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Subject to completion, dated February 10, 2014

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to the notes has become effective under the Securities Act of 1933, as amended. This preliminary prospectus supplement and the accompanying prospectus is not an offer to sell the notes and it is not soliciting an offer to buy the notes in any jurisdiction where the offer or sale is not permitted.

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-192132

Prospectus supplement
(To prospectus dated November 18, 2013)

AMAG PHARMACEUTICALS, INC.

$150,000,000
         % Convertible Senior Notes due 2019
Interest payable February 15 and August 15

We are offering $150,000,000 principal amount of our         % Convertible Senior Notes due 2019. The notes will bear interest at a rate of         % per year, payable semiannually in arrears on February 15 and August 15 of each year, beginning on August 15, 2014. The notes will mature on February 15, 2019.

Holders may convert their notes at their option at any time prior to the close of business on the business day immediately preceding May 15, 2018 only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on March 31, 2014 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the "measurement period") in which the trading price (as defined below) per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events. On or after May 15, 2018 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their notes at any time, regardless of the foregoing circumstances. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, as described in this prospectus supplement.

The conversion rate will initially be                           shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $             per share of common stock). The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, we will increase the conversion rate for a holder who elects to convert its notes in connection with such a corporate event in certain circumstances.

We may not redeem the notes prior to the maturity date, and no sinking fund is provided for the notes.

If we undergo a fundamental change, holders may require us to repurchase for cash all or any portion of their notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

The notes will be our senior unsecured obligations and will rank senior in right of payment to any of our indebtedness that is expressly subordinated in right of payment to the notes; equal in right of payment to any of our unsecured indebtedness that is not so subordinated; effectively junior in right of payment to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) and preferred stock of our subsidiaries.

We do not intend to apply to list the notes on any securities exchange or any automated dealer quotation system. Our common stock is listed on The NASDAQ Global Select Market under the symbol "AMAG." The last reported sale price of our common stock on The NASDAQ Global Select Market on February 7, 2014 was $21.16 per share.

Investing in the notes involves a high degree of risk. See "Risk factors" beginning on page S-11 of this prospectus supplement.

We have granted the underwriters the right to purchase, exercisable within a 30-day period, up to an additional $22,500,000 principal amount of notes, solely to cover over-allotments.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the notes or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We expect that delivery of the notes will be made to investors in book-entry form through The Depository Trust Company on or about February     , 2014.

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Prospectus Supplement

Prospectus

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About this prospectus supplement

We are providing information to you about this offering in two parts. The first part is this prospectus supplement, which describes the specific terms of the offering. The second part, the accompanying prospectus, gives more general information. You should read this prospectus supplement and the accompanying prospectus, including the information incorporated by reference herein and therein and any free writing prospectus we have authorized for use in connection with this offering, in their entirety before making an investment decision.

We have not and the underwriters have not authorized anyone to provide you with any information other than information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus or any free writing prospectus prepared by or on behalf of us or to which we have referred you. If the description of the offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information in this prospectus supplement. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

If the description of the offering varies between any free writing prospectus we have authorized for use in connection with this offering and this prospectus supplement, you rely on the information in such free writing prospectus.

You should assume that the information in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein and in any free writing prospectus we have authorized for use in connection with this offering is accurate only as of the respective dates of those documents in which such information is contained, regardless of the time of delivery of this prospectus supplement or any sale of the notes. Our business, financial condition, results of operations and prospects may have changed since those dates.

Any statement made in this prospectus supplement or in a document incorporated by reference in this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or in any other subsequently filed document that is also incorporated or deemed to be incorporated by reference in this prospectus supplement modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement. See "Incorporation of documents by reference" in this prospectus supplement.

We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted.

References in this prospectus supplement and the accompanying prospectus to "AMAG," "the Company," "we," "our" and "us" refer to AMAG Pharmaceuticals, Inc. and its consolidated subsidiaries, except where the context otherwise requires or as otherwise indicated.

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Trade names, trademarks and service marks

Feraheme®, Rienso®, MuGard®, our logo and other trade names, trademarks or service marks of AMAG appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein and any free writing prospectus we authorize for use in connection with this offering are the property of AMAG. Trade names, trademarks and service marks of other organizations are the property of their respective holders.

Cautionary note regarding forward-looking statements

Any statements in this prospectus supplement, the accompany prospectus, the documents incorporated by reference herein and therein and any free writing prospectus we authorize for use in connection with this offering about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or the "Securities Act," and Section 21E of the Securities Exchange Act of 1934, as amended, or the "Exchange Act." You can identify these forward-looking statements by the use of words or phrases such as "believe," "may," "could," "will," "estimate," "continue," "anticipate," "intend," "seek," "plan," "expect," "potential," "predict," "project," "should" or "would." Examples of forward-looking statements contained in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein include statements regarding the following:

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our plan to grow Feraheme in the U.S. chronic kidney disease market and through international expansion, IV iron market expansion and label expansion;

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the expansion of our portfolio through the in-license or purchase of additional specialty pharmaceutical products and companies;

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expectations regarding our supplemental New Drug Application for Feraheme and our plans for addressing the complete response letter from the FDA and the path forward for Feraheme in the broad IDA population;

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the timing of the opinion of the European Medicines Agency and the related decision by the European Commission regarding Takeda Pharmaceutical Company Limited's application for Type II variation of the marketing authorization for Rienso in the EU;

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our expectations regarding the timing for enrollment in and commencement of our pediatric studies and a post-approval trial to assess the safety and efficacy of repeat doses of Feraheme for the treatment of iron deficiency anemia;

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our expectation of costs to be incurred in connection with and revenue sources to fund our future operations;

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our expectation for the patient population for Feraheme in the United States;

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our expectations regarding the success of our collaboration with Takeda Pharmaceutical Company Limited, including any potential milestone payments, product sales or royalties we may receive;

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our expectations regarding the manufacture of all Feraheme/Rienso drug substance and drug product at our third-party manufacturers;

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our expectations regarding customer returns and other revenue-related reserves and accruals;

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variations of the labeling and other elements of the marketing authorization for Rienso in the European Union that may be expected as a result of the review by the EMA Committee for Medicinal Products for Human Use of IV iron-containing medications used to treat iron deficiency anemia;

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our expectations regarding the validity of our European ferumoxytol patent and timing of the appeals process;

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our expectations regarding government regulations, including the Branded Drug Fee under the Health Care Reform Act and the Medicare reimbursement rate for Feraheme and estimates for Medicaid rebates;

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our expectations regarding our license fee and other collaboration revenues;

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expected customer mix and utilization rates;

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the impact of volume rebates and other incentives;

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provider purchase patterns and use of competitive products;

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expectations regarding MuGard and our license arrangement with Access Pharmaceuticals, Inc.;

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the valuation of certain intangible assets, contingent consideration and other assets and liabilities, including our methodology and assumptions regarding fair value measurements;

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our gross-to-net sales adjustments;

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our expectations that increasing competitive pressures in 2014 may lead to slowing growth in our products sales;

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our Citizen's Petition;

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our expectation for product sales and net revenue per gram of Feraheme and our costs of product sales as a percentage of net product sales and royalties, our research and development expenses, external expenses and the timing of our planned research and development projects, and selling, general and administrative expenses;

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our belief regarding the potential impact of the adoption of newly issued and future accounting guidance on our financial statements; and

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our expectations for our cash, cash equivalents and investments balances and information with respect to any other plans and strategies for our business, including without limitation, the use of proceeds from this offering.

Our actual results and the timing of certain events may differ materially from the results discussed, projected, anticipated or indicated in any forward-looking statements. Any forward-looking statement should be considered in light of the factors discussed under the heading "Item 1A. Risk Factors" in our most recent Annual Report on 10-K, as well as any

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amendments thereto reflected in subsequent filings with the Securities and Exchange Commission, or SEC, and under the heading "Risk Factors" in this prospectus supplement and the accompanying prospectus.

We qualify all of the forward-looking statements about our expectations, beliefs, plans, objectives, assumptions or future events or performance in this prospectus supplement, the accompany prospectus, the documents incorporated by reference herein and therein and any free writing prospectus we authorize for use in connection with this offering by these cautionary statements.

We cannot guarantee future results, events, levels of activity, performance or achievement. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, unless required by law.

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Risk factors

Investing in the notes and our common stock involves a high degree of risk. You should carefully consider the risks described below and all of the information contained and incorporated by reference in this prospectus supplement, the accompanying prospectus and any free writing prospectus we have authorized for use in connection with this offering before deciding whether to purchase the notes. You should carefully consider, among other things, the matters discussed under "Item 1A. Risk Factors" in our most recent Annual Report on Form 10-K, as well as any amendments thereto reflected in subsequent filings with the SEC. See "Incorporation of documents by reference." The risks and uncertainties described below are not the only ones we face. Additional risks and uncertainties not presently known to us or that our management currently deems immaterial also may impair our business operations. If any of the risks described below were to occur, our business, financial condition, operating results and cash flows could be materially adversely affected. In such an event, the trading price of the notes and our common stock could decline and you could lose all or part of your investment. The risks discussed below also include forward-looking statements and our actual results may differ substantially from those discussed in these forward-looking statements. See "Cautionary note regarding forward-looking statements."

Risks related to the notes

The notes are effectively subordinated to our secured debt and any liabilities of our subsidiaries.

The notes will rank senior in right of payment to any of our indebtedness that is expressly subordinated in right of payment to the notes; equal in right of payment to any of our liabilities that are not so subordinated; effectively junior in right of payment to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) and preferred stock of our subsidiaries. In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure debt ranking senior in right of payment to the notes will be available to pay obligations on the notes only after the secured debt has been repaid in full from these assets. There may not be sufficient assets remaining to pay amounts due on any or all of the notes then outstanding. The indenture governing the notes will not prohibit us from incurring additional senior debt or secured debt, nor will it prohibit any of our subsidiaries from incurring liabilities or issuing preferred stock.

As of December 31, 2013, we had no consolidated indebtedness and our subsidiaries had no liabilities (including trade payables, but excluding intercompany obligations and liabilities of a type not required to be reflected on a balance sheet of such subsidiaries in accordance with GAAP).

The notes are our obligations only.

The notes are our obligations exclusively and are not guaranteed by any of our subsidiaries. Our ability to service our debt, including the notes, may depend on the results of operations of our subsidiaries and upon the ability of such subsidiaries to provide us with cash, whether in the form of dividends, loans or otherwise, to pay amounts due on our obligations, including the notes. Our subsidiaries are separate and distinct legal entities and have no obligation, contingent or otherwise, to make payments on the notes or to make any funds available for

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that purpose. In addition, dividends, loans or other distributions to us from such subsidiaries may be subject to contractual and other restrictions and are subject to other business considerations, including that such distributions may be subject to U.S. and foreign tax liabilities.

Servicing our debt requires a significant amount of cash, and we may not have sufficient cash flow from our business to make payments on our debt.

Our ability to make scheduled payments of the principal of, to pay interest on or to refinance our indebtedness, including the notes, depends on our future performance, which is subject to economic, financial, competitive and other factors that may be beyond our control. Our business may not generate cash flow from operations in the future sufficient to service our debt and make necessary capital expenditures. If we are unable to generate such cash flow, we may be required to adopt one or more alternatives, such as selling assets, restructuring debt or obtaining additional equity capital on terms that may be onerous or highly dilutive. Our ability to refinance our indebtedness will depend on the capital markets and our financial condition at such time. We may not be able to engage in any of these activities or engage in these activities on desirable terms, which could result in a default on our debt obligations, including the notes.

Recent and future regulatory actions and other events may adversely affect the trading price and liquidity of the notes.

We expect that many investors in, and potential purchasers of, the notes will employ, or seek to employ, a convertible arbitrage strategy with respect to the notes. Investors would typically implement such a strategy by selling short the common stock underlying the notes and dynamically adjusting their short position while continuing to hold the notes. Investors may also implement this type of strategy by entering into swaps on our common stock in lieu of or in addition to short selling the common stock.

The SEC and other regulatory and self-regulatory authorities have implemented various rules and taken certain actions, and may in the future adopt additional rules and take other actions, that may impact those engaging in short selling activity involving equity securities (including our common stock). Such rules and actions include Rule 201 of SEC Regulation SHO, the adoption by the Financial Industry Regulatory Authority, Inc. and the national securities exchanges of a "Limit Up-Limit Down" program, the imposition of market-wide circuit breakers that halt trading of securities for certain periods following specific market declines, and the implementation of certain regulatory reforms required by the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010. Any governmental or regulatory action that restricts the ability of investors in, or potential purchasers of, the notes to effect short sales of our common stock, borrow our common stock or enter into swaps on our common stock could adversely affect the trading price and the liquidity of the notes.

Volatility in the market price and trading volume of our common stock could adversely impact the trading price of the notes.

The market price of our common stock has been, and may continue to be, volatile. Our stock price has ranged between $15.90 and $28.42 in the fifty-two week period through January 31, 2014. The stock market has from time to time experienced extreme price and volume fluctuations, particularly in the biotechnology and pharmaceuticals sectors, which have often

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been unrelated to the operating performance of particular companies. Various factors and events, many of which are beyond our control, may have a significant impact on the market price of our common stock. The market price of our common stock could fluctuate significantly for many reasons, including in response to the risks described in this section, elsewhere in this prospectus supplement, the accompanying prospectus or the documents we have incorporated by reference in this prospectus supplement or for reasons unrelated to our operations, such as reports by industry analysts, investor perceptions or negative announcements by our customers, competitors or suppliers regarding their own performance, as well as industry conditions and general financial, economic and political instability. A decrease in the market price of our common stock would likely adversely impact the trading price of the notes. The market price of our common stock could also be affected by possible sales of our common stock by investors who view the notes as a more attractive means of equity participation in us and by hedging or arbitrage trading activity that we expect to develop involving our common stock. This trading activity could, in turn, affect the trading price of the notes.

We may incur substantially more debt or take other actions which would intensify the risks discussed above.

We and our subsidiaries may be able to incur substantial additional debt in the future, some of which may be secured debt and/or structurally senior debt. We and our subsidiaries will not be restricted under the terms of the indenture governing the notes from incurring additional debt, securing debt, recapitalizing our debt or taking several other actions that are not limited by the terms of the indenture governing the notes that could have the effect of diminishing our ability to make payments on the notes when due.

We may not have the ability to raise the funds necessary to settle conversions of the notes or to repurchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to pay cash upon conversion or repurchase of the notes.

Holders of the notes will have the right to require us to repurchase their notes upon the occurrence of a fundamental change at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest, if any, as described under "Description of notes—Fundamental change permits holders to require us to repurchase notes." In addition, upon conversion of the notes, unless we elect to deliver solely shares of our common stock to settle such conversion (other than paying cash in lieu of delivering any fractional share), we will be required to make cash payments in respect of the notes being converted as described in under "Description of notes—Conversion rights—Settlement upon conversion." However, we may not have enough available cash or be able to obtain financing at the time we are required to make repurchases of notes surrendered therefor or notes being converted. In addition, our ability to repurchase the notes or to pay cash upon conversions of the notes may be limited by law, by regulatory authority or by agreements governing our future indebtedness. Our failure to repurchase notes at a time when the repurchase is required by the indenture or to pay any cash payable on future conversions of the notes as required by the indenture would constitute a default under the indenture. A default under the indenture or the fundamental change itself could also lead to a default under agreements governing our future indebtedness. If the repayment of the related indebtedness were to be accelerated after any applicable notice or grace periods, we may not have sufficient funds to repay the indebtedness and repurchase the notes or make cash payments upon conversions thereof.

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The conditional conversion feature of the notes, if triggered, may adversely affect our financial condition and operating results.

In the event the conditional conversion feature of the notes is triggered, holders of notes will be entitled to convert the notes at any time during specified periods at their option. At all times on or after May 15, 2018 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders of the notes will be entitled to convert the notes. See "Description of notes—Conversion rights." If one or more holders elect to convert their notes, unless we elect to satisfy our conversion obligation by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share), we would be required to settle a portion or all of our conversion obligation through the payment of cash, which could adversely affect our liquidity. In addition, even if holders do not elect to convert their notes, we could be required under applicable accounting rules to reclassify all or a portion of the outstanding principal of the notes as a current rather than long-term liability, which would result in a material reduction of our net working capital.

The accounting method for convertible debt securities that may be settled in cash, such as the notes, is the subject of recent changes that could have a material effect on our reported financial results.

In May 2008, the Financial Accounting Standards Board, to which we refer as FASB, issued FASB Staff Position No. APB 14-1, Accounting for Convertible Debt Instruments That May Be Settled in Cash Upon Conversion (Including Partial Cash Settlement), which has subsequently been codified as Accounting Standards Codification 470-20, Debt with Conversion and Other Options, to which we refer as ASC 470-20. Under ASC 470-20, an entity must separately account for the liability and equity components of convertible debt instruments (such as the notes) that may be settled entirely or partially in cash upon conversion in a manner that reflects the issuer's economic interest cost. The effect of ASC 470-20 on the accounting for the notes is that the equity component is required to be included in the additional paid-in capital section of stockholders' equity on our consolidated balance sheet, and the value of the equity component would be treated as original issue discount for purposes of accounting for the debt component of the notes. As a result, we will be required to record a greater amount of non-cash interest expense in current periods presented as a result of the amortization of the discounted carrying value of the notes to their face amount over the term of the notes. We will report lower net income in our financial results because ASC 470-20 will require interest to include both the current period's amortization of the debt discount and the instrument's coupon interest, which could adversely affect our reported or future financial results, the trading price of our common stock or the trading price of the notes.

In addition, under certain circumstances, convertible debt instruments (such as the notes) that may be settled entirely or partly in cash are currently accounted for utilizing the treasury stock method, the effect of which is that the shares issuable upon conversion of the notes are not included in the calculation of diluted earnings per share except to the extent that the conversion value of the notes exceeds their principal amount. Under the treasury stock method, for diluted earnings per share purposes, the transaction is accounted for as if the shares of common stock that would be necessary to settle such excess, if we elected to settle such excess in shares, are issued. We cannot be sure that the accounting standards in the future will continue to permit the use of the treasury stock method. If we are unable to use the treasury

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stock method in accounting for the shares issuable upon conversion of the notes, then our diluted earnings per share will be adversely affected.

Future sales of our common stock or equity-linked securities could lower the market price for our common stock and adversely impact the trading price of the notes.

In the future, we may sell additional shares of our common stock or equity-linked securities to raise capital or in connection with strategic transactions or partnerships. In addition, a substantial number of shares of our common stock is reserved for issuance upon the exercise of stock options, the vesting of restricted stock units and upon conversion of the notes. We cannot predict the size of future issuances or the effect, if any, that they may have on the market price for our common stock. The issuance and sale of substantial amounts of common stock or equity-linked securities, or the perception that such issuances and sales may occur, could adversely affect the trading price of the notes and the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities.

You will not be entitled to any rights with respect to our common stock, but you will be subject to all changes made with respect to them to the extent we satisfy our conversion obligation with shares of our common stock.

Holders of notes will not be entitled to any rights with respect to our common stock (including, without limitation, voting rights, rights to receive any dividends or other distributions on our common stock or rights pursuant to our shareholder rights plan) prior to the conversion date relating to such notes (if we have elected to settle the relevant conversion by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share)) or the last trading day of the relevant observation period (if we elect to pay and deliver, as the case may be, a combination of cash and shares of our common stock in respect of the relevant conversion), but holders of notes will be subject to all changes affecting our common stock. For example, if an amendment is proposed to our certificate of incorporation or bylaws requiring stockholder approval and the record date for determining the stockholders of record entitled to vote on the amendment occurs prior to the conversion date related to a holder's conversion of its notes (if we have elected to settle the relevant conversion by delivering solely shares of our common stock (other than paying cash in lieu of delivering any fractional share)) or the last trading day of the relevant observation period (if we elect to pay and deliver, as the case may be, a combination of cash and shares of our common stock in respect of the relevant conversion), such holder will not be entitled to vote on the amendment, although such holder will nevertheless be subject to the amendment, if adopted.

The conditional conversion feature of the notes could result in your receiving less than the value of our common stock into which the notes would otherwise be convertible.

Prior to the close of business on the business day immediately preceding May 15, 2018, you may convert your notes only if specified conditions are met. If the specific conditions for conversion are not met, you will not be able to convert your notes, and you may not be able to receive (through sale or otherwise) the value of the cash, common stock or a combination of cash and common stock, as applicable, into which the notes would otherwise be convertible.

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Upon conversion of the notes, you may receive less valuable consideration than expected because the value of our common stock may decline after you exercise your conversion right but before we settle our conversion obligation.

Under the notes, a converting holder will be exposed to fluctuations in the value of our common stock during the period from the date such holder surrenders notes for conversion until the date we settle our conversion obligation.

Upon conversion of the notes, we have the option to pay or deliver, as the case may be, cash, shares of our common stock, or a combination of cash and shares of our common stock. If we elect to satisfy our conversion obligation in cash or a combination of cash and shares of our common stock, the amount of consideration that you will receive upon conversion of your notes will be determined by reference to the volume-weighted average price of our common stock for each trading day in an 80 trading day observation period. As described under "Description of notes—Settlement upon conversion," this period would be (i) if the relevant conversion date occurs prior to May 15, 2018, the 80 consecutive trading day period beginning on, and including, the third trading day immediately succeeding such conversion date; and (ii) if the relevant conversion date occurs on or after May 15, 2018, the 80 consecutive trading days beginning on, and including, the 82nd scheduled trading day immediately preceding the maturity date. Accordingly, if the price of our common stock decreases during this period, the amount and/or value of consideration you receive will be adversely affected. In addition, if the market price of our common stock at the end of such period is below the average volume-weighted average price of our common stock during such period, the value of any shares of our common stock that you will receive in satisfaction of our conversion obligation will be less than the value used to determine the number of shares that you will receive.

If we elect to satisfy our conversion obligation solely in shares of our common stock upon conversion of the notes, we will be required to deliver the shares of our common stock, together with cash for any fractional share, on the third business day following the relevant conversion date. Accordingly, if the price of our common stock decreases during this period, the value of the shares that you receive will be adversely affected and would be less than the conversion value of the notes on the conversion date.

The notes are not protected by restrictive covenants.

The indenture governing the notes will not contain any financial or operating covenants or restrictions on the payments of dividends, the incurrence of indebtedness or the issuance or repurchase of securities by us or any of our subsidiaries. The indenture will contain no covenants or other provisions to afford protection to holders of the notes in the event of a fundamental change or other corporate transaction involving us except to the extent described under "Description of notes—Fundamental change permits holders to require us to repurchase notes," "Description of notes—Conversion rights—Increase in conversion rate upon conversion upon a make-whole fundamental change" and "Description of notes—Consolidation, merger and sale of assets."

The increase in the conversion rate for notes converted in connection with a make-whole fundamental change may not adequately compensate you for any lost value of your notes as a result of such transaction.

If a make-whole fundamental change occurs prior to the maturity date, under certain circumstances, we will increase the conversion rate for notes converted in connection with such

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make-whole fundamental change. The increase in the conversion rate will be determined based on the date on which the specified corporate transaction becomes effective and the price paid (or deemed to be paid) per share of our common stock in such transaction, as described below under "Description of notes—Conversion rights—Increase in conversion rate upon conversion upon a make-whole fundamental change." The increase in the conversion rate for notes converted in connection with a make-whole fundamental change may not adequately compensate you for any lost value of your notes as a result of such transaction. In addition, if the price per share of our common stock paid (or deemed paid) in the transaction is greater than $             per share or less than $             per share (in each case, subject to adjustment), the conversion rate will not be increased. Moreover, in no event will the conversion rate per $1,000 principal amount of notes as a result of this adjustment exceed             , subject to adjustment in the same manner as the conversion rate as set forth under "Description of notes—Conversion rights—Conversion rate adjustments."

Our obligation to increase the conversion rate for notes converted in connection with a make-whole fundamental change could be considered a penalty, in which case the enforceability thereof would be subject to general principles of reasonableness and equitable remedies.

The conversion rate of the notes may not be adjusted for all dilutive events.

The conversion rate of the notes is subject to adjustment for certain events, including, but not limited to, the issuance of certain stock dividends on our common stock, the issuance of certain rights or warrants, subdivisions, combinations, distributions of capital stock, indebtedness, or assets, cash dividends and certain issuer tender or exchange offers as described under "Description of notes—Conversion rights—Conversion rate adjustments." However, the conversion rate will not be adjusted for other events, such as a third-party tender or exchange offer or an issuance of common stock for cash, that may adversely affect the trading price of the notes or our common stock. An event that adversely affects the value of the notes may occur, and that event may not result in an adjustment to the conversion rate.

Some significant restructuring transactions may not constitute a fundamental change, in which case we would not be obligated to offer to repurchase the notes.

Upon the occurrence of a fundamental change, you have the right to require us to repurchase your notes. However, the fundamental change provisions will not afford protection to holders of notes in the event of other transactions that could adversely affect the notes. For example, transactions such as leveraged recapitalizations, refinancings, restructurings or acquisitions initiated by us may not constitute a fundamental change requiring us to repurchase the notes. In the event of any such transaction, the holders would not have the right to require us to repurchase the notes, even though each of these transactions could increase the amount of our indebtedness, or otherwise adversely affect our capital structure or any credit ratings, thereby adversely affecting the holders of notes.

We cannot assure you that an active trading market will develop for the notes.

Prior to this offering, there has been no trading market for the notes, and we do not intend to apply to list the notes on any securities exchange or to arrange for quotation on any automated dealer quotation system. We have been informed by the underwriters that they intend to make a market in the notes after the offering is completed. However, the

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underwriters may cease their market-making at any time without notice. In addition, the liquidity of the trading market in the notes, and the market price quoted for the notes, may be adversely affected by changes in the overall market for this type of security and by changes in our financial performance or prospects or in the prospects for companies in our industry generally. As a result, we cannot assure you that an active trading market will develop for the notes. If an active trading market does not develop or is not maintained, the market price and liquidity of the notes may be adversely affected. In that case you may not be able to sell your notes at a particular time or you may not be able to sell your notes at a favorable price.

Any adverse rating of the notes may cause their trading price to fall.

We do not intend to seek a rating on the notes. If a rating service were to rate the notes, however, and if such rating service were to lower its rating on the notes below the rating initially assigned to the notes or otherwise announces its intention to put the notes on credit watch, the trading price of the notes could decline.

You may be subject to tax if we make or fail to make certain adjustments to the conversion rate of the notes even though you do not receive a corresponding cash distribution.

The conversion rate of the notes is subject to adjustment in certain circumstances, including the payment of cash dividends. If the conversion rate is adjusted as a result of a distribution that is taxable to our common stockholders, such as a cash dividend, you may be deemed to have received a dividend subject to U.S. federal income tax without the receipt of any cash. In addition, a failure to adjust (or to adjust adequately) the conversion rate after an event that increases your proportionate interest in us could be treated as a deemed taxable dividend to you. If a make-whole fundamental change occurs prior to the maturity date, under some circumstances, we will increase the conversion rate for notes converted in connection with the make-whole fundamental change. Such increase may also be treated as a distribution subject to U.S. federal income tax as a dividend. See "Material U.S. federal income tax considerations." If you are a non-U.S. holder (as defined in "Material U.S. federal income tax considerations"), any deemed dividend would be subject to U.S. federal withholding tax at a 30% rate, or such lower rate as may be specified by an applicable treaty, which may be set off against subsequent payments on the notes. See "Material U.S. federal income tax considerations."

The convertible note hedge and warrant transactions may affect the value of the notes and our common stock.

In connection with the pricing of the notes, we expect to enter into convertible note hedge transactions with the option counterparties. The convertible note hedge transactions are expected to reduce the potential dilution and/or offset cash payments due upon conversion of the notes. We also expect to enter into warrant transactions with the option counterparties. However, the warrant transactions could separately have a dilutive effect on our earnings per share to the extent that the market price per share of our common stock exceeds the applicable strike price of the warrants. If the underwriters exercise their over-allotment option, we may sell additional warrants and use a portion of the net proceeds from the sale of the additional notes, together with the proceeds from the sale of the additional warrants, to enter into additional convertible note hedge transactions.

The option counterparties have advised us that, in connection with establishing their initial hedge of the convertible note hedge and warrant transactions, they or their affiliates expect to

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enter into various derivative transactions with respect to our common stock concurrently with or shortly after the pricing of the notes. This activity could increase (or reduce the size of any decrease in) the market price of our common stock or the notes at that time.

In addition, the option counterparties or their affiliates may modify their hedge position by entering into or unwinding various derivatives with respect to our common stock and/or purchasing or selling our common stock or other securities of ours in secondary market transactions following the pricing of the notes and prior to the maturity of the notes (and are likely to do so during any observation period related to a conversion of notes). This activity could also cause or avoid an increase or a decrease in the market price of our common stock or the notes, which could affect your ability to convert the notes and, to the extent the activity occurs during any observation period related to a conversion of notes, it could affect the number of shares and value of the consideration that you will receive upon conversion of the notes.

In addition, if any such convertible note hedge and warrant transactions fail to become effective, whether or not this offering of notes is completed, the option counterparties or their affiliates may unwind their hedge positions with respect to our common stock, which could adversely affect the value of our common stock and, if the notes have been issued, the value of the notes.

Risks related to our common stock

The price of our common stock historically has been volatile. This volatility may affect the price at which you could sell the common stock you receive upon conversion of your notes, if any, and the sale of substantial amounts of our common stock could adversely affect the price of our common stock.

The market price of our common stock has been, and may continue to be, volatile. This volatility may affect the price at which you could sell the common stock, if any, you receive upon conversion of your notes, and the sale of substantial amounts of our common stock could adversely affect the price of our common stock and the value of your notes. The market price of our common stock could fluctuate significantly for many reasons, including in response to the risks described in this section, elsewhere in this prospectus supplement, the accompanying prospectus or the documents we have incorporated by reference in this prospectus supplement or for reasons unrelated to our operations, such as reports by industry analysts, investor perceptions or negative announcements by our customers, competitors or suppliers regarding their own performance, as well as industry conditions and general financial, economic and political instability.

In addition, the sale of substantial amounts of our common stock could adversely impact its price. As of December 31, 2013, we had outstanding 21,772,571 shares of our common stock, options to purchase approximately 2,819,676 shares of our common stock (of which approximately 1,003,804 were exercisable as of that date), approximately 465,394 shares of our common stock issuable upon the vesting of restricted stock units and approximately 2,024,621 shares of our common stock available for future grants under our equity compensation plans. The sale or the availability for sale of a large number of shares of our common stock or equity-linked securities could cause the price of our common stock and the value of your notes to decline.

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Our shareholder rights plan, certain provisions in our charter and by-laws, certain contractual relationships and certain Delaware law provisions could discourage an acquisition of us by others, even if an acquisition would be beneficial to our stockholders, and may prevent attempts by our stockholders to replace or remove our current members of our board of directors.

