X0508 4 2023-11-09 0 0001060736 Seagen Inc. SGEN 0001361966 HIMES VAUGHN B 21823 30TH DRIVE SE BOTHELL WA 98021 0 1 0 0 Chief Technical Officer 0 Common Stock 2023-11-09 4 S 0 8567 213.31 D 42792 D Common Stock 2023-11-09 4 S 0 218 213.88 D 42574 D Common Stock 119471 I by Trust The sales reported in this Form 4 were effected pursuant to a written plan, entered into on November 29, 2022, that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). Reflects sales of common stock executed in multiple transactions at prices ranging from $212.79 to $213.72. 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. By: Vaughn B Himes For: /s/ Jennifer Prosba 2023-11-13