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What Is Pemvidutide? Altimmune's GLP-1/Glucagon Dual Agonist for Weight Loss and MASH

Part of Weight Loss Drug Profiles: Every GLP-1 and GLP3 Agonist.

What Is Pemvidutide? Altimmune's GLP-1/Glucagon Dual Agonist for Weight Loss and MASH

Pemvidutide (ALT-801) is an investigational dual GLP-1/glucagon receptor agonist developed by Altimmune. It is a once-weekly subcutaneous injection designed with balanced 1:1 GLP-1 and glucagon receptor agonism — meaning it activates both receptors with equal potency rather than favoring one over the other.
In the Phase 2 MOMENTUM trial of 391 participants with obesity, pemvidutide produced up to 15.6% body weight loss at 48 weeks at the highest dose (2.4 mg), with over 30% of participants achieving 20% or more weight loss. In a separate Phase 2b IMPACT trial for metabolic dysfunction-associated steatohepatitis (MASH), pemvidutide achieved a 54.7% reduction in liver fat at 48 weeks and significant improvements in fibrosis markers.
Pemvidutide is not FDA approved and is not commercially available. The FDA has granted it both Fast Track designation (for MASH and alcohol use disorder) and Breakthrough Therapy Designation (for MASH, January 2026). The PERFORMA Phase 3 MASH trial has started and is enrolling participants.

How Pemvidutide Works

Balanced 1:1 GLP-1/Glucagon Mechanism

Altimmune describes pemvidutide as a balanced GLP-1/glucagon receptor agonist. GLP-1 activity is intended to reduce food intake and support glucose control; glucagon activity is part of the rationale for studying effects on liver fat and metabolism.

A laboratory receptor-activity ratio is not a clinical measure of how much liver fat or body weight someone will lose. It cannot establish that pemvidutide has stronger liver effects than survodutide.

Why Balanced Agonism Matters

The dual mechanism is a rationale for research in metabolic liver disease. Clinical trials must establish whether it improves MASH and fibrosis. A fall in liver fat or a blood-test marker is not, by itself, proof that scarring has reversed.

How Pemvidutide Relates to Retatrutide

Both pemvidutide and retatrutide target GLP-1 and glucagon receptors; retatrutide also targets GIP. Their separate trials do not isolate the contribution of GIP or establish which medicine works better.

Clinical Trial Data

Phase 2 MOMENTUM — Obesity (NCT05295875)

The MOMENTUM trial enrolled 391 adults with obesity (BMI 30+) or overweight (BMI 27+ with at least one comorbidity) without diabetes. Participants were randomized 1:1:1:1 to receive 1.2 mg, 1.8 mg, or 2.4 mg pemvidutide or placebo, administered once weekly by subcutaneous injection for 48 weeks.

DoseWeight Loss at 48 WeeksAchieved 20%+ Loss
2.4 mg-15.6%Over 30%
1.8 mg-11.2%—
1.2 mg-10.3%—
Placebo-2.2%—

Key findings:

  • 15.6% average body weight loss at 48 weeks on the highest dose (2.4 mg) in the trial’s reported analysis. This was not a head-to-head comparison with semaglutide
  • Lean mass preservation: MRI-based body composition analysis in 50 participants showed that only 21.9% of weight lost came from lean mass, with 78.1% from fat. This small substudy did not compare pemvidutide directly with another medicine, and lean mass is not synonymous with skeletal muscle
  • Preferential visceral fat reduction: At the 2.4 mg dose, visceral adipose tissue (VAT) was reduced by 28.3% versus 19.5% for subcutaneous adipose tissue — a meaningful distinction since VAT is more closely linked to cardiovascular risk
  • No clinically meaningful average heart-rate increase was reported by the sponsor; this is not a comparison with another medicine

Phase 2b IMPACT — MASH (NCT05989711)

The IMPACT trial enrolled 212 participants with biopsy-confirmed MASH and fibrosis stages F2 or F3, with and without diabetes. Participants were randomized 1:2:2 to receive placebo, 1.2 mg, or 1.8 mg pemvidutide once weekly for 48 weeks. The MASH trial answers a different question from the obesity trial.

Swipe sideways to see every column.

Endpoint1.2 mg1.8 mgPlacebo
Liver fat reduction-45.2%-54.7%-8.2%
ALT reduction-37.8 IU/L-37.4 IU/L-10.3 IU/L
cT1 reduction-124 ms-140 ms-21 ms
Weight loss-4.5%-7.5%-0.2%

Key findings:

  • 54.7% liver fat reduction at the 1.8 mg dose in the sponsor’s 48-week report
  • Statistically significant improvements in Enhanced Liver Fibrosis (ELF) score and Liver Stiffness Measurement (LSM) versus placebo, which are encouraging non-invasive signals rather than a biopsy finding of fibrosis reversal
  • ALT reduction — the average decline was nearly 38 IU/L; a group average reduction does not mean every participant’s ALT normalized
  • IMPACT used different doses and enrolled people with MASH and F2/F3 fibrosis. Its results should be interpreted separately from MOMENTUM
  • The 24-week biopsy results were published in The Lancet in November 2025

Pemvidutide Side Effects

Nausea and other gastrointestinal symptoms were common in the obesity development program. Safety results need to be tied to the trial and dose.

