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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( 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 TO Commission File Number 001-39782 4D Molecular Therapeutics , Inc. ( Exact name of Registrant as specified in its Charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 5858 Horton Street # 455 Emeryville , CA ( Address of principal executive offices ) U 47-3506994 ( I.R.S. Employer Identification No. ) 94608 ( Zip Code ) Registrant's telephone number , including area code : ( 510 ) 505-2680 Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , par value $ 0.0001 per share Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the Registrant is 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 Trading Symbol ( s ) FDMT Name of each exchange on which registered The Nasdaq Global Select Market 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 , 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 . 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 registrant was not a public company as of June 30 , 2020 , the last business day of its most recently completed second fiscal quarter , and therefore , cannot calculate the aggregate market value of its voting and non - voting common equity held by non - affiliates as of such date . The registrant's Common Stock began trading on the Nasdaq Global Select Market on December 11 , 2020 . The number of shares of Registrant's Common Stock outstanding as of March 15 , 2021 was 26,692,879 . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive Proxy Statement relating to the 2021 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10 - K to the extent stated herein . The proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31 , 2020 .