X0306 4 2018-03-15 0 0001060736 SEATTLE GENETICS INC /WA SGEN 0001361966 HIMES VAUGHN B 21823 30TH DRIVE SE BOTHELL WA 98021 0 1 0 0 See Remarks Common Stock 2018-03-15 4 M 0 5000 12.00 A 169906 D Common Stock 2018-03-15 4 S 0 4800 58.09 D 165106 D Common Stock 2018-03-15 4 S 0 200 58.86 D 164906 D Non-Qualified Stock Option (right to buy) 12.00 2018-03-15 4 M 0 5000 0.00 D 2020-08-27 Common Stock 5000 51498 D Amount of securities beneficially owned following reported transactions includes restricted stock units subject to vesting and 285 shares acquired under the Amended and Restated 2000 Employee Stock Purchase Plan on January 31, 2018. 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 $57.64 to $58.61. 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. Shares vested at a rate of 25% on 8/27/2011 and monthly thereafter until all the shares were fully vested on 8/27/2014. Chief Technical Officer 5500 - Technical Operations /s/ Jean Liu 2018-03-19