Pharma BD Deal Intelligence
GSK acquired efimosfermin alfa from Boston Pharmaceuticals for $1.2B upfront and up to $800M in success-based milestones (total up to $2B), with success-based milestones and tiered royalties also payable to Novartis Pharma AG; the acquisition completed on 7 July 2025. Efimosfermin is a once-monthly subcutaneous FGF21 analog for metabolic dysfunction-associated steatohepatitis (MASH) including compensated cirrhosis, with future development planned in alcohol-related liver disease. Since the deal closed, the Phase 3 program has begun: the pivotal ZENITH-1 study (NCT07221227) in biopsy-confirmed F2/F3 MASH started 24 October 2025 and is recruiting (~1,200 participants; primary completion estimated March 2028), with companion F2/F3 and cirrhotic (F4) studies following. In April 2026 GSK reported that efimosfermin received US FDA Breakthrough Therapy designation and EMA Priority Medicines (PRIME) designation in MASH. GSK continues to guide to a potential first launch in 2029.