Published on: Aug 25, 2025
Researchers from the School of Medicine & Health Sciences determined that further testing is necessary to determine if a popular anti-aging treatment is capable of prolonging longevity in humans, according to a study published this month.
The study — led by Jacob Hands, a medical student at SMHS — could not determine that rapamycin therapy, a treatment marketed to promote longevity in humans by slowing down cellular growth that has been shown to increase the lifespan of mice, delays aging in older adults. While some doctors have recommended the drug, which has increased in popularity as an anti-aging treatment in recent years, the study posits that further testing would be appropriate to determine if rapamycin should be used on humans.
I have worked for several scientists interested in rapamycin therapy and have personally witnessed dozens of friends and relatives taking the drug, Hands said. I am unconvinced of its benefit at this point.
Rapamycin is a compound that inhibits mammalian targets of rapamycin, commonly known as mTORs, a protein that controls cell growth. Rapamycin has been found to extend the lifespan of mice by 13 percent on average, according to the National Library of Medicine. But it remains unclear if rapamycin can also slow the aging process in humans, despite being marketed as such by some doctors and online vendors.
Researchers discovered rapamycin’s anti-aging capabilities when two studies, published in 2006 and 2009, respectively, found that it increased the lifespan of both yeast and mice. Some doctors and health influencers then began touting rapamycin as an anti-aging drug, leading to the drug’s rise in popularity, although no evidence yet exists of rapamycin extending the lifespan of humans.
As part of the study, researchers assigned two groups of healthy older adults with a mean age of 80 to either an experimental or control group. The experimental group received low-dose daily rapamycin therapy, while the control group received a placebo.
Researchers used a phenotypic age calculator — a tool used to measure a patient’s biological age based on biometric data like blood quality — to find the experimental group had an average phenotypic age lower than their chronological age, meaning they appeared younger than they were supposed to be at the studies completion. Researchers were unable to establish if rapamycin was responsible for any clear benefit in the experimental group.
It’s unclear how rapamycin extends lifespan in different species, Hands said in an email. Why a mouse benefits may be unique to its biology and may not be as relevant to us.
Although rapamycin has demonstrated anti-aging effects in multiple organisms, researchers of the drug said that little is known about the potential side effects of the drug in humans and that long-term clinical trials are needed.
Thomas Weichhart, an associate professor at the Medical University of Vienna, said rapamycin has been shown to increase lifespans in all tested organisms, including yeast, worms, flies and mice, according to a study published by the Anatomical Society. Weichhart said these results could also be applicable to humans, but he said careful clinical studies are necessary before rapamycin is widely used by the public.
This remarkable consistency makes researchers hopeful that rapamycin, or related compounds, could promote healthier aging in humans as well, Weichhart said in an email.
Researchers hope rapamycin can reduce aging in humans by inhibiting mTOR complex 1, a protein complex that controls protein synthesis. Sustained mTOR activation, which can occur during aging because of factors like persistent inflammation, can cause diseases like Alzheimer’s and Parkinson’s. However, inhibiting mTOR complex 1 can prevent this, according to Weichhart.
Inhibiting mTOR can rebalance these processes, activating stress resistance and maintenance pathways that support healthier aging and increased lifespan, Weichhart said.
However, rapamycin has also been found to cause negative side effects in mice, like testicular degeneration and insulin resistance, and its effects on humans are inconclusive. Richard Miller, a professor of pathology at the University of Michigan, said researchers have been unable to determine if its lifespan-extending properties are applicable to humans and that a study on it may be prohibitively expensive.
In humans, there’s no real evidence that it does extend lifespan, Miller said. That’s why you need to take thousands of people, put them on the drug for a couple decades and then see how long we live. So that’s a very slow, very expensive study, right?
Miller also said rapamycin’s negative side effects found to be present in mice, like insulin resistance, could rapidly make humans patients’ health worse, particularly in patients with preexisting conditions like diabetes and that it’s premature to recommend rapamycin therapy.
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