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). A registrational Phase 3 trial for MASH is planned for 2026.

How Pemvidutide Works

Balanced 1:1 GLP-1/Glucagon Mechanism

Pemvidutide is a balanced dual agonist, meaning it activates GLP-1 and glucagon receptors in a 1:1 ratio. This distinguishes it from other GLP-1/glucagon dual agonists like survodutide, which has an 8:1 GLP-1-to-glucagon ratio. The balanced ratio means pemvidutide delivers a proportionally stronger glucagon signal relative to its GLP-1 activity.

GLP-1 receptor agonism provides the appetite-suppressing effects familiar from drugs like semaglutide:

• Reduces appetite by acting on hypothalamic GLP-1 receptors
• Slows gastric emptying, prolonging satiety after meals
• Stimulates insulin secretion in a glucose-dependent manner
• Suppresses post-meal glucagon from the pancreas

Glucagon receptor agonism adds metabolic effects that pure GLP-1 drugs do not provide:

• Increases energy expenditure — glucagon stimulates thermogenesis and raises resting metabolic rate
• Promotes hepatic fat oxidation — glucagon acts directly on liver cells to accelerate fat burning, which drives pemvidutide's liver-related benefits
• Reduces liver fat and inflammation — the direct hepatic effects are why pemvidutide shows particular promise for MASH

Why Balanced Agonism Matters

The 1:1 ratio of GLP-1 to glucagon agonism is central to Altimmune's strategy. In theory, a stronger glucagon signal relative to GLP-1 means more direct liver impact — greater hepatic fat oxidation, faster liver fat clearance, and stronger anti-inflammatory effects on the liver. The GLP-1 component counterbalances glucagon's glucose-raising effect to maintain glycemic safety.

This balanced approach may explain why pemvidutide has shown particularly strong liver fat reduction data relative to its weight loss numbers. The drug appears optimized for liver disease rather than maximum weight loss.

How Pemvidutide Relates to Retatrutide

Both pemvidutide and retatrutide include glucagon receptor agonism — a mechanism that most obesity drugs lack. The key difference is that retatrutide is a triple agonist (GLP-1 + GIP + glucagon), while pemvidutide is a dual agonist (GLP-1 + glucagon only). Retatrutide's additional GIP agonism likely contributes to its superior weight loss (up to 28.7% in TRIUMPH-4), but both drugs share the liver-targeting glucagon component.

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.

Key findings:

• 15.6% average body weight loss at 48 weeks on the highest dose (2.4 mg) — a meaningful result though lower than semaglutide 2.4 mg (15.3% at 68 weeks in STEP 1, noting the shorter trial duration)
• 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 compares favorably to other GLP-1 drugs where up to 40% of weight loss can come from lean mass
• 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 significant heart rate increases observed, unlike some GLP-1 receptor agonists

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 data is where pemvidutide stands out most clearly.

Key findings:

• 54.7% liver fat reduction at the 1.8 mg dose — a substantial effect driven by the glucagon component's direct hepatic action
• Statistically significant improvements in Enhanced Liver Fibrosis (ELF) score and Liver Stiffness Measurement (LSM) versus placebo, indicating anti-fibrotic activity
• ALT normalization — alanine aminotransferase reductions of nearly 38 IU/L indicate significant reduction in liver inflammation
• The lower weight loss numbers in this trial (4.5-7.5%) reflect the lower doses tested (capped at 1.8 mg vs 2.4 mg in MOMENTUM) and the patient population (MASH patients with more advanced metabolic disease)
• Results were published in The Lancet in November 2025

Pemvidutide Side Effects

The side effect profile is consistent with the GLP-1 drug class. The most common adverse events in clinical trials were gastrointestinal:

• Nausea — the most frequently reported side effect, occurring in approximately 33% of pemvidutide-treated participants. The majority of cases were mild to moderate.
• Diarrhea — mild to moderate, resolving without treatment
• Constipation — mild to moderate, resolving without treatment

Importantly, the discontinuation rates due to adverse events were very low:

• 0% discontinuation at the 1.2 mg dose
• 1.2% discontinuation at the 1.8 mg dose
• 3.5% discontinuation in the placebo group

These discontinuation rates are notably lower than many competing GLP-1 drugs and suggest good tolerability. Additionally, pemvidutide did not produce significant increases in heart rate — a side effect seen with some GLP-1 receptor agonists — and showed improvements in both systolic and diastolic blood pressure across all doses tested.

How Pemvidutide Compares to Other Drugs

Pemvidutide's position in the obesity drug landscape is distinctive. Its weight loss numbers (15.6%) are lower than survodutide (18.7%) and substantially below retatrutide (28.7%), but it differentiates on several fronts:

1. MASH focus: The Breakthrough Therapy Designation and strong liver fat reduction data position pemvidutide primarily as a MASH treatment rather than a pure obesity drug
2. Lean mass preservation: The MRI body composition data showing 78.1% fat-to-total weight loss ratio is among the best reported for any incretin-based drug
3. Tolerability: Very low discontinuation rates (0-1.2%) suggest good long-term adherence potential
4. Balanced glucagon agonism: The 1:1 ratio maximizes the liver-targeting glucagon effect, which may explain the strong MASH results relative to the moderate weight loss

Pemvidutide vs Retatrutide

Both pemvidutide and retatrutide activate the glucagon receptor, setting them apart from semaglutide and tirzepatide. But the similarities end there:

• Pemvidutide is a dual agonist (GLP-1 + glucagon). It omits GIP and leans into the liver-targeting glucagon mechanism with its balanced 1:1 ratio.
• Retatrutide is a triple agonist (GLP-1 + GIP + glucagon). The addition of GIP contributes to greater appetite suppression and insulin sensitization, resulting in substantially higher weight loss (28.7% vs 15.6%).

The shared glucagon component means both drugs show strong effects on liver fat. However, pemvidutide's development is focused primarily on MASH (with FDA Breakthrough Therapy Designation), while retatrutide is being developed primarily for obesity with MASH as a secondary indication.

If retatrutide represents the "maximum efficacy" approach with three receptors and the highest weight loss numbers, pemvidutide represents a more targeted approach — optimizing for liver disease with meaningful but more moderate weight loss.

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: Registrational Phase 3 trial planned for 2026. Will evaluate multiple doses over 52 weeks with biopsy-based endpoints. Plans to incorporate AIM-MASH AI Assist, the first AI pathology tool qualified by the FDA for use in MASH trials.
• 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: Phase 2 trials in alcohol use disorder (RECLAIM, initiated May 2025) and alcohol-associated liver disease (RESTORE, initiated July 2025) are ongoing.
• 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

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.