Rapamycin is being studied to see if it can slow down age-related diseases in humans

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A clinical trial is starting to test a drug taken by many so-called longevity enthusiasts. NPR's Allison Aubrey explains why a dentist is leading the research.

ALLISON AUBREY, BYLINE: A few years back, a scientist named Matt Kaeberlein developed a pain in his shoulder that was diagnosed as a frozen shoulder.

MATT KAEBERLEIN: It was really bad. I couldn't sleep, couldn't go throw a ball with my kid.

AUBREY: His doctor recommended physical therapy and told him it may take a year to get better.

KAEBERLEIN: And I was like, I can't do this for another year. Then I thought to myself, I know a drug that is really good at knocking down age-related inflammation. I wonder if it'll work.

AUBREY: Kaeberlein is a biologist who co-founded a project to test the drug rapamycin in dogs. It's been shown to extend lifespan in lab animals, and he knew some longevity experts taking it experimentally. Though he was a bit skeptical it could help his shoulder, he decided to try it.

KAEBERLEIN: It worked. And I'm not kidding you. Within 10 weeks, it was 95% range of motion back, and pain was completely gone. And it hasn't come back.

AUBREY: Rapamycin was first approved by the FDA for transplant patients in the 1990s. At high doses, it suppresses the immune system. At low doses, it seems to help tamp down inflammation. It works by inhibiting a pathway in the body called mTOR, which appears to be key to healthy aging.

KAEBERLEIN: I can't rule out placebo effect, but, you know, I'm pretty sure it was real.

AUBREY: Rapamycin is not approved for pain or anti-aging, though doctors can prescribe it off-label. Kaeberlein has surveyed about 300 people who take low doses, and many report benefits. But anecdotes are no replacement for science, and that's where the dentist at the University of Washington comes in. Dr. Jonathan An has FDA approval to test rapamycin in patients with gum disease, a common condition that tends to accelerate with age.

JONATHAN AN: So we're hoping that rapamycin can target the underlying cause, which is aging, to improve patients that have periodontal disease.

AUBREY: There's already some evidence from transplant patients that the drug may help improve oral health, and as part of the study, An will also measure changes in participants' microbiomes and their biological clocks. The study will enroll participants over the age of 50 who have gum recession. They will take the drug for eight weeks.

AN: If our results show that it's safe and there's actually efficacy, then that's a direct evidence showing that if we target something systemically, we could actually improve oral health.

AUBREY: He says he thinks of gum disease as a kind of canary in the coal mine. It's linked to a higher risk of heart disease, for instance, so they may share a common root cause.

AN: So really, if we can target the underlying biology, you know, we predict that it might address a lot of the other underlying conditions that happen along with periodontic disease - so not just the microbiome impact but the inflammatory pathways.

AUBREY: That underlie many age-related conditions. Rapamycin is a generic drug, so pharmaceutical companies have little incentive to fund new research. An has received grants to conduct this trial, which could open the door to further studies to determine whether rapamycin can help slow down other age-related diseases. Allison Aubrey, NPR News.

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