Rapamycin: revision 1 to 2 — Future Human Wiki

Revision 1

Revision 2

categories: ["longevity"]

tags: ["mtor", "aging", "drug repurposing", "autophagy", "immunosenescence", "clinical trials"]

summary: "A macrolide immunosuppressant that inhibits the mTOR growth pathway and extends lifespan across several laboratory species, with no confirmed effect on human aging."

summary: "A macrolide immunosuppressant that inhibits the mTOR growth pathway and extends lifespan across several laboratory species, with no confirmed effect on human aging."

updated: "2026-07-28"

updated: "2026-10-29"

humanEvidence: "No human trial has tested lifespan or healthspan; low-dose rapalogs improved influenza vaccine response in older adults, a phase 3 respiratory-illness trial failed, and every lifespan result is from mice and other laboratory species."

humanEvidence: "No human trial has tested lifespan or healthspan; low-dose rapalogs improved influenza vaccine response in older adults, a phase 3 respiratory-illness trial failed, and every lifespan result is from mice and other laboratory species."

access: "Approved as sirolimus for transplant rejection and available as a generic; longevity use is off-label prescribing by a minority of physicians, at doses and schedules no regulator has evaluated."

access: "Approved as sirolimus for transplant rejection and available as a generic; longevity use is off-label prescribing by a minority of physicians, at doses and schedules no regulator has evaluated."

