Resmetirom is now FDA-approved for non-cirrhotic non-alcoholic steatohepatitis (NASH) with moderate to advanced liver scarring (fibrosis) along with a healthy diet and exercise, as per the news release of the FDA in March 2024.

NASH develops as a consequence of the advancement of nonalcoholic fatty liver disease (NAFLD), where prolonged liver inflammation may eventually result in liver scarring and impaired liver function. This therapy promotes partial activation of thyroid hormone receptors to cut down excess fat accumulation in the liver.

The effectiveness and safety of Resmetirom were assessed by analyzing a surrogate endpoint after 12 months in a 54-month-long, randomized, controlled trial. This endpoint gauged liver inflammation and scarring. A post-approval study is mandated to elaborate on Resmetirom’s clinical benefits, with the same 54-month study ongoing. Patients were required to have liver biopsies indicating NASH-related inflammation with moderate or advanced scarring to participate in the trial. In the study, 888 participants were randomly assigned to receive either a placebo (294 participants), Resmetirom 80 mg (298 participants), or Resmetirom 100 mg (296 participants) once a day, alongside standard NASH care, which includes dietary and exercise counselling.

As found, more people treated with Resmetirom showed improvement in NASH or liver scarring compared to those on placebo. Approximately 26% to 27% of those on Resmetirom 80 mg and 24% to 36% of those on Resmetirom 100 mg experienced NASH resolution without worsening scarring, versus 9% to 13% on placebo. Improvement in scarring was witnessed in 23% of people with Resmetirom 80 mg and 24% to 28% of people with Resmetirom 100 mg without worsening NASH. Achieving such improvements in just a year is noteworthy, given NASH's typically slow progression, often taking years or decades to worsen. 

In terms of side effects, diarrhoea and nausea were most frequently observed with Resmetirom. It should be avoided in case of decompensated cirrhosis and discontinued if signs of deteriorating liver function appear. In terms of drug-drug interactions, the use of Resmetirom along with certain other drugs, such as statins for lowering cholesterol, may result in adverse interactions. 

Resmetirom received FDA approval through the accelerated pathway, which allows early approval for drugs addressing serious illnesses, based on surrogate clinical benefits. This clinical study of Resmetirom will still examine its long-term clinical benefits (after 54 months).