Resmetirom, sold under the brand name Rezdiffra, is a medication used for the treatment of noncirrhotic metabolic dysfunction associated steatohepatitis (MASH) (formerly known as nonalcoholic steatohepatitis NASH). It is a thyroid hormone receptor beta (NR1A2) agonist.

The most common side effects include diarrhea and nausea.

Resmetirom was approved for medical use in the United States in March 2024, and in the European Union in August 2025. The US Food and Drug Administration considers it to be a first-in-class medication.

Resmetirom is indicated, in conjunction with diet and exercise, for the treatment of adults with noncirrhotic nonalcoholic steatohepatitis with moderate to advanced liver fibrosis (consistent with stages F2 to F3 fibrosis).

In a phase III clinical trial, it was found to be effective for resolving noncirrhotic nonalcoholic steatohepatitis and improving liver fibrosis.

The US Food and Drug Administration (FDA) evaluated the safety and efficacy of resmetirom based on an analysis of a surrogate endpoint at month twelve in a 54-month, randomized, double-blind placebo-controlled trial. The surrogate endpoint measured the extent of liver inflammation and scarring. The FDA requires the sponsor to conduct a postapproval study to verify and describe the clinical benefit of resmetirom, which will be done through completing the same 54-month study. In the trial, 888 participants were randomly assigned to receive one of the following: placebo (294 participants); 80 milligrams of resmetirom (298 participants); or 100 milligrams of resmetirom (296 participants); once daily, in addition to standard care for noncirrhotic nonalcoholic steatohepatitis, which includes counseling for healthy diet and exercise.

The FDA granted the application for resmetirom accelerated approval, along with breakthrough therapy, fast track, and priority review designations. The FDA granted the approval of Rezdiffra to Madrigal Pharmaceuticals.

Resmetirom was approved for medical use in the United States in March 2024.