In 2009, we adopted a shareholder rights plan, the provisions of which are intended to deter a hostile takeover by making any proposed hostile acquisition of us more expensive and less desirable to a potential acquirer by enabling our stockholders (other than the potential hostile acquirer) to purchase significant amounts of additional shares of our common stock at dilutive prices. The rights issued pursuant to our shareholder rights plan become exercisable generally upon the earlier of 10 days after a person or group acquires 20% or more of our outstanding common stock or 10 business days after the announcement by a person or group of an intention to acquire 20% of our outstanding common stock via tender offer or similar transaction. The shareholder rights plan could delay or discourage transactions involving an actual or potential change in control of us or our management, including transactions in which stockholders might otherwise receive a premium for their shares over then-current prices. We amended our shareholder rights plan to allow for this note offering, the convertible note hedge and warrant transactions and related derivative transactions without triggering the exercisability of the rights issued under our shareholder rights plan.

In addition, certain provisions in our certificate of incorporation and our by-laws may discourage, delay or prevent a change of control or takeover attempt of our company by a third-party as well as substantially impede the ability of our stockholders to benefit from a change of control or effect a change in management and our board of directors. These provisions include:

•

The ability of our board of directors to increase or decrease the size of the board of directors without stockholder approval;

•

Advance notice requirements for the nomination of candidates for election to our board of directors and for proposals to be brought before our annual meeting of stockholders;

•

The authority of our board of directors to designate the terms of and issue new series of preferred stock without stockholder approval;

•

Non-cumulative voting for directors; and

•

Limitations on the ability of our stockholders to call special meetings of stockholders.

As a Delaware corporation, we are subject to the provisions of Section 203 of the Delaware General Corporation Law, or Section 203, which prevents us from engaging in any business combination with any "interested stockholder," which is defined generally as a person that acquires 15% or more of a corporation's outstanding voting stock, for a period of three years after the date of the transaction in which the person became an interested stockholder, unless the business combination is approved in the manner prescribed in Section 203. These provisions could have the effect of delaying or preventing a change of control, whether or not it is desired by, or beneficial to, our stockholders.

In addition to the above factors, an acquisition of our company could be made more difficult by employment agreements we have in place with our executive officers, as well as a

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company-wide change of control policy, which provide for severance benefits as well as the full acceleration of vesting of any outstanding options or restricted stock units in the event of a change of control and subsequent termination of employment. Further, our Third Amended and Restated 2007 Equity Incentive Plan generally permits our board of directors to provide for the acceleration of vesting of options granted under that plan in the event of certain transactions that result in a change of control.

The repurchase right under the notes in connection with a fundamental change and any increase in the conversion rate in connection with a make-whole fundamental change could also discourage a potential acquirer.

We do not intend to pay dividends in the foreseeable future, and we may be unable to pay dividends.

We have never declared or paid any cash dividends on our common stock. For the foreseeable future, we intend to retain any earnings to finance the development and expansion of our business, and we do not anticipate paying any cash dividends on our common stock. Any future determination to pay dividends will be at the discretion of our board of directors and will be dependent on then-existing conditions, including our financial condition and results of operations, capital requirements, contractual restrictions, business prospects and other factors that our board of directors considers relevant. In addition, our ability to pay dividends is constrained by our holding company structure, under which we are dependent on our subsidiaries for payments. For the foregoing reasons, you will not be able to rely on dividends to receive a return on your investment, and the success of an investment in shares of our common stock will depend upon any future appreciation in its value.

If equity research analysts cease to publish research or reports about our business or if they issue unfavorable commentary or downgrade our common stock, the price of our common stock and the value of your notes could decline.

The trading market for our common stock will rely in part on the research and reports that equity research analysts publish about us and our business. We do not control these analysts. The price of our stock and the value of your notes could decline if one or more equity analysts downgrade our stock or if those analysts issue other unfavorable commentary or cease publishing reports about us or our business.

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Use of proceeds

We estimate that the proceeds from this offering will be approximately $          million (or $          million if the underwriters exercise their option to purchase additional notes, solely to cover over-allotments, in full), after deducting fees and estimated expenses. In connection with the pricing of this offering, we expect to enter into convertible note hedge transactions with one or more financial institutions, which we refer to as the option counterparties. We also intend to enter into warrant transactions with the option counterparties. We intend to use approximately $          million of the net proceeds from this offering to pay the net cost of the convertible note hedge transactions (after such cost is partially offset by the proceeds to us from the warrant transactions). We intend to use the remainder of the net proceeds from this offering for working capital and other general corporate purposes, including to fund possible acquisitions of, or investments in, complementary businesses, products, services and technologies. We have not entered into any agreements or commitments with respect to any acquisitions or investments at this time. If the underwriters exercise their over-allotment option, we may sell additional warrants and use a portion of the net proceeds from the sale of the additional notes, together with the proceeds from the sale of the additional warrants, to enter into additional convertible note hedge transactions.

Pending these uses, we intend to invest the net proceeds in high quality, investment grade, short-term fixed income instruments which include corporate, financial institution, federal agency or U.S. government obligations. We will retain broad discretion over the use of these proceeds.

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Ratio of earnings to fixed charges

The following table presents our ratio of earnings to fixed charges for the years ended December 31, 2013, 2012, 2011, 2010 and 2009.

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Dividend policy

We have never declared or paid a cash dividend on our common stock. We currently anticipate that we will retain all of our earnings for use in the development of our business and do not anticipate paying any cash dividends in the foreseeable future. Payment of future dividends, if any, will be at the discretion of our board of directors and will depend on our financial condition, results of operations, capital requirements, restrictions contained in current or future financing instruments and other factors our board of directors deems relevant.

Price range of common stock

Our common stock trades on the NASDAQ Global Select Market, or NASDAQ, under the trading symbol "AMAG." The following table shows the high and low sale prices per share of our common stock as reported on NASDAQ for the periods indicated:

The last reported sale price of our common stock on NASDAQ on February 7, 2014 was $21.16 per share. As of February 3, 2014, we had approximately 90 holders of record of our common stock.

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Capitalization

The following table sets forth our cash, cash equivalents and investments and our capitalization as of December 31, 2013:

•

on an actual basis; and

•

on an as adjusted basis to reflect the sale of the notes (assuming the underwriters' option to purchase additional notes, solely to cover over-allotments, is not exercised), and the receipt of the net proceeds therefrom as described in "Use of proceeds" assuming such net proceeds that are not used in connection with the convertible note hedge transactions are held as cash or cash equivalents.

You should read this table in conjunction with "Use of proceeds" appearing elsewhere in this prospectus supplement, as well as "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our audited consolidated financial statements and the related notes thereto, incorporated by reference into this prospectus supplement from our Annual Report on Form 10-K for the year ended December 31, 2013.

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The number of shares of our common stock in the table above excludes:

•

an aggregate of 2,819,676 shares of our common stock issuable upon exercise of outstanding stock options issued under our equity compensation plans;

•

an aggregate of 465,394 shares of our common stock reserved for issuance in connection with restricted stock units issued under our equity compensation plans;

•

an additional 2,024,621 shares of our common stock available for future grants under our equity compensation plans; and

•

shares of common stock initially issuable in connection with conversion of the notes offered hereby or the warrant transactions.

All applicable share, per share and related information in this prospectus supplement speaks as of December 31, 2013, unless otherwise indicated.

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Description of notes

We will issue the notes under a base indenture between us and Wilmington Trust, National Association, as supplemented by a supplemental indenture with respect to the notes, each of which will be dated the date of the initial issuance of the notes. In this section, we refer to the base indenture (the "base indenture"), as supplemented by the supplemental indenture (the "supplemental indenture"), collectively as the "indenture." This description of the notes supplements and, to the extent it is inconsistent, replaces the description of the general provisions of the notes and the base indenture in the accompanying prospectus. The terms of the notes include those expressly set forth in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as amended (the "Trust Indenture Act").

You may request a copy of the indenture from us as described under "Where you can find more information."

The following description is a summary of the material provisions of the notes and the indenture and does not purport to be complete. This summary is subject to and is qualified by reference to all of the provisions of the notes and the indenture, including the definitions of certain terms used in the indenture. We urge you to read these documents because they, and not this description, define your rights as a holder of the notes.

For purposes of this description, references to "we," "our" and "us" refer only to AMAG Pharmaceuticals, Inc. and not to any of its subsidiaries.

General

The notes will:

•

be our general unsecured, senior obligations;

•

initially be limited to an aggregate principal amount of $150,000,000 (or $172,500,000 if the underwriters' over-allotment option is exercised in full);

•

bear cash interest from February     , 2014 at an annual rate of         % payable on February 15 and August 15 of each year, beginning on August 15, 2014;

•

not be redeemable prior to their maturity date;

•

be subject to repurchase by us at the option of the holders following a fundamental change (as defined below under "—Fundamental change permits holders to require us to repurchase notes"), at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the relevant fundamental change repurchase date;

•

mature on February 15, 2019, unless earlier converted or repurchased;

•

be issued in denominations of $1,000 and integral multiples of $1,000; and

•

be represented by one or more registered notes in global form, but in certain limited circumstances may be represented by notes in definitive form. See "Book-entry, settlement and clearance."

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Subject to satisfaction of certain conditions and during the periods described below, the notes may be converted at an initial conversion rate of             shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $             per share of common stock). The conversion rate is subject to adjustment if certain events occur.

We will settle conversions of notes by paying or delivering, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, as described under "—Conversion rights—Settlement upon conversion." You will not receive any separate cash payment for interest, if any, accrued and unpaid to the conversion date except under the limited circumstances described below.

The indenture does not limit the amount of debt, including secured debt, that may be issued by us or our subsidiaries under the indenture or otherwise. The indenture does not contain any financial covenants and does not restrict us from paying dividends or issuing or repurchasing our other securities. Other than the restrictions described under "—Fundamental change permits holders to require us to repurchase notes" and "—Consolidation, merger and sale of assets" below and except for the provisions set forth under "—Conversion rights—Increase in conversion rate upon conversion upon a make-whole fundamental change," the indenture does not contain any covenants or other provisions designed to afford holders of the notes protection in the event of a highly leveraged transaction involving us or in the event of a decline in our credit rating as the result of a takeover, recapitalization, highly leveraged transaction or similar restructuring involving us that could adversely affect such holders.

We may, without the consent of the holders, reopen the indenture for the notes and issue additional notes under the indenture with the same terms as the notes offered hereby (other than differences in the issue price and interest accrued prior to the issue date of such additional notes) in an unlimited aggregate principal amount; provided that if any such additional notes are not fungible with the notes initially offered hereby for U.S. federal income tax purposes, such additional notes will have a separate CUSIP number.

We do not intend to list the notes on any securities exchange or any automated dealer quotation system.

Purchase and cancellation

We will cause all notes surrendered for payment, repurchase (including as described below), registration of transfer or exchange or conversion, if surrendered to any person other than the trustee (including any of our agents, subsidiaries or affiliates), to be delivered to the trustee for cancellation and they will no longer be considered "outstanding" under the indenture upon their repurchase. All notes delivered to the trustee shall be cancelled promptly by the trustee. No notes shall be authenticated in exchange for any notes cancelled as provided in the indenture.

We may, to the extent permitted by law, and directly or indirectly (regardless of whether such notes are surrendered to us), repurchase notes in the open market or otherwise, whether by us or our subsidiaries or through a privately negotiated transaction or public tender or exchange offer or through counterparties to private agreements, including by cash-settled swaps or other derivatives, in each case, without prior notice to the holders of the notes. We will cause any

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notes so repurchased (other than notes repurchased pursuant to cash-settled swaps or other derivatives) to be surrendered to the trustee for cancellation, and they will no longer be considered "outstanding" under the indenture upon their repurchase.

Payments on the notes; paying agent and registrar; transfer and exchange

We will pay or cause the paying agent to pay the principal of, and interest on, notes in global form registered in the name of or held by The Depository Trust Company ("DTC") or its nominee in immediately available funds to DTC or its nominee, as the case may be, as the registered holder of such global note.

We will pay or cause the paying agent to pay the principal of any certificated notes at the office or agency designated by us for that purpose. We have initially designated the trustee as our paying agent and registrar and its corporate trust office as a place where notes may be presented for payment or for registration of transfer. We may, however, change the paying agent or registrar without giving prior notice to the holders of the notes, and we may act as paying agent or registrar. Interest on certificated notes will be payable (i) to holders holding certificated notes having an aggregate principal amount of $5,000,000 or less, by check mailed to the holders of these notes and (ii) to holders holding certificated notes having an aggregate principal amount of more than $5,000,000, either by check mailed to each such holder or, upon written application by such a holder to the registrar not later than the relevant regular record date, by wire transfer in immediately available funds to that holder's account within the United States, which application shall remain in effect until the holder notifies, in writing, the registrar to the contrary.

A holder of notes may transfer or exchange notes at the office of the registrar in accordance with the indenture. The registrar and the trustee may require a holder, among other things, to furnish appropriate endorsements and transfer documents. No service charge will be imposed by us, the trustee or the registrar for any registration of transfer or exchange of notes, but we may require a holder to pay a sum sufficient to cover any transfer tax or other similar governmental charge required by law or permitted by the indenture. We are not required to transfer or exchange any note surrendered for conversion or required repurchase.

The registered holder of a note will be treated as its owner for all purposes.

Interest

The notes will bear cash interest at a rate of         % per year until maturity. Interest on the notes will accrue from February     , 2014 or from the most recent date on which interest has been paid or duly provided for. Interest will be payable semiannually in arrears on February 15 and August 15 of each year, beginning on August 15, 2014.

Interest will be paid to the person in whose name a note is registered at the close of business on February 1 or August 1, as the case may be, immediately preceding the relevant interest payment date (each, a "regular record date"). Interest on the notes will be computed on the basis of a 360-day year composed of twelve 30-day months and, for partial months, on the basis of the number of days actually elapsed in a 30-day month.

If any interest payment date, the maturity date or any earlier required repurchase date upon a fundamental change of a note falls on a day that is not a business day, the required payment

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will be made on the next succeeding business day and no interest on such payment will accrue in respect of the delay. The term "business day" means, with respect to any note, any day other than a Saturday, a Sunday or a day on which the Federal Reserve Bank of New York is authorized or required by law or executive order to close or be closed.

Unless the context otherwise requires, all references to interest in this prospectus supplement include additional interest, if any, payable at our election as the sole remedy during certain periods for an event of default relating to the failure to comply with our reporting obligations as described under "—Events of default."

Additional amounts

If we consolidate with or merge with or into, or sell, convey, transfer or lease all or substantially all of our properties and assets to, another company and the resulting, surviving or transferee company is not organized and existing under the laws of the United States of America, any State thereof or the District of Columbia (such company or any successor thereto, the "surviving entity"), then all payments and deliveries made by, or on behalf of, the surviving entity under or with respect to the notes, including, but not limited to, payments of principal (including, if applicable, the fundamental change repurchase price), payments of interest and deliveries of common stock or other reference property and/or payments of cash, in each case, upon conversion, will be made without withholding or deduction for, or on account of, any present or future taxes, duties, assessments or governmental charges of whatever nature imposed or levied by a taxing authority within any jurisdiction in which the surviving entity is, for tax purposes, organized or resident or doing business or through which payment is made or deemed made (or any political subdivision or taxing authority thereof or therein) (each, as applicable, a "relevant taxing jurisdiction"), unless such withholding or deduction is required by law or by regulation or governmental policy having the force of law. In the event that any such withholding or deduction is so required, the surviving entity will pay such additional amounts (the "additional amounts") as may be necessary to ensure that the net amount received by the beneficial owner after such withholding or deduction (and after deducting or withholding any taxes on the additional amounts) will equal the amounts that would have been received by such beneficial owner had no such withholding or deduction been required; provided that no additional amounts will be payable:

(1)

for or on account of:

(a)   any tax, duty, assessment or other governmental charge that would not have been imposed but for:

(i)    the existence of any present or former connection between the holder or beneficial owner of such note and the relevant taxing jurisdiction, other than merely holding such note or the receipt of payments thereunder, including, without limitation, such holder or beneficial owner being or having been a national, domiciliary or resident of such relevant taxing jurisdiction or treated as a resident thereof or being or having been physically present or engaged in a trade or business therein or having or having had a permanent establishment therein;

(ii)   the presentation of such note (in cases in which presentation is required) more than 30 days after the later of the date on which the payment of the principal of

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(including the fundamental change repurchase price, if applicable) and interest on, such note or the delivery of common stock and other reference property and/or payments of cash, in each case, upon conversion of such note became due and payable pursuant to the terms thereof or was made or duly provided for; or

(iii)  the failure of the holder or beneficial owner to comply with a timely request from the surviving entity to provide certification, information, documents or other evidence concerning such holder's or beneficial owner's nationality, residence, identity or connection with the relevant taxing jurisdiction, or to make any declaration or satisfy any other reporting requirement relating to such matters, if and to the extent that due and timely compliance with such request is required by statute, regulation or administrative practice of the relevant taxing jurisdiction in order to reduce or eliminate any withholding or deduction as to which additional amounts would have otherwise been payable to such holder or beneficial owner;

(b)   any estate, inheritance, gift, sale, transfer, excise, personal property or similar tax, assessment or other governmental charge;

(c)    any tax, duty, assessment or other governmental charge that is payable otherwise than by withholding or deduction from payments under or with respect to the notes;

(d)   any tax, assessment, withholding or deduction required by sections 1471 through 1474 of the United States Internal Revenue Code of 1986, as amended ("FATCA"), any current or future Treasury Regulations or rulings promulgated thereunder, any law, regulation or other official guidance enacted in any jurisdiction implementing FATCA, any intergovernmental agreement between the United States and any other jurisdiction to implement FATCA or any law enacted by such other jurisdiction to give effect to such agreement, or any agreement with the U.S. Internal Revenue Service under FATCA; or

(e)   any combination of taxes referred to in the preceding clauses (a), (b), (c) or (d),

(2)   with respect to any payment of the principal of (including the fundamental change repurchase price, if applicable) and interest on, such note or the delivery of common stock or other reference property and/or payments of cash, in each case, upon conversion of such note to a holder, if the holder is a fiduciary, partnership or person other than the sole beneficial owner of that payment to the extent that such payment would be required to be included in the income under the laws of the relevant taxing jurisdiction, for tax purposes, of a beneficiary or settlor with respect to the fiduciary, a partner or member of that partnership or a beneficial owner who would not have been entitled to such additional amounts had that beneficiary, settlor, partner, member or beneficial owner been the holder thereof.

In the event that (i) the taxing authority of a relevant taxing jurisdiction determines that amounts should have been withheld or deducted in respect of any payments or deliveries under or with respect to the notes in excess of any amounts that were actually withheld or deducted by the surviving entity, and (ii) the surviving entity would have been required to pay additional amounts if such amounts had been withheld or deducted, then the surviving entity will indemnify the beneficial owner, on an after-tax basis, for any and all losses incurred as a result of its failure to make such withholdings and deductions and to pay additional amounts; provided that (i) only direct losses (and no consequential losses or damages) shall be recoverable hereunder, (ii) no indemnification shall be required hereunder unless and after the

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beneficial owner has exhausted all reasonable remedies available to it to reduce or eliminate the amount of such losses, and (iii) as a condition of such indemnification the beneficial owner shall reasonably assist the surviving entity in any attempt the surviving entity may make to seek to secure a reduction or refund of any such amounts, which reduction or refund shall be for the account of the surviving entity to the extent of any indemnification previously provided to the beneficial owner.

If the surviving entity is required to make any deduction or withholding from any payments with respect to the notes, the surviving entity will deliver to the trustee official tax receipts evidencing the remittance to the relevant tax authorities of the amounts so withheld or deducted or other evidence reasonably satisfactory to the trustee.

Whenever there is mentioned in any context the delivery of common stock or other reference property and/or payments of cash, in each case, upon conversion of any note or the payment of principal of (including the fundamental change repurchase price, if applicable) and interest on, any note or any other amount payable with respect to such note, such mention shall be deemed to include payment of additional amounts provided for in the indenture to the extent that, in such context, additional amounts are, were or would be payable in respect thereof.

Ranking

The notes will be our general unsecured obligations that rank senior in right of payment to all of our indebtedness that is expressly subordinated in right of payment to the notes. The notes will rank equal in right of payment with all of our liabilities that are not so subordinated. The notes will effectively rank junior to any of our secured indebtedness to the extent of the value of the assets securing such indebtedness. In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure secured debt will be available to pay obligations on the notes only after all indebtedness under such secured debt has been repaid in full from such assets. The notes will rank structurally junior to all indebtedness and other liabilities (including trade payables, but excluding intercompany obligations and liabilities of a type not required to be reflected on a balance sheet of such subsidiaries in accordance with GAAP) and preferred stock of our subsidiaries. We advise you that there may not be sufficient assets remaining to pay amounts due on any or all the notes then outstanding.

As of December 31, 2013, we had no consolidated indebtedness and our subsidiaries had no liabilities (including trade payables, but excluding intercompany obligations and liabilities of a type not required to be reflected on a balance sheet of such subsidiaries in accordance with GAAP).

We may not be able to pay the cash portions of any settlement amount upon conversion of the notes, or to pay cash for the fundamental change repurchase price upon a fundamental change if a holder requires us to repurchase notes as described below. See "Risk factors—Risks related to the notes—We may not have the ability to raise the funds necessary to settle conversions of the notes or to repurchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to pay cash upon conversion or repurchase of the notes."

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No optional redemption or sinking fund

We may not redeem the notes pursuant to the indenture prior to the maturity date, though the indenture does not limit our ability to make open-market purchases of or tender offers for the notes at any time. No "sinking fund" is provided for the notes, which means that we are not required to redeem or retire the notes periodically.

Conversion rights

General

Prior to the close of business on the business day immediately preceding May 15, 2018, the notes will be convertible only upon satisfaction of one or more of the conditions described under the headings "—Conversion upon satisfaction of sale price condition," "—Conversion upon satisfaction of trading price condition," and "—Conversion upon specified corporate events." On or after May 15, 2018 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their notes at any time irrespective of the foregoing conditions.

The conversion rate will initially be             shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $             per share of common stock). Upon conversion of a note, we will satisfy our conversion obligation by paying or delivering, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, all as set forth below under "—Settlement upon conversion." If we satisfy our conversion obligation solely in cash or through payment and delivery, as the case may be, of a combination of cash and shares of our common stock, the amount of cash and the number of shares of common stock, if any, due upon conversion will be based on a daily conversion value (as defined below) calculated on a proportionate basis for each trading day in an 80 trading day observation period (as defined below under "—Settlement upon conversion"). The trustee will initially act as the conversion agent.

A holder may convert fewer than all of such holder's notes so long as the notes converted are an integral multiple of $1,000 principal amount.

Upon conversion, you will not receive any separate cash payment for accrued and unpaid interest, if any, except as described below. We will not issue fractional shares of our common stock upon conversion of notes. Instead, we will pay cash in lieu of delivering any fractional share as described under "—Settlement upon conversion." Our payment and delivery, as the case may be, to you of the cash, shares of our common stock or a combination thereof, as the case may be, into which a note is convertible will be deemed to satisfy in full our obligation to pay:

•

the principal amount of the note; and

•

accrued and unpaid interest, if any, to, but not including, the relevant conversion date.

As a result, accrued and unpaid interest, if any, to, but not including, the relevant conversion date will be deemed to be paid in full rather than cancelled, extinguished or forfeited. Upon a conversion of notes into a combination of cash and shares of our common stock, accrued and unpaid interest will be deemed to be paid first out of the cash paid upon such conversion.

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Notwithstanding the immediately preceding paragraph, if notes are converted after 5:00 p.m., New York City time, on a regular record date for the payment of interest, holders of such notes at 5:00 p.m., New York City time, on such regular record date will receive the full amount of interest payable on such notes on the corresponding interest payment date notwithstanding the conversion. However, notes surrendered for conversion during the period from 5:00 p.m., New York City time, on any regular record date to 9:00 a.m., New York City time, on the immediately following interest payment date must be accompanied by funds equal to the amount of interest payable on the notes so converted; provided that no such payment need be made:

•

for conversions following the regular record date immediately preceding the maturity date;

•

if we have specified a fundamental change repurchase date that is after a regular record date and on or prior to the corresponding interest payment date, in respect of notes converted after the close of business on such record date and on or prior to the open of business on such interest payment date; or

•

to the extent of any overdue interest, if any overdue interest exists at the time of conversion with respect to such note.

Therefore, for the avoidance of doubt, all record holders on the regular record date immediately preceding the maturity date will receive the full interest payment due on the maturity date regardless of whether their notes have been converted following such regular record date.

If a holder converts notes, we will pay any documentary, stamp or similar issue or transfer tax due on any issuance of any shares of our common stock upon the conversion, unless the tax is due because the holder requests any such shares to be issued in a name other than the holder's name, in which case the holder will pay that tax.

Holders may surrender their notes for conversion only under the following circumstances:

Conversion upon satisfaction of sale price condition

Prior to the close of business on the business day immediately preceding May 15, 2018, a holder may surrender all or any portion of its notes for conversion at any time during any calendar quarter commencing after the calendar quarter ending on March 31, 2014 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day.

The "last reported sale price" of our common stock on any date means the closing sale price per share (or if no closing sale price is reported, the average of the bid and ask prices or, if more than one in either case, the average of the average bid and the average ask prices) on that date as reported in composite transactions for the principal U.S. national or regional securities exchange on which our common stock is traded. If our common stock is not listed for trading on a U.S. national or regional securities exchange on the relevant date, the "last reported sale price" will be the last quoted bid price per share for our common stock in the over-the-counter market on the relevant date as reported by OTC Markets Group Inc. or a similar organization. If our common stock is not so quoted, the "last reported sale price" will

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be the average of the mid-point of the last bid and ask prices per share for our common stock on the relevant date received from each of at least three nationally recognized independent investment banking firms selected by us for this purpose. The "last reported sale price" will be determined without regard to after-hours trading or any other trading outside of regular trading session hours.

On or after the occurrence of a share exchange event, the last reported sale price of a unit of reference property on any date will be determined in accordance with the definition of "last reported sale price" above (except in the case of a share exchange event in connection with which holders of our common stock receive only cash as set forth under "—Recapitalizations, reclassifications and changes of our common stock" below, in which case the last reported sale price will be equal to the per share amount of cash received by holders of our common stock in such share exchange event).

"Trading day" means a day on which (i) trading in our common stock (or other security for which a closing sale price must be determined) generally occurs on The NASDAQ Global Select Market or, if our common stock (or such other security) is not then listed on The NASDAQ Global Select Market, on the principal other U.S. national or regional securities exchange on which our common stock (or such other security) is then listed or, if our common stock (or such other security) is not then listed on a U.S. national or regional securities exchange, on the principal other market on which our common stock (or such other security) is then traded, and (ii) a last reported sale price for our common stock (or closing sale price for such other security) is available on such securities exchange or market. If our common stock (or such other security) is not so listed or traded, "trading day" means a "business day."

Conversion upon satisfaction of trading price condition

Prior to the close of business on the business day immediately preceding May 15, 2018, a holder of notes may surrender all or any portion of its notes for conversion at any time during the five business day period after any five consecutive trading day period (the "measurement period") in which the "trading price" per $1,000 principal amount of notes, as determined following a request by a holder of notes in accordance with the procedures described below, for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day, subject to compliance with the procedures and conditions described below concerning the bid solicitation agent's obligation to make a trading price determination.

The "trading price" per $1,000 principal amount of the notes on any date of determination means the average of the secondary market bid quotations obtained by the bid solicitation agent for $2,000,000 principal amount of notes at approximately 3:30 p.m., New York City time, on such determination date from three independent nationally recognized securities dealers we select for this purpose; provided that if three such bids cannot reasonably be obtained by the bid solicitation agent but two such bids are obtained, then the average of the two bids shall be used, and if only one such bid can reasonably be obtained by the bid solicitation agent, that one bid shall be used. If the bid solicitation agent cannot reasonably obtain at least one bid for $2,000,000 principal amount of notes from a nationally recognized securities dealer selected by us, then the trading price per $1,000 principal amount of notes for such determination date will be deemed to be less than 98% of the product of the last reported sale price of our common stock and the conversion rate. Any such determination will

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be conclusive absent manifest error. If we do not, when we are required to, instruct the bid solicitation agent to obtain bids, or if we give such instruction to the bid solicitation agent, and the bid solicitation agent fails to make such determination, then, in either case, the trading price per $1,000 principal amount of notes will be deemed to be less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each trading day of such failure.

The bid solicitation agent shall have no obligation to determine the trading price per $1,000 principal amount of notes unless we have requested such determination, and we shall have no obligation to make such request unless a holder of a note provides us with reasonable evidence that the trading price per $1,000 principal amount of notes would be less than 98% of the product of the last reported sale price of our common stock and the conversion rate. At such time, we shall instruct the bid solicitation agent to determine the trading price per $1,000 principal amount of notes beginning on the next trading day and on each successive trading day until the trading price per $1,000 principal amount of notes is greater than or equal to 98% of the product of the last reported sale price of our common stock and the conversion rate. If the trading price condition has been met, we will so notify the holders, the trustee and the conversion agent (if other than the trustee) within one business day. If, at any time after the trading price condition has been met, the trading price per $1,000 principal amount of notes is greater than or equal to 98% of the product of the last reported sale price of our common stock and the conversion rate for such trading day, we will so notify the holders, the trustee and the conversion agent (if other than the trustee).

The trustee will initially act as the bid solicitation agent.

Conversion upon specified corporate events

Certain distributions

If, prior to the close of business on the business day immediately preceding May 15, 2018, we elect to:

•

issue to all or substantially all holders of our common stock any rights, options or warrants entitling them, for a period of not more than 45 calendar days after the announcement date of such issuance, to subscribe for or purchase shares of our common stock at a price per share that is less than the average of the last reported sale prices of our common stock for the 10 consecutive trading day period ending on, and including, the trading day immediately preceding the date of announcement of such issuance; or

•

distribute to all or substantially all holders of our common stock our assets, debt securities or rights to purchase our securities, which distribution has a per share value, as reasonably determined by our board of directors or a committee thereof, exceeding 10% of the last reported sale price of our common stock on the trading day immediately preceding the date of announcement for such distribution,

then, in either case, we must notify the holders of the notes, the trustee and the conversion agent (if other than the trustee) at least 90 scheduled trading days prior to the ex-dividend date for such issuance or distribution. Once we have given such notice, holders may surrender all or any portion of their notes for conversion at any time until the earlier of 5:00 p.m., New York City time, on the business day immediately preceding the ex-dividend date for such issuance or distribution and our announcement that such issuance or distribution will not take place.

