Theseus Pharmaceuticals emerges from stealth with $100M series B and Ariad veterans at the helm

Cancer cells reproduction
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Theseus Pharmaceuticals has launched from under the wing of healthcare fund manager OrbiMed with a $100 million series B financing and data to show that the new biotech’s gastrointestinal tumor candidate could be effective in fighting treatment-resistant cancers.

The financing was led by Foresite Capital, with a number of new investors including Adage Capital Management, Boxer Capital, Farallon Capital Management and others. OrbiMed, which incubated Theseus to tackle treatment-resistant cancer mutations, also contributed and General Partner Carl Gordon is on the new company’s board. Foresite Capital Managing Director Michael Rome, Ph.D., will also join the Theseus board in conjunction with the financing.

Theseus is developing pan-variant kinase inhibitors or therapies that adapt to cancer mutations to retain effectiveness. The company’s lead candidate is THE-630, which is in early-stage development for treating gastrointestinal stromal tumors that have become resistant to other types of kinase inhibitors.

THE-630 was found to have potent activity against all types of activating and resistance mutations found in GISTs that have a KIT mutation, according to a poster presentation at the American Association for Cancer Research (AACR) meeting this month. Theseus expects to file an IND for the therapy before the year's end. 

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"For many driver-oncogene targets, current standard-of-care kinase inhibitors have insufficient activity to cover the broad array of variants that could lead to resistance, so they are limited by constantly mutating cancer," said William Shakespeare, Ph.D., Theseus co-founder and president of research and development. "Using sophisticated assays, we can predict how cancers will change, enabling new therapies to stay ahead of future mutations and overcome the demonstrated burden of treatment resistance."

Other pipeline products under development by Theseus include a selective EGFR inhibitor for patients with non-small cell lung cancer that has become resistant to first or later treatment with AstraZeneca's Tagrisso. A third kinase target is also in the works, though for an as yet undisclosed indication.

Theseus' leadership team is made up of industry veterans who previously ran Ariad Pharmaceuticals, which was picked up by Takeda in a deal valued at $5.2 billion back in 2017. Shakespeare served as vice president of drug discovery at Ariad and oversaw the discovery of the FDA-approved compounds Iclusig and Alunbrig.

Other Theseus co-founders and Ariad alum are Chief Technical Officer David Dalgarno, D.Phil., Chief Scientific Officer Victor Rivera, Ph.D., Vice President of Chemistry Wei-Sheng Huang, Ph.D., and Chief Medical Officer David Kerstein, M.D.

"The scientific co-founders of Theseus are a team of distinguished drug discovery and development leaders who have pioneered the development of pan-variant kinase inhibitors," said Iain Dukes, D.Phil., venture partner of Orbimed who is Theseus' co-founder and interim CEO. "With this foundation of expertise, combined with the backing of a top-tier syndicate of investors, Theseus is well-positioned to develop best-in-class, pan-variant TKIs that provide durable benefit for people living with cancer."