X0508 4 2025-09-10 0 0001599298 Summit Therapeutics Inc. SMMT 0001055919 DUGGAN ROBERT W C/O SUMMIT THERAPEUTICS INC. 601 BRICKELL KEY DRIVE SUITE 1000 MIAMI FL 33131 1 1 1 0 Co-Chief Executive Officer 0 Common Stock 2025-09-10 4 P 0 333394 17.68 A 556088090 D Common Stock 2025-09-11 4 P 0 5000 18.07 A 556093090 D Common Stock 31000 I By Spouse Common Stock 10199776 I By the Shaun Zanganeh Irrevocable Trust, with the Spouse of Reporting Person as Trustee Common Stock 25457666 I By the Mahkam Zanganeh Revocable Trust, with the Spouse of Reporting Person as Trustee Common Stock 50000 I Immediate family member of Spouse The reported price in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $17.49 to $17.89 per share, inclusive. The Reporting Person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote. The Reporting Person disclaims beneficial ownership of these securities, except to the extent of his pecuniary interest therein, if any, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose /s/ Robert W. Duggan 2025-09-11