Septerna, Inc.

Rule 10b5-1 Trading Plans

On October 20, 2025, Liz Bhatt, M.S., M.B.A., our President and Chief Operating Officer, adopted a pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 41,000 shares of our common stock (comprised of shares issuable upon the exercise of option awards previously granted to Ms. Bhatt), which plan expires at the earlier of January 15, 2027, and the date upon which all authorized transactions thereunder are completed. Ms. Bhatt’s trading plan is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

On October 31, 2025, Samira Shaikhly, our Chief People Officer, adopted a pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 109,206 shares of our common stock (comprised of shares issuable upon the exercise of option awards previously granted to Ms. Shaikhly), which plan expires at the earlier of October 30, 2026, and the date upon which all authorized transactions thereunder are completed. Ms. Shaikhly’s trading plan is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

During the three months ended December 31, 2025, no other directors or officers (as defined in Rule 16a-1(f) of the Exchange Act) of the Company adopted, modified, orterminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement” as each term is defined in Item 408 of Regulation S-K.