Seaport Therapeutics filed an S-1 registration statement with the SEC for an initial public offering of common stock on the Nasdaq Global Market under the ticker symbol SPTX. The share count and price range were not disclosed in the preliminary filing.
Prior to the offering, the company raised USD 325 million in net proceeds from private investors, with shareholders holding greater than 5% identified as ARCH Venture Partners, General Atlantic, Sofinnova Investments, Third Rock Ventures, and PureTech, which the filing identified as a founder. Completion of the offering is contingent upon listing on the Nasdaq Global Market.
Seaport Therapeutics is a clinical-stage company developing oral therapies for major depressive disorder and generalized anxiety disorder using a proprietary lymphatic-targeting prodrug platform called Glyph. The platform is designed to bypass first-pass hepatic metabolism, increase oral bioavailability, and reduce side effects associated with parent compounds. The company's lead asset, GlyphAllo (SPT-300), is an oral prodrug of allopregnanolone targeting MDD with or without anxious distress. Its second candidate, GlyphAgo (SPT-320), is an oral prodrug of agomelatine targeting GAD. A third asset, Glyph2BLSD (SPT-348), is an oral prodrug of the non-hallucinogenic LSD analog 2-bromo-LSD in preclinical development for depressive disorders including treatment-resistant depression and PTSD.
GlyphAllo completed a Phase I trial in 99 participants in Australia, the filing stated, demonstrating therapeutically relevant allopregnanolone plasma exposures with an AUCinf of 6.6 ng·hr/mL per 1 mg dosed, compared to 0.7 ng·hr/mL per 1 mg with unmodified oral allopregnanolone in a prior third-party study. No treatment-related severe or serious adverse events were reported. In a Phase IIa randomized, placebo-controlled trial in 80 healthy volunteers in Australia using the Trier Social Stress Test as a biomarker of stress response, GlyphAllo demonstrated initial proof-of-concept and a favorable tolerability profile, as per the filing. The company initiated the Phase IIb BUOY-1 trial in July 2025, a global, randomized, double-blind, placebo-controlled study enrolling up to approximately 360 adults with MDD, with topline data anticipated in the first half of 2027. No interim or efficacy data from BUOY-1 were disclosed.