Lilly lands third oncology deal in 3 weeks, inking up to $2.3B for Ajax

Eli Lilly Acquires Ajax Therapeutics for Up to $2.3B

Eli Lilly is acquiring Ajax Therapeutics for up to $2.3 billion, marking its third oncology deal in three weeks. The acquisition focuses on Ajax's lead program, AJ1-11095, a next-generation JAK2 inhibitor. This oral candidate is designed to treat myeloproliferative neoplasms (MPNs), including myelofibrosis and polycythemia vera, by offering a unique binding mechanism. AJ1-11095 is currently in a Phase 1 trial for myelofibrosis patients previously treated with a JAK2 inhibitor and has secured FDA orphan drug status, aiming to provide more durable disease control than current therapies.

• Eli Lilly is acquiring Ajax Therapeutics for a potential sum of up to $2.3 billion, which includes an undisclosed upfront payment and subsequent clinical and regulatory milestone payments. This strategic move is part of Lilly's recent aggressive expansion in oncology, marking its third cancer-related acquisition in as many weeks, following deals for CrossBridge Bio and Kelonia Therapeutics.
• The core of the acquisition is Ajax's lead program, AJ1-11095, a clinical-stage, once-daily oral JAK2 inhibitor. This asset is specifically developed to treat myeloproliferative neoplasms (MPNs), such as myelofibrosis and polycythemia vera, by offering a unique mode of binding JAK2 (type II conformation) that is expected to provide more durable disease control compared to existing type I JAK2 inhibitors like Incyte’s Jakafi.
• AJ1-11095 is currently undergoing a Phase 1 trial in patients with myelofibrosis who have previously received an approved JAK2 inhibitor. Ajax anticipates releasing proof-of-concept data from this trial later in the year. The drug has also been granted FDA orphan drug status, highlighting its potential to address unmet needs in these rare blood cancers and accelerate its development pathway.

AJ1-11095: A Novel Approach to JAK2 Inhibition in MPNs

Recent research has identified several promising therapeutic targets beyond traditional JAK2 inhibition for myeloproliferative neoplasms. ULK1 kinase has emerged as a particularly compelling target, with 2025 studies demonstrating its essential role in MPN pathophysiology downstream of hyperactive JAK2 signaling. Genetic or pharmacological targeting of ULK1 substantially delays disease development in JAK2-mutant MPN models, reducing early stage erythroid progenitors, hemoglobin levels, and spleen size. Additionally, novel macrocyclic JAK2 inhibitors have been developed to address limitations of current therapies, with lead compounds showing potent JAK2 inhibition (IC₅₀ = 54.70 nM), excellent bioavailability (54.8%), and effective downregulation of p-STAT3 and p-STAT5 pathways.

The immune microenvironment has become a focal point for therapeutic intervention, with researchers targeting pro-inflammatory cytokines including IL-2, IFN-α, IL-23, and TNF-α that drive pathogenic Th17 cell polarization. CALR-mutated MPNs present unique immunotherapeutic opportunities through anti-CALR antibodies and T-cell receptor-mediated therapies targeting the mutant protein. The tumor microenvironment is further being addressed through CXCR1/2 antagonists targeting GRO-α signaling, anti-TGF-β agents for fibrosis reduction, and immune checkpoint inhibitors targeting exhausted PD-1+ T cells that reflect impaired immune surveillance.

Innovative technological approaches are expanding the therapeutic landscape, including mitochondria-targeted antioxidants to address mitochondrial dysfunction and reactive oxygen species production, and RNA-exosome complex modulation targeting JAK2V617F ssDNA release and DNA-sensing pathways like cGAS-STING and TLR9. Advanced delivery systems through nanoparticle-mediated drug delivery, gene editing technologies, and RNA-based therapies are under development. Notable clinical progress includes OB756, a selective JAK2 inhibitor achieving 22% complete hematologic response rates and 50% achieving ≥35% spleen volume reduction in phase 2 trials, and combination approaches pairing JAK inhibitors with BCL-XL inhibitors to overcome treatment resistance.

