On Tuesday, GSK plc (NYSE: GSK) declared its intention to acquire RAPT Therapeutics Inc. (NASDAQ: RAPT) through a definitive agreement setting the purchase price at $58.00 per share. This consideration translates into an estimated aggregate equity valuation of $2.2 billion. After accounting for cash acquired in the transaction, GSK’s projected upfront financial commitment totals $1.9 billion.
RAPT Therapeutics, headquartered in California, is a clinical-stage biopharmaceutical company focusing on creating innovative therapies targeting inflammatory and immunologic conditions. The acquisition notably includes ozureprubart, a long-acting anti-immunoglobulin E (IgE) monoclonal antibody currently undergoing phase 2b clinical trials for prophylactic intervention aimed at mitigating food allergen reactions.
IgE represents a clinically validated target in allergies and inflammation, serving as the sole systemic therapy with regulatory approval to prevent detrimental allergic immune responses. Approximately 94% of severe food allergy cases stem from IgE-mediated mechanisms. Present treatments targeting IgE mandate injections every two to four weeks. Ozureprubart distinguishes itself by potentially enabling dosing every 12 weeks, promising enhanced patient adherence and clinical outcomes. Additionally, this therapy could offer treatment options to nearly 25% of patients ineligible for current anti-IgE therapies. The candidate’s development aligns well with GSK’s broad allergy treatment portfolio and prescribing foothold.
Data from the ongoing phase 2b trial, named prestIgE, are expected in 2027. Subsequently, phase 3 trials will concentrate on both adult and pediatric populations considered at risk. The deal grants GSK global rights to ozureprubart with the exception of mainland China, Macau, Taiwan, and Hong Kong. Furthermore, GSK will assume responsibility for milestone payments and potential royalties linked to RAPT’s collaboration with Shanghai Jeyou Pharmaceutical Co., Ltd.
Market Landscape for Food Allergy Therapeutics
Within the United States, the prevalence of diagnosed food allergies exceeds 17 million individuals, including more than 1.3 million who have experienced severe allergic reactions. The healthcare burden is underscored by over 3 million hospital and emergency department visits annually related to food allergies. These figures indicate a significant unmet medical need and a sizable market opportunity for innovative prophylactic therapies addressing this condition.
Management Insights on Strategic Fit
GSK’s Chief Scientific Officer, Tony Wood, emphasized that ozureprubart enriches GSK’s pipeline with a candidate possessing the potential to become a best-in-class allergy treatment. He highlighted the advantages of longer-lasting protective effects and quarterly dosing schedules in addressing critical unmet needs in food allergy management.
Brian Wong, CEO of RAPT Therapeutics, expressed that the acquisition provides ozureprubart a clear and accelerated pathway to market by leveraging GSK’s comprehensive global development resources and commercial infrastructure. This synergy is expected to enhance both patient access and shareholder value.
Pfizer’s Strategic Divestment from ViiV Healthcare
In a related development, Pfizer Inc. (NYSE: PFE) announced the planned exit from its 11.7% equity interest in ViiV Healthcare, a company specializing in HIV drug development. Shionogi Co. Ltd. will augment its ownership stake from 17.7% to 21.7%, while GSK will maintain a majority share of 78.3% in ViiV Healthcare.
ViiV Healthcare will issue new shares to Shionogi for $2.125 billion. Concurrently, Pfizer will receive $1.875 billion in return for its divestiture. Additionally, GSK is set to receive a special dividend of $250 million, payable in British pounds and related to this transaction. Shionogi will continue to have representation on ViiV Healthcare’s board through Dr. John Keller, who has served as a director since 2012.
Transaction Timing and Market Impact
Both the acquisition of RAPT Therapeutics by GSK and Pfizer’s divestment from ViiV Healthcare are expected to conclude during the first quarter of 2026. Following the announcement, RAPT Therapeutics’ shares surged by more than 63% during premarket trading, reaching $57.40 and setting a new 52-week high as per Benzinga Pro data. GSK’s stock experienced a marginal increase of 0.04%, while Pfizer’s shares declined by 0.51% in early trading.
Summary
This series of transactions reflects notable shifts within the biotechnology and pharmaceutical industries, with GSK fortifying its presence in the immunologic and allergy therapeutic space, and Pfizer realigning its portfolio through the sale of its stake in HIV specialist ViiV Healthcare. The deal is strategically significant for GSK as it will gain access to a promising novel therapy with the potential to address high unmet needs in food allergy prophylaxis.