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Certain corporate events

If a transaction or event that constitutes a "fundamental change" (as defined under "—Fundamental change permits holders to require us to repurchase notes") or a "make-whole fundamental change" (as defined under "—Increase in conversion rate upon conversion upon a make-whole fundamental change") occurs prior to the close of business on the business day immediately preceding May 15, 2018, regardless of whether a holder has the right to require us to repurchase the notes as described under "—Fundamental change permits holders to require us to repurchase notes," or if we are a party to a consolidation, merger, binding share exchange, or transfer or lease of all or substantially all of our assets, in each case, pursuant to which our common stock would be converted into cash, securities or other assets (other than any merger or binding share exchange, in each case, solely for the purpose of changing our jurisdiction of organization that (x) does not constitute a fundamental change or a make-whole fundamental change and (y) results in a reclassification, conversion or exchange of outstanding shares of our common stock solely into shares of common stock of the surviving entity), all or any portion of a holder's notes may be surrendered for conversion at any time from or after the date that is 90 scheduled trading days prior to the anticipated effective date of the transaction (or, if later, the business day after we give notice of such transaction) until 35 trading days after the actual effective date of such transaction or, if such transaction also constitutes a fundamental change, until the related fundamental change repurchase date. We will notify holders, the trustee and the conversion agent (if other than the trustee) (i) as promptly as practicable following the date we publicly announce such transaction but in no event less than 90 scheduled trading days prior to the anticipated effective date of such transaction; or (ii) if we do not have knowledge of the anticipated effective date of such transaction at least 90 scheduled trading days prior to the anticipated effective date of such transaction, within five business days of the date upon which we have knowledge of the anticipated effective date of such transaction, but in no event later than the actual effective date of such transaction.

Conversions on or after May 15, 2018

On or after May 15, 2018, a holder may convert all or any portion of its notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date regardless of the foregoing conditions.

Conversion procedures

If you hold a beneficial interest in a global note, to convert you must comply with DTC's procedures for converting a beneficial interest in a global note and, if required, pay funds equal to interest payable on the next interest payment date to which you are not entitled.

If you hold a certificated note, to convert you must:

•

complete and manually sign the conversion notice on the back of the note, or a facsimile of the conversion notice;

•

deliver the conversion notice, which is irrevocable, and the note to the conversion agent;

•

if required, furnish appropriate endorsements and transfer documents; and

•

if required, pay funds equal to interest payable on the next interest payment date to which you are not entitled.

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We will pay any documentary, stamp or similar issue or transfer tax on the issuance of any shares of our common stock upon conversion of the notes, unless the tax is due because the holder requests such shares to be issued in a name other than the holder's name, in which case the holder will pay the tax.

We refer to the date you comply with the relevant procedures for conversion described above as the "conversion date."

If a holder has already delivered a repurchase notice as described under "—Fundamental change permits holders to require us to repurchase notes" with respect to a note, the holder may not surrender that note for conversion until the holder has withdrawn the repurchase notice in accordance with the relevant provisions of the indenture. If a holder submits its notes for required repurchase, the holder's right to withdraw the repurchase notice and convert the notes that are subject to repurchase will terminate at the close of business on the business day immediately preceding the relevant fundamental change repurchase date.

Settlement upon conversion

Upon conversion, we may choose to pay or deliver, as the case may be, either cash ("cash settlement"), shares of our common stock ("physical settlement") or a combination of cash and shares of our common stock ("combination settlement"), as described below. We refer to each of these settlement methods as a "settlement method."

All conversions for which the relevant conversion date occurs on or after May 15, 2018 will be settled using the same settlement method. Except for any conversions for which the relevant conversion date occurs on or after May 15, 2018, we will use the same settlement method for all conversions with the same conversion date, but we will not have any obligation to use the same settlement method with respect to conversions with different conversion dates. That is, we may choose for notes converted on one conversion date to settle conversions in physical settlement, and choose for notes converted on another conversion date cash settlement or combination settlement.

If we elect a settlement method, we will inform the trustee, the conversion agent (if other than the trustee) and the holders so converting through the conversion agent of the settlement method we have selected no later than the close of business on the second trading day immediately following the related conversion date (or in the case of any conversions for which the relevant conversion date occurs on or after May 15, 2018, no later than May 15, 2018). If we do not timely elect a settlement method, we will no longer have the right to elect cash settlement or physical settlement and we will be deemed to have elected combination settlement in respect of our conversion obligation, as described below, and the specified dollar amount (as defined below) per $1,000 principal amount of notes will be equal to $1,000. If we elect combination settlement, but we do not timely notify converting holders of the specified dollar amount per $1,000 principal amount of notes, such specified dollar amount will be deemed to be $1,000. It is our current intent and policy to settle conversions through combination settlement with a specified dollar amount per $1,000 principal amount of notes of $1,000.

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Settlement amounts will be computed as follows:

•

if we elect physical settlement, we will deliver to the converting holder in respect of each $1,000 principal amount of notes being converted a number of shares of common stock equal to the conversion rate;

•

if we elect cash settlement, we will pay to the converting holder in respect of each $1,000 principal amount of notes being converted cash in an amount equal to the sum of the daily conversion values for each of the 80 consecutive trading days during the related observation period; and

•

if we elect (or are deemed to have elected) combination settlement, we will pay or deliver, as the case may be, to the converting holder in respect of each $1,000 principal amount of notes being converted a "settlement amount" equal to the sum of the daily settlement amounts for each of the 80 consecutive trading days during the related observation period.

The "daily settlement amount," for each of the 80 consecutive trading days during the observation period, shall consist of:

•

cash equal to the lesser of (i) the maximum cash amount per $1,000 principal amount of notes to be received upon conversion as specified in the notice specifying our chosen settlement method (the "specified dollar amount"), if any, divided by 80 (such quotient, the "daily measurement value") and (ii) the daily conversion value; and

•

if the daily conversion value exceeds the daily measurement value, a number of shares equal to (i) the difference between the daily conversion value and the daily measurement value, divided by (ii) the daily VWAP for such trading day.

The "daily conversion value" means, for each of the 80 consecutive trading days during the observation period, 1.25% of the product of (1) the conversion rate on such trading day and (2) the daily VWAP for such trading day.

The "daily VWAP" means, for each of the 80 consecutive trading days during the relevant observation period, the per share volume-weighted average price as displayed under the heading "Bloomberg VWAP" on Bloomberg page "AMAG <equity> AQR" (or its equivalent successor if such page is not available) in respect of the period from the scheduled open of trading until the scheduled close of trading of the primary trading session on such trading day (or if such volume-weighted average price is unavailable, the market value of one share of our common stock on such trading day determined, using a volume-weighted average method, by a nationally recognized independent investment banking firm retained for this purpose by us). The "daily VWAP" will be determined without regard to after-hours trading or any other trading outside of the regular trading session trading hours.

The "observation period" with respect to any note surrendered for conversion means:

•

if the relevant conversion date occurs prior to May 15, 2018, the 80 consecutive trading day period beginning on, and including, the third trading day immediately succeeding such conversion date; and

•

if the relevant conversion date occurs on or after May 15, 2018, the 80 consecutive trading days beginning on, and including, the 82nd scheduled trading day immediately preceding the maturity date.

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For the purposes of determining amounts due upon conversion only, "trading day" means a day on which (i) there is no "market disruption event" (as defined below) and (ii) trading in our common stock generally occurs on The NASDAQ Global Select Market or, if our common stock is not then listed on The NASDAQ Global Select Market, on the principal other U.S. national or regional securities exchange on which our common stock is then listed or, if our common stock is not then listed on a U.S. national or regional securities exchange, on the principal other market on which our common stock is then listed or admitted for trading. If our common stock is not so listed or admitted for trading, "trading day" means a "business day."

"Scheduled trading day" means a day that is scheduled to be a trading day on the principal U.S. national or regional securities exchange or market on which our common stock is listed or admitted for trading. If our common stock is not so listed or admitted for trading, "scheduled trading day" means a "business day."

For the purposes of determining amounts due upon conversion, "market disruption event" means (i) a failure by the primary U.S. national or regional securities exchange or market on which our common stock is listed or admitted for trading to open for trading during its regular trading session or (ii) the occurrence or existence prior to 1:00 p.m., New York City time, on any scheduled trading day for our common stock for more than one half-hour period in the aggregate during regular trading hours of any suspension or limitation imposed on trading (by reason of movements in price exceeding limits permitted by the relevant stock exchange or otherwise) in our common stock or in any options contracts or future contracts relating to our common stock.

Except as described under "—Increase in conversion rate upon conversion upon a make-whole fundamental change" and "—Recapitalizations, reclassifications and changes of our common stock," we will deliver the consideration due in respect of conversion on the third business day immediately following the relevant conversion date, if we elect physical settlement, or on the third business day immediately following the last trading day of the relevant observation period, in the case of any other settlement method.

We will pay cash in lieu of delivering any fractional share of common stock issuable upon conversion based on the daily VWAP for the relevant conversion date (in the case of physical settlement) or based on the daily VWAP for the last trading day of the relevant observation period (in the case of combination settlement).

Each conversion will be deemed to have been effected as to any notes surrendered for conversion in accordance with the requirements set forth in the indenture on the conversion date; provided, however, that the person in whose name any shares of our common stock shall be issuable upon such conversion will become the holder of record of such shares as of the close of business on the conversion date (in the case of physical settlement) or the last trading day of the relevant observation period (in the case of combination settlement).

Exchange in lieu of conversion

When a holder surrenders its notes for conversion, we may, at our election (an "exchange election"), direct the conversion agent to surrender, on or prior to the second trading day following the conversion date, such notes to a financial institution designated by us for exchange in lieu of conversion. In order to accept any notes surrendered for conversion, the

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designated institution must agree to timely deliver, in exchange for such notes, the shares of our common stock, cash or combination thereof due upon conversion as described above under "—Settlement upon conversion". If we make an exchange election, we will, by the close of business on the second trading day following the relevant conversion date, notify the holder surrendering its notes for conversion that we have made the exchange election, and we will notify the designated financial institution of the settlement method we have elected with respect to such conversion and the relevant deadline for payment and/or delivery of shares of our common stock, cash or a combination thereof due upon conversion.

Any notes exchanged by the designated institution will remain outstanding. If the designated institution agrees to accept any notes for exchange but does not timely pay and/or deliver the shares of our common stock, cash or a combination thereof due upon conversion, or if such designated financial institution does not accept the notes for exchange, we will pay and/or deliver the shares of our common stock, cash or a combination thereof due upon conversion to the converting holder at the time and in the manner required under the indenture as if we had not made an exchange election.

Our designation of an institution to which the notes may be submitted for exchange does not require the institution to accept any notes (unless the financial institution has separately made an agreement with us). We may, but will not be obligated to, enter into a separate agreement with any designated financial institution that would compensate it for any such transaction.

Conversion rate adjustments

The conversion rate will be adjusted by us as described below, except that we will not make any adjustments to the conversion rate if holders of the notes participate (other than in the case of (x) a share split or share combination or (y) a tender or exchange offer), at the same time and upon the same terms as holders of our common stock and solely as a result of holding the notes, in any of the transactions described below without having to convert their notes as if they held a number of shares of our common stock equal to the conversion rate, multiplied by the principal amount (expressed in thousands) of notes held by such holder.

(1)   If we exclusively issue shares of our common stock as a dividend or distribution on shares of our common stock, or if we effect a share split or share combination, the conversion rate will be adjusted based on the following formula:

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Any adjustment made under this clause (1) shall become effective immediately after the open of business on the ex-dividend date for such dividend or distribution, or immediately after the open of business on the effective date for such share split or share combination, as applicable. If any dividend or distribution of the type described in this clause (1) is declared but not so paid or made, the conversion rate shall be immediately readjusted, effective as of the date our board of directors or a committee thereof determines not to pay such dividend or distribution, to the conversion rate that would then be in effect if such dividend or distribution had not been declared.

(2)   If we issue to all or substantially all holders of our common stock any rights, options or warrants entitling them, for a period of not more than 45 calendar days after the announcement date of such issuance, to subscribe for or purchase shares of our common stock at a price per share that is less than the average of the last reported sale prices of our common stock for the 10 consecutive trading day period ending on, and including, the trading day immediately preceding the date of announcement of such issuance, the conversion rate will be increased based on the following formula:

Any increase made under this clause (2) will be made successively whenever any such rights, options or warrants are issued and shall become effective immediately after the open of business on the ex-dividend date for such issuance. To the extent that such rights, options or warrants are not exercised prior to their expiration or shares of our common stock are not delivered after the expiration of such rights, options or warrants, the conversion rate shall be decreased to the conversion rate that would then be in effect had the increase with respect to the issuance of such rights, options or warrants been made on the basis of delivery of only the number of shares of our common stock actually delivered. If such rights, options or warrants are not so issued or if no such right, option or warrant is exercised prior to its expiration, the conversion rate shall be decreased to the conversion rate that would then be in effect if such ex-dividend date for such issuance had not occurred.

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For the purpose of this clause (2) and for the purpose of the first bullet point under "—Conversion upon specified corporate events—Certain distributions," in determining whether any rights, options or warrants entitle the holders to subscribe for or purchase shares of our common stock at less than such average of the last reported sale prices for the 10 consecutive trading day period ending on, and including, the trading day immediately preceding the date of announcement of such issuance, and in determining the aggregate offering price of such shares of our common stock, there shall be taken into account any consideration received by us for such rights, options or warrants and any amount payable on exercise or conversion thereof, the value of such consideration, if other than cash, to be determined by our board of directors or a committee thereof.

(3)   If we distribute shares of our capital stock, evidences of our indebtedness, other assets or property of ours or rights, options or warrants to acquire our capital stock or other securities, to all or substantially all holders of our common stock, excluding:

•

dividends, distributions or issuances as to which an adjustment was effected pursuant to clause (1) or (2) above;

•

dividends or distributions paid exclusively in cash as to which an adjustment was effected pursuant to clause (4) below;

•

any dividends or distributions of reference property in exchange for our common stock in connection with any reclassification, change, consolidation, merger, conveyance, transfer, sale, lease or other disposition described below under "—Recapitalizations, reclassifications and changes of our common stock"; and

•

spin-offs as to which the provisions set forth below in this clause (3) shall apply;

then the conversion rate will be increased based on the following formula:

Any increase made under the portion of this clause (3) above will become effective immediately after the open of business on the ex-dividend date for such distribution. If such distribution is not so paid or made, the conversion rate shall be decreased to be the conversion rate that would then be in effect if such distribution had not been declared. Notwithstanding

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the foregoing, if "FMV" (as defined above) is equal to or greater than "SP₀" (as defined above), in lieu of the foregoing increase, each holder of a note shall receive, in respect of each $1,000 principal amount thereof, at the same time and upon the same terms as holders of our common stock, the amount and kind of our capital stock, evidences of our indebtedness, other assets or property of ours or rights, options or warrants to acquire our capital stock or other securities that such holder would have received if such holder owned a number of shares of common stock equal to the conversion rate in effect on the ex-dividend date for the distribution.

With respect to an adjustment pursuant to this clause (3) where there has been a payment of a dividend or other distribution on our common stock of shares of capital stock of any class or series, or similar equity interest, of or relating to a subsidiary or other business unit, that are, or, when issued, will be, listed or admitted for trading on a U.S. national securities exchange, which we refer to as a "spin-off," the conversion rate will be increased based on the following formula:

 

The increase to the conversion rate under the preceding paragraph will occur on the last trading day of the valuation period; provided that in respect of any conversion of notes during the valuation period, references in the preceding paragraph to 10 trading days shall be deemed to be replaced with such lesser number of trading days as have elapsed between the ex-dividend date of such spin-off and the conversion date in determining the conversion rate. If the ex-dividend date of the spin-off is after the 10th trading day immediately preceding, and including, the end of any observation period in respect of a conversion of notes, references in the preceding paragraph to 10 trading days will be deemed to be replaced, solely in respect of that conversion, with such lesser number of trading days as have elapsed from, and including, the ex-dividend date for the spin-off to, and including, the last trading day of such observation period.

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(4)   If we pay or make any cash dividend or distribution to all or substantially all holders of our common stock, the conversion rate will be adjusted based on the following formula:

 

Any increase to the conversion rate made under this clause (4) shall become effective immediately after the open of business on the ex-dividend date for such dividend or distribution. If such dividend or distribution is not so paid, the conversion rate shall be decreased, effective as of the date our board of directors or a committee thereof determines not to make or pay such dividend or distribution, to be the conversion rate that would then be in effect if such dividend or distribution had not been declared. Notwithstanding the foregoing, if "C" (as defined above) is equal to or greater than "SP₀" (as defined above), in lieu of the foregoing increase, each holder of a note shall receive, for each $1,000 principal amount of notes, at the same time and upon the same terms as holders of shares of our common stock, the amount of cash that such holder would have received if such holder owned a number of shares of our common stock equal to the conversion rate on the ex-dividend date for such cash dividend or distribution.

(5)   If we or any of our subsidiaries make a payment pursuant to a tender or exchange offer for our common stock that is subject to the then-applicable tender offer rules under the Exchange Act, other than an odd lot tender offer, to the extent that the cash and value of any other consideration included in the payment per share of our common stock exceeds the average of the last reported sale prices of our common stock over the 10 consecutive trading day period commencing on, and including, the trading day next succeeding the last date on which tenders or exchanges may be made pursuant to such tender or exchange offer, the conversion rate will be increased based on the following formula:

 

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The adjustment to the conversion rate under the preceding paragraph will occur at the close of business on the 10th trading day immediately following, and including, the trading day next succeeding the date such tender or exchange offer expires; provided that in respect of any conversion of notes within the 10 trading days immediately following, and including, the trading day next succeeding the expiration date of any tender or exchange offer, references with respect to 10 trading days shall be deemed replaced with such lesser number of trading days as have elapsed between the expiration date of such tender or exchange offer and the conversion date in determining the conversion rate. In addition, if the trading day next succeeding the date such tender or exchange offer expires is after the 10th trading day immediately preceding, and including, the end of any observation period in respect of a conversion of notes, references in the preceding paragraph to 10 trading days shall be deemed to be replaced, solely in respect of that conversion, with such lesser number of trading days as have elapsed from, and including, the trading day next succeeding the date such tender or exchange offer expires to, and including, the last trading day of such observation period.

Notwithstanding the foregoing, if a conversion rate adjustment becomes effective on any ex-dividend date as described above, and a holder that has converted its notes on or after such ex-dividend date and on or prior to the related record date would be treated as the record holder of shares of our common stock as of the related conversion date as described under "—Settlement upon conversion" based on an adjusted conversion rate for such ex-dividend date, then, notwithstanding the foregoing conversion rate adjustment provisions, the conversion rate adjustment relating to such ex-dividend date will not be made for such converting holder. Instead, such holder will be treated as if such holder were the record owner of the shares of our common stock on an unadjusted basis and participate in the related dividend, distribution or other event giving rise to such adjustment.

Except as stated herein, we will not adjust the conversion rate for the issuance of shares of our common stock or any securities convertible into or exchangeable for shares of our common stock or the right to purchase shares of our common stock or such convertible or exchangeable securities.

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As used in this section, "ex-dividend date" means the first date on which the shares of our common stock trade on the applicable exchange or in the applicable market, regular way, without the right to receive the issuance, dividend or distribution in question, from us or, if applicable, from the seller of our common stock on such exchange or market (in the form of due bills or otherwise) as determined by such exchange or market, and "effective date" means the first date on which the shares of our common stock trade on the applicable exchange or in the applicable market, regular way, reflecting the relevant share split or share combination, as applicable.

We are permitted to increase the conversion rate of the notes by any amount for a period of at least 20 business days if our board of directors or a committee thereof determines that such increase would be in our best interest. We may also (but are not required to) increase the conversion rate to avoid or diminish income tax to holders of our common stock or rights to purchase shares of our common stock in connection with a dividend or distribution of shares (or rights to acquire shares) or similar event.

A holder may, in some circumstances, including a distribution of cash dividends to holders of our shares of common stock, be deemed to have received a distribution subject to U.S. federal income tax as a result of an adjustment or the nonoccurrence of an adjustment to the conversion rate. For a discussion of the U.S. federal income tax treatment of an adjustment to the conversion rate, see "Material U.S. federal income tax considerations."

If we have a rights plan in effect upon conversion of the notes into common stock, you will receive, in addition to any shares of common stock received in connection with such conversion, the rights under the rights plan. However, if, prior to any conversion, the rights have separated from the shares of common stock in accordance with the provisions of the applicable rights plan, the conversion rate will be adjusted at the time of separation as if we distributed to all or substantially all holders of our common stock, shares of our capital stock, evidences of indebtedness, assets, property, rights, options or warrants as described in clause (3) above, subject to readjustment in the event of the expiration, termination or redemption of such rights. We currently have a stockholder rights plan in effect.

Notwithstanding any of the foregoing, the conversion rate will not be adjusted:

•

upon the issuance of any shares of our common stock pursuant to any present or future plan providing for the reinvestment of dividends or interest payable on our securities and the investment of additional optional amounts in shares of our common stock under any plan;

•

upon the issuance of any shares of our common stock or options or rights to purchase those shares pursuant to any present or future employee, director or consultant benefit plan or program of or assumed by us or any of our subsidiaries;

•

upon the issuance of any shares of our common stock pursuant to any option, warrant, right or exercisable, exchangeable or convertible security not described in the preceding bullet and outstanding as of the date the notes were first issued;

•

upon the repurchase of any shares of our common stock pursuant to an open-market share repurchase program or other buy-back transaction that is not a tender offer or exchange offer of the kind described under clause (5) above;

•

solely for a change in the par value of our common stock; or

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•

for accrued and unpaid interest, if any.

We will not adjust the conversion rate pursuant to the clauses above unless the adjustment would result in a change of at least 1% in the then-effective conversion rate. However, we will carry forward any adjustment that we would otherwise have to make and take that adjustment into account in any subsequent adjustment. Notwithstanding the foregoing, all such carried-forward adjustments shall be made with respect to the notes (i) in connection with any subsequent adjustment to the conversion rate of at least 1% and (ii)(a) on each trading day of any observation period related to the conversion of notes (in the case of cash settlement or combination settlement) or (b) on the conversion date for any notes (in the case of physical settlement).

Adjustments to the conversion rate will be calculated to the nearest 1/10,000th of a share.

Recapitalizations, reclassifications and changes of our common stock

In the case of:

•

any recapitalization, reclassification or change of our common stock (other than changes resulting from a share split, share combination or change in par value),

•

any consolidation, merger or combination involving us,

•

any sale, lease or other transfer to a third party of the consolidated assets of ours and our subsidiaries substantially as an entirety, or

•

any statutory share exchange,

in each case, as a result of which our common stock would be converted into, or exchanged for, stock, other securities, other property or assets (including cash or any combination thereof) (any such event, a "share exchange event"), then, at and after the effective time of the transaction, the right to convert each $1,000 principal amount of notes will be changed into a right to convert such principal amount of notes into the kind and amount of shares of stock, other securities or other property or assets (including cash or any combination thereof) that a holder of a number of shares of common stock equal to the conversion rate immediately prior to such transaction would have owned or been entitled to receive (the "reference property") upon such transaction. However, at and after the effective time of the transaction, (i) we will continue to have the right to determine the form of consideration to be paid or delivered, as the case may be, upon conversion of notes, as set forth under "—Settlement upon conversion" and (ii)(x) any amount payable in cash upon conversion of the notes as set forth under "—Settlement upon conversion" will continue to be payable in cash, (y) any shares of our common stock that we would have been required to deliver upon conversion of the notes as set forth under "—Settlement upon conversion" will instead be deliverable in the amount and type of reference property that a holder of that number of shares of our common stock would have received in such transaction and (z) the daily VWAP and the last reported sale price, as applicable, will be calculated based on the value of a unit of reference property that a holder of one share of our common stock would have received in such transaction. If the transaction causes our common stock to be converted into, or exchanged for, the right to receive more than a single type of consideration (determined based in part upon any form of stockholder election), the reference property into which the notes will be convertible will be deemed to be (i) the weighted average of the types and amounts of consideration received by the holders of

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our common stock that affirmatively make such an election or (ii) if no holders of our common stock affirmatively make such an election, the types and amounts of consideration actually received by the holders of our common stock. If the holders of our common stock receive only cash in such transaction, then for all conversions that occur after the effective date of such transaction (i) the consideration due upon conversion of each $1,000 principal amount of notes shall be solely cash in an amount equal to the conversion rate in effect on the conversion date (as may be increased as described under "—Increase in conversion rate upon conversion upon a make-whole fundamental change"), multiplied by the price paid per share of common stock in such transaction and (ii) we will satisfy our conversion obligation by paying cash to converting holders on the third business day immediately following the conversion date. The supplemental indenture providing that the notes will be convertible into reference property will also provide for anti-dilution and other adjustments that are as nearly equivalent as possible to the adjustments described under "—Conversion rate adjustments" above. If the reference property in respect of any such transaction includes shares of stock, securities or other property or assets of a company other than us or the successor or purchasing company, as the case may be, in such transaction, such other company will also execute such supplemental indenture, and such supplemental indenture will contain such additional provisions to protect the interests of the holders, including the right of holders to require us to repurchase their notes upon a fundamental change as described under "—Fundamental change permits holders to require us to repurchase notes" below, as the board of directors reasonably considers necessary by reason of the foregoing. We will notify holders, the trustee and the conversion agent (if other than the trustee) of the weighted average as soon as practicable after such determination is made. We will agree in the indenture not to become a party to any such transaction unless its terms are consistent with the foregoing.

Adjustments of prices

Whenever any provision of the indenture requires us to calculate the last reported sale prices, the daily VWAPs, the daily conversion values or the daily settlement amounts over a span of multiple days (including an observation period and the "stock price" for purposes of a make-whole fundamental change), we will make appropriate adjustments (to the extent no corresponding adjustment is otherwise made pursuant to the provisions described under "—Conversion rate adjustments" above) to each to account for any adjustment to the conversion rate that becomes effective, or any event requiring an adjustment to the conversion rate where the ex-dividend date of the event occurs at any time during the period when such last reported sale prices, the daily VWAPs, the daily conversion values or the daily settlement amounts are to be calculated.

Increase in conversion rate upon conversion upon a make-whole fundamental change

If the "effective date" (as defined below) of a "make-whole fundamental change" (as defined below) occurs prior to the maturity date of the notes and a holder elects to convert its notes in connection with such make-whole fundamental change, we will, under certain circumstances, increase the conversion rate for the notes so surrendered for conversion by a number of additional shares of common stock (the "additional shares"), as described below. A "make-whole fundamental change" means any transaction or event that constitutes a fundamental change defined below in clause (1), (2) or (4) of the definition of "fundamental change" under "—Fundamental change permits holders to requires us to repurchase notes" below, after giving effect to any exceptions or exclusions from such definition, but without

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regard to the proviso in clause (2) of the definition thereof. A conversion of notes will be deemed for these purposes to be "in connection with" such make-whole fundamental change if the relevant notice of conversion of the notes is received by the conversion agent from, and including, the effective date of the make-whole fundamental change up to, and including, the business day immediately prior to the related fundamental change repurchase date (or, in the case of a make-whole fundamental change that would have been a fundamental change but for the proviso in clause (2) of the definition thereof, the 35th trading day immediately following the effective date of such make-whole fundamental change).

Upon surrender of notes for conversion in connection with a make-whole fundamental change, we will, at our option, satisfy our conversion obligation by physical settlement, cash settlement or combination settlement, as described under "—Conversion rights—Settlement upon conversion." However, if the consideration for our common stock in any make-whole fundamental change described in clause (2) of the definition of fundamental change is composed entirely of cash, for any conversion of notes following the effective date of such make-whole fundamental change, the conversion obligation will be calculated based solely on the "stock price" (as defined below) for the transaction and will be deemed to be an amount of cash per $1,000 principal amount of converted notes equal to the conversion rate (including any increase as described in this section), multiplied by such stock price. In such event, the conversion obligation will be determined and paid to holders in cash on the third business day following the conversion date. We will notify the trustee, the conversion agent (if other than the trustee) and holders of the effective date of any make-whole fundamental change no later than five business days after such effective date.

The amount, if any, by which the conversion rate will be increased will be determined by reference to the table below, based on the date on which the make-whole fundamental change occurs or becomes effective (the "effective date") and the price (the "stock price") paid (or deemed to be paid) per share of our common stock in the make-whole fundamental change. If the holders of our common stock receive in exchange for their common stock only cash in a make-whole fundamental change described in clause (2) of the definition of fundamental change, the stock price will be the cash amount paid per share. Otherwise, the stock price will be the average of the last reported sale prices of our common stock over the five trading day period ending on, and including, the trading day immediately preceding the effective date of the make-whole fundamental change.

The stock prices set forth in the column headings of the table below will be adjusted as of any date on which the conversion rate of the notes is otherwise adjusted. The adjusted stock prices will equal the stock prices immediately prior to such adjustment, multiplied by a fraction, the numerator of which is the conversion rate immediately prior to the adjustment giving rise to the stock price adjustment and the denominator of which is the conversion rate as so adjusted. The amounts by which the conversion rate will be increased as set forth in the table below will be adjusted in the same manner and at the same time as the conversion rate as set forth under "—Conversion rate adjustments."

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The following table sets forth the amount, if any, by which the conversion rate will be increased per $1,000 principal amount of notes for each stock price and effective date set forth below:

The exact stock prices and effective dates may not be set forth in the table above, in which case

•

if the stock price is between two stock prices in the table or the effective date is between two effective dates in the table, the amount by which the conversion rate will be increased will be determined by a straight-line interpolation between the amount of the conversion rate increase set forth for the higher and lower stock prices and the earlier and later effective dates, as applicable, based on a 365-day year;

•

if the stock price is greater than $             per share (subject to adjustment in the same manner as the stock prices set forth in the column headings of the table above), the conversion rate will not be increased; and

•

if the stock price is less than $             per share (subject to adjustment in the same manner as the stock prices set forth in the column headings of the table above), the conversion rate will not be increased.

Notwithstanding the foregoing, in no event will the conversion rate per $1,000 principal amount of notes exceed             shares of common stock, subject to adjustment in the same manner as the conversion rate as set forth under "—Conversion rate adjustments."

Our obligation to increase the conversion rate for notes converted in connection with a make-whole fundamental change could be considered a penalty, in which case the enforceability thereof would be subject to general principles of reasonableness and equitable remedies.

Fundamental change permits holders to require us to repurchase notes

If a "fundamental change" (as defined below in this section) occurs at any time prior to the maturity date, holders will have the right, at their option, to require us to repurchase for cash all of their notes, or any portion of the principal amount thereof that is equal to $1,000 or an integral multiple of $1,000. The fundamental change repurchase date will be a date specified by us that is not less than 20 or more than 35 business days following the date of our fundamental change notice as described below.