Addressing Unmet Needs in Myeloproliferative Neoplasms Treatment

Current treatment approaches for myeloproliferative neoplasms face significant limitations that prevent optimal patient outcomes. While JAK inhibitors represent a major advance in MPN management, they address only a subset of disease manifestations and fail to provide curative therapy for most patients. These challenges necessitate continued development of novel therapeutic strategies.

• Limited molecular response with JAK inhibitors - Despite being standard of care for myelofibrosis, only a minority of patients achieve significant molecular-level responses with JAK inhibitor therapy, and additional agents are necessary for patients who do not respond to the one FDA-approved JAK1/JAK2 inhibitor

• Absence of curative medical therapy - The cure of myelofibrosis remains an unmet clinical need, as identification of molecular lesions has not yet translated into treatments that can modify the natural history of the disease, with hematopoietic stem cell transplantation being the only potentially curative option limited to patients with compatible donors and appropriate age/functional status

• Significant treatment-related toxicity - Interferon-α2 use is limited by inflammation-mediated toxicity leading to discontinuation in 10-30% of patients, while ruxolitinib toxicity primarily affects erythropoiesis and thrombocytopoiesis requiring careful dose management

• JAK inhibitor-specific limitations - Janus kinase inhibitors have inherent disadvantages including toxicity, resistance development, withdrawal phenomenon, non-reversal of bone marrow histology, and inability to eradicate the disease clone, with off-target effects from clinically relevant dosing contributing to both efficacy and toxicity

• Incomplete disease control in polycythemia vera - Current treatment for polycythemia vera is limited and primarily targets thrombosis risk rather than addressing underlying disease mechanisms, with opportunities remaining to improve efficacy and decrease risk of disease progression

• Need for dual targeting approaches - Achieving cure will likely require targeting both the malignant stem cell clone and its supportive microenvironment, as current single-agent approaches fail to address the complex pathophysiology of these disorders

Lilly's Bold Move to Redefine JAK2 Inhibition in MPNs

Eli Lilly's recent acquisition of Ajax Therapeutics, highlighted by the lead program AJ1-11095, signals a significant strategic maneuver within the oncology space, particularly in the realm of myeloproliferative neoplasms (MPNs). The discovery of the JAK2 V617F mutation revolutionized the understanding and treatment of MPNs, leading to the development of JAK2 inhibitors like ruxolitinib. These agents have profoundly improved patient quality of life by reducing splenomegaly and constitutional symptoms, and even extending overall survival in intermediate- to high-risk myelofibrosis patients.

However, the journey with JAK inhibitors has revealed persistent challenges. Many patients experience resistance or intolerance over time, with a substantial proportion discontinuing therapy within a few years. A critical limitation is the common occurrence of cytopenias, such as anemia, which can be exacerbated by JAK inhibitors and significantly impact patient management. Furthermore, current JAK inhibitors, while effective symptomatically, do not typically eradicate the malignant clone or fundamentally alter the disease's progression.

AJ1-11095, described as a next-generation JAK2 inhibitor with a unique binding mechanism, aims to address these unmet needs. Its focus on previously treated myelofibrosis patients suggests a strategic intent to provide a more durable and potentially safer therapeutic option where existing treatments fall short. The literature indicates that Type II JAK2 inhibitors, which bind differently, may overcome resistance observed with Type I inhibitors like ruxolitinib, offering a promising avenue for improved efficacy. Lilly's move, bolstered by orphan drug status for AJ1-11095, could accelerate its development and market access, positioning the company to capture a high-value segment of the MPN market.

Yet, the path forward is not without its complexities. As an early-stage asset, AJ1-11095 must demonstrate a superior clinical profile in terms of durability, safety, and impact on cytopenias compared to a rapidly evolving competitive landscape. Other novel agents, including different JAK inhibitors (e.g., momelotinib for anemia, pacritinib for thrombocytopenia) and non-JAK inhibitor combinations, are also advancing, creating a crowded field. Ultimately, while AJ1-11095 holds promise for more durable disease control, the fundamental challenge of eradicating the malignant clone in MPNs remains, suggesting that combination therapies may be the eventual key to truly modifying the natural course of these diseases.