GLP-1 and Fatty Liver (MASLD/MASH): ESSENCE, SYNERGY-NASH

Metabolic dysfunction-associated steatohepatitis (MASH, formerly NASH) is on track to become the leading cause of liver transplant in the United States. GLP-1 agonists are a leading candidate therapy: semaglutide phase 3 (ESSENCE) showed resolution of steatohepatitis without worsening fibrosis, and tirzepatide phase 2 (SYNERGY-NASH) showed substantial fibrosis improvement.

Why fatty liver became a hot indication

MASLD prevalence in U.S. adults is now ~38%, and MASH (the inflammatory subset that progresses to cirrhosis) affects roughly 5%. The pathophysiology overlaps almost completely with metabolic syndrome — insulin resistance, visceral adiposity, dyslipidemia. GLP-1 agonists improve every one of these inputs, so liver benefit is mechanistically expected.

What the trials showed

ESSENCE (semaglutide 2.4 mg): Phase 3 trial in MASH with stage F2–F3 fibrosis. Interim 72-week data showed MASH resolution in ~62% of treated participants vs ~34% placebo, with fibrosis improvement in ~37% vs ~22%. Full results expected 2026.

SYNERGY-NASH (tirzepatide): Phase 2, 190 patients with MASH and stage F2–F3 fibrosis. At 52 weeks, MASH resolution rates were 44%, 56%, and 62% with tirzepatide 5/10/15 mg vs 10% placebo. Phase 3 program is underway.

How GLP-1s compare to resmetirom

Resmetirom (Rezdiffra) was approved in March 2024 as the first MASH-specific therapy. It acts on the thyroid hormone receptor-β in the liver and works without inducing weight loss. Effect sizes for MASH resolution are smaller than GLP-1 phase 2 data, but it has a clean FDA indication and is dosed orally. For a patient with MASH but normal weight, resmetirom is the obvious choice. For a patient with MASH and obesity, the GLP-1 may be preferred (or combined therapy may be considered).

Off-label use today

Currently, neither semaglutide nor tirzepatide carries an FDA MASH indication. Treatment is off-label, typically driven by overlapping indications (obesity, T2D). Clinicians should document the metabolic rationale and follow standard monitoring.

Practical monitoring

• Baseline ALT, AST, GGT, platelets, FIB-4 score, and either FibroScan/elastography or MRE.
• Repeat noninvasive fibrosis assessment at 12 months.
• If FIB-4 ≥2.67 or MRE ≥3.5 kPa at baseline, hepatology referral is appropriate.

References

ESSENCE interim results (Sanyal et al., 2024), SYNERGY-NASH (Loomba et al., NEJM 2024). See our research bibliography for full citations.