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( Mark One ) 冈 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 ☐ 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 ) to Commission File Number 001-38537 AVROBIO , INC . ( Exact name of registrant as specified in its charter ) One Kendall Square Building 300 , Suite 201 Cambridge , Massachusetts ( Address of principal executive offices ) Title of each class Common Stock , $ 0.0001 par value per share ( 617 ) 914-8420 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol AVRO Securities registered pursuant to Section 12 ( g ) of the Act : None 81-0710585 ( I.R.S. Employer Identification No. ) 02139 ( Zip Code ) Name of each exchange on which registered Nasdaq Global Select Market Yes ☐ No ☑ No ☑ Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . 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 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 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 Non - accelerated filer ☐ 冈 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 aggregate market value of the registrant's common stock held by non - affiliates of the registrant was approximately $ 533,953,963 as of June 30 , 2020 ( based on a closing price of $ 17.45 share as quoted by the Nasdaq Global Select 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 . The registrant had 41,622,060 shares of Common Stock , $ 0.0001 par value per share , outstanding as of March 9 , 2021 . 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 , 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 .