It’s a sad fact that dogs don’t live as long as we would like. The average dog lives around 8 to 15 years, with large breeds having shorter lifespans than smaller breeds. Our canine friends manage to pack a lot of love into those years, but wouldn’t it be wonderful if there were a way to keep them alive and healthy much longer? There soon may be.

Scientists are working to develop drugs that could extend dogs’ lifespans and health spans. Late last year, Loyal, a San Francisco biotech company, announced that the Food and Drug Administration had granted what is known in the parlance of drug regulation as a “reasonable expectation of effectiveness” for a drug the company has in development.

If effective, the medication would extend the lifespan of large-breed dogs. The FDA decision isn’t about approval of the drug, but it is an important step toward that goal. 

Variations in Dog Lifespans

In the blog post about the FDA’s decision, Celine Halioua, CEO of Loyal, explained that the variation in lifespans seen in dogs is unusual. It’s rare to have this much lifespan disparity within a species. The reason is due, at least in part, to “the process of selective breeding that ‘created’ these dog breeds,” she wrote.

Dogs bred to be large developed especially high levels of  IGF-1 (insulin-like growth factor one), a hormone that drives cell growth. Loyal’s new drug turns down IGF-1 signaling. The company hopes that this will slow aging.

The mechanism makes sense, says Matt Kaeberlein, biogerontologist and founder and co-director of The Dog Aging Project. “It’s almost certain that if you took a big dog and turned down IGF-1 during development, you would get a dog that lives longer. But you’d also get a smaller dog. The question is whether you can get the benefits of longevity from starting the treatment in middle age.”

He adds that there are some data in laboratory animals — mostly mice — to support this.

Read More: Do Selective Breeding Practices Harm Dogs?

Are There any Side Effects of IGF-1?

But what about potential side effects? Kaeberlein sees a couple of possible issues. IGF-1 is involved in muscle growth and bone density, so suppressing the hormone could possibly lead to a reduction in muscle mass or bone density, though he adds that this is just speculation at this point. Loyal will have to conduct safety studies as a part of the approval process.

Not all potential side effects are bad. “We know that IGF-1 is a risk factor for cancer, and a lot of dogs die of cancer,” says Kaeberlein. “So even if it doesn’t have an effect on biological aging, the drug might offer a benefit in terms of a reduction in cancer.”

Meanwhile, the Dog Aging Project is following about 50,000 dogs in a longitudinal study of aging. The dogs live with their owners at home, and the project team collects data about the animals’ lives, including genome sequences for some of the participants. The aim is to identify the most important genetic and environmental factors that influence aging and health as the animals age.

A subset of the dogs in the Dog Aging Project are taking part in a randomized controlled clinical trial of Rapamycin, a drug used to treat some cancers and prevent organ rejection in transplant patients. Research has shown the drug can slow aging in some species, and the study is designed to see if it has that effect on dogs.

No matter what the breed, we lose our dogs too soon. If these studies pan out, we may get to keep them a little longer. 

Read More: The Drug That Could One Day Help People — and Dogs — Live Longer

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