Pemvidutide: A GLP-1/Glucagon Dual Agonist in Trials for Obesity and MASH

Pemvidutide (developer code ALT-801, from Altimmune) is an investigational, once-weekly injectable peptide being studied for obesity and for metabolic dysfunction-associated steatohepatitis (MASH). It is described by its developer as a balanced 1:1 GLP-1/glucagon dual receptor agonist — a single molecule designed to hit two receptors at once. This research log entry summarizes what the published and reported trial data actually show. It is not medical advice, and pemvidutide is not approved by the FDA for any use.

The dual-agonist rationale: what the glucagon arm adds

Most of the weight-loss peptides people recognize — like semaglutide — act on the GLP-1 receptor, which drives appetite suppression and slowed gastric emptying. Pemvidutide adds a second signal: agonism at the glucagon receptor.

The stated mechanistic logic is that GLP-1 receptor activity mediates appetite reduction and weight loss, while glucagon receptor activity acts more directly on the liver. Glucagon-receptor agonists are reported to stimulate hepatic fatty-acid oxidation and inhibit lipogenesis, which the developer frames as a potential mechanism for reducing liver fat beyond what weight loss alone would achieve. This is the same two-hormone thesis behind other agents in the class, such as survodutide, another GLP-1/glucagon dual agonist in development.

An important caveat: glucagon has complex metabolic effects (including on glucose), so the balance between the two receptor activities is a key design variable, and long-term outcomes remain under study.

MOMENTUM: the Phase 2 obesity trial

MOMENTUM was a 48-week, placebo-controlled Phase 2 trial that enrolled 391 participants with overweight or obesity (with at least one comorbidity) and without diabetes. Participants were randomized to weekly pemvidutide at 1.2 mg, 1.8 mg, or 2.4 mg, or placebo, alongside diet and exercise.

Reported mean weight loss at 48 weeks was 10.3%, 11.2%, and 15.6% for the 1.2 mg, 1.8 mg, and 2.4 mg doses respectively, versus 2.2% for placebo. More than 30% of participants on the 2.4 mg dose achieved 20% or greater weight loss.

A point the developer emphasized was body composition: of the total weight lost, roughly 78% was attributable to fat and about 22% to lean mass. Altimmune framed this lean-mass preservation as favorable relative to what has been publicly reported for some other incretin drugs, where lean mass has accounted for a larger share of total weight loss. The trial also reported improvements in serum lipids, BMI, and blood pressure. These are Phase 2 findings and were presented at the American Diabetes Association's Scientific Sessions.

IMPACT: the Phase 2b MASH trial

IMPACT tested pemvidutide (1.2 mg and 1.8 mg) in biopsy-confirmed MASH. The results were released in stages during 2025 and 2026.

Liver fat and 24-week histology. Reported liver-fat reductions were 45.2% (1.2 mg) and 54.7% (1.8 mg) versus 8.2% for placebo. On the primary histology endpoint, MASH resolution without worsening of fibrosis was achieved in 59.1% (1.2 mg) and 52.1% (1.8 mg) of participants versus 19.1% for placebo (p<0.0001 for both doses).

48-week fibrosis signals. At 48 weeks, both doses produced statistically significant improvements versus placebo in non-invasive tests of fibrosis, including Enhanced Liver Fibrosis (ELF: −0.49 and −0.58 vs +0.16) and Liver Stiffness Measurement (LSM). The proportion of patients achieving both a ≥0.5 ELF reduction and a ≥30% LSM reduction at week 48 was reported as 27.8% for the 1.2 mg dose versus 3.2% for placebo. Altimmune reported that pemvidutide was well tolerated with low discontinuation rates due to adverse events.

The IMPACT data were published in The Lancet with a late-breaking presentation at the AASLD Liver Meeting 2025, and additional 48-week metabolic data were presented at EASL 2026.

Regulatory status and what to watch

The FDA granted pemvidutide Breakthrough Therapy Designation for MASH (based on the 24-week IMPACT data), along with Fast Track designations. Altimmune has reported alignment with the FDA on parameters for a registrational Phase 3 trial in MASH patients with moderate-to-advanced fibrosis.

Breakthrough and Fast Track designations are process tools that can speed review — they are not approvals and do not guarantee one. For general background on how the agency classifies research compounds versus approved drugs, see our FDA status reference. Pemvidutide remains investigational and available only within clinical trials.

Bottom line for the research log

Pemvidutide is one of the more closely watched dual agonists because its glucagon component targets the liver directly, and its Phase 2 obesity and Phase 2b MASH datasets have both read out with statistically significant results across weight, liver fat, and fibrosis markers. The next milestone is Phase 3. As always, Phase 2/2b results can change in larger, longer trials, and none of this establishes safety or efficacy for personal use.

PepStash is a research log and reference tool. This article is educational and is not medical advice — it does not diagnose, treat, or recommend any protocol. Regulatory status and trial data change; always verify against primary sources and consult a licensed physician before making any decisions about your health.