One way to identify the more promising candidates would be to see which ones also work in dogs. Dogs are long-lived enough to serve as a better model for human aging than mice, but short-lived enough that treatment can be tested in a few years.

Matt Kaeberlein, CEO of Optispan and an affiliate professor at the University of Washington, was among the most vocal critics of Sinclair’s dog longevity claims. He’s also in competition as co-director of The Dog Aging Project. That project involves collecting data on thousands of dogs as well as conducting a dog clinical trial with a drug called Rapamycin. It’s currently approved for people who’ve had organ transplants. At high doses, it causes mouth sores and other nasty side effects, he admits, but can extend the lives of mice and — at low doses — might do the same in dogs or humans.

A group of biohacker types is already taking Rapamycin off-label in the hope of life-extension, he said. He’s trying to get data from them, messy as it is, because there might be useable information there. (Caplan, the NYU ethicist, says he thinks it’s unethical for doctors to prescribe this drug off-label for longevity.)

Kaeberlein said the biological data they’re collecting from all those thousands of dogs could lead to an explanation for the fact that big dogs don’t live as long as small ones. “If you compare a Great Dane to a chihuahua on average, it’s at least a twofold difference in life expectancy,” he said.

But his project might be a victim of the field’s wider credibility problem. It had been funded by the National Institutes of Health, but he and his colleagues learned recently that a five-year grant established in 2018 and extended one year probably won’t be renewed. He’s now working to get private money.

Charles Brenner, a biochemist at the City of Hope National Medical Center in Los Angeles, is another vocal critic of Sinclair’s claims regarding dogs and humans. (Like most researchers on the forefront of aging, he has his own supplement ties as chief scientific advisor of a bioscience company called ChromaDex.)

Brenner is also skeptical of those who claim various treatments or drugs can reverse a person’s “biological age” as calculated through proxies measured in blood — including telomeres and epigenetic markers. None of these measure aging as well as walking speed, he said.

When I asked him about the Rapamycin study in dogs, he said it’s “worth a try” because the trial measures actual lifespan rather than some proxy. But he isn’t betting on this particular drug. He’s more optimistic about work done by a company called Loyal, profiled in 2021 by Bloomberg Businessweek.

Brenner says while Loyal has been secretive about the drug, he thinks what they’re now testing inhibits the production or action of growth hormone. Growth hormone, he said, is connected to the faster aging they see in larger dogs compared to smaller ones.

There’s promise in studying how and why animals age — not just dogs but clams that can live to 500, rockfish that survive until 200 and whales that reach 80. Once scientists understand the mechanisms of aging, they’ll be much better able to find ways to help us — and our furry friends — live longer and healthier lives.

But first, they need investors and the public to take them seriously.

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This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

F.D. Flam is a Bloomberg Opinion columnist covering science. She is host of the “Follow the Science” podcast.

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