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 I 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 preclinical-stage 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.
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