X0609 4 2026-04-30 0002042347 Seaport Therapeutics, Inc. SPTX 0001818770 Loebel Antony false SEAPORT THERAPEUTICS, INC. 101 SEAPORT BLVD., FLOOR 12 BOSTON MA 02210 false true false false Chief Medical Officer false Common Stock 2026-05-04 4 C false 20109 A 20109 D 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 63157 0 D Common Stock 20109 0 D 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 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