X0306 4 2020-05-13 0 0000730272 REPLIGEN CORP RGEN 0001283576 BARTHELEMY NICOLAS C/O REPLIGEN CORPORATION 41 SEYON ST., BLDG 1, STE 100 WALTHAM MA 02453 1 0 0 0 Common Stock 2020-05-13 4 A 0 527 0.00 A 3564 D Stock Option (Right to Buy) 128.18 2020-05-13 4 A 0 1285 0.00 A 2021-05-13 2030-05-13 Common Stock 1285 1285 D Mr. Barthelemy was awarded 527 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 13, 2021. The restricted stock unit may be settled only by delivering shares of Repligen Corporation's Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance. Award vests in full one year from grant date on May 13, 2021. /s/ Jeffrey P. Leduc (Attorney in Fact) 2020-05-19