REPLIGEN CORP — Director's Dealing 2007

Sep 24, 2007

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: REPLIGEN CORP (RGEN)
CIK: 0000730272
Period of Report: 2007-09-20

Reporting Person: HERLIHY WALTER C (Director, PRESIDENT, CEO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2007-09-20	Common Stock	M	156277	$1.41	Acquired	554668	Direct
2007-09-20	Common Stock	F	52465	$4.20	Disposed	502203	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2007-09-20	Stock Option Right to Buy	$1.41	M	156277	Acquired	2008-04-29	Common Stock (156277)	Direct

Footnotes

F1: 100,000 shares exercisable at each of 4/29/1999, 4/29/2000, 4/29/2001 and 4/29/2002