Health

Study: Drug Preserves Muscle Mass During GLP-1 Weight Loss

Is apitegromab a breakthrough solution to muscle loss in GLP-1 users or an overhyped drug that needs far more evidence?

JUN 8·Updated JUN 9

Study: Drug Preserves Muscle Mass During GLP-1 Weight Loss

Story

Above: Men lifting dumbbells during gym workout for fitness goals - stock photo. Image credit: Organic Media/Getty Images

The Facts

A phase 2 clinical trial published in Nature Medicine on Monday found that apitegromab, a monoclonal antibody that blocks the muscle-inhibiting protein myostatin, preserved 54.9% more lean mass in participants taking the weight loss drug tirzepatide compared to those on tirzepatide alone.
BBC News
Nature
The EMBRAZE trial enrolled 102 adults aged 18 to 65, who were overweight or obese, across seven U.S. sites. Participants were randomized to receive either apitegromab or a placebo alongside tirzepatide for 24 weeks.
Nature
National Institutes of Health (NIH)
Lean mass accounted for 14.6% of total weight loss in the apitegromab group, compared with 30.2% in the placebo group. Overall weight loss was similar between the two groups at roughly 12-13% of body weight.
Scholar Rock
ChosunBiz
Studies suggest that 25 to 40% of total weight loss from GLP-1 drugs such as Wegovy and Mounjaro involves lean body mass rather than fat. Lean mass includes muscle, organs and blood, and is linked to physical strength and a lower risk of type 2 diabetes.
Science News
Guardian
The incidence of adverse events was 39% in the apitegromab group and 36% in the placebo group. No serious adverse events or discontinuations were attributed to apitegromab, and no deaths occurred during the trial, according to apitegromab maker Scholar Rock.
Scholar Rock
ChosunBiz
Apitegromab is also under FDA review for spinal muscular atrophy, with a decision date set for Sept. 30. Scholar Rock, which funded the EMBRAZE obesity trial, is reportedly developing a subcutaneous self-injection version of the drug.
BBC News
SMA News Today

Sources Split

LEFT

CENTER

RIGHT

ESTAB
CRIT

CENTER

PRO
ESTAB

The Spin

Narrative A

Apitegromab is a genuine breakthrough for GLP-1 users — the Phase 2 EMBRAZE trial showed it preserved 55% more lean mass than tirzepatide alone, cutting muscle loss nearly in half while delivering comparable fat reduction. Muscle mass drives metabolism, physical strength and long-term health, so losing 30% of weight as lean tissue is a serious problem that demands a medical solution. This drug directly addresses that gap and points toward a smarter, higher-quality approach to obesity treatment.

ChosunBiz

Scholar Rock

Narrative B

Apitegromab preserved lean mass on paper, but nobody actually knows if that translates to real health benefits. The gains in grip and leg strength were minor, the trial ran only 24 weeks and enrolled just 102 mostly female participants. For most GLP-1 users, losing some lean mass doesn't hurt function and people actually move better after shedding weight. Larger, longer, more diverse trials are needed before adding another unapproved IV drug to an already complex treatment regimen.

ChosunBiz

Guardian

Science News