Pemvidutide: What the Evidence Shows

Pemvidutide is an experimental weekly injection from Altimmune that activates the GLP-1 and glucagon receptors. Its strongest evidence is in the liver. In a peer-reviewed phase 2b trial, 24 weeks of treatment cleared liver inflammation in 52% to 58% of people with MASH, against 20% on placebo, but did not significantly improve scarring.^[1] Its obesity results, up to 15.6% weight loss at 48 weeks, exist only as a company press release.^[6] The lean-mass claims are company-reported too. Pemvidutide is not approved. Altimmune now develops it for liver disease and for problem drinking; its phase 3 trial is in MASH, with first results expected in 2029.^[13][14]

What pemvidutide is

Pemvidutide, development code ALT-801, is a peptide injected under the skin once a week. Altimmune, which now describes itself as focused on serious liver diseases, owns and runs the program.^[13] The company calls it a “balanced 1:1” agonist, meaning it is designed to act on the GLP-1 and glucagon receptors about equally.^[13]

The two halves do different jobs. GLP-1 activity reduces appetite and drives weight loss, as it does with semaglutide. Glucagon activity acts directly on the liver, where it is thought to increase the burning of fat and reduce the making of new fat.^[2] That is why the drug was built for fatty liver disease first. In its first animal study, mice with diet-induced liver disease lost about a quarter of their body weight over 12 weeks and showed less liver fat and less inflammation than mice given semaglutide.^[4] Mouse results do not predict human ones, and the people who ran that study worked for or with Altimmune.^[4]

The pemvidutide record: what is peer-reviewed and what is not

The liver results

IMPACT is the trial that matters most, because it used liver biopsies, the measure regulators accept for MASH. MASH is the inflamed, scarring form of fatty liver disease. Across 83 US and Australian sites, 212 adults with moderate or advanced scarring (stages F2 and F3) were randomized to placebo or to 1.2 mg or 1.8 mg of pemvidutide, started at full dose without a slow increase.^[1]

• Inflammation resolved without scarring getting worse in 58% on 1.2 mg and 52% on 1.8 mg, against 20% on placebo. This primary endpoint was met.^[1]
• Scarring improved by at least one stage in 33% and 36%, against 28% on placebo. Neither difference was statistically significant, so the trial missed its second primary endpoint.^[1]
• Side effects were reported in 78% and 81% of people on pemvidutide and 67% on placebo, mostly mild or moderate. One person on the drug stopped because of side effects, against two on placebo.^[1]

Altimmune’s June 2025 release gave slightly different percentages, 59.1% and 52.1% against 19.1%, because it counted people with missing biopsies differently. The journal paper is the figure to use.^[10][1] Twenty-four weeks is short for scarring to reverse. At 48 weeks the company reported further improvement in blood tests and scans that track scarring, but those readings were not biopsies, and the 48-week data have not been published in a journal.^[11]

Earlier, smaller trials measured liver fat by MRI. After 12 weeks, liver fat fell by about half to two-thirds on pemvidutide, against 4.4% on placebo, and more than half the people on 1.8 mg reached a normal level.^[2] An independent meta-analysis that pooled the pemvidutide trials found consistent drops in liver fat and liver enzymes. Its authors still call for bigger trials, run for longer, before any effect on scarring can be confirmed.^[5] For the approved MASH treatment options, see GLP-1 drugs and fatty liver disease.

Weight loss: one trial, never published

MOMENTUM is the only obesity trial. It randomized 391 adults with a mean starting weight of about 104 kg to one of three doses or placebo for 48 weeks.^[6] Altimmune reported mean weight loss of 10.3%, 11.2% and 15.6% on 1.2 mg, 1.8 mg and 2.4 mg, against 2.2% on placebo.^[6] The trial finished in September 2023.^[7] Three years later there is no journal paper, and the ClinicalTrials.gov record has no results posted.^[7] Those numbers are company-reported and nothing more.

The release itself contains reasons for caution. About a quarter of people on pemvidutide did not finish the trial, and nearly two in five on placebo did not.^[6] On the two higher doses, about one in five stopped because of side effects, against 6.2% on placebo. Nausea affected 59.6% on 1.8 mg and 51.5% on 2.4 mg; vomiting about 28%.^[6] Heart rate rose 2.5 to 3.1 beats per minute on those doses, and no major heart events were reported.^[6]

In the liver trials, where most people were not chosen for obesity, weight loss was modest: up to 4.3% at 12 weeks^[2], and 5.0% to 6.2% at 24 weeks in IMPACT by the company’s count.^[10] Altimmune’s own papers argue that glucagon cuts liver fat directly, beyond what weight loss alone would do.^[2] That is a plausible reading of the mechanism. It also means pemvidutide at its MASH doses is not a strong weight-loss drug.

