UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Schedule TO

Amendment No. 1
(Rule 14d-100)

Tender Offer Statement under Section 14(d)(1) or 13(e)(1)
of the Securities Exchange Act of 1934

SIRTRIS PHARMACEUTICALS, INC.

Fountain Acquisition Corporation
and
GlaxoSmithKline plc
(Names of Filing Persons (Offerors))

Common Stock, par value $0.001 per share
(Title of Class of Securities)

82968A105
(CUSIP Number of Class of Securities)

Carol G. Ashe, Esq.
GlaxoSmithKline
One Franklin Plaza (FP 2355)
200 N. 16th Street
Philadelphia, Pennsylvania 19102
(215) 741-4000
(Name, Address and Telephone Numbers of Person Authorized
to Receive Notices and Communications on Behalf of Filing Persons)

Copy to:
Victor I. Lewkow, Esq.
Cleary Gottlieb Steen & Hamilton LLP
One Liberty Plaza
New York, New York 10006
(212) 225-2000

CALCULATION OF FILING FEE

Transaction Valuation*		Amount of Filing Fee**
$692,189,100		$27,203.03

 

 

þ

Check the box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid: $27,203.03		Filing Party: Fountain Acquisition Corporation and GlaxoSmithKline plc
Form or Registration No.: Schedule TO		Date Filed: May 2, 2008

o Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the statement relates:

þ third-party tender offer subject to Rule 14d-1.

o issuer tender offer subject to Rule 13e-4.

o going-private transaction subject to Rule 13e-3.

o amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer: o

     This Amendment No. 1 to the Tender Offer Statement on Schedule TO (this “Amendment”), filed with the Securities and Exchange Commission on May 20, 2008, amends and supplements the Tender Offer Statement on Schedule TO filed on May 2, 2008 (the “Schedule TO”) and relates to the offer by Fountain Acquisition Corporation, a Delaware corporation (“Purchaser”) and a direct wholly-owned subsidiary of SmithKline Beecham Corporation, a Pennsylvania corporation (“SKB”), and an indirect wholly-owned subsidiary of GlaxoSmithKline plc, a public limited company organized under the laws of England and Wales (“GSK”), to purchase all outstanding shares of common stock, par value $0.001 per share (the “Shares”), of Sirtris Pharmaceuticals, Inc., a Delaware corporation (“Sirtris”), at a price of $22.50 per Share, net to the seller in cash, without interest thereon and less any required withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase dated May 2, 2008 (the “Offer to Purchase”) and in the related Letter of Transmittal (which, together with any amendments or supplements thereto, collectively constitute the “Offer”), which are annexed to and filed with the Schedule TO as Exhibits (a)(1)(A) and (a)(1)(B), respectively. This Amendment is being filed on behalf of Purchaser and GSK.

     All information set forth in the Offer to Purchase filed as Exhibit (a)(1)(A) to the Schedule TO is incorporated by reference in answer to Items 1 through 11 in the Schedule TO, except those items as to which information is specifically provided herein. The Agreement and Plan of Merger, dated as of April 22, 2008, by and among Purchaser, SKB and Sirtris, a copy of which is attached as Exhibit (d)(1) to the Schedule TO, is incorporated herein by reference with respect to Items 4 through 11 of the Schedule TO.

Item 11.		Additional Information.

     Item 11 of the Schedule TO is hereby amended and supplemented by adding the following:

     On May 2, 2008, GSK filed a Premerger Notification and Report Form with respect to the Offer with the Antitrust Division of the Department of Justice and the Federal Trade Commission (the “FTC”) in accordance with the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the “HSR Act”).

     At 11:59 p.m., New York City time, on May 19, 2008, the HSR Act waiting period with respect to the Offer and Merger expired. Accordingly, the condition to the Offer that any waiting period under the HSR Act shall have expired or been terminated has been satisfied.

SIGNATURE

     After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: May 20, 2008