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The fundamental change repurchase price we are required to pay will be equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date (unless the fundamental change repurchase date falls after a regular record date but on or prior to the interest payment date to which such regular record date relates, in which case we will instead pay the full amount of accrued and unpaid interest to the holder of record on such regular record date, and the fundamental change repurchase price will be equal to 100% of the principal amount of the notes to be repurchased).

A "fundamental change" will be deemed to have occurred at the time after the notes are originally issued if any of the following occurs:

(1)   a "person" or "group" within the meaning of Section 13(d) of the Exchange Act, other than us, our subsidiaries and our and their employee benefit plans, has become the direct or indirect "beneficial owner," as defined in Rule 13d-3 under the Exchange Act, of our common equity representing more than 50% of the voting power of our common equity;

(2)   the consummation of (A) any recapitalization, reclassification or change of our common stock (other than changes resulting from a subdivision, combination or changes solely in par value) as a result of which our common stock would be converted into, or exchanged for, stock, other securities, other property or assets; (B) any share exchange, consolidation or merger of us pursuant to which our common stock will be converted into cash, securities or other property or assets; or (C) any sale, lease or other transfer in one transaction or a series of transactions of all or substantially all of the consolidated assets of us and our subsidiaries, taken as a whole, to any person other than one of our subsidiaries; provided, however, that a transaction described in clause (A) or (B) in which the holders of all classes of our common equity immediately prior to such transaction own, directly or indirectly, more than 50% of all classes of common equity of the continuing or surviving company or transferee or the parent thereof immediately after such transaction in substantially the same proportions as such ownership immediately prior to such transaction shall not be a fundamental change pursuant to this clause (2);

(3)   our stockholders approve any plan or proposal for our liquidation or dissolution; or

(4)   our common stock (or other common stock, American depositary receipts, ordinary shares or other common equity interests underlying the notes) ceases to be listed or quoted on any of The New York Stock Exchange, The NASDAQ Global Select Market or The NASDAQ Global Market (or any of their respective successors).

A transaction or transactions described in clause (1) or (2) above will not constitute a fundamental change, however, if at least 90% of the consideration received or to be received by our common stockholders, excluding cash payments for fractional shares and cash payments made pursuant to dissenters' appraisal rights, in connection with such transaction or transactions consists of shares of common stock, American depositary receipts, ordinary shares or other common equity interests, in each case, that are listed or quoted on any of The New York Stock Exchange, The NASDAQ Global Select Market or The NASDAQ Global Market (or any of their respective successors) or will be so listed or quoted when issued or exchanged in connection with such transaction or transactions and as a result of such transaction or transactions the notes become convertible into such consideration, excluding cash payments for

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fractional shares and cash payments made pursuant to dissenters' appraisal rights (subject to the provisions set forth above under "—Conversion rights—Settlement upon conversion").

On or before the 20th business day after the occurrence of a fundamental change, we will provide to all holders of the notes and the trustee and paying agent a notice of the occurrence of the fundamental change and of the resulting repurchase right. Such notice shall state, among other things:

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the events causing a fundamental change;

•

the effective date of the fundamental change;

•

the last date on which a holder may exercise the repurchase right;

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the fundamental change repurchase price;

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the fundamental change repurchase date;

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the name and address of the paying agent and the conversion agent, if applicable;

•

if applicable, the conversion rate and any adjustments to the conversion rate;

•

that the notes with respect to which a fundamental change repurchase notice has been delivered by a holder may be converted only if the holder withdraws the fundamental change repurchase notice in accordance with the terms of the indenture; and

•

the procedures that holders must follow to require us to repurchase their notes.

If notes are held in certificated form, to exercise the fundamental change repurchase right, you must deliver, prior to the close of business on the business day immediately preceding the fundamental change repurchase date, the notes to be repurchased, duly endorsed for transfer, together with a written repurchase notice, to the paying agent. Each repurchase notice must state:

•

if certificated, the certificate numbers of your notes to be delivered for repurchase;

•

the portion of the principal amount of notes to be repurchased, which must be $1,000 or an integral multiple thereof; and

•

that the notes are to be repurchased by us pursuant to the applicable provisions of the notes and the indenture.

If the notes are not in certificated form, such repurchase notice must comply with appropriate DTC procedures.

Holders may withdraw any repurchase notice (in whole or in part) by a written notice of withdrawal delivered to the paying agent prior to the close of business on the business day immediately preceding the fundamental change repurchase date. The notice of withdrawal shall state:

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the principal amount of the withdrawn notes, which must be $1,000 aggregate principal amount or an integral multiple thereof;

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if certificated notes have been issued, the certificate numbers of the withdrawn notes; and

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•

the principal amount, if any, which remains subject to the repurchase notice, which must be $1,000 aggregate principal amount or an integral multiple thereof.

If the notes are not in certificated form, such notice of withdrawal must comply with appropriate DTC procedures.

We will be required to repurchase the notes on the fundamental change repurchase date, subject to postponement to comply with applicable law. Holders who have exercised the repurchase right will receive payment of the fundamental change repurchase price on the later of (i) the fundamental change repurchase date and (ii) the time of book-entry transfer or the delivery of the notes. If the paying agent holds money sufficient to pay the fundamental change repurchase price of the notes on the fundamental change repurchase date, then, with respect to the notes that have been properly surrendered for repurchase and have not been validly withdrawn:

•

the notes will cease to be outstanding and interest will cease to accrue (whether or not book-entry transfer of the notes is made or whether or not the notes are delivered to the paying agent); and

•

all other rights of the holder will terminate (other than the right to receive the fundamental change repurchase price).

In connection with any repurchase offer pursuant to a fundamental change repurchase notice, we will, if required:

•

comply with the provisions of Rule 13e-4, Rule 14e-1 and any other tender offer rules under the Exchange Act that may then be applicable;

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file a Schedule TO or any other required schedule under the Exchange Act; and

•

otherwise comply with all federal and state securities laws in connection with any offer by us to repurchase the notes;

in each case, so as to permit the rights and obligations under this "—Fundamental change permits holders to require us to repurchase notes" to be exercised in the time and in the manner specified in the indenture.

No notes may be repurchased by us on any date at the option of holders upon a fundamental change if the principal amount of the notes has been accelerated, and such acceleration has not been rescinded, on or prior to such date (except in the case of an acceleration resulting from a default by us in the payment of the fundamental change repurchase price with respect to such notes).

The repurchase rights of the holders upon a fundamental change could discourage a potential acquirer of us. The fundamental change repurchase feature, however, is not the result of management's knowledge of any specific effort to obtain control of us by any means or part of a plan by management to adopt a series of anti-takeover provisions.

We will not be required to purchase, or to make an offer to purchase, the notes upon a fundamental change if a third party makes such an offer in the same manner, at the same time and otherwise in compliance with the requirements for an offer made by us as set forth above and such third party purchases all notes properly surrendered and not validly withdrawn under

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its offer in the same manner, at the same time and otherwise in compliance with the requirements for an offer made by us as set forth above.

To the extent that the provisions of any securities laws or regulations conflict with the provisions of the indenture relating to our obligations to purchase the notes upon a fundamental change, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under such provisions of the indenture by virtue of such conflict.

The term fundamental change is limited to specified transactions and may not include other events that might adversely affect our financial condition. In addition, the requirement that we offer to repurchase the notes upon a fundamental change may not protect holders in the event of a highly leveraged transaction, reorganization, merger or similar transaction involving us.

Furthermore, holders may not be entitled to require us to repurchase their notes upon a fundamental change or entitled to an increase in the conversion rate upon conversion as described under "—Increase in conversion rate upon conversion upon a make-whole fundamental change" in circumstances involving a significant change in the composition of our board, unless such change is in connection with a fundamental change or make-whole fundamental change, as the case may be, as described herein.

The definition of fundamental change includes a phrase relating to the sale, lease or other transfer of "all or substantially all" of our consolidated assets. There is no precise, established definition of the phrase "substantially all" under applicable law. Accordingly, the ability of a holder of the notes to require us to repurchase its notes as a result of the sale, lease or other transfer of less than all of our assets may be uncertain.

If a fundamental change were to occur, we may not have enough funds to pay the fundamental change repurchase price. Our ability to repurchase the notes for cash may be limited by restrictions on our ability to obtain funds for such repurchase through dividends from our subsidiaries, the terms of our then existing borrowing arrangements or otherwise. See "Risk factors—Risks related to the notes—We may not have the ability to raise the funds necessary to settle conversions of the notes or to repurchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to pay cash upon conversion or repurchase of the notes." If we fail to repurchase the notes when required following a fundamental change, we will be in default under the indenture. In addition, we may in the future incur other indebtedness with similar change in control provisions permitting our holders to accelerate or to require us to repurchase our indebtedness upon the occurrence of similar events or on some specific dates.

Consolidation, merger and sale of assets

The indenture provides that we shall not consolidate with or merge with or into, or sell, convey, transfer or lease all or substantially all of our properties and assets to, another person, unless (i) the resulting, surviving or transferee person (if not us) is (1) a corporation organized and existing under the laws of the United States of America, any State thereof or the District of Columbia or (2) a corporation or entity treated as a corporation for U.S. federal income tax purposes organized and existing under the laws of the Islands of Bermuda, the Netherlands,

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Belgium, Switzerland, Luxembourg, the Republic of Ireland, Canada or the United Kingdom, and such company (if not us) expressly assumes by supplemental indenture all of our obligations under the notes and the indenture (including, for the avoidance of doubt, the obligation to pay additional amounts, as set forth above under "—Additional amounts"); (ii) we shall have delivered to the trustee an officer's certificate and an opinion of counsel, each stating that such consolidation, merger, sale, conveyance, transfer or lease and such supplemental indenture, if any, comply with the indenture; and (iii) immediately after giving effect to such transaction, no default or event of default has occurred and is continuing under the indenture. Upon any such consolidation, merger or sale, conveyance, transfer or lease, the resulting, surviving or transferee person (if not us) shall succeed to, and may exercise every right and power of, ours under the indenture, and we shall be discharged from our obligations under the notes and the indenture except in the case of any such lease.

Although these types of transactions are permitted under the indenture, certain of the foregoing transactions could constitute a fundamental change permitting each holder to require us to repurchase the notes of such holder as described above.

This "—Consolidation, merger and sale of assets" section replaces the section of the accompanying prospectus under the heading "Description of Our Debt Securities—Consolidation, Merger or Sale" in its entirety and Article 10 and Section 4.05 of the base indenture will not apply to the notes.

Events of default

Each of the following is an event of default with respect to the notes:

(1)   default in any payment of interest on any note when due and payable and the default continues for a period of 30 days;

(2)   default in the payment of principal of any note when due and payable at its stated maturity, upon any required repurchase, upon declaration of acceleration or otherwise;

(3)   our failure to comply with our obligation to convert the notes in accordance with the indenture upon exercise of a holder's conversion right and such failure continues for a period of five business days;

(4)   our failure to give a fundamental change notice as described under "—Fundamental change permits holders to require us to repurchase notes" or notice of a specified corporate transaction as described under "—Conversion rights—Conversion upon specified corporate events," in each case when due and such failure continues for three business days after the due date for such notice;

(5)   our failure to comply with our obligations under "Consolidation, merger and sale of assets";

(6)   our failure for 60 days after written notice from the trustee or the holders of at least 25% in principal amount of the notes then outstanding has been received to comply with any of our other agreements contained in the notes or indenture;

(7)   default by us or any of our significant subsidiaries with respect to any mortgage, agreement or other instrument under which there may be outstanding, or by which there

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may be secured or evidenced, any indebtedness for money borrowed in excess of $15,000,000 (or its foreign currency equivalent) in the aggregate of ours and/or of any such significant subsidiary, whether such indebtedness now exists or shall hereafter be created (i) resulting in such indebtedness becoming or being declared due and payable prior to its stated maturity or (ii) constituting a failure to pay the principal or interest of any such debt when due and payable (after the expiration of all applicable grace periods) at its stated maturity, upon required repurchase, upon declaration of acceleration or otherwise, and such acceleration shall not have been rescinded or annulled or such failure to pay shall not have been cured, as the case may be, within 30 days after written notice to us by the trustee or to us and the trustee by the holders of at least 25% in principal amount of the notes then outstanding has been received;

(8)   certain events of bankruptcy, insolvency, or reorganization of us or any of our significant subsidiaries; or

(9)   a final judgment for the payment of $15,000,000 (or its foreign currency equivalent) or more (excluding any amounts covered by insurance) rendered against us or any of our significant subsidiaries, which judgment is not discharged or stayed within 60 days after (i) the date on which the right to appeal thereof has expired if no such appeal has commenced, or (ii) the date on which all rights to appeal have been extinguished.

A "significant subsidiary" is a subsidiary that is a "significant subsidiary" as defined in Article 1, Rule 1-02 of Regulation S-X promulgated by the SEC; provided that, in the case of a subsidiary that meets the criteria of clause (3) of the definition thereof but not clause (1) or (2) thereof, such subsidiary shall not be deemed to be a significant subsidiary unless the subsidiary's income from continuing operations before income taxes, extraordinary items and cumulative effect of a change in accounting principle exclusive of amounts attributable to any non-controlling interests for the last completed fiscal year prior to the date of such determination exceeds $15,000,000.

If an event of default occurs and is continuing, the trustee by notice to us, or the holders of at least 25% in principal amount of the outstanding notes by notice to us and the trustee, may, and the trustee at the request of such holders shall, declare 100% of the principal amount of and accrued and unpaid interest, if any, on all the notes to be due and payable. Upon such a declaration of acceleration, such principal and accrued and unpaid interest, if any, will be due and payable immediately. In case of certain events of bankruptcy, insolvency or reorganization, involving us, 100% of the principal of and accrued and unpaid interest on the notes will automatically become due and payable.

Notwithstanding the foregoing, the indenture will provide that, to the extent we elect, the sole remedy for an event of default relating to (i) our failure to file with the trustee pursuant to Section 314(a)(1) of the Trust Indenture Act any documents or reports that we are required to file with the SEC pursuant to Section 13 or 15(d) of the Exchange Act or (ii) our failure to comply with our obligations as set forth under "—Reports" below, will (x) for the first 180 days after the occurrence of such an event of default (beginning on, and including, the date on which such an event of default first occurs), consist exclusively of the right to receive additional interest on the notes equal to 0.25% per annum of the principal amount of notes outstanding for each day during such 180-day period on which such event of default is continuing and (y) for the period from, and including, the 181st day after the occurrence of such an event of

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default to, and including, the 270th day after the occurrence of such an event of default, consist exclusively of the right to receive additional interest on the notes equal to 0.50% per annum of the principal amount of notes outstanding for each day during such 90-day period on which such event of default is continuing. In no event will the additional interest described in this paragraph accrue at a rate in excess of 0.25% per annum during the initial 180-day period or 0.50% per annum during the subsequent 90-day period pursuant to the indenture, regardless of the number of events or circumstances giving rise to the requirement to pay such additional interest.

If we so elect, such additional interest will be payable in the same manner and on the same dates as the stated interest payable on the notes. On the 271st day after such event of default (if the event of default relating to the reporting obligations is not cured or waived prior to such 271st day), the notes will be subject to acceleration as provided above. The provisions of the indenture described in this paragraph will not affect the rights of holders of notes in the event of the occurrence of any other event of default. In the event we do not elect to pay the additional interest following an event of default in accordance with this paragraph or we elected to make such payment but do not pay the additional interest when due, the notes will be immediately subject to acceleration as provided above.

In order to elect to pay the additional interest as the sole remedy during the first 270 days after the occurrence of an event of default relating to the failure to comply with the reporting obligations in accordance with the immediately preceding paragraph, we must notify all holders of the notes, the trustee and the paying agent of such election prior to the beginning of such 270-day period. Upon our failure to timely give such notice, the notes will be immediately subject to acceleration as provided above.

If any portion of the amount payable on the notes upon acceleration is considered by a court to be unearned interest (through the allocation of the value of the instrument to the embedded warrant or otherwise), the court could disallow recovery of any such portion.

The holders of a majority in principal amount of the outstanding notes may waive all past defaults (except with respect to nonpayment of principal or interest or with respect to the failure to deliver the consideration due upon conversion) and rescind any such acceleration with respect to the notes and its consequences if (i) rescission would not conflict with any judgment or decree of a court of competent jurisdiction and (ii) all existing events of default, other than the nonpayment of the principal of and interest on the notes that have become due solely by such declaration of acceleration, have been cured or waived.

Each holder shall have the right to receive payment or delivery, as the case may be, of:

•

the principal (including the fundamental change repurchase price, if applicable) of;

•

accrued and unpaid interest, if any, on; and

•

the consideration due upon conversion of,

its notes, on or after the respective due dates expressed or provided for in the indenture, or to institute suit for the enforcement of any such payment or delivery, as the case may be, and such right to receive such payment or delivery, as the case may be, on or after such respective dates shall not be impaired or affected without the consent of such holder.

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Subject to the provisions of the indenture relating to the duties of the trustee, if an event of default occurs and is continuing, the trustee will be under no obligation to exercise any of the rights or powers under the indenture at the request or direction of any of the holders unless such holders have offered to the trustee indemnity or security reasonably satisfactory to it against any loss, liability or expense. Except to enforce the right to receive payment of principal or interest when due, or the right to receive payment or delivery of the consideration due upon conversion, no holder may pursue any remedy with respect to the indenture or the notes unless:

(1)   such holder has previously given the trustee written notice that an event of default with respect to the notes is continuing;

(2)   holders of at least 25% in aggregate principal amount of the outstanding notes have requested the trustee to pursue the remedy;

(3)   such holders have offered the trustee security or indemnity reasonably satisfactory to it against any loss, liability or expense;

(4)   the trustee has not complied with such request within 60 days after the receipt of the request and the offer of such security or indemnity; and

(5)   the holders of a majority in principal amount of the outstanding notes have not given the trustee a direction that, in the opinion of the trustee, is inconsistent with such request within such 60-day period.

Subject to certain restrictions, the holders of a majority in principal amount of the outstanding notes are given the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or of exercising any trust or power conferred on the trustee.

The indenture provides that in the event an event of default has occurred and is continuing, the trustee will be required in the exercise of its powers to use the degree of care that a prudent person would use in the conduct of its own affairs. The trustee, however, may refuse to follow any direction that conflicts with law or the indenture or that the trustee determines is unduly prejudicial to the rights of any other holder or that would involve the trustee in personal liability. Prior to taking any action under the indenture, the trustee will be entitled to indemnification reasonably satisfactory to it against any loss, liability or expense caused by taking or not taking such action.

The indenture provides that if a default occurs and is continuing and is known to a responsible officer of the trustee, the trustee must send to each holder notice of the default within 90 days after it occurs. Except in the case of a default in the payment of principal of or interest on any note or a default in the payment or delivery of the consideration due upon conversion, the trustee may withhold notice if and so long as it in good faith determines that withholding notice is in the interests of the holders. In addition, we are required to deliver to the trustee, within 120 days after the end of each fiscal year, a certificate indicating whether the signers thereof know of any default that occurred during the previous year. We are also required to deliver to the trustee, within 30 days after the occurrence thereof, written notice of any events which would constitute certain defaults, their status and what action we are taking or proposing to take in respect thereof; provided that we are not required to deliver such notice if the default has been cured.

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Payments of the fundamental change repurchase price, principal and interest that are not made when due will accrue interest per annum at the then-applicable interest rate from the required payment date.

This "—Events of default" section replaces the section of the accompanying prospectus under the heading "Description of Our Debt Securities—Events of Default Under the Indenture" in its entirety.

Modification and amendment

Subject to certain exceptions, the indenture or the notes may be amended with the consent of the holders of at least a majority in principal amount of the notes then outstanding (including without limitation, consents obtained in connection with a repurchase of, or tender or exchange offer for, notes) and, subject to certain exceptions, any past default or compliance with any provisions may be waived with the consent of the holders of a majority in principal amount of the notes then outstanding (including, without limitation, consents obtained in connection with a repurchase of, or tender or exchange offer for, notes). However, without the consent of each holder of an outstanding note affected, no amendment may, among other things:

(1)   reduce the amount of notes whose holders must consent to an amendment;

(2)   reduce the rate of or extend the stated time for payment of interest on any note;

(3)   reduce the principal of or extend the stated maturity of any note;

(4)   make any change that adversely affects the conversion rights of any notes other than as required by the indenture;

(5)   reduce the fundamental change repurchase price of any note or amend or modify in any manner adverse to the holders of notes our obligation to make such payments, whether through an amendment or waiver of provisions in the covenants, definitions or otherwise;

(6)   make any note payable in a currency, or at a place of payment, other than that stated in the note;

(7)   change the ranking of the notes;

(8)   impair the right of any holder to receive payment of principal and interest on such holder's notes on or after the due dates therefor or to institute suit for the enforcement of any payment on or with respect to such holder's notes;

(9)   change the provisions described under "—Additional amounts" above; or

(10) make any change in the amendment provisions that require each holder's consent or in the waiver provisions.

Without the consent of any holder, we and the trustee may amend the indenture and/or the notes to:

(1)   cure any ambiguity, omission, defect or inconsistency;

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(2)   provide for the assumption by a successor company of our obligations under the indenture and the notes;

(3)   add guarantees with respect to the notes;

(4)   secure the notes;

(5)   add to our covenants or events of default for the benefit of the holders or surrender any right or power conferred upon us;

(6)   make any change that does not adversely affect the rights of any holder;

(7)   in connection with any transaction described under "Conversion rights—Recapitalizations, reclassifications and changes of our common stock" above, provide that the notes are convertible into reference property, subject to the provisions described under "Conversion rights—Settlement upon conversion" above, and make certain related changes to the terms of the notes to the extent expressly required by the indenture;

(8)   increase the conversion rate as provided in the indenture;

(9)   provide for the issuance of additional notes in accordance with the limitations set forth in the indenture;

(10) comply with any requirement of the SEC in connection with the qualification of the indenture under the Trust Indenture Act;

(11) provide for the acceptance of appointment by a successor trustee or facilitate the administration of the trusts under the indenture by more than one trustee; or

(12) conform the provisions of the indenture to the "Description of notes" section in the preliminary prospectus supplement, as supplemented by the related pricing term sheet as evidenced in an officer's certificate.

Holders do not need to approve the particular form of any proposed amendment. It will be sufficient if such holders approve the substance of the proposed amendment. After an amendment under the indenture becomes effective, we are required to mail to the holders a notice briefly describing such amendment. However, the failure to give such notice to all the holders, or any defect in the notice, will not impair or affect the validity of the amendment.

This "—Modification and amendment" section replaces the section of the accompanying prospectus under the heading "Description of Our Debt Securities—Modification of Indenture; Waiver" in its entirety.

Discharge

We may satisfy and discharge our obligations under the indenture by delivering to the registrar for cancellation all outstanding notes or by depositing with the trustee or delivering to the holders, as applicable, after the notes have become due and payable, whether at maturity, at any fundamental change repurchase date, upon conversion or otherwise, cash or cash and/or shares of common stock, solely to satisfy outstanding conversions, as applicable, sufficient to pay all of the outstanding notes and paying all other sums payable under the indenture by us. Such discharge is subject to terms contained in the indenture.

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This "—Discharge" section replaces the section of the accompanying prospectus under the heading "Description of Our Debt Securities—Discharge" in its entirety.

Calculations in respect of notes

Except as otherwise provided above, we will be responsible for making all calculations called for under the notes. These calculations include, but are not limited to, determinations of the stock price, the last reported sale prices of our common stock, the daily VWAPs, the daily conversion values, the daily settlement amounts, accrued interest payable on the notes and the conversion rate of the notes. We will make all these calculations in good faith and, absent manifest error, our calculations will be final and binding on holders of notes. We will provide a schedule of our calculations to each of the trustee and the conversion agent, and each of the trustee and the conversion agent is entitled to rely conclusively upon the accuracy of our calculations without independent verification. The trustee will forward our calculations to any holder of notes upon the written request of that holder.

Reports

The indenture provides that any documents or reports that we are required to file with the SEC pursuant to Section 13 or 15(d) of the Exchange Act (excluding, for the avoidance of doubt, any such documents or reports (or portions thereof) that are subject to confidential treatment and any correspondence with the SEC) (collectively, the "financial information") must be delivered or filed by us with the trustee within 15 days after the same are required to be filed with the SEC (giving effect to any grace period provided by Rule 12b-25 under the Exchange Act). Documents filed by us with the SEC via the EDGAR system (or any successor thereto) will be deemed to be delivered and filed with the trustee as of the time such documents are filed via EDGAR (or any successor thereto) it being understood that the trustee shall have no responsibility to determine if such filings have been made. Notwithstanding the foregoing, at any time we are otherwise not required to file documents or reports with the SEC pursuant to Section 13 or 15(d) of the Exchange Act and the conversion obligation for the notes may be satisfied by the delivery of reference property consisting of, in whole or in part, another entity's common stock, American depositary receipts, ordinary shares or other common equity, as the case may be, we may satisfy our obligations under this covenant by delivering or filing the financial information of such entity within the same time periods and in the same manner described above.

Trustee

Wilmington Trust, National Association is the trustee, registrar, paying agent, conversion agent and bid solicitation agent. Wilmington Trust, National Association, in each of its capacities, including without limitation as trustee, registrar, paying agent, conversion agent and bid solicitation agent, assumes no responsibility for the accuracy or completeness of the information concerning us or our affiliates or any other party contained in this document or the related documents or for any failure by us or any other party to disclose events that may have occurred and may affect the significance or accuracy of such information.

We maintain banking relationships in the ordinary course of business with the trustee and its affiliates.

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Governing law

The indenture provides that it and the notes, and any claim, controversy or dispute arising under or related to the indenture or the notes, will be governed by and construed in accordance with the laws of the State of New York.

Book-entry, settlement and clearance

The global notes

The notes will be initially issued in the form of one or more registered notes in global form, without interest coupons (the "global notes"). Upon issuance, each of the global notes will be deposited with the trustee as custodian for DTC and registered in the name of Cede & Co., as nominee of DTC.

Ownership of beneficial interests in a global note will be limited to persons who have accounts with DTC ("DTC participants") or persons who hold interests through DTC participants. We expect that under procedures established by DTC:

•

upon deposit of a global note with DTC's custodian, DTC will credit portions of the principal amount of the global note to the accounts of the DTC participants designated by the underwriters; and

•

ownership of beneficial interests in a global note will be shown on, and transfer of ownership of those interests will be effected only through, records maintained by DTC (with respect to interests of DTC participants) and the records of DTC participants (with respect to other owners of beneficial interests in the global note).

Beneficial interests in global notes may not be exchanged for notes in physical, certificated form except in the limited circumstances described below.

Book-entry procedures for the global notes

All interests in the global notes will be subject to the operations and procedures of DTC. We provide the following summary of those operations and procedures solely for the convenience of investors. The operations and procedures of DTC are controlled by that settlement system and may be changed at any time. Neither we nor the underwriters are responsible for those operations or procedures.

DTC has advised us that it is:

•

a limited purpose trust company organized under the laws of the State of New York;

•

a "banking organization" within the meaning of the New York State Banking Law;

•

a member of the Federal Reserve System;

•

a "clearing corporation" within the meaning of the Uniform Commercial Code; and

•

a "clearing agency" registered under Section 17A of the Exchange Act.

DTC was created to hold securities for its participants and to facilitate the clearance and settlement of securities transactions between its participants through electronic book-entry changes to the accounts of its participants. DTC's participants include securities brokers and dealers, including the underwriters; banks and trust companies; clearing corporations and other organizations. Indirect access to DTC's system is also available to others such as banks, brokers, dealers and trust companies; these indirect participants clear through or maintain a custodial

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relationship with a DTC participant, either directly or indirectly. Investors who are not DTC participants may beneficially own securities held by or on behalf of DTC only through DTC participants or indirect participants in DTC.

So long as DTC's nominee is the registered owner of a global note, that nominee will be considered the sole owner or holder of the notes represented by that global note for all purposes under the indenture. Except as provided below, owners of beneficial interests in a global note:

•

will not be entitled to have notes represented by the global note registered in their names;

•

will not receive or be entitled to receive physical, certificated notes; and

•

will not be considered the owners or holders of the notes under the indenture for any purpose, including with respect to the giving of any direction, instruction or approval to the trustee under the indenture.

As a result, each investor who owns a beneficial interest in a global note must rely on the procedures of DTC to exercise any rights of a holder of notes under the indenture (and, if the investor is not a participant or an indirect participant in DTC, on the procedures of the DTC participant through which the investor owns its interest).

Payments of principal and interest with respect to the notes represented by a global note will be made by the paying agent to DTC's nominee as the registered holder of the global note. Neither we nor the paying agent will have any responsibility or liability for the payment of amounts to owners of beneficial interests in a global note, for any aspect of the records relating to or payments made on account of those interests by DTC, or for maintaining, supervising or reviewing any records of DTC relating to those interests.

Payments by participants and indirect participants in DTC to the owners of beneficial interests in a global note will be governed by standing instructions and customary industry practice and will be the responsibility of those participants or indirect participants and DTC.

Transfers between participants in DTC will be effected under DTC's procedures and will be settled in same-day funds.

Certificated notes

Notes in physical, certificated form will be issued and delivered to each person that DTC identifies as a beneficial owner of the related notes only if:

•

DTC notifies us at any time that it is unwilling or unable to continue as depositary for the global notes and a successor depositary is not appointed within 90 days;

•

DTC ceases to be registered as a clearing agency under the Exchange Act and a successor depositary is not appointed within 90 days; or

•

an event of default with respect to the notes has occurred and is continuing and such beneficial owner requests that its notes be issued in physical, certificated form.

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Description of convertible note hedge and warrant transactions

In connection with the pricing of the notes, we expect to enter into convertible note hedge transactions with one or more financial institutions, which we refer to as the option counterparties. The convertible note hedge transactions will cover, subject to anti-dilution adjustments substantially similar to those applicable to the notes, the number of shares of our common stock underlying the notes. Concurrently with entering into the convertible note hedge transactions, we also expect to enter into warrant transactions with the option counterparties whereby we will sell to the option counterparties warrants to purchase, subject to customary anti-dilution adjustments, up to the same number of shares of our common stock.

We intend to use approximately $              million of the net proceeds from this offering to pay the cost of the convertible note hedge transactions (after such cost is partially offset by the proceeds to us from the sale of the warrant transactions). If the underwriters exercise their over-allotment option, we may sell additional warrants and use a portion of the proceeds from the sale of the additional notes, together with the proceeds from the sale of the additional warrants, to enter into additional convertible note hedge transactions.

The convertible note hedge transactions are expected generally to reduce the potential dilution and/or offset cash payments due upon conversion of the notes in the event that the market price per share of our common stock, as measured under the terms of the convertible note hedge transactions, is greater than the strike price of the convertible note hedge transactions, which initially corresponds to the conversion price of the notes and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of the notes. If, however, the market price per share of our common stock, as measured under the terms of the warrant transactions, exceeds the strike price of the warrants, there would nevertheless be dilution to the extent that such market price exceeds the strike price of the warrants.

