Ajax Therapeutics Receives Orphan Drug Designation from the U.S. FDA for AJ1-11095 for the Treatment of Myelofibrosis

AJ1-11095 is a first-in-class Type II JAK2 inhibitor currently in a Phase 1 study for the treatment of patients with myelofibrosis, previously treated with a Type I JAK2 inhibitor

NEW YORK and CAMBRIDGE, Mass., Dec. 10, 2025 (GLOBE NEWSWIRE) — Ajax Therapeutics, Inc., a biopharmaceutical company developing next generation JAK inhibitors for patients with myeloproliferative neoplasms (MPNs), today announced that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation to AJ1-11095 for the treatment of myelofibrosis, a debilitating blood cancer that affects approximately 20,000 patients in the U.S. AJ1-11095 is the first JAK2 inhibitor to enter the clinic that binds the Type II conformation of the JAK2 kinase, in contrast to all currently approved JAK2 inhibitors that bind the Type I conformation. AJ1-11095 is in an ongoing Phase 1 trial in patients with myelofibrosis who have been previously treated with a Type I JAK2 inhibitor and have either not responded or have lost response (NCT identifier: NCT06343805).

“Orphan Drug Designation is an important milestone in our clinical development of AJ1-11095 for the treatment of myelofibrosis,” said David Steensma, MD, FACP, Chief Medical Officer of Ajax. “This designation reinforces the compelling need for effective new treatment options for patients suffering from myelofibrosis, and supports our continued efforts to advance AJ1-11095 to address the unmet need for patients who would benefit from improved treatment efficacy, or who have not responded to existing therapies.”

About AJ1-11095
AJ1-11095 was designed by Ajax Therapeutics using structure-based drug design and computational methods at scale to selectively bind the Type II conformation of the JAK2 kinase in order to provide greater efficacy with disease modification compared to all currently approved JAK2 inhibitors, including ruxolitinib, which bind the Type I conformation of JAK2. AJ1-11095 has been shown in preclinical studies to reverse marrow fibrosis, reduce mutant allele burden, and maintain efficacy against MPN cells that become resistant to chronic Type I JAK2 inhibition. 

About Myelofibrosis
Myelofibrosis (MF) is a rare blood cancer that affects approximately 20,000 patients in the United States and approximately 26,000 patients in Europe. The disease is characterized by spleen enlargement, scarring (fibrosis) in the bone marrow, progressive anemia, and debilitating symptoms such as fatigue, night sweats, itching, and abdominal discomfort, which can impair a patient’s quality of life. The most widely used treatment for MF patients are Type I JAK2 inhibitors, which can reduce spleen size and provide symptomatic improvement but have little effect on the underlying cause of disease. Over time, most MF patients stop Type I JAK2 inhibitor therapy; the most common causes for treatment discontinuation include a lack of benefit or loss of response, adverse events such as anemia, and disease progression. 

About Ajax Therapeutics
Ajax Therapeutics, Inc. is pursuing uniquely selective approaches to develop novel next generation therapies for myeloproliferative neoplasms (MPNs), including myelofibrosis. By combining the deep cancer and structural biology insights of our founding scientists with the industry’s most advanced computational drug discovery and protein structure platforms, we aim to discover and develop more precisely designed therapies to address the significant unmet needs for patients with MPNs.

Please find more information at www.ajaxtherapeutics.com.

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Kathryn Morris
The Yates Network
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kathryn@theyatesnetwork.com