Biotech Startup Atavistik Raises $40M for Rare Bleeding Disorder Drug

The Series B extension brings Atavistik Bio's total Series B financing to $160 million as it prepares for clinical trials of its lead program for hereditary hemorrhagic telangiectasia (HHT).

Published on Mar. 5, 2026

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Atavistik Bio, a biotech startup based in Cambridge, Massachusetts, has raised an additional $40 million in a Series B extension round led by new investor RA Capital Management. The new funding will support the development of Atavistik's lead drug candidate, ATV-1601, which is being investigated as a treatment for hereditary hemorrhagic telangiectasia (HHT), a rare and potentially life-threatening bleeding disorder with no approved therapies.

Why it matters

HHT is a genetic disorder that leads to abnormal blood vessel formation and frequent, uncontrolled bleeding. The lack of approved treatments for this condition makes Atavistik's drug candidate a potentially important development for the HHT patient community. The company's approach of targeting the AKT1 protein, which plays a role in the abnormal cell growth behind HHT, sets it apart from other startups working on HHT therapies.

The details

Atavistik's drug candidate, ATV-1601, is a small molecule inhibitor of the AKT1 protein. Unlike other AKT inhibitors developed for cancer, which can have a range of side effects by also inhibiting AKT2, Atavistik's molecule is designed to selectively target AKT1, which the company says is the primary driver of the abnormal cell growth behind HHT. Atavistik initially tested ATV-1601 in cancer, where Phase 1 results showed a favorable safety profile, before shifting its focus to developing the drug for HHT.

  • Atavistik launched in 2021 backed by a $60 million Series A round.
  • The company announced a $120 million Series B round in late December 2025.
  • The new $40 million Series B extension was announced on March 5, 2026.

The players

Atavistik Bio

A biotech startup based in Cambridge, Massachusetts, that is developing treatments for rare diseases, including a drug candidate for hereditary hemorrhagic telangiectasia (HHT).

RA Capital Management

A new investor that led the $40 million Series B extension round for Atavistik Bio.

Jared Rutter

A professor of biochemistry at the University of Utah, whose lab developed the platform technology that Atavistik is using to discover its drug candidates.

Bryan Stuart

The CEO of Atavistik Bio.

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What they’re saying

“This additional funding further strengthens our ability to accelerate the development of best-in-class therapies designed to deliver superior efficacy, improved tolerability profiles, and potentially transformative outcomes for patients.”

— Bryan Stuart, CEO, Atavistik Bio (medcitynews.com)

What’s next

Atavistik plans to use the new funding to support the clinical development of ATV-1601 for the treatment of hereditary hemorrhagic telangiectasia (HHT), as well as continued preclinical work on a drug candidate for myeloproliferative neoplasms (MPNs).

The takeaway

Atavistik's approach of selectively targeting the AKT1 protein, which is a key driver of the abnormal blood vessel formation in HHT, sets it apart from other startups working on therapies for this rare and debilitating bleeding disorder. The additional $40 million in funding will help the company advance its lead program towards clinical trials, potentially bringing the first approved treatment option to HHT patients.