We will not be required to make any cash payments to the option counterparties or their affiliates upon the exercise of the options that are a part of the convertible note hedge transactions, but we will be entitled to receive from them a number of shares of our common stock and/or an amount of cash generally based on the amount by which the market price per share of our common stock, as measured under the terms of the convertible note hedge transactions, is greater than the strike price of the convertible note hedge transactions during the relevant valuation period under the convertible note hedge transactions. Additionally, if the market price per share of our common stock, as measured under the terms of the warrant transactions, exceeds the strike price of the warrants during the measurement period at the maturity of the warrants, we will owe the option counterparties a number of shares of our common stock in an amount based on the excess of such market price per share of our common stock over the strike price of the warrants.

The convertible note hedge transactions and the warrant transactions are separate transactions entered into by us with the option counterparties, are not part of the terms of the notes and will not change the holders' rights under the notes. As a holder of the notes, you will not have any rights with respect to the convertible note hedge transactions or the warrant transactions.

For a discussion of the potential impact of any market or other activity by the option counterparties or their affiliates in connection with these convertible note hedge and warrant transactions, see "Underwriting—Convertible note hedge and warrant transactions" and "Risk Factors—Risks related to the notes—The convertible note hedge and warrant transactions may affect the value of the notes and our common stock."

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Description of capital stock

Our authorized capital stock consists of 58,750,000 shares of common stock, par value $0.01 per share, and 2,000,000 shares of preferred stock, par value $0.01 per share, issuable in multiple series, subject to limitations provided in our certificate of incorporation. To date, our board has designated 45,000 of the 2,000,000 authorized shares of preferred stock as Series A Junior Participating Preferred Stock, which series is described in greater detail below under "—Preferred share purchase rights plan."

Common stock

Holders of our common stock are entitled to one vote per share and vote together as a single class on all matters to be voted on by our stockholders. Pursuant to our certificate of incorporation, there are no cumulative voting rights in the election of directors. The approval of corporate actions may also require the approval of the holders of any series of our preferred stock. Our common stock will be the only type of our capital stock entitled to vote in the election and removal of directors and other matters presented to our stockholders from time to time, unless we issue voting preferred stock or our certificate of incorporation or the law requires otherwise. Our common stockholders will be entitled to receive dividends and distributions declared by our board of directors, or our board of directors, to the extent permitted by outstanding series of preferred stock and by our certificate of incorporation. If a dividend is declared, it will be distributed pro rata to our common stockholders on a per share basis. If we are liquidated or dissolved, our common stockholders will be entitled to receive our assets and funds available for distribution to common stockholders in proportion to the number of shares they hold. Our common stockholders may not receive any assets or funds until our creditors have been paid in full and the preferential or participating rights of our preferred stockholders, if any, have been satisfied. Holders of our common stock will not have any preemptive, subscription or conversion rights with respect to shares of our common stock. We may issue additional shares of our common stock, if authorized by our board of directors, without the common stockholders' approval, unless required by Delaware law or a stock exchange on which our securities are traded. The issuance of additional shares could have the effect of diluting any earnings per share and the book value per share of outstanding shares of common stock. If we receive the appropriate payment, shares of our common stock that we issue will be fully paid and non-assessable. There are no redemption or sinking fund provisions applicable to our common stock.

Preferred stock

We are authorized to issue up to 2,000,000 shares of preferred stock, par value $0.01value per share, in multiple series and to fix the designations, powers, preferences and the relative, participating, optional or other special rights of the shares of each series and any qualifications, limitations and restrictions thereon as set forth in our certificate of incorporation. Any such preferred stock issued by us may rank prior to the common stock as to dividend rights, liquidation preference or both, may have full or limited voting rights and may be convertible into shares of common stock. The issuance of preferred stock could have the effect of making it more difficult for a third party to acquire, or of discouraging a third party from acquiring or seeking to acquire, a significant portion of the outstanding common stock.

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Preferred share purchase rights plan

Each outstanding share of our common stock has attached to it one preferred share purchase right, which we refer to as a right. Each right entitles the registered holder of our common stock to purchase from us one one-thousandth of a share of Series A Junior Participating Preferred Stock, which we refer to as participating preferred shares, at a price of $250 per one one-thousandth of a participating preferred share, subject to adjustment. Each one one-thousandth of a share of participating preferred shares has designations and powers, preferences and rights, and the qualifications, limitations and restrictions that make its value approximately equal to the value of a share of our common stock at the end of the ten-year term of the rights. The description and terms of the rights are set forth in a Rights Agreement, dated as of September 4, 2009, between us and American Stock Transfer & Trust Company, LLC, as rights agent, or the rights agreement, which is incorporated by reference as an exhibit into the registration statement of which this prospectus supplement is a part. See "Description of Our Preferred Stock—Preferred Share Purchase Rights Plan" in the accompanying prospectus for a more detailed description of our Rights Agreement. We amended our shareholder rights plan to allow for this note offering, the convertible note hedge and warrant transactions and related derivative transactions without triggering the exercisability of these rights issued under our shareholder rights plan.

Description of certain provisions of Delaware law and our certificate of incorporation and by-laws

We are organized as a Delaware corporation. The following is a summary of our certificate of incorporation and by-laws and certain provisions of the Delaware General Corporation Law, or the DGCL. Because it is a summary, it does not contain all the information that may be important to you. If you want more information, you should read our entire certificate of incorporation and by-laws, copies of which are filed with the SEC as exhibits to the registration statement of which this prospectus supplement is a part.

Classification of directors

Our by-laws provide that, except as otherwise required by specific provisions of the certificate of incorporation relating to the rights of holders of any class or series of preferred stock to elect additional directors under specified circumstances, the number of our directors may be fixed from time to time by a resolution adopted by a majority of our board of directors but must not be less than one. Our board of directors is not classified into classes. A director may be removed, with or without cause, by the holders of a majority of the shares then entitled to vote at an election of directors, subject to the rights of any series of preferred stock then outstanding.

Meetings of stockholders

Except as otherwise required by law and subject to the rights of holders of any class or series of preferred stock, special meetings of the stockholders may only be called by our President or by our board of directors. No business other than that stated in the notice of meeting may be transacted at any special meeting of stockholders. Our by-laws limit the business that may be conducted at an annual meeting of stockholders to those matters properly brought before the meeting.

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Limitation of liability and indemnification

Our certificate of incorporation provides that we shall indemnify our directors and officers to the fullest extent that Delaware law permits. Our certificate of incorporation also provides that we, by action of our board of directors, may provide indemnification to our employees and agents with the same scope and effect as the indemnification of our officers and directors. Delaware law permits a corporation to indemnify any director, officer, employee or agent made or threatened to be made a party to any pending or completed proceeding if the person acted in good faith and in a manner that the person reasonably believed to be in the best interests of the corporation and, with respect to any criminal proceeding, had no reasonable cause to believe that his or her conduct was unlawful.

Our certificate of incorporation limits the liability of our directors to the fullest extent permitted by the DGCL. Delaware law provides that directors will not be personally liable for monetary damages for breach of their fiduciary duties as directors, except liability for:

•

any breach of their duty of loyalty to the corporation or its stockholders;

•

acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law;

•

unlawful payments of dividends or unlawful stock repurchases or redemptions; or

•

any transaction from which the director derived an improper personal benefit.

The effect of this provision may be to reduce the likelihood of derivative litigation against directors for breach of their duty of care, even though the action, if successful, might otherwise have benefited us and our stockholders. This provision has no effect on any non-monetary remedies that may be available to us or our stockholders, nor does it relieve us or our officers or directors from compliance with federal or state securities laws.

Each of our directors and executive officers is party to an indemnification agreement that provides specific contractual assurance that the indemnification protection promised by certificate of incorporation and by-laws will be available.

As permitted by our certificate of incorporation, we have purchased and maintain insurance on behalf of our directors and officers for any expense, liability or loss incurred by them arising out of their actions in that capacity if we would have the power to indemnify such person against such expense, liability or loss under the DGCL.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers or persons controlling the registrant pursuant to the foregoing provisions, the registrant has been informed that in the opinion of the SEC such indemnification is against public policy and is therefore unenforceable.

Undesignated preferred stock

Our certificate of incorporation provides for 2,000,000 authorized shares of preferred stock (of which our board has designated 45,000 shares as Series A Junior Participating Preferred Stock). The existence of authorized but unissued shares of preferred stock may enable our board of directors to render more difficult or to discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest or otherwise. For example, if in the due exercise of its

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fiduciary obligations, our board of directors were to determine that a takeover proposal is not in the best interests of our stockholders, our board of directors could cause shares of preferred stock to be issued without stockholder approval in one or more private offerings or other transactions that might dilute the voting or other rights of the proposed acquirer or insurgent stockholder or stockholder group. In this regard, our certificate of incorporation grants our board of directors broad power to establish the rights and preferences of authorized and unissued shares of preferred stock. The issuance of shares of preferred stock could decrease the amount of earnings and assets available for distribution to holders of shares of common stock. The issuance may also adversely affect the rights and powers, including voting rights, of these holders and may have the effect of delaying, deterring or preventing a change in control of us.

Section 203 of the Delaware General Corporation Law

Section 203 of the DGCL prohibits a defined set of transactions between a Delaware corporation, such as us, and an "interested stockholder." An interested stockholder is defined as a person who, together with any affiliates or associates of such person, beneficially owns, directly or indirectly, 15% or more of the outstanding voting stock of a Delaware corporation. This provision may prohibit business combinations between an interested stockholder and a corporation for a period of three years after the date the interested stockholder becomes an interested stockholder. The term "business combination" is broadly defined to include mergers, consolidations, sales or other dispositions of assets having a total value in excess of 10% of the consolidated assets of the corporation, and some other transactions that would increase the interested stockholder's proportionate share ownership in the corporation.

This prohibition is effective unless:

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either the business combination or the transaction that resulted in the interested stockholder becoming an interested stockholder is approved by our board prior to the time the interested stockholder becomes an interested stockholder;

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the interested stockholder owns at least 85% of our voting stock, other than stock held by directors who are also officers or by qualified employee stock plans, upon completion of the transaction in which it becomes an interested stockholder; or

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the business combination is approved by a majority of our board and by the affirmative vote of 66²/3% of the outstanding voting stock that is not owned by the interested stockholder.

In general, the prohibitions do not apply to business combinations with persons who were interested stockholders prior to the corporation becoming subject to Section 203.

Stock exchange listing

Our common stock is listed on the NASDAQ Global Select Market under the symbol "AMAG".

Transfer agent and registrar

American Stock Transfer & Trust Company is the transfer agent and registrar for our common stock.

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Material U.S. federal income tax considerations

The following discussion is a summary of the material U.S. federal income tax considerations relating to the purchase, ownership and disposition of the notes, but does not purport to be a complete analysis of all potential tax effects and does not address the effects of any state, local, alternative minimum, estate, gift or non-U.S. tax laws. This discussion is based upon the U.S. Internal Revenue Code of 1986, as amended (the "Code"), Treasury regulations issued thereunder, and judicial and administrative interpretations thereof, each as in effect on the date hereof, and all of which are subject to change, possibly with retroactive effect and to differing interpretations, all of which could result in U.S. federal income tax considerations different from those described below. No rulings from the Internal Revenue Service ("IRS") have been or are expected to be sought with respect to the matters discussed below. The discussion below is not binding on the IRS or the courts. Accordingly, there can be no assurance that the IRS will not take a different position concerning the tax consequences of the purchase, ownership or disposition of the notes or that any such position would not be sustained.

This discussion does not address all of the U.S. federal income tax considerations that might be relevant to a beneficial owner in light of such beneficial owner's particular circumstances or to beneficial owners subject to special treatment under the U.S. federal income tax laws, including:

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a dealer in securities;

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a financial institution;

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a regulated investment company;

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a real estate investment trust;

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a tax-exempt organization;

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an insurance company;

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a person holding the notes as part of a hedging, integrated, or conversion transaction or a straddle, or a person deemed to sell notes or common stock under the constructive sale provisions of the Code;

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a trader in securities that has elected the mark-to-market method of accounting for securities;

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an entity that is treated as a partnership for U.S. federal income tax purposes;

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a person who is an investor in a pass-through entity;

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a U.S. person whose "functional currency" is not the U.S. dollar;

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a "controlled foreign corporation";

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a "passive foreign investment company"; or

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a United States expatriate.

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In addition, this discussion is limited to persons who purchase the notes for cash at original issue and at their "issue price" (the first price at which a substantial amount of the notes are sold to the public for cash, excluding sales to bond houses, brokers or similar persons or organizations acting in the capacity of underwriters, placement agents or wholesalers) and who hold the notes as capital assets within the meaning of Section 1221 of the Code.

This summary does not address all aspects of United States federal income taxes, does not deal with all tax considerations that may be relevant to beneficial owners in light of their personal circumstances and does not address any alternative minimum, state, local or foreign or gift tax considerations.

For purposes of this discussion, a "U.S. holder" is a beneficial owner of a note or a share of common stock received upon conversion of the note that is:

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an individual citizen of the United States or a resident of the United States for U.S. federal income tax purposes;

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a corporation (or any other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States, any state thereof or the District of Columbia;

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an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

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a trust if (1) it is subject to the primary supervision of a court within the United States and one or more United States persons have the authority to control all substantial decisions of the trust or (2) it has a valid election in effect under applicable United States Treasury regulations to be treated as a U.S. person.

For purposes of this discussion, a "non-U.S. holder" is a beneficial owner of a note or share of common stock received upon conversion of the note that is (i) a foreign corporation, (ii) a nonresident alien individual, or (iii) a foreign estate or trust that in either case is not subject to United States federal income tax on a net-income basis on income or gain from a note or share of common stock. Special rules may apply to certain non-U.S. holders such as "controlled foreign corporations," or, in certain circumstances, individuals who are United States expatriates. Such entities should consult their own tax advisors to determine the United States federal, state, local and other tax consequences that may be relevant to them.

If a partnership holds the notes or shares of common stock, the tax treatment of a partner will generally depend upon the status of the partner and the activities of the partnership. A partner of a partnership holding the notes or shares of common stock should consult its own tax advisors.

Prospective investors considering the purchase of notes should consult their own tax advisors concerning the particular U.S. federal income tax consequences to them of the ownership of the notes or shares of common stock in light of their specific situation, as well as the consequences to them arising under the laws of any other taxing jurisdiction.

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U.S. Holders

The following discussion is a summary of certain United States federal income tax considerations applicable to a U.S. holder.

Payment of Interest.    Payments of stated interest on the notes generally will be taxable to a U.S. holder as ordinary income at the time that such payments are received or accrued, in accordance with such U.S. holder's method of accounting for U.S. federal income tax purposes.

This discussion assumes that the notes will not be issued with more than a de minimis amount of original issue discount. If, however, the notes' principal amount exceeds the issue price by more than a de minimis amount, as determined under applicable Treasury regulations, a U.S. holder will be required to include such excess of principal amount over issue price in income as original issue discount, as it accrues, in accordance with a constant-yield method based on a compounding of interest, before the receipt of cash payments attributable to this income.

Additional Interest.    As described under the heading "Description of Notes—Events of Default," we may be required to pay additional interest on the notes in certain circumstances. We intend to take the position that the notes should not be treated as contingent payment debt instruments because of the anticipated remote possibility of such additional payments. Assuming such position is respected, any additional interest paid to a U.S. holder would be taxable as additional ordinary income when received or accrued, in accordance with the U.S. holder's method of accounting for U.S. federal income tax purposes. However, the IRS may take a position contrary to our position, which could materially and adversely affect the timing and character of income with respect to the notes.

Sale, Exchange, or Other Taxable Disposition of Notes, Including a Conversion of the Notes for Cash.    Except as provided below under "—Conversion of Notes into Common Stock" and "—Conversion of Notes into a Combination of Common Stock and Cash," a U.S. holder will generally recognize gain or loss upon the sale, exchange, or other taxable disposition of a note, including a conversion of the note into cash, equal to the difference between the amount realized upon the sale, exchange, or other taxable disposition (less an amount equal to any accrued but unpaid interest, which will be taxable as interest income as discussed above to the extent not previously included in income by the U.S. holder) and the U.S. holder's adjusted U.S. federal income tax basis in the note. A U.S. holder's adjusted tax basis in a note will generally be its cost for that note. Any such gain or loss generally will be capital gain or loss. Capital gains of non-corporate U.S. holders (including individuals) derived in respect of capital assets held for more than one year currently are eligible for reduced rates of taxation. The deductibility of capital losses is subject to limitations under the Code.

Conversion of Notes into Common Stock.    A U.S. holder who receives solely stock and cash in lieu of a fractional share of common stock upon conversion will generally not recognize any gain or loss, except to the extent of cash received in lieu of a fractional share and except to the extent of the fair market value of common stock received with respect to accrued interest, which will be taxable as interest income as discussed above to the extent not previously included in income by the U.S. holder.

A U.S. holder's tax basis in the shares of common stock received upon a conversion (other than common stock attributable to accrued interest, the tax basis of which will equal its fair market

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value) will equal the tax basis in the note that was converted (excluding the portion of the tax basis that is allocable to any fractional share). A U.S. holder's holding period for shares of common stock will include the period during which the U.S. holder held the notes, except that the holding period of any common stock received with respect to accrued interest will commence on the day after the date of receipt.

The amount of gain or loss recognized on the receipt of cash in lieu of a fractional share will be equal to the difference between the amount of cash a U.S. holder receives in respect of the fractional share and the portion of the U.S. holder's tax basis in the note that is allocable to the fractional share. Any gain recognized on conversion generally will be capital gain and will be long-term capital gain if, at the time of the conversion, the note has been held for more than one year.

Conversion of Notes into a Combination of Common Stock and Cash.    If a combination of cash and common stock is received in exchange for a U.S. holder's notes upon conversion, we intend to take the position that the conversion should be treated as a recapitalization. In this case, gain, but not loss, will be recognized in an amount equal to the excess of the fair market value of the common stock and cash received (other than amounts attributable to accrued interest, which will be taxable as interest income as discussed above to the extent not previously included in income by the U.S. holder) over the U.S. holder's tax basis in the note, but such gain will only be recognized to the extent of such cash received (excluding cash attributable to accrued interest or received in lieu of a fractional share).

The amount of gain or loss recognized on the receipt of cash in lieu of a fractional share will be equal to the difference between the amount of cash a U.S. holder receives in respect of the fractional share and the portion of the U.S. holder's tax basis in the note that is allocable to the fractional share. Any gain recognized on conversion generally will be capital gain and will be long-term capital gain if, at the time of the conversion, the note has been held for more than one year.

The tax basis in the shares of common stock received upon a conversion (other than common stock attributable to accrued interest, the tax basis of which will equal its fair market value) will equal the tax basis in the note that was converted (excluding the portion of the tax basis that is allocable to any fractional share), reduced by the amount of any cash received (other than cash received in lieu of a fractional share and cash attributable to accrued interest), and increased by the amount of gain, if any, recognized (other than with respect to a fractional share). A U.S. holder's holding period for shares of common stock will include the period during which the U.S. holder held the notes except that the holding period of any common stock received with respect to accrued interest will commence on the day after the date of receipt.

Alternative treatments of the conversion of the notes into cash and common stock are possible. For example, the conversion of a note into cash and common stock may instead be treated for United States federal income tax purposes as in part a conversion into stock and in part a payment in redemption of a portion of the note. U.S. holders should consult their tax advisors regarding the tax treatment of the receipt of cash and stock in exchange for notes upon conversion or repurchase, including any alternative treatments.

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If a U.S. holder surrenders notes for conversion and such notes are exchanged with an entity other than us, the U.S. holder will be required to recognize gain or loss as described under "—Sale, Exchange, or Other Taxable Disposition of Notes, Including a Conversion of the Notes for Cash." In such case, the U.S. holder's tax basis in the common stock received will equal the fair market value of the stock on the date of the exchange, and the U.S. holder's holding period in the common stock received will begin on the day after the date of the exchange.

Constructive Distribution.    The conversion rate of the notes will be adjusted in certain circumstances, including upon the payment of certain cash dividends. Under Section 305(c) of the Code, adjustments (or failures to make adjustments) that have the effect of increasing a U.S. holder's proportionate interest in our assets or earnings may in some circumstances result in a deemed distribution. Certain adjustments to the conversion rate made pursuant to a bona fide reasonable adjustment formula that have the effect of preventing the dilution of the interest of the beneficial owners of the notes, however, will generally not be considered to result in a deemed distribution. Certain of the possible conversion rate adjustments provided in the notes (including, without limitation, upon the payments of cash dividends to holders of common stock) will not qualify as being pursuant to a bona fide reasonable adjustment formula. If such adjustments are made, a U.S. holder may be deemed to have received a distribution even though it has not received any cash or property because of such adjustments. In addition, a failure to adjust (or to adjust adequately) the conversion rate after an event that increases a U.S. holder's proportionate interest could be treated as a deemed taxable dividend. Other increases in the conversion rate of the notes (including an adjustment to the conversion rate in connection with a make-whole fundamental change) may, depending on the circumstances, be a deemed distribution. Any deemed distribution would be taxable as a dividend, return of capital, or capital gain in accordance with the earnings and profits rules under the Code. It is not clear whether a constructive dividend deemed paid would be eligible for the preferential rates of U.S. federal income tax applicable to certain dividends paid to non-corporate beneficial owners. It is also not clear whether corporate beneficial owners would be entitled to claim the dividends-received deduction with respect to any such constructive dividends.

Common Stock.    Distributions, if any, made on our common stock generally will be included in a U.S. holder's income as ordinary dividend income to the extent of our current or accumulated earnings and profits. However, for individual U.S. holders, such dividends currently are generally taxed at the lower applicable long-term capital gains rates, provided certain holding period and other requirements are satisfied. Distributions in excess of our current and accumulated earnings and profits will be treated as a return of capital to the extent of a U.S. holder's tax basis in the common stock and thereafter as capital gain from the sale or exchange of such common stock. For corporate U.S. holders, dividends received may be eligible for the dividends-received deduction, subject to applicable limitations.

Upon the sale or exchange or other taxable disposition of our common stock (including certain redemptions), a U.S. holder generally will recognize capital gain or loss equal to the difference between (i) the amount of cash and the fair market value of any property received upon such taxable disposition and (ii) the U.S. holder's tax basis in the common stock. Such capital gain or loss will be long-term capital gain or loss if a U.S. holder's holding period in the common stock is more than one year at the time of the taxable disposition. The deductibility of capital losses is subject to certain limits under the Code.

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Unearned Income Medicare Contribution Tax.    Certain U.S. holders who are individuals, estates or trusts will be required to pay an additional 3.8% tax on, among other things, interest and dividends and capital gains from the sale, exchange, redemption, retirement or other taxable disposition of notes and our common stock.

Information Reporting and Backup Withholding.    Information reporting requirements generally will apply to payments of interest on the notes and to the proceeds of a sale of a note unless a U.S. holder is an exempt recipient, such as a corporation. Backup withholding will apply to those payments if a U.S. holder fails to provide its correct taxpayer identification number and certification of exempt status, or fails to report in full interest and dividend income. Any amounts withheld under the backup withholding rules will be allowed as a refund or a credit against U.S. federal income tax liability, provided the required information is timely furnished to IRS.

Non-U.S. Holders

The following is a summary of the United States federal income tax considerations applicable to a non-U.S. holder (as defined above) of notes or shares of common stock.

Payments of Interest.    The gross amount of payments to a non-U.S. holder of interest that does not qualify for the portfolio interest exemption and that is not effectively connected with the conduct by such non-U.S. holder of a trade or business within the United States (or, if required by an applicable income tax treaty, is not attributable to a permanent establishment of such non-U.S. holder in the United States) will be subject to U.S. withholding tax at the rate of 30%, unless a U.S. income tax treaty applies to reduce or eliminate such withholding tax. The 30% United States federal withholding tax will not apply to any payment to a non-U.S. holder of interest on a note under the "portfolio interest exemption" provided the non-U.S. holder:

•

does not actually (or constructively) own 10% or more of the total combined voting power of all of our stock entitled to vote;

•

is not a "controlled foreign corporation" with respect to which we are a "related person" within the meaning of the Code; and

•

either (1) provides the non-U.S. holder's name and address on an IRS Form W-8BEN (or other applicable or successor form), and certifies under penalties of perjury that it is not a U.S. person or (2) owns through a securities clearing organization, bank or other financial institution that holds customers' securities in the ordinary course of its trade or business, under penalties of perjury, that such a form has been received from the non-U.S. holder by it or by a financial institution between it and the non-U.S. holder.

If a non-U.S. holder is engaged in a trade or business in the United States and interest paid on the note constitutes income that is effectively connected with the conduct of that trade or business (and, if required by an applicable income tax treaty, is attributable to a permanent establishment of that non-U.S. holder), or U.S. Trade or Business Income, such interest will be taxed on a net basis at regular graduated U.S. income tax rates rather than the 30% gross rate. In the case of a non-U.S. holder that is a corporation, such U.S. Trade or Business Income may also be subject to the branch profits tax at a 30% rate (or lower applicable income tax treaty rate).

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To claim the benefit of a tax treaty exemption from or reduction in withholding, or to claim exemption from withholding because the income is U.S. Trade or Business Income, a non-U.S. holder must provide a properly executed IRS Form W-8BEN or W-8ECI (or such successor forms as the IRS designates), as applicable. The non-U.S. holder must provide the form to its withholding agent. These forms must be periodically updated. A non-U.S. holder who is claiming the benefits of a treaty may be required in certain instances to obtain a U.S. taxpayer identification number and to provide certain documentary evidence issued by foreign governmental authorities to prove residence in the foreign country.

Dividends and Constructive Dividends.    Any dividends paid to a non-U.S. holder with respect to shares of our common stock (and any deemed dividends resulting from certain adjustments, or failure to make adjustments, to the conversion rate including, without limitation, for cash dividends paid to holders of our common stock, see "—U.S. Holders—Constructive Distribution" above) will be subject to withholding tax at a 30% rate (or lower applicable treaty rate). Because any constructive dividend a non-U.S. holder is deemed to receive would not give rise to any cash from which any applicable withholding tax could be satisfied, it is possible that this tax would be withheld from any amount owed to the non-U.S. holder, including, but not limited to, interest payments, cash or shares of common stock otherwise due on conversion, dividends or sales proceeds subsequently paid or credited to the non-U.S. holder. Dividends and constructive dividends that constitute U.S. Trade or Business Income are attributable to a United States permanent establishment, are not subject to the withholding tax, but instead are subject to United States federal income tax on a net income basis at applicable graduated individual or corporate rates. Certain certification requirements and disclosure requirements must be complied with in order for effectively connected income to be exempt from withholding. Any such effectively connected income received by a foreign corporation may, under certain circumstances, be subject to an additional branch profits tax at a 30% rate (or lower applicable income tax treaty rate).

A non-U.S. holder of shares of our common stock who wishes to claim the benefit of an applicable treaty rate is required to satisfy applicable certification and other requirements. Non-U.S. holders eligible for a reduced rate of United States withholding tax pursuant to an income tax treaty may obtain a refund of any excess amounts withheld by filing an appropriate claim for refund with the IRS.

Sale, Exchange, Conversion or Other Disposition of Notes or Shares of Common Stock.    A non-U.S. holder will recognize gain on the sale, exchange, or other taxable disposition of notes or shares of common stock, including a conversion of notes into cash or into a combination of cash and stock. Nevertheless, such gain generally will not be subject to U.S. federal income tax unless:

•

such gain is U.S. Trade or Business Income;

•

in the case of any gain realized by an individual non-U.S. holder, such non-U.S. holder is present in the United States for 183 days or more in the taxable year of such sale, exchange, retirement, conversion, or other disposition and certain other conditions are met; or

•

we are or have been a "United States real property holding corporation" for United States federal income tax purposes during the shorter of the non-U.S. holder's holding period and the five-year period ending on the date of such sale, exchange, retirement, conversion or other disposition.

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An individual non-U.S. holder described in the first bullet point above will be subject to tax on the net gain derived from the sale, exchange, conversion or other taxable disposition under regular graduated United States federal income tax rates. An individual non-U.S. holder described in the second bullet point above will be subject to a flat 30% tax on the gain derived from the sale, exchange, conversion or other taxable disposition, which may be offset by U.S. source capital losses, even though such non-U.S. holder is not considered a resident of the United States. A corporate non-U.S. holder that falls under the first bullet point above will be subject to tax on any net gain in the same manner as if such non-U.S. holder was a United States person as defined under the Code and, in addition, may be subject to the branch profits tax equal to 30% of such non-U.S. holder's U.S. Trade or Business Income or at such lower rate as may be specified by an applicable income tax treaty.

We believe that we are not, and do not anticipate becoming, a "United States real property holding corporation" for United States federal income tax purposes.

Any stock that a non-U.S. holder receives on the sale, exchange, conversion or other disposition of a note that is attributable to accrued interest will not give rise to gain, as described above, but will instead generally be subject to United Stated federal income tax in accordance with the rules for taxation of interest described above under "—Payments of Interest."

Information Reporting and Backup Withholding.    The amount of interest and dividends paid (including dividends deemed paid) and the amount of tax, if any, withheld with respect to those payments will be reported to the non-U.S. holder and the IRS. Copies of the information returns reporting such interest and dividend payments and any withholding may also be made available to the tax authorities in the country in which a non-U.S. holder resides, under the provisions of an applicable income tax treaty.

In general, a non-U.S. holder will not be subject to backup withholding with respect to payments of interest or dividends, provided that the withholding agent does not have actual knowledge or reason to know that such non-U.S. holder is a United States person, as defined under the Code, and has received the statement described above in the third bullet point under "—Payments of Interest." In addition, information returns will not be filed with the IRS in connection with the payment of proceeds from a sale or other disposition of the notes or the shares of our common stock unless paid within the United States or through certain U.S.-related payors and, unless the withholding agent has not received the statement described above in the third bullet point under "—Payments of Interest," a non-U.S. holder may also be subject to U.S. backup withholding on such proceeds.

