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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 ( Mark One ) × 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 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number : 001-36866 TRANSITION REPORT PURSUANT TO SECTION Delaware ( State or Other Jurisdiction of Incorporation or Organization ) Summit Therapeutics Inc. ( Exact Name of Registrant as Specified in its Charter ) One Broadway , 14th Floor Cambridge , MA ( Address of Principal Executive Offices ) FORM 10 - K Title of each class Common Stock , par value $ 0.01 per share ( 617 ) 514-7149 ( Registrant's Telephone Number , Including Area Code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) Large accelerated filer Non - accelerated filer SMMT 37-1979717 ( I.R.S. Employer Identification No. ) 02142 ( Zip Code ) Name of each exchange on which registered The Nasdaq Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No 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 No Indicate by check mark 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 posted 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 . ☐ 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 . 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 . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No The aggregate market value of the voting common stock held by non - affiliates based on the closing stock price on June 30 , 2020 , was $ 67.0 million . For purposes of this computation only , all executive officers and directors have been deemed affiliates . The number of outstanding shares of the registrant's common stock , par value $ 0.01 per share , as of March 24 , 2021 was 82,916,189 . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive Proxy Statement to be filed with the Securities and Exchange Commission within 120 days after registrant's fiscal year ended December 31 , 2020 are incorporated by reference into Part III of this report .