Amended Statement of Beneficial Ownership (3/a)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^*

KURIYEL RALF

2. Date of Event Requiring Statement (MM/DD/YYYY) 2/28/2018

3. Issuer Name and Ticker or Trading Symbol

REPLIGEN CORP [RGEN]

(Last) (First) (Middle)

C/O REPLIGEN CORPORATION, 41 SEYON ST, BLDG 1, STE 100

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

_____ Director _____ 10% Owner
___ X ___ Officer (give title below) _____ Other (specify below)
Senior VP, R&D /

(Street)

WALTHAM, MA 02453

(City) (State) (Zip)

5. If Amendment, Date Original Filed (MM/DD/YYYY)

3/5/2018

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 Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	5962	D

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivate Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Stock Option (Right to Buy)	⁽¹⁾	12/14/2026	Common Stock	10000	$33.05	D

Explanation of Responses:
(1)	This option shall vest as follows: 2,000 shares shall vest on 12/14/2017; 12/14/2018; 12/14/2019; 12/14/2020 and on 12/14/2021.

Remarks:
This Form 3/A amends a Form 3 filed on 3/5/18 to attach the Power of Attorney on Exhibit 24.1 that was not provided in the original filing.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
KURIYEL RALF C/O REPLIGEN CORPORATION 41 SEYON ST, BLDG 1, STE 100 WALTHAM, MA 02453			Senior VP, R&D

Signatures
/s/ Jeffrey P. Leduc (Attorney in Fact)		3/6/2018
^** 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 5(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).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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