X0306 4 2023-03-13 0 0001060736 Seagen Inc. SGEN 0001206199 WELCH DANIEL G 21823 30TH DRIVE SE BOTHELL WA 98021 1 0 0 0 Common Stock 2023-03-13 4 M 0 5758 38.82 A 15407 D Common Stock 2023-03-13 4 M 0 283 39.94 A 15690 D Common Stock 2023-03-13 4 S 0 283 202.36 D 15407 D Common Stock 2023-03-13 4 M 0 1348 39.94 A 16755 D Common Stock 2023-03-13 4 S 0 1348 201.53 D 15407 D Common Stock 2023-03-13 4 M 0 7629 39.94 A 23036 D Common Stock 2023-03-13 4 S 0 7629 200.30 D 15407 D Common Stock 2023-03-13 4 S 0 2098 200.20 D 13309 D Common Stock 2023-03-13 4 S 0 214 201.53 D 13095 D Common Stock 2023-03-13 4 S 0 44 202.35 D 13051 D Common Stock 2023-03-14 4 S 0 74 200.00 D 12977 D Common Stock 2023-03-14 4 M 0 470 38.82 A 13447 D Common Stock 2023-03-14 4 S 0 470 200.00 D 12977 D Common Stock 2023-03-13 4 S 0 5758 200.06 D 7219 D Common Stock 2023-03-13 4 S 0 8210 200.20 D 25575 I by Trust Common Stock 2023-03-13 4 S 0 808 201.53 D 24767 I by Trust Common Stock 2023-03-13 4 S 0 173 202.36 D 24594 I by Trust Common Stock 2023-03-14 4 S 0 288 200.00 D 24306 I by Trust Non-Qualified Stock Option (right to buy) 38.82 2023-03-13 4 M 0 5758 0.00 D 2026-05-19 Common Stock 5758 3502 D Non-Qualified Stock Option (right to buy) 38.82 2023-03-14 4 M 0 470 0.00 D 2026-05-19 Common Stock 470 3032 D Non-Qualified Stock Option (right to buy) 39.94 2023-03-13 4 M 0 283 0.00 D 2025-05-14 Common Stock 283 8977 D Non-Qualified Stock Option (right to buy) 39.94 2023-03-13 4 M 0 1348 0.00 D 2025-05-14 Common Stock 1348 7629 D Non-Qualified Stock Option (right to buy) 39.94 2023-03-13 4 M 0 7629 0.00 D 2025-05-14 Common Stock 7629 0 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 $202.12 to $202.47. 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 $201.05 to $202.04. 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 $200.00 to $200.94. 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 $200.00 to $200.94. 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 $201.05 to $202.04. 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 $202.12 to $202.47. 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 $200.00 to $200.31. 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 5/14/16. By: /s/ Jennifer Prosba For: Daniel G. Welch 2023-03-16