What changed, and when

GSK announced a definitive agreement on 20 Jan 2026 to acquire RAPT Therapeutics for $58 per share, valuing the deal at $2.2 billion, with closing targeted in Q1 2026 via tender offer and second-step merger (GSK press release). Independent reports confirm terms and strategic focus on ozureprubart, a long-acting anti-IgE antibody for food allergy (Reuters, Financial Times, Fierce Biotech).

60-second thesis frame

The deal gives GSK a potentially best-in-class long-acting anti-IgE, ozureprubart, in phase 2b for prophylactic protection against food allergens, with a proposed dosing interval of every 12 weeks, versus omalizumab’s every 2–4 weeks, in a category newly validated by FDA’s 2024 approval of Xolair for IgE-mediated food allergy (GSK press release, FDA press announcement on Xolair food allergy approval, 16 Feb 2024, Xolair FDA label, dosing q2–4w). The near-term value hinge is execution on tender offer and HSR timing, then delivery of clean phase 2b “prestIgE” data and a clear phase 3 path in adult and paediatric populations, while navigating payer positioning against an entrenched omalizumab standard. If ozureprubart shows robust efficacy and safety with materially less frequent dosing, adoption and adherence could be meaningfully better in predominantly paediatric care settings (ClinicalTrials.gov NCT07220811, RAPT trial initiation PR, Oct 2025).

The seven diligence questions

Clinical

• Does prestIgE demonstrate clinically meaningful protection across multiple allergens, with effect sizes competitive versus omalizumab real-world outcomes, and with durability supporting q12w dosing (ClinicalTrials.gov NCT07220811, Xolair FDA label)?
• What is the paediatric safety profile, including anaphylaxis risk and injection-site reactions, and does immunogenicity impact long-interval dosing (Xolair FDA label)?

Payer or Access

• Will US payers apply prior authorization or step-edit to omalizumab first, given existing coverage frameworks and dosing familiarity (FDA press announcement)?
• Are appropriate J-codes or HCPCS pathways anticipated at launch, and what site-of-care strategies will minimize administration friction in paediatric clinics (FDA press announcement)?

Ops or Adoption

• Can GSK scale supply and specialty-pharmacy distribution aligned to seasonal allergy care patterns, and support caregiver training for less frequent injections (GSK press release)?

Competitive

• How does ozureprubart’s efficacy, safety and dosing convenience compare to omalizumab in food allergy, and could head-to-head or indirect comparisons be necessary to drive switching (Xolair FDA label, FDA press announcement)?

Team or Cap table

• Are success-based milestones to Shanghai Jeyou and any retained economics cleanly structured for global rollout outside Greater China, and are integration plans resourced for paediatric allergy commercial execution (GSK press release)?

Red flags

• Phase 2b fails to show consistent protection across multiple allergens or reveals safety signals that negate the long-interval dosing advantage (ClinicalTrials.gov NCT07220811).
• US payers hard-gate access behind omalizumab step therapy, slowing uptake despite convenience claims (FDA press announcement).
• Regulatory or antitrust timing slips past Q1 2026, prolonging uncertainty around program ownership and trial execution (GSK press release).

Next catalyst

Tender offer launch within 10 business days of signing and HSR waiting period expiration, with closing targeted in Q1 2026, plus study-ops updates as prestIgE enrollment progresses toward 2027 readout (GSK press release, Reuters).

FAQ

• What exactly changed by GSK’s agreement to acquire RAPT Therapeutics, and why does it matter for food allergy?
  GSK agreed to buy RAPT for $58 per share, about $2.2 billion, to acquire ozureprubart, a long-acting anti-IgE antibody in development for prophylactic protection against food allergens, potentially enabling dosing every 12 weeks (GSK press release, Reuters, Fierce Biotech).
• What is the regulatory path after GSK enters in an agreement to acquire RAPT Therapeutics and what are the next formal steps in the US, UK, and EU?
  In the US, GSK will commence a tender offer within 10 business days, then close subject to HSR expiration, followed by a second-step merger; clinical path targets phase 3 in adult and paediatric populations after phase 2b readout expected in 2027 (GSK press release, Financial Times).
• Which endpoints in prestIgE drove the result cited in the announcement by GSK regarding RAPT Therapeutics and how meaningful is the effect size?
  PrestIgE is a randomized, double-blind, placebo-controlled phase 2b monotherapy study evaluating safety and efficacy with q8–12 week dosing; effect sizes are unknown pre-readout, which RAPT and GSK guide for 2027 (ClinicalTrials.gov NCT07220811, RAPT trial initiation PR).
• What safety issues matter post-GSK-RAPT agreement and do they change real-world use?
  Key considerations include anaphylaxis risk, hypersensitivity, and injection-site reactions, which are class-relevant for anti-IgE therapy, and will be scrutinized for a q12w regimen in paediatric settings (Xolair FDA label).
• Does this deal include RAPT’s oncology asset tivumecirnon?
  Technically yes, GSK acquires all outstanding shares, but the deal value and strategic rationale are explicitly centered on ozureprubart and the immunology pipeline, with tivumecirnon (CCR4) receiving minimal mention in the acquisition thesis (GSK press release, Fierce Biotech).

Publisher / Disclosure

Publisher: LucidQuest Ventures Ltd. Produced: 20 Jan 2026, 10:00 London. Purpose: general and impersonal information. Not investment research or advice, no offer or solicitation, no suitability assessment. UK: directed at investment professionals under Article 19(5) and certain high-net-worth entities under Article 49(2)(a)–(d) of the Financial Promotion Order 2005. Others should not act on this. Sources and accuracy: public sources believed reliable, provided “as is,” may change without notice. No duty to update. Past performance is not reliable. Forward-looking statements carry risks. Methodology: questions-first framework using public sources. No conflicts. Authors do not hold positions unless stated. © 2026 LucidQuest Ventures Ltd.

Entities / Keywords

GSK; RAPT Therapeutics; ozureprubart; RPT904; IgE; IgE-mediated food allergy; prophylaxis; prestIgE; NCT07220811; omalizumab; Xolair; FDA; EMA; MHRA; CHMP; HSR; tender offer; Evercore; A&O Shearman; J.P. Morgan; Cooley LLP; Shanghai Jeyou Pharmaceutical; Greater China; paediatric allergy; peanut allergy; milk allergy; egg allergy; tree nut allergy; specialty pharmacy; HCPCS; q12w dosing; phase 2b; phase 3; respiratory, immunology and inflammation; UK; US.