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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 Delaware ( State or other jurisdiction of incorporation or organization ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , par value $ 0.0001 per share Large accelerated filer Non - accelerated filer to Commission File No. 001-38359 Adicet Bio , Inc. ( Exact name of registrant as specified in its charter ) ( Address , including zip code , and telephone number , including area code , of registrant's principal executive offices ) 500 Boylston Street , 13th Floor Boston , MA 02116 ( 857 ) 315-5528 ■ Trading Symbol ( s ) ACET 81-3305277 ( I.R.S. Employer Identification No. ) Securities registered pursuant to Section 12 ( g ) of the Act : None Yes > No 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 . 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 Name of each exchange on which registered The Nasdaq Global 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 . 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 As of June 30 , 2020 , the aggregate market value of the registrant's voting and non - voting common stock held by non - affiliates was approximately $ 40.0 million based on a closing price of $ 15.05 per share as quoted by The Nasdaq Global Market as of such date . In determining the market value of non - affiliate common stock , shares of the registrant's common stock beneficially owned by officers , directors and affiliates have been excluded . This determination of affiliate status is not necessarily a conclusive determination for other purposes . As of March 10 , 2021 , there were 31,780,347 shares of common stock , $ 0.0001 par value per share , outstanding . DOCUMENTS INCORPORATED BY REFERENCE Part III of this Annual Report on Form 10 - K incorporates by reference certain information from the registrant's definitive Proxy Statement for its 2021 annual meeting of shareholders , scheduled to be held on April 27 , 2021 which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant's fiscal year end of December 31 , 2020. Except with respect to information specifically incorporated by reference in this Form 10 - K , the Proxy Statement is not deemed to be filed as part of this Form 10 - K .