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Table of Contents ☑ ㅁ 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 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 001-37368 to ADAPTIMMUNE THERAPEUTICS PLC England and Wales ( Exact name of Registrant as specified in its charter ) ( State or other jurisdiction of incorporation or organization ) 60 Jubilee Avenue , Milton Park Abingdon , Oxfordshire OX14 4RX United Kingdom ( Address of principal executive offices ) Not Applicable ( I.R.S. Employer Identification No. ) ( 44 ) 1235 430000 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Trading Symbol ( s ) American Depositary Shares , each representing 6 Ordinary Shares , par value £ 0.001 per share ADAP 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 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 and post 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 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 Act ) . □ Yes > No State the aggregate market value of the voting and non - voting common equity held by non - affiliates computed by reference to the price at which the common equity was last sold , or the average bid and asked price of such common equity , as of the last business day of the registrant's most recently completed second fiscal quarter . $ 1,359,787,192 . Indicate the number of shares outstanding of each of the issuer's classes of common stock , as of the latest practicable date . As of February 24 , 2021 the number of outstanding ordinary shares , par value £ 0.001 per share , of the Registrant is 930,827,670 . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive Proxy Statement for the 2021 Annual Meeting of Shareholders to be filed with the U.S. Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10 - K are incorporated by reference in Part III , Items 10-14 of this Annual Report on Form 10 - K .