GSK Acquires Promising Liver Disease Drug in USD 2 Billion Deal
The acquisition of efimosfermin alfa, a Phase III-ready FGF21 analog targeting steatotic liver diseases, will expand GSK’s hepatology pipeline and establish a best-in-class therapy for MASH and ALD.
GSK has entered into an agreement to acquire Boston Pharmaceuticals’ lead asset, efimosfermin alfa — a Phase III-ready, investigational specialty medicine to treat and prevent progression of steatotic liver disease (SLD). As part of the deal, GSK will make an upfront payment of USD 1.2 billion, with the potential for up to USD 800 million in additional milestone payments based on future success (1).
Efimosfermin is a once-monthly therapy based on a fibroblast growth factor 21 (FGF21) analog and is currently in clinical development to treat a form of SLD — metabolic dysfunction-associated steatohepatitis (MASH) — with plans to expand into alcohol-related liver disease (ALD). SLD — including MASH and ALD — is characterized by the accumulation of fat in the liver (steatosis) with associated inflammation and fibrosis, which is estimated to affect approximately 5% of the global population. ALD alone affects about 26 million patients globally, and together with MASH, is the leading cause of liver transplant in the U.S. and poses a significant burden and cost on healthcare utilization (2,3).
With limited therapeutic options currently available, GSK aims to combine their expertise in human genetics and disease profiling with efimosfermin’s targeted antifibrotic action to progress treatment of advanced stages of SLD. The company has also stated potential plans to combine efimosfermin with their own small interfering RNA (siRNA) therapy, GSK’990, which is currently being developed for other SLD patient groups.
“The FGF21 class has shown some of the most exciting data in MASH including first-in-disease evidence of cirrhosis reversal, and efimosfermin has the potential to define a new standard-of-care with its monthly dosing and tolerability profile,” said Tony Wood, Chief Scientific Officer at GSK, in a company press release about the acquisition (1). “Efimosfermin will significantly expand our hepatology pipeline and provide us the opportunity to develop a new potential best-in-class medicine with first launch expected in 2029. It complements GSK’990, also in development for ALD and MASH, offering GSK options to develop both monotherapy and potential combinations to improve patient outcomes.”
While lifestyle interventions through diet and exercise remain the cornerstone of early-stage management of SLD-related disease (4), adherence and efficacy are often limited — especially in advanced cases involving fibrosis or cirrhosis. The field of hepatology has seen increased investment in targeted therapies, particularly agents aimed at modulating metabolic pathways, inflammation, and fibrogenesis. FGF21 analogs have emerged as one of the most promising classes in clinical trials, showing their ability to not only halt progression but reverse liver damage through coordinated actions on the central nervous system and liver (5).
To date, no therapy has received full global regulatory approval specifically for MASH with cirrhosis, but GSK will hope that efimosfermin, alone or in combination, will continue to demonstrate positive results in treating the complex, multifactorial nature of the disease.
References
GSK. GSK to Acquire Efimosfermin, a Phase III-Ready Potential Best-in-Class Specialty Medicine to Treat and Prevent Progression of Steatotic Liver Disease (SLD). Press Release, May 14, 2025.
GBD 2017 Cirrhosis Collaborators. Global Burden of Disease Study 2017. Lancet Gastroenterol. Hepatol. 2020, 5(3), 245–266.
Younossi, Z.M.; Stepanova, M.; Al Shabeeb, R.; et al. The Dominance of Metabolic Dysfunction-Associated Steatotic Liver Disease and Alcohol-Associated Liver Disease. Hepatol. Commun. 2023, 8(1), e0352.
Verywell Health. What's New in MASH Treatment?. Article, April 10, 2025.
Rose, J.P.; Morgan, D.A.; Sullivan, A.I.; et al. FGF21 Reverses MASH Through Coordinated Actions on the CNS and Liver. Cell Metab., Available Online May 13, 2025.