RAPT Therapeutics stock surged an extraordinary 64% on January 20, 2026, following the announcement that pharmaceutical giant GSK will acquire the immunology-focused biotech company for $2.2 billion. The all-cash deal values RAPT at $58 per share, representing a significant premium over the company’s closing price of $35.10 on January 16.
This acquisition marks one of the first major pharmaceutical deals of 2026 and underscores GSK’s strategic focus on strengthening its immunology portfolio, particularly in the food allergy treatment space.
GSK Deal Highlights and Strategic Implications
GSK’s $58-per-share offer represents a substantial premium, with RAPT’s stock jumping from $35.10 to approximately $57.52 as of mid-morning trading on January 20. Pre-market trading showed the stock reaching $57.41, demonstrating strong investor confidence in the deal’s completion. Trading volume exploded to over 17.2 million shares compared to the average daily volume of just 455,304 shares, reflecting the dramatic market reaction to the announcement.
The centerpiece of this acquisition is ozureprubart, RAPT’s long-acting anti-immunoglobulin E (IgE) antibody candidate for food allergy prophylaxis. GSK will gain global commercial rights to the drug outside of China, Taiwan, Macau, and Hong Kong. Ozureprubart is currently being evaluated in the Phase IIb prestIgE study enrolling patients in the US, Australia, and Canada, with results expected in 2027. The drug’s once-quarterly dosing schedule represents a significant advantage over existing treatments like Xolair, which require dosing every two to four weeks.
GSK views ozureprubart as a potential “best-in-class” medication if approved, given its superior convenience and ability to treat patients with high IgE levels or body weight who aren’t eligible for current therapies. The drug demonstrates four times higher affinity than Xolair and can remove bound IgE. The food allergy market represents a substantial opportunity, with over 17 million diagnosed patients in the US alone, including approximately 6 million children, and about 40% of patients allergic to multiple foods.
Market Reaction and RAPT's Financial Performance
As of 10:24 AM EST on January 20, RAPT stock was trading at $57.52, up $22.42 or 63.89% from the previous close. The stock opened at $57.46 and has traded in a tight range between $57.46 and $57.61 throughout the day. The company’s market capitalization surged to approximately $1.595 billion following the announcement. RAPT’s 52-week range has been dramatic, from a low of $5.66 to the current high of $57.61, illustrating the transformative impact of GSK’s acquisition offer.
The acquisition comes as GSK fortifies its pipeline amid an industry-wide patent cliff, with potential losses of $230 billion to the US market between 2025 and 2030 affecting more than half of the top 15 pharmaceutical companies. GSK has been actively pursuing immunology deals, having previously signed a $12 billion agreement with Hengrui Pharma and a five-year £50 million R&D partnership with the University of Cambridge. This strategic focus on immunology represents the company’s effort to offset future revenue losses from patent expirations.
Following the deal announcement, the one-year target estimate for RAPT stands at $68.75, though analyst ratings have already begun adjusting to the acquisition price. Clear Street downgraded the stock to Hold with a lowered price target of $58, reflecting the acquisition offer. The company’s year-to-date return has skyrocketed to 69.91%, while its one-year return reached an impressive 499.48%, driven almost entirely by today’s acquisition news.