Semaglutide (Wegovy) for MASH: What the ESSENCE Trial Showed

TL;DR: In August 2025 the FDA approved semaglutide, the drug in Wegovy and Ozempic, to treat MASH, the inflammatory and scarring form of fatty liver disease, in adults with moderate-to-advanced fibrosis. It is the first GLP-1 drug cleared for the liver, joining resmetirom as the second approved MASH treatment. In the pivotal ESSENCE trial, semaglutide resolved the steatohepatitis in about 63% of people versus 34% on placebo, a strong result, and improved liver scarring in about 37% versus 22%, a genuine but more modest gain. Unlike resmetirom, which acts directly on liver cells and is weight-neutral, semaglutide works mostly by driving weight loss and better blood sugar, and it adds the bonus of substantial weight loss and proven cardiovascular benefit. Its approval rests on liver biopsy improvement; whether it prevents cirrhosis, liver failure, and death is still being tested.

What is semaglutide's role in fatty liver disease?

Semaglutide is the GLP-1 drug behind Ozempic and Wegovy, known for lowering blood sugar and driving major weight loss. Its newest use is the liver. In August 2025, based on the ESSENCE trial, the FDA approved Wegovy to treat MASH, short for metabolic dysfunction-associated steatohepatitis, in adults with moderate-to-advanced fibrosis. MASH is the stage of fatty liver where fat has driven inflammation and scarring, and it can progress to cirrhosis if left unchecked. Our fatty liver guide covers the disease; this piece is about the drug.

This approval is a milestone: semaglutide is the first GLP-1 drug cleared for the liver, and only the second drug of any kind approved for MASH, after resmetirom in 2024. For the many people whose fatty liver is bound up with obesity and diabetes, a drug that treats all three at once is a meaningful addition.

What did the ESSENCE trial show?

ESSENCE was a phase 3 trial of nearly 1,200 people with biopsy-confirmed MASH and moderate-to-advanced fibrosis, who took weekly semaglutide at the 2.4 mg Wegovy dose or a placebo for 72 weeks.¹ Like other MASH trials, it measured two things by liver biopsy: whether the steatohepatitis resolved, and whether the scarring improved.

Both goals were met, but not equally. The inflammation result was strong: the steatohepatitis resolved in about 63% of people on semaglutide, compared with 34% on placebo. The scarring result was more measured: liver fibrosis improved by at least one stage in about 37%, versus 22% on placebo. That fibrosis gain is genuine and matters, but it is smaller than the inflammation benefit, roughly half the size, so the fair read is that semaglutide is better at calming the liver's inflammation than at reversing its scarring, at least over these 72 weeks. Along the way, people lost about 10% of their body weight, much more than the placebo group.

How is it different from resmetirom?

The two approved MASH drugs treat the same disease by opposite routes, which is what makes them interesting together.

Resmetirom works directly in the liver, switching on a thyroid receptor that tells liver cells to burn fat, and it does not cause weight loss. Semaglutide barely touches the liver directly; in fact, liver cells have almost no GLP-1 receptors. Instead it works from the outside in, chiefly by driving weight loss and improving insulin sensitivity, which takes the metabolic pressure off the liver and lets it heal. Interestingly, the liver benefit in ESSENCE was somewhat larger than weight loss alone would predict, hinting that semaglutide has some liver effects beyond the pounds lost, though the weight and metabolic improvement do most of the work.

That difference gives semaglutide two advantages resmetirom lacks: it produces significant weight loss, and it has proven cardiovascular benefit. In a separate large trial, semaglutide lowered heart attacks and strokes in people with obesity and heart disease.² Since people with MASH are usually carrying excess weight and are at high cardiovascular risk, those bonuses are worth a great deal. Because the two drugs work so differently, there is growing interest in whether they might be used together, but that is a hypothesis: no trial has tested the combination, and there is no head-to-head comparison of the two.

The limits worth understanding

Two cautions keep the enthusiasm grounded, and they mirror the ones for resmetirom.

First, the approval rests on a surrogate. ESSENCE measured the liver on biopsy at 72 weeks, the inflammation and the scarring. It did not, and could not in that time, prove that these improvements translate into fewer people developing cirrhosis, needing a transplant, or dying of liver disease. Those hard outcomes are being measured in a longer phase of the trial that follows patients for about 4.5 years. So the fair statement is that semaglutide is proven to improve the liver's biology and appearance, with its effect on long-term liver outcomes still being confirmed.

Second, the benefit likely depends on staying on the drug. Semaglutide's effects on weight and metabolism tend to regress when it is stopped, and since its liver benefit flows largely from those effects, the improvement may not hold if the drug is discontinued. That makes it a long-term treatment for most people rather than a short course, and one more reason to build the plan around durable habits alongside the medication.

One more point on scope: the approval is specific, for MASH with moderate-to-advanced fibrosis, stages F2 and F3, in people without cirrhosis. It was not studied in mild fatty liver without scarring, and people who already have cirrhosis were excluded, so it is not for either of those groups.

Side effects and who it is for

The side effects are the familiar GLP-1 effects, centered on the gut: nausea, vomiting, and diarrhea, usually mildest when the dose is raised slowly. Like the other drugs in its class, it carries a boxed warning about a rare thyroid tumor seen in rodents, so it is avoided in people with a personal or family history of medullary thyroid cancer or the MEN2 syndrome, along with cautions about pancreatitis and gallbladder problems.

It suits a person with MASH and F2-to-F3 fibrosis, particularly one who also carries excess weight, has type 2 diabetes, or is at high cardiovascular risk, since it addresses all of those at once. For a leaner person with MASH but little excess weight, resmetirom's liver-direct approach may fit better. As with every MASH treatment, it works alongside the metabolic basics, the diet, exercise, and weight and glucose control that remain the foundation, rather than replacing them.

Guidance from the Clinic

"For years, the plain answer to a patient with fatty liver was that we had no approved drug, only the hard metabolic work. Now we have two, and semaglutide is a natural fit for the many patients whose fatty liver, weight, blood sugar, and heart risk are all tangled together, because it treats the whole tangle. What I keep clear is what it does and does not do. It is very good at quieting the liver inflammation, less dramatic at reversing the scarring, and it has not yet been shown to prevent cirrhosis or extend life, though the trial testing that is underway. I am also upfront that it is a long-term commitment, since the benefit fades if you stop, and that it works with the diet and exercise, never instead of them. For the right patient, it is an exciting option that happens to help several problems with one weekly shot."

Related at Fishtown Medicine

• Resmetirom (Rezdiffra): The First MASH Drug - the other approved MASH drug, working directly in the liver
• Survodutide (GLP-1/Glucagon) - the investigational GLP-1/glucagon drug with strong MASH data
• Fatty Liver (MASLD/MASH) - the disease and the metabolic work underneath it
• Tirzepatide (Zepbound, Mounjaro) - the dual agonist with its own emerging MASH data
• Ozempic vs Metformin - where semaglutide fits among metabolic drugs
• Metabolic Health and Insulin Resistance - the root driver of fatty liver

Scientific References

1. Sanyal AJ, Newsome PN, et al. "Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis." New England Journal of Medicine. 2025;392(17):1608-1618.
2. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. "Semaglutide and Cardiovascular Outcomes in Obesity Without Diabetes." New England Journal of Medicine. 2023;389(24):2221-2232.