Rapamycin, Metformin, Senolytics: The Evidence

Three classes of drug dominate the anti-aging conversation. Here is what each one does, what the trials actually show, and why none is approved to extend human life.

Search “drugs that slow aging” and you will land on the same three names again and again: rapamycin, metformin and a family of compounds called senolytics. Each has a serious scientific case built on animal studies and early human trials. Each is also surrounded by claims that run well ahead of the data. The single most important fact to hold onto is this: not one of these drugs is approved by the United States Food and Drug Administration, or any other major regulator, to extend human lifespan or slow aging. Everything below is journalism about an unfinished science, not medical advice. People taking these compounds for longevity are using them off-label, often on thin evidence, and should be talking to a physician first.

Here is what the strongest research actually shows, drug by drug, and where the honest uncertainty lies.

Rapamycin: the most convincing animal data, the thinnest human proof

Rapamycin is the molecule that geroscientists take most seriously, and the reason is the National Institute on Aging’s Interventions Testing Program (ITP), a rigorous effort that tests compounds in genetically diverse mice across three independent labs. In a landmark 2009 paper in Nature, rapamycin extended lifespan even when started late in life, at roughly 20 months of age, the rough equivalent of human late-middle-age. Follow-up ITP work published in Aging Cell found the effect was dose- and sex-dependent, with median lifespan gains in the range of about 10 to 25 percent depending on dose and sex.

Rapamycin works by inhibiting mTOR, a cellular nutrient-sensing pathway that, when dialed down, shifts cells toward repair and recycling (autophagy) rather than growth. That mechanism is conserved across species, which is part of why the mouse results are taken so seriously.

The catch is that humans are not mice. The best canine evidence comes from the Test of Rapamycin in Aging Dogs (TRIAD), a randomized, double-blind, placebo-controlled trial run through the Dog Aging Project; it is ongoing and has not yet delivered lifespan results. In people, the most cited recent study is the PEARL trial, a 48-week randomized placebo-controlled study of low-dose, intermittent rapamycin in healthy adults. PEARL found the regimen was generally well tolerated, with no significant difference in serious adverse events versus placebo, and some signals of benefit in body composition. What it did not do, and could not do in under a year, was show that rapamycin extends human life. Rapamycin is an immunosuppressant approved for organ-transplant patients, and the classic concerns of chronic daily dosing, raised blood sugar, raised lipids and infection risk, are real even if low intermittent doses appear gentler.

Metformin and the TAME trial

Metformin is the world’s most prescribed diabetes drug, cheap and decades old, which is exactly why it became a longevity candidate. The intriguing observation came from UK records suggesting that diabetics on metformin sometimes lived as long as, or longer than, matched non-diabetics, a finding most associated with a 2014 Bannister analysis in Diabetes, Obesity and Metabolism. Metformin acts partly through AMPK activation and reduced mitochondrial energy production, pathways that overlap with caloric restriction.

That hint inspired the Targeting Aging with Metformin (TAME) trial, led by Dr. Nir Barzilai of the Albert Einstein College of Medicine. TAME is designed to randomize roughly 3,000 adults aged 65 to 79 without diabetes to metformin or placebo, tracking a composite endpoint of major age-related diseases, heart attack, stroke, heart failure, cancer, dementia and death. Its real significance is regulatory: TAME was structured with the FDA to test whether aging itself can serve as a drug target, a template for future trials. As of mid-2026 the trial has long faced funding hurdles, and metformin’s case is not airtight. A worrying 2019 study in Aging Cell by Konopka and colleagues found metformin blunted the mitochondrial gains older adults normally get from aerobic exercise, and a 2023 longevity analysis found the early survival advantage in diabetics faded over longer follow-up. The drug that launched the field may turn out to be its weakest member.

Metformin sits next to a newer class drawing intense interest for similar metabolic reasons; we covered that story in our piece on GLP-1 drugs and longevity.

Senolytics: clearing the cells that refuse to die

The third approach is conceptually different. As we age, some cells stop dividing but refuse to die, becoming “senescent” and pumping out inflammatory signals that damage surrounding tissue. Senolytics are drugs meant to selectively kill those cells. The leading combination is dasatinib (a cancer drug) plus quercetin (a plant flavonoid), abbreviated D+Q, with the natural compound fisetin as a second candidate.

The most important human evidence comes from the Mayo Clinic. A first-in-human pilot in idiopathic pulmonary fibrosis, a fatal senescence-linked lung disease, found intermittent D+Q feasible and reported improvements in physical function in 14 patients, though it was open-label with no placebo. A separate Mayo report showed D+Q reduced markers of senescent cells in patients with diabetic kidney disease, the first direct human evidence the drugs do what the theory predicts. A later randomized phase I trial in pulmonary fibrosis of just 12 people confirmed tolerability but was far too small to prove efficacy. Fisetin is being tested at Mayo in older adults with multimorbidity and elsewhere. These are tiny, early studies in sick patients, not proof that senolytics slow aging in healthy people.

How strong is the evidence, really?

Honestly: animal data is genuinely strong for rapamycin, suggestive for the others, and human data is preliminary across the board. Trials so far are short, small, or measure biomarkers rather than lifespan. None has shown that a healthy person who takes these drugs lives longer or stays healthier for years. That is a hard endpoint to study, which is precisely why the field keeps reaching for surrogate measures. Some researchers are betting instead on epigenetic clocks to measure biological age as a faster readout, though those tools are themselves unvalidated as trial endpoints.

The gap between hype and proof is where buyers get hurt. Compounding pharmacies, online clinics and a small army of biohackers now sell these drugs for longevity, and the most visible self-experimenters have made dosing themselves a public spectacle, as we explored in our profile of Bryan Johnson’s Blueprint protocol. Enthusiasm is not evidence.

FAQ

Are rapamycin, metformin or senolytics approved to slow aging? No. All three are approved or studied for other conditions, rapamycin for transplant patients, metformin for diabetes, dasatinib for leukemia. Using any of them for longevity is off-label and not endorsed by regulators. Talk to a doctor before considering it.

Which has the best evidence? Rapamycin has the most convincing animal data, repeatedly confirmed by the NIA’s Interventions Testing Program. But “best animal evidence” is not the same as proven human benefit, and human longevity trials for all three remain preliminary.

Can I just take metformin to live longer? There is no good reason to do so on current evidence. The TAME trial that would test this in non-diabetics has not delivered results, and some studies suggest metformin may interfere with the benefits of exercise. Discuss any use with your physician.