Resmetirom (Rezdiffra™) is an oral thyroid hormone receptor-β (THR-β) agonist developed by Madrigal Pharmaceuticals, Inc. to address the underlying causes of metabolic dysfunction associated with steatohepatitis (MASH, previously known as nonalcoholic steatohepatitis, NASH). In March 2024, resmetirom received its first approval in the USA under accelerated approval for the treatment of adults with noncirrhotic NASH and moderate to advanced liver fibrosis (stages F2 to F3). The drug is also under regulatory review in the EU for the treatment of MASH/NASH. This article outlines the key milestones in the development of resmetirom leading to this approval.Resmetirom (Rezdiffra™) is an oral thyroid hormone receptor-β (THR-β) agonist developed by Madrigal Pharmaceuticals, Inc. to address the underlying causes of metabolic dysfunction associated with steatohepatitis (MASH, previously known as nonalcoholic steatohepatitis, NASH). In March 2024, resmetirom received its first approval in the USA under accelerated approval for the treatment of adults with noncirrhotic NASH and moderate to advanced liver fibrosis (stages F2 to F3). The drug is also under regulatory review in the EU for the treatment of MASH/NASH. This article outlines the key milestones in the development of resmetirom leading to this approval.