X0306 4 2021-05-14 0 0000730272 REPLIGEN CORP RGEN 0001733143 KURIYEL RALF C/O REPLIGEN CORPORATION 41 SEYON ST., BLDG 1, STE 100 WALTHAM MA 02453 0 1 0 0 Senior VP, R&D Common Stock 2021-05-14 4 S 0 710 172.29 D 24555 D Sale of shares in the open market to cover tax liability resulting from the release of restricted stock units. $172.29 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $172.26 to $172.40, 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. Exhibit 24.1: Power of Attorney /s/ Kimberly Brown (Attorney in Fact) 2021-05-18