X0306 4 2020-12-07 0 0001060736 Seagen Inc. SGEN 0001361966 HIMES VAUGHN B 21823 30TH DRIVE SE BOTHELL WA 98021 0 1 0 0 Chief Technical Officer Common Stock 2020-12-07 4 M 0 2207 45.3 A 189036 D Common Stock 2020-12-07 4 M 0 2554 39.15 A 191590 D Common Stock 2020-12-07 4 M 0 8000 15.46 A 199590 D Common Stock 2020-12-07 4 S 0 1554 180.41 D 198036 D Common Stock 2020-12-07 4 S 0 2554 181.48 D 195482 D Common Stock 2020-12-07 4 S 0 3692 182.43 D 191790 D Common Stock 2020-12-07 4 S 0 200 183.26 D 191590 D Common Stock 2020-12-08 5 G 0 45538 0.0 D 146052 D Common Stock 2020-12-08 5 G 0 8131 0.0 D 137921 D Common Stock 2020-12-08 5 G 0 8131 0.0 D 129790 D Common Stock 2020-12-08 5 G 0 45538 0.0 A 45538 I by Trust Common Stock 2020-12-08 5 G 0 8131 0.0 A 53669 I by Trust Incentive Stock Option (right to buy) 39.15 2020-12-07 4 M 0 2554 0.0 D 2025-08-25 Common Stock 2554 0 D Incentive Stock Option (right to buy) 45.3 2020-12-07 4 M 0 2207 0.0 D 2026-08-27 Common Stock 2207 0 D Non-Qualified Stock Option (right to buy) 15.46 2020-12-07 4 M 0 8000 0.0 D 2021-08-24 Common Stock 8000 22697 D Amount of securities beneficially owned following reported transactions includes restricted stock units subject to vesting. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. Reflects sales of common stock executed in multiple transactions at prices ranging from $179.90 to $180.89. 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. Reflects sales of common stock executed in multiple transactions at prices ranging from $180.90 to $181.89. 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. Reflects sales of common stock executed in multiple transactions at prices ranging from $182.06 to $182.92. 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. Reflects sales of common stock executed in multiple transactions at prices ranging from $183.23 to $183.29. 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. On December 8, 2020, the reporting person transferred 45,538 shares of common stock to an irrevocable trust of which the reporting person's spouse is the trustee. Members of the reporting person's immediate family are the sole beneficiaries of the trust. On December 8, 2020, the reporting person transferred 8,131 shares of common stock to an irrevocable trust of which the reporting person's spouse is the trustee. Members of the reporting person's immediate family are the sole beneficiaries of the trust. Options vested at a rate of 25% on 8/25/16 and monthly thereafter until all the shares were fully vested on 8/25/19. Options vested at a rate of 25% on 8/27/17 and monthly thereafter until all the shares were fully vested on 8/27/20. Options vested at a rate of 25% on 8/24/12 and monthly thereafter until all the shares were fully vested on 8/24/15. By: /s/ Jean Liu For: Vaughn B. Himes 2020-12-09