Rapamycin

Rapamycin (generic name sirolimus) is a licensed immunosuppressant that is the closest thing yet to a true anti-aging drug candidate. It reliably extends life in mice, but in people the trials are small and short, the largest trial in healthy adults missed its main goal, and the one placebo-controlled trial of the dose clinics prescribe found no benefit and more side effects in total.

Treat rapamycin as an experiment, not a supplement. If you want to try it, do so only with a knowledgeable physician, with blood monitoring, and not if you are pregnant, have an active infection or are due for surgery.

What it is

Rapamycin blocks mTOR (the mechanistic target of rapamycin), the cell's central nutrient-sensing switch. It is prescribed to stop the immune system rejecting transplanted organs. Its longevity use is off-label: it is not approved for that purpose, and that use is increasing but unmonitored. Related drugs that act on the same switch, such as everolimus, are called rapalogs. The wider family of anti-aging drug candidates is compared on Geroprotectors.

Mice: a replicated lifespan signal

In the US National Institute on Aging's Interventions Testing Program, which tests each compound at three sites in genetically diverse mice, rapamycin extended median lifespan by roughly 10–25%, depending on dose and sex, with females gaining more. The result replicated across all three sites.^[1]

People: immune signals, then a failed phase 3

The early human evidence came from small, short trials of related mTOR-blocking drugs rather than rapamycin itself: everolimus, alone or combined with an experimental drug called BEZ235. They modestly improved older adults' response to the flu vaccine and cut self-reported infections.^[2] ^[3]

The follow-up did not hold up. A 1,000-person phase 3 trial of BEZ235 found no reduction in respiratory illness: 26% of people on the drug fell ill against 25% on placebo, even though the drug again switched on antiviral gene activity.^[4]

A 2024 systematic review of 19 human studies of rapamycin and related drugs, in healthy people and people with age-related disease, found improvements in some immune, heart-and-vessel and skin measures, but no significant effect overall on muscle, hormone or brain measures. Healthy people reported no serious side effects, but people who were already ill had more infections and higher cholesterol and triglycerides.^[5]

PEARL: tolerable, but it missed its main goal

PEARL is the largest and longest trial to date of intermittent low-dose rapamycin in healthy adults. Participants took 5 mg or 10 mg a week, or placebo, for 48 weeks. Side effects were no more common than on placebo, though rapamycin users appeared to have more stomach upsets. But the trial missed its primary endpoint: visceral (belly) fat did not change.^[6]

Its bright spot — more lean mass and less pain in women on the higher dose — needs three caveats:

it came from just 8 women, and was a secondary result confined to a subgroup;
only people who finished the trial were analysed;
every author is an employee or shareholder of AgelessRx, a company that prescribes rapamycin for longevity.

PEARL also used compounded rapamycin later found to deliver only about a third as much drug as standard generic sirolimus. So it shows the schedule is tolerable more than it shows benefit, and its reassuring safety record does not carry over to standard sirolimus at the same dose.

The dose clinics prescribe: one trial, not encouraging

Some clinicians prescribe 5–6 mg a week off-label. The one placebo-controlled trial of that dose in older adults, RAPA-EX-01, gave 40 people aged 65–85 either 6 mg of standard sirolimus or placebo once a week for 13 weeks, alongside a home exercise programme. Rapamycin added no benefit: the main result was not statistically significant, and backup analyses hinted that it slightly blunted the gains from exercise. The same share of each group (85%) had side effects, but the rapamycin group logged more of them in total (99 against 63), including one pneumonia that may have been caused by the drug.^[7]

There is still no human trial with hard longevity outcomes such as disease or death. Independent trials are following: one of everolimus in insulin-resistant adults (EVERLAST) finished in mid-2026 without results yet,^[8] and a larger dosing study in people over 65 (RESTOR) runs to 2028.^[9] Dosing for healthy adults is far from worked out.

In the brain: in a dementia pilot, the drug was not detected in spinal fluid

Rapamycin has also been tried in early dementia, on the theory that it switches on autophagy, the brain's clearance of damaged proteins. In a small pilot without a placebo group in 10 older adults with mild cognitive impairment or early dementia, rapamycin at 1 mg a day for eight weeks never reached detectable levels in the fluid around the brain and did not change cognition. Markers of brain injury and tau rose rather than fell, though disease progression may explain the rise.^[10] The wider picture of autophagy-boosting drugs in brain disease is on Disabled macroautophagy.

Side effects, and who should not take it

Rapamycin's known side effects are mouth ulcers, raised blood fats, disturbed blood sugar and lowered immunity. The weekly-pulse schedule used in longevity practice is an attempt to get the mTOR effect without the immunosuppression, not a demonstrated way of avoiding it.

Not in pregnancy or during an active infection.
No live vaccines while taking it.
It slows wound healing, so stop before planned surgery.
Drug interactions. It is cleared by CYP3A4 (cytochrome P450 3A4), the liver enzyme that also handles several statins, many calcium-channel blockers, several blood thinners and most immunosuppressants. Grapefruit and berberine act on the same enzyme, so combinations can produce unexpected drug levels.
Monitoring. Blood fats, fasting glucose or HbA1c (a marker of longer-term blood sugar) and a complete blood count, periodically — the three things it most reliably disturbs.

What to do

Don't take it for longevity on your own. It is a prescription immunosuppressant whose benefit in healthy people is unproven.
If you and a physician decide to try it, know that the only placebo-controlled trial of the usual 5–6 mg weekly dose found no benefit and more side-effect events, and that the reassuring trial used a much weaker product.
Get the blood tests above, and have a pharmacist check every other medicine and supplement you take.