X0306 4 2017-03-31 0 0001060736 SEATTLE GENETICS INC /WA SGEN 0001361966 HIMES VAUGHN B 21823 30TH DRIVE SE BOTHELL WA 98021 0 1 0 0 Chief Technical Officer Common Stock 2017-03-31 4 M 0 10000 9.23 A 161283 D Common Stock 2017-03-31 4 S 0 10000 62.7527 D 151283 D Non-Qualified Stock Option (right to buy) 9.23 2017-03-31 4 M 0 10000 0.0 D 2019-04-30 Common Stock 10000 13164 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. Reflects sales of ordinary shares executed in multiple transactions at prices ranging from $62.27 to $63.04. The price reported reflects the weighted average sale price. The Reporting Person hereby undertakes to provide upon request by the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the sales were effected. Amount of securities beneficially owned following reported transactions includes restricted stock units subject to vesting. Includes 272 shares acquired under the Amended & Restated 2000 Employee Stock Purchase Plan on January 31, 2017. Shares vested at a rate of 25% on 4/1/10 and monthly thereafter until all the shares were fully vested on 4/1/13. By: /s/ Jean Liu For: Vaughn B. Himes 2017-04-03