<ACCESSION-NUMBER>0001193125-19-193992 <TYPE>424B5 <PUBLIC-DOCUMENT-COUNT>3 <FILING-DATE>20190715 <DATE-OF-FILING-DATE-CHANGE>20190715 <FILER> <COMPANY-DATA> <CONFORMED-NAME>REPLIGEN CORP <CIK>0000730272 <ASSIGNED-SIC>2836 <IRS-NUMBER>042729386 <STATE-OF-INCORPORATION>DE <FISCAL-YEAR-END>1231 </COMPANY-DATA> <FILING-VALUES> <FORM-TYPE>424B5 <ACT>33 <FILE-NUMBER>333-231098 <FILM-NUMBER>19955278 </FILING-VALUES> <BUSINESS-ADDRESS> <STREET1>41 SEYON STREET <STREET2>BUILDING 1, SUITE 100 <CITY>WALTHAM <STATE>MA <ZIP>02453 <PHONE>7814499560 </BUSINESS-ADDRESS> <MAIL-ADDRESS> <STREET1>41 SEYON STREET <STREET2>BUILDING 1, SUITE 100 <CITY>WALTHAM <STATE>MA <ZIP>02453 </MAIL-ADDRESS> </FILER>