Any amounts withheld under the backup withholding rules will be allowed as a refund or a credit against a non-U.S. holder's U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Withholding on Foreign Accounts.    Legislation known as the Foreign Account Tax Compliance Act ("FATCA") and guidance issued thereunder imposes withholding taxes on certain types of payments made to "foreign financial institutions" and certain other non-U.S. entities (including financial intermediaries). FATCA imposes a 30% withholding tax on certain payments of interest, dividends, or gross proceeds from the sale or other disposition of common stock or notes paid to a foreign financial institution or to certain non-financial foreign entities unless certain certification, information reporting and other specified requirements are met or an

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exemption applies. Under transition rules, any obligation to withhold under the legislation will not begin, with respect to payments of interest on the notes and payments of dividends on the common stock, until July 1, 2014 and, with respect to the gross proceeds of a sale or other disposition of the notes or common stock, until January 1, 2017. Additionally, this legislation does not apply to "grandfathered obligations" that are outstanding on July 1, 2014. We anticipate that the notes will qualify as "grandfathered obligations" so long as there is not a material modification of the notes on or after July 1, 2014 that would cause the notes to be treated as reissued. This exemption does not apply to shares of our common stock. Prospective investors should consult their tax advisors regarding FATCA.

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Underwriting

We will enter into an underwriting agreement with J.P. Morgan Securities LLC, as representative of the several underwriters listed in the table below. Pursuant to the terms and conditions of the underwriting agreement, we have agreed to sell to the underwriters, and each underwriter has severally agreed to purchase from us, the principal amount of notes set forth opposite its name below:

The underwriting agreement provides that the underwriters are obligated to purchase all of the notes if any are purchased. The underwriting agreement also provides that if an underwriter defaults, the purchase commitments of non-defaulting underwriters may also be increased or the offering terminated. The obligations of the underwriters under the underwriting agreement are subject to the satisfaction of certain conditions.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters initially propose to offer the notes to the public at the public offering price that appears on the cover page of this prospectus supplement. The underwriters may offer the notes to selected dealers at the public offering price minus a concession of up to       % of the principal amount. In addition, the underwriters may allow, and those selected dealers may reallow, a concession of up to       % of the principal amount to certain other dealers. After the initial offering, the underwriters may change the public offering price and any other selling terms. The underwriters may offer and sell notes through certain of their affiliates.

The following table shows the underwriting discounts and commissions to be paid to the underwriters by us in connection with this offering, assuming both no exercise and full exercise of the underwriters' over-allotment option described below.

Paid by us

We estimate that the expenses for this offering payable by us (other than discounts and commissions set forth in the table above) will be approximately $       . We have agreed to reimburse the underwriters for expenses relating to qualification of this offering with FINRA up to $10,000.

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A prospectus in electronic format may be made available on the web sites maintained by one or more underwriters, or selling group members, if any, participating in the offering. The underwriters may agree to allocate a number of shares to underwriters and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the representatives to underwriters and selling group members that may make Internet distributions on the same basis as other allocations.

Option to purchase additional notes

We have granted the underwriters the right to purchase, exercisable within a 30-day period from the date of this prospectus supplement, up to an additional $22,500,000 principal amount of notes from us solely to cover over-allotments. If any additional notes are purchased with this option, the underwriters will offer such additional notes on the same terms as those on which the notes are being offered.

New issue of notes

The notes are a new issue of securities, and there is currently no established trading market for such notes. We do not intend to apply for the notes to be listed on any securities exchange or to arrange for the notes to be quoted on any quotation system.

The underwriters have advised us that they intend to make a market in the notes, but they are not obligated to do so. The underwriters may discontinue any market-making in the notes at any time in their sole discretion without notice. Accordingly, we cannot assure you that a liquid trading market will develop for the notes. If an active trading market for the notes does not develop, the market price and liquidity of the notes may be adversely affected. If the notes are traded, they may trade at a discount from their initial public offering price depending on prevailing interest rates, the market for similar securities, our performance and other factors.

No sale of similar securities

We and our directors and certain of our executive officers have agreed that, for a period of 90 days from the date of this prospectus supplement, neither we nor they will, without the prior consent of J.P. Morgan Securities LLC, sell or pledge (or, in the case of our directors and such certain of our executive officers, offer or enter into any agreement to offer or sell), directly or indirectly, any shares of common stock or any securities convertible into, or exercisable or exchangeable for, shares of common stock, enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the common stock or such other securities, or file or participate in the filing of a registration statement with the SEC in respect of such common stock or securities (or, in the case of our directors and such certain executive officers, publicly announce an intention to effect one of these transactions).

Notwithstanding the above, the underwriters have agreed in the underwriting agreement that the lock-up restrictions applicable to us do not apply to (i) the sale of the securities in this offering, or the issuance by us of any shares of our common stock upon the conversion thereof; (ii) the issuance by us of any shares of our common stock upon the exercise of an option, warrant or the conversion of a security outstanding on the date hereof or under any employee benefit plans existing on the date hereof in each case as described in this prospectus

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supplement or the documents incorporated by reference herein; (iii) the vesting of or removal or lapse of restrictions on options, restricted stock or other awards under our employee benefits plans or agreements in accordance with the terms of such plans or agreements; (iv) the issuance by us of any options, restricted stock and other awards granted under, or any shares of our common stock issued upon the exercise of options granted under, existing employee benefits plans described herein or in the documents incorporated by reference herein; (v) the filing of any registration statement in respect of securities offered pursuant to the terms of our existing employee benefits plans or agreements; (vi) our issuance of options, restricted stock or other awards to newly hired employees, provided such awards do not vest or are not exercisable during the lock-up period and (vii) our entry into the warrant transactions described in this prospectus supplement and the performance of our obligations thereunder.

In addition, notwithstanding the lock-up agreements applicable to our directors and certain of our executive officers, the underwriters have agreed that the lock-up restrictions applicable to such directors and such certain executive officers do not apply to: (i) the receipt, exercise, cashless or net exercise, vesting or forfeiture of, or removal or lapse of restrictions on, any stock option, common stock issued upon exercise of a stock option, restricted stock or other awards pursuant to any employee benefit plan or agreement in existence as of the date of the applicable lock-up agreement, so long as such transaction or event does not involve the sale or transfer of any shares of common stock (other than from such director or executive officer to us; (ii) forfeitures of securities to us during the lock-up period only to satisfy tax withholding requirements; (iii) transfers of securities as a bona fide gift or gifts; (iv) the transfer or sale of our common stock acquired in open market transactions on or after the date of the prospectus supplement; (v) the transfer or sale of our securities by operation of law, such as pursuant to a domestic relations order or in connection with a divorce settlement; (vi) transfers of our securities to any immediate family member, trusts for the direct or indirect benefit of such director or executive officer or the immediate family members of such director or executive officer or any of their successors upon death, or any partnerships or limited liability company, the partners or members of which consist of such director or executive officer and/or immediate family members of such director or executive officer, and in each case such transfer does not involve a disposition for value; (vii) transfers of our securities to any beneficiary of such director or executive officer pursuant to a will, other testamentary document or applicable laws of descent and, with respect to one of our executive officers (viii) transfers and sales not otherwise permitted by one or more of clauses (i) through (vii) by such executive officer in an aggregate amount not to exceed 2,084 shares of our common stock; provided that in the case of any transfer or distribution pursuant to clauses (iii), (v), (vi) or (vii), each donee, distributee or transferee shall agree to be bound by the lock-up restrictions; and provided, further, that in the case of any transfer or distribution pursuant to clause (iii), (v), (vi) or (vii), no filing by any party (donor, donee, transferor or transferee) under the Exchange Act, or other public announcement (other than a filing on a Form 5 made after the expiration of the lock-up period) reporting a reduction in beneficial ownership of our securities shall be required or shall be made voluntarily in connection with such transfer or distribution. The underwriters have also agreed that such directors and executive officers may enter into any contract, instruction or plan complying with Rule 10b5-1 of the Exchange Act, so long as no party shall be required to, nor shall it voluntarily, file a report under the Exchange Act or otherwise voluntarily effect any public filing, report or announcement of such entry and no transfer or sale under such a plan occurs during the lock-up period. In addition, certain of our directors and executive

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officers have established trading plans pursuant to Rule 10b5-1 and may sell, pledge, transfer or otherwise dispose, directly or indirectly, shares of our common stock pursuant to such plans during the lock-up period. Should sales be made by such directors and executive officers pursuant to these trading plans, reports on Form 4 will be filed with the SEC, if required by law.

In addition, each of our directors and our executive officers has agreed that, without the prior written consent of J.P. Morgan Securities LLC, he or she will not, during the period commencing on the date of his or her lock-up agreement and ending 90 days after the date of this prospectus supplement, make any demand for, or exercise any right with respect to, the registration of any shares of our common stock or any security convertible into or exercisable or exchangeable for shares of our common stock. J.P. Morgan Securities LLC, in its sole discretion, may release any of the securities subject to this lock-up agreement at any time without notice.

Price stabilization and short positions; purchase of common stock

In connection with the offering of the notes, the underwriters may engage in over-allotment, stabilizing transactions and syndicate covering transactions in the notes and our common stock. Over-allotment involves sales in excess of the offering size, which creates a short position for the underwriters. Stabilizing transactions involve bids to purchase the notes or our common stock in the open market for the purpose of pegging, fixing or maintaining the price of the notes. Syndicate covering transactions involve purchases of the notes or our common stock in the open market after the distribution has been completed in order to cover short positions. Stabilizing transactions and syndicate covering transactions may cause the price of the notes or our common stock to be higher than it would otherwise be in the absence of those transactions.

These acquisitions could have the effect of raising or maintaining the market price of our common stock above levels that would otherwise have prevailed, or preventing or retarding a decline in the market price of our common stock. See "Use of proceeds."

In addition, in connection with this offering certain of the underwriters (and selling group members) may engage in passive market making transactions in our common stock on The Nasdaq Global Select Market prior to the pricing and completion of this offering. Passive market making consists of displaying bids on The Nasdaq Global Select Market no higher than the bid prices of independent market makers and making purchases at prices no higher than these independent bids and effected in response to order flow. Net purchases by a passive market maker on each day are generally limited to a specified percentage of the passive market maker's average daily trading volume in the common stock during a specified period and must be discontinued when such limit is reached. Passive market making may cause the price of our common stock to be higher than the price that otherwise would exist in the open market in the absence of these transactions. If passive market making is commenced, it may be discontinued at any time.

Convertible note hedge and warrant transactions

In connection with the pricing of the notes, we expect to enter into convertible note hedge transactions with the option counterparties. The convertible note hedge transactions are

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expected to reduce the potential dilution to our common stock and/or offset cash payments due upon conversion the of notes. We also expect to enter into warrant transactions with the option counterparties. However, the warrant transactions could separately have a dilutive effect on our earnings per share to the extent that the market price per share of our common stock exceeds the applicable strike price of the warrants. If the underwriters exercise their over-allotment option, we may enter into additional convertible note hedge transactions and additional warrant transactions.

We intend to use approximately $        million of the net proceeds from this offering to pay the cost of the convertible note hedge transactions (after such cost is partially offset by the proceeds to us from the sale of the warrant transactions). If the underwriters exercise their over-allotment option, we may sell additional warrants and use a portion of the proceeds from the sale of the additional notes, together with the proceeds from the sale of the additional warrants, to enter into additional convertible note hedge transactions.

In connection with establishing their initial hedge of the convertible note hedge and warrant transactions, the option counterparties or their affiliates have advised us that they expect to enter into various derivative transactions with respect to our common stock concurrently with or shortly after the pricing of the notes. This activity could increase (or reduce the size of any decrease in) the market price of our common stock or the notes at that time.

In addition, the option counterparties or their affiliates may modify their hedge positions by entering into or unwinding various derivatives with respect to our common stock and/or purchasing or selling our common stock or other securities of ours in secondary market transactions following the pricing of the notes and prior to the maturity of the notes (and are likely to do so during any observation period related to a conversion of notes). This activity could also cause or avoid an increase or a decrease in the market price of our common stock or the notes, which could affect your ability to convert the notes and, to the extent the activity occurs during any observation period related to a conversion of notes, it could affect the number of shares and value of the consideration that you will receive upon conversion of the notes.

For a discussion of the potential impact of any market or other activity by the option counterparties or their affiliates in connection with these convertible note hedge and warrant transactions, see "Risk factors—Risks related to the notes—The convertible note hedge and warrant transactions may affect the value of the notes and our common stock."

Foreign jurisdictions

Other than in the United States, no action has been taken by us or the underwriters that would permit a public offering of the securities offered by this prospectus supplement in any jurisdiction where action for that purpose is required. The securities offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement. This prospectus supplement does not constitute an

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offer to sell or a solicitation of an offer to buy any securities offered by this prospectus supplement in any jurisdiction in which such an offer or a solicitation is unlawful.

Notice to Prospective Investors in the European Economic Area

In relation to each Member State of the European Economic Area (each, a "Relevant Member State"), no offer of notes may be made to the public in that Relevant Member State other than:

A.

to any legal entity which is a qualified investor as defined in the Prospectus Directive;



B.

to fewer than 100 or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150, natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the representatives; or



C.

in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of notes shall require the Company or the representatives to publish a prospectus pursuant to Article 3 of the Prospectus Directive or supplement a prospectus pursuant to Article 16 of the Prospectus Directive.

Each person in a Relevant Member State who initially acquires any notes or to whom any offer is made will be deemed to have represented, acknowledged and agreed that it is a "qualified investor" within the meaning of the law in that Relevant Member State implementing Article 2(1)(e) of the Prospectus Directive. In the case of any notes being offered to a financial intermediary as that term is used in Article 3(2) of the Prospectus Directive, each such financial intermediary will be deemed to have represented, acknowledged and agreed that the notes acquired by it in the offer have not been acquired on a non-discretionary basis on behalf of, nor have they been acquired with a view to their offer or resale to, persons in circumstances which may give rise to an offer of any notes to the public other than their offer or resale in a Relevant Member State to qualified investors as so defined or in circumstances in which the prior consent of the representatives has been obtained to each such proposed offer or resale.

This prospectus has been prepared on the basis that any offer of notes in any Relevant Member State will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus for offers of notes. Accordingly any person making or intending to make an offer in that Relevant Member State of notes which are the subject of the offering contemplated in this prospectus may only do so in circumstances in which no obligation arises for the Company or any of the underwriters to publish a prospectus pursuant to Article 3 of the Prospectus Directive in relation to such offer. Neither the Company nor the underwriters have authorized, nor do they authorize, the making of any offer of notes in circumstances in which an obligation arises for the Company or the underwriters to publish a prospectus for such offer.

For the purpose of the above provisions, the expression "an offer to the public" in relation to any notes in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the notes to be offered so as to enable an investor to decide to purchase or subscribe the notes, as the same may be varied in the Relevant Member State by any measure implementing the Prospectus Directive in the Relevant Member State and the expression "Prospectus Directive" means Directive 2003/71/EC

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(including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member States) and includes any relevant implementing measure in the Relevant Member State and the expression "2010 PD Amending Directive" means Directive 2010/73/EU.

Notice to Prospective Investors in the United Kingdom

In addition, in the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are "qualified investors" (as defined in the Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the "Order") and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as "relevant persons"). This document must not be acted on or relied on in the United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons.

Notice to Prospective Investors in Switzerland

The notes may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange ("SIX") or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the notes or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, the Company, or the notes have been or will be filed with or approved by any Swiss regulatory authority. In particular, this document will not be filed with, and the offer of notes will not be supervised by, the Swiss Financial Market Supervisory Authority FINMA (FINMA), and the offer of notes has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes ("CISA"). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of notes.

Notice to Prospective Investors in the Dubai International Financial Centre

This prospectus relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority ("DFSA"). This prospectus is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus nor taken steps to verify the information set forth herein and has no responsibility for the prospectus. The notes to which this prospectus relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the notes offered should conduct their own due diligence on the notes. If you do not understand the contents of this prospectus you should consult an authorized financial advisor.

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Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission ("ASIC"), in relation to the offering. This prospectus does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the "Corporations Act"), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the notes may only be made to persons (the "Exempt Investors") who are "sophisticated investors" (within the meaning of section 708(8) of the Corporations Act), "professional investors" (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the notes without disclosure to investors under Chapter 6D of the Corporations Act.

The notes applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring notes must observe such Australian on-sale restrictions.

This prospectus contains general information only and does not take account of the investment objectives, financial situation or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in Hong Kong

The notes have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to "professional investors" as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a "prospectus" as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the notes has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to notes which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

Notice to Prospective Investors in Japan

The notes have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) and, accordingly, will not be offered

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or sold, directly or indirectly, in Japan, or for the benefit of any Japanese Person or to others for re-offering or resale, directly or indirectly, in Japan or to any Japanese Person, except in compliance with all applicable laws, regulations and ministerial guidelines promulgated by relevant Japanese governmental or regulatory authorities in effect at the relevant time. For the purposes of this paragraph, "Japanese Person" shall mean any person resident in Japan, including any corporation or other entity organized under the laws of Japan.

Notice to Prospective Investors in Singapore

This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of notes may not be circulated or distributed, nor may the notes be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the "SFA"), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275, of the SFA, or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the notes are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

(a)

a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or



(b)

a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries' rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the notes pursuant to an offer made under Section 275 of the SFA except:

(c)

to an institutional investor or to a relevant person defined in Section 275(2) of the SFA, or to any person arising from an offer referred to in Section 275(1A) or Section 276(4)(i)(B) of the SFA;



(d)

where no consideration is or will be given for the transfer;



(e)

where the transfer is by operation of law;



(f)

as specified in Section 276(7) of the SFA; or



(g)

as specified in Regulation 32 of the Securities and Futures (Offers of Investments) (Shares and Debentures) Regulations 2005 of Singapore.

You should be aware that the laws and practices of certain countries require investors to pay stamp taxes and other charges in connection with purchases of securities.

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Other relationships

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include sales and trading, commercial and investment banking, advisory, investment management, investment research, principal investment, hedging, market making, brokerage and other financial and non-financial activities and services. Certain of the underwriters and their respective affiliates have provided in the past and may provide from time to time in the future certain commercial banking, financial advisory, investment banking and other services for us and our affiliates in the ordinary course of their business, for which they have received and may continue to receive customary fees and commissions.

In addition, from time to time, the underwriters and their respective affiliates may effect transactions for their own account or the account of customers, and hold on behalf of themselves or their customers, long or short positions in our debt or equity securities or loans, and may do so in the future. For example, J.P. Morgan Securities LLC and its affiliates beneficially own in excess of 5% of our outstanding equity securities, almost all of which are held in a fiduciary capacity for the benefit of others.

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Legal matters

Certain legal matters relating to the notes offered hereby will be passed upon for us by Goodwin Procter LLP, Boston, Massachusetts. Certain legal matters will be passed upon for the underwriters by Davis Polk & Wardwell LLP, New York, New York.

Experts

The financial statements and management's assessment of the effectiveness of internal control over financial reporting (which is included in "Management's Annual Report on Internal Control over Financial Reporting") incorporated in this prospectus supplement by reference to our Annual Report on Form 10-K for the year ended December 31, 2013 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

Where you can find more information

We file reports, proxy statements and other information with the SEC. You may read and copy the reports, proxy statements and other information that we file with the SEC at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for information about the operation of its Public Reference Room and for its prescribed rates to obtain copies of such material. The SEC also maintains an Internet site that contains reports, proxy and information statements and other information regarding registrants, like us, that file electronically with the SEC. The address of the SEC's Internet site is http://www.sec.gov.

Our Internet site is http://www.amagpharma.com. Information contained on our Internet site is not a part of this prospectus. We make our annual reports, quarterly reports, current reports and proxy statements available free of charge on our website as soon as reasonably practicable after we file these reports with the SEC. Information contained on our website is not a part of this prospectus supplement, expect as explicitly incorporated by reference in "Incorporation of documents by reference."

This registration statement of which this prospectus supplement is a part, including the exhibits contained or incorporated by reference therein, can be read at the SEC web site or at the SEC office referred to above. Any statement made or incorporated by reference in this prospectus supplement concerning the contents of any contract, agreement or other document is only a summary of the actual contract, agreement or other document. If we have filed any contract, agreement or other document as an exhibit to the registration statement or incorporated any contract, agreement or other document into this prospectus supplement, you should read such contract, agreement or other document, as the case may be, for a more complete understanding of the document or matter involved. Each statement regarding a contract, agreement or other document is qualified in its entirety by reference to the actual document.

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Incorporation of documents by reference

We incorporate by reference into this prospectus supplement the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including any filings after the date of this prospectus supplement, other than any information furnished in any such current report on Form 8-K that we filed or may file with the SEC under Items 2.02 or 7.01 or exhibits furnished on such form that relate to such items, until we have sold all of the notes to which this prospectus supplement relates or the offering is otherwise terminated. The information incorporated by reference is an important part of this prospectus supplement. Any statement in a document incorporated by reference into this prospectus supplement will be deemed to be modified or superseded to the extent a statement contained in (1) this prospectus supplement or (2) any other subsequently filed document that is incorporated by reference into this prospectus supplement, modifies or supersedes such statement.

•

Our Annual Report on Form 10-K for the fiscal year ended December 31, 2013;

•

Our annual Proxy Statement on Schedule 14A relating to our annual meeting of stockholders, filed with the SEC on April 19, 2013 (with respect to those portions incorporated by reference into our Annual Report on Form 10-K for the year ended December 31, 2012);

•

Our Current Reports on Form 8-K as filed on January 8, 2014 and January 22, 2014;

•

The description of our common stock, which is registered under Section 12 of the Exchange Act, contained under Item 8.01 of our Current Report on Form 8-K, as filed on August 1, 2013, including any amendment or report filed for the purpose of updating such descriptions; and

•

The description of our Series A Junior Participating Preferred Stock Purchase Rights, or the rights, contained under Item 3.03 of our Current Report on Form 8-K, as filed on September 4, 2009, in our registration statement on Form 8-A registering the rights under Section 12 of the Exchange Act, filed with the SEC on September 4, 2009, including any amendments or reports filed for the purpose of updating that description.

We will provide, without charge, to each person, including any beneficial owner, to whom a copy of this prospectus supplement is delivered, upon the written or oral request of such person, a copy of any or all of the documents that have been incorporated herein by reference, but are not delivered with this prospectus supplement, other than exhibits to such documents (unless such exhibits are specifically incorporated by reference therein). Requests for these copies should be directed to our investor relations department at the following address and telephone number: AMAG Pharmaceuticals, Inc., 1100 Winter Street, Waltham, Massachusetts, 02451; (617) 498-3300.

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PROSPECTUS

$250,000,000

Common Stock
Preferred Stock
Debt Securities
Warrants
Depositary Shares
Stock Purchase Units or Contracts
Subscription Rights
Units

        We may offer and sell, from time to time, in one or more offerings, up to $250,000,000 of our common stock, preferred stock, debt securities, warrants, depositary shares, stock purchase units or contracts, subscription rights or units described in this prospectus, either separately or together with other securities described in this prospectus.

        Each time securities are offered pursuant to this prospectus, we will indicate the particular securities we offer and their specific terms in a supplement to this prospectus. In each case we will describe the type and amount of securities we are offering, the initial public offering price, the net proceeds we expect to receive and the other terms of the offering.

        The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled "Plan of Distribution" in this prospectus and in the applicable prospectus supplement.

        Our common stock is listed on the NASDAQ Global Select Market under the symbol "AMAG." On November 6, 2013, the last reported sale price of our common stock on the NASDAQ Global Select Market was $24.38 per share.

        Investing in our securities involves risks. You should review carefully the risks and uncertainties described under the heading "Risk Factors" beginning on page 3 and contained in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference herein.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or the accuracy of this prospectus. Any representation to the contrary is a criminal offense.

        Our principal executive office is at 1100 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (617) 498-3300.

The date of this prospectus is November 18, 2013.

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ABOUT THIS PROSPECTUS

        This prospectus is part of a registration statement we filed with the Securities and Exchange Commission, or the SEC, using a "shelf" registration process. Under this shelf process, we may sell any combination of the securities described in this prospectus from time to time in one or more offerings up to a total dollar amount of $250,000,000.

        This prospectus provides you only with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement containing specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. We may also add, update or change in the prospectus supplement (and in any related free writing prospectus that we may authorize to be provided to you) any of the information contained in this prospectus or in the documents that we have incorporated by reference into this prospectus. You should read both this prospectus and any prospectus supplement or related free writing prospectus together with additional information described under the headings "Where You Can Find More Information" and "Documents Incorporated By Reference."

        You should rely only on the information incorporated by reference or provided in this document. We have not authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We will not make an offer of these securities in any jurisdiction where it is unlawful. You should assume that the information in this prospectus, as well as the information we have previously filed with the SEC and incorporated by reference in this prospectus, is accurate only as of the date of the documents containing the information.

        References in this prospectus to the terms "AMAG Pharmaceuticals," "company," "we," "our" or "us" or other similar terms means AMAG Pharmaceuticals, Inc.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

        Any statements in this prospectus or the applicable prospectus supplement or free writing prospectus, including the documents that we incorporate by reference herein, about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or the "Securities Act," and Section 21E of the Securities Exchange Act of 1934, as amended, or the "Exchange Act." You can identify these forward-looking statements by the use of words or phrases such as "believe," "may," "could," "will," "estimate," "continue," "anticipate," "intend," "seek," "plan," "expect," "potential," "predict," "project," "should," or "would." Among the factors that could cause actual results to differ materially from those indicated in the forward-looking statements are risks and uncertainties inherent in our business including, without limitation, our plan to grow Feraheme in the U.S. chronic kidney disease market and through international and label expansion; the expansion of our portfolio through the in-license or purchase of additional specialty pharmaceutical products; expectations regarding our supplemental New Drug Application for Feraheme; the timing of the response from the EMA and Health Canada regarding Takeda Pharmaceutical Company Limited's Type II variation and Supplemental New Drug Submission, respectively; our expectations regarding the timing for enrollment in and commencement of our pediatric study and post-approval trials; our plans for a post-approval trial to assess the safety and efficacy of repeat doses of Feraheme for the treatment of iron deficiency anemia; our expectation that 3SBio, Inc. will begin a clinical trial if approved by the Chinese State Food and Drug Administration; our expectation of costs to be incurred in connection with and revenue sources to fund our future operations; our expectation for the patient population for Feraheme in the U.S.; our expectations regarding the success of our collaboration with Takeda Pharmaceutical Company Limited, including any potential milestone

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payments, product sales or royalties we may receive; our expectations regarding the manufacture of all Feraheme/Rienso drug substance and drug product at our third-party manufacturers; our expectations regarding customer returns and related reserves and accruals; labeling and other changes for Rienso in the EU expected as a result of the review by the Medicinal Products for Human Use of IV iron-containing medications used to treat iron deficiency anemia; our expectations regarding the validity of our European ferumoxytol patent and timing of the appeals process; our expectations regarding the Branded Drug Fee under the Health Care Reform Act and the Medicare reimbursement rate for Feraheme and estimates for Medicaid rebates; our expectations regarding our license fee and other collaboration revenues; the effect of price increases; expected customer mix and utilization rates; the impact of volume rebates and other incentives; provider purchase patterns and use of competitive products; expectations regarding MuGard and our license arrangement with Access Pharmaceuticals, Inc.; the valuation of certain intangible assets, contingent consideration and other assets and liabilities, including our methodology and assumptions regarding fair value measurements; our gross-to-net sales adjustments; our Citizen's Petition; our expectation for product sales and our costs of product sales as a percentage of net product sales and royalties, our research and development expenses, external expenses and the timing of our planned research and development projects, and selling, general and administrative expenses; our belief regarding the potential impact of the adoption of newly issued and future accounting guidance on our financial statements; our expectations for our cash, cash equivalents and investments balances and information with respect to any other plans and strategies for our business; and other material risks described under the heading "Risk Factors" in our most recent annual report on Form 10-K and our quarterly reports on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC.

        You should rely only on information contained, or incorporated by reference, in this prospectus, the registration statement of which this prospectus is a part, the documents incorporated by reference in this prospectus, and any applicable prospectus supplement or free writing prospectus and understand that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in the foregoing documents by these cautionary statements.

        Although we believe that the expectations reflected in our forward-looking statements are reasonable, we cannot guarantee future results, events, levels of activity, performance or achievement. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, unless required by law. Before deciding to purchase our securities, you should carefully consider the risk factors incorporated herein by reference, in addition to the other information set forth in this prospectus, any accompanying prospectus supplement, any free writing prospectus and in the documents incorporated by reference.

OUR COMPANY

        This business overview highlights information contained in certain documents incorporated by reference into this prospectus. This business overview does not contain all of the information that you should consider before investing in our securities. You should read the entire prospectus carefully, including the "Risk Factors" section and the financial statements and the notes to those statements incorporated herein by reference, before making an investment decision.

        AMAG Pharmaceuticals, Inc., a Delaware corporation, was founded in 1981. We are a specialty pharmaceutical company that markets Feraheme® (ferumoxytol) Injection for Intravenous use to treat iron deficiency anemia (IDA) and MuGard® Mucoadhesive Oral Wound Rinse for the management of oral mucositis. Feraheme is a registered trademark of AMAG Pharmaceuticals,  Inc. and MuGard is a registered trademark of Access Pharmaceuticals, Inc.

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        Feraheme was approved for marketing in the U.S. in June 2009 by the U.S. Food and Drug Administration (FDA) for use as an intravenous iron replacement therapy for the treatment of IDA in adult patients with chronic kidney disease. We began selling Feraheme in the U.S. in July 2009 through our own commercial organization, including a specialty sales force. We sell Feraheme to authorized wholesalers and specialty distributors, who in turn, sell Feraheme to healthcare providers who administer Feraheme primarily within hospitals, hematology and oncology centers, and nephrology clinics.

        On June 6, 2013, we entered into a License Agreement with Access Pharmaceuticals, Inc. (Access) under which we acquired the U.S. commercial rights to MuGard (the Access License Agreement). MuGard is indicated for the management of oral mucositis/stomatitis (that may be caused by radiotherapy and/or chemotherapy) and all types of oral wounds (mouth sores and injuries), including aphthous ulcers/canker sores and traumatic ulcers, such as those caused by oral surgery or ill-fitting dentures or braces. Under the Access License Agreement, we obtained an exclusive, royalty-bearing license, with the right to grant sublicenses, to certain intellectual property rights, including know-how, patents and trademarks, to use, import, offer for sale, sell, manufacture and commercialize MuGard in the U.S. and its territories. In addition, Access has assigned us all of its right, title and interest in MuGard-related internet and social media outlets and other sales, marketing and promotional materials currently owned or controlled by Access. We sell MuGard to wholesalers and specialty and retail pharmacies.

        Our common stock trades on the NASDAQ Global Select Market, or NASDAQ, under the trading symbol "AMAG."

        Our principal offices are located at 1100 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (617) 498-3300. Our website address is www.amagpharma.com. Information found on, or accessible through, our website is not a part of, and is not incorporated into, this prospectus, and you should not consider it part of this prospectus or part of any prospectus supplement. Our website address is included in this document as an inactive textual reference only.

