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X : UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , DC 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 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES ACT OF 1934 For the transition period from to Nevada Commission File Number : 001-12584 SYNTHETIC BIOLOGICS , INC . ( Exact Name of Registrant as Specified in Its Charter ) ( State or Other Jurisdiction of Incorporation or Organization ) 9605 Medical Center Drive , Ste . 270 Rockville , MD ( Address of Principal Executive Offices ) 13-3808303 ( I.R.S. Employer Identification Number ) Registrant's telephone number , including area code : ( 301 ) 417-4364 20850 ( Zip Code ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Trading Symbol ( s ) Common Stock SYN Name of each exchange on which registered NYSE American 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 X 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 X Indicate by check mark whether the issuer : ( 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 X 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 ( section 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 X 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 . ( Check one ) : Large Accelerated Filer Accelerated Filer Non - accelerated Filer X Smaller Reporting Companyx