X0305 4 2012-05-24 0 0000730272 REPLIGEN CORP RGEN 0001263366 RYAN THOMAS F JR C/O REPLIGEN CORPORATION 41 SEYON STREET, BLDG 1, STE 100 WALTHAM MA 02453 1 0 0 0 Common Stock 2012-05-24 4 A 0 11038 0 A 61038 D Mr. Ryan was awarded 11,038 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 24, 2013. 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. William J. Kelly (Attorney in Fact) 2012-06-20