Septerna, Inc.

Item 5. Other Information.

(c) Rule 10b5-1 Trading Plans

On July 13, 2026, Alan Ezekowitz, M.D., D.Phil., a member of ourboard of directors, adopted a pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 100,000 shares of common stock held directly, which plan expires at the earlier of July 13, 2027 and the date upon which all authorized transactions thereunder are completed. Dr. Ezekowitz’s trading plan is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

On July 22, 2026, Gil M. Labrucherie, CFA, J.D., our Chief Financial Officer, adopteda pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 95,750 shares (including shares issuable upon the exercise of option awards granted to Mr. Labrucherie and shares held indirectly in a trust), which plan expires at the earlier of July 31, 2027 and the date upon which all authorized transactions thereunder are completed. Mr. Labrucherie’s trading plan is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

On August 11, 2026, Jeffrey Finer, M.D., Ph.D., our Chief Executive 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 192,000 shares of our common stock (comprised of shares issuable upon the exercise of option awards previously granted to Dr. Finer), which plan expires at the earlier of November 30, 2027 and the date upon which all authorized transactions thereunder are completed. Dr. Finer’s trading plan is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

On August 26, 2026, Samira Shaikhly, our Chief People Officer, adopteda pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 57,958 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 29, 2027, 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, and accordingly trading under this plan is not authorized to commence until after all transactions under Ms. Shaikhly’s previously adopted Rule 10b5-1 trading arrangement have been completed or have expired without execution.

On September 29, 2026, Liz Bhatt, M.S., M.B.A., our President and Chief Operating Officer, adopteda pre-arranged trading plan for the sale, at the times and prices specified in the plan, of up to an aggregate of 50,000 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 December 31, 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, and accordingly, trading under this plan is not authorized to commence until after all transactions under Ms. Bhatt’s previously adopted Rule 10b5-1 trading arrangement have been completed or have expired without execution.

During the three months ended September 30, 2026, 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.