Does rapamycin help people live longer in good health?

Rapamycin inhibits a protein called mTOR, a central switch in ageing processes. In mouse studies this led to a substantial extension of lifespan: female mice lived an average of 249 days longer, male mice 154 days. That is one of the most robust anti-ageing results ever measured in mammals.

In humans the signals are cautiously positive, but not yet definitive. A systematic review of 19 clinical studies showed improvements in measurable ageing parameters of the immune system, the cardiovascular system and the skin. A concrete example: a related compound improved the response to the flu vaccine in older participants, suggesting a more youthful immune response. No effect was found on muscle strength, the nervous system or hormone levels.

The safety picture is nuanced. In patients with age-related diseases, more infections occurred, and blood lipid values (cholesterol, LDL and triglycerides) rose. In healthy participants no serious adverse effects were reported, but long-term data in healthy people are still largely lacking. Effects on the lungs, kidneys, digestive system and reproduction have barely been studied in humans.

Clinical trials are now under way that specifically examine age-related diseases. In mice it has also been shown that rapamycin can slow ovarian ageing through a cellular clean-up mechanism, opening a new biological avenue, but evidence in humans is still completely absent there. Larger and longer trials in humans will need to determine whether the promise from animal research is truly fulfilled.