GSK’s announcement, on 14 May 2025, that it is to acquire efimosfermin ‒ the lead asset of Boston Pharmaceuticals (Boston) being developed for the treatment and prevention of liver disease ‒ has attracted much media attention, even making BBC news headlines on subsequent days. This decision is based on Phase II data, published in 4Q’24, with GSK agreeing to pay $1.2bn upfront for efimosfermin, and further success-based development milestones of up to $800m. GSK will be responsible also for success-based milestone payments and tiered royalties that become due to Novartis.
Given the high prevalence of obesity in the world and increasing alcohol-related issues, there has been an enormous rise in the number of patients with liver disease. “Liver disease” is a composite term describing >100 conditions that may be inherited, degenerative (e.g. cancers), or caused by lifestyle factors and infectious agents. Cirrhosis is the end-stage result of liver fibrosis, which occurs when scar tissue accumulates from chronic liver damage. Patients with established cirrhosis are at risk of hepatocellular carcinoma (HCC): up to 90% of HCC patients have cirrhosis.
Efimosfermin is a once-monthly, subcutaneously injected, fibroblast growth factor 21 (FGF21) analogue in clinical development for the treatment of metabolic dysfunction-associated steatohepatitis (MASH), including cirrhosis, and future development in alcohol-related liver disease (ALD). In addition to targeting the main forms of liver disease in its various stages with efimosfermin, GSK is aiming to maximise this putative drug’s potential by combining its direct anti-fibrotic mechanism of action with its own drug, GSK’990, a siRNA therapeutic in development, for other subsets of patients with liver disease.
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