New York, Jan 20, 2026, 10:20 ET — Regular session.
- RAPT shares surged about 64%, ending at $57.54—just shy of GSK’s $58-a-share cash offer.
- GSK is snapping up the biotech to add ozureprubart—a longer-acting anti-IgE drug—to its pipeline; the treatment is now being tested for food allergies.
- Investors are focused on when tender offers will land and the pace of U.S. antitrust approvals as a busy week of data and earnings looms, heightening market nerves.
RAPT Therapeutics shares jumped about 64% Tuesday, reaching $57.54 in early Nasdaq action. The uptick followed Britain’s GSK unveiling a cash acquisition offer of $58 per share for the U.S. biotech firm.
GSK’s deal values RAPT at $2.2 billion, securing a promising experimental food allergy treatment as drugmakers race to broaden their immunology offerings.
Wall Street’s main indexes fell early on as new tariff threats stirred worries, triggering a risk-off reaction that left only a handful of stocks linked to recent deals showing gains. “The headlines are going to drive angst and concern about what the future holds,” said David Lundgren, chief market strategist at Little Harbor Advisors. 1
Ozureprubart, an engineered antibody aimed at immunoglobulin E (IgE), which drives allergic reactions, is central to the acquisition. GSK and RAPT have positioned the drug as a less frequent dosing option compared to existing anti-IgE injections.
GSK pointed out that “Ozureprubart offers the opportunity to bring sustained protection to patients with dosing every 12 weeks.” Brian Wong, CEO of RAPT, called the deal “an attractive path forward for our programs.” GSK also flagged that data from RAPT’s phase IIb prestIgE study is due in 2027. 2
GSK’s offer values RAPT at a 65.2% premium over its Monday close of $35.10. RAPT’s shares jumped to $57.50 in U.S. premarket trading and held near that level after hours. Jefferies analyst Michael Leuchten said, “I like the fact that food allergy is not a crowded market at the moment.” Barclays analysts, however, cautioned that the asset is more early-stage than expected for GSK, especially given upcoming HIV patent expiries. 3
A filing showed that GSK’s U.S. arm intends to launch a cash tender offer for all outstanding RAPT shares within 10 business days of signing. The acquisition hinges on a majority of shares being tendered and passing the Hart-Scott-Rodino antitrust review, which enforces a waiting period before deals can close. 4
RAPT shareholders have little room for near-term upside unless a new bidder emerges—something common when a small biotech is handed a full-cash offer at a steep premium.
But the deal isn’t set in stone. Extended regulatory scrutiny, hold-ups in the tender process, or legal challenges could all slow things down. On top of that, ozureprubart is still in mid-stage development — highlighting that GSK is betting on future data and commercial payoff that haven’t materialized yet.
Next up are the formal tender offer documents and RAPT’s board recommendation filing, both set to come before the offer kicks off. The U.S. economic calendar is packed this week too, with GDP, PMI data, and the PCE inflation report all due, plus key earnings releases. GSK expects the deal to close in the first quarter of 2026.
