SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* BVF PARTNERS L P/IL (Last) (First) (Middle) 900 N. MICHIGAN AVENUE SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 05/15/2009	3. Issuer Name and Ticker or Trading Symbol REPLIGEN CORP [ RGEN ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) X Other (specify below) Group Member	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	825,750	D(1)
Common Stock	534,400	D(2)
Common Stock	1,856,700	D(3)
Common Stock	3,216,850	I(4)	General partner and manager of entities with direct ownership.
Common Stock	3,216,850	I(5)	General partner of entity with indirect ownership.
Common Stock	3,216,850	I(6)	Sole shareholder and sole director of entity with indirect ownership.

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* BVF PARTNERS L P/IL (Last) (First) (Middle) 900 N. MICHIGAN AVENUE SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

1. Name and Address of Reporting Person* BIOTECHNOLOGY VALUE FUND L P (Last) (First) (Middle) 900 N. MICHIGAN AVENUE, SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

1. Name and Address of Reporting Person* BIOTECHNOLOGY VALUE FUND II LP (Last) (First) (Middle) C/O GROSVENOR CAPITAL MANAGEMENT 900 N. MICHIGAN AVENUE, SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

1. Name and Address of Reporting Person* BVF INVESTMENTS LLC (Last) (First) (Middle) C/O GROSVENOR CAPITAL MANAGEMENT LP 900 N. MICHIGAN AVENUE, SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

1. Name and Address of Reporting Person* BVF INC/IL (Last) (First) (Middle) C/O GROSVENOR CAPITAL MANAGEMENT 900 N. MICHIGAN AVENUE, SUITE 1100 (Street) CHICAGO IL 60611 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

1. Name and Address of Reporting Person* LAMPERT MARK N (Last) (First) (Middle) 2415 GREEN ST (Street) SAN FRANCISCO CA 94123 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Group Member

Explanation of Responses:

1. The shares of Common Stock are directly beneficially owned by Biotechnology Value Fund, L.P. ("BVF"), a Delaware limited partnership.

2. The shares of Common Stock are directly beneficially owned by Biotechnology Value Fund II, L.P. ("BVF2"), a Delaware limited partnership.

3. The shares of Common Stock are directly beneficially owned by BVF Investments, LLC ("BVFLLC"), a Delaware limited liability company. Pursuant to the operating agreement of BVFLLC, BVF Partners, L.P., a Delaware limited partnership ("Partners") is authorized, among other things, to invest the contributed capital of Samana Capital, L.P., the majority member of BVFLLC, in the shares of Common Stock and other securities and to vote, exercise or convert and dispose of such securities and is entitled to receive fees based on assets under management and, subject to certain exceptions, allocations based on realized and unrealized gains on such assets.

4. The shares of Common Stock are indirectly beneficially owned by Partners. Partners is the general partner of BVF and BVF2 and is the manager of BVFLLC.

5. The shares of Common Stock are indirectly beneficially owned by BVF Inc., a Delaware corporation ("BVF Inc."). BVF Inc. is the general partner of Partners.

6. Mark N. Lampert is the sole shareholder, sole director, and an officer of BVF Inc.

	BVF PARTNERS L.P., By: BVF Inc., its General Partner, By: /s/ Mark N. Lampert, President	05/20/2009
	BIOTECHNOLOGY VALUE FUND, L.P., By: BVF Partners L.P., its General Partner, By: BVF Inc., its General Partner, By: /s/ Mark N. Lampert, President	05/20/2009
	BIOTECHNOLOGY VALUE FUND II, L.P., By: BVF Partners L.P., its General Partner, By: BVF Inc., its General Partner, By: /s/ Mark N. Lampert, President	05/20/2009
	BVF INVESTMENTS, L.L.C., By: BVF Partners L.P., its Manager, By: BVF Inc., its General Partner, By: /s/ Mark N. Lampert, President	05/20/2009
	BVF INC., By: /s/ Mark N. Lampert, President	05/20/2009
	Mark N. Lampert, By: /s/ Mark N. Lampert	05/20/2009
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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