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Ajax, aiming for a better JAK drug, raises $95M to begin first tests

Medicines called JAK inhibitors are well known in the pharmaceutical industry. Several are approved to treat inflammatory disease conditions or cancer, and regularly bring in billions of dollars in yearly revenue for drugmakers like AbbVie and Pfizer.  

But JAK inhibitors are flawed. They don’t change the course of a disease, and in the last few years, have been linked to serious safety concerns. Those weaknesses have led some startups to look elsewhere in the ongoing search for better immunological drugs.

Ajax Therapeutics, a biotechnology company based in Cambridge, Massachusetts, and New York, has a different idea. With the help of computational drug specialist Schrodinger and research that originated at Memorial Sloan Kettering Cancer Center, Ajax designed a newer type of JAK drug that works differently than others that have come before it. The result, the company says, should be a more precise and potent therapy.

“Nobody’s taking the same approach that we’re that we’re taking to target JAK [enzymes],” said CEO Martin Vogelbaum. 

Ajax will now get a chance to prove those claims. On Monday, it closed a $95 million series C round and said the Food and Drug Administration has cleared the company to begin its first clinical trial. That study will test a drug, codenamed AJ1-11095, Ajax is developing for the bone marrow cancer myelofibrosis. 

The key difference with Ajax’s drug is how it binds to its target. Multiple approved therapies for myelofibroris, like Incyte’s Jakafi or Bristol Myers Squibb’s Inrebic, affect one or more JAK enzymes. But none of them specifically target JAK2 while the enzyme is in an “inactive” state, according to Vogelbaum.

Doing so, the company says, should enable the drug to overcome resistance mechanisms that limit the effectiveness of other JAK medicines. Preclinical research Ajax has presented at a medical meeting hinted at such potential. 

Myelofibrosis is a type of bone marrow cancer that disrupts red blood cell production, leading to symptoms like anemia and fatigue. Though multiple JAK therapies are available, led by Jakafi, they affect symptoms, not the disease’s course, and some have shown in testing that they can worsen anemia. Ajax claims its approach could lead to more powerful results, though that hasn’t yet been proven in trials.

“We believe, fundamentally, that current myelofibrosis therapies aren’t good enough,” said Ross Levine, one of Ajax’s co-founders and a leukemia specialist at Memorial Sloan Kettering. “JAK2 is the one that drives these diseases, and we thought there was an opportunity to drug it better.” 

Ajax’s series C round was led by Goldman Sachs Alternatives, and included participation from Eli Lilly, RA Capital Management and Schrodinger, among others. A collaboration between Ajax and Schrodinger — the firm that worked with Nimbus Therapeutics to discover a so-called TYK2 inhibitor Takeda bought for $4 billion — led to the discovery of its lead molecule.

“We took the [TYK2] team from Schrodinger and poured it into JAK2, given their expertise,” Vogelbaum said. 

Ajax’s last funding round came in 2021, when it brought in $40 million from a group of venture firms and academic research centers. With clinical trials soon on the way, it was able to raise more than twice that number this time around.

“We’re not a company with five different targets and cancers,” Levine said. “We’re not trying to be a platform company. We really do have a clear focus on a target and a disease, with plans, of course, beyond it.”