GSK plc (GSK) is making a substantial bet on food allergies, agreeing Tuesday to acquire RAPT Therapeutics Inc. (RAPT) for $58.00 per share. The deal values the California-based biotech at roughly $2.2 billion in total equity, though GSK's actual upfront investment comes to about $1.9 billion after accounting for RAPT's existing cash.

What's GSK buying, exactly? The centerpiece is ozureprubart, a drug that could change how people with severe food allergies manage their condition. Right now, if you're one of the millions of Americans dealing with potentially life-threatening reactions to peanuts or other common foods, your systemic treatment options involve getting injected every two to four weeks. That's a lot of doctor visits and a lot of needles.

Ozureprubart works differently. It's a long-acting monoclonal antibody that targets immunoglobulin E, or IgE, which is the molecule responsible for about 94% of severe food allergic reactions. The key innovation here is duration: clinical data suggests ozureprubart could be dosed just once every 12 weeks. That's quarterly instead of bi-weekly, which matters enormously for patient compliance and quality of life.

A Growing Market With Clear Unmet Needs

The food allergy market is both large and expanding. In the United States alone, more than 17 million people have been diagnosed with food allergies. Of those, over 1.3 million suffer severe reactions each year, generating more than 3 million hospital and emergency care visits annually. That's a lot of EpiPens and a lot of anxiety.

Current anti-IgE therapies work, but they have limitations. Beyond the frequent dosing schedule, roughly 25% of patients aren't even eligible for existing treatments. Ozureprubart's clinical profile could potentially address both problems, offering less burdensome dosing while expanding the treatable patient population.

The drug is currently in phase 2b development, with a trial called prestIgE evaluating ozureprubart as a monotherapy. Results from that study are expected in 2027, and phase 3 trials will focus on both adult and pediatric populations who are at risk of severe allergic reactions.

Strategic Fit and Geographic Rights

For GSK, the acquisition fits neatly into its existing allergy franchise. The company already has substantial commercial infrastructure and an established prescriber base in allergy treatment, so ozureprubart complements what's already there rather than requiring GSK to build capabilities from scratch.

The deal gives GSK global rights to ozureprubart, with one notable exception: mainland China, Macau, Taiwan, and Hong Kong are carved out. RAPT has a partnership with Shanghai Jeyou Pharmaceutical Co., Ltd. for those territories, and GSK will be responsible for any success-based milestones and royalty payments owed to that partner.

What Management Is Saying

Tony Wood, GSK's chief scientific officer, emphasized that ozureprubart strengthens the pipeline with what could be a best-in-class allergy treatment. The quarterly dosing schedule offers longer-lasting protection and addresses what he called "a clear unmet need in food allergy care."

RAPT Therapeutics CEO Brian Wong framed the deal as giving ozureprubart the resources it needs to reach patients. Pairing the program with GSK's global development capabilities and commercial scale, he said, unlocks greater value for both patients and shareholders.

Meanwhile, Pfizer Exits ViiV Healthcare

In a related but separate transaction announced the same day, Pfizer Inc. (PFE) is exiting its 11.7% stake in ViiV Healthcare, an HIV drug developer in which GSK holds the majority position. ViiV will issue new shares to Shionogi Co. Ltd. for $2.125 billion, increasing Shionogi's stake to 21.7%, while GSK maintains its 78.3% majority share.

Pfizer will receive $1.875 billion from the transaction, and GSK will get a $250 million special dividend payable in British pounds. Shionogi will continue to have one director position on ViiV's board, represented by Dr. John Keller, who has served as a director since 2012.

Both the RAPT acquisition and the ViiV restructuring are expected to close in the first quarter of 2026.

Market Reaction

RAPT Therapeutics (RAPT) shares surged 63.53% to $57.40 in premarket trading Tuesday, hitting a new 52-week high. That makes sense when you're getting acquired at $58. GSK (GSK) shares edged up 0.04%, while Pfizer (PFE) dipped 0.51%.