RISK FACTORS

        An investment in our securities involves a high degree of risk. In addition to the other information included in, or incorporated by reference into, this prospectus, the applicable prospectus supplement and any related free writing prospectus, you should carefully consider the risk factors incorporated by reference to our Annual Report on Form 10-K for the year ended December 31, 2012 and in our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2013, June 30, 2013 and September 30, 2013, as the same may be updated from time to time by our future filings under the Exchange Act, when determining whether or not to purchase the securities offered under this prospectus and the prospectus supplement.

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RATIO OF EARNINGS TO COMBINED FIXED CHARGES
AND PREFERENCE STOCK DIVIDENDS

        The following table sets forth our ratio of earnings to fixed charges and the ratio of our combined fixed charges and preference stock dividends to earnings for the periods indicated:

        The ratios above were computed by dividing earnings by fixed charges or by dividing earnings by combined fixed charges and preference dividends. For this purpose, earnings is calculated by as follows: (i) adding (a) pre-tax income (loss) from continuing operations before adjustment for income or loss from equity investees; (b) fixed charges; (c) amortization of capitalized interest; (d) distributed income of equity investees; and (e) our share of pre-tax losses of equity investees for which charges arising from guarantees are included in fixed charges; and (ii) then subtracting from such sum (a) interest capitalized; (b) preference security dividend requirements of our consolidated subsidiaries; and (c) any noncontrolling interest in the pre-tax income (loss) of our subsidiaries that have not incurred fixed charges. Equity investees are investments that we account for using the equity method of accounting.

        Fixed charges consist of that portion of rental expense associated with certain facility, equipment and vehicle leases considered to be a reasonable estimate of the interest factor. We did not pay or accrue any preference dividends for the periods presented.

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USE OF PROCEEDS

        Unless otherwise described in a prospectus supplement or related free writing prospectus, we intend to use the net proceeds from the sale of the offered securities for general corporate purposes, which may include, but are not limited to, working capital, strategic acquisitions and other potential business development activities, ongoing research and development activities and capital expenditures. Pending any specific utilization, the proceeds from the sale of the offered securities may be invested in a manner designed to ensure levels of liquidity which correspond to our current and foreseeable cash needs. Such investments may include, but may not be limited to, short-term investments, including government bonds, or other interest-bearing investments.

DESCRIPTION OF OUR COMMON STOCK

        This section describes the general terms of our common stock that we may offer from time to time. For more detailed information, a holder of our common stock should refer to our certificate of incorporation, our by-laws and our rights agreement with respect to our preferred share purchase rights plan, copies of which are filed with the SEC as exhibits to the registration statement of which this prospectus is a part.

        We are authorized to issue up to 58,750,000 shares of common stock, $.01 par value per share. As of October 31, 2013, approximately 21,736,357 shares of common stock were outstanding.

        Holders of our common stock are entitled to one vote per share and vote together as a single class on all matters to be voted on by our stockholders. Pursuant to our certificate of incorporation, there are no cumulative voting rights in the election of directors. The approval of corporate actions may also require the approval of the holders of any series of our preferred stock. See "Description of Our Preferred Stock."

        Our common stock will be the only type of our capital stock entitled to vote in the election and removal of directors and other matters presented to our stockholders from time to time, unless we issue voting preferred stock or our certificate of incorporation or the law requires otherwise.

        Our common stockholders will be entitled to receive dividends and distributions declared by our board of directors, or our board, to the extent permitted by outstanding series of preferred stock and by our certificate of incorporation. If a dividend is declared, it will be distributed pro rata to our common stockholders on a per share basis.

        If we are liquidated or dissolved, our common stockholders will be entitled to receive our assets and funds available for distribution to common stockholders in proportion to the number of shares they hold. Our common stockholders may not receive any assets or funds until our creditors have been paid in full and the preferential or participating rights of our preferred stockholders, if any, have been satisfied.

        Holders of our common stock will not have any preemptive, subscription or conversion rights with respect to shares of our common stock. We may issue additional shares of our common stock, if authorized by our board, without the common stockholders' approval, unless required by Delaware law or a stock exchange on which our securities are traded. The issuance of additional shares could have the effect of diluting any earnings per share and the book value per share of outstanding shares of common stock. If we receive the appropriate payment, shares of our common stock that we issue will be fully paid and nonassessable. There are no redemption or sinking fund provisions applicable to our common stock.

        Reference is made to the applicable prospectus supplement relating to the common stock offered by that prospectus supplement for specific terms, including:

•

amount and number of shares offered;



•

the initial offering price, if any, and market price;



•

information with respect to dividends; and



•

any listing of the common stock on any securities exchange or market.

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Stock Exchange Listing

        Our common stock is listed on the NASDAQ Global Select Market. The trading symbol for our common stock is "AMAG."

Transfer Agent and Registrar

        American Stock Transfer & Trust Company is the transfer agent and registrar for our common stock.

DESCRIPTION OF OUR PREFERRED STOCK

        This section describes the general terms and provisions of our preferred stock that we may offer from time to time. The applicable prospectus supplement will describe the specific terms of the shares of preferred stock offered through that prospectus supplement, which may differ from the terms we describe below. We will file a copy of the certificate of designation that contains the terms of each new series of preferred stock with the SEC each time we issue a new series of preferred stock, and these certificates of designation will be incorporated by reference into the registration statement of which this prospectus is a part. Each certificate of designation will establish the number of shares included in a designated series and fix the designation, powers, privileges, preferences and rights of the shares of each series as well as any applicable qualifications, limitations or restrictions. A holder of our preferred stock should refer to the applicable certificate of designation, our certificate of incorporation and the applicable prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you) for more specific information.

        We are authorized to issue up to 2,000,000 shares of preferred stock, $.01 par value per share, in multiple series, subject to limitations provided in our certificate of incorporation. To date, our board has designated 45,000 of the 2,000,000 authorized shares of preferred stock as Series A Junior Participating Preferred Stock, which series is described in greater detail below under "—Preferred Share Purchase Rights Plan." As of October 31, 2013, no other series has been designated and no shares of our preferred stock were outstanding.

        The issuance of preferred stock could adversely affect the voting power of holders of common stock and reduce the likelihood that common stockholders will receive dividend payments and payments upon liquidation. The issuance of preferred stock could have the effect of decreasing the market price of our common stock. The issuance of preferred stock also could have the effect of delaying, deterring or preventing a change in control of our company.

        With respect to each new series of our preferred stock, our board has the authority to fix, among other things, the following terms:

•

the designation of the series;



•

the number of shares within the series;



•

whether the dividends are cumulative and, if cumulative, the dates from which dividends are cumulative;



•

the rate of any dividends, any conditions upon which dividends are payable, and the dates of payment of dividends;



•

whether the shares are redeemable, the redemption price and the terms of redemption;



•

the amount payable to a holder for each share owned if we are dissolved or liquidated;



•

whether the shares are convertible or exchangeable, the price or rate of exchange, and the applicable terms and conditions;



•

any restrictions on issuance of shares in the same series or any other series;

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•

the voting rights, if any, of the shares of the series;



•

the provisions for a sinking fund, if any; and



•

any listing of the preferred stock on any securities exchange or market.

        Holders of our preferred stock will not have preemptive rights with respect to shares of our preferred stock. In addition, rights with respect to shares of our preferred stock will be subordinate to the rights of our general creditors. If we receive the appropriate payment, shares of our preferred stock that we issue will be fully paid and nonassessable.

        Preferred Share Purchase Rights Plan.    Each outstanding share of our common stock has attached to it one preferred share purchase right, which we refer to as a right. Each right entitles the registered holder of our common stock to purchase from us one one-thousandth of a share of Series A Junior Participating Preferred Stock, which we refer to as participating preferred shares, at a price of $250 per one one-thousandth of a participating preferred share, subject to adjustment. Each one one-thousandth of a share of participating preferred shares has designations and powers, preferences and rights, and the qualifications, limitations and restrictions that make its value approximately equal to the value of a share of our common stock at the end of the ten-year term of the rights. The description and terms of the rights are set forth in a Rights Agreement, dated as of September 4, 2009, between us and American Stock Transfer & Trust Company, LLC, as rights agent, or the rights agreement, which is incorporated by reference as an exhibit into the registration statement of which this prospectus is a part.

        Until the distribution date described below, we will not issue separate certificates evidencing the rights. Until that date, the rights will be evidenced, with respect to any common stock certificate, by that common stock certificate. The rights will detach from the common stock and a distribution date will occur upon the earlier of the following dates:

•

the 10^th day following the date of a public announcement that an "acquiring person," which may include an entity or group of affiliated or associated persons, has acquired beneficial ownership of 20% or more of our outstanding common stock; or



•

the 10^th business day following the commencement of, or announcement of an intention to make, a tender offer or exchange offer which would result in the beneficial ownership by an "acquiring person" of 20% or more of our outstanding common stock.

        Our board may postpone the distribution date by determining a later distribution date before the time any person or group becomes an acquiring person.

        The term "acquiring person" does not include us, any of our subsidiaries, any of our or our subsidiaries' employee benefit or compensation plans or any entity holding our common stock for or under any of our or our subsidiaries' employee benefit or compensation plans. In addition, a person who would otherwise be an acquiring person will not be considered an acquiring person if our board determines in good faith that such person inadvertently became the beneficial owner of 20% or more of our common stock and such person divests itself, as promptly as practicable following written notice from us, of beneficial ownership of a sufficient number of shares of our common stock so that it would no longer otherwise qualify as an acquiring person or, in the case of any derivative securities underlying a transaction entered into by such person or otherwise acquired by such person, such person terminates such transaction or otherwise disposes of such derivative securities so that such person would no longer be an "acquiring person," then such person shall not be considered an "acquiring person."

        In addition, except under limited circumstances, no person or entity shall become an acquiring person as the result of our acquisition of our common stock that, by reducing the number of shares outstanding, increases the proportionate number of shares beneficially owned by such person or entity to 20% or more of our outstanding common stock; provided, however, that if a person shall become the

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beneficial owner of 20% or more of our outstanding common stock by reason of our acquisition of our common stock and shall, following written notice from us, or public disclosure by us of such share purchases by us, become the beneficial owner of any additional common stock without our prior consent and shall then beneficially own more than 20% of our common stock, then outstanding, then such person shall be deemed to be an "acquiring person."

        The rights agreement provides that, until the distribution date, or earlier redemption or expiration of the rights, the rights will be transferred only with our common stock. The rights will be evidenced, with respect to any common stock certificate outstanding as of September 17, 2009, by that common stock certificate with a summary of the rights attached to it. Until the distribution date, or earlier redemption or expiration of the rights, new common stock certificates issued after September 17, 2009 upon transfer or new issuances of common stock will contain a notation incorporating the rights agreement by reference. Until the distribution date, the surrender for transfer of any certificates for common stock, even without a summary of the rights attached to it, also will constitute the transfer of the rights associated with the common stock represented by that certificate. As soon as practicable after the distribution date, separate certificates evidencing the rights will be mailed to holders of record of our common stock as of the close of business on the distribution date, and the separate right certificates alone will evidence the rights.

        The rights are not exercisable until the distribution date. The rights will expire on September 17, 2019, unless the rights are earlier redeemed or exchanged by us, in each case, as described below.

        The purchase price payable for the participating preferred shares, and the number of participating preferred shares or other securities or property issuable, upon exercise of the rights, as well as the number of rights outstanding, are subject to adjustment from time to time to prevent dilution in the following circumstances:

•

a stock dividend on, or a subdivision, combination or reclassification of, the participating preferred shares;



•

upon the grant to holders of the participating preferred shares of certain rights or warrants to subscribe for or purchase participating preferred shares at a price, or securities convertible into participating preferred shares with a conversion price, less than the then current market price of the participating preferred shares; or



•

upon the distribution to holders of the participating preferred shares of evidences of indebtedness or assets (excluding regular periodic cash dividends paid out of earnings or retained earnings or dividends payable in participating preferred shares) or of subscription rights or warrants (other than those referred to above).

        The exercise of rights to purchase participating preferred shares is at all times subject to the availability of a sufficient number of authorized but unissued participating preferred shares.

        The number of outstanding rights and the number of one one-thousandths of a participating preferred share issuable upon exercise of each right are also subject to adjustment in the event of a dividend or other distribution on the common stock payable in common stock or subdivisions, consolidations or combinations of our common stock occurring, in any of those cases, before the distribution date.

        Participating preferred shares purchasable upon exercise of the rights will be non-redeemable and rank junior to any other series of our preferred stock. Each participating preferred share would be entitled to receive a minimum preferential quarterly dividend payment of $1.00 per share but would be entitled to receive an aggregate dividend of 1,000 times the dividend declared per share of our common stock. If there is a liquidation, the holders of the participating preferred shares will be entitled to a minimum preferential liquidation payment of $250 per share and will be entitled to an aggregate

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payment of 1,000 times the payment made per share of our common stock. Each participating preferred share will have 1,000 votes, voting together with our common stock. Finally, in the event of any merger, consolidation or other transaction in which our common shares are exchanged, each participating preferred share will be entitled to receive 1,000 times the amount of consideration received per common share. These rights are protected by customary anti-dilution provisions.

        Because of the nature of the dividend, liquidation and voting rights of the participating preferred shares, the value of the one one-thousandth interest in a participating preferred share purchasable upon exercise of each right should approximate the value of one share of our common stock.

        In the event that any person or group of affiliated or associated persons becomes an "acquiring person," proper provision shall be made so that each holder of a right, other than rights beneficially owned by the "acquiring person" and its associates and affiliates (which will thereafter be void), will for a sixty (60) day period have the right to receive upon exercise that number of common shares having a market value of two times the exercise price of the right (or, if such number of shares is not and cannot be authorized, we may issue participating preferred shares, cash, debt, stock or a combination thereof in exchange for the rights). This right will terminate sixty (60) days after the date on which the rights become nonredeemable (as described below), unless there is an injunction or similar obstacle to exercise of the rights, in which event this right will terminate sixty (60) days after the date on which the rights again become exercisable.

        If we are acquired in a merger or other business combination transaction or 50% or more of our consolidated assets or earning power are sold to an "acquiring person", its associates or affiliates or certain other persons in which such persons have an interest, proper provision will be made so that each holder of a right will thereafter have the right to receive, upon the exercise thereof at the then current exercise price of the right, that number of shares of common stock of the acquiring company that at the time of such transaction will have a market value of two times the exercise price of the right.

        At any time after an "acquiring person" becomes an "acquiring person" and prior to the acquisition by such "acquiring person" of 50% or more of our outstanding common shares, our board may exchange the rights (other than rights owned by such person or group that have become void), in whole or in part, at an exchange ratio of one common share per right (or, in lieu of the common shares, at our election, we may issue cash, debt, stock or a combination thereof in exchange for the rights), subject to adjustment.

        With specified exceptions, no adjustments in the purchase price for the preferred shares will be required until cumulative adjustments require an adjustment of at least 1% in the purchase price. No fractional participating preferred shares will be issued, other than fractions that are integral multiples of one one-thousandth of a participating preferred share, which may, at our election, be evidenced by depositary receipts. Instead of issuing fractional participating preferred shares, we will make an adjustment in cash based on the closing price of the participating preferred shares on the last trading day immediately before the date of exercise.

        At any time prior to the earliest of (i) the day that a person has become an "acquiring person" or (ii) September 17, 2019, our board may redeem the rights in whole, but not in part, at a price of $0.01 per right, which may be paid in cash, common shares or any other consideration deemed appropriate by our board. The rights become nonredeemable on the day that a person has become an "acquiring person". Immediately upon any redemption of the rights, the right to exercise the rights will terminate and the only right of the holders of rights will be to receive the redemption price.

        Until a right is exercised, the holder of the right, in the capacity of a holder, will have no rights as a stockholder of ours, including, without limitation, the right to vote or to receive dividends. Although the distribution of the rights will not be taxable to stockholders or to us, stockholders may, depending upon the circumstances, recognize taxable income in the event that the rights become exercisable for our common stock or other consideration, or for common stock of any company acquiring us.

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        The terms of the rights generally may be amended by our board without the consent of the holders of the rights, except that from and after the time that the rights are no longer redeemable, no such amendment may adversely affect the interests of the holders of the rights (excluding the interests of any "acquiring person" and any group of affiliated or associated persons).

        The rights have certain anti-takeover effects. The rights will cause substantial dilution to a person or group that attempts to acquire us on terms not approved by our board. The rights should not interfere with any merger or other business combination approved by our board since the rights may be amended to permit such acquisition or redeemed by us at the redemption price prior to the earliest of (i) the time that a person or group has acquired beneficial ownership of 20% or more of our common shares or (ii) September 17, 2019.

        Transfer Agent and Registrar.    We currently plan to retain American Stock Transfer & Trust Company as the registrar and transfer agent of any series of our preferred stock.

DESCRIPTION OF OUR DEBT SECURITIES

        This section describes the general terms and provisions of our debt securities that we may issue from time to time. We may issue debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any future debt securities we may offer under this prospectus, the applicable prospectus supplement or free writing prospectus will describe the specific terms of any debt securities offered through that prospectus supplement or free writing prospectus. The terms of any debt securities we offer under a prospectus supplement or free writing prospectus may differ from the terms we describe below. Unless the context requires otherwise, whenever we refer to the "indentures," we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

        We will issue any senior debt securities under the senior indenture that we will enter into with the trustee named in the senior indenture. We will issue any subordinated debt securities under the subordinated indenture that we will enter into with the trustee named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement, of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

        The indentures will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We use the term "trustee" to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

        The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplement or free writing prospectus and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete applicable indenture that contains the terms of the debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

        We will describe in the applicable prospectus supplement or free writing prospectus the terms of the series of debt securities being offered, including:

•

the title;

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•

the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;



•

any limit on the amount that may be issued;



•

whether or not we will issue the series of debt securities in global form, and, if so, the terms and who the depository will be;



•

the maturity date;



•

whether and under what circumstances, if any, we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;



•

the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;



•

whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;



•

the terms of the subordination of any series of subordinated debt;



•

the place where payments will be payable;



•

restrictions on transfer, sale or other assignment, if any;



•

our right, if any, to defer payment of interest and the maximum length of any such deferral period;



•

the date, if any, after which, the conditions upon which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;



•

the date, if any, on which, and the price at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder's option, to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;



•

whether the indenture will restrict our ability or the ability of our subsidiaries to:



•

incur additional indebtedness;



•

issue additional securities;



•

create liens;



•

pay dividends or make distributions in respect of our capital stock or the capital stock of our subsidiaries;



•

redeem capital stock;



•

place restrictions on our subsidiaries' ability to pay dividends, make distributions or transfer assets;



•

make investments or other restricted payments;



•

sell or otherwise dispose of assets;



•

enter into sale-leaseback transactions;



•

engage in transactions with stockholders or affiliates;



•

issue or sell stock of our subsidiaries; or



•

effect a consolidation or merger;

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•

whether the indenture will require us to maintain any interest coverage, fixed charge, cash flow-based, asset-based or other financial ratios;



•

a discussion of certain material or special United States federal income tax considerations applicable to the debt securities;



•

information describing any book-entry features;



•

provisions for a sinking fund purchase or other analogous fund, if any;



•

the applicability of the provisions in the indenture on discharge;



•

whether the debt securities are to be offered at a price such that they will be deemed to be offered at an "original issue discount" as defined in paragraph (a) of Section 1273 of the Internal Revenue Code of 1986, as amended;



•

the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;



•

the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars; and



•

any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms that may be required by us or advisable under applicable laws or regulations or advisable in connection with the marketing of the debt securities.

Conversion or Exchange Rights

        We will set forth in the applicable prospectus supplement or free writing prospectus the terms on which a series of debt securities may be convertible into or exchangeable for our common stock, our preferred stock or other securities (including securities of a third-party). We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock, our preferred stock or other securities (including securities of a third-party) that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

        Unless we provide otherwise in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, the indentures will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate. If the debt securities are convertible into or exchangeable for other securities of ours or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities that the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

Events of Default Under the Indenture

        Unless we provide otherwise in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

•

if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended;

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•

if we fail to pay the principal, premium or sinking fund payment, if any, when due and payable at maturity, upon redemption or repurchase or otherwise, and the time for payment has not been extended;



•

if we fail to observe or perform any other covenant contained in the debt securities or the indentures, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive notice from the trustee or holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and



•

if specified events of bankruptcy, insolvency or reorganization occur.

        We will describe in each applicable prospectus supplement or free writing prospectus any additional events of default relating to the relevant series of debt securities.

        If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the unpaid principal, premium, if any, and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

        The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

        Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity or security satisfactory to it against any loss, liability or expense. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

•

the direction so given by the holder is not in conflict with any law or the applicable indenture; and



•

subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

        A holder of the debt securities of any series will have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:

•

the holder has given written notice to the trustee of a continuing event of default with respect to that series;



•

the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made written request, and such holders have offered reasonable indemnity to the trustee or security satisfactory to it against any loss, liability or expense or to be incurred in compliance with instituting the proceeding as trustee; and

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•

the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

        These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities, or other defaults that may be specified in the applicable prospectus supplement or free writing prospectus.

        We will periodically file statements with the trustee regarding our compliance with specified covenants in the indentures.

Modification of Indenture; Waiver

        Subject to the terms of the indenture for any series of debt securities that we may issue, we and the trustee may change an indenture without the consent of any holders with respect to the following specific matters:

•

to fix any ambiguity, defect or inconsistency in the indenture;



•

to comply with the provisions described above under "Description of Our Debt Securities—Consolidation, Merger or Sale;"



•

to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act;



•

to add to, delete from or revise the conditions, limitations, and restrictions on the authorized amount, terms, or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;



•

to provide for the issuance of and establish the form and terms and conditions of the debt securities of any series as provided under "Description of Our Debt Securities—General," to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;



•

to evidence and provide for the acceptance of appointment hereunder by a successor trustee;



•

to provide for uncertificated debt securities and to make all appropriate changes for such purpose;



•

to add to our covenants such new covenants, restrictions, conditions or provisions for the benefit of the holders, to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred to us in the indenture; or



•

to change anything that does not materially adversely affect the interests of any holder of debt securities of any series.

        In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, subject to the terms of the indenture for any series of debt securities that we may issue or as otherwise provided in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

•

extending the stated maturity of the series of debt securities;

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•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption or repurchase of any debt securities; or



•

reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

        Each indenture provides that, subject to the terms of the indenture and any limitation otherwise provided in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

•

register the transfer or exchange of debt securities of the series;



•

replace stolen, lost or mutilated debt securities of the series;



•

maintain paying agencies;



•

hold monies for payment in trust;



•

recover excess money held by the trustee;



•

compensate and indemnify the trustee; and



•

appoint any successor trustee.

        In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

        We will issue the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement or free writing prospectus, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depository named by us and identified in a prospectus supplement or free writing prospectus with respect to that series.

        At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement or free writing prospectus, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

        Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement or free writing prospectus, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

        We will name in the applicable prospectus supplement or free writing prospectus the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that

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we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

        If we elect to redeem the debt securities of any series, we will not be required to:

•

issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or



•

register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Trustee

        The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs.

        Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

        Unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

        We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement or free writing prospectus any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

        All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

        The indentures and the debt securities will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

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Ranking of Debt Securities

        The subordinated debt securities will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement or free writing prospectus. The subordinated indenture does not limit the amount of subordinated debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

        The senior debt securities will rank equally in right of payment to all our other senior unsecured debt. The senior indenture does not limit the amount of senior debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

DESCRIPTION OF OUR WARRANTS

        The following description, together with the additional information we include in any applicable prospectus supplements or free writing prospectus, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase common stock, preferred stock and/or debt securities in one or more series. Warrants may be offered independently or together with common stock, preferred stock and/or debt securities offered by any prospectus supplement or free writing prospectus, and may be attached to or separate from those securities. While the terms we have summarized below will generally apply to any future warrants we may offer under this prospectus, we will describe the particular terms of any warrants that we may offer in more detail in the applicable prospectus supplement or free writing prospectus. The terms of any warrants we offer under a prospectus supplement or free writing prospectus may differ from the terms we describe below.

        We will issue the warrants under a warrant agreement which we will enter into with a warrant agent to be selected by us. We have filed forms of these warrant agreements and forms of the warrant certificates representing the warrants as exhibits to the registration statement, of which this prospectus is a part, and the complete warrant agreements and forms of warrant certificates containing the terms of the warrants being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC. We use the term "warrant agreement" to refer to any of these warrant agreements. We use the term "warrant agent" to refer to the warrant agent under any of these warrant agreements. The warrant agent will act solely as an agent of ours in connection with the warrants and will not act as an agent for the holders or beneficial owners of the warrants.

        The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement applicable to a particular series of warrants. We urge you to read the applicable prospectus supplements or free writing prospectus related to the warrants that we sell under this prospectus, as well as the complete warrant agreements that contain the terms of the warrants.

General

        We will describe in the applicable prospectus supplement or free writing prospectus the terms relating to a series of warrants. If warrants for the purchase of debt securities are offered, the prospectus supplement or free writing prospectus will describe the following terms, to the extent applicable:

•

the offering price and the aggregate number of warrants offered;



•

the currencies in which the warrants are being offered;



•

the designation, aggregate principal amount, currencies, denominations and terms of the series of debt securities that can be purchased if a holder exercises a warrant;

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•

the designation and terms of any series of debt securities with which the warrants are being offered and the number of warrants offered with each such debt security;



•

the date on and after which the holder of the warrants can transfer them separately from the related series of debt securities;



•

the principal amount of the series of debt securities that can be purchased if a holder exercises a warrant and the price at which and currencies in which such principal amount may be purchased upon exercise;



•

the terms of any rights to redeem or call the warrants;



•

the date on which the right to exercise the warrants begins and the date on which such right expires;



•

federal income tax consequences of holding or exercising the warrants; and



•

any other specific terms, preferences, rights or limitations of, or restrictions on, the warrants.

Warrants for the purchase of debt securities will be in registered form only.

        If warrants for the purchase of common stock or preferred stock are offered, the prospectus supplement or free writing prospectus will describe the following terms, to the extent applicable:

•

the offering price and the aggregate number of warrants offered;



•

the total number of shares that can be purchased if a holder of the warrants exercises them and, in the case of warrants for preferred stock, the designation, total number and terms of the series of preferred stock that can be purchased upon exercise;



•

the designation and terms of any series of preferred stock with which the warrants are being offered and the number of warrants being offered with each share of common stock or preferred stock;



•

the date on and after which the holder of the warrants can transfer them separately from the related common stock or series of preferred stock;



•

the number of shares of common stock or preferred stock that can be purchased if a holder exercises the warrant and the price at which such common stock or preferred stock may be purchased upon exercise, including, if applicable, any provisions for changes to or adjustments in the exercise price and in the securities or other property receivable upon exercise;



•

the terms of any rights to redeem or call, or accelerate the expiration of, the warrants;



•

the date on which the right to exercise the warrants begins and the date on which that right expires;



•

federal income tax consequences of holding or exercising the warrants; and



•

any other specific terms, preferences, rights or limitations of, or restrictions on, the warrants.

Warrants for the purchase of common stock or preferred stock will be in registered form only.

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Exercise of Warrants

        Each holder of a warrant is entitled to purchase the principal amount of debt securities or number of shares of common stock or preferred stock, as the case may be, at the exercise price described in the applicable prospectus supplement or free writing prospectus. After the close of business on the day when the right to exercise terminates (or a later date if we extend the time for exercise), unexercised warrants will become void.

        A holder of warrants may exercise them by following the general procedure outlined below:

•

delivering to the warrant agent the payment required by the applicable prospectus supplement or free writing prospectus to purchase the underlying security;



•

properly completing and signing the reverse side of the warrant certificate representing the warrants; and



•

delivering the warrant certificate representing the warrants to the warrant agent within five business days of the warrant agent receiving payment of the exercise price.

        If you comply with the procedures described above, your warrants will be considered to have been exercised when the warrant agent receives payment of the exercise price, subject to the transfer books for the securities issuable upon exercise of the warrant not being closed on such date. After you have completed those procedures and subject to the foregoing, we will, as soon as practicable, issue and deliver to you the debt securities, common stock or preferred stock that you purchased upon exercise. If you exercise fewer than all of the warrants represented by a warrant certificate, a new warrant certificate will be issued to you for the unexercised amount of warrants. Holders of warrants will be required to pay any tax or governmental charge that may be imposed in connection with transferring the underlying securities in connection with the exercise of the warrants.

Amendments and Supplements to the Warrant Agreements

        We may amend or supplement a warrant agreement without the consent of the holders of the applicable warrants to cure ambiguities in the warrant agreement, to cure or correct a defective provision in the warrant agreement, or to provide for other matters under the warrant agreement that we and the warrant agent deem necessary or desirable, so long as, in each case, such amendments or supplements do not materially adversely affect the interests of the holders of the warrants.

Warrant Adjustments

        Unless the applicable prospectus supplement or free writing prospectus states otherwise, the exercise price of, and the number of securities covered by, a common stock warrant or preferred stock warrant will be adjusted proportionately if we subdivide or combine our common stock or preferred stock, as applicable. In addition, unless the prospectus supplement or free writing prospectus states otherwise, if we, without receiving payment:

•

issue capital stock or other securities convertible into or exchangeable for common stock or preferred stock, or any rights to subscribe for, purchase or otherwise acquire any of the foregoing, as a dividend or distribution to holders of our common stock or preferred stock;



•

pay any cash to holders of our common stock or preferred stock other than a cash dividend paid out of our current or retained earnings or other than in accordance with the terms of the preferred stock;



•

issue any evidence of our indebtedness or rights to subscribe for or purchase our indebtedness to holders of our common stock or preferred stock; or

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•

issue common stock or preferred stock or additional stock or other securities or property to holders of our common stock or preferred stock by way of spinoff, split-up, reclassification, combination of shares or similar corporate rearrangement,

then the holders of common stock warrants and preferred stock warrants, as applicable, will be entitled to receive upon exercise of the warrants, in addition to the securities otherwise receivable upon exercise of the warrants and without paying any additional consideration, the amount of stock and other securities and property such holders would have been entitled to receive had they held the common stock or preferred stock, as applicable, issuable under the warrants on the dates on which holders of those securities received or became entitled to receive such additional stock and other securities and property.

        Except as stated above or as otherwise set forth in the applicable prospectus supplement or free writing prospectus, the exercise price and number of securities covered by a common stock warrant and preferred stock warrant, and the amounts of other securities or property to be received, if any, upon exercise of those warrants, will not be adjusted or provided for if we issue those securities or any securities convertible into or exchangeable for those securities, or securities carrying the right to purchase those securities or securities convertible into or exchangeable for those securities.

        Holders of common stock warrants and preferred stock warrants may have additional rights under the following circumstances:

•

certain reclassifications, capital reorganizations or changes of the common stock or preferred stock, as applicable;



•

certain share exchanges, mergers, or similar transactions involving us and which result in changes of the common stock or preferred stock, as applicable; or



•

certain sales or dispositions to another entity of all or substantially all of our property and assets.

