A pill that might buy your dog two more good years

Doges Editorial · 2026-06-04 · 6 min read

A biotech startup has enrolled 1,300 senior dogs in the largest clinical trial in veterinary history, testing a daily tablet designed to slow the biology of aging. The FDA has cleared the science as plausible. A launch is expected in 2026.

Every dog owner eventually runs the same arithmetic. A Great Dane weighs as much as a small human and lives, on average, about eight years. A Chihuahua weighs six pounds and often makes it past fifteen. The gap isn't random. It comes down, researchers now believe, to a single hormone — and a San Francisco biotech company called Loyal has spent the last several years trying to do something about it.

Loyal's drug is called LOY-002. It's a beef-flavored daily tablet for senior dogs, and it is currently being tested in 1,300 dogs across 70 veterinary clinics in the United States — the largest clinical trial in veterinary medicine history, according to the company. The FDA has reviewed its safety profile and accepted the scientific rationale for its effectiveness. A launch is expected sometime in 2026, pending completion of manufacturing requirements.

The hormone that speeds up time

The size-lifespan relationship in dogs comes down to a hormone called IGF-1, or insulin-like growth factor 1. It drives rapid growth during puppyhood, which is why a Great Dane goes from a few pounds to 130 in about a year. After maturity, large breeds continue circulating IGF-1 at elevated levels — sometimes 28 times higher than what you'd find in a Chihuahua.

At those concentrations, IGF-1 accelerates cellular aging. It increases metabolic stress, promotes chronic inflammation, and appears to push large dogs toward earlier disease onset — cancer, arthritis, cognitive decline — at a rate that small dogs don't experience. The Chihuahua's clock runs slower because its IGF-1 levels run lower. The mechanism is that direct.

LOY-002 is designed as a caloric restriction mimetic. It targets the metabolic dysfunction that IGF-1 creates in aging dogs, attempting to reproduce the biological effects of reduced caloric intake without requiring the dog to eat less. The precedent for that idea is solid: in a landmark study, dogs on caloric restriction lived approximately two years longer than controls and had significantly delayed onset of cancer and osteoarthritis. Two years is the figure the company keeps returning to.

The STAY study

The pivotal clinical trial — called STAY — is fully enrolled with 1,300 dogs at 70 clinics across the country. Dogs are randomized to LOY-002 or placebo. The study tracks healthspan outcomes alongside safety metrics, which matters for a drug designed to slow aging rather than treat a specific disease. Loyal is trying to measure quality of life and disease delay over time, not just whether the dog survives to a certain point.

The trial accepts dogs aged 10 and older weighing at least 14 pounds — which means it is designed for senior dogs of nearly all breeds, not just giant ones. In prior studies at doses ranging from 1x to 5x the intended clinical level, the company reports no clinically significant adverse effects. The drug has been tested in more than 400 companion animals for periods up to one year.

LOY-002 aims to address the metabolic dysfunction that all dogs experience as they age, delaying the start of many diseases that reduce quality of life for senior dogs and giving dogs, and their human family, more enjoyable time together.

— Loyal

What the FDA actually said

Veterinary drug approvals work differently from human drug approvals. Loyal is navigating a pathway called Expanded Conditional Approval, which requires clearing three major requirements before launch: a reasonable expectation of effectiveness (RXE), a target animal safety (TAS) review, and a manufacturing quality demonstration. Loyal has now cleared the first two.

The RXE package — accepted by the FDA in February 2025 — established that the mechanism was scientifically plausible. The more recently completed TAS package showed the drug was safe across the tested population. The FDA's acceptance of these packages doesn't mean the drug is approved; it means the agency reviewed the underlying science and didn't find it implausible. That's a meaningful bar.

Also in the room: rapamycin

Loyal is not the only company trying to slow aging in dogs. The Dog Aging Project's TRIAD study is simultaneously running a randomized, placebo-controlled trial of rapamycin — an immunosuppressant with well-documented longevity effects in mice — in aging dogs at multiple sites across the country. The two drugs work through different mechanisms: LOY-002 targets IGF-1 and metabolic aging; rapamycin works through the mTOR pathway.

The Dog Aging Project, which has enrolled tens of thousands of dogs in various longitudinal studies, describes the rapamycin trial as "the first rigorous test of a pharmacologic intervention against biological aging with lifespan and healthspan metrics as endpoints to be performed outside of the laboratory in any species." That's a long sentence, but the short version is: dogs are teaching us what might work in humans before we ever try it in humans.

The dedication and commitment of these owners to participate in research and discovery to better the health of dogs is remarkable.

— Dr. Kate Creevy, Dog Aging Project

What this actually means for your dog

If LOY-002 launches in 2026, it will cost approximately $100 a month. That's not trivial. But it's not the number to focus on. The figure that matters is the two years from the caloric restriction studies, and what two more years of a healthy senior dog actually looks like — more mornings, more walks, one more winter, the particular kind of time that is almost impossible to explain to someone who doesn't have a dog.

Loyal uses the word healthspan rather than lifespan to describe what they're after. The period of life spent free from the diseases that make a dog's last years hard — the joint pain that turns a morning walk into a negotiation, the cognitive changes that disorient a dog who has always known exactly where home is. LOY-002 is designed to push the point at which that slide begins further into the future.

The STAY study is still running. There is no pill yet. But there are 1,300 senior dogs in vet clinics around the country, some of them on something that might help, some of them on placebo, all of them doing what senior dogs do — living their ordinary mornings, pulling their people toward the usual routes, blinking in the kitchen light. The data is accumulating alongside them.