New York, Jan 21, 2026, 12:09 EST — Regular session.
RAPT Therapeutics (RAPT.O) hovered near flat on Wednesday, with shares at $57.60 around midday on Nasdaq. The stock inched up roughly 0.05% for the session.
Following Tuesday’s steep reprice, the shares now behave more like a deal spread than a biotech momentum play. This shift is key since the upcoming steps are mostly procedural: filings, launching a tender offer, and then the regulatory wait, which could either widen or narrow the final gap to the bid.
GSK announced it will acquire the California biotech for $58 a share in cash, putting RAPT’s value at roughly $2.2 billion. The deal is set to close in Q1 2026. The target: ozureprubart, a long-acting anti-IgE antibody now in phase IIb trials for food allergies. Since IgE antibodies can trigger allergic responses, this drug aims to be a game-changer. GSK’s Tony Wood called it “another promising new, potential best-in-class treatment,” while RAPT CEO Brian Wong said, “We are excited.” (GSK)
A recent filing revealed GSK will launch a cash tender offer within 10 business days of signing. This offer asks shareholders to sell their stock for cash. Closing hinges on a majority of shares being tendered and the Hart-Scott-Rodino (HSR) waiting period ending, part of the U.S. antitrust review. The buyer isn’t relying on financing to close. The merger deal also imposes “no-shop” restrictions and includes a $78.4 million termination fee if a superior proposal emerges. (SEC)
GSK’s $58-per-share bid values RAPT at a 65.2% premium over Monday’s closing price, Reuters noted. Jefferies analyst Michael Leuchten commented, “I like the fact that food allergy is not a crowded market.” If cleared, ozureprubart would take on Genentech’s Xolair, while Novartis is developing remibrutinib for food allergies, the report added. (Reuters)
RAPT is currently trading roughly 40 cents under the bid. This slight discount typically accounts for time value and the possibility that the process drags on longer than anticipated.
The tight spread makes the stock highly reactive to minor news—whether it’s a tender offer schedule change, a regulatory snag, or hints of rival bids. Even a slight move can alter the implied odds significantly.
Merger trades stall for common reasons — a review gets pushed back, the tender falls short, or a lawsuit drags out the timeline. When that occurs, the spread often widens fast and the stock slips back toward its pre-announcement price.
Investors await the arrival of the tender offer documents and RAPT’s board recommendation, along with the antitrust clock kicking into gear. A fresh timetable from the companies could jolt the shares far more than the usual daily biotech fluctuations.
Next, all eyes turn to the tender offer launch and early nods from U.S. antitrust regulators. The key question: will the final pennies to $58 vanish quickly, or drag out toward the close?
