MASH: Peptide Solutions for Liver Disease
MASH & Liver Disease
63%
Proportion of semaglutide-treated patients who achieved MASH resolution without worsening fibrosis at 72 weeks in the ESSENCE trial.
Bansal et al., Hepatology, 2025
Bansal et al., Hepatology, 2025
View as imageMetabolic dysfunction-associated steatohepatitis, now called MASH (formerly NASH), affects an estimated 5 to 14% of adults worldwide. It is the progressive, inflammatory form of fatty liver disease that drives liver fibrosis, cirrhosis, and eventually liver failure. MASLD has already become the leading indication for liver transplant in US women. Until 2024, there were zero FDA-approved treatments. Then resmetirom arrived in March 2024, followed by semaglutide in August 2025. Both approvals transformed a disease with no pharmacological options into one with a peptide-centered treatment pipeline.[7] For a detailed look at semaglutide's liver data specifically, see our article on semaglutide for liver fat. This article covers the full landscape of peptide-based approaches to MASH.
Key Takeaways
- Semaglutide 2.4 mg weekly achieved MASH resolution without worsening fibrosis in 63% of patients versus 34% on placebo in the ESSENCE trial (Bansal et al., Hepatology 2025)
- Tirzepatide achieved MASH resolution in 44 to 62% of patients across doses, with fibrosis improvement in 51 to 55% in a phase 2 trial (Loomba et al., NEJM 2024)
- Survodutide (dual glucagon/GLP-1 agonist) achieved MASH improvement in 47% of patients at the highest dose, with 34 to 36% achieving fibrosis improvement (Sanyal et al., NEJM 2024)
- The combination of efruxifermin (an FGF21 analog) with a GLP-1 receptor agonist showed enhanced liver fat reduction beyond either agent alone (Harrison et al., Clin Gastro Hepatol 2025)
- MASLD affects 38% of adults globally, with prevalence projected to exceed 55% by 2040
- Three distinct peptide agonist classes (GLP-1, GIP/GLP-1, and glucagon/GLP-1) are being studied, each targeting different metabolic pathways that drive liver fat accumulation and inflammation
What Is MASH and Why Does It Need Peptides
MASH is the inflammatory stage of metabolic dysfunction-associated steatotic liver disease (MASLD). The progression runs: healthy liver to simple steatosis (fat accumulation) to steatohepatitis (fat plus inflammation and hepatocyte ballooning) to fibrosis (scarring) to cirrhosis (irreversible scarring) to liver failure or hepatocellular carcinoma.
The disease is driven by metabolic dysfunction: insulin resistance, excess adiposity, lipotoxicity, and chronic low-grade inflammation. This metabolic root explains why peptide hormones that regulate metabolism, appetite, and glucose homeostasis have therapeutic potential. GLP-1 receptor agonists do not simply reduce liver fat by causing weight loss. They also reduce hepatic inflammation, improve insulin sensitivity, and may directly affect hepatic stellate cell activation, the cells responsible for fibrosis.[5]
The nomenclature shift from NASH to MASH (and NAFLD to MASLD) occurred in 2023 when the American Association for the Study of Liver Diseases adopted the new terminology to better reflect the metabolic basis of the disease and reduce stigma associated with the term "fatty."
Semaglutide: The First Peptide Approved for MASH
Semaglutide's journey to MASH approval began with a 2021 phase 2 trial published in the New England Journal of Medicine. In that trial, patients with biopsy-confirmed NASH received subcutaneous semaglutide 0.4 mg daily for 72 weeks. The primary endpoint was NASH resolution without worsening of fibrosis: 59% of the semaglutide group achieved this versus 17% on placebo.[1]
The ESSENCE phase 3 trial confirmed these results at the approved 2.4 mg weekly dose. At 72 weeks, 63% of semaglutide-treated patients achieved resolution of steatohepatitis without worsening fibrosis compared to 34% on placebo. Fibrosis improvement occurred in 37% of the semaglutide group versus 22% on placebo.[7]
The FDA granted accelerated approval in August 2025 for noncirrhotic MASH with moderate to advanced fibrosis (stages F2 to F3). The approval was based on histological improvement, with a confirmatory trial required to demonstrate clinical outcomes (reduced progression to cirrhosis, liver transplant, or death).
