X0609 4 2026-04-30 0002042347 Seaport Therapeutics, Inc. SPTX 0001864430 White Lauren false SEAPORT THERAPEUTICS, INC. 101 SEAPORT BLVD., FLOOR 12 BOSTON MA 02210 false true false false Chief Financial Officer false Common Stock 2026-05-04 4 C false 6702 A 6702 I By Lauren Anne White Living Trust, dated January 30, 2020 Stock Option (Right to Buy) 18 2026-04-30 4 A false 63680 0 A 2036-04-29 Common Stock 63680 63680 D Series B Preferred Stock 2026-05-04 4 C false 21052 0 D Common Stock 6702 0 I By Lauren Anne White Living Trust, dated January 30, 2020 Each share of Series B Preferred Stock (the "Preferred Stock") was convertible into Common Stock of the Issuer on a one-for-3.1407 basis at the option of the holder, and automatically converted upon the closing of the Issuer's initial public offering without payment of further consideration. The Preferred Stock had no expiration date. The Reporting Person disclaims beneficial ownership of such shares for purposes of Section 16 of the Exchange Act, except to the extent of her pecuniary interest therein, if any. This report shall not be deemed an admission that she is a beneficial owner of such shares for the purpose of Section 16 of the Exchange Act, or for any other purpose. The shares underlying this option shall vest in forty-eight (48) equal monthly installments following April 30, 2026, subject to the Reporting Person's continued service on each such vesting date. /s/ Lana Gladstein, Attorney-in-Fact 2026-05-04