A Glimpse of Promise for Losing Fat and Keeping Muscle

Regeneron announced tantalizing results for the combination of trevogrumab with semaglutide for losing fat while preserving muscle. With the combination of these two drugs, it appears that individuals might lose more fat mass and less muscle mass than with semaglutide alone. In short, the promise is for a better quality of weight loss, leaving people with better body composition.

George Yancopoulos is President and Chief Scientific Officer at Regeneron. He explains why this progress may lead to improved health for people living with obesity:

“Recent advancements have resulted in patients being able to lose significant amounts of body weight. Unfortunately, this weight loss comes at the cost of muscle loss, and we know muscle is important to overall health.”

A Phase 2 Study

These are phase 2 data for a product that has a long way to go before we can be confident it will be safe and effective in clinical use. They are topline results for a study of 599 patients randomized to four different groups: semaglutide alone, semaglutide plus low-dose trevogrumab, semaglutide plus high-dose trevogrumab, and semaglutide plus trevogrumab and garatosmab.

Some loss of muscle mass is normal when a person is losing fat. It is not at all unusual for about 35% of a person’s weight loss to be from losing muscle. That is what happened in this study with semaglutide alone. But with the addition of the higher dose trevogrumab, people lost a little more weight overall and only 17% of that weight loss was from muscle loss.

In other words, it cut the typical amount of muscle loss in half.

Much More to Learn

We have a whole lot more to learn about this approach to obesity treatment. These are only topline results and we will get more detail later this year. With a detailed publication will come the all important peer review.

In addition, at the ADA Scientific Sessions in two weeks we can look forward to detailed presentations of phase 2 results of bimagrumab and semaglutide. Two years ago, Lilly agreed to pay as much as $1.9 billion for the rights to bimagrumab, which is a drug with a mechanism of action similar to trevogrumab. We will learn much from this.

But even so, FDA has said that these new agents will get close scrutiny. It’s likely that companies will have to prove that the health outcomes are better with this different approach to weight loss in treating obesity. It will be a wild ride.

Click here, here, and here for more on this news. For a bit more background on this approach, click here.

Studies of Legs, sketches by Leonardo da Vinci / WikiArt

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June 5, 2025