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PureTech launches Seaport, hoping to create Karuna 2.0

Hoping to repeat a recent success story, the biotechnology startup creator PureTech Health has launched a new company aimed at developing psychiatric medicines.

Seaport Therapeutics officially debuted Tuesday with $100 million from a Series A financing round that received more investor interest than expected. High-profile biotech backers like ARCH Venture Partners, Sofinnova Investments and Third Rock Ventures participated in the round, which Seaport will use to “support the rapid advancement” of its experimental therapies.

PureTech operates through a “hub-and-spoke” model, wherein it discovers, develops or acquires promising drug programs, then spins them out into individual startups that are kept at arm’s reach.

The most well-known of these startups, Karuna Therapeutics, recently sold to Bristol Myers Squibb for $14 billion. Its “KarXT” medicine could receive Food and Drug Administration approval before the end of September as a treatment for schizophrenia, which some Wall Street analysts believe, at its peak, could generate billions of dollars each year. 

That deal with Bristol Myers has already generated around $1.1 billion in gross proceeds for PureTech, which initially put in less than $19 million to get Karuna off the ground, and could result in upwards of $400 million more if certain regulatory and commercial milestones are hit.

At Seaport, scientists have created a technology designed to help oral drugs bypass the liver, where they’re often metabolized and their effects diminished. Seaport’s “Glyph” platform attaches drugs to dietary fat molecules, rerouting them to the lymphatic system to keep more of them circulating through the body while also reducing side effects.

The company’s most advanced candidate is a prodrug of allopregnanolone, a steroid that is found in the brain, regulates neuron excitability and is the active ingredient in Sage Therapeutics’ postpartum depression therapy Zulresso. Seaport, though, is developing the prodrug for anxious depression. A mid-stage clinical trial of healthy volunteers showed it acted as researchers had suspected, according to the startup.

Additionally, Seaport is working on a novel prodrug of agomelatine, a compound very similar to melatonin, for the treatment of generalized anxiety disorder. PureTech has said this program should enter human testing in the first half of 2025.

Farther behind, Seaport has “multiple discovery and preclinical programs underway,” including one built around a prodrug of a non-hallucinogenic compound believed to help the brain function and adapt. That program targets mood and other psychiatric disorders.

PureTech sees immense opportunity in Seaport, so much so that it’s pursuing a leadership reshuffle. Founding CEO Daphne Zohar is stepping down from the company’s board of directors to fill the top spot at Seaport. She will continue to advise the board, however.

“PureTech has now reached both financial independence and the important inflection point of returning capital,” Zohar said in a statement. “I will continue to work on behalf of PureTech shareholders by advancing the exciting Seaport programs through a structure that can help unlock their value for PureTech.”

PureTech senior executive Bharatt Chowrira took over as CEO on Tuesday. Eric Elenko, who co-founded the company and currently serves as chief innovation officer, has been promoted to president.

Steven Paul, the former CEO and Chair of Karuna, also founded Seaport. He will now helm the startup’s board of directors, which will include Elenko and Chowrira as well as Robert Nelsen, managing partner and co-founder of ARCH, and James Healy, managing partner of Sofinnova.

Courtney Wallace, a venture partner at Third Rock, will join, too, but as a board observer.

“At Seaport Therapeutics, PureTech has brought together the proven team that helped build Karuna and some of the investors that backed Karuna’s initial funding rounds,” Chowrira said. “I am confident that following our well charted strategy of starting with validated mechanisms and applying our proprietary Glyph technology to solve previous limitations will enable Seaport to provide important new options for patients with depression, anxiety and other neuropsychiatric conditions.”