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( Mark one ) NOX UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K NO > 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 UNDER SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Canada ( State or other jurisdiction of incorporation or organization ) Commission file number 001-3200 APTOSE BIOSCIENCES INC . ( Exact name of registrant as specified in its charter ) Title of each class Common Shares , no par value ( I.R.S. Employer Identification No. ) 251 Consumers Road , Suite 1105 Toronto , Ontario , Canada M2J 4R3 ( Address of principal executive offices ) 647-479-9828 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) APTO 98-1136802 Name of each exchange on which registered Nasdaq Capital Market 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 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