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 *
Snodgres Jon
   2. Issuer Name and Ticker or Trading Symbol
REPLIGEN CORP [RGEN] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
CFO
(Last)
(First)
(Middle)
C/O REPLIGEN CORPORATION, 41 SEYON ST., BLDG 1, STE 100		 3. Date of Earliest Transaction (Month/Day/Year)
11/26/2018
(Street)

WALTHAM, MA 02453		 4. If Amendment, Date 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
(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 11/26/2018   M   11,445 A $ 26.2 32,344 D  
Common Stock 11/26/2018   M   4,000 A $ 24.5 36,344 D  
Common Stock 11/26/2018   M   6,055 A $ 32.4 42,399 D  
Common Stock 11/26/2018   M   10,253 A $ 26.05 52,652 D  
Common Stock 11/26/2018   S   31,753 (1) D $ 63.4874 (2) 20,899 D  

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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
Stock Option (Right to Buy) $ 26.2 11/26/2018   M     11,445   (3) 02/26/2025 Common Stock 11,445 $ 0 0 D  
Stock Option (Right to Buy) $ 24.5 11/26/2018   M     4,000   (4) 07/14/2024 Common Stock 4,000 $ 0 2,000 D  
Stock Option (Right to Buy) $ 32.4 11/26/2018   M     6,055   (5) 02/23/2027 Common Stock 6,055 $ 0 12,110 D  
Stock Option (Right to Buy) $ 26.05 11/26/2018   M     10,253   (6) 02/26/2026 Common Stock 10,253 $ 0 5,127 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Snodgres Jon
C/O REPLIGEN CORPORATION
41 SEYON ST., BLDG 1, STE 100
WALTHAM, MA 02453		       CFO  

Signatures

 /s/ Jeffrey P. Leduc (Attorney in Fact)   11/28/2018
**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) Sale of common stock was effective pursuant to a 10(b)5-1 trading plan adopted on September 19, 2018.
(2) $63.4874 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $63.18 to $64.71, 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.
(3) This option is currently exercisable.
(4) 2,000 shares vest and become exercisable on each of the following dates: 7/14/2015, 7/14/2016, 7/14/2017, 7/14/2018 and 7/14/2019.
(5) 6,055 shares vest and become exercisable on each of the following dates: 2/23/2018, 2/23/2019 and 2/23/2020.
(6) Shares vest and become exercisable as follows: 5,126 shares on 2/26/2017, 5,127 shares on 2/26/2018 and 5,127 shares on 2/26/2019.

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