GlaxoSmithKline (GSK) has agreed to acquire Rapt Therapeutics for $2.2 billion, the companies said today, in a deal intended to bolster the buyer’s pipeline with Rapt’s ozureprubart (RPT904), a mid-phase anti-immunoglobulin E (IgE) monoclonal antibody which is being developed to protect against food allergens.
Ozureprubart is designed for every-12-week dosing, a less frequent dosage than the two- or four-week dosing offered by the current standard of care for food allergy treatments, the Genentech (Roche)/Novartis co-marketed Xolair® (omalizumab).
“The addition of ozureprubart brings another promising new, potential best-in-class treatment to GSK’s pipeline,” Tony Wood, GSK’s chief scientific officer, said in a statement. “Ozureprubart offers the opportunity to bring sustained protection to patients with dosing every 12 weeks and is consistent with our approach to acquire assets that address validated targets and where there is clear unmet medical need.”
In the U.S., more than 17 million people are diagnosed with food allergies, with more than 1.3 million people suffering severe reactions, according to GSK and Rapt, citing data from a study published online in 2022, U.S. Census Bureau data from 2022, MarketScan data, and Optum insurance claims. More than three million patient visits are made each year to hospital and emergency care, according to Food Allergy Research & Education (FARE) data published in 2024.
GSK and Rapt also expect ozureprubart can grow the patient population for food allergy treatment since approximately 25% of patients are now ineligible for existing therapy. The companies also reason that the current standard represents a significant burden, since most current food allergy patients are children.
Investors signaled approval of the deal with a stock buying surge that sent Rapt shares soaring 64% in afternoon trading on NASDAQ, from yesterday’s close of $35.10 to $57.51 as of 1:47 p.m. ET. GSK shares on the London Stock Exchange dipped 2% to close at 1,795.50 pence from 1,816 pence.
Data due in 2027
Ozureprubart is now in the Phase IIb “prestIgE” trial (NCT07220811) designed to assess the drug as monotherapy for prophylactic protection against food allergens, with data from the trial to be released next year. According to ClinicalTrials.gov, April 2027 is the estimated primary completion date for the prestIgE study, a randomized, double-blind, placebo-controlled trial designed to evaluate the safety and efficacy of ozureprubart dosed every eight weeks and every 12 weeks as a treatment for food allergy.
The deal will give GSK global rights to the ozureprubart program worldwide except mainland China, Macau, Taiwan and Hong Kong. GSK will also be responsible for success-based milestone and royalty payments for ozureprubart owed to Rapt’s partner, Shanghai Jeyou Pharmaceutical.
Under the acquisition agreement, a GSK subsidiary will commence a tender offer to acquire all outstanding shares of Rapt common stock for $58 per share in cash within 10 business days of signing. The transaction is subject to customary closing conditions, including the tender of a majority of Rapt’s outstanding shares of common stock in the tender offer and expiration or termination of the applicable waiting period under the under the Hart-Scott-Rodino Act in the U.S.
Following the closing of the tender offer, GSK will acquire any shares of Rapt that are not tendered in the tender offer through a second-step merger under Delaware law at the tender offer price. The transaction is expected to close in the first quarter of this year.
Recouping sales
In acquiring Rapt, GSK is counting on ozureprubart to help it recoup the sales it stands to lose as its mini portfolio of four marketed HIV drugs based on the active ingredient dolutegravir (Tivicay, Triumeq [abacavir/dolutegravir/lamivudine], Juluca [(dolutegravir and rilpivirine], and Dovato [dolutegravir and lamivudine]) approaches a loss of exclusivity with key patents set to expire—notably including a composition of matter patent, in April 2028. For Q1-Q3 2025, the dolutegravir-based HIV drugs racked up a total £4.092 billion ($5.511 billion), barely up 0.2% from £4.083 billion ($5.499 billion) in the year-ago period.
The revenue recouping will be key to GSK fulfilling its goal of achieving annual revenue of more than £40 billion (about $53.9 billion) by 2031.
Ozureprubart targets IgE, which mediates reactions that according to GSK and Rapt cause around 94% of severe food allergies. GSK bases that estimate on an epidemiology assessment using data from MarketScan and Optum claims.
Ozureprubart would join the segment of GSK’s pipeline focused on respiratory, immunology and inflammation drugs, the second largest segment by revenue among the company’s specialty medicines with £2.721 billion ($3.665 billion) generated in the first three quarters of 2025, up 8% from a year earlier (GSK is set to report Q4 and full-year 2025 results on February 4).
GSK’s top revenue segment is HIV drugs, which racked up £5.538 billion ($7.458 billion) in Q1-Q3 2025, of which nearly three quarters (74%) came from the dolutegravir treatments.
“We are excited to enter into this agreement with GSK, which offers an attractive path forward for our programs, particularly the opportunity we envision for ozureprubart in food allergy,” Rapt’s President and CEO Brian Wong stated. “This transaction has the potential to provide access to the global development and commercialization capabilities, resources and infrastructure that GSK has to offer, and ultimately bring added value to our pipeline, patients, and stockholders.”
