A Life-Extension Drug for Big Dogs Is Getting Closer to Reality

There’s a well-established inverse relationship between a dog’s size and its expected lifespan. Bernese mountain dogs and Great Danes live just six to eight years, for example, while corgis can live up to 15 years and Chihuahuas up to two decades.

San Francisco biotech company Loyal wants to close that gap, and is developing an experimental drug to extend the lifespan and improve the quality of life of large and giant dog breeds. Today, the company announced that based on early data, the US Food and Drug Administration has determined that Loyal’s drug has a “reasonable expectation of effectiveness.” The company hasn’t yet shown that its drug actually extends lifespan, but the FDA decision signals the agency’s confidence in Loyal’s approach, and the drug will soon be tested in a bigger trial.

“Big dog owners want more time with their dogs,” says Loyal CEO Celine Halioua. “It’s really heartbreaking to people that they don’t live that long.” She argues that the wide variety in dog sizes isn’t natural, but a result of selective breeding by humans to create dogs with certain physical traits or that can perform specific tasks. On average, mixed-breed dogs live longer than their purebred counterparts.

So far, the FDA has not approved any drugs to expand the lifespan of animals—or humans, for that matter. “This is completely novel,” says Linda Rhodes, former CEO of pet biotech company Aratana Therapeutics and a consultant for Loyal. It’s difficult to study life-extension drugs in people, she says, because humans live relatively longer lives than other species. But starting with dogs—and the breeds with the shortest lives—could yield important clues. “The implication for other species, including humans, is pretty profound,” she says.

Loyal’s experimental drug is an injection designed to be given every three to six months by a veterinarian. The drug is meant to lower levels of a hormone called IGF-1, which is involved in growth and metabolism and has been linked to dog size. Large dogs have a genetic variant that leads to high levels of IGF-1 and small dogs have a different variant that results in lower levels.

Inhibiting this hormone has been shown to increase lifespan in worms, flies, and rodents. In humans, both very high and very low levels increase mortality risk, while a midrange is associated with the lowest mortality.