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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 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 to Commission file number : 001-34962 Delaware ( State of Incorporation ) 5959 Horton Street , Suite 500 Emeryville , California ( Address of principal executive offices ) Title of each class Common Stock , $ 0.001 par value per share FORM 10 - K Large accelerated filer Non - accelerated filer ZOGENIX INC . 0 ( I.R.S. Employer Identification No. ) ( 510 ) 550-8300 ( Registrant's telephone number , including area code ) 20-5300780 Securities registered pursuant to Section 12 ( b ) of the Act : Trading symbol ZGNX Securities registered pursuant to Section 12 ( g ) of the Act : None 94608 ( Zip Code ) 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 Exchange 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 such files ) . Yes No Name of exchange registered The Nasdaq Global Market 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 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 0 0 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 USC . 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . < No > Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes □ As of June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , the aggregate market value of the registrant's common stock held by non - affiliates was approximately $ 1.5 billion . As of February 19 , 2021 , there were 55,735,558 shares of the registrant's common stock outstanding .