X0407 4 2023-04-03 0 0001060736 Seagen Inc. SGEN 0001206199 WELCH DANIEL G 21823 30TH DRIVE SE BOTHELL WA 98021 1 0 0 0 0 Common Stock 2023-04-03 4 M 0 995 38.82 A 7894 D Common Stock 2023-04-03 4 S 0 995 200.11 D 6899 D Common Stock 2023-04-03 4 M 0 5680 66.60 A 12579 D Common Stock 2023-04-03 4 S 0 5680 200.71 D 6899 D Common Stock 2023-04-03 4 M 0 3575 66.60 A 10474 D Common Stock 2023-04-03 4 S 0 3575 201.59 D 6899 D Common Stock 2023-04-03 4 M 0 5 66.60 A 6904 D Common Stock 2023-04-03 4 S 0 5 202.49 D 6899 D Common Stock 2023-04-03 4 M 0 7158 56.77 A 14057 D Common Stock 2023-04-03 4 S 0 7158 202.51 D 6899 D Common Stock 2023-04-03 4 M 0 112 56.77 A 7011 D Common Stock 2023-04-03 4 S 0 112 203.05 D 6899 D Common Stock 2023-04-03 4 S 0 817 200.45 D 6082 D Common Stock 2023-04-03 4 S 0 851 201.51 D 5231 D Common Stock 2023-04-03 4 S 0 1082 202.54 D 4149 D Common Stock 2023-04-03 4 S 0 3124 200.45 D 19936 I By Trust Common Stock 2023-04-03 4 S 0 3317 201.51 D 16619 I By Trust Common Stock 2023-04-03 4 S 0 4284 202.54 D 12335 I By Trust Non-Qualified Stock Option (right to buy) 38.82 2023-04-03 4 M 0 995 0.00 D 2026-05-19 Common Stock 995 0 D Non-Qualified Stock Option (right to buy) 66.60 2023-04-03 4 M 0 9260 0.00 D 2027-05-18 Common Stock 9260 0 D Non-Qualified Stock Option (right to buy) 56.77 2023-04-03 4 M 0 7270 0.00 D 2028-05-18 Common Stock 7270 1990 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 $200.10 to $200.43. 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 $200.27 to $201.26. 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 $201.28 to $202.03. 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 $202.32 to $202.60. 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 $201.92 to $202.91. 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 $200.10 to $201.07. 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 $201.10 to $202.05. 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 $202.11 to $203.05. 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. Options were fully vested on 5/19/17. Options were fully vested on 5/18/18. Options were fully vested on 5/18/19. By: /s/ Jennifer Prosba For: Daniel G. Welch 2023-04-05