reversibility: "reversible"

```

**Rapamycin** is a bacterial macrolide, marketed as sirolimus, that inhibits the mechanistic target

of rapamycin (mTOR) — the kinase complex through which cells decide whether conditions favour growth

of rapamycin (mTOR), the kinase complex through which cells decide whether conditions favour growth

or conservation. It is one of the few compounds shown to extend lifespan in yeast, nematodes, flies,

or conservation. It is one of the few compounds shown to extend lifespan in yeast, nematodes, flies

and mice, and the most reproducible positive result in the US National Institute on Aging's

and mice, and it is the most reproducible positive result in the US National Institute on Aging's

[[interventions-testing-program|Interventions Testing Program]]. Whether it does anything for human aging is unknown: the human trials run so far

[[interventions-testing-program|Interventions Testing Program]]. Whether it does anything for human

have tested immune and functional surrogates in small populations, and the one large randomized trial

aging is unknown. The human trials run so far have tested immune and functional surrogates in small

of a related compound failed its primary endpoint.

populations, and the one large randomized trial of a related compound failed its primary endpoint.

## How it works

mTOR sits at the centre of nutrient sensing. As part of complex 1 (mTORC1) it integrates amino-acid

availability, growth-factor signalling, and cellular energy state, and when those inputs are

availability, growth-factor signalling and cellular energy state. When those inputs are favourable,

favourable it drives protein synthesis through S6 kinase and 4E-BP1, promotes ribosome biogenesis,

it drives protein synthesis through S6 kinase and 4E-BP1, promotes ribosome biogenesis and

and suppresses [[autophagy]]. Rapamycin does not bind mTOR directly. It first binds the small protein

suppresses [[autophagy]]. Rapamycin does not bind mTOR directly. It first binds the small protein

FKBP12, and the resulting complex docks onto mTORC1 and allosterically restricts its activity.

FKBP12, and the resulting complex docks onto mTORC1 and restricts its activity allosterically.

Inhibiting mTORC1 therefore shifts a cell from building to recycling. Autophagic flux rises, damaged

organelles and aggregated proteins are degraded, and the burden on the

[[proteostasis|protein quality-control system]] falls. This is the same axis that

[[proteostasis|protein quality-control system]] falls. [[caloric-restriction]] engages the same axis

[[caloric-restriction]] engages nutritionally, and the overlap is the main reason mTOR inhibition is

through diet, and that overlap is the main reason mTOR inhibition is treated as a pharmacological

treated as a pharmacological approximation of dietary restriction rather than an independent

approximation of dietary restriction and not as an independent mechanism.

mechanism.

The complication is mTORC2. Acute rapamycin spares it, but chronic exposure disrupts its assembly in

some tissues, and mTORC2 inhibition is associated with insulin resistance and glucose

intolerance.[^lamming2012] Much of the current interest in intermittent dosing, and in

mTORC1-selective inhibitors built to avoid touching complex 2 at all, follows from this single

mTORC1-selective inhibitors built to leave complex 2 untouched, follows from this one

pharmacological fact.

> [!key] Why mTOR keeps appearing

> Nearly every intervention that reliably extends lifespan in a model organism (dietary restriction,

> reduced growth-hormone signalling, several genetic mutants including the long-lived

> [[cynthia-kenyon|daf-2 nematodes]]) converges on reduced mTORC1 output and

> [[cynthia-kenyon|daf-2 nematodes]]) converges on reduced mTORC1 output and increased autophagy.

> increased autophagy. Rapamycin is the most direct available way to hit that node with a drug.

> Rapamycin is the most direct available way to hit that node with a drug.

## Development history

## Evidence in animals

The mouse result is unusually robust. Rapamycin extended median and maximal lifespan in the ITP even

The mouse result is unusually robust. In the ITP, rapamycin extended median and maximal lifespan

when treatment began at an age equivalent to human late middle age,[^harrison2009] and the effect has

even when treatment began at an age equivalent to human late middle age,[^harrison2009] and the

been replicated across ITP cohorts and sites — a standard the field rarely meets. Higher doses

effect has been replicated across ITP cohorts and sites, a standard the field rarely meets. Higher

produce larger effects, with a sex difference that has never been fully explained: females generally

doses produce larger effects, and females generally respond more strongly, a sex difference that has

show a larger response.[^miller2014]

never been fully explained.[^miller2014]

Lifespan is not the same as [[healthspan]]. Treated mice show delayed decline in several tissues,

including reduced accumulation of [[cellular-senescence|senescent cells]] and better maintenance of

immune and cognitive function, but other age-related pathologies proceed unchanged, and rapamycin

immune and cognitive function, but other age-related pathologies proceed unchanged. Rapamycin does

does not produce the uniform rejuvenation across the [[hallmarks-of-aging]] that popular accounts

not produce the uniform rejuvenation across the [[hallmarks-of-aging]] that popular accounts imply.

imply. Work in companion dogs, where the Dog Aging Project's randomized trial tests cardiac and

The most informative test underway outside the laboratory is in companion dogs, where the Dog Aging

cognitive outcomes over years, is the most informative non-laboratory test underway; an earlier

Project's randomized trial tests cardiac and cognitive outcomes over years. An earlier ten-week pilot

ten-week pilot reported improved echocardiographic measures, and the programme's funding was

reported improved echocardiographic measures, and the programme's funding was disrupted in 2024. A separate

disrupted in 2024. A separate commercial effort, [[loyal]], pursues canine lifespan drugs through

commercial effort, [[loyal]], is pursuing canine lifespan drugs with other mechanisms through the

the veterinary regulator on other mechanisms. In common marmosets, daily dosing has been reported as well tolerated without an

veterinary regulator. In common marmosets, daily dosing has been reported as well tolerated, with no

established lifespan effect.

## Human evidence

No trial has tested whether rapamycin changes how long people live or how long they stay healthy.

What exists falls into three groups.

The human evidence that exists falls into three groups.

The first is decades of transplant experience, which establishes the safety profile at

