GSK Acquires Phase III-Ready Liver Drug Efimosfermin for Up to $2B to Enter MASH Arena

GSK announced a deal worth up to $2 billion to acquire efimosfermin alfa, a Phase III-ready liver drug from Boston Pharmaceuticals234.

The deal includes a $1.2 billion upfront payment to Boston Pharmaceuticals and up to $800 million in milestone-based payments25.

Efimosfermin alfa is an investigational analog of FGF21, designed to treat steatotic liver disease (SLD), including metabolic dysfunction-associated steatohepatitis (MASH) and alcohol-related liver disease123.

GSK aims to develop efimosfermin as a potential new standard of care for SLD, a condition that affects up to 5% of the global population and currently has limited therapeutic options2.

The acquisition positions GSK in direct competition with recent MASH therapies, such as Madrigal Pharmaceuticals' FDA-approved Rezdiffra1.

The new drug could benefit healthcare systems by preventing disease progression, which may save an estimated $40-100 billion for the US over the next 20 years2.

Sources:

1. https://medcitynews.com/2025/05/gsk-fatty-liver-disease-mash-boston-pharmaceuticals-efimosfermin-fgf21/

2. https://medicalxpress.com/news/2025-05-gsk-buys-liver-disease-drug.html

3. https://www.biospace.com/deals/gsk-buys-phase-iii-ready-liver-drug-in-potential-2b-deal-to-play-in-mash-arena

4. https://www.clinicaltrialsarena.com/news/gsk-to-spend-2bn-on-phase-iii-liver-disease-drug-acquisition/

5. https://www.biopharmadive.com/news/gsk-boston-pharmaceuticals-liver-drug/748099/