Table of Contents FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Seaport Therapeutics, Inc. (Exact name of registrant as specified in its charter) As filed with the Securities and Exchange Commission on April 10, 2026. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 (State or other jurisdiction of incorporation or organization) Delaware 2834 99-2235719 (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identification Numb ...