If this drug gets approved, it won't just be the first medicine to extend a dog's life. It will be the first FDA-approved drug to extend lifespan in any species. Human or animal. In the history of medicine.
That's the part that isn't getting enough attention.
A San Francisco biotech company called Loyal is developing LOY-002 — a daily prescription pill for senior dogs that targets the metabolic drivers of aging and slows them down. For