Edgar Filing: REPLIGEN CORP

SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

SCHEDULE 13G/A
(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
TO RULES 13d-1(b) (c) AND (d) AND AMENDMENTS THERETO FILED
PURSUANT TO 13d-2(b)

(Amendment No. 5)*
Repligen Corporation

(Name of Issuer)

Common Stock

(Title of Class of Securities)

759916109

(CUSIP Number)

May 15, 2009

(Date of Event Which Requires Filing of this Statement)

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

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

*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 on 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 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).


CUSIP No. 759916109	13G	Page 2 of 12 Pages


1	NAME OF REPORTING PERSON: Biotechnology Value Fund, L.P. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*	(a) x
		(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware

		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			825,750
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			825,750

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	825,750

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	2.69%

12	TYPE OF REPORTING PERSON*
	PN


CUSIP No. 759916109	13G	Page 3 of 12 Pages


1	NAME OF REPORTING PERSON: Biotechnology Value Fund II, L.P. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*	(a) x
		(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware

		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			534,400
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			534,400

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	534,400

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	1.74%

12	TYPE OF REPORTING PERSON*
	PN


CUSIP No. 759916109		13G	Page 4 of 12 Pages


1	NAME OF REPORTING PERSON: BVF Investments, L.L.C. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*			(a) x
				(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware


	5	SOLE VOTING POWER
NUMBER OF		0
SHARES
BENEFICIALLY	6	SHARED VOTING POWER
OWNED		1,856,700
BY
EACH	7	SOLE DISPOSITIVE POWER
REPORTING		0
PERSON
WITH:	8	SHARED DISPOSITIVE POWER
		1,856,700


9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	1,856,700

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*	o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	6.05%

12	TYPE OF REPORTING PERSON*
	OO


CUSIP No. 759916109	13G	Page 5 of 12 Pages


1	NAME OF REPORTING PERSON: Investment 10, L.L.C. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*	(a) x
		(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Illinois

		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			200,100
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			200,100

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	200,100

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	.65%

12	TYPE OF REPORTING PERSON*
	OO


CUSIP No. 759916109	13G	Page 6 of 12 Pages

1	NAME OF REPORTING PERSON: BVF Partners L.P. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*	(a) x
		(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware

		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			3,416,950
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			3,416,950

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	3,416,950

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	11.13%

12	TYPE OF REPORTING PERSON*
	PN, HC

CUSIP No. 759916109		13G	Page 7 of 12 Pages



1	NAME OF REPORTING PERSON: BVF Inc. S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*			(a) x
				(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware


		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			3,416,950
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			3,416,950

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	3,416,950

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	11.13%

12	TYPE OF REPORTING PERSON*
	HC, CO

CUSIP No. 759916109		13G	Page 8 of 12 Pages



1	NAME OF REPORTING PERSON: Mark N. Lampert S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY):

2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*			(a) x
				(b) o


3	SEC USE ONLY


4	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States


		5	SOLE VOTING POWER
NUMBER OF			0
SHARES
BENEFICIALLY		6	SHARED VOTING POWER
OWNED			3,416,950
BY
EACH		7	SOLE DISPOSITIVE POWER
REPORTING			0
PERSON
WITH:		8	SHARED DISPOSITIVE POWER
			3,416,950

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	3,416,950

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*			o


11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	11.13%

12	TYPE OF REPORTING PERSON*
	IN


CUSIP No. 759916109		13G		Page 9 of 12 Pages

ITEM 1(a). NAME OF ISSUER:

Repligen Corporation (“Repligen”)

ITEM 1(b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

41 Seyon Street, Bldg 1, Suite 100
Waltham, MA 02453
United States

ITEM 2(a). NAME OF PERSON FILING:

This Amendment No. 5 to Schedule 13G is being filed on behalf of the following persons (the "Reporting Persons"):

	(i)		Biotechnology Value Fund, L.P. ("BVF")
	(ii)		Biotechnology Value Fund II, L.P. ("BVF2")
	(iii)		BVF Investments, L.L.C. ("BVFLLC")
	(iv)		Investment 10, L.L.C. ("ILL10")
	(v)		BVF Partners L.P. ("Partners")
	(vi)		BVF Inc. ("BVF Inc.")
	(vii)		Mark N. Lampert (“Mr. Lampert”)

ITEM 2(b). ADDRESS OF PRINCIPAL BUSINESS OFFICE:

The principal business office of the Reporting Persons comprising the group filing this Amendment No. 5 to Schedule 13G is located at 900 North Michigan Avenue, Suite 1100, Chicago, Illinois, 60611.

