Drug apitegromab may reduce lean tissue loss in slimming jab users
A small trial suggests the monoclonal antibody apitegromab can help retain lean body mass when used alongside the slimming drug tirzepatide. Researchers in the US randomly divided 102 participants into two groups, with 51 receiving apitegromab and tirzepatide, and the other 51 receiving a placebo and tirzepatide. After 24 weeks, total weight loss was similar between the groups, but those given apitegromab lost an average of 1.6kg of lean mass, compared with 3.5kg in the placebo group. The study found a 55% greater retention of lean mass relative to placebo. Apitegromab works by blocking myostatin, a protein that inhibits muscle growth. Experts described the findings as important but called for far larger and longer trials to check safety and health benefits. The trial was funded by Scholar Rock, the producer of apitegromab, and published in Nature Medicine.
What’s reported
GLP-1 based slimming jabs such as Wegovy and Mounjaro can lead to loss of lean body mass, with studies suggesting 25-40% of total weight loss is lean mass.
The trial involved 102 participants, split into two groups of 51.
The drug apitegromab is a monoclonal antibody that blocks myostatin.
After 24 weeks, the apitegromab group lost 1.6kg of lean mass (14.6% of total weight loss), while the placebo group lost 3.5kg of lean mass.
This equates to a 55% greater retention of lean mass in the apitegromab group.
Side effects were similar between the groups, with most deemed mild.
The study had limitations: most participants were women, the sample size was small, and the duration was short.
Prof Alexander Miras of Ulster University said the findings are very important.
Prof Naveed Sattar of the University of Glasgow said larger, longer trials are needed to check safety and whether the retention of lean mass benefits health or function.
Open questions
Whether the retention of lean mass leads to improved health, physical function, or ability to move. Long-term safety and efficacy of apitegromab remain uncertain.
Key figures
Prof Alexander Miras, obesity expert at Ulster University
Prof Naveed Sattar, cardiometabolic medicine expert at the University of Glasgow
Researchers in the US (unnamed in the article)
Scholar Rock, the producer of apitegromab
Sources: The Guardian
