GSK's Efimosfermin Secures USFDA Breakthrough, EMA PRIME Tags for MASH

The FDA’s Breakthrough Therapy designation aims to accelerate the development and review of drugs for serious conditions where early clinical evidence suggests substantial improvement over existing therapies. Similarly, the EMA’s PRIME designation offers enhanced scientific and regulatory support to medicines addressing significant unmet medical needs.

Commenting on the development, Kaivan Khavandi, SVP, R&D Head Respiratory, Immunology & Inflammation (RI&I), and Head of Translational & Development Sciences at GlaxoSmithKline, said, “MASH affects millions of people worldwide and is one of the leading causes of liver transplant in the US and Europe, but treatment options are limited for most and non-existent for those with the most advanced form of disease. These designations recognise efimosfermin’s potential and reflect GSK’s accelerating momentum in liver health. We believe efimosfermin has the potential to significantly advance the standard of care by directly targeting liver fibrosis.”

The dual regulatory recognitions are supported by Phase II clinical data in patients with moderate-to-advanced (F2/F3) and cirrhotic (F4) fibrosis. At 48 weeks, patients treated with once-monthly efimosfermin demonstrated improvement in liver fibrosis and resolution of MASH compared to placebo. The therapy also showed a favourable safety profile, with mostly mild and transient adverse events such as nausea, vomiting, and diarrhoea.

Efimosfermin is currently being evaluated in Phase III studies—ZENITH-1 and ZENITH-2—for patients with F2/F3 fibrosis. Additional Phase III trials targeting patients with cirrhotic (F4) MASH are expected to commence later this year.

MASH is a chronic and progressive liver disease affecting up to 5% of the global population and is a leading cause of liver transplantation in the US and Europe. Disease progression is driven by fibrosis, which increases the risk of cirrhosis, liver failure, and hepatocellular carcinoma. Currently, treatment options remain limited, particularly for patients with advanced fibrosis, and no therapies are approved for cirrhotic (F4) MASH.

Efimosfermin is a once-monthly subcutaneous injection and a long-acting variant of fibroblast growth factor 21 (FGF21), designed to regulate metabolic pathways, reduce liver fat, alleviate inflammation, and reverse fibrosis. The therapy remains investigational and is not approved for use anywhere globally.

GlaxoSmithKline continues to expand its hepatology pipeline, leveraging its expertise in inflammation and immune science to develop next-generation therapies for chronic liver diseases, including MASH, chronic hepatitis B, and alcohol-associated liver disease.