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Table of Contents X UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 000-14656 Delaware ( State or other jurisdiction of incorporation or organization ) FORM 10 - K REPLIGEN CORPORATION ( Exact name of registrant as specified in its charter ) 41 Seyon Street , Bldg . 1 , Suite 100 Waltham , MA ( Address of principal executive offices ) Title of each class Common Stock , par value $ 0.01 per share 04-2729386 ( I.R.S. Employer Identification No. ) 0 Registrant's telephone number , including area code : ( 781 ) 250-0111 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) RGEN Securities registered pursuant to Section 12 ( g ) of the Act : None 02453 ( Zip Code ) Name of each exchange on which registered The Nasdaq Global Select Market No □ . No > . Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes > Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes Indicate by checkmark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No . Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No □ . Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer Accelerated filer Smaller reporting company Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Yes No □ . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . No > . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes The aggregate market value of the voting and non - voting common equity held by non - affiliates as of June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , was $ 5,711,511,345 . The number of shares of the registrant's common stock outstanding as of February 19 , 2021 was 54,771,343 . Documents Incorporated By Reference The registrant intends to file a proxy statement pursuant to Regulation 14A within 120 days of the end of the fiscal year ended December 31 , 2020 . Portions of such proxy statement are incorporated by reference into Part III of this Annual Report on Form 10 - K . 0 0 0