GSK plc has announced that its investigational liver therapy, efimosfermin, has received both Breakthrough Therapy Designation from the US Food and Drug Administration and Priority Medicines (PRIME) Designation from the European Medicines Agency for the treatment of Metabolic dysfunction-Associated Steatohepatitis (MASH).

The dual recognition is expected to accelerate the development and regulatory review of efimosfermin, particularly as MASH remains a serious liver condition with limited treatment options. The FDA’s Breakthrough Therapy Designation is granted to drugs that demonstrate substantial improvement over existing therapies for serious diseases, while the EMA’s PRIME scheme provides enhanced scientific and regulatory support for medicines addressing unmet medical needs.

According to Kaivan Khavandi, Senior Vice President and R&D Head for Respiratory, Immunology and Inflammation at GSK, MASH affects millions globally and is a leading cause of liver transplants in both the United States and Europe. He emphasised that efimosfermin has the potential to transform the current standard of care by directly targeting liver fibrosis, especially in patients with advanced stages of the disease where treatment options are scarce or non-existent.

The regulatory designations are backed by clinical data from Phase II trials involving patients with moderate to advanced fibrosis (F2/F3) and cirrhosis (F4). Results at 48 weeks showed that once-monthly efimosfermin led to significant improvements in fibrosis and resolution of MASH compared to placebo. The therapy also demonstrated a favourable safety profile, with mostly mild and transient side effects such as nausea, vomiting and diarrhoea.

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

MASH is a chronic and progressive liver disease affecting up to 5 percent of the global population. It is characterised by fat accumulation, inflammation and fibrosis in the liver, which can lead to cirrhosis, liver failure or cancer. Despite its growing prevalence, there are currently limited treatment options for patients with moderate to advanced fibrosis, and none approved for cirrhotic stages.

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

The development of efimosfermin forms part of GSK’s broader strategy to expand its pipeline in liver diseases by leveraging its expertise in inflammation and immunology. The company continues to advance research into treatments for chronic hepatitis B, MASH and alcohol-associated liver disease, aiming to address significant unmet needs in hepatology.