GSK Acquires Boston Pharmaceuticals’ Liver Drug for $1.2 Billion Plus

GSK has agreed to acquire Boston Pharmaceuticals’ lead asset, efimosfermin alfa, a phase III-ready, potential best-in-class, investigational drug for steatotic liver disease (SLD). Under the agreement, GSK will pay $1.2 billion upfront, with potential for additional success-based milestone payments totaling $800 million.

Efimosfermin is an investigational, once-monthly subcutaneous injection of a long-acting variant of fibroblast growth factor 21 (FGF21) in clinical development for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), including cirrhosis, and future development in alcohol-related liver disease (ALD), both forms of SLD.

SLD represents an area of significant unmet medical need affecting approximately 5% of the global population with limited therapeutic options for patients. SLD, including MASH and ALD, is characterized by the accumulation of fat in the liver (steatosis), with associated inflammation and fibrosis. ALD affects about 26 million patients globally, and together with MASH, is the leading cause of liver transplantation in the US.  Interventions that reduce moderate-to-advanced fibrosis to prevent progression of cirrhosis, liver cancer, hospitalizations and transplant could save the US healthcare system an estimated $40-100 billion over the next two decades.

The acquisition of efimosfermin is highly aligned to GSK’s R&D focus on science related to the immune system and is further evidence of the company’s intent to build on its deep understanding of fibrosis and auto-inflammation to develop precision interventions that stop and reverse disease progression. The addition of efimosfermin further strengthens GSK’s hepatology pipeline of specialty medicines aimed at addressing both viral (chronic hepatitis B) and steatotic (SLD) drivers of fibrotic liver diseases. (Source: Boston Pharmaceuticals Website, 14 May, 2025)