A new Ozempic rival helps patients lose fat, but keep their muscle — the holy grail for a weight-loss drug

• A new GLP-1 drug, pemvidutide, helped patients lose fat while guarding muscle like exercise does.
• The weekly injectable from Altimmune saw trial participants lose about 75% fat and 25% muscle.

It's the holy grail for a weight-loss drug: Stay strong, but lose the fat.

The drugmaker Altimmune says its new weekly injectable, pemvidutide, saw patients lose about 75% fat and only 25% muscle in results of a Phase II clinical trial the company announced on Wednesday.

That's impressive when you compare it to existing GLP-1 drugs such as Ozempic and Wegovy, which use semaglutide, or Mounjaro and Zepbound, which use tirzepatide.

On those drugs, patients can lose as much as 40% of their muscle mass. Their muscle-to-fat ratio usually still improves, but in particularly vulnerable populations, such as older adults, rapid and significant muscle loss can be a dangerous issue. This is why doctors recommend patients on weight-loss drugs do some strength training in tandem with taking their medication.

But representatives for Altimmune say its drug may mimic the beneficial effects of weightlifting without making you do the work. Pemvidutide, like tirzepatide, is a two-part drug that combines a GLP-1 drug with another in a single shot. In this case, it's boosting glucagon, a key blood-sugar-regulating hormone. While the GLP-1 reduces a person's appetite, the glucagon is thought to mimic the effects of exercise, the company says.

"There is a growing appreciation that the quality of weight loss is as important as the quantity of weight loss," Scott Harris, Altimmune's chief medical officer, said in a release. "We believe that pemvidutide, if approved, could stand out as an attractive option for weight loss and weight maintenance."

Other drugmakers are trying to solve the issue of patients losing muscle while on drugs like Ozempic

In July, Eli Lilly, which makes Zepbound and Mounjaro, acquired Versanis, a privately held, clinical-stage biopharmaceutical company. The deal was worth $1.9 billion, FierceBiotech reported.

Versanis makes a monoclonal antibody called bimagrumab, which is thought to help preserve more muscle mass, even through weight loss.

The same antibody is also being tried with semaglutide in a worldwide Phase II clinical trial run by Eli Lilly.