Seaport Therapeutics raises $255 million in upsized IPO to fund depression drug trials

Seaport Therapeutics, a clinical-stage biotechnology company developing treatments for depression and anxiety, has successfully raised nearly $255 million in an upsized initial public offering that priced at the top of its marketed range, according to people familiar with the matter as reported by Bloomberg.

The Boston-based firm, which had initially aimed to raise funds through an offering of shares priced between $16 and $18, saw strong investor demand that allowed it to expand the IPO and achieve the higher pricing. This success marks a significant milestone for Seaport, which entered 2026 with approximately $233.7 million in cash on hand from prior fundraising totaling $325 million. The new capital will primarily fund advancement of its lead candidate, SPT-300, also known as GlyphAllo, with about $121 million allocated specifically to support a Phase 3 study for this depression treatment.

Seaport's IPO reflects a broader resurgence in biotech public listings, where companies are attracting substantial investor interest despite operating without revenues. As a clinical-stage player, Seaport focuses on innovative therapies for mental health conditions affecting millions worldwide, including major depressive disorder and anxiety. The funds position the company to accelerate clinical trials and potentially bring new antidepressant options to patients who have not responded to existing medications.

In a parallel development highlighting the hot biotech IPO market, Hemab Therapeutics Holdings, another clinical-stage company backed by the Novo Nordisk Foundation, raised $301.5 million in its own upsized IPO, also pricing at the top of its $16 to $18 range. The Cambridge, Massachusetts-based Hemab, which targets blood coagulation disorders like Glanzmann thrombasthenia and Factor VII deficiency, offered around 11.76 million to 16.8 million shares and is set to begin trading on Nasdaq under the symbol COAG as early as May 1. With no revenues but a net loss of about $63.91 million over the last 12 months, Hemab plans to use the proceeds for a Phase 3 study and an ongoing Phase 2 trial.

Both Seaport and Hemab initially targeted around $180 million to $200 million in their filings earlier in the week, but investor enthusiasm led to upsized deals exceeding expectations. Underwriters including Goldman Sachs, Jefferies, and Evercore ISI managed Hemab's offering, signaling confidence from major financial players in these pipelines.

This wave of successful IPOs comes amid renewed momentum for biotech firms, providing critical cash to fuel late-stage development without diluting existing investors excessively. For patients, the implications are promising: Seaport could address gaps in antidepressant efficacy, while Hemab advances solutions for rare bleeding disorders with limited treatments. What happens next includes debut trading for both companies, potential share price volatility based on market reception, and progression through clinical milestones that could lead to regulatory submissions in the coming years.

The deals underscore investor appetite for high-potential therapies in neuroscience and hematology, even as these biotechs navigate clinical risks and competitive landscapes. Seaport and Hemab now join a growing list of public biotechs racing to validate their science with data that could transform patient care.