X0306 4 2017-09-18 0 0001412067 Cascadian Therapeutics, Inc. CASC 0001701440 Walker Luke Nathaniel C/O CASCADIAN THERAPEUTICS, INC. 2601 4TH AVE., SUITE 500 SEATTLE WA 98121 0 1 0 0 SVP, Clinical Development Stock Option (right to buy) 3.99 2017-09-18 4 A 0 50000 0.00 A 2027-09-18 Common Stock 50000 50000 D Restricted Share Unit (RSU) 2017-09-18 4 A 0 12000 0.00 A 2021-09-18 Common Stock 12000 12000 D The option vests and is exercisable at the rate of 1/4th of the total shares on September 18, 2018 and then 1/48th of the total shares vest and are exercisable monthly thereafter, with 100% vested and exercisable on September 18, 2021, subject to the holder's continued employment with the issuer on each vesting date. Approximately 67% of each RSU represents a contingent right to receive approximately 0.67 share of the issuer's Common Stock upon vesting and approximately 33% represents a contingent right to receive cash upon vesting, which cash will be used to facilitate the holder's satisfaction of U.S. federal tax obligations in connection with the vesting of the RSUs. Twenty-five percent of the shares underlying the RSU vest on each of September 18, 2018, September 18, 2019, September 18, 2020 and September 18, 2021, subject to the holder's continued employment with the issuer on each vesting date. /s/ Julia M. Eastland as attorney-in-fact for Luke N. Walker 2017-09-20