Researchers have discovered a muscle-targeted therapy that could help protect muscle during weight loss treatment. The study suggests that taking an additional medication with weight loss injections may reduce the risk of muscle loss, a growing concern among users of popular weight loss drugs.
Study details
For the research, a muscle-targeted therapy called apitegromab was tested to compare its effects on current weight loss injection users. Apitegromab is an antibody that stops the activation of myostatin, a protein that regulates muscle mass. If myostatin is activated, it can inhibit muscle growth, potentially leading to fragility and metabolic issues if left untreated.
Previous studies have found that the absence of this gene is associated with increased muscle strength and mass. To see how this antibody would work on weight loss injection users, researchers examined data from 102 adults taking weekly injections of Mounjaro, also known as tirzepatide.
Results
For the study, half of the group was given apitegromab alongside the weight loss injection, while the other half received a placebo. Both groups saw similar overall weight loss. However, those who took apitegromab lost significantly less lean mass — about 1.9 kg less — over six months compared to those who took the placebo.
The study, led by experts from AdventHealth Translational Research Institute in the US, found that lean mass accounted for 14.6% of total weight loss in the apitegromab group. According to the phase two study published in Nature Medicine, this is almost half of the lean mass weight loss in the placebo group, which was 30.2%.
Expert commentary
While the findings seem promising, the researchers have called for more work to confirm their findings on a larger scale. However, they stated that the study demonstrates "clinical proof of concept for a highly selective anti-myostatin antibody to preserve lean mass with tirzepatide therapy."
Dr Marie Spreckley from the University of Cambridge commented: "These findings suggest that apitegromab may improve the composition of weight loss by preserving lean mass while maintaining similar overall weight reduction. This is an important area of research because substantial weight loss, whether achieved through medication, dietary interventions or bariatric surgery, is often accompanied by some loss of lean mass."
She added: "Strategies that help preserve lean mass while maintaining the benefits of weight reduction are of considerable interest, but whether they improve longer-term health outcomes remains to be established. Importantly, although apitegromab preserved lean mass, the study did not demonstrate clear improvements in physical function or cardiometabolic outcomes over the 24-week treatment period. Preserving lean mass is biologically plausible and potentially beneficial, but larger and longer studies will be needed to determine whether these changes translate into meaningful improvements in strength, physical function, quality of life, or long-term health outcomes."
