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The European Medicines Agency (EMA) has recommended conditional marketing authorization for Rezdiffra (resmetirom) for adults with noncirrhotic metabolic dysfunction-associated steatohepatitis (MASH) with moderate-to-advanced liver fibrosis. 

MASH was formerly known as nonalcoholic fatty liver disease (NASH). There are currently no authorized treatments for MASH in the EU, making Rezdiffra a potential first.

MASH is a serious liver disease that occurs when fat accumulates in the liver, causing inflammation. Left untreated, it can lead to cirrhosis and cancer. Symptoms may only present in more advanced stages of the condition, at which point they may include discomfort or pain in the upper right abdomen, muscle weakness or loss, and swelling in the abdomen or legs. 

Estimates suggest that up to 5% of people in Europe have MASH and that around 25% have metabolic dysfunction‐associated steatotic liver disease (MASLD), the condition that precedes MASH. MASLD was previously known as nonalcoholic fatty liver disease (NAFLD). 

The active substance of Rezdiffra is resmetirom, which is a partial agonist of the thyroid hormone receptor-beta. It works by promoting lipophagy and hepatic fatty acid beta-oxidation to reduce liver fat, inflammation, and liver fibrosis.

The EMA’s decision comes after interim results from a pivotal, ongoing phase 3 trial including 966 adults with biopsy-confirmed MASH with varying stages of fibrosis. Patients were randomly assigned treatment on a 1:1:1 ratio to receive once-daily resmetirom at 80 mg or 100 mg, or a placebo. 

The primary endpoints were MASH resolution at week 52 with no worsening of fibrosis, and a reduction in fibrosis by at least one stage alongside no worsening of NAFLD activity score. MASH resolution included a reduction in the NAFLD activity score by ≥ 2 points. Scores range from 0 to 8; higher scores indicate more severe disease.

After 12 months, 30% of patients in the 100 mg resmetirom group and 26% of those in the 80 mg group achieved MASH resolution with no worsening fibrosis compared with 10% in the placebo group. 

Meanwhile, 26% of patients in the 100 mg resmetirom group and 24% of patients in the 80 mg group experienced fibrosis improvement by at least one stage with no worsening of NAFLD activity score compared with 14% in the placebo group.

The most frequent side effects were diarrhea, nausea, itching, and pruritus. Diarrhea and nausea were more frequent among those taking resmetirom than those taking the placebo. The rate of serious adverse events was similar across all groups and ranged from 10.9% to 12.7%.

Rezdiffra will be available as 60 mg, 80 mg, and 100 mg film-coated tablets. It should be taken alongside diet and exercise. 

The opinion adopted by the EMA will now go to the European Commission to await a decision on EU-wide marketing authorization. 

In the meantime, the EMA has required Rezdiffra’s applicant to complete both the pivotal and another ongoing trial to provide further data regarding the drug’s efficacy. This conditional approval comes as the EMA perceives that the benefits to patients from immediate availability outweigh the risk inherent in incomplete data. 

Detailed recommendations for using Rezdiffra will be described in the summary of product characteristics, which will be published on the EMA website in all official European Union languages.

Annie Lennon is a medical journalist. Her writing appears on Medscape, WebMD, and Medical News Today, among other outlets.