Semaglutide's mechanism in MASH extends beyond weight loss. A review by Barritt and colleagues outlined multiple pathways: reduced hepatic de novo lipogenesis through improved insulin sensitivity, decreased inflammatory cytokine production, reduced oxidative stress, and potentially direct anti-fibrotic effects through GLP-1 receptor signaling in hepatic stellate cells.[5]
Tirzepatide: Dual Agonism for Liver Disease
Tirzepatide targets both GIP and GLP-1 receptors, and its MASH data is striking. Loomba and colleagues published a phase 2 trial in the New England Journal of Medicine evaluating three doses of tirzepatide (5, 10, and 15 mg weekly) against placebo in patients with biopsy-confirmed MASH and stage F2 or F3 fibrosis.[2]
At 52 weeks:
- MASH resolution without worsening fibrosis: 44% (5 mg), 56% (10 mg), and 62% (15 mg) versus 10% on placebo
- Fibrosis improvement by at least one stage without worsening MASH: 55% (5 mg), 51% (10 mg), and 51% (15 mg) versus 30% on placebo
The fibrosis improvement rates are particularly notable. While semaglutide's fibrosis benefit has been modest, tirzepatide achieved fibrosis improvement in over half of treated patients. Whether GIP receptor agonism contributes to this advantage over pure GLP-1 agonism, or whether the greater weight loss with tirzepatide drives the difference, remains an open question.
For more context on tirzepatide's broader mechanism and how it differs from semaglutide, see our article on every GLP-1 receptor agonist compared.
Survodutide: Glucagon Receptor Agonism for the Liver
Survodutide is a dual glucagon/GLP-1 receptor agonist, distinct from tirzepatide (which targets GIP/GLP-1). The glucagon receptor component is the key differentiator: glucagon receptor activation directly increases hepatic fatty acid oxidation, reduces lipogenesis, and promotes hepatic lipid mobilization. This makes survodutide "liver-targeted" in a way that pure GLP-1 agonists are not.[6]
A phase 2 randomized trial published in the New England Journal of Medicine enrolled 293 patients with biopsy-confirmed MASH and stage F2 or F3 fibrosis. Patients received survodutide at 2.4, 4.8, or 6 mg weekly or placebo for 48 weeks.[3]
Results at 48 weeks:
- MASH activity improvement (NAS reduction of 2 or more points): 43% (2.4 mg), 48% (4.8 mg), and 62% (6 mg) versus 14% on placebo
- Fibrosis improvement by at least one stage: 34% (4.8 mg) and 36% (6 mg) versus 22% on placebo
- MASH resolution without worsening fibrosis: 47% at the highest dose versus 14% on placebo
Gastrointestinal side effects (nausea, diarrhea, vomiting) were the most common adverse events, consistent with other incretin-based therapies. For an overview of the full MASH peptide pipeline, see our article on every peptide being studied for MASH. Our article on survodutide specifically covers its pharmacology in greater depth.
Triple Agonists: Retatrutide on the Horizon
Retatrutide targets three receptors: GLP-1, GIP, and glucagon. By combining the appetite suppression of GLP-1, the metabolic enhancement of GIP, and the hepatic fat-burning of glucagon agonism, retatrutide represents the most comprehensive peptide approach to MASH currently in development.[4]
Phase 2 data showed dramatic liver fat reduction, with some patients achieving complete resolution of hepatic steatosis on MRI. Retatrutide also produced the greatest weight loss of any incretin-based therapy tested (up to 24% body weight reduction at 48 weeks). Phase 3 trials in MASH are underway, with results expected in 2026 to 2027.
The progression from single (semaglutide, GLP-1 only) to dual (tirzepatide, GIP/GLP-1; survodutide, glucagon/GLP-1) to triple agonism (retatrutide, GLP-1/GIP/glucagon) reflects a systematic exploration of which receptor combinations most effectively reverse the metabolic drivers of liver disease. For a detailed look at retatrutide's triple mechanism, see our article on retatrutide and liver fibrosis.
