โš—๏ธ Phase 2 Complete ๐Ÿ’ช Best Muscle Preservation Altimmune ยท Weekly injection

Pemvidutide

ALT-801 ยท GLP-1 + Glucagon Dual Agonist ยท Est. Phase 3: 2025-2026

Pemvidutide targets fat while protecting your muscle better than any other weight loss drug tested. Phase 2 showed only 21.9% lean mass loss, compared to up to 40% with standard GLP-1 drugs. The best fat-to-muscle ratio in its class.

๐Ÿ’‰
Phase 2 Loss
15.6%
Lean Mass Lost
Only 21.9%
At a Glance

Pemvidutide by the Numbers

Phase 2 Weight Loss
15.6%
At 48 weeks, 2.4mg dose ยท MOMENTUM trial
Lean Mass Preserved
78.1%
Of all weight lost was fat, not muscle
Mechanism
GLP-1 + Glucagon
Reduces hunger + increases calorie burn
Form & Schedule
Weekly Injection
Subcutaneous pen, once a week
FDA Phase 3 Status
Design Agreed
End-of-Phase 2 meeting complete Nov 2024
Developer
Altimmune
Also studying MASH (liver disease)
Plain English

Why does this drug protect muscle better than others?

GLP-1 reduces appetite. Glucagon raises your metabolic rate. Together they direct your body to burn fat preferentially over muscle. One of the least-discussed side effects of GLP-1 drugs is muscle loss. When you lose weight rapidly, through any method, your body doesn't only burn fat. It also breaks down lean tissue, including muscle. With typical GLP-1 drugs, up to 40% of weight lost can come from lean mass. Pemvidutide appears to change that equation significantly.

๐Ÿง 
GLP-1 receptor activation
The same mechanism as Wegovy and Zepbound, activates receptors in your gut and brain that signal fullness, reduce appetite, and slow digestion. This is what drives the calorie reduction that leads to weight loss. Pemvidutide's GLP-1 component is calibrated to be highly potent.
๐Ÿ”ฅ
Glucagon receptor activation
Glucagon is a hormone that tells your liver to release stored energy and increases your metabolic rate, meaning your body burns more calories even at rest. In pemvidutide, this addition is believed to direct the body toward fat oxidation rather than muscle breakdown, contributing to the exceptional lean mass preservation seen in trials.
How much of total weight loss came from lean mass (muscle)?
Lower is better, you want to lose fat, not muscle.
Other GLP-1 drugs (historical reports)Up to 40%
Diet and exercise programs (historical)25-30%
Pemvidutide (Phase 2 MOMENTUM trial)21.9%
Pemvidutide in adults 60+ (sub-study)19.9%

Source: Altimmune Phase 2 MOMENTUM trial MRI sub-study, 67 subjects. Historical comparisons are from published literature, not direct comparison trials.

1

You inject it once a week

A small subcutaneous injection, similar to Wegovy. The dose starts low and increases gradually to minimize side effects. Phase 3 trials will test the optimal dosing regimen for the full population.

2

Hunger decreases, metabolism increases

The GLP-1 component reduces appetite, food cravings, and the speed of digestion. The glucagon component simultaneously raises your resting metabolic rate. Both effects work together to create a calorie deficit.

3

Your body burns fat, not muscle

The glucagon activation appears to direct your metabolism preferentially toward fat stores, which may explain why lean mass preservation was better than any other weight loss drug tested in Phase 2. This effect was even stronger in older adults, who are more vulnerable to muscle loss.

Clinical Evidence

What the Phase 2 MOMENTUM Trial Showed

15.6% weight loss at 48 weeks. Only 21.9% of weight lost was lean mass, better than every other drug in class. The Phase 2 MOMENTUM trial enrolled adults with obesity across 48 weeks at three dose levels (1.2mg, 1.8mg, 2.4mg once weekly). Results were presented at the American Diabetes Association's 84th Scientific Sessions in 2024. The body composition MRI sub-study provided some of the most important data on lean mass preservation ever published for a weight loss drug.

