Rapamycin

A transplant-rejection drug that became the longevity field's single most-hyped molecule after it extended lifespan in every organism tested — the only drug to do so reproducibly in mammals. Longevity clinics now prescribe it off-label, typically as intermittent low doses.

Rapamycin binds a protein inside the cell, and that complex then inhibits mTOR — the master switch that tells a cell whether conditions are good enough to grow and build, or lean enough to conserve and recycle. Blocking it flips cells toward autophagy, the self-cleaning process that clears damaged components. That single lever is why the same molecule is an immunosuppressant used to stop organ rejection, a cancer drug, and the most-cited candidate longevity compound: growth signalling, immune activation and cellular ageing all run through it. The longevity hypothesis is that intermittent partial inhibition captures the cleaning without the immune suppression, which is plausible and not established in people.

Mouse lifespan extension is real and replicated (ITP, multiple labs, both sexes). Human longevity evidence: none yet — the PEARL trial was small and mostly null, and the dog (TRIAD) and further human trials are still running. Everything a longevity clinic tells you is extrapolation from mice plus mechanism. That does not make it wrong; it makes it unproven.

• Approved for preventing kidney-transplant rejection and for lymphangioleiomyomatosis. It is NOT an approved cancer treatment — related mTOR inhibitors such as everolimus and temsirolimus carry the oncology indications, not sirolimus itself.
• Unusually strong and replicated lifespan evidence in genetically heterogeneous mice, including when started in late life. Effects still vary by species, sex, genotype and regimen, and other compounds have also reproducibly extended mouse lifespan — so it is among the strongest animal evidence in the field rather than the only such result.
• In humans the closest thing to a positive ageing signal is a set of small trials of a related mTOR inhibitor that improved vaccine response in older adults — an immune-ageing endpoint, not lifespan.
• PEARL, the randomised placebo-controlled trial of low-dose intermittent rapamycin in healthy adults, enrolled 129 and analysed 114 completers. Its primary endpoint was visceral fat and it did NOT significantly improve. The benefits reported were exploratory and sex-specific, and the compounded drug delivered roughly a third of the exposure of the commercial formulation. It cannot support a human longevity claim: it did not measure lifespan and it missed its primary endpoint.
• There is no human trial demonstrating extended lifespan or healthspan, and the off-label longevity dosing schedules in circulation are extrapolated from mouse work rather than derived from human data.

Long half-life, roughly 60 hours, which is what makes weekly intermittent dosing plausible and is the basis of most longevity protocols. Metabolised by CYP3A4 and transported by P-glycoprotein, which gives it a large and clinically serious interaction list. Blood levels vary substantially between individuals on the same dose, which is why transplant medicine monitors levels directly rather than assuming.

Immunosuppression is the mechanism, so infections are the risk — mouth ulcers are the common one, and intermittent dosing is an attempt to dodge this, not proof it does. Metabolic effects (glucose, lipids) at continuous doses. Long-term intermittent-use safety in healthy humans is simply unknown. Grey-market powder purity is its own problem for a drug this potent.

• Anyone with an active infection, or a history of serious recurrent infection
• Anyone with a planned surgery or dental procedure, because wound healing is impaired
• Anyone pregnant, breastfeeding or trying to conceive
• Anyone with poorly controlled lipids or diabetes
• Anyone unable to get blood monitoring and clinician oversight — this is not a self-directed compound

• Strong CYP3A4 inhibitors — including grapefruit juice, ketoconazole, clarithromycin and some antivirals — can raise levels sharply and dangerously.
• Strong CYP3A4 inducers such as rifampicin, carbamazepine and St John's wort can drop levels enough to fail.
• Live vaccines should be avoided on an immunosuppressant, and other vaccines may respond less well.
• Other immunosuppressants, including ciclosporin, with which it has a specific documented interaction.
• Any planned surgery — impaired wound healing means the surgeon must know.

• Lipids — rapamycin raises triglycerides and cholesterol, commonly and sometimes markedly.
• Fasting glucose and HbA1c, since it can impair glucose tolerance.
• Full blood count, for the drops in white cells and platelets.
• Kidney and liver function.
• Mouth ulceration, which is its own labelled adverse effect and the most common dose-limiting nuisance — not a sign of infection.
• Infection, taken more seriously than usual on an immunosuppressant: the label warns about serious and opportunistic infections, and about progressive multifocal leukoencephalopathy.
• The label also carries lymphoma and other malignancies, interstitial lung disease and non-infectious pneumonitis, blood-count suppression, protein in the urine, fluid accumulation and effects on fertility. These are the risks that matter most and they are not metabolic laboratory changes.
• Wound healing, which is impaired — genuinely important before any planned surgery or dental work.

mTOR inhibition lifts as the drug clears, and given the long half-life that takes one to two weeks. Lipid and glucose changes generally reverse and mouth ulcers resolve. There is no withdrawal syndrome, but stopping does not automatically resolve a serious adverse reaction — infection, pneumonitis, low blood counts, effusions or impaired wound healing all need clinician management rather than time. Transplant recipients must never stop without their team, because rejection is the immediate consequence.

US: prescription-only (not scheduled). Off-label prescribing is legal; longevity clinics operate in that space.

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

• Paclitaxel-coated versus sirolimus-coated balloon angioplasty for coronary artery disease: A systematic review and meta-analysis
  Catheter Cardiovasc Interv, 2024
• Targeting ageing with rapamycin and its derivatives in humans: a systematic review
  Lancet Healthy Longev, 2024
• Efficacy and safety of sirolimus in the treatment of vascular anomalies: A systematic review
  J Vasc Surg, 2020

• Rapamycin for longevity: the pros, the cons, and future perspectivesFront Aging · 2025
• Evaluation of off-label rapamycin use to promote healthspan in 333 adultsGeroscience · 2023
• Rapamycin not dietary restriction improves resilience against pathogens: a meta-analysisGeroscience · 2023
• Rapamycin: A Bacteria-Derived Immunosuppressant That Has Anti-atherosclerotic Effects and Its Clinical ApplicationFront Pharmacol · 2018
• Why Is Rapamycin Not a Rapalog?Gerontology · 2023
• The effect of rapamycin treatment on mouse ovarian follicle development in dehydroepiandrosterone-induced polycystic ovary syndrome mouse modelZygote · 2024
• Cancer prevention with rapamycinOncotarget · 2023
• A mixed blessing for liver transplantation patients - RapamycinHepatobiliary Pancreat Dis Int · 2023
• Rapamycin golden jubilee and still the miraculous drug: a potent immunosuppressant, antitumor, rejuvenative agent, and potential contributor in COVID-19 treatmentBioresour Bioprocess · 2022
• Rapamycin Does Not Compromise Exercise-Induced Muscular Adaptations in Female MiceAging Cell · 2025
• Rapamycin: an anti-cancer immunosuppressant?Crit Rev Oncol Hematol · 2005
• Molecular and therapeutic insights of rapamycin: a multi-faceted drug from Streptomyces hygroscopicusMol Biol Rep · 2023