ITEM 2(c). CITIZENSHIP:

		BVF:	a Delaware limited partnership
		BVF2:	a Delaware limited partnership
		BVFLLC:	a Delaware limited liability company
		ILL10:	an Illinois limited liability company
		Partners:	a Delaware limited partnership
		BVF Inc.:	a Delaware corporation
		Mark N. Lampert	United States

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

This Amendment No. 5 to Schedule 13G is being filed with respect to the common stock, par value $0.01 per share (“Common Stock”), of Repligen. The Reporting Persons’ percentage ownership of Common Stock is based on 30,691,707 shares of Common Stock being outstanding.


CUSIP No. 759916109		13G		Page 10 of 12 Pages

As of May 15, 2009, BVF beneficially owned 825,750 shares of Common Stock, BVF2 beneficially owned 534,400 shares of Common Stock, BVFLLC beneficially owned 1,856,700 shares of Common Stock and ILL10 beneficially owned 200,100 shares of Common Stock. Beneficial ownership by Partners, BVF Inc., and Mr. Lampert includes 3,416,950 shares of Common Stock.

ITEM 2(e). CUSIP Number:

759916109

ITEM 3.

IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(b), or 13d-2(b) or (c) CHECK WHETHER THE PERSON FILING IS: One of the following

Not applicable as this Amendment No. 5 to Schedule 13G is filed pursuant to Rule 13d-1(c).

ITEM 4. OWNERSHIP:

The information in items 1 and 5 through 11 on the cover pages (pp. 2 - 8) on this Amendment No. 5 to Schedule 13G is hereby incorporated by reference.

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 Persons have ceased to be the beneficial owner of more than five percent of the class of securities check the following.

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

Pursuant to the operating agreement of BVFLLC, 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. Partners and BVF Inc. share voting and dispositive power over shares of the Common Stock beneficially owned by BVF, BVF2, BVFLLC and those owned by ILL10, on whose behalf Partners acts as an investment manager and, accordingly, Partners and BVF Inc. have beneficial ownership of all of the shares of the Common Stock owned by such parties.

ITEM 7.

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


CUSIP No. 759916109		13G		Page 11 of 12 Pages

Mr. Lampert is the owner, sole director and an officer of BVF Inc. BVF Inc. is the general partner of Partners, which is the general partner of BVF and BVF2. Partners is the manager of BVFLLC and is investment adviser to ILL10.

ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF A GROUP:

The members of the group making this filing on Amendment No. 5 to Schedule 13G are: Biotechnology Value Fund, L.P., Biotechnology Value Fund II, L.P., BVF Investments, L.L.C., Investment 10, L.L.C., BVF Partners L.P., BVF Inc. and Mr. Lampert.

ITEM 9. NOTICE OF DISSOLUTION OF GROUP:

Not applicable.


CUSIP No. 759916109		13G		Page 12 of 12 Pages

ITEM 10. CERTIFICATION

By signing below I certify that, to the best of my 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.

After reasonable 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, 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
			Mark N. Lampert President
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
			Mark N. Lampert President
BVF INVESTMENTS, L.L.C.
By:	BVF Partners L.P., its manager
	By:	BVF Inc., its general partner
		By:	/s/ Mark N. Lampert
			Mark N. Lampert President

INVESTMENT 10, L.L.C
By:	BVF Partners L.P., its attorney-in-fact
	By:	BVF Inc., its general partner
		By:	/s/ Mark N. Lampert
			Mark N. Lampert President
BVF PARTNERS L.P.
By:	BVF Inc., its general partner
		By:	/s/ Mark N. Lampert
			Mark N. Lampert President
BVF INC.
		By:	/s/ Mark N. Lampert
			Mark N. Lampert President

		MARK N. LAMPERT
						By:		/s/ Mark N. Lampert

Exhibit A
JOINT FILING AGREEMENT

The undersigned agree that this Amendment No. 5 to Schedule 13G, dated May 20, 2009, relating to the Common Stock of Repligen Corporation shall be filed on behalf of the undersigned.

Dated: May 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

Mark N. Lampert, President

BIOTECHNOLOGY VALUE FUND II, L.P.

By: BVF Partners, L.P., its general partner

By: BVF Inc., its general partner

By: /s/ Mark N. Lambert

Mark N. Lampert, President

BVF INVESTMENTS, L.L.C.

By: BVF Partners, L.P., its manager

By: BVF Inc., its general partner

By: /s/ Mark N. Lampert

Mark N. Lampert, President

INVESTMENT 10, L.L.C.

By: BVF Partners, L.P., its investment manager

By: BVF Inc., its general partner

By: /s/ Mark N. Lampert

Mark N. Lampert, President

BVF PARTNERS L.P.

By: BVF Inc., its general partner

By: /s/ Mark N. Lampert

Mark N. Lampert, President

BVF INC.

By: /s/ Mark N. Lampert

Mark N. Lampert, President

MARK N. LAMPERT

By: /s/ Mark N. Lampert

Mark N. Lampert