The co-founder of Regeneron has warned that blockbuster weight-loss drugs could cause “more harm than good” unless the rapid muscle loss associated with the treatments is solved, as the US biotech pushes ahead with trials of muscle-preserving medicines.

Clinical studies suggest that patients treated with the new class of weight- loss drugs, known as GLP-1s, lose muscle at far faster rates than people losing weight from diet or exercise, exposing them to health problems, said George Yancopoulos, who also serves as Regeneron’s chief scientific officer.

For the two in every five patients who discontinue the treatments within a year, according to a 2024 JAMA study, this means that they are likely to rebound to their original weight with less muscle and a higher body fat percentage, “adding insult to injury”, said Yancopoulos.