immunosuppressive doses: stomatitis and mouth ulcers, raised blood lipids, impaired glucose

handling, delayed wound healing, oedema, and increased infection risk. These are the doses geroscience

handling, delayed wound healing, oedema and increased infection risk. Geroscience does not propose

does not propose to use.

to use these doses.

The second is immune-function work at low or intermittent doses. Rapalog treatment improved influenza

The second is immune-function work at low or intermittent doses. Rapalog treatment improved

vaccine responses in older adults[^mannick2014] and, in a follow-up combination study, was associated

influenza vaccine responses in older adults[^mannick2014] and, in a follow-up combination study, was

with fewer reported respiratory infections. This produced the field's most cited paradox: a drug

associated with fewer reported respiratory infections. Those results gave the field its most cited

classed as an immunosuppressant appearing to improve some aspects of immune function in the old,

paradox: a drug classed as an immunosuppressant appeared to improve some aspects of immune function

plausibly by reducing the accumulation of exhausted and senescent lymphocytes that also drives

in the old, plausibly by reducing the accumulation of exhausted and senescent lymphocytes that also

[[inflammaging]]. The subsequent phase 3 of RTB101 failed, which is the strongest single piece of

drives [[inflammaging]]. The later phase 3 trial of RTB101 failed, the strongest single piece of

negative human evidence about the strategy.

The third is the PEARL trial, a decentralized, placebo-controlled study of weekly rapamycin in

healthy adults over 48 weeks. It reported no serious adverse events and a small number of favourable

secondary measures, with most prespecified outcomes unchanged. It was not designed or powered to

secondary measures, with most prespecified outcomes unchanged. It was neither designed nor powered

detect a change in aging.

to detect a change in aging.

> [!caution] Off-label use runs ahead of evidence

> Rapamycin is prescribed off-label for longevity by a minority of physicians and taken by a

> A minority of physicians prescribe rapamycin off-label for longevity, and a self-selected

> self-selected community of users. Surveys of that population report a tolerable side-effect profile

> community of users takes it. Surveys of that population report a tolerable side-effect profile at

> at intermittent doses, but self-reported outcomes from people who chose the drug cannot establish

> intermittent doses, but self-reported outcomes from people who chose the drug cannot establish

> benefit, and no dose, schedule, or monitoring standard has been validated for healthy adults.

> benefit, and no dose, schedule or monitoring standard has been validated for healthy adults.

## Limitations

The dose–schedule question is unresolved. Animal lifespan data come from continuous exposure at

The question of dose and schedule is unresolved. Animal lifespan data come from continuous exposure

concentrations that would be immunosuppressive in humans; the human longevity community uses weekly

at concentrations that would be immunosuppressive in humans, while the human longevity community

pulses chosen largely by inference from mTORC2 pharmacology. Nobody knows whether the pulsed schedule

uses weekly pulses chosen largely by inference from mTORC2 pharmacology. Nobody knows whether the

retains the effect that the continuous schedule produced in mice.

pulsed schedule keeps the effect that the continuous schedule produced in mice.

The endpoint question is worse. Because no regulator accepts a measure of

The endpoint question is harder still. No regulator accepts a measure of

[[aging-biomarkers|biological aging]] as a surrogate, a trial would have to be powered on disease

[[aging-biomarkers|biological aging]] as a surrogate, so a trial would have to be powered on disease

events over years. A movement in an [[epigenetic-clock]] reading or in a

events over years. A shift in an [[epigenetic-clock]] reading or in a

[[biological-age|composite age estimate]] is not evidence of clinical benefit. Rapamycin is also

generic, so no company has a commercial reason to fund such a trial — the same structural problem

generic, so no company has a commercial reason to fund such a trial. The same structural problem has

that has stalled [[metformin|the TAME trial]], which [[nir-barzilai]] has spent more than a decade

stalled [[metformin|the TAME trial]], which [[nir-barzilai]] has spent more than a decade trying to

trying to finance, and the reason the [[longevity-dividend]] remains an argument for research rather

finance, and it is why the [[longevity-dividend]] remains an argument for research and not a

than a description of an available drug.

description of an available drug.

## Outlook

Two lines could break the impasse. Bi-steric and otherwise mTORC1-selective inhibitors, designed to

Two lines of work could break the impasse. Bi-steric and other mTORC1-selective inhibitors, designed

leave complex 2 alone, would remove the metabolic penalty that limits chronic dosing and would test

to leave complex 2 alone, would remove the metabolic penalty that limits chronic dosing and would

whether the metabolic side effects and the geroprotective effect are separable. Narrow indications

test whether the metabolic side effects can be separated from the geroprotective effect. Narrow

with measurable endpoints, among them vaccine response, periodontal disease,

indications with measurable endpoints, among them vaccine response, periodontal disease,

[[reproductive-longevity|ovarian reserve]], and age-related cardiac decline, offer trials short

[[reproductive-longevity|ovarian reserve]] and age-related cardiac decline, offer trials short

enough to run and specific enough to interpret.

Until one of those produces a positive controlled result, rapamycin occupies an awkward position: the

Until one of those produces a positive controlled result, rapamycin sits in an awkward position. It

best animal evidence in [[geroscience-hypothesis|geroscience]], a plausible mechanism converging with

has the best animal evidence in [[geroscience-hypothesis|geroscience]] and a plausible mechanism

[[senolytics]] and dietary restriction on shared damage pathways, and nothing in humans that would

that converges with [[senolytics]] and dietary restriction on shared damage pathways. It has nothing

justify recommending it to a healthy person over the interventions with actual outcome data, starting

in humans that would justify recommending it to a healthy person over interventions with actual

with [[exercise-and-aging|exercise]].

outcome data, starting with [[exercise-and-aging|exercise]].

## See also