Consumer's Guide to THR-Beta Agonists for MASH

Although resmetirom is the only FDA-approved THR-beta agonist currently available, “There is one ongoing phase 2b clinical trial for a different THR-beta agonist and at least a few others that are still in preclinical stages,” says Vincent Chen, MD, an assistant professor of internal medicine at the University of Michigan Medical School in Brighton. And different drugs may also be coming down the pike to help treat MASH.

Resmetirom is available now, but its clinical trial is still ongoing, says Na Li, MD, PhD, a hepatologist at The Ohio State University Wexner Medical Center in Columbus. This means the drug has to continue to be evaluated for safety and efficacy before it receives final approval.

THR-beta agonists mimic the “thyroid hormone in the liver, while having little effect on thyroid hormone levels in the rest of the body,” says Dr. Chen.

Findings from a study published in January 2025 showed that, by activating the THR-beta protein, this drug can help reduce liver fat accumulation, fibrosis (a buildup of scar tissue), and inflammation, primarily through its ability to regulate fat metabolism and improve liver function. This can slow the progression of MASH and improve overall liver health.

“It’s a very attractive mechanism,” Dr. Gunn says. “It also has some ability to lower LDL [“bad”] cholesterol, which is appealing, because people living with MASH often have underlying dyslipidemia,” or unhealthy levels of fat in the blood.

Cirrhosis is a severe form of liver scarring that occurs when healthy liver tissue is replaced by scar tissue. MASH can lead to cirrhosis, because the fat accumulation and inflammation in the liver can cause permanent scarring (fibrosis). But resmetirom can only reduce fibrosis in the earlier stages of liver disease and slow down its progress. It has not been shown to reverse existing cirrhosis. “People with cirrhosis should not take resmetirom, because we don’t know if it can help them,” says Chen.

That said, “There is an ongoing clinical trial looking at resmetirom in people with cirrhosis, so we should find out more in a few years,” he says.

“Common side effects include nausea, diarrhea, and elevated liver enzymes,” says Dr. Li. These effects usually go away as your body adjusts to the medication. In rare cases, gallbladder problems can occur.

Your doctor will monitor you for potential side effects and check your liver function to make sure the treatment is working well for you. Testing with bloodwork should occur every three to six months.

Resmetirom is a pill taken by mouth once a day, with or without food. It should be taken around the same time each day.

The exact dosing varies from person to person, so be sure to follow your doctor's instructions, according to MedlinePlus, especially to avoid any potential interactions with other medications you’re taking.

MASH often occurs in people who have other health conditions, such as:

• Diabetes
• High blood pressure
• High cholesterol
• Obesity
  

Exercising regularly and eating a healthy diet can help reduce liver fat and decrease inflammation, according to research — and help improve other health conditions you may have, too.

You most likely won’t have to avoid any other medications if you’re taking resmetirom, Li says. But your doctor may want to monitor you for possible drug interactions if you’re taking medications such as statins or clopidogrel.

Be sure your doctor has a full list of the medications and supplements you take, including ones that are over the counter, so they can watch for any possible issues.