Rapt Therapeutics has charted a new course following the implosion of its lead program, agreeing to pay $35 million for a long-acting challenger to Novartis and Roche’s Xolair.
The California-based biotech went into 2024 focused on zelnecirnon, a CCR4 agonist that was in phase 2 atopic dermatitis and asthma trials. However, the FDA put the trials on hold in February in response to a case of liver failure. Rapt stopped the studies early in May and axed the program in November, putting a hole in the biotech’s clinical-phase pipeline.
A deal with Shanghai Jemincare Pharmaceutical has filled the hole. Rapt is paying $35 million upfront, plus up to $672.5 million in milestones, for ex-China rights to a half-life extended anti-immunoglobulin E (IgE) antibody that is in clinical development at Jemincare.
The Chinese biotech is studying the antibody, which Rapt calls RPT904, in phase 2 trials in asthma and chronic spontaneous urticaria. But Rapt is prioritizing development in food allergy and planning to start a phase 2b trial in the indication next year.
Rapt’s interest in food allergy is underpinned by the success Xolair is enjoying in the indication. The FDA approved Novartis and Roche’s anti-IgE antibody for use in people with certain food allergies in February. Rapt has been following Roche’s updates on the launch, telling investors 30,000 food allergy patients were on the drug after its first two quarters on the market.
While Xolair has burst out of the blocks, Rapt has market research showing payers and prescribers would welcome a longer-acting alternative. Xolair is given every two to four weeks. If RPT904 can match Xolair’s safety and efficacy while extending dosing to every eight weeks, Rapt said the antibody could be used in 16% of moderate-to-severe food allergy patients.
Rapt estimates peak U.S. food allergy sales could hit $4.5 billion. The biotech predicts that the development of the antibody in chronic spontaneous urticaria, another indication in which Xolair is approved, could add another $1 billion in revenue.
The forecasts reflect Rapt’s belief RPT904 is a best-in-class molecule. RPT904 will need to be better than Xolair to make a mark. While Roche no longer expects a Xolair biosimilar to launch in the U.S. in 2025, off-patent challengers are coming. Rapt said RPT904 could command at least 30% premium over Xolair biosimilars because its long-acting design may increase compliance and convenience.
RPT904 targets the same epitope as Xolair but features tweaks intended to extend half life, boost affinity and reduce the potential for immunogenicity. Jemincare’s phase 1 trial showed RPT904 had a half life of 63 days, compared to 27 days for Xolair, and achieved superior IgE reduction than Novartis and Roche’s product.
Investors have bought into Rapt’s plan, funnelling $150 million into the biotech. The investment extends the biotech’s cash runway beyond the anticipated delivery of phase 2b food allergy data in the first half of 2027.