Rapamycin

Rapamycin, approved as sirolimus, is an immune-suppressing drug that extended lifespan in mice and is now prescribed off-label by some doctors in the hope it does the same in people. It acts by inhibiting mTOR, the pathway that tells a cell whether to grow or to recycle.

The mouse result is unusually solid for this field. In 2009, Harrison and colleagues reported in Nature that rapamycin begun at 600 days of age — late in a mouse life — raised the age at 90 percent mortality by 14 percent in females and 9 percent in males, and that the effect appeared at three independent test sites in genetically mixed mice.

What exists in humans is much thinner. A 48-week randomised, placebo-controlled trial in healthy adults, published in 2025, found adverse events no more common on the drug than on placebo. Its primary measure, visceral fat, did not change. Some secondary and subgroup measures did.

The word “off-label” is doing real work here. Sirolimus is an approved drug, but it is approved for suppressing the immune system after a transplant, not for aging. Prescribing it to a healthy person for longevity is a use no regulator has evaluated, and a 2025 review concluded that the human data have yet to establish that rapamycin can delay aging in healthy older adults.