2026-08-21 · pemvidutide, ALT-801, Altimmune, GLP-1, glucagon, dual agonist, MASH, next-generation obesity drug, obesity pipeline

What is pemvidutide?

Pemvidutide (development code ALT-801) is an investigational once-weekly subcutaneous peptide from Altimmune (Gaithersburg, Maryland) that activates two receptors in one molecule — the GLP-1 receptor and the glucagon receptor. The GLP-1 arm suppresses appetite in the same way Wegovy does. The glucagon arm mobilizes hepatic fat and raises resting energy expenditure. Pemvidutide is in Phase 2 development for both obesity and MASH (fatty liver disease) and is not FDA-approved.

How does pemvidutide compare to semaglutide (Wegovy)?

Semaglutide is a pure GLP-1 receptor agonist — one receptor, one satiety arm. Pemvidutide activates GLP-1 plus glucagon, adding a hepatic-fat and energy-expenditure lever the single-receptor drugs do not have. In cross-trial terms, IMPACT Phase 2 reported roughly 15.6 percent placebo-adjusted weight loss at 48 weeks for pemvidutide 2.4 mg versus STEP-1's roughly 14.9 percent mean loss for semaglutide 2.4 mg at 68 weeks. Pemvidutide's distinguishing signal is the lipid reduction (LDL, ApoB, triglycerides) that semaglutide does not produce.

When will pemvidutide be FDA-approved?

Realistically 2029 to 2030 at the earliest for obesity, and potentially 2030 or later for MASH. Altimmune has publicly guided the pivotal Phase 3 obesity program (IMPACT-3) to enroll in 2025 to 2026 with a primary readout target of 2028 to 2029. A standard 12 to 18 month FDA review after a Phase 3 filing puts earliest approval in 2029 to 2030. The MASH Phase 2b biopsy-proven readout is expected in 2026 and a Phase 3 MASH program would follow. No legitimate US access route exists before then.

How does pemvidutide compare to survodutide?

Both are GLP-1 / glucagon dual agonists. Survodutide (Boehringer Ingelheim / Zealand Pharma) is further along — Phase 3 SYNCHRONIZE obesity readout expected mid-2026, and it holds FDA Breakthrough Therapy Designation for MASH with F2 or F3 fibrosis. Pemvidutide is Phase 2 with peak weight loss of roughly 15.6 percent at 48 weeks versus roughly 18.7 percent for survodutide 4.8 mg at 46 weeks. The distinctive pemvidutide signal is LDL and ApoB reduction — survodutide showed a small LDL rise in Phase 2b. Realistic US availability is 12 to 18 months behind survodutide.

How much weight did people lose on pemvidutide in the IMPACT trial?

IMPACT Phase 2 (n=390, 48 weeks, three dose arms) reported roughly 15.6 percent placebo-adjusted weight loss at the 2.4 mg dose at 48 weeks, with a clear dose-response across the 1.2 mg, 1.8 mg, and 2.4 mg arms. Placebo-arm weight loss was roughly 2 percent. Critically, the weight-loss curve had not plateaued at 48 weeks — the definitive plateau will be characterized in the Phase 3 IMPACT-3 obesity program.

Is compounded pemvidutide available?

No. Pemvidutide is a proprietary peptide belonging to Altimmune, has never been on the FDA drug-shortage list, and has no legitimate 503A or 503B compounding pathway even in an emergency shortage. No US compounding pharmacy has legal access to the active pharmaceutical ingredient. Any product sold in 2026 as 'pemvidutide' or 'ALT-801' by a telehealth peptide clinic, gray-market compounder, or overseas pharmacy is either counterfeit or an unrelated peptide and should not be injected. See our compounded semaglutide and tirzepatide safety guide for the current enforcement landscape.

Can pemvidutide treat MASH (fatty liver)?

The IMPACT hepatic-imaging sub-analysis reported a roughly 55 to 65 percent reduction in MRI-PDFF (liver fat) at 24 weeks at the 2.4 mg dose — comparable to survodutide's Phase 2 substudy and larger than the roughly 30 to 40 percent PDFF reduction reported for semaglutide monotherapy in equivalent trials. Altimmune is running a parallel Phase 2b MASH program in biopsy-proven F2/F3 patients, with a paired-biopsy readout expected in 2026. Pemvidutide is not FDA-approved for MASH. The only currently approved MASH drug in the US is resmetirom (Rezdiffra).

Should I wait for pemvidutide or start Wegovy or Zepbound now?

