Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
EDDLEMAN ROY T
   2. Issuer Name and Ticker or Trading Symbol
REPLIGEN CORP [RGEN] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
C/O TROYGOULD PC, 1801 CENTURY PARK E., 16TH FLOOR		 3. Date of Earliest Transaction (Month/Day/Year)
05/08/2018
(Street)

LOS ANGELES, CA 90067		 4. If Amendment, Date Original Filed(Month/Day/Year)
05/09/2018		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
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)
Code V Amount (A) or (D) Price
Common Stock 05/08/2018   S   49,227 D $ 40.77 (1) 850,773 I As trustee (2)
Common Stock 05/08/2018   S   25,000 D $ 40.66 (3) 455,000 I As trustee (4)
Common Stock 05/09/2018   S   20,773 D $ 40.52 (5) 830,000 I As trustee (2)
Common Stock 05/09/2018   S   25,000 D $ 40.37 (6) 430,000 I As trustee (4)
Common Stock               357,518 D (7)  
Common Stock               3,044,826 I As trustee (8)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Underlying Securities
(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 of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
EDDLEMAN ROY T
C/O TROYGOULD PC
1801 CENTURY PARK E., 16TH FLOOR
LOS ANGELES, CA 90067		     X    

Signatures

 /s/ Istvan Benko, Attorney-in-fact for Roy T. Eddleman   05/10/2018
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(1) The price is a weighted-average price. The shares were sold in multiple transactions at prices ranging from $40.5515 to $41.0078, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the SEC, upon request, full information regarding the number of shares sold at each price within the price ranges set forth in this footnote (1) and in footnotes (3) - (5) to this Form 4.
(2) The shares shown are held, of record, by a charitable remainder unitrust of which the reporting person is the sole trustee and, as such, has investment and voting control over such shares, and is a lifetime beneficiary. The reporting person disclaims as beneficial ownership of the shares except to the extent of his pecuniary interest therein.
(3) The price is a weighted-average price. The shares were sold in multiple transactions at prices ranging from $40.5607 to $41.0107, inclusive.
(4) The shares shown are held, of record, by another charitable remainder unitrust of which the reporting person is the sole trustee and, as such, has investment and voting control over such shares, and is a lifetime beneficiary. The reporting person disclaims as beneficial ownership of the shares except to the extent of his pecuniary interest therein.
(5) The price is a weighted-average price. The shares were sold in multiple transactions at prices ranging from $40.2401 to $40.70, inclusive.
(6) The price is a weighted-average price. The shares were sold in multiple transactions at prices ranging from $40.2102 to $40.6022, inclusive.
(7) The shares shown are held for the benefit of the reporting person in a 15-month escrow account established in connection with the acquisition of Spectrum, Inc. by the issuer on August 1, 2017 and are subject to potential indemnification claims of the issuer relating to the acquisition.
(8) The shares shown are held of record by the Roy T. Eddleman Living Trust UAD 8-7-2000, of which the reporting person is the sole trustee, and as such, has investment and voting control over such shares.

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