In the 48-week IMPACT MASH report, adverse events led to treatment discontinuation in 0% on 1.2 mg and 1.2% on 1.8 mg, versus 3.5% on placebo. These are MASH-trial rates, not the rates for the 2.4 mg obesity regimen in MOMENTUM.
The MOMENTUM report describes gastrointestinal adverse events, generally mild to moderate. Neither trial establishes better tolerability than another drug in a separate study, and absence of a clinically meaningful average heart-rate increase does not guarantee that an individual will have none.

How Pemvidutide Compares to Other Drugs

Pemvidutide and survodutide target GLP-1 and glucagon; retatrutide also targets GIP. The most useful comparison is the development question: pemvidutide’s PERFORMA trial is testing MASH outcomes, while its MOMENTUM obesity data remain Phase 2 evidence.

Separate weight-loss percentages, liver endpoints and adverse-event rates cannot establish a ranking. In particular, the 78.1% fat-loss share in the small MRI substudy does not prove superior muscle preservation, and IMPACT’s low discontinuation rate does not predict tolerability at a different dose in obesity.

Pemvidutide vs Retatrutide

Both drugs remain investigational. Retatrutide has an additional GIP target, but there is no direct pemvidutide–retatrutide comparison in the evidence summarized here. The drugs’ different trial populations, durations and endpoints prevent a claim that one is better for weight loss, liver disease or muscle retention.

Current Status and Availability

  • Developer: Altimmune (Gaithersburg, Maryland)
  • Regulatory status: Not FDA approved. Not approved in any country.
  • FDA designations: Breakthrough Therapy Designation (MASH, January 2026); Fast Track designation (MASH and alcohol use disorder)
  • MASH Phase 3: PERFORMA has started and is actively enrolling.
  • Obesity development: Altimmune completed an End-of-Phase 2 meeting with FDA for pemvidutide in obesity, but the primary development focus is MASH.
  • Other indications: Altimmune reports positive topline RECLAIM results in alcohol use disorder; RESTORE in alcohol-associated liver disease remains ongoing. See the current pipeline.
  • Commercial availability: Not available commercially. Cannot be prescribed or purchased.

Pemvidutide is currently only available to participants enrolled in clinical trials. There is no legitimate way to obtain pemvidutide outside of a clinical trial setting.

Frequently Asked Questions

What is pemvidutide?

Pemvidutide (ALT-801) is an investigational dual GLP-1/glucagon receptor agonist developed by Altimmune. It is a once-weekly subcutaneous injection with balanced 1:1 GLP-1 and glucagon receptor activity, being studied primarily for MASH (metabolic dysfunction-associated steatohepatitis) and obesity. It is not FDA approved.

How much weight can you lose on pemvidutide?

The Phase 2 MOMENTUM trial reported average weight loss of 15.6% with 2.4 mg weekly at 48 weeks. A separate MRI substudy in 50 treated participants found 78.1% of lost mass was fat. That does not establish muscle preservation in every participant.

What are pemvidutide's side effects?

Gastrointestinal symptoms, including nausea, are common. The often-quoted 0–1.2% discontinuation rates come from the 1.2 and 1.8 mg groups in the IMPACT MASH trial, not the 2.4 mg obesity regimen.

Is pemvidutide FDA approved?

No. Pemvidutide is not FDA approved and is not approved in any country. It has received FDA Breakthrough Therapy Designation for MASH (January 2026) and Fast Track designation for MASH and alcohol use disorder. The Phase 3 PERFORMA MASH trial has started.

How does pemvidutide help with liver disease (MASH)?

IMPACT found improvements in liver fat and non-invasive liver markers at 48 weeks. These results are encouraging but differ from biopsy-confirmed MASH resolution or fibrosis improvement. Phase 3 PERFORMA is evaluating MASH further.

How does pemvidutide compare to retatrutide?

Pemvidutide targets GLP-1 and glucagon; retatrutide also targets GIP. Separate studies cannot establish comparative weight loss, liver benefit or tolerability.

What makes pemvidutide different from survodutide?

Both target GLP-1 and glucagon. Their molecules and trial programs differ, but receptor-activity ratios and results from separate trials do not establish which drug is better for MASH or obesity.

Does pemvidutide preserve lean muscle mass?

A small MRI substudy found that 21.9% of lost mass was lean mass and 78.1% was fat. Lean mass still declined, and it is not identical to skeletal muscle. The study does not prove better muscle preservation than other medicines.

Sources

  1. Altimmune. "Phase 2 MOMENTUM trial results — 48-week topline data." Altimmune Press Release
  2. Altimmune. "IMPACT Phase 2b trial — 48-week MASH data." Altimmune Press Release
  3. Altimmune. "IMPACT Phase 2b trial data published in The Lancet." The Lancet
  4. Altimmune. "FDA Breakthrough Therapy Designation for pemvidutide in MASH." Altimmune Press Release
  5. Altimmune. "Pemvidutide pipeline overview." Altimmune
  6. Jastreboff AM, et al. "Retatrutide once weekly for treatment of obesity." New England Journal of Medicine. 2023. NEJM
This article is for informational purposes only and does not constitute medical advice. Pemvidutide is an investigational compound that has not been approved by the FDA or any regulatory authority. Always consult a healthcare provider before starting any medication.
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Retatrutide and similar peptides are investigational — not approved by the FDA or any regulator. Semaglutide and tirzepatide are prescription-only medicines, available only through a licensed prescriber.
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Sources

Grounded in primary sources
NEJMThe LancetJAMAFDAClinicalTrials.gov

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