Indianapolis, IN – June 15, 2026 – Eli Lilly and Company has unveiled encouraging Phase I data for its investigational type II JAK2 inhibitor, AJ1-11095, demonstrating a favorable safety profile and promising clinical activity in patients with myelofibrosis who have exhausted existing treatment options. The findings, presented at the prestigious European Hematology Association (EHA) Annual Meeting in Stockholm, Sweden, suggest a potential new therapeutic avenue for a patient population facing significant unmet needs.
The once-daily oral medication, acquired by Lilly through its substantial $2.3 billion acquisition of Ajax Therapeutics earlier this year, was evaluated in the AJX-101 study (NCT06343805). This early-stage trial specifically targeted patients with myelofibrosis who had previously failed to respond to treatment with a type I JAK2 inhibitor. These patients represent a particularly challenging subgroup, often experiencing severe symptoms and limited recourse to effective therapies.
The presented data highlights AJ1-11095’s ability to address key efficacy endpoints in myelofibrosis, including spleen volume reduction and symptom burden alleviation. These improvements, coupled with the drug’s generally manageable safety profile, position it as a potentially significant advancement in the treatment landscape for this rare and debilitating blood cancer.
Unveiling Promising Efficacy: A Deeper Dive into the Data
The AJX-101 study meticulously assessed the impact of AJ1-11095 across several critical measures of treatment response. For patients battling myelofibrosis, an enlarged spleen (splenomegaly) is a hallmark symptom, contributing significantly to pain, discomfort, and overall poor quality of life. The trial reported a remarkable SVR35 rate – a reduction in spleen volume of at least 35% – in an impressive 70% of patients, signifying the best response observed in this cohort.
Beyond physical manifestations, the psychological and functional impact of myelofibrosis is profound. The study also measured symptom burden using the Total Symptom Score (TSS). The TSS50 rate, indicating a reduction in symptom burden by at least 50%, was achieved by 70% of patients by week 12, underscoring the drug’s capacity to alleviate the debilitating symptoms associated with the disease.
Perhaps one of the most compelling aspects of the Phase I data is the observed reduction in driver mutation variant allele frequency (VAF). These mutations, such as JAK2, MPL, and CALR, are the underlying genetic drivers of myelofibrosis. Lilly reported that AJ1-11095 led to VAF reductions in a significant 21 out of 23 patients assessed. This finding is particularly noteworthy as VAF reductions are not commonly observed with existing type 1 JAK2 inhibitors, suggesting that AJ1-11095’s mechanism of action may target the disease at a more fundamental level.
Further reinforcing these observations, at week 24 of treatment, 59% of the 17 patients who reached this milestone demonstrated a VAF reduction of 20% or greater. Even more encouraging, 35% of these patients achieved a VAF reduction of 50% or greater, encompassing reductions in JAK2, MPL, and CALR type 1 and type 2 mutations. This suggests a potential to not only manage symptoms but also to potentially impact the underlying disease biology.
A Favorable Safety Profile: Enabling Continued Treatment
The safety and tolerability of AJ1-11095 were also key focal points of the Phase I trial. The drug exhibited an overall manageable safety profile, with no dose-limiting toxicities identified during the dose escalation phase. This is a critical factor for any new therapeutic, particularly in a patient population that may have pre-existing comorbidities.
The encouraging safety data is further substantiated by the high rate of patient retention in the study. A substantial 78% of patients enrolled in the dose escalation phase remained on the study, a testament to the drug’s tolerability and the perceived benefit by both patients and investigators. This high retention rate allows for more comprehensive data collection and provides a strong foundation for subsequent clinical development.
Expert Perspectives: A Differentiated Approach to a Challenging Disease
The clinical significance of these early findings was underscored by insights from Dr. John Mascarenhas, MD, Professor of Medicine at the Icahn School of Medicine at Mount Sinai and the principal investigator of the AJX-101 study. Dr. Mascarenhas articulated the critical need for novel therapies in myelofibrosis, stating, "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."
He further elaborated on the potential of AJ1-11095, commenting, "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."
Dr. Mascarenhas’s comments highlight the scientific rationale behind Lilly’s investment in type II JAK2 inhibitors. While type I JAK inhibitors target both active and inactive forms of the JAK2 enzyme, type II inhibitors are designed to specifically bind to and inhibit the active conformation of JAK2. This selectivity could translate into improved efficacy and a potentially better safety profile by minimizing off-target effects.
Chronology of Development: From Acquisition to Clinical Presentation
The journey of AJ1-11095 to this pivotal Phase I data presentation is rooted in strategic acquisition and prior collaboration. Eli Lilly finalized its acquisition of Ajax Therapeutics in April 2026 for a substantial sum of up to $2.3 billion, contingent upon the achievement of specific clinical and regulatory milestones. This acquisition brought a promising pipeline of JAK inhibitors, including AJ1-11095, under Lilly’s umbrella.
However, the relationship between Lilly and Ajax was not entirely new. Prior to the acquisition, Lilly had demonstrated its belief in Ajax’s potential by participating in the company’s $95 million Series C financing round in 2024. This prior investment signaled Lilly’s early recognition of the therapeutic promise held within Ajax’s research and development efforts.
The presentation of the Phase I data at the 2026 EHA Annual Meeting, held from June 11-14 in Stockholm, Sweden, marks a significant milestone in the drug’s development. This prominent scientific forum provides a platform for researchers and clinicians to share cutting-edge findings and foster scientific discourse within the hematology community.
Future Directions and Broader Implications
The promising results from the AJX-101 study have paved the way for further clinical investigation of AJ1-11095. The drug is currently being evaluated in an expansion cohort for second-line myelofibrosis, aiming to solidify its efficacy and safety in a larger patient population.
Beyond its current indication, Lilly has ambitious plans to explore AJ1-11095 in other myeloproliferative neoplasms (MPNs). Specifically, the company intends to investigate its potential in patients with high-risk polycythemia vera and in individuals with myelofibrosis who have not yet received any JAK2 inhibitor treatment. This broad exploration underscores Lilly’s commitment to leveraging this novel therapeutic across a spectrum of related blood cancers.
The implications of these findings extend beyond the immediate patient benefit. The success of AJ1-11095 could validate the therapeutic strategy of selectively targeting the type II conformation of JAK2, potentially opening doors for the development of similar inhibitors for other inflammatory and autoimmune conditions where JAK signaling plays a critical role. Furthermore, the acquisition of Ajax Therapeutics by Lilly highlights the ongoing consolidation and innovation within the biopharmaceutical industry, particularly in the pursuit of treatments for rare and challenging diseases.
In conclusion, the early Phase I data for Lilly’s AJ1-11095 represents a significant step forward in the fight against myelofibrosis. With a demonstrated ability to improve spleen size, alleviate symptoms, and potentially reduce the underlying disease burden, coupled with a favorable safety profile, this type II JAK2 inhibitor offers a renewed sense of optimism for patients and clinicians alike, signaling a potential paradigm shift in the treatment of this complex blood cancer. The forthcoming clinical trials will be crucial in confirming these promising early findings and ultimately determining the full therapeutic potential of AJ1-11095.
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