Lilly Spent $2.3B on a Drug Nobody Had Tested in Humans. It Might Already Be Working.
Eli Lilly paid up to $2.3 billion for Ajax Therapeutics before its JAK2 inhibitor had ever proven it worked in humans. The first clinical data just landed, and the early numbers are turning heads in the myelofibrosis world.
The Fastest $2.3 Billion Gut Check in Pharma
Back in April, Eli Lilly agreed to pay up to $2.3 billion for Ajax Therapeutics, a small biotech with a single drug that had barely started testing in people. The bet: a new kind of JAK2 inhibitor that works differently from every blood cancer drug on the market. Plenty of observers raised an eyebrow. The drug was still in Phase 1. There was no proof it actually worked.
Seven weeks later, the first real data just dropped at the European Hematology Association (EHA) congress in Stockholm. And according to Lilly oncology chief Jake Van Naarden, the drug "started working right out of the gate."
That's an unusually bold thing for a pharma executive to say about a Phase 1 asset. So is the data bold enough to back it up?
A Lock, Not a Dimmer Switch
To understand why this matters, you need a quick primer on how these drugs work.
Myelofibrosis is a rare blood cancer where the bone marrow goes haywire, producing scar tissue instead of healthy blood cells. Think of it like your body's blood factory slowly replacing its workers with concrete. The result: an enlarged spleen, crushing fatigue, anemia, and a shortened life.
For a decade, the go-to treatments have been Type I JAK inhibitors like ruxolitinib. These drugs dial down a hyperactive protein called JAK2, offering real symptom relief. But they don't kill the underlying problem. The mutant cells survive. Over time, many patients stop responding. There's no universally accepted backup plan after that.
Ajax's drug, AJ1-11095, takes a fundamentally different approach. Instead of turning down JAK2 after it fires up (like a dimmer switch), it locks JAK2 in its inactive position from the start. It's the difference between lowering the volume on a blaring speaker and unplugging the speaker entirely.
That's why it's called a Type II inhibitor: the first of its kind to reach human testing for myelofibrosis.
Get tomorrow's biotech intelligence before your competitors.
Join thousands of biotech professionals who start their day with our free, daily briefing.
The Phase 1 trial (called AJX-101) enrolled 23 patients, all of whom had already failed a standard Type I JAK inhibitor. This is the toughest crowd to impress: people whose disease had already outsmarted the best available therapy.
The headline number is striking. About 70% of patients achieved a major spleen volume reduction (at least 35% shrinkage), which is the standard benchmark in myelofibrosis trials. In this same population, historical response rates to existing drugs are much lower.
Symptoms improved too. Roughly 70% of patients saw their total symptom score cut in half or more by week 12. For a disease that leaves people exhausted, in pain, and barely functional, that's a meaningful change in daily life.
But the most provocative signal involves something deeper: the mutant cells driving the disease. In 21 out of 23 patients, the drug reduced the burden of driver gene mutations (the genetic fuel behind the cancer). Among those treated for at least 24 weeks, 35% saw their mutation burden drop by half or more. Type I JAK inhibitors almost never do that. This is the kind of finding that makes researchers whisper the words "disease modification" in hushed, hopeful tones.
Clean Enough to Keep Going
JAK inhibitors have baggage. The entire drug class carries safety concerns: suppressed blood counts, infection risk, liver problems. The FDA has slapped warnings on other JAK drugs for issues ranging from blood clots to secondary cancers. That history is exactly why investors have been cautious about anything with "JAK" in the name.
So the safety profile matters enormously here. And so far, it looks encouraging.
The trial reported zero dose-limiting toxicities. About 78% of patients in the dose-escalation phase were still on treatment at the data cutoff (May 12, 2026). Five patients discontinued, but none because of drug-related side effects. The most common issues were anemia, altered taste, low platelets, and mild liver enzyme bumps; all described as "generally manageable."
For a Phase 1 trial in sick, heavily pretreated patients, that's a clean scorecard. It doesn't guarantee long-term safety, but it removes the biggest early red flag.
Wall Street Shrugged (For Now)
You might expect data like this to send Lilly's stock soaring. It didn't. Shares actually dipped about 2.4% on the day of the readout, worse than Lilly's average move after clinical updates.
The reason is simple math. Lilly's market cap is enormous, powered by its GLP-1 obesity and diabetes juggernaut. A Phase 1 drug in a rare blood cancer, no matter how promising, barely registers on the earnings model. Analysts are treating AJ1-11095 as a "long-dated call option" on hematology: real upside if it works, but years away from revenue.
RBC Capital had already flagged that Lilly's own prior JAK2 program failed, and that Ajax hadn't yet shown full proof of concept when the deal was announced. Still, the bank called the science "grounded" and the strategic logic clear. Most Street models won't assign meaningful value to this program until a larger trial confirms durability.
The Bigger Picture: Lilly's Shopping Spree
Ajax isn't a one-off purchase. It's part of a deliberate strategy to recycle GLP-1 profits into oncology and hematology. By mid-2026, Lilly has committed over $10 billion upfront across six acquisitions, with total potential payouts reaching $25 billion. Half of those deals are cancer-focused.
The Ajax buy sits alongside a $7 billion deal for Kelonia Therapeutics (an in-body CAR-T platform for blood cancers) and a $2.5 billion acquisition of Scorpion Therapeutics (precision breast cancer). Lilly is building a diversified oncology franchise, one big check at a time.
What Comes Next
Lilly expects to finalize the Ajax acquisition subject to customary closing conditions including HSR antitrust approval, with dose selection for later-stage development also targeted for this year. If the profile holds up in more patients and over longer follow-up, the company could move quickly toward a registrational (approval-seeking) trial. The dream scenario: expanding beyond second-line myelofibrosis into first-line treatment and other blood cancers like polycythemia vera.
That's a lot of "ifs." Twenty-three patients is a napkin sketch, not a masterpiece. Response rates can look stunning in small trials and fade as the numbers grow. The cytopenias and liver signals bear watching.
But as far as early bets go, this one is off to a running start. Lilly paid $2.3 billion for a hunch that locking JAK2 in its off position could change myelofibrosis treatment. Seven weeks in, the hunch is looking pretty good.
Clinical & Regulatory
5 min read
Prostate Cancer Just Got Its HER2 Moment
The FDA just approved the first targeted therapy for a specific genetic subtype of prostate cancer, turning PTEN loss from a bad prognosis into an actionable target. It's the same precision oncology playbook that transformed breast cancer, and it could reshape how we treat the most common male cancer.
