As filed with the Securities and Exchange Commission on June 16, 2023 Registration No. 333-________ UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Aptose Biosciences U.S. Inc. Unit 120, 12770 High Bluff Drive San Diego, California 92130 (858) 926-2730 (Name, address, including zip code, and telephone number, including area code, of agent for service) FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 APTOSE BIOSCIENCES INC. (Exact Name of Registrant As Specified In Its ...