Ajax Therapeutics Presents Preclinical Data on Differentiated Efficacy Profile of AJ1-11095, a First-in-Class Type II JAK2 Inhibitor, at the American Society of Hematology Annual Meeting
– Data demonstrate superior efficacy compared to ruxolitinib, an approved type I JAK2 inhibitor, including reductions in mutant allele burden and bone marrow fibrosis, key markers of disease modification –
– AJ1-11095 is currently in a Phase 1 clinical trial in patients with myelofibrosis, previously treated with a type I JAK2 inhibitor –
NEW YORK and CAMBRIDGE, Mass., Dec. 04, 2025 (GLOBE NEWSWIRE) -- Ajax Therapeutics, Inc., a biopharmaceutical company developing next generation JAK inhibitors for patients with myeloproliferative neoplasms (MPNs), today announced the presentation of preclinical data for AJ1-11095, the company’s first-in-class type II JAK2 inhibitor that is currently in a Phase 1 trial in patients with myelofibrosis who have previously been treated with a type I JAK2 inhibitor and have either not responded or have lost response (NCT identifier: NCT06343805). The preclinical results demonstrate the superior efficacy profile of AJ1-11095, compared to ruxolitinib, one of the four FDA-approved type I JAK2 inhibitors, in well validated MPN models. The poster is being presented at the 67th American Society of Hematology (ASH) Annual Meeting in Orlando, FL, in a session on December 6th, 2025, at 5:30-7:30 p.m. EST in the West Halls B3-B4 (Presentation #1983.)
The poster entitled “AJ1-11095, a potent and highly selective type II JAK2 inhibitor, shows enhanced therapeutic efficacy as compared with type I JAK2 inhibitor ruxolitinib in models of myeloproliferative neoplasms (MPNs)” includes the following preclinical data highlights:
- In ruxolitinib-persistent JAK2 mutant cells, AJ1-11095 restored the inhibition of JAK/STAT signaling, supporting the ability to overcome type I JAK2 inhibitor mediated persistence.
- In a JAK2VF knock-in competitive transplant model, AJ1-11095 demonstrated superior efficacy compared to ruxolitinib, including improvements in hematologic parameters and spleen weights, and marked reductions in mutant allele burden across peripheral blood, spleen, and bone marrow. Significant mutant allele burden reductions were also seen in animals initially treated with ruxolitinib and then treated with AJ1-11095 suggesting AJ1-11095 can reduce mutant allele burden after exposure to a type I JAK2 inhibitor.
- In the hMPLW515L myelofibrosis model, AJ1-11095 demonstrated superior efficacy compared to ruxolitinib with improvements in hematologic parameters and spleen weights and significant reductions in bone marrow fibrosis and pro-fibrotic cytokine levels, including TNFa, IL13, and IP-10.
Andrew Dunbar, MD, Assistant Professor, Department of Hematopoietic Biology and Malignancy, The University of Texas MD Anderson Cancer Center and presenter of the AJ1-11095 poster commented, “It’s exciting to see such consistent and superior efficacy results with AJ1-11095, when compared to ruxolitinib, across all preclinical MPN models and confirms the potential therapeutic advantages of type II JAK2 inhibition versus type I JAK2 inhibition. We were most encouraged by the potential for disease modification with AJ1-11095, as seen by the reductions in mutant allele burden and bone marrow fibrosis, which were not seen with ruxolitinib.”
“The preclinical data presented today on our lead type II JAK2 development candidate, AJ1-11095, were what drove us to move the program into the clinic as a potential differentiated treatment option for patients with myelofibrosis whose disease has been refractory to type I JAK2 inhibitors,” said David Steensma, MD, FACP, Chief Medical Officer of Ajax Therapeutics. “Our Phase 1 clinical study, AJX-101, continues to enroll well and we expect to transition to the expansion phase of the study early next year.”
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, and disease progression, leaving significant unmet treatment needs for these patients.
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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