AJ1-11095’s First Proof-of-Concept Data Signal Potential for a New JAK2 Approach

Lilly’s newly acquired AJ1-11095 has moved beyond the “data expected” stage, with the first proof-of-concept clinical results showing encouraging activity in patients with myelofibrosis who had previously received a Type I JAK2 inhibitor.

The investigational therapy is a first-in-class Type II JAK2 inhibitor originally developed by Ajax Therapeutics. Lilly acquired Ajax in April 2026 in a deal worth up to $2.3 billion, reflecting its confidence that AJ1-11095 could offer a differentiated treatment option for patients whose disease has become resistant to existing JAK2-directed therapies.

From Expected Data to Early Clinical Validation

When Lilly announced its acquisition of Ajax, the company said the first proof-of-concept clinical data for AJ1-11095 would be presented later in 2026.

That milestone arrived at the European Hematology Association (EHA) 2026 Congress, where Lilly presented initial results from the Phase 1 AJX-101 study. The data provided the first clinical evidence supporting the drug's differentiated mechanism.

The trial evaluated AJ1-11095 in patients with myelofibrosis who had previously been treated with a Type I JAK2 inhibitor. The Phase 1 dose-escalation portion enrolled 23 patients across five dose levels, ranging from 25 mg to 125 mg once daily.

A Different Way of Targeting JAK2

The central attraction of AJ1-11095 is its mechanism.

Currently approved JAK2 inhibitors for myeloproliferative neoplasms primarily bind the Type I conformation of the JAK2 kinase. AJ1-11095 was designed to selectively bind the Type II conformation, representing a fundamentally different approach to JAK2 inhibition.

That distinction could be important for patients who eventually lose response to Type I JAK2 inhibitors.

Myelofibrosis is a chronic blood cancer in which patients can experience progressive symptoms, enlarged spleen and worsening disease burden. Although Type I JAK2 inhibitors can provide symptom and spleen-volume benefits, many patients eventually discontinue treatment because of loss of response, insufficient benefit, adverse events or disease progression.

AJ1-11095 is therefore being developed with the possibility of delivering deeper and more durable disease control.

The Early Results Show Multiple Signs of Activity

The first clinical data provide several encouraging signals.

Among the 23 patients enrolled in the dose-escalation portion, a 35% or greater reduction in spleen volume (SVR35) was observed as the best response in 70% of patients.

A 50% or greater improvement in total symptom score (TSS50) was also observed in 70% of patients at Week 12.

The results also produced an important biomarker signal.

Reductions in driver mutation variant allele frequency (VAF) were observed in 21 of the 23 patients. Among the 17 patients who had reached Week 24, 59% experienced a reduction of at least 20%, while 35% achieved reductions of at least 50%. These reductions were observed across JAK2, MPL and CALR mutations.

For Lilly, the VAF findings may be particularly significant because reductions in molecular disease burden are less commonly observed with existing Type I JAK2 inhibitors.

Safety Profile Remains an Important Part of the Story

The early data also provided an encouraging safety signal.

Lilly reported that AJ1-11095 demonstrated an encouraging safety profile across the evaluated dose levels. The most common treatment-emergent adverse events included anemia, dysgeusia, decreased platelet count and increased alanine aminotransferase.

However, these findings remain preliminary.

AJ1-11095 is still being evaluated in Phase 1, meaning that the available patient population is relatively small and longer follow-up will be necessary to determine whether the early efficacy and tolerability signals translate into a clinically meaningful advantage.

Why the Acquisition Now Looks More Strategic

The timing of Lilly's Ajax acquisition is becoming easier to understand in light of the initial clinical results.

Lilly agreed to acquire Ajax for up to $2.3 billion, including payments tied to development and regulatory milestones. At the time, AJ1-11095 was still an early-stage asset, making the transaction a significant bet on both the drug's mechanism and its future clinical potential.

The first proof-of-concept data now provide an initial clinical rationale for that investment.

Rather than simply acquiring another JAK inhibitor, Lilly obtained a program designed around a different binding mode and potentially capable of addressing patients who have exhausted existing Type I JAK2 options.

Lilly Is Expanding the Development Opportunity

The company is not limiting AJ1-11095 to its original patient population.

The program is currently being evaluated in an expansion cohort for second-line myelofibrosis, while Lilly plans to explore the therapy in patients with high-risk polycythemia vera and in patients with myelofibrosis who have not previously received a JAK2 inhibitor.

This could substantially expand the eventual addressable patient population if the drug continues to demonstrate favorable efficacy and safety.

The strategy also reflects Lilly's broader objective of moving AJ1-11095 rapidly through clinical development and toward registrational studies.

What Investors and Competitors Will Watch Next

The current results are encouraging, but several questions remain unanswered.

The most important will be whether the observed responses are durable and whether AJ1-11095 can demonstrate a meaningful advantage over established JAK2 therapies in larger and better-controlled studies.

Future trials will also need to clarify the optimal dose, long-term safety profile and potential role of the drug across different lines of treatment.

The molecular findings will be particularly important. If reductions in VAF continue with longer treatment, AJ1-11095 could potentially differentiate itself not only through symptom and spleen control but also through deeper effects on disease biology.

A Potential New Chapter for JAK2 Therapy

AJ1-11095's first clinical results represent an important transition from scientific rationale to human proof of concept.

The drug is not yet an approved therapy, and the early-stage results should not be interpreted as evidence of definitive clinical superiority. Nevertheless, the combination of spleen-volume reduction, symptom improvement and molecular responses gives Lilly a strong foundation for further development.

The program also illustrates why pharmaceutical companies continue to acquire specialized biotechnology platforms. Ajax had developed a highly focused approach to JAK2 biology, while Lilly brings substantially greater resources and development infrastructure.

If the early signals are confirmed in larger trials, AJ1-11095 could become one of the more closely watched next-generation treatments in myeloproliferative neoplasms.

For now, the key story is no longer that AJ1-11095's proof-of-concept data are expected later in 2026. That milestone has already arrived—and the results give Lilly an early clinical basis for its $2.3 billion bet on Type II JAK2 inhibition.