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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 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR Delaware ( State or other jurisdiction of incorporation or organization ) Title of each class For the transition period from 3201 Carnegie Avenue , Cleveland , Ohio ( Address of principal executive offices ) Commission file number 001-33876 Athersys , Inc. ( Exact name of registrant as specified in its charter ) to Large accelerated filer □ Non - accelerated filer Registrant's telephone number , including area code ( 216 ) 431-9900 Securities registered pursuant to Section 12 ( b ) of the Act : Common Stock , par value $ 0.001 per : share Trading Symbol ATHX Securities registered pursuant to Section 12 ( g ) of the Act : None 20-4864095 ( I.R.S. Employer Identification No. ) 44115-2634 ( Zip Code ) Name of each exchange on which registered Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No X Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Securities Exchange Act of 1934. Yes No X 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 The NASDAQ Stock Market LLC 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 , 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 . Documents Incorporated By Reference . 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 is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No 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 . The aggregate market value at June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , of shares of the registrant's common stock ( based upon the closing price per share of $ 2.76 of such stock as quoted on the NASDAQ Capital Market on such date ) held by non - affiliates of the registrant was approximately $ 464.4 million . The registrant had 215,244,507 shares of common stock outstanding on March 19 , 2021 .