X0306 4 2018-05-16 0 0000730272 REPLIGEN CORP RGEN 0001046351 COOPER GLENN L MD C/O REPLIGEN CORPORATION 41 SEYON STREET, BLDG 1, STE 100 WALTHAM MA 02453 1 0 0 0 Common Stock 2018-05-16 4 A 0 1486 0 A 39786 D Stock Option (Right to Buy) 42.07 2018-05-16 4 A 0 3304 0 A 2019-05-16 2028-05-16 Common Stock 3304 3304 D Dr. Cooper was awarded 1,486 Restricted Stock Units. Each Restricted Stock Unit represents a contingent right to receive one share of Repligen Corporation's Common Stock. The Restricted Stock Units vest on May 16, 2019. The Restricted Stock Units may be settled only by delivering shares of Repligen Corporation's Common Stock, and thus, the grant is being reported in Table 1 as allowed per SEC guidance. Award vests in full one year from grant date on May 16, 2019. /s/ Jeffrey P. Leduc (Attorney in Fact) 2018-05-17