Allergy pill developer RAPT soars on announcement of acquisition by GSK

Shares of RAPT Therapeutics, a developer of long-acting therapies for food allergies, surged nearly 64% in premarket trading on Tuesday, January 20, after the company announced its acquisition at a premium by pharma giant GSK.

RAPT shares soared 63.8% to $57.50 per share in early trading on Tuesday.

The rally followed the announcement that GSK will acquire RAPT for $2.2 billion, or $58 per share in cash, the companies said in a statement. At the close of trading on Friday, RAPT shares were priced at $35.10 per share. The offer thus implies a premium of about 65% versus the last closing level, as U.S. markets were closed on Monday for a public holiday.

The transaction is expected to close in the first quarter of 2026.

RAPT develops therapies for inflammatory and immunologic diseases. Its lead experimental asset, ozureprubart, is being developed for prophylactic protection against food allergies and is currently in phase II clinical trials.

The key differentiator of ozureprubart versus peer therapies is dosing frequency. Standard food allergy treatment typically requires injections every 2-4 weeks, which can be burdensome for patients, particularly children, the press release noted. Ozureprubart is designed for dosing once every 12 weeks, which the companies believe could improve adherence and patient outcomes.

In addition, ozureprubart could expand access to treatment. Existing therapies are not suitable for about 25% of patients with food allergies, according to the companies. In the U.S. alone, more than 17 million people are diagnosed with food allergies.

RAPT is developing ozureprubart in collaboration with Shanghai Jeyou Pharmaceutical, which holds rights to the therapy in mainland China, Macau, Taiwan, and Hong Kong. These territories are excluded from the GSK transaction. Under the agreement, GSK will assume responsibility for milestone and royalty payments owed to Shanghai Jeyou under its partnership with RAPT.

Over the last 12 months, RAPT shares have gained about 268%.

The stock has 11 “buy” ratings versus one “hold” from Wall Street analysts, MarketWatch data shows. The average target price stands at $67.80 per share, implying upside of roughly 93% versus the Friday close.