Combination Approaches: Peptides Plus Targeted Liver Therapy
The most promising near-term development may be combination therapy. Harrison and colleagues evaluated efruxifermin (an FGF21 analog that directly targets hepatic lipid metabolism and fibrosis) in combination with a GLP-1 receptor agonist in patients with MASH and type 2 diabetes.[8]
The rationale: GLP-1 agonists address the upstream metabolic drivers (obesity, insulin resistance, systemic inflammation), while FGF21 analogs target the intrahepatic processes (lipotoxicity, stellate cell activation, fibrogenesis). The combination produced greater liver fat reduction than either approach alone, suggesting additive or synergistic effects.
This combination strategy extends to semaglutide plus resmetirom (a thyroid hormone receptor beta agonist approved for MASH in 2024). By addressing metabolic drivers systemically with peptides and hepatic processes locally with targeted small molecules, combination regimens may achieve fibrosis reversal rates that monotherapy cannot.
How Peptides Compare to Resmetirom
Resmetirom, the first FDA-approved MASH therapy (March 2024), is a small molecule, not a peptide. It activates thyroid hormone receptor beta selectively in the liver, reducing hepatic lipid content and inflammation. In the MAESTRO-NASH trial, 26 to 30% of patients achieved MASH resolution at 52 weeks versus 10% on placebo.
The peptide approaches (semaglutide at 63%, tirzepatide at 44 to 62%) achieve higher MASH resolution rates. However, resmetirom has a different mechanism and different side effect profile (it does not cause nausea, the primary tolerability issue with incretin-based peptides). This positions resmetirom as a complement to peptide therapy rather than a competitor.
For patients who cannot tolerate GLP-1 receptor agonists due to gastrointestinal side effects, resmetirom offers a non-peptide alternative. For patients who can tolerate both, the combination may be superior to either alone.
The Fibrosis Question
The most important clinical endpoint in MASH is fibrosis stage. Liver fat and inflammation fluctuate, but fibrosis progression predicts cirrhosis, liver failure, and death. The peptide therapies show a consistent pattern: MASH resolution rates are high (44 to 63%), but fibrosis improvement rates are more modest (34 to 55%).[1][2][3]
This gap raises a question: do peptide therapies prevent fibrosis progression more effectively than they reverse existing fibrosis? Longer-term data will clarify this. The ESSENCE confirmatory trial for semaglutide will measure clinical outcomes (progression to cirrhosis, need for transplant, death) rather than just histological endpoints.
The fibrosis data also reveals interesting differences between agonist classes. Tirzepatide's fibrosis improvement rates (51 to 55%) are numerically higher than semaglutide's (37%) or survodutide's (34 to 36%), though cross-trial comparisons require caution due to differences in patient populations, fibrosis staging, and trial duration. For more on tirzepatide's liver-specific effects, see our article on tirzepatide and liver disease.
The Scale of the Problem
MASLD affects an estimated 38% of adults globally. MASH, the progressive inflammatory form, affects 5 to 14% depending on the diagnostic method used. By 2040, MASLD prevalence is projected to exceed 55% of adults. MASLD-related hepatocellular carcinoma and decompensated cirrhosis cases could increase by 65 to 100% by 2030 in Asian populations alone.
These numbers explain why the peptide treatment pipeline is so active. The combination of enormous disease burden, zero prior approved therapies (until 2024), and the metabolic nature of the disease creates a situation where existing peptide drugs (semaglutide, already approved for diabetes and obesity) can be repositioned for a new indication with a large unmet need.
The economic implications are equally significant. MASH-related healthcare costs in the US alone are estimated to exceed $100 billion annually by 2030, driven primarily by cirrhosis complications and liver transplantation. Peptide therapies that prevent progression to cirrhosis would generate enormous cost savings even at high drug prices.
Understanding the broader metabolic effects of GLP-1 drugs provides context for their liver benefits. Articles on how much weight semaglutide produces and semaglutide's body composition effects cover the systemic metabolic changes that contribute to hepatic improvement.
The Bottom Line
MASH has gone from zero approved therapies to an active pipeline centered on peptide agonists in under two years. Semaglutide achieved FDA approval for MASH in 2025 with 63% resolution rates. Tirzepatide and survodutide show comparable or superior results in phase 2 trials. The field is moving toward combination approaches that pair systemic peptide therapy with liver-targeted agents, aiming to close the gap between high MASH resolution rates and more modest fibrosis improvement rates.