X0306 4 2020-02-03 0 0001060736 SEATTLE GENETICS INC /WA SGEN 0001741836 DANSEY ROGER D 21823 30TH DRIVE SE BOTHELL WA 98021 0 1 0 0 Chief Medical Officer Common Stock 2020-02-03 4 S 0 727 108.51 D 108009 D Shares sold pursuant to a 10b5-1 arrangement to satisfy tax obligations arising out of the vesting of previously granted restricted stock units. Amount of securities beneficially owned following reported transactions includes restricted stock units subject to vesting and 125 shares acquired under the Amended and Restated 2000 Employee Stock Purchase Plan on January 31, 2020. By: /s/ For: Jean Liu 2020-02-05