Resmetirom

Resmetirom is a substrate and mild inhibitor of CYP2C8. In a clinical study in healthy subjects, co-administration of a single oral dose of pioglitazone (15 mg), a moderately sensitive CYP2C8 substrate, with resmetirom (100 mg/day) resulted in a 1.5-fold increase in the AUC of pioglitazone, with no change in C_max.

Although no dose adjustment is required, clinical monitoring is recommended when resmetirom is used with certain CYP2C8 substrates for which small increases in exposure may lead to serious or dose-related adverse reactions.

Concomitant use of resmetirom with strong CYP2C8 inhibitors (e.g., gemfibrozil) is not recommended. If resmetirom is used concomitantly with a moderate CYP2C8 inhibitor (e.g., clopidogrel, deferasirox, teriflunomide), the dose of resmetirom should be reduced from 100 mg to 80 mg for patients weighing ≥100 kg and from 80 mg to 60 mg for patients weighing <100 kg.

Clopidogrel increased resmetirom exposure (1.3-fold in C_max and 1.7-fold in AUC) in healthy adult subjects.

No dose adjustment is required in patients with mild hepatic impairment (Child-Pugh A). Safety and efficacy have not been demonstrated in Child-Pugh A cirrhosis.

Increased exposure (C_max and AUC) of resmetirom has been observed in patients with moderate or severe hepatic impairment. Resmetirom should not be used in patients with moderate or severe (Child-Pugh B or C) hepatic impairment.

The effect of resmetirom on the pharmacokinetics of statins (i.e., simvastatin, rosuvastatin, pravastatin and atorvastatin) was evaluated in studies in healthy subjects:

• Simvastatin: AUC increased by 1.7-fold and C_max by 1.4-fold following a single dose of simvastatin 20 mg with resmetirom (100 mg/day).
• Rosuvastatin: AUC increased by 1.4-fold and C_max by 1.8-fold following a single dose of rosuvastatin 20 mg with resmetirom (100 mg/day).
• Pravastatin: AUC increased by 1.4-fold and C_max by 1.3-fold following a single dose of pravastatin 40 mg with resmetirom (100 mg/day).
• Atorvastatin: AUC increased by 1.4-fold with no change in C_max following a single dose of atorvastatin 20 mg with resmetirom (100 mg/day).

The dose of rosuvastatin and simvastatin should be limited to a daily dose of 20 mg and the dose of pravastatin and atorvastatin should be limited to a daily dose of 40 mg.

Resmetirom has not been studied in patients with other underlying liver diseases. Resmetirom should be used with caution in MASH patients with other underlying liver diseases such as autoimmune liver diseases or active viral hepatitis. Resmetirom should be used with caution in patients with alcohol-related liver disease.

There are no data from the use of resmetirom in pregnant women. Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity.

As a precautionary measure, it is preferable to avoid the use of resmetirom during pregnancy.

It is unknown whether resmetirom and/or its metabolites are excreted in human milk. A risk to newborns/infants cannot be excluded.

A decision must be made whether to discontinue breast-feeding or to abstain from resmetirom therapy, taking into account the benefit of breast-feeding for the child and the benefit of therapy for the woman.

Fertility

No fertility data are available in humans. Animal studies do not indicate any direct or indirect effects on fertility.

Resmetirom has no or negligible influence on the ability to drive and use machines.

Summary of the safety profile

The most frequently reported adverse reactions are diarrhoea, nausea, and pruritus.

Diarrhoea typically occurred at treatment initiation, was mild to moderate and self-limiting, resolving on average in 2 to 3 weeks. The median time to complete resolution of diarrhoea was 3 to 4 weeks. Nausea occurred at treatment initiation and was mild to moderate, occurring more commonly in female patients.

Other rare events included cholecystitis and urticaria.

The most common reason for discontinuation in all age groups was withdrawal by subject.

Tabulated list of adverse reactions

Unless otherwise stated, the frequencies of adverse reactions in the table below are based on all-cause adverse event frequencies identified in patients randomised to the double-blind treatment arms of the Phase 3 clinical studies (MAESTRO-NASH and MAESTRO-NAFLD-1).

Adverse reactions are listed by MedDRA system organ class and frequency: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1 000 to <1/100); rare (≥1/10 000 to <1/1 000); very rare (<1/10 000); not known (cannot be estimated from the available data). Within each frequency grouping, adverse reactions are presented in the order of decreasing seriousness.

List of adverse reactions in MAESTRO-NASH and MAESTRO-NAFLD-1:

¹ The term "cholecystitis" includes Preferred Terms of bile duct stone, biliary colic, biliary dilatation, cholecystitis, cholecystitis acute, cholecystitis chronic and cholangitis.
² A higher incidence of cholecystitis and obstructive pancreatitis (gallstone) was observed in the treatment arms compared to placebo. However, the Exposure Adjusted Incidence Rates (EAIRs) for these events were less than 1 per 100 patient years (PY) for all treatment arms.

Description of selected adverse reactions

Liver enzyme elevations

Mild increases in mean alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were observed in the first 4 weeks after initiating treatment with resmetirom. These elevations were more common in patients on concomitant statin therapy. In both resmetirom dose arms, the mean elevation in ALT and AST values was less than 1.5 times baseline at 4 weeks after treatment initiation. These values returned to baseline around 8 weeks after initiating treatment.

Thyroid function tests

A decrease in levels of prohormone free T4 (FT4) of mean 2%, 13%, and 17% was seen at 12 months in patients treated with placebo, resmetirom 80 mg once daily, and resmetirom 100 mg once daily, respectively, with minimal changes in active hormone T3 or in TSH. There were no clinical findings associated with FT4 decreases.

Other special populations

Elderly

Of the 1794 patients with MASH in clinical studies of resmetirom who received the recommended dose (80 mg or 100 mg), 440 (25%) were 65 years of age or older and 54 (3%) were 75 years of age or older. Discontinuation rates among older patients ≥65 years of age in MAESTRO-NASH were higher at 100 mg than 80 mg.