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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Year Ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number 000-51531 SUNESIS PHARMACEUTICALS INC . ( Exact name of registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 395 Oyster Point Boulevard , Suite 400 South San Francisco , California 94080 ( Address of principal executive offices , including zip code ) ( 650 ) 266-3500 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol : SNSS None . Title of Each Class : Common Stock , par value $ 0.0001 per share 94-3295878 ( I.R.S. Employer Identification Number ) Name of Each Exchange on Which Registered : The Nasdaq Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act : None ( Title of Class ) No X 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 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 ( the " Exchange Act " ) during the preceding 12 months ( or for such 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 , accelerated filer , a non - accelerated filer , a smaller reporting company , or emerging growth company . See 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 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 Exchange Act Rule 12b - 2 . ) Yes No The aggregate market value of common stock held by non - affiliates of the registrant , based on the closing sales price for such stock on June 30 , 2020 , as reported by The Nasdaq Stock Market , was approximately $ 28,910,000 . The calculation of the aggregate market value of voting and non - voting stock excludes certain shares of the registrant's common stock held by current executive officers , directors and stockholders that the registrant has concluded are affiliates of the registrant . Exclusion of such shares should not be construed to indicate that any such person possesses the power , direct or indirect , to direct or cause the direction of the management or policies of the registrant or that such person is controlled by or under common control with the registrant . The total number of shares outstanding of the registrant's common stock , $ 0.0001 par value per share , as of February 18 , 2021 , was approximately 18,108,000 . DOCUMENTS INCORPORATED BY REFERENCE