Semaglutide, the active ingredient in the blockbuster diabetes and weight-loss injections Ozempic and Wegovy, has shown the first clinical signs of slowing—and even reversing—biological ageing in humans. A newly released 32-week, randomised, placebo-controlled study involving 108 adults with HIV-associated lipohypertrophy found that participants receiving the weekly GLP-1 analogue became biologically younger by an average of 3.1 years, as measured by epigenetic ageing clocks. Some organ-specific measures, including brain and inflammatory-system markers, improved by almost five years. The investigation, posted as a preprint on the medRxiv server, is the earliest human evidence that a marketed metabolic drug can turn back molecular hallmarks of ageing. Researchers compared semaglutide injections with placebo while tracking DNA-methylation patterns that correlate with chronological ageing. While weight loss and improved metabolic profiles were expected, the magnitude of the age-related molecular shift surprised investigators, suggesting the drug’s anti-inflammatory effects may extend beyond fat reduction. Because the cohort was restricted to patients with HIV-related fat redistribution—a condition linked to accelerated cellular ageing—the findings require confirmation in larger, more diverse populations. The authors and outside specialists caution that the work has not yet undergone peer review and that semaglutide’s known side-effects, as well as limited global supply, argue against off-label use for longevity. Nonetheless, the results are intensifying calls for full-scale trials in otherwise healthy adults to test whether GLP-1 therapies can safely modulate the human ageing process.