Drugmakers test compounds to limit muscle loss during weight reduction

Cambrian Biotech released early results from the first human study of ATX-304, a once-daily pill designed to raise resting metabolic rate. In a safety trial of 23 adults with obesity and prediabetes, participants showed an increase in resting metabolic rate and lost about 5 percent of visceral fat.

The company said the drug mimics the metabolic effects of running 5-10 kilometers daily without changing appetite or digestion. A larger mid-stage trial is scheduled to report results at the end of 2027.

Repurposed compounds advance Eli Lilly acquired bimagrumab from Versanis in 2023 for $1.9 billion after earlier trials for age-related muscle loss did not meet goals. In a later study of more than 500 people with obesity, patients who added bimagrumab to an Ozempic regimen lost more than 90 percent of body weight as fat.

AstraZeneca purchased SPX-001 for roughly $300 million in 2025. Novo Nordisk is testing CagriSema, a combination of semaglutide and cagrilintide, which produced 67 percent fat loss in an earlier obesity study.

Market questions remain Daniel Drucker, an endocrinologist at the University of Toronto, said no drug has yet demonstrated clinically meaningful outcomes such as fewer falls or faster walking speed in older adults. He noted that physicians are unlikely to prescribe medicines solely for changes in body composition.

Lloyd Klickstein, founder of Versanis, said the field is shifting focus from the amount of weight lost to the proportion of fat versus lean mass retained. Larger trials will determine whether any of the candidates reach regulatory review or gain coverage from insurers.