Atavistik Bio Adds $40 Million to Series B to Advance HHT and MPN Programs

Rare Daily Staff

Atavistik Bio said it raised an additional $40 million in an extension of its Series B financing, bringing total proceeds from the round to $160 million.

The funds will advance its lead program for the rare genetic bleeding disorder hereditary hemorrhagic telangiectasia, as well as a group of rare cancers.

RA Capital Management led the new funding, joining existing investors Nextech Invest, The Column Group, Lux Capital, and Regeneron Ventures. The extension follows Atavistik’s initial $120 million Series B announced in December 2025.

The funding will support clinical development of the company’s lead program, ATV-1601, and advancement of its JAK2 V617F mutant-selective inhibitor for myeloproliferative neoplasms, a group of chronic blood cancers. ATV-1601, an oral AKT1-selective inhibitor, is being developed as a potential treatment for hereditary hemorrhagic telangiectasia (HHT), which currently has no approved therapies.

“These additional funds strengthen our ability to accelerate development of therapies designed to deliver superior efficacy, improved tolerability, and potentially transformative outcomes for patients,” said Atavistik CEO Bryan Stuart.