The lean-mass claim

Altimmune’s main selling point in obesity was the quality of the weight lost. In March 2024 it said 25.5% of the weight lost in MOMENTUM came from lean mass and 74.5% from fat, without giving the method or the number of people measured.^[8] In November 2024 it reported an MRI substudy with a lean loss ratio of 21.9%, and 19.9% in people aged 60 and over, and called this “class-leading.”^[9] It also reported a 28.3% drop in visceral fat, the fat around the organs, on 2.4 mg.^[9] None of this has been published in a journal.

Set against other drugs, the numbers look ordinary rather than special. A 2026 meta-analysis of 20 trials found lean mass made up 25.4% of the weight lost on tirzepatide, 35.2% on semaglutide and 26.2% with diet and lifestyle change alone.^[17] Different trials measured body composition with different scanners, and pemvidutide was never compared head to head, so no ranking holds. Lean mass also includes water and organs, not only muscle. A 2025 expert workshop that named pemvidutide among drugs pitched as muscle-preserving stressed how hard it is to separate true skeletal muscle from other lean tissue.^[18] Our lean mass review and muscle volume versus function explain why a scan ratio is not proof of preserved strength.

Alcohol use disorder and alcohol-related liver disease

Altimmune has since moved pemvidutide into alcohol. In RECLAIM, 100 adults with alcohol use disorder and excess weight took 2.4 mg or placebo for 24 weeks.^[16] The company reported that heavy drinking days fell by 4.20 a week on pemvidutide against 2.75 on placebo, and that weight fell 9.1% more than on placebo.^[12] Ten percent of people on the drug stopped because of drug-related side effects, against none on placebo, and one serious case of low blood sodium was judged possibly related.^[12] These are topline, company-reported results. FDA has granted Fast Track designation for this use.^[13]

A second trial, RESTORE, has enrolled 121 people with alcohol-related liver disease; its main measure is liver stiffness at 48 weeks. Altimmune expects topline results during late 2027.^[15][13] For what is known about semaglutide in the same condition, see semaglutide for alcohol use disorder.

Is pemvidutide approved? Where it stands

No regulator has approved pemvidutide. FDA has given it Fast Track designation for MASH and alcohol use disorder, and Breakthrough Therapy designation for MASH on the strength of the 24-week IMPACT data.^[13] Those designations speed FDA’s process. They are not approvals and do not mean the drug works.

The obesity story has a turn in it. In November 2024 Altimmune said it had agreed with FDA on a plan for four phase 3 obesity trials.^[9] By 2026 its filings listed three uses for pemvidutide, all tied to the liver or to drinking, with obesity gone, and the only phase 3 trial registered is in MASH.^[13][14] Those filings give no reason. Anyone quoting a date for pemvidutide as a weight-loss drug is guessing. Our GLP-1 pipeline tracker follows the program as filings and results land.

Pemvidutide vs survodutide and retatrutide

Survodutide, from Boehringer Ingelheim, uses the same GLP-1 plus glucagon mechanism and is years ahead: its 76-week phase 3 obesity trial already appears in a major journal, the NEJM.^[19] Retatrutide, from Eli Lilly, adds a third target, GIP, and is in phase 3, including a head-to-head trial against tirzepatide.^[23] None of the three has been compared with another in a trial, and the trials below differ in length, population and method, so the rows show what each drug has on record, not a ranking.

Read the survodutide column against the placebo, as we did in newer is not stronger: a new mechanism is not automatically a bigger effect. For pemvidutide the honest summary is narrower. Its liver biopsy result at 24 weeks is real and published. Its weight-loss and muscle claims rest on one unpublished trial. Its developer has steered it away from obesity, the market where survodutide and retatrutide are competing.

Is pemvidutide sold online?

Of the 157 FDA warning letters in our warning-letter tracker, none names pemvidutide. FDA’s page on unapproved GLP-1 drugs warns about research-labeled semaglutide, tirzepatide, retatrutide, survodutide and mazdutide, and does not mention pemvidutide.^[24] That is an absence of enforcement records, not a clean bill of health. Pemvidutide is not part of any FDA-approved drug and does not appear on FDA’s 503A bulks page, so there is no legal route for a pharmacy to compound it.^[25] Any vial sold under the name has no prescriber, no licensed pharmacy and no check on what is inside. Our guide to whether peptides are legal covers the rules. The only legal way to take pemvidutide is in a clinical trial.