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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 ( Mark one ) ☑ ☐ 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 EXCHANGE ACT OF 1934 For the transition period from Commission file number : 000-24477 to Diffusio₂n Pharmaceuticals Inc. Diffusion Pharmaceuticals Inc. Delaware ( Exact Name of Registrant as specified in its Charter ) ( State or Other Jurisdiction of Incorporation or Organization ) 1317 Carlton Avenue , Suite 200 Charlottesville , VA ( Address of Principal Executive Offices ) ( 434 ) 220-0718 30-0645032 ( I.R.S. Employer Identification No ) 22902 ( Zip Code ) ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of Each Class Common Stock , par value $ 0.001 per share Trading Symbol DFFN Name of Each Exchange on Which Registered The Nasdaq Capital Market No ☑ 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 □ 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 . 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 □