15.6%
Weight loss at 48 weeks
2.4mg dose ยท MOMENTUM trial
21.9%
Of weight lost was lean mass
vs up to 40% for other GLP-1 drugs
78.1%
Of weight lost was pure fat
Best in class as of Phase 2 completion
๐Ÿ’ช
Why muscle loss matters: When you lose muscle alongside fat, you're not just losing weight, you're potentially losing strength, slowing your metabolism, and making it harder to maintain weight long-term. Muscle mass also becomes increasingly important as we age. Pemvidutide's lean mass preservation was even stronger in adults over 60, where the lean loss ratio dropped to just 19.9%. An entire Phase 3 trial (VELOCITY-4) is being designed specifically around body composition and elderly patients.

Also being studied for liver disease (MASH)

Pemvidutide is also being developed for MASH (metabolic-associated steatohepatitis), a serious liver condition strongly linked to obesity. The Phase 2b IMPACT trial showed significant improvements in liver-related biomarkers at 24 weeks alongside weight loss. A Phase 3 MASH trial is planned for 2026. If both obesity and MASH indications advance to approval, pemvidutide could become one of the most versatile drugs in its class.

Where Things Stand

Pemvidutide's Road to Approval

End-of-Phase 2 FDA meeting complete. Four Phase 3 VELOCITY trials starting 2025-2026. Altimmune reached a key milestone in November 2024 when it completed its End-of-Phase 2 meeting with the FDA and got agreement on the Phase 3 design. That's the regulatory green light to move forward, and it means the Phase 3 program is clearly defined.

โœ“ Done
Phase 1, Is it safe?
Early safety studies confirmed pemvidutide was well-tolerated at multiple dose levels with a side effect profile expected for GLP-1 drugs.
โœ“ Done
Phase 2 MOMENTUM, Does it work?
48-week trial showed 15.6% weight loss and landmark lean mass preservation data. MRI sub-study provided some of the most detailed body composition data in obesity drug research. Presented at ADA 2024.
โœ“ Done
End-of-Phase 2 FDA Meeting
Completed November 2024. Altimmune and the FDA reached agreement on the Phase 3 program design, including trial size, endpoints, and duration. This is a critical regulatory milestone.
โ— Happening Now
Phase 3 VELOCITY Program Launch
Four Phase 3 trials (VELOCITY-1 through VELOCITY-4) are launching in 2025-2026. Together they'll enroll approximately 5,000 participants across 60 weeks, covering obesity, cardiovascular risk, liver fat, and elderly patients with muscle loss concerns.
Up Next
Phase 3 Results
Phase 3 results expected 2027. If successful, Altimmune would file an NDA with the FDA, targeting approval around 2027-2028.
The Four Phase 3 Trials
VELOCITY-1: Adults with obesity or overweight. Primary endpoints: body weight, waist circumference, blood lipids.
VELOCITY-2: Adults with elevated LDL cholesterol, testing both weight and cardiovascular risk reduction.
VELOCITY-3: Adults with elevated liver fat, connecting obesity and metabolic liver disease.
VELOCITY-4: Adults with obesity including elderly patients with sarcopenia, directly testing lean mass preservation and physical function.

"Dual agonists aren't all the same, the balance between the two targets matters. Pemvidutide's specific formulation is different from tirzepatide's and I think that gets glossed over. Whether that difference shows up clinically is what I'm looking for in the data."

Dr. Roynny Sanchez Gil, MD

Dr. Roynny Sanchez Gil, MD

Endocrine Surgeon ยท GLP-1 Specialist

Is It Right for You?

Who Pemvidutide Is, and Isn't, For

Especially promising for people who care about body composition, not just the number on the scale. Pemvidutide's headline story is muscle preservation, but it's also a strong weight loss drug in its own right. Here's who stands to benefit most.

