Canine conundrums
The life of a pet dog follows a predictable trajectory. Over time, the floppy-eared puppy that keeps falling asleep in his food bowl will become a lanky-legged adolescent with an insatiable interest in squirrels — before eventually settling into adulthood as a canine creature of habit, with a carefully chosen napping location and a well-rehearsed greeting ritual.
But as the years progress, his joints will stiffen and his muzzle will gray. And one day, which will inevitably arrive too soon, his wagging tail will finally still.
“When you adopt a dog, you’re adopting future heartbreak,” said Emilie Adams, a New Yorker who owns three Rhodesian Ridgebacks. “It’s worth it over time because you just have so much love between now and when they go. But their life spans are shorter than ours.”
In recent years, scientists have been chasing after drugs that might stave off this heartbreak by extending the lives of our canine companions. On Nov. 28, the biotech company Loyal announced that it had moved one step closer to bringing one such drug to market. “The data you provided are sufficient to show that there is a reasonable expectation of effectiveness,” an official at the U.S. Food and Drug Administration informed the company in a recent letter. (Loyal provided a copy of the letter to The New York Times.)
That means that the drug, which Loyal declined to identify for proprietary reasons, has met one of the requirements for “expanded conditional approval,” a fasttracked authorization for animal drugs that fulfill unmet health needs and require difficult clinical trials. The drug is not available to pet owners yet, and the FDA must still review the company’s safety and manufacturing data. But conditional approval, which Loyal hopes to receive in 2026, would allow the company to begin marketing the drug for canine life extension, even before a large clinical trial is complete.
“We’re going to be going for claiming at least one year of healthy life span extension,” said Celine Halioua, the founder and CEO of Loyal.
Whether the drug will actually deliver on that promise is unknown. Although a small study suggests LOY-001 might blunt metabolic changes associated with aging, Loyal has not yet demonstrated that it lengthens dogs’ lives.
But the letter, which came after years of discussion between Loyal and the FDA, suggests that the agency is open to canine longevity drugs, Halioua said.
More are in the pipeline. A team of academic researchers is conducting a canine clinical trial of rapamycin, which has been shown to extend the lives of lab mice. And Loyal is recruiting dogs for a clinical trial of another drug candidate, dubbed LOY-002.
These developments are a sign of the accelerating pace of the science and the seriousness with which researchers and regulators are taking a field that once seemed like science fiction. They also raise questions about what it might mean to succeed, said Daniel Promislow, a biogerontologist at the University of Washington and a co-director of the Dog Aging Project, which is conducting the rapamycin trial.
“What if it works?” he said. “What are the implications?”
Lapping at the fountain of youth
Aging may be an inevitability, but it is not an unyielding one. Scientists have created longer-lived worms, flies and mice by tweaking key aging-related genes.
These findings have raised the tantalizing possibility that scientists might be able to find drugs that had the same life-extending effects in people. That remains an active area of research, but canine longevity has recently started to attract more attention, in part because dogs are good models for human aging and in part because many pet owners would love more time with their furry family members.
The drugs under investigation act in different ways. Rapamycin, which has also attracted intense interest as a potential longevity drug for humans, inhibits a protein known as mTOR, which regulates cell growth and metabolism.
This year, a team of scientists including Promislow and some of his colleagues at the Dog Aging Project published an analysis of dogs that had been randomly assigned to receive either a low dose of rapamycin or a placebo for six months. Although the sample size was small, 27% of dog owners whose pets received the drug reported improvements in health or behavior, including increases in activity or playfulness, compared with 8% of owners whose dogs received a placebo.
LOY-001, an extended-release implant intended for large, adult dogs, is designed to modulate a different growth-related compound: insulin growth factor-1, or IGF-1. The IGF-1 pathway has been associated with aging and longevity in several species; in dogs, it is known to play a key role in determining body size. Although the idea remains unproven, some scientists hypothesize that high IGF-1 levels drive rapid growth and accelerated aging in large dogs, which generally have shorter life spans.
Loyal’s own research, which has not yet been published, suggests that LOY001 does reduce IGF-1 levels in dogs and that it might curb aging-related increases in insulin; an observational study of nearly 500 dogs also suggested that lower insulin levels were correlated with reduced frailty and a higher quality of life.
“It’s quite an exciting approach,” said Colin Selman, a biogerontologist of aging at the University of Glasgow, who was not involved in the research and had not personally reviewed the company’s data.
But proving that a drug can actually extend canine lives will require large, time-consuming clinical trials. Although some are underway, it will be at least several more years before the results are in. And regardless of the drug, researchers will need to demonstrate that it adds good, healthy years to a dog’s life, rather than just drawing out their decline, experts said.
It is too soon to say what longevity drugs will cost, but Halioua predicted that LOY-001 would work out to “mid-double-digit dollars per month.”
For some owners, cost will not be a deterrent, said Karen Cornelius of Illinois, who has owned mastiffs and other “giant” breeds for decades. Many died when they were about 9, said Cornelius, who runs several Facebook groups for owners of giant dogs.
“We were just having a discussion on one of my forums yesterday about how shortlived they were, and how people would give almost anything if they could extend that life,” she said.
Some ethicists worried that this enthusiasm could be exploited, especially if the drugs are advertised as fountains of canine youth while questions of long-term safety and efficacy remain unresolved. The dogs themselves cannot give consent,