Launched by PureTech and backed by well-known venture capital firms, the startup has raised $325 million since its debut this spring.
A young biotechnology company developing drugs for the brain has raised another $225 million from a syndicate of well-known healthcare investors.
Launched in April, Seaport Therapeutics wants to create psychiatry medicines that last longer and cause fewer side effects. The company was founded by PureTech Health, the same Boston-based startup incubator that established Karuna Therapeutics 15 years ago. Karuna led the charge developing a new class of antipsychotic medications, and was recently acquired through a $14 billion deal.
In some ways, Seaport serves as Karuna's successor. The biotech's most advanced program is an oral drug designed to get more of a steroid called allopregnanolone into the brain. The steroid regulates how neurons respond to stimulation, and is the active ingredient in Sage Therapeutics' postpartum depression therapy Zulresso.
Seaport, though, is testing it against major depressive disorder, in a mid-stage study that the company says could be the foundation for an approval filing. Seaport is also working on a compound very similar to melatonin, for the treatment of generalized anxiety disorder, as well as a drug for mood and neuropsychiatric disorders.
When it debuted in April, Seaport had $100 million from a Series A fundraising round that got buy-in from prominent biotech backers like Arch Venture Partners, Sofinnova Investments and Third Rock Ventures. Those firms, along with PureTech, also participated in the funding round announced Monday, which Seaport said received more interest than initially expected.
General Atlantic, a growth equity firm, led the Series B round, and was joined by T. Rowe Price Associates, Foresite Capital, Invus, Goldman Sachs Alternatives, CPP Investments and other new investors.
Seaport plans to use the proceeds to move clinical-stage research programs through important milestones and further advance the company's "Glyph" drugmaking technology. "This financing enables the important clinical work that brings us another step closer to delivering new medicines," said Daphne Zohar, Seaport's CEO and one of its founders, in a statement.
Zohar created PureTech and was its longtime chief executive until she moved over to Seaport. She also co-founded Karuna. Steven Paul, who served as CEO of Karuna, co-founded Seaport and is now chair of the biotech's board of directors.
Brett Zbar, the global head of life sciences at General Atlantic, said in Monday's statement that his firm is "impressed" with the Seaport team's "outstanding" track record developing drugs for the central nervous system, as well as its technology and slate of research programs.
"The approach to clinical development and trial design demonstrates the deep neuropsychiatric expertise around the table, which we believe offers unique advantages that will contribute to Seaport's success," Zbar said.