        If one of the above transactions occurs and holders of our common stock or preferred stock are entitled to receive stock, securities or other property with respect to or in exchange for their securities, the holders of the common stock warrants and preferred stock warrants then outstanding, as applicable, will be entitled to receive upon exercise of their warrants the kind and amount of shares of stock and other securities or property that they would have received upon the applicable transaction if they had exercised their warrants immediately before the transaction.

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DESCRIPTION OF OUR DEPOSITARY SHARES

        The following description, together with the additional information we include in any applicable prospectus supplements or free writing prospectus, contains general terms and provisions of the depositary shares that we may offer under this prospectus. The specific terms of the depositary shares offered will be described in the applicable prospectus supplement or free writing prospectus relating to such depositary shares, and such terms may differ from the terms we describe below. For more information, please refer to the provisions of the deposit agreement we will enter into with a depository to be selected, and our certificate of incorporation, including the form of certificate of designation for the applicable series of preferred stock.

General

        We may, at our option, elect to offer depositary shares rather than full shares of preferred stock. In the event such option is exercised, each of the depositary shares will represent ownership of and entitlement to all rights and preferences of a fraction of a share of preferred stock of a specified series (including dividend, voting, redemption and liquidation rights). The applicable fraction will be specified in a prospectus supplement. The preferred stock represented by the depositary shares will be deposited with a depository named in the applicable prospectus supplement, under a deposit agreement, among us, the depository and the holders of the certificates evidencing depositary shares, or depositary receipts. Depositary receipts will be delivered to those persons purchasing depositary shares in the offering. The depository will be the transfer agent, registrar and dividend disbursing agent for the depositary shares. Holders of depositary receipts agree to be bound by the deposit agreement, which requires holders to take certain actions such as filing proof of residence and paying certain charges.

Dividends

        The depository will distribute all cash dividends or other cash distributions received in respect of the series of preferred stock represented by the depositary shares to the record holders of depositary receipts in proportion to the number of depositary shares owned by such holders on the relevant record date, which will be the same date as the record date fixed by us for the applicable series of preferred stock. The depository, however, will distribute only such amount as can be distributed without attributing to any depositary share a fraction of one cent, and any balance not so distributed will be added to and treated as part of the next sum received by the depository for distribution to record holders of depositary receipts then outstanding.

        In the event of a distribution other than in cash, the depository will distribute property received by it to the record holders of depositary receipts entitled thereto, in proportion, as nearly as may be practicable, to the number of depositary shares owned by such holders on the relevant record date, unless the depository determines (after consultation with us) that it is not feasible to make such distribution, in which case the depository may (with our approval) adopt any other method for such distribution as it deems equitable and appropriate, including the sale of such property (at such place or places and upon such terms as it may deem equitable and appropriate) and distribution of the net proceeds from such sale to such holders.

Liquidation Preference

        In the event of the liquidation, dissolution or winding up of the affairs of the company, whether voluntary or involuntary, the holders of each depositary share will be entitled to the fraction of the liquidation preference accorded each share of the applicable series of preferred stock as set forth in the prospectus supplement.

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Redemption

        If the series of preferred stock represented by the applicable series of depositary shares is redeemable, such depositary shares will be redeemed from the proceeds received by the depository resulting from the redemption, in whole or in part, of preferred stock held by the depository. Whenever we redeem any preferred stock held by the depository, the depository will redeem as of the same redemption date the number of depositary shares representing the preferred stock so redeemed. The depository will mail the notice of redemption promptly upon receipt of such notice from us and not less than 30 nor more than 60 days prior to the date fixed for redemption of the preferred stock and the depositary shares to the record holders of the depositary receipts.

Voting

        Promptly upon receipt of notice of any meeting at which the holders of the series of preferred stock represented by the applicable series of depositary shares are entitled to vote, the depository will mail the information contained in such notice of meeting to the record holders of the depositary receipts as of the record date for such meeting. Each such record holder of depositary receipts will be entitled to instruct the depository as to the exercise of the voting rights pertaining to the number of shares of preferred stock represented by such record holder's depositary shares. The depository will endeavor, insofar as practicable, to vote such preferred stock represented by such depositary shares in accordance with such instructions, and we will agree to take all action which may be deemed necessary by the depository in order to enable the depository to do so. The depository will abstain from voting any of the shares of preferred stock to the extent that it does not receive specific instructions from the holders of depositary receipts.

Withdrawal of Preferred Stock

        Upon surrender of depositary receipts at the principal office of the depository, upon payment of any unpaid amount due the depository, and subject to the terms of the deposit agreement, the owner of the depositary shares evidenced thereby is entitled to delivery of the number of whole shares of preferred stock and all money and other property, if any, represented by such depositary shares. Fractional shares of preferred stock will not be issued. If the depositary receipts delivered by the holder evidence a number of depositary shares in excess of the number of depositary shares representing the number of whole shares of preferred stock to be withdrawn, the depository will deliver to such holder at the same time a new depositary receipt evidencing such excess number of depositary shares. Holders of shares of preferred stock thus withdrawn will not thereafter be entitled to deposit such shares under the deposit agreement or to receive depositary receipts evidencing depositary shares therefor.

Amendment and Termination of Deposit Agreement

        The form of depositary receipt evidencing the depositary shares and any provision of the deposit agreement may at any time and from time to time be amended by agreement between us and the depository. However, any amendment which materially and adversely alters the rights of the holders (other than any change in fees) of depositary shares will not be effective unless such amendment has been approved by the holders of at least a majority of the depositary shares then outstanding. No such amendment may impair the right, subject to the terms of the deposit agreement, of any owner of any depositary shares to surrender the depositary receipt evidencing such depositary shares with instructions to the depository to deliver to the holder of shares of preferred stock and all money and other property, if any, represented thereby, except in order to comply with mandatory provisions of applicable law.

        The deposit agreement will be permitted to be terminated by us upon not less than 30 days prior written notice to the applicable depository if a majority of each series of preferred stock affected by

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such termination consents to such termination, whereupon such depository will be required to deliver or make available to each holder of depositary receipts, upon surrender of the depositary receipts held by such holder, such number of whole or fractional shares of preferred stock as are represented by the depositary shares evidenced by such depositary receipts together with any other property held by such depository with respect to such depositary receipts. In addition, the deposit agreement will automatically terminate if (i) all outstanding depositary shares thereunder shall have been redeemed, (ii) there shall have been a final distribution in respect of the related shares of preferred stock in connection with any liquidation, dissolution or winding up of our company and such distribution shall have been distributed to the holders of depositary receipts evidencing the depositary shares representing such shares of preferred stock or (iii) each share of preferred stock shall have been converted into shares of our common stock not so represented by depositary shares.

Charges of Depository

        We will pay all transfer and other taxes and governmental charges arising solely from the existence of the depositary arrangements. We will pay charges of the depository in connection with the initial deposit of the shares of preferred stock and initial issuance of the depositary shares, and redemption of the shares of preferred stock and all withdrawals of shares of preferred stock by owners of depositary shares. Holders of depositary receipts will pay transfer, income and other taxes and governmental charges and certain other charges as are provided in the deposit agreement to be for their accounts. In certain circumstances, the depository may refuse to transfer depositary shares, may withhold dividends and distributions and sell the depositary shares evidenced by such depositary receipt if such charges are not paid.

Miscellaneous

        The depository will forward to the holders of depositary receipts all reports and communications from us which are delivered to the depository and which we are required to furnish to the holders of the shares of preferred stock. In addition, the depository will make available for inspection by holders of depositary receipts at the principal office of the depository, and at such other places as it may from time to time deem advisable, any reports and communications received from us which are received by the depository as the holder of shares of preferred stock.

        Neither we nor the depository assumes any obligation or will be subject to any liability under the deposit agreement to holders of depositary receipts other than for its negligence or willful misconduct. Neither we nor the depository will be liable if it is prevented or delayed by law or any circumstance beyond its control in performing its obligations under the deposit agreement. Our obligations under the deposit agreement and the obligations of the depository under the deposit agreement will be limited to performance in good faith of our and the depository's respective duties thereunder, and neither we nor the depository will be obligated to prosecute or defend any legal proceeding in respect of any depositary shares or shares of preferred stock unless satisfactory indemnity is furnished. We and the depository may rely on written advice of counsel or accountants, on information provided by holders of the depositary receipts or other persons believed in good faith to be competent to give such information and on documents believed to be genuine and to have been signed or presented by the proper party or parties. In the event the depository shall receive conflicting claims, requests or instructions from any holders of depositary receipts, on the one hand, and us, on the other hand, the depository shall be entitled to act on such claims, requests or instructions received from us.

Resignation and Removal of Depository

        The depository may resign at any time by delivering to us notice of its election to do so, and we may at any time remove the depository, any such resignation or removal to take effect upon the appointment of a successor depository and its acceptance of such appointment. Such successor

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depository must be appointed within 60 days after delivery of the notice for resignation or removal and must be a bank or trust company having its principal office in the United States of America and having a combined capital and surplus of at least $150,000,000.

DESCRIPTION OF OUR STOCK PURCHASE UNITS OR CONTRACTS

        This section outlines some of the provisions of the stock purchase units or contracts, the stock purchase unit or contract agreement and the pledge agreement. This information is not complete in all respects and is qualified entirely by reference to the stock purchase unit or contract agreement and pledge agreement with respect to the stock purchase units or contracts of any particular series. The specific terms of any series of stock purchase units or contracts will be described in the applicable prospectus supplement or free writing prospectus. If so described in a prospectus supplement or free writing prospectus, the specific terms of any series of stock purchase units or contracts may differ from the general description of terms presented below.

        Unless otherwise specified in the applicable prospectus supplement, we may issue stock purchase units or contracts, including contracts obligating holders to purchase from us and us to sell to the holders, a specified number of shares of common stock, shares of preferred stock or depositary shares at a future date or dates. Alternatively, the stock purchase units or contracts may obligate us to purchase from holders, and obligate holders to sell to us, a specified or varying number of shares of common stock, shares of preferred stock or depositary shares. The consideration per shares of common stock, share of preferred stock, or depositary share may be fixed at the time the stock purchase units or contracts are issued or may be determined by a specific reference to a formula set forth in the stock purchase units or contracts. The stock purchase units or contracts may provide for settlement by delivery by us or on our behalf of shares of the underlying security, or they may provide for settlement by reference or linkage to the value, performance or trading price of the underlying security. The stock purchase units or contracts may be issued separately or as part of stock purchase units consisting of a stock purchase contract and debt securities, shares of preferred stock or debt obligations of third parties, including U.S. treasury securities, other stock purchase contracts or common stock, or other securities or property, securing the holders' obligations to purchase or sell, as the case may be, the shares of common stock, shares of preferred stock, depositary shares or other security or property under the stock purchase units or contracts. The stock purchase units or contracts may require us to make periodic payments to the holders of the stock purchase units or vice versa, and such payments may be unsecured or prefunded on some basis and may be paid on a current or on a deferred basis. The stock purchase units or contracts may require holders to secure their obligations thereunder in a specified manner and may provide for the prepayment of all or part of the consideration payable by holders in connection with the purchase of the underlying security or other property pursuant to the stock purchase units or contracts.

        The securities related to the stock purchase units or contracts may be pledged to a collateral agent for our benefit pursuant to a pledge agreement to secure the obligations of holders of stock purchase units or contracts to purchase the underlying security or property under the related stock purchase units or contracts. The rights of holders of stock purchase units or contracts to the related pledged securities will be subject to our security interest therein created by the pledge agreement. No holder of stock purchase units or contracts will be permitted to withdraw the pledged securities related to such stock purchase units or contracts from the pledge arrangement.

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DESCRIPTION OF OUR SUBSCRIPTION RIGHTS

        The following is a general description of the terms of the subscription rights we may issue from time to time. Particular terms of any subscription rights we offer will be described in the prospectus supplement or free writing prospectus relating to such subscription rights, and may differ from the terms described herein.

        We may issue subscription rights to purchase our securities. These subscription rights may be issued independently or together with any other security offered hereby and may or may not be transferable by the stockholder receiving the subscription rights in such offering. In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other purchasers pursuant to which the underwriters or other purchasers may be required to purchase any securities remaining unsubscribed for after such offering.

        The applicable prospectus supplement will describe the specific terms of any offering of subscription rights for which this prospectus is being delivered, including the following:

•

whether common stock, preferred stock, or warrants for those securities will be offered under the stockholder subscription rights;



•

the price, if any, for the subscription rights;



•

the exercise price payable for each security upon the exercise of the subscription rights;



•

the number of subscription rights issued to each stockholder;



•

the number and terms of the securities which may be purchased per each subscription right;



•

the extent to which the subscription rights are transferable;



•

any other terms of the subscription rights, including the terms, procedures and limitations relating to the exchange and exercise of the subscription rights;



•

the date on which the right to exercise the subscription rights shall commence, and the date on which the subscription rights shall expire;



•

the extent to which the subscription rights may include an over-subscription privilege with respect to unsubscribed securities;



•

if appropriate, a discussion of material U.S. federal income tax considerations; and



•

if applicable, the material terms of any standby underwriting or purchase arrangement entered into by us in connection with the offering of subscription rights.

        The description in the applicable prospectus supplement of any subscription rights we offer will not necessarily be complete and will be qualified in its entirety by reference to the applicable subscription rights certificate or subscription rights agreement, which will be filed with the SEC if we offer subscription rights.

DESCRIPTION OF OUR UNITS

        This section outlines some of the provisions of the units and the unit agreements. This information may not be complete in all respects and is qualified entirely by reference to the unit agreement with respect to the units of any particular series. The specific terms of any series of units will be described in the applicable prospectus supplement or free writing prospectus. If so described in a particular prospectus supplement or free writing prospectus, the specific terms of any series of units may differ from the general description of terms presented below.

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        As specified in the applicable prospectus supplement, we may issue units consisting of one or more shares of common stock, shares of preferred stock, debt securities, depositary shares, warrants, stock purchase units or contracts, subscription rights or any combination of such securities.

        The applicable prospectus supplement will specify the following terms of any units in respect of which this prospectus is being delivered:

•

the terms of the units and of any of the shares of common stock, shares of preferred stock, debt securities, warrants, depositary shares, stock purchase units or contracts or subscription rights comprising the units, including whether and under what circumstances the securities comprising the units may be traded separately;



•

a description of the terms of any unit agreement governing the units;



•

if appropriate, a discussion of material U.S. federal income tax considerations; and



•

a description of the provisions for the payment, settlement, transfer or exchange of the units.

DESCRIPTION OF CERTAIN PROVISIONS OF DELAWARE LAW
AND OUR CERTIFICATE OF INCORPORATION AND BY-LAWS

        We are organized as a Delaware corporation. The following is a summary of our certificate of incorporation and by-laws and certain provisions of the Delaware General Corporation Law, or the DGCL. Because it is a summary, it does not contain all the information that may be important to you. If you want more information, you should read our entire certificate of incorporation and by-laws, copies of which are filed with the SEC as exhibits to the registration statement of which this prospectus is a part. See "Where You Can Find More Information," or refer to the provisions of Delaware law.

Classification of Directors

        Our by-laws provide that, except as otherwise required by specific provisions of the certificate of incorporation relating to the rights of holders of any class or series of preferred stock to elect additional directors under specified circumstances, the number of our directors may be fixed from time to time by a resolution adopted by a majority of our board but must not be less than one. Our board is not classified into classes. A director may be removed, with or without cause, by the holders of a majority of the shares then entitled to vote at an election of directors, subject to the rights of any series of preferred stock then outstanding.

Special Meetings

        Except as otherwise required by law and subject to the rights of holders of any class or series of preferred stock, special meetings of the stockholders may only be called by our President or by our board. No business other than that stated in the notice of meeting may be transacted at any special meeting of stockholders.

Limitation of Liability and Indemnification

        Our certificate of incorporation provides that we shall indemnify our directors and officers to the fullest extent that Delaware law permits. Our certificate of incorporation also provides that we, by action of our board, may provide indemnification to our employees and agents with the same scope and effect as the indemnification of our officers and directors. Delaware law permits a corporation to indemnify any director, officer, employee or agent made or threatened to be made a party to any pending or completed proceeding if the person acted in good faith and in a manner that the person reasonably believed to be in the best interests of the corporation and, with respect to any criminal proceeding, had no reasonable cause to believe that his or her conduct was unlawful.

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        Our certificate of incorporation limits the liability of our directors to the fullest extent permitted by the DGCL. Delaware law provides that directors will not be personally liable for monetary damages for breach of their fiduciary duties as directors, except liability for:

•

any breach of their duty of loyalty to the corporation or its stockholders;



•

acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law;



•

unlawful payments of dividends or unlawful stock repurchases or redemptions; or



•

any transaction from which the director derived an improper personal benefit.

        The effect of this provision may be to reduce the likelihood of derivative litigation against directors for breach of their duty of care, even though the action, if successful, might otherwise have benefited us and our stockholders. This provision has no effect on any non-monetary remedies that may be available to us or our stockholders, nor does it relieve us or our officers or directors from compliance with federal or state securities laws.

        Each of our directors and executive officers is party to an indemnification agreement that provides specific contractual assurance that the indemnification protection promised by certificate of incorporation and by-laws will be available.

        As permitted by our certificate of incorporation, we have purchased and maintain insurance on behalf of our directors and officers for any expense, liability or loss incurred by them arising out of their actions in that capacity if we would have the power to indemnify such person against such expense, liability or loss under the DGCL.

        Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers or persons controlling the registrant pursuant to the foregoing provisions, the registrant has been informed that in the opinion of the SEC such indemnification is against public policy and is therefore unenforceable.

Section 203 of the Delaware General Corporation Law

        Section 203 of the DGCL prohibits a defined set of transactions between a Delaware corporation, such as us, and an "interested stockholder." An interested stockholder is defined as a person who, together with any affiliates or associates of such person, beneficially owns, directly or indirectly, 15% or more of the outstanding voting stock of a Delaware corporation. This provision may prohibit business combinations between an interested stockholder and a corporation for a period of three years after the date the interested stockholder becomes an interested stockholder. The term "business combination" is broadly defined to include mergers, consolidations, sales or other dispositions of assets having a total value in excess of 10% of the consolidated assets of the corporation, and some other transactions that would increase the interested stockholder's proportionate share ownership in the corporation.

        This prohibition is effective unless:

•

either the business combination or the transaction that resulted in the interested stockholder becoming an interested stockholder is approved by our board prior to the time the interested stockholder becomes an interested stockholder;



•

the interested stockholder owns at least 85% of our voting stock, other than stock held by directors who are also officers or by qualified employee stock plans, upon completion of the transaction in which it becomes an interested stockholder; or



•

the business combination is approved by a majority of our board and by the affirmative vote of 66²/3% of the outstanding voting stock that is not owned by the interested stockholder.

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        In general, the prohibitions do not apply to business combinations with persons who were interested stockholders prior to the corporation becoming subject to Section 203.

LEGAL OWNERSHIP OF SECURITIES

        We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee or depository or warrant agent maintain for this purpose as the "holders" of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as "indirect holders" of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

        We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement or free writing prospectus. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depository on behalf of other financial institutions that participate in the depository's book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

        Only the person in whose name a security is registered is recognized as the holder of that security. Global securities will be registered in the name of the depository or its participants. Consequently, for global securities, we will recognize only the depository as the holder of the securities, and we will make all payments on the securities to the depository. The depository passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depository and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

        As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depository's book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not holders, of the securities.

Street Name Holders

        We may terminate a global security or issue securities that are not issued in global form. In these cases, investors may choose to hold their securities in their own names or in "street name." Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

        For securities held in street name, we or any applicable trustee or depository will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any such trustee or depository will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

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Legal Holders

        Our obligations, as well as the obligations of any applicable trustee or third party employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

        For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depository participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of an indenture, or for other purposes. In such an event, we would seek approval only from the legal holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the legal holders.

Special Considerations For Indirect Holders

        If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

•

how it handles securities payments and notices;



•

whether it imposes fees or charges;



•

how it would handle a request for the holders' consent, if ever required;



•

whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;



•

how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and



•

if the securities are global securities, how the depository's rules and procedures will affect these matters.

Global Securities

        A global security is a security which represents one or any other number of individual securities held by a depository. Generally, all securities represented by the same global securities will have the same terms.

        Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depository. Unless we specify otherwise in the applicable prospectus supplement or free writing prospectus, The Depository Trust Company, New York, New York, known as DTC, will be the depository for all global securities issued under this prospectus.

        A global security may not be transferred to or registered in the name of anyone other than the depository, its nominee or a successor depository, unless special termination situations arise. We describe those situations below under "—Special Situations When a Global Security Will Be Terminated." As a result of these arrangements, the depository, or its nominee, will be the sole registered owner and holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by

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means of an account with a broker, bank or other financial institution that in turn has an account with the depository or with another institution that does. Thus, an investor whose security is represented by a global security will not be a holder of the security, but only an indirect holder of a beneficial interest in the global security.

        If the prospectus supplement or free writing prospectus for a particular security indicates that the security will be issued as a global security, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

        As an indirect holder, an investor's rights relating to a global security will be governed by the account rules of the investor's financial institution and of the depository, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a legal holder of securities and instead deal only with the depository that holds the global security.

        If securities are issued only as a global security, an investor should be aware of the following:

•

An investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;



•

An investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;



•

An investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;



•

An investor may not be able to pledge his or her interest in the global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;



•

The depository's policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor's interest in the global security. We and any applicable trustee have no responsibility for any aspect of the depository's actions or for its records of ownership interests in the global security. We and the trustee also do not supervise the depository in any way;



•

The depository may, and we understand that DTC will, require that those who purchase and sell interests in the global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and



•

Financial institutions that participate in the depository's book-entry system, and through which an investor holds its interest in the global security, may also have their own policies affecting payments, notices and other matters relating to the securities. There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When A Global Security Will Be Terminated

        In a few special situations described below, a global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

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        A global security will terminate when the following special situations occur:

•

if the depository notifies us that it is unwilling, unable or no longer qualified to continue as depository for that global security and we do not appoint another institution to act as depository within 90 days;



•

if we notify any applicable trustee that we wish to terminate that global security; or



•

if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

        The prospectus supplement or free writing prospectus may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement or free writing prospectus. When a global security terminates, the depository, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

PLAN OF DISTRIBUTION

        We may sell the securities in and outside the United States (a) through underwriters or dealers, (b) directly to purchasers, including our affiliates, (c) through agents or (d) through a combination of any of these methods. The applicable prospectus supplement or free writing prospectus will include the following information:

•

the terms of the offering;



•

the names of any underwriters or agents;



•

the name or names of any managing underwriter or underwriters;



•

the purchase price of the securities;



•

the net proceeds from the sale of the securities;



•

any delayed delivery arrangements;



•

any underwriting discounts, commissions and other items constituting underwriters' compensation;



•

any initial public offering price;



•

any discounts or concessions allowed or reallowed or paid to dealers; and



•

any commissions paid to agents.

        The sale of the securities may be effected in transactions (a) on any national or international securities exchange or quotation service on which the securities may be listed or quoted at the time of sale, (b) in the over-the-counter market, (c) in transactions otherwise than on such exchanges or in the over-the-counter market or (d) through the writing of options.

        The distribution of offered securities may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, at market prices prevailing at the time of sale, at prices related to the market prices, or at negotiated prices.

Sale Through Underwriters or Dealers

        If underwriters are used in the sale of any of these securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. Underwriters may offer securities to the public either through

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underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. Unless we inform you otherwise in any prospectus supplement or free writing prospectus, the obligations of the underwriters to purchase the securities will be subject to certain conditions, and the underwriters will be obligated to purchase all the offered securities if they purchase any of them. We may grant underwriters an option to purchase additional securities to cover over-allotment, if any, or otherwise in connection with the distribution. The underwriters may change from time to time any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers.

        Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

        Any underwriters who are qualified market makers on NASDAQ (or any exchange or quotation system on which our securities are listed) may engage in passive market making transactions in our common stock, preferred stock, debt securities, warrants, depositary shares, stock purchase units or contracts, subscription rights or units, as applicable, on NASDAQ in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded.

        Some or all of the securities that we offer though this prospectus may be new issues of securities with no established trading market. Any underwriters to whom we sell these securities for public offering and sale may make a market in those securities, but they will not be obligated to and they may discontinue any market making at any time without notice. Accordingly, we cannot assure you of the liquidity of, or continued trading markets for, any securities that we offer.

        If dealers are used in the sale of securities, we will sell the securities to them as principals. They may then resell those securities to the public at varying prices determined by the dealers at the time of resale. We will include in the prospectus supplement or free writing prospectus the names of the dealers and the terms of the transaction.

Direct Sales and Sales Through Agents

        We may sell the securities directly, and not through underwriters or agents. We may also sell the securities through agents designated from time to time. In the prospectus supplement or free writing prospectus, we will name any agent involved in the offer or sale of the offered securities, and we will describe any commissions payable to the agent. Unless we inform you otherwise in the prospectus supplement or free writing prospectus, any agent will agree to use its reasonable best efforts to solicit purchases for the period of its appointment.

        We may sell the securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act with respect to any sale of those securities. We will describe the terms of any such sales in the prospectus supplement or free writing prospectus.

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        We may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement or free writing prospectus indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement or free writing prospectus, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be identified in the applicable prospectus supplement or free writing prospectus (or a post-effective amendment).

Delayed Delivery Contracts

        If we so indicate in the prospectus supplement or free writing prospectus, we may authorize agents, underwriters or dealers to solicit offers from certain types of institutions to purchase securities from us at the public offering price under delayed delivery contracts. These contracts would provide for payment and delivery on a specified date in the future. The contracts would be subject only to those conditions described in the prospectus supplement or free writing prospectus. The prospectus supplement or free writing prospectus will describe any commission payable for solicitation of those contracts.

Subscription Offerings

        Direct sales to investors or our stockholders may be accomplished through subscription offerings or through subscription rights distributed to stockholders. In connection with subscription offerings or the distribution of subscription rights to stockholders, if all of the underlying securities are not subscribed for, we may sell any unsubscribed securities to third parties directly or through underwriters or agents. In addition, whether or not all of the underlying securities are subscribed for, we may concurrently offer additional securities to third parties directly or through underwriters or agents. If securities are to be sold through subscription rights, the subscription rights will be distributed as a dividend to the stockholders for which they will pay no separate consideration.

General Information

        We may have agreements with the agents, dealers and underwriters to indemnify them against certain civil liabilities, including liabilities under the Securities Act, or to contribute with respect to payments that the agents, dealers or underwriters may be required to make. Agents, dealers and underwriters may be customers of, engage in transactions with or perform services for us in the ordinary course of their businesses.

LEGAL MATTERS

        Certain legal matters with respect to the securities offered hereby have been passed upon by Goodwin Procter LLP, Boston, Massachusetts.

EXPERTS

        The financial statements and management's assessment of the effectiveness of internal control over financial reporting (which is included in "Management's Annual Report on Internal Control over Financial Reporting") incorporated in this prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2012 have been so incorporated in reliance on the report(s) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

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DOCUMENTS INCORPORATED BY REFERENCE

        The SEC allows us to "incorporate by reference" the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information we incorporate by reference is considered part of this prospectus. Statements in this prospectus regarding the contents of any contract or other document may not be complete. You should refer to the copy of the contract or other document filed as an exhibit to the registration statement. Later information filed with the SEC will update and supersede information we have included or incorporated by reference in this prospectus.

        We incorporate by reference the documents listed below, which have been filed with the SEC (other than Current Reports or portions thereof furnished under Item 2.02 or Item 7.01 of Form 8-K):

1.

Our Annual Report on Form 10-K for the fiscal year ended December 31, 2012;



2.

Our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2013, June 30, 2013, and September 30, 2013;



3.

Our Current Reports on Form 8-K as filed on March 15, 2013 (solely with respect to Item 5.02 therein), April 4, 2013, May 21, 2013, May 24, 2013, June 10, 2013, June 13, 2013, August 1, 2013 (solely with respect to Item 8.01 therein), September 9, 2013, September 25, 2013, October 4, 2013, and October 23, 2013 (solely with respect to Item 8.01 therein and Exhibit 99.3 thereon);



4.

Our Definitive Proxy Statement on Schedule 14A as filed on April 19, 2013;



5.

The description of our common stock, which is registered under Section 12 of the Exchange Act, in our registration statement on Form 8-A as filed on June 26, 2006, including any amendment or report filed for the purpose of updating such descriptions; and



6.

The description of our Series A Junior Participating Preferred Stock Purchase Rights, or the rights, contained in our registration statement on Form 8-A registering the rights under Section 12 of the Exchange Act, filed with the SEC on September 4, 2009, including any amendments or reports filed for the purpose of updating that description.

        We also incorporate by reference any filings made after the date of the initial filing of the registration statement of which this prospectus forms a part including filings made prior to the effectiveness of the registration statement, made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 until the offering of the securities made by this prospectus is completed or terminated.

        We will provide without charge to each person, including any beneficial owner, to whom this prospectus is delivered, upon the written or oral request of that person, a copy of any and all of the information that has been incorporated in this prospectus by reference other than exhibits unless those exhibits are specifically incorporated by reference into the documents. Requests for these copies should be directed to our investor relations department at the following address and telephone number: AMAG Pharmaceuticals, Inc., 1100 Winter Street, Waltham, Massachusetts, 02451; (617) 498-3300.

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WHERE YOU CAN FIND MORE INFORMATION

        We file reports, proxy statements and other information with the SEC. You may read and copy the reports, proxy statements and other information that we file with the SEC at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for information about the operation of its Public Reference Room and for its prescribed rates to obtain copies of such material. The SEC also maintains an Internet site that contains reports, proxy and information statements and other information regarding registrants, like us, that file electronically with the SEC. The address of the SEC's Internet site is http://www.sec.gov. Our Internet site is http://www.amagpharma.com. Information contained on our Internet site is not a part of this prospectus.

        This prospectus provides you with a general description of the common stock, preferred stock, debt securities, warrants, depositary shares, stock purchase units or contracts, subscription rights and units being registered. This prospectus is part of a registration statement that we have filed with the SEC. To see more detail, you should read the registration statement and the exhibits and schedules filed with, or incorporated by reference into, our registration statement.

        This registration statement, including the exhibits contained or incorporated by reference therein, can be read at the SEC web site or at the SEC office referred to above. Any statement made or incorporated by reference in this prospectus concerning the contents of any contract, agreement or other document is only a summary of the actual contract, agreement or other document. If we have filed or incorporated by reference any contract, agreement or other document as an exhibit to the registration statement, you should read the exhibit for a more complete understanding of the document or matter involved. Each statement regarding a contract, agreement or other document is qualified in its entirety by reference to the actual document.

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$150,000,000

             % Convertible Senior Notes due 2019

Prospectus Supplement

February     , 2014

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