Trial review

Tirzepatide and Fatty Liver / MASH

What the trial did

SYNERGY-NASH randomised adults aged 18 to 80 with biopsy-confirmed MASH, stage F2 or F3 fibrosis, a BMI between 27 and 50 and a NAFLD activity score of 4 or above, with or without type 2 diabetes. Participants were assigned 1:1:1:1 to once-weekly subcutaneous tirzepatide at 5, 10 or 15 mg, or placebo, for 52 weeks, across 130 sites in ten countries.

The primary endpoint was MASH resolution without worsening of fibrosis on liver histology — a biopsy endpoint, which is considerably more demanding than the imaging surrogates most liver research relies on.

It was published in the New England Journal of Medicine in July 2024 (Loomba R et al., 391(4):299-310) and registered as NCT04166773.

Why we have not published a resolution percentage

Because the secondary sources disagree, and by a wide margin.

One reports resolution at 51.8%, 62.8% and 73.3% for the 5, 10 and 15 mg arms against 13.2% on placebo. Another reports 62% at 15 mg against 10% on placebo. Those cannot both describe the same arm of the same trial, and neither states which analysis produced its figure.

Publishing either would mean picking one at random and presenting it as settled. We have recorded both, flagged the conflict, and opened a task to read the NEJM full text and record the exact rate per arm with its estimand named. That is the same standard applied to SURMOUNT-1's two estimands and to the orforglipron figures.

What can be said confidently

That tirzepatide was superior to placebo on a biopsy-confirmed histological endpoint, that the effect appeared dose-related, and that fibrosis improvement was less pronounced than MASH resolution at 52 weeks.

That last point matters more than it reads. MASH resolution is inflammation settling; fibrosis is scarring, and it is fibrosis stage that predicts progression to cirrhosis and liver-related death. A drug that resolves inflammation without reversing established scarring is doing something valuable and incomplete.

What is not established

• Approval status. One commercial source states tirzepatide is FDA-approved for MASH. Trade coverage from June 2026 describes it as under evaluation, and the registry lists SYNERGY-NASH as phase 2. We do not report it as approved, and the source making that claim also sells peptides.
• Long-term outcomes. A phase 3 programme, SYNERGY-OUTCOMES, is reported to have launched in late 2025 targeting completion in 2032. Histological improvement at 52 weeks is not the same as fewer transplants or deaths.
• Comparison with semaglutide. No head-to-head trial has compared the two for liver endpoints. Semaglutide's phase 2 MASH work reported resolution around 59% against 17% placebo, but different trials with different populations are not comparable.
• Anything about compounded preparations. No compounded product appears in any MASH trial.

What a patient with fatty liver disease should take from this

That this is a real and reasonably strong signal on a demanding endpoint, in a condition with few options — and that it is phase 2 evidence for an unapproved indication.

If you have MASH and obesity, this is worth raising with a hepatologist rather than with a weight-management platform. The biopsy staging that determines whether the trial population resembles you is not something an intake questionnaire establishes.

Questions readers actually ask