REPLIGEN CORP — Director's Dealing 2009

Jul 9, 2009

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: REPLIGEN CORP (RGEN)
CIK: 0000730272
Period of Report: 2009-07-06

Reporting Person: BVF PARTNERS L P/IL (10% Owner, Indirect Beneficial Owner)
Reporting Person: BIOTECHNOLOGY VALUE FUND L P (Direct Beneficial Owner)
Reporting Person: BIOTECHNOLOGY VALUE FUND II LP (Direct Beneficial Owner)
Reporting Person: BVF INVESTMENTS LLC (Direct Beneficial Owner)
Reporting Person: LAMPERT MARK N (10% Owner, Indirect Beneficial Owner)
Reporting Person: BVF INC/IL (10% Owner, Indirect Beneficial Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2009-07-06	Common Stock	S	110800	$5.5157	Disposed	3106050	Direct
2009-07-06	Common Stock	S	76000	$5.5157	Disposed	3030050	Direct
2009-07-06	Common Stock	S	264000	$5.5157	Disposed	2766050	Direct
2009-07-07	Common Stock	S	1000	$5.50	Disposed	2765050	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	2765050	Indirect
Common Stock	2765050	Indirect
Common Stock	2765050	Indirect

Footnotes

F1: Units may represent aggregation of daily trade activity. Details regarding individual execution amounts and prices are available upon request.

F2: Shares directly beneficially owned by Biotechnology Value Fund, L.P. ("BVF")

F3: Shares directly beneficially owned by Biotechnology Value Fund II, L.P. ("BVF II")

F4: 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.

F5: The shares of Common Stock are indirectly beneficially owned by Partners. Partners is the general partner of BVF and BVF II and is the manager of BVFLLC.

F6: 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.

F7: Mark N. Lampert is the sole shareholder, sole director, and an officer of BVF Inc.