Seaport Therapeutics targets $912 million valuation in US IPO bid

Seaport Therapeutics is asking public-market investors to put a $912 million price tag on a company with no approved drug, a live test of whether appetite has returned for risky biotech deals. The Boston-based developer is seeking to raise as much as $212.4 million by selling 11.8 million shares at $16 to $18 each, with Goldman Sachs, JPMorgan and Leerink Partners leading the offering on Nasdaq under the ticker SPTX.

The timing matters as much as the valuation. IPO activity has improved after a thin stretch, with 22 traditional U.S. listings raising more than $9.4 billion through March 31, the strongest first quarter in five years. Other recent deals have helped reset sentiment, including X-Energy’s April 24 debut, when shares rose 30.9% to a $11.9 billion valuation, and Lincoln International’s filing for a U.S. IPO the same day. Even so, investors remain selective, especially in sectors that depend on clinical data rather than current sales.

That puts Seaport squarely in the market’s sweet spot and its danger zone at once. Biotech IPOs are often used to measure confidence in earlier-stage drug developers, and Seaport is still in the clinical-stage camp. Its lead asset, GlyphAllo, also known as SPT-300, is an oral prodrug of allopregnanolone designed to bypass first-pass liver metabolism and enable oral dosing for neuropsychiatric disorders. The company says the compound is aimed at major depressive disorder, and its filing notes that allopregnanolone has been clinically validated in third-party trials for postpartum depression.

Seaport went public with its story long before it filed the IPO. The company launched with a $100 million oversubscribed Series A on April 9, 2024, backed by ARCH Venture Partners, Sofinnova Investments, Third Rock Ventures and PureTech Health. PureTech said at the time that it held a 61.5% diluted stake in Seaport and that the company was created to advance neuropsychiatric programs and related Glyph intellectual property. Daphne Zohar founded and leads the company, while Steven M. Paul, M.D., serves as founder and chair; Paul previously ran Karuna Therapeutics before Bristol Myers Squibb bought it for $14 billion.

Seaport’s IPO filing, submitted April 10 and amended April 27, shows a company trying to convert scientific progress into market credibility. The first patient was dosed in the Phase 2b BUOY-1 study of GlyphAllo in July 2025, and Seaport said in March that peer-reviewed data were published in Science Translational Medicine. The company also added Sharon Mates to its board on April 27, bringing in a neuroscience executive who co-founded and led Intra-Cellular Therapies until Johnson & Johnson acquired it in 2025 for about $14.6 billion. For investors, the offering is a verdict on whether the public markets are truly thawing enough to fund long-horizon drug bets again.