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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 ΤΟ 89bio , Inc. ( Exact name of Registrant as specified in its Charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 142 Sansome Street , Second Floor Commission File Number 001-39122 San Francisco , California 94104 ( Address of principal executive offices ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common stock , par value $ 0.001 per share Large accelerated filer Non - accelerated filer Registrant's telephone number , including area code : ( 415 ) 500-4614 36-4946844 ( I.R.S. Employer Identification No. ) Trading Symbol ( s ) ETNB 94104 ( Zip Code ) Name of each exchange on which registered Nasdaq Global Market 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 15 ( d ) of the Act . YESNO > 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 , 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 > The aggregate market value of the voting and non - voting common equity held by non - affiliates of the Registrant as of June 30 , 2020 , the last business day of the Registrant's most recently completed second fiscal quarter , was approximately $ 72,707,052 , based on the closing price on The Nasdaq Global Market reported for such date . Shares of common stock held by each officer and director and by each person who is known to own 10 % or more of the outstanding common stock have been excluded in that such persons may be deemed to be affiliates of the Registrant . This determination of affiliate status is not necessarily a conclusive determination for other purposes . As of March 1 , 2021 , there were 19,946,426 shares of the Registrant's common stock outstanding . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive proxy statement relating to its 2021 Annual Meeting of Stockholders , to be held on or about June 2 , 2021 , are incorporated by reference into Part III of this Annual Report on Form 10 - K where indicated . Such proxy statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates .