New York, Jan 21, 2026, 12:09 EST — Regular session.
RAPT Therapeutics (RAPT.O) held steady on Wednesday, trading around $57.60 midday on Nasdaq. The shares ticked up just 0.05% during the session.
After Tuesday’s sharp reprice, the shares are trading more like a deal spread than a high-flying biotech stock. That matters because what’s next largely boils down to routine moves: filings, kicking off a tender offer, and then waiting on regulators. That process could push the gap to the bid either wider or tighter.
GSK is set to buy the California biotech at $58 a share in cash, valuing RAPT at about $2.2 billion. The deal should wrap up in Q1 2026. The prize here is ozureprubart, a long-acting anti-IgE antibody currently in phase IIb trials targeting food allergies. Since IgE antibodies drive allergic reactions, this drug could shift the landscape. Tony Wood from GSK described it as “another promising new, potential best-in-class treatment,” and RAPT CEO Brian Wong added, “We are excited.” 1
A recent filing shows GSK plans to launch a cash tender offer within 10 business days after signing. The offer invites shareholders to sell their stock for cash. Closing depends 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 counting on external financing to complete the deal. The merger also includes “no-shop” restrictions and a $78.4 million termination fee if a better proposal comes along. 2
GSK’s $58-per-share offer puts RAPT at a 65.2% premium over Monday’s close, Reuters reported. Jefferies analyst Michael Leuchten said, “I like the fact that food allergy is not a crowded market.” If approved, ozureprubart would compete with Genentech’s Xolair. Novartis is also working on remibrutinib for food allergies, the report noted. 3
RAPT is trading about 40 cents below the bid. This small gap usually reflects time value and the risk the process could take longer than expected.
The narrow spread leaves the stock extremely sensitive to small news—be it a tweak in the tender offer timeline, a regulatory hiccup, or whispers of competing bids. Even a modest shift can swing the implied odds sharply.
Merger trades often hit roadblocks for familiar reasons — a delayed review, an underwhelming tender offer, or a drawn-out lawsuit. When that happens, the spread usually blows out quickly, and the stock retreats toward where it stood before the announcement.
Investors are on hold for the tender offer documents and RAPT’s board recommendation, while the antitrust review officially begins. Any new schedule from the companies might shake the shares more than the typical daily biotech swings.
Now, attention shifts to the tender offer launch and initial signals from U.S. antitrust officials. The big question: will the last few cents to hit $58 disappear fast, or will they linger as the deadline approaches?
