Eli Lilly is acquiring Ajax Therapeutics for $2.3 billion to obtain AJ1 11095, the first JAK2 inhibitor designed to bind the Type II conformation of the protein, whereas all approved myelofibrosis drugs (Jakafi, Inrebic, Vonjo) target the Type I conformation. The acquisition…
Eli Lilly is buying a drug that does something no approved medicine in its class can do — and it is betting $2.3 billion that the distinction matters.
AJ1-11095, the lead asset of Ajax Therapeutics, is the first JAK2 inhibitor designed to bind the Type II conformation of the JAK2 protein. Every approved JAK2 inhibitor for myelofibrosis — Jakafi, Inrebic, Vonjo — grabs the same shape. When patients stop responding, they have run out of options, because all the drugs on the shelf do the same thing. AJ1-11095 is different in a way that is structurally legible, not just a marketing claim.
"Acquiring Ajax looks to further deepen the company's portfolio development in blood-based myeloproliferative neoplasms," BMO analyst Evan Seigerman wrote in a note to investors Monday. He called AJ1-11095 "a competitive therapy in MPNs where traditional JAK inhibitors have failed." That is a remarkable thing to say about a drug that has not yet produced a single clinical result.
The competitive pressure on traditional JAK inhibitors is not abstract. Three days ago, Constellation Pharmaceuticals reported phase 3 MANIFEST-2 results showing its pelabresib combined with Jakafi drove a 35 percent spleen volume reduction at 24 weeks in 66 percent of patients, compared with 35 percent on Jakafi and placebo. The combination-therapy bar is rising. Separately, Karyopharm said April 21 its selinexor-plus-ruxolitinib Phase 3 SENTRY trial was selected for a late-breaking oral presentation at ASCO in May. The JAK2 field is not standing still.
AJ1-11095 binds a conformation of JAK2 that the approved drugs do not reach. According to the Eli Lilly press release, patients discontinuing existing therapies often do so because they lose response. Ajax designed AJ1-11095 to deliver deeper and more durable efficacy and to address patients who have exhausted Type I options. The drug is also being developed for polycythemia vera, a related blood disorder.
The deal is small by Lilly's recent standards — $2.3 billion against a $7 billion ceiling for Kelonia three weeks ago and a $2.4 billion deal for Orna in February. The terms were not broken out between upfront and milestones, which would have clarified what Lilly is actually paying today versus what it is paying for results. The transaction is expected to close in the second half of 2026, pending Hart-Scott-Rodino review.
The Phase 1 trial, AJX-101, began in late 2024 and is enrolling myelofibrosis patients previously treated with a Type I JAK2 inhibitor. Proof-of-concept data is expected later in 2026. AJ1-11095 has received FDA orphan drug designation. Lilly has been a strategic investor in Ajax since the company's inception in 2021, co-founding it with Schrödinger, the computational chemistry company whose structure-based drug design platform was used to engineer the Type II binding geometry. Schrödinger's most tangible validation to date is a computationally designed molecule commanding a nine-figure acquisition price before it has shown a single clinical result.
Ajax was co-founded by Ross Levine, chief scientific officer at Memorial Sloan Kettering Cancer Center and chair of Ajax's scientific advisory board. Martin Vogelbaum is co-founder and chief executive.
Lilly's dealmaking pace in oncology has compressed to roughly one acquisition per week for the past month. In January it bought Scorpion Therapeutics for up to $2.5 billion. The Ajax deal is the fourth in that stretch. Scotiabank analyst Louise Chen said the acquisition builds on Lilly's established capabilities in blood cancers and helps expand its future commercial products beyond obesity — the therapeutic area that has defined the company for the past two years.
Jakafi generated $2.8 billion in 2024 sales and its patents expire around 2028. The myelofibrosis market is projected to grow from roughly $2.6 billion to $5.6 billion by 2034, according to DelveInsight market analysis. AJ1-11095 would enter as Jakafi's generics erode rather than competing against an intact franchise. Whether a Type II binder can command that window depends on data that will not exist for another year or more.