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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 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM Commission File Number 001-38096 Delaware ( State or other jurisdiction of incorporation or organization ) Title of each class Common Stock $ .0001 par value FORM 10 - K G1 THERAPEUTICS , INC . ( Exact name of Registrant as specified in its Charter ) ■ ΤΟ 700 Park Offices Drive , Suite 200 Research Triangle Park , NC 27709 ( Address of principal executive offices including zip code ) Registrant's telephone number , including area code : ( 919 ) 213-9835 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol GTHX 26-3648180 ( I.R.S. Employer Identification No. ) Name of each exchange on which registered The Nasdaq Stock Market 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 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 check mark whether the Registrant has submitted elec y 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 X Accelerated filer Non - 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 and non - voting common equity held by non - affiliates of the Registrant as of June 30 , 2020 , the last business day of the Registrant's most recently completed second fiscal quarter , was $ 820.8 million based on the closing price of the shares of common stock on The Nasdaq Stock Market on that date . The number of shares of the Registrant's Common Stock outstanding as of February 22 , 2021 was 41,959,379 . Documents Incorporated by Reference