Atavistik Bio Raises USD 40 Million Series B Extension, Totaling USD 160 Million Round

Atavistik Bio Closes USD 40 Million Series B Extension, Bringing Total Round to USD 160 Million

Atavistik Bio, a Cambridge, Massachusetts-based biotechnology company focused on developing selective allosteric therapeutics, has closed a USD 40 million extension to its Series B financing, bringing total proceeds from the round to USD 160 million. The company is advancing a pipeline of mutant-selective small molecule inhibitors targeting hereditary hemorrhagic telangiectasia and myeloproliferative neoplasms, the company said.

The extension was funded by new investor RA Capital Management, which joins existing Series B participants Nextech Invest, The Column Group, Lux Capital, and Regeneron Ventures. The initial Series B close was announced in December 2025. Atavistik Bio said it plans to use the combined proceeds to fund clinical development of its lead candidate, ATV-1601, an oral allosteric AKT1-selective inhibitor for hereditary hemorrhagic telangiectasia, and to advance its JAK2 V617F mutant-selective inhibitor program for myeloproliferative neoplasms through clinical proof of concept.

ATV-1601 has completed a Phase 1 study in oncology, where the company said it demonstrated a safety profile consistent with its AKT1-selective mechanism, avoiding the hyperglycemia associated with pan-AKT inhibitors driven by AKT2 inhibition. The company is now redirecting development toward HHT, a severe inherited bleeding disorder affecting more than 1.6 million people globally with no currently approved therapies. AKT1 hyperactivation has been identified as a driver of the vascular pathology underlying HHT. The company's second program targets the JAK2 V617F mutation, the most common driver mutation in myeloproliferative neoplasms, found in approximately 95% of polycythemia vera patients, 60% of essential thrombocythemia patients, and 55% of myelofibrosis patients. Approved pan-JAK inhibitors such as ruxolitinib provide symptom relief but inhibit both mutant and wild-type JAK2, limiting disease modification and contributing to adverse events.

Atavistik Bio's platform centers on designing small molecules that exploit structural differences between mutant and wild-type proteins, targeting allosteric sites rather than conserved active sites to achieve selectivity. This approach aims to widen the therapeutic window by enabling higher effective doses against disease-driving targets without the toxicities associated with wild-type inhibition. The company was co-founded by Philip Cole, a professor at Harvard Medical School whose academic work on allosteric kinase regulation and isoform-selective inhibition informs the platform's scientific foundation. Specific intellectual property licensing arrangements between the company and academic institutions have not been publicly disclosed.

Bryan Stuart serves as chief executive officer of Atavistik Bio. No major pharmaceutical licensing or co-development partnerships have been publicly disclosed by the company, which appears to be advancing its pipeline internally using venture financing. Details of funding rounds prior to the Series B have not been specified in available disclosures.

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