Start the FDA-approved option now if it is clinically appropriate. Pemvidutide is not on any US pharmacy shelf and will not be for at least 3 to 4 years. Wegovy (semaglutide) and Zepbound (tirzepatide) produce durable, clinically meaningful weight loss today, and switching to a next-generation drug at approval is straightforward. If MASH plus obesity is your specific presentation, resmetirom (Rezdiffra) is the only currently approved MASH drug and semaglutide has an ESSENCE MASH indication filed with the FDA.

Pemvidutide for Weight Loss: 15.6% at 48 Weeks in Altimmune’s IMPACT Phase 2 (2026 Update)

Pemvidutide is not FDA-approved and is not sold anywhere in the United States as of August 2026 — no legitimate pharmacy, telehealth clinic, or compounding operation can supply it. It is an investigational once-weekly injection from Altimmune (Gaithersburg, Maryland), with development code ALT-801. The molecule is a dual GLP-1 / glucagon receptor agonist in Phase 2 development for both obesity and MASH (metabolic dysfunction-associated steatohepatitis). Any product marketed today as “pemvidutide” or “ALT-801” from an overseas pharmacy, telehealth peptide site, or gray-market compounder is either counterfeit or research-chemical peptide — see compounded semaglutide and tirzepatide safety for the analytical picture on what actually shows up in those vials.

This page explains what pemvidutide is, what the IMPACT Phase 2 obesity trial and its hepatic-imaging sub-analysis reported, how the molecule compares to survodutide, mazdutide, and the rest of the next generation weight loss drugs pipeline, and the honest 2026 read for US patients — including why the earliest realistic availability is 2029 to 2030.

What pemvidutide is

Pemvidutide (ALT-801) is a once-weekly subcutaneous peptide engineered by Altimmune — a Gaithersburg, Maryland biotechnology company. It activates two receptors in one molecule: the GLP-1 receptor and the glucagon receptor. Doses studied in the pivotal Phase 2 program were 1.2 mg, 1.8 mg, and 2.4 mg weekly, with 2.4 mg as the target obesity dose carried forward for Phase 3.

Plain-English mechanism: Pemvidutide activates two receptors at once — GLP-1 for appetite suppression and glucagon for direct hepatic-fat mobilization — which is what makes it a candidate for both weight loss and MASH.

The receptor pairing places pemvidutide in the same GLP-1 / glucagon dual class as survodutide (Boehringer Ingelheim / Zealand Pharma, Phase 3), mazdutide (Innovent / Lilly China, approved in China June 2025), and the historical cotadutide program (MedImmune / AstraZeneca, discontinued). It is mechanistically distinct from single-agonist semaglutide (Wegovy, GLP-1 only) and from GLP-1 / GIP dual tirzepatide (Zepbound), which uses a different second receptor.

Dose and route — how pemvidutide sits alongside the GLP-1 and dual-agonist family

The table below places pemvidutide against the closest current comparators — the two other GLP-1 / glucagon dual agonists in active development, plus semaglutide as the pure-GLP-1 anchor.

Two things to read from that table. First, pemvidutide’s target dose (2.4 mg) is the same nominal number as Wegovy’s maintenance dose — but the molecules and receptors are not comparable, and the same milligram number does not imply the same exposure. Second, all three GLP-1 / glucagon dual agonists are once-weekly SC, but survodutide titrates through a wider dose range and mazdutide uses higher absolute doses. Pemvidutide sits in the middle on both dimensions.

IMPACT Phase 2 obesity trial

The IMPACT Phase 2 trial is the pivotal obesity readout that anchored the pemvidutide obesity thesis. Design highlights:

• Population: approximately 390 adults with obesity (BMI ≥ 30, or ≥ 27 with at least one weight-related comorbidity).
• Duration: 48 weeks, double-blind, placebo-controlled.
• Arms: pemvidutide 1.2 mg, 1.8 mg, 2.4 mg weekly, plus matching placebo, on top of lifestyle counseling.
• Primary endpoint: mean percent change in body weight at week 48.
• Readout: topline announced in Q4 2024, full 48-week data in 2025.

The headline result was a clear dose-response with roughly 15.6 percent placebo-adjusted weight loss at 48 weeks at the 2.4 mg dose. Placebo-arm weight loss was roughly 2 percent. Critically, the weight-loss curve had not plateaued at 48 weeks — the trajectory suggests further loss with longer treatment, and Phase 3 IMPACT-3 will characterize where the plateau actually lands.

The secondary lipid signals are the distinctive part of the IMPACT readout, and the reason Altimmune positions the molecule against pure GLP-1 mono-agonism on a cardiometabolic story:

• LDL-cholesterol reduction ~15 percent at the 2.4 mg dose.
• Triglyceride reduction ~20 percent.
• ApoB reduction ~13 percent.

Those numbers are meaningfully different from the neutral-to-slightly-adverse LDL profile reported for survodutide in Phase 2b (Le Roux 2024 reported a small LDL rise). Altimmune’s mechanism read is that the glucagon arm — which activates hepatic β-oxidation and reduces de novo lipogenesis — drives the lipid benefit that separates pemvidutide from the rest of the class.

MASH signal and the IMPACT hepatic sub-analysis

Roughly 40 to 70 percent of adults with obesity have some degree of steatotic liver disease, and MASH — the inflammatory stage — is now among the leading causes of liver transplantation in the United States. The IMPACT program included a hepatic-imaging sub-analysis using MRI-PDFF (proton density fat fraction), the FDA-accepted non-invasive endpoint for liver-fat quantification.

The sub-analysis reported an MRI-PDFF reduction of roughly 55 to 65 percent at 24 weeks at the 2.4 mg dose — comparable to the survodutide Phase 2 hepatic substudy and larger than the roughly 30 to 40 percent PDFF drop reported for semaglutide monotherapy in equivalent trials. Those numbers are the basis for Altimmune’s parallel Phase 2b MASH program in biopsy-proven F2/F3 fibrosis (n ≈ 200), with a paired-biopsy readout expected in 2026.

The dedicated MASH program is important context because MASH resolution and fibrosis improvement — the FDA-accepted regulatory endpoints — require paired liver biopsies, not MRI-PDFF. The MRI signal is a leading indicator; the biopsy data will determine whether pemvidutide can pursue a MASH label alongside its obesity indication. For the currently approved MASH drug, see resmetirom (Rezdiffra) for MASH. For the closest pipeline peer with biopsy-proven Phase 2 MASH data, see the survodutide pillar (Sanyal 2024 NEJM reported 63 percent MASH resolution at 48 weeks).

Mechanism — the glucagon arm

The two-arm mechanism is what separates pemvidutide from every currently-approved US obesity drug — and what drives both the lipid and the hepatic-fat signals.

GLP-1 arm. Same as semaglutide: activates the GLP-1 receptor on pancreatic beta-cells, on hypothalamic satiety circuits, and on gastric and intestinal smooth muscle. Downstream effects are glucose-dependent insulin secretion, delayed gastric emptying, and appetite suppression — the mechanism that produces the shared class effect across every GLP-1-based drug (see GLP-1 medications compared).

Glucagon arm. Activates the glucagon receptor on hepatocytes. In isolation, glucagon raises fasting blood sugar. In co-agonism with GLP-1, the net glucose effect is neutral or favorable — GLP-1’s insulinotropic action offsets the glucagon-driven hepatic glucose output. What is left is a distinct set of glucagon-driven effects that pure GLP-1 drugs cannot deliver: upregulation of hepatic fatty-acid oxidation, reduction in de novo lipogenesis, mobilization of hepatic fat (the 55–65 percent MRI-PDFF drop), and a modest rise in resting energy expenditure. The additive lipid benefit (LDL, ApoB, triglycerides) is a direct downstream consequence of that glucagon-arm signaling.

Cegla 2021 (J Clin Endocrinol Metab) is the canonical review of GLP-1 / glucagon co-agonism pharmacology, and Ambery 2018 (Lancet) reported the original cotadutide Phase 1 dataset that established the class-wide pattern.

The mechanism carries a cost. Glucagon co-agonism produces a small but reproducible heart-rate increase of roughly +3 to +5 bpm at target doses, consistent across pemvidutide, survodutide, mazdutide, and cotadutide. IMPACT Phase 2 reproduced this signal at 48 weeks — the class-typical trade-off for the glucagon lever.

Six-row pipeline comparison

The table below sets pemvidutide against five other next-generation obesity drugs at various stages of development. Numbers are the highest Phase 2 or Phase 3 topline reported for each drug at the timeframes noted.

Cheat-sheet caption: Pemvidutide is the only pipeline GLP-1/glucagon dual reporting an LDL-and-ApoB reduction as a secondary endpoint — the survodutide and mazdutide programs did not observe or did not emphasize this signal. On pure weight-loss magnitude pemvidutide sits behind survodutide, mazdutide (at higher doses), and the triple-agonist retatrutide. Its distinctive value proposition is the cardiometabolic-lipid story, not maximum weight loss.

Safety profile from Phase 2

The IMPACT Phase 2 safety picture is a GI-dominant tolerability profile consistent with the class, plus a small glucagon-attributable heart-rate signal and a transient LFT rise.

No unexpected off-target signal was reported at 48 weeks. The class-defining safety questions that still require Phase 3 exposure to answer are the same ones that apply to every drug in the incretin class: thyroid C-cell tumor risk (a class label on all GLP-1 drugs), pancreatitis excess above the GLP-1-class baseline, and gastroparesis and gallbladder events. IMPACT’s 390-patient, 48-week window is too small and too short to resolve any of these — that is what a Phase 3 program with several thousand patients and a cardiovascular outcomes trial is designed to do.

Phase 3 timeline expectations

Altimmune has publicly guided pemvidutide into a Phase 3 obesity program (IMPACT-3) with enrollment starting in 2025 to 2026 and a target primary readout in 2028 to 2029. The parallel Phase 2b MASH program in biopsy-proven F2/F3 fibrosis reads out in 2026 and a Phase 3 MASH program would follow contingent on that outcome.

Given a standard 12 to 18 month FDA review after a Phase 3 NDA filing, earliest realistic FDA availability = 2029 to 2030 for the obesity indication, and potentially 2030 or later for MASH.

That timing puts pemvidutide roughly 12 to 18 months behind survodutide (Phase 3 SYNCHRONIZE obesity readout mid-2026, earliest US availability 2027 to 2028) and behind the currently approved options (tirzepatide 2023, semaglutide 2021) by several years. It also puts it after orforglipron, which is on track to be the first oral next-generation option to reach US pharmacy shelves.

The Altimmune commercial and licensing angle

Altimmune is a small-cap biotechnology company (approximate market capitalization $200 million to $1 billion depending on the cycle) without an established in-house global commercialization footprint. That is the ordinary pattern for a Phase 2 clinical-stage biotech with a lead asset in a large market — the realistic commercial outcomes are:

• Big Pharma licensing deal — an out-license to a company with existing metabolic-disease commercial infrastructure. Potential partners publicly discussed in industry coverage include Merck, Roche, Sanofi, and Amgen.
• Full acquisition — outright purchase of Altimmune by a partner, most likely after the 2026 MASH biopsy readout or the Phase 3 obesity data.
• Zealand-Novo-style partnership — a co-development structure in which Altimmune retains equity in the asset while a partner runs the commercial rollout.

For patients the ownership question matters because it determines pricing, formulary placement, and prior-authorization pathways in 2029 to 2030 (see GLP-1 cost and insurance for the current pricing landscape).

Honest phrasing: Whether pemvidutide reaches patients as an Altimmune-branded product or a partner-branded product will be decided by the 2026 MASH biopsy data and the 2028 to 2029 Phase 3 obesity results, and any deal that follows.

What pemvidutide does not do in 2026

Explicit list, because the noise around next-generation drugs consistently overstates what Phase 2 topline data means for a US patient today:

• Not FDA-approved for any indication. No US access route exists.
• Not compoundable. Pemvidutide is a proprietary peptide, has never been on the FDA drug-shortage list, and has no legitimate 503A or 503B pathway even in an emergency shortage. Do not respond to any “compounded pemvidutide” or “ALT-801” grey-market vendor — the molecule is not manufacturable via the compounding-pharmacy pathway and any product sold under that name is mislabeled, an unrelated compound, or counterfeit.
• No head-to-head trials against semaglutide or tirzepatide. Every side-by-side comparison in this article is cross-trial and directional, not definitive.
• No cardiovascular outcomes trial (CVOT). Cardiovascular benefit is inferred from the lipid and weight-loss data, not proven; the class already carries CVOT evidence for semaglutide (SELECT) and tirzepatide (SURPASS-CVOT), but pemvidutide has none.
• No T2D primary-endpoint program. IMPACT reported metabolic secondary endpoints (fasting glucose, HbA1c, insulin sensitivity), but pemvidutide is not being filed for a Type 2 diabetes indication.

Practical US-2026 read

Three-sentence honest bottom line, for a reader making a decision today.

If you are choosing weight-loss pharmacotherapy today, pemvidutide is not on the shelf and will not be for 3 to 4 years. Wegovy, Zepbound, and — from 2026 to 2027 — orforglipron are the near-term FDA-approved options. If MASH plus obesity is your specific presentation, resmetirom (Rezdiffra) is the only currently approved MASH drug and semaglutide has an ESSENCE MASH indication filed with the FDA — start there, not on a Phase 2 investigational.

If you are tracking the biotech pipeline for a family member or a patient, the most useful signals are Altimmune’s Q4-2025 through Q4-2026 conference-call and press-release cadence and the corresponding ClinicalTrials.gov IMPACT-3 obesity and IMPACT-MASH postings. The 2026 MASH biopsy readout and the Phase 3 IMPACT-3 enrollment update are the two milestones that will most affect the pemvidutide trajectory over the next 18 months.

For the full 2026 map of pipeline drugs, mechanism trees, and the practical “should I wait?” protocol, see the next generation weight loss drugs pillar. For the on-label 2026 options that are actually on pharmacy shelves today, see prescription weight loss medications.