Merck: efinopegdutide resolved MASH in up to 63% of patients in a Phase 2b trial at 52 weeks

Merck (MRK) reported positive Phase 2b results for efinopegdutide, an investigational treatment for metabolic dysfunction-associated steatohepatitis (MASH), on November 10, 2026, according to rttnews.com rttnews.comrttnews.comrttnews.comOpen source ↗. The study enrolled 386 adults with biopsy-confirmed MASH and stage F2 or F3 liver fibrosis. The trial met its primary endpoint after 52 weeks of treatment.

MASH is a progressive liver disease characterized by fat buildup, inflammation and scarring in the liver. It can lead to cirrhosis, liver failure and other serious complications, and treatment options remain limited, particularly for patients with more advanced fibrosis.

Trial design and efficacy results

Participants received one of three once-weekly doses of efinopegdutide, placebo, or an active reference treatment, semaglutide 2.4 mg. In total, 92% of participants completed the study. The primary endpoint was MASH resolution without worsening of fibrosis. It was reached by 56%, 63% and 61% of patients receiving 4 mg, 7 mg and 10 mg, respectively, versus 13% on placebo.

A key secondary endpoint was an improvement in fibrosis of at least one stage without worsening of liver inflammation. It was achieved by 43%, 52% and 34% of patients across the three dose groups, compared with 21% on placebo rttnews.comrttnews.comrttnews.comOpen source ↗. The results were presented at The Liver Meeting and published simultaneously in The Lancet.

Safety and mechanism

The safety profile was generally consistent with that of GLP-1-based therapies. The most common side effects were gastrointestinal: nausea, diarrhea and vomiting. Discontinuation due to adverse events ranged from 3% to 11% across the efinopegdutide groups, compared with 1% for both placebo and semaglutide.

Efinopegdutide is a once-weekly injectable dual GLP-1/glucagon receptor co-agonist. It is designed to combine appetite regulation and metabolic benefits with direct effects on liver fat metabolism. The drug has received FDA Fast Track Designation for MASH, and Merck continues its development for patients with MASH and liver fibrosis.