Pemvidutide Achieves MASH Resolution in Phase 2b IMPACT Trial

Bottom line: Pemvidutide resolved MASH without worsening fibrosis at 24 weeks in the IMPACT Phase 2b trial, earning FDA Breakthrough Therapy designation and positioning this dual-agonist peptide as a serious contender in the crowded MASH pipeline.

Pemvidutide is a once-weekly injectable peptide that activates both GLP-1 and glucagon receptors in a balanced 1:1 ratio. Unlike pure GLP-1 receptor agonists that primarily reduce weight and improve insulin sensitivity, the glucagon component is designed to directly enhance hepatic fatty acid oxidation and reduce liver lipid accumulation — targeting the root pathology of metabolic dysfunction-associated steatohepatitis (MASH).

IMPACT Trial Design

The IMPACT Phase 2b trial was a randomized, double-blind, placebo-controlled study evaluating pemvidutide at 1.2 mg and 1.8 mg doses administered weekly in patients with biopsy-confirmed MASH. The dual primary endpoints at 24 weeks were:

1. MASH resolution without worsening of fibrosis
2. Fibrosis improvement (≥ 1 stage) without worsening of MASH

Key Findings

Results published in The Lancet showed:¹

• Primary endpoint met: Pemvidutide achieved statistically significant MASH resolution without worsening of fibrosis at 24 weeks compared to placebo.
• Fibrosis endpoint not met at 24 weeks: The co-primary endpoint of fibrosis improvement was not achieved at the 24-week timepoint, though this was expected given that fibrosis regression typically requires longer treatment durations.
• 48-week open-label extension data showed sustained weight loss and continued improvements in non-invasive fibrosis biomarkers, supporting the hypothesis that longer treatment would demonstrate histological fibrosis improvement.²

Regulatory Milestones

• January 5, 2026: FDA granted Breakthrough Therapy designation for pemvidutide in MASH.³
• Altimmune has completed end-of-Phase 2 discussions with the FDA and aligned on a Phase 3 design using biopsy-based endpoints over 52 weeks at the 1.8 mg dose.

Clinical Implication

For hepatologists and endocrinologists managing MASH patients, pemvidutide offers a mechanistically differentiated approach compared to resmetirom (thyroid hormone receptor agonist) and semaglutide. The dual agonist's ability to resolve steatohepatitis at 24 weeks — combined with meaningful weight loss — suggests it could serve patients with co-existing obesity and MASH. Watch for Phase 3 enrollment, expected to begin mid-2026.

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¹ Altimmune. Safety and efficacy of weekly pemvidutide versus placebo for metabolic dysfunction-associated steatohepatitis. The Lancet. 2025.

² Altimmune. Updated 48-week IMPACT results. January 2026.

³ FDA Breakthrough Therapy Designation for Pemvidutide. January 5, 2026.