SEC FORM 4

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

HERLIHY WALTER C

(Last)

(First)

(Middle)

C/O REPLIGEN CORPORATION

41 SEYON STREET SUITE 100, BUILDING 1

(Street)

WALTHAM

02453

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
REPLIGEN CORP [ RGEN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	PRESIDENT, CEO

3. Date of Earliest Transaction (Month/Day/Year)
05/03/2013

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/03/2013	05/03/2013	M		50,000	A	$3.05	564,916	D
Common Stock	05/03/2013	05/03/2013	F		17,078⁽¹⁾	D	$8.93	547,838	D
Common Stock	05/03/2013	05/03/2013	M		80,000	A	$5.87	627,838	D
Common Stock	05/03/2013	05/03/2013	F		52,587⁽²⁾	D	$8.93	575,251	D
Common Stock	05/03/2013	05/03/2013	M		20,000	A	$3.33	595,251	D
Common Stock	05/03/2013	05/03/2013	F		7,458⁽³⁾	D	$8.93	587,793	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (Right to Buy)	$3.05⁽¹⁾	05/03/2013	05/03/2013	M			50,000⁽¹⁾	04/23/2005	04/30/2014	Common Stock	50,000	$0	235,000	D
Stock Option (Right to Buy)	$5.87⁽²⁾	05/03/2013	05/03/2013	M			80,000⁽²⁾	06/06/2009	06/06/2018	Common Stock	80,000	$0	155,000	D
Stock Option (Right to Buy)	$3.33⁽³⁾	05/03/2013	05/03/2013	M			20,000⁽³⁾	07/15/2011	07/15/2020	Common Stock	20,000	$0	135,000	D

Explanation of Responses:

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

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

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

Remarks:

	William J. Kelly (Attorney in Fact)	05/06/2013
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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