British drugs giant GSK has agreed to buy American allergy specialist Rapt Therapeutics in a $2.2bn deal, it was announced on Tuesday.
Under the terms of the deal, GSK will pay Rapt shareholders $58 per share, giving the California-based firm an estimated aggregate equity value of $2.2bn. Net of cash acquired, GSK's estimated upfront investment is $1.9bn.
Loss-making Rapt is a clinical-stage biotech that specialises in developing new drugs for patients with inflammatory and immunologic diseases. Its portfolio includes ozureprubart, a long-acting anti-immunoglobulin monoclonal antibody in phase IIb trials.
The drug is intended to be provide prophylactic protection against food allergens.
Currently around 17m people in the US have food allergies, with more than 1.3m people suffering severe reactions.
Tony Wood, GSK's chief scientific officer, said: "The addition of ozureprubart brings another promising new, potential best-in-class treatment to GSK's pipeline.
"Food allergies cause severe health impacts to patients, with existing treatments requiring injections as frequently as every two weeks. Ozureprubart offers the opportunity to bring sustained protection to patients with dosing every 12 weeks."
Brian Wong, Rapt chief executive, said the deal with GSK offered an "attractive path forward for our programmes".
Once completed, likely by the end of the current quarter, the blue chip will have global rights to ozureprubart excluding mainland China, Macau, Taiwan and Hong Kong.
Rapt was founded in 2015 and floated on Nasdaq in 2019. In the nine months to 30 September 2025, losses were $52.4m, compared to $76.6m a year previously, while research and development expenses were sharply lower, falling to $36.4m from $60.8m.