Seaport Therapeutics Holds $403.8 Million, Enough Cash to Run Into 2029

Seaport Therapeutics ended September with $403.8 million in cash, cash equivalents and investments. That is 73% more than it held at the end of 2025, and the Boston drug developer says the money will last into 2029. The company reported third-quarter results Monday, Nov. 2, six months after it went public on Nasdaq. Its net loss widened 17% to $26.4 million, according to the results release filed with the SEC.

Seaport (Nasdaq: SPTX) develops oral medicines for depression, anxiety and other neuropsychiatric disorders. The company said its cash runway covers three mid-to-late-stage clinical readouts. The first is expected in the first half of 2027, from a Phase 2b trial of its lead drug in major depressive disorder.

Key figures: Cash and investments $403.8M · Q3 net loss $26.4M ($0.49/share) · R&D $23.9M (up 17%) · G&A $6.5M (up 29%) · Runway into 2029

The quarter by the numbers

Research and development spending rose to $23.9 million from $20.5 million a year earlier. Seaport said the $3.4 million increase came mainly from its BUOY-1 Phase 2b trial. General and administrative costs rose to $6.5 million from $5.0 million, which the company tied mainly to the costs of operating as a public company. Total operating expenses were $30.3 million, up from $25.4 million, according to the Form 8-K filing.

The net loss per share fell to $0.49 from $9.43, even though the dollar loss grew. That is because the share count changed after the IPO: weighted-average shares outstanding rose from about 2.4 million to about 53.5 million. Other income, mostly from the cash pile, added $4.1 million in the quarter.

For the first nine months of 2026, the net loss was $114.4 million, compared with $50.7 million a year earlier. Most of that gap came from general and administrative costs, which reached $53.8 million for the nine months. That figure includes $39.1 million of non-cash stock-based compensation, compared with $3.5 million in the same period of 2025.

Data analysis: spending up, runway longer

The Boston Report compared the third quarter with the same quarter of 2025, using the company’s reported figures. R&D and the net loss each grew about 17%, and G&A grew about 29%. R&D was 79% of operating expenses, roughly the same share as a year earlier (80%). The extra spending is going mostly to clinical work, not overhead.

The cash balance rose $170.1 million from $233.7 million on Dec. 31, 2025. The main reason was the initial public offering. On April 30, Seaport priced an upsized IPO of about 14.2 million shares at $18 each, raising about $254.9 million before fees. Its shares began trading May 1. At the third quarter’s operating-expense pace of about $30 million, the balance equals a little over three years of spending, in line with the company’s guidance of funding into 2029. That simple estimate does not account for future changes in trial costs.

Pipeline milestones

• GlyphAllo (SPT-300), major depressive disorder: In September, a Phase 1 driving-simulation trial met its main goal. An evening dose of 375 mg did not impair next-morning driving compared with placebo, and the company plans to submit the results to the FDA. Enrollment in the Phase 2b BUOY-1 trial is on track, with topline data expected in the first half of 2027.
• GlyphAgo (SPT-320), generalized anxiety disorder: The first patient was dosed in October in a Phase 2a trial in patients with anxiety and sleep disturbance, with data expected in early 2028. A Phase 2/3 trial is planned for the first half of 2027, with data by the end of 2028. Earlier data showed a 6.8-fold increase in agomelatine bioavailability, the company said.
• Glyph2BLSD (SPT-348): This non-hallucinogenic version of a psychedelic compound is in preclinical work. First-in-human-enabling studies are expected to finish by the end of 2027.

A Seaport District biotech

The company is based in Boston’s Seaport District, the South Boston waterfront neighborhood that is also home to other life sciences companies. Its results join a busy Boston earnings season, which we track in our roundup of third-quarter earnings from Boston companies. The local biotech IPO market has stayed active, too: Bambusa Therapeutics recently made its Nasdaq debut. For more company coverage, see the business section of our Boston news page.

“Seaport is well-capitalized, with cash runway through all three of our upcoming mid-to-late-stage clinical data readouts,” co-founder and CEO Daphne Zohar said in the release. “There are a billion people living with mental illness – waiting and hoping for better medicines.”

The company noted that clinical results are uncertain. Its forward-looking statements list risks including trial outcomes, regulatory review and the need for more funding.

Sources

• Seaport Therapeutics: Third Quarter 2026 Financial Results (SEC Form 8-K Exhibit 99.1, Nov. 2, 2026)
• SEC EDGAR: Seaport Therapeutics Form 8-K filing index
• Business Wire: Seaport Therapeutics Reports Third Quarter 2026 Financial Results
• Seaport Therapeutics: Pricing of Upsized Initial Public Offering
• Reuters: Seaport Therapeutics raises about $255 million in upsized IPO