Eli Lilly’s type II JAK2 inhibitor, which it acquired through the $2.3bn acquisition of Ajax Therapeutics earlier this year, has shown an encouraging safety profile and promising clinical activity in a Phase I trial.
In the AJX-101 study (NCT06343805), AJ1-11095, a once-daily oral medication, was investigated in patients with myelofibrosis who did not respond to previous treatment with a type I JAK2 inhibitor.
Go deeper with GlobalData
Discover B2B Marketing That Performs
Combine business intelligence and editorial excellence to reach engaged professionals across 36 leading media platforms.
In patients with the rare blood cancer, AJ1-11095 demonstrated responses across the standard efficacy endpoints of spleen volume reduction and symptom improvement.
The SVR35 rate, a reduction in spleen volume of at least 35%, was observed as the best response in 70% of patients.
The TSS50 rate, indicating at least a 50% improvement in symptom burden, was also seen in 70% of patients at week 12.
Lilly said the study also recorded reductions in driver mutation variant allele frequency (VAF) in 21 out of 23 patients. VAF reductions are not commonly observed after treatment with a type 1 JAK2 inhibitor.
Of the 17 patients who reached week 24 of treatment, 59% saw a reduction of 20% or greater, and 35% saw a reduction of 50% or greater, including JAK2, MPL, and CALR type 1 and type 2 mutations.
The overall safety profile for the medicine was generally manageable. No dose-limiting toxicities were observed, and most patients enrolled in the dose escalation phase remain on study (78%).
“Patients with myelofibrosis who have been previously treated with an existing type I JAK2 inhibitor face very limited treatment options, highlighting an urgent need for new therapies,” said John Mascarenhas, MD, professor of medicine, Icahn School of Medicine at Mount Sinai and principal investigator of the AJX-101 study. “These early clinical findings suggest that selective targeting of the type II conformation of JAK2 may provide a differentiated approach. With an encouraging safety profile, meaningful spleen size reduction, symptom improvement, and decrease in underlying mutant disease burden, these data, while early, point to the potential to meaningfully impact treatment options for people with certain myeloproliferative neoplasms.”
Lilly presented the data on the JAK2 inhibitor during an oral presentation at the 2026 European Hematology Association (EHA) Annual Meeting which took place between 11-14 June in Stockholm, Sweden.
AJ1-11095 is currently being evaluated in an expansion cohort in second-line myelofibrosis, with plans to investigate in patients with high-risk polycythemia vera and those with myelofibrosis who have not yet received a JAK2 inhibitor.
Lilly gained the drug through its acquisition of Ajax Therapeutics, agreed in April 2026. Under the terms of the deal, Ajax shareholders could receive up to $2.3bn if certain clinical and regulatory milestones are achieved.
Lilly and Ajax had already worked together prior to the acquisition, with Lilly participating in Ajax’s $95m Series C financing round in 2024.
