What do we know about rapamycin as an anti-ageing agent in humans?

Rapamycin robustly extends lifespan in mice, and is the first agent shown to do so in a mammal in both sexes. Whether this represents genuine slowing of ageing or is largely cancer suppression (the leading cause of death in the mouse strains used) remains unclear.

In humans, the results are mixed and limited. A systematic review of 19 studies found improvements in ageing-related parameters of the immune system, the cardiovascular system, and the skin. No effects were found for hormones, muscles, or the nervous system. For the lungs, kidneys, digestive system, and reproduction, there is simply no human research at all.

For the skin, there is one small randomised trial showing that topically applied rapamycin reduces signs of cellular ageing in the skin and improves skin structure. However, more than half of the 36 participants dropped out, which substantially limits the reliability of that outcome.

Safety is a serious concern. No serious adverse effects were reported in healthy participants. In people with ageing-related diseases, participants experienced more frequent infections and showed rises in cholesterol and triglyceride levels. These are real risks, particularly with long-term use. More selective variants that inhibit only a specific component of the mTOR pathway (mTORC1) are under development to reduce those side effects.

Long-term data in humans are entirely absent. Recent clinical trials are promising enough to justify further research, but not yet convincing enough to recommend rapamycin as an anti-ageing treatment. Excessive mTOR activity is associated with accelerated ageing, cancer, and neurological diseases, which supports the theoretical basis for inhibiting it. However, that mechanistic argument does not reduce the clinical uncertainty in humans.