REPLIGEN CORP — Director's Dealing 2013

May 8, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: REPLIGEN CORP (RGEN)
CIK: 0000730272
Period of Report: 2013-05-07

Reporting Person: Kelly William J (Chief Accounting Officer)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-07	Common Stock	M	20000	$4.82	Acquired	20000	Direct
2013-05-07	Common Stock	S	20000	$9.1367	Disposed	0	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-05-07	Stock Option (Right to Buy)	$4.82	M	20000	Disposed	2018-03-31	Common Stock (20000)	Direct

Footnotes

F1: $9.1367 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.12 to $9.15, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.