GSK’s agreement to acquire RAPT Therapeutics for $58 per share in cash underscores a growing trend in biotech investing: large pharmaceutical companies are increasingly turning to small-cap innovators to fill critical gaps in their pipelines. For small-cap investors, the deal offers a clear example of how differentiated science, even at the clinical-stage level, can command a meaningful premium.
Under the terms of the agreement, GSK will acquire RAPT Therapeutics for an estimated equity value of $2.2 billion, or approximately $1.9 billion net of cash acquired. The transaction is expected to close in the first quarter of 2026, pending customary regulatory approvals and shareholder tender conditions. Shares of RAPT surged following the announcement, reflecting both the attractive takeover premium and validation of the company’s lead asset.
At the center of the deal is ozureprubart, a long-acting anti-immunoglobulin E (IgE) monoclonal antibody currently in Phase IIb development for prophylactic protection against food allergens. IgE is a clinically validated target and is responsible for roughly 94% of severe food allergy reactions, making it one of the most established mechanisms in allergy treatment. However, existing anti-IgE therapies require injections every two to four weeks, creating a significant burden for patients—most of whom are children.
Ozureprubart’s potential differentiator lies in its dosing profile. The therapy is designed to be administered once every 12 weeks, which could dramatically improve patient compliance and expand treatment eligibility to an estimated 25% of patients who are currently unable to use standard therapies. If successful in late-stage trials, ozureprubart could represent a best-in-class option in a market with substantial unmet medical need.
From GSK’s perspective, the acquisition strengthens its Respiratory, Immunology, and Inflammation pipeline and leverages its existing commercial footprint in allergy and immunology. For a company of GSK’s scale, the upfront investment is manageable, while the long-term upside could be significant. In the U.S. alone, more than 17 million people are diagnosed with food allergies, with over 1.3 million experiencing severe reactions that often require emergency care.
For small-cap investors, the RAPT deal is instructive. RAPT was a clinical-stage company without an approved product, yet it attracted a multibillion-dollar buyout based on a single, well-positioned asset targeting a validated pathway. This reinforces the idea that big pharma is willing to pay for de-risked science, especially when it addresses large, underserved markets and fits cleanly into an existing commercial infrastructure.
The transaction also highlights the importance of platform credibility. RAPT’s focus on immunology and its ability to advance ozureprubart into mid-stage clinical development made it a credible acquisition target rather than a speculative bet.
While not every small-cap biotech will see a similar outcome, GSK’s acquisition of RAPT Therapeutics serves as a reminder that disciplined execution, clear differentiation, and alignment with big pharma priorities can create substantial shareholder value—even before commercialization.