โœ… Likely a strong fit

  • People who exercise regularly and want to preserve the muscle they've built
  • Adults over 50 or 60, where muscle loss during weight loss carries real health risks
  • Anyone who tried GLP-1 drugs and noticed significant muscle or strength loss
  • People with elevated liver fat or early MASH (liver disease linked to obesity)
  • People with high LDL cholesterol alongside obesity, VELOCITY-2 specifically targets this group

โš ๏ธ Things to consider

  • Still 1-2 years from approval, Wegovy and Zepbound are available today for people who need treatment now
  • 15.6% weight loss is strong but lower than Retatrutide or CagriSema, this is a trade-off for the muscle preservation benefit
  • GI side effects are expected (nausea, diarrhea during dose escalation)
  • Glucagon activation can raise blood sugar transiently, people with uncontrolled diabetes should discuss with a doctor
Side by Side

How Pemvidutide Compares

The weight loss numbers look similar to some approved drugs, but pemvidutide's differentiator is what the weight loss is made of.

Drug Weight Loss Lean Mass Lost Form Status
๐Ÿ’‰Pemvidutide
You're here
15.6% (Ph2) 21.9% โœ“ Best Weekly injection Phase 3
๐Ÿ’‰Retatrutide 24% (Ph2) Not yet reported Weekly injection Phase 3
๐Ÿ’‰CagriSema 22.7% (Ph3) Not reported Weekly injection FDA Review
๐Ÿ’‰Zepbound 21% 25-35% Weekly injection โœ“ Approved
๐Ÿ’‰Wegovy 15% 35-40% Weekly injection โœ“ Approved

Lean mass percentages for approved drugs are from observational studies and are not directly comparable to pemvidutide's controlled MRI sub-study. Phase 2 weight loss data cannot be directly compared to Phase 3 data.

Common Questions

Frequently Asked Questions

Pemvidutide (ALT-801) is a once-weekly injectable drug from Altimmune that activates two receptor types: GLP-1 (which reduces hunger) and glucagon (which increases calorie burning and appears to direct metabolism toward fat rather than muscle). Most GLP-1 drugs only activate GLP-1. The addition of glucagon activation is what researchers believe explains pemvidutide's lean mass preservation in Phase 2, only 21.9% of weight lost was lean tissue, compared to up to 40% reported with other GLP-1 drugs.
Based on the Phase 2 MOMENTUM trial data, yes, and the data comes from a rigorous MRI body composition sub-study, not just weight measurements. Of the 50 participants who received pemvidutide for 48 weeks, only 21.9% of their total weight loss came from lean mass. The lean mass preservation was even better in adults over 60, dropping to 19.9%. Historically, GLP-1 drugs have shown lean mass comprising 25-40% of weight loss in various studies. The important caveat: Phase 3 will provide much larger, more rigorous data, but the Phase 2 signal is meaningful.
In the Phase 2 MOMENTUM trial, participants receiving the 2.4mg dose (the highest tested) lost an average of 15.6% of their body weight at 48 weeks, compared to 2.2% on placebo. Lower doses also showed meaningful weight loss: 10.3% at 1.2mg and 11.2% at 1.8mg. While 15.6% is lower than CagriSema or Retatrutide, it's comparable to Wegovy, and the body composition advantage is pemvidutide's key differentiator.
MASH (metabolic-associated steatohepatitis, formerly called NASH) is a serious liver condition caused by fat buildup in the liver that leads to inflammation and scarring. It's closely linked to obesity and affects tens of millions of people. Pemvidutide's glucagon component directly targets liver fat metabolism, making it a natural candidate for MASH treatment. The Phase 2b IMPACT trial showed significant improvements in liver-related biomarkers at 24 weeks. A Phase 3 MASH trial is planned for 2026.
Altimmune completed its End-of-Phase 2 meeting with the FDA in November 2024 and received agreement on the Phase 3 design. The four VELOCITY Phase 3 trials are launching in 2025-2026. These trials run approximately 60 weeks plus data analysis and review time. If successful, FDA submission could happen around 2027, with a potential approval and commercial launch around 2027-2028. It's still a few years away.
That depends on your situation and your doctor's guidance. Wegovy and Zepbound are highly effective approved drugs available today. If muscle preservation is your primary concern and you're otherwise healthy enough to wait 2-3 years, pemvidutide could be worth watching. However, for most people dealing with obesity-related health risks right now, starting treatment today with an approved drug is likely the better choice than waiting for something that's still in trials. Clinical trials can always produce unexpected results.
Dr. Sanchez-Gil
Medically Reviewed by
Dr. Sanchez-Gil
Endocrine Surgeon