REPLIGEN CORP — Director's Dealing 2013

May 6, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: REPLIGEN CORP (RGEN)
CIK: 0000730272
Period of Report: 2013-05-03

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

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-03	Common Stock	M	50000	$3.05	Acquired	564916	Direct
2013-05-03	Common Stock	F	17078	$8.93	Disposed	547838	Direct
2013-05-03	Common Stock	M	80000	$5.87	Acquired	627838	Direct
2013-05-03	Common Stock	F	52587	$8.93	Disposed	575251	Direct
2013-05-03	Common Stock	M	20000	$3.33	Acquired	595251	Direct
2013-05-03	Common Stock	F	7458	$8.93	Disposed	587793	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-05-03	Stock Option (Right to Buy)	$3.05	M	50000	Disposed	2014-04-30	Common Stock (50000)	Direct
2013-05-03	Stock Option (Right to Buy)	$5.87	M	80000	Disposed	2018-06-06	Common Stock (80000)	Direct
2013-05-03	Stock Option (Right to Buy)	$3.33	M	20000	Disposed	2020-07-15	Common Stock (20000)	Direct

Footnotes

F1: Payment made via forfeiture of 17,078 shares of Common Stock valued at the Closing Price of $8.93 on May 3, 2013.

F2: Payment made via forfeiture of 52,587 shares of Common Stock valued at the Closing Price of $8.93 on May 3, 2013.

F3: Payment made via forfeiture of 7,458 shares of Common Stock valued at the Closing Price of $8.93 on May 3, 2013.