Edgar Filing: Prothena Corp plc

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549


SCHEDULE 13G
(Rule 13d-102)




(Amendment No.)*

Prothena Corporation plc
(Name of Issuer)

Ordinary Shares, $0.01 Par Value
(Title of Class of Securities)

IE00B91XRN20
(ISIN Number)^[1]

April 24, 2014
(Date of event which requires filing of this statement)


Check the appropriate box to designate the rule pursuant to which this Schedule 13G is filed:

¨	Rule 13d-1(b)
x	Rule 13d-1(c)
¨	Rule 13d-1(d)

(Page 1 of 11 Pages)

______________________________

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

____________________________

[1] The Ordinary Shares have no CUSIP number. The ISIN number for the Ordinary Shares is IE00B91XRN20.

CUSIP No. IE00B91XRN20

13G

Page 2 of 11 Pages

1	NAMES OF REPORTING PERSONS Adage Capital Partners, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 1,037,452
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 1,037,452
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,037,452
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.73%
12	TYPE OF REPORTING PERSON PN

CUSIP No. IE00B91XRN20

13G

Page 3 of 11 Pages

1	NAMES OF REPORTING PERSONS Adage Capital Partners GP, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 1,037,452
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 1,037,452
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,037,452
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.73%
12	TYPE OF REPORTING PERSON OO

CUSIP No. IE00B91XRN20

13G

Page 4 of 11 Pages

1	NAMES OF REPORTING PERSONS Adage Capital Advisors, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 1,037,452
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 1,037,452
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,037,452
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.73%
12	TYPE OF REPORTING PERSON OO

CUSIP No. IE00B91XRN20

13G

Page 5 of 11 Pages

1	NAMES OF REPORTING PERSONS Robert Atchinson
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 1,037,452
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 1,037,452
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,037,452
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.73%
12	TYPE OF REPORTING PERSON IN

CUSIP No. IE00B91XRN20

13G

Page 6 of 11 Pages

1	NAMES OF REPORTING PERSONS Phillip Gross
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 1,037,452
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 1,037,452
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,037,452
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.73%
12	TYPE OF REPORTING PERSON IN

CUSIP No. IE00B91XRN20

13G

Page 7 of 11 Pages

Item 1(a).	NAME OF ISSUER:

	The name of the issuer is Prothena Corporation plc (the “Company”).

Item 1(b).	ADDRESS OF ISSUER’S PRINCIPAL EXECUTIVE OFFICES:

	The Company’s principal executive offices are located at 650 Gateway Boulevard South San Francisco, California.

Item 2(a).	NAME OF PERSON FILING:
	This statement is filed by:

	(i)	Adage Capital Partners, L.P., a Delaware limited partnership ("ACP") with respect to the shares of Common Stock directly owned by it;

	(ii)	Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), as general partner of ACP with respect to the shares of Common Stock directly owned by ACP;

	(iii)	Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), as managing member of ACPGP, general partner of ACP, with respect to the shares of Common Stock directly owned by ACP;

	(iv)	Robert Atchinson ("Mr. Atchinson"), as managing member of ACA, managing member of ACPGP, general partner of ACP, with respect to the shares of Common Stock directly owned by ACP; and

	(v)	Phillip Gross ("Mr. Gross"), as managing member of ACA, managing member of ACPGP, general partner of ACP, with respect to the shares of Common Stock directly owned by ACP.

	The foregoing persons are hereinafter sometimes collectively referred to as the “Reporting Persons.” Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party.

Item 2(b).

ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:

The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52^nd floor, Boston, Massachusetts 02116.

Item 2(c).

CITIZENSHIP:

ACP is a limited partnership organized under the laws of the State of Delaware. ACPGP and ACA are limited liability companies organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States.

Item 2(d).	TITLE OF CLASS OF SECURITIES:

	Ordinary Shares, $0.01 par value per share (the "Ordinary Shares").

CUSIP No. IE00B91XRN20

13G

Page 8 of 11 Pages

Item 2(e).	CUSIP NUMBER:

	The Ordinary Shares have no CUSIP number. The ISIN number for the Ordinary Shares is IE00B91XRN20.

Item 3.

IF THIS STATEMENT IS FILED PURSUANT TO §§ 240.13d-1(b) OR 240.13d-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A:

(a)	¨	Broker or dealer registered under Section 15 of the Act (15 U.S.C. 78o);
(b)	¨	Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	¨	Insurance company as defined in Section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	¨	Investment company registered under Section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	¨	Investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);
(f)	¨	Employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);
(g)	¨	Parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);
(h)	¨	Savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	¨	Church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act (15 U.S.C. 80a-3);
(j)	¨	Non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J);
(k)	¨	Group, in accordance with Rule 13d-1(b)(1)(ii)(K).

If filing as a non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J), please

specify the type of institution: Not applicable.

Item 4.

OWNERSHIP.

A.	Adage Capital Partners, L.P., Adage Capital Partners GP, L.L.C. and Adage Capital Advisors, L.L.C.
		(a)	Amount beneficially owned: 1,037,452
		(b)	Percent of class: 4.73%. The percentages used herein and in the rest of this Schedule 13G are calculated based upon the 21,902,937 Ordinary Shares issued and outstanding as of as of March 3, 2014 as reflected in the Company's Form 10-K filed by the Company on March 7, 2014. On the date of the event which requires the filing of this Schedule 13G, each of the Reporting Persons may have been deemed to be the beneficial owner of more than five percent of the outstanding shares.
		(c)	(i)	Sole power to vote or direct the vote: 0
			(ii)	Shared power to vote or direct the vote: 1,037,452
			(iii)	Sole power to dispose or direct the disposition: 0
			(iv)	Shared power to dispose or direct the disposition of: 1,037,452

CUSIP No. IE00B91XRN20

13G

Page 9 of 11 Pages

ACP has the power to dispose of and the power to vote the shares of Ordinary Share beneficially owned by it, which power may be exercised by its general partner, ACPGP. ACA, as managing member of ACPGP, directs ACPGP's operations. Neither ACPGP nor ACA directly own any shares of Ordinary Share. By reason of the provisions of Rule 13d-3 of the Securities Exchange Act of 1934 (the "Act"), ACPGP and ACA may be deemed to beneficially own the shares owned by ACP.

	B.	Robert Atchinson and Phillip Gross
			(a)	Amount beneficially owned: 1,037,452
			(b)	Percent of class: 4.73%
			(c)	(i)	Sole power to vote or direct the vote: 0
				(ii)	Shared power to vote or direct the vote: 1,037,452
				(iii)	Sole power to dispose or direct the disposition: 0
				(iv)	Shared power to dispose or direct the disposition: 1,037,452

Messrs. Atchinson and Gross, as managing members of ACA, have shared power to vote the Ordinary Share beneficially owned by ACP. Neither Mr. Atchinson nor Mr. Gross directly own any shares of Ordinary Share. By reason of the provisions of Rule 13d-3 of the Act, each may be deemed to beneficially own the shares beneficially owned by ACP.

Item 5.	OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

	If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [X]

Item 6.	OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.

	Not applicable.

Item 7.	IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY.

	Not applicable.

Item 8.	IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP.

	Not applicable.

Item 9.	NOTICE OF DISSOLUTION OF GROUP.

	Not applicable.

Item 10.	CERTIFICATION.

	Each of the Reporting Persons hereby makes the following certification:

	By signing below each Reporting Person certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

CUSIP No. IE00B91XRN20

13G

Page 10 of 10 Pages

SIGNATURES

After reasonable inquiry and to the best of our knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct.

DATED: May 2, 2014

	ADAGE CAPITAL PARTNERS, L.P.
	By: Adage Capital Partners GP, L.L.C.,
	its general partner

	By: Adage Capital Advisors, L.L.C.,
	its managing member

	/s/ Robert Atchinson
	Name: Robert Atchinson
	Title: Managing Member

	ADAGE CAPITAL PARTNERS GP, L.L.C.
	By: Adage Capital Advisors, L.L.C.,
	its managing member

	/s/ Robert Atchinson
	Name: Robert Atchinson
	Title: Managing Member

	ADAGE CAPITAL ADVISORS, L.L.C.

	/s/ Robert Atchinson
	Name: Robert Atchinson
	Title: Managing Member

	ROBERT ATCHINSON

	/s/ Robert Atchinson
	ROBERT ATCHINSON, individually

	PHILLIP GROSS

	/s/ Phillip Gross
	PHILLIP GROSS, individually

CUSIP No. IE00B91XRN20

13G

Page 11 of 11 Pages

EXHIBIT 1

JOINT FILING AGREEMENT
PURSUANT TO RULE 13d-1(k)

The undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements. The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained herein and therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.

DATE: May 2, 2014

ADAGE CAPITAL PARTNERS, L.P.

By: Adage Capital Partners GP, L.L.C.,

its general partner

By: Adage Capital Advisors, L.L.C.,

its managing member

/s/ Robert Atchinson

Name: Robert Atchinson

Title: Managing Member

ADAGE CAPITAL PARTNERS GP, L.L.C.

By: Adage Capital Advisors, L.L.C.,

its managing member

/s/ Robert Atchinson

Name: Robert Atchinson

Title: Managing Member

ADAGE CAPITAL ADVISORS, L.L.C.

/s/ Robert Atchinson

Name: Robert Atchinson

Title: Managing Member

/s/ Robert Atchinson

ROBERT ATCHINSON, individually

/s/ Phillip Gross

PHILLIP GROSS, individually