X0306 4 2020-12-22 0 0000882361 Aptose Biosciences Inc. APTO 0001761449 Whitehead Warren C/O APTOSE BIOSCIENCES INC. 251 CONSUMERS ROAD, SUITE 1105 TORONTO A6 M2J 4R3 ONTARIO, CANADA 1 0 0 0 Common Shares 2020-12-22 4 M 0 20000 2.01 A 60000 D Common Shares 2020-12-22 4 S 0 10000 4.01 D 50000 D Common Shares 2020-12-22 4 S 0 10000 4.11 D 40000 D Director Stock Option (Right to Buy) 2.01 2020-12-22 4 M 0 20000 0 D 2019-01-02 2029-01-02 Common Shares 40000 20000 D Converted from Canadian exercise price of C$2.60 using an exchange rate of C$1.2908 = US$1.00. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from C$5.16 to C$5.1924, inclusive. The reporting person undertakes to provide to Aptose Biosciences, Inc., any security holder of Aptose Biosciences, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. The weighted average sales price reported above was converted from the Canadian weighted average sales price of C$5.1745 using an exchange rate of C$1.2908 = US$1.00. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from C$5.2979 to C$5.3111, inclusive. The reporting person undertakes to provide to Aptose Biosciences, Inc., any security holder of Aptose Biosciences, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. The weighted average sales price reported above was converted from the Canadian weighted average sales price of C$5.3003 using an exchange rate of C$1.2908 = US$1.00. The options were granted on 1/2/2019 and fully vested on 1/2/2020. /s/ Janet Clennett as attorney-in-fact for Warren Whitehead 2020-12-23