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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( Mark One ) × ANNUAL REPORT UNDER 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 to Commission File No. 000-16929 SOLIGENIX , INC . ( Exact name of registrant as specified in its charter ) ( State or other jurisdiction of incorporation or organization ) 29 EMMONS DRIVE , SUITE B - 10 PRINCETON , NJ 41-1505029 ( I.R.S. Employer Identification Number ) ( Address of principal executive offices ) Title of each class ( 609 ) 538-8200 ( Registrant's telephone number , including area code ) 08540 ( Zip Code ) Securities registered under Section 12 ( b ) of the Exchange Act : Common Stock , par value $ 0.01 per share Common Stock Purchase Warrants Trading Symbol ( s ) SNGX SNGXW Name of each exchange on which registered Securities registered under Section 12 ( g ) of the Exchange Act : None The Nasdaq Capital Market The Nasdaq Capital Market 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 such files ) . Yes No □ Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , or a smaller reporting company . See the definition of “ large accelerated filer ” , “ accelerated filer ” and “ smaller reporting company ” in Rule 12b - 2 of the Exchange Act . ( Check one ) : Large accelerated filer ☐ Non - accelerated filer ☑ 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 common stock held by non - affiliates of the registrant was $ 57,299,617 ( assuming , for this purpose , that executive officers , directors and holders of 10 % or more of the common stock are affiliates ) , based on the closing price of the registrant's common stock as reported on The Nasdaq Capital Market on June 30 , 2020 . On March 23 , 2021 , there were 40,020,461 shares of the registrant's common stock outstanding . DOCUMENTS INCORPORATED BY REFERENCE : None .