CAMBRIDGE, Mass. — GSK has announced the acquisition of efimosfermin alfa, a late-stage investigational therapy developed by Boston Pharmaceuticals, in a deal valued at up to $2 billion. The agreement, which includes a $1.2 billion upfront payment and up to $800 million in milestone-based payments, marks a major expansion of GSK’s hepatology pipeline and reflects its growing focus on treatments for steatotic liver disease (SLD), a condition that affects up to 5% of the global population.
Efimosfermin, a once-monthly injectable fibroblast growth factor 21 (FGF21) analog, is being developed to treat metabolic dysfunction-associated steatohepatitis (MASH), a severe form of SLD. It is also being explored for use in alcohol-related liver disease (ALD). Data from a recent phase II trial suggest the therapy may reverse liver fibrosis and halt disease progression in patients with moderate to advanced MASH, with promising results that could position it as a new standard of care. The full trial data were presented at the American Association for the Study of Liver Diseases (AASLD) meeting in November 2024.
Tony Wood, Chief Scientific Officer at GSK, said efimosfermin shows strong potential due to its antifibrotic mechanism, favorable tolerability, and convenient monthly dosing. “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,” he said. “It complements our existing programs, including GSK‘990, and gives us flexibility to pursue both monotherapy and combination treatments for better patient outcomes.”
The acquisition builds on GSK’s strategy of targeting the immune system and fibrosis pathways to treat chronic diseases. SLD, which includes both MASH and ALD, is characterized by fat buildup in the liver, inflammation, and fibrosis, often progressing to cirrhosis or liver cancer. It is the leading cause of liver transplants in the U.S. and places a heavy burden on healthcare systems. Efimosfermin may help reduce that burden by improving liver health and associated cardiometabolic conditions like high triglycerides and poor glycemic control, which are common among MASH patients.
Boston Pharmaceuticals, backed by biotech entrepreneur Ernesto Bertarelli, developed efimosfermin as its lead asset. Company Chair Elias Zerhouni expressed pride in the agreement with GSK, calling the acquisition a validation of years of scientific and strategic work. CEO Sophie Kornowski noted the transaction represents a pivotal moment in the drug’s development, adding that GSK’s global presence and deep expertise in liver disease position it well to bring efimosfermin to patients worldwide.
With the addition of efimosfermin, GSK continues to build a broad portfolio of specialty medicines aimed at both viral and non-viral drivers of fibrotic liver disease, positioning the company at the forefront of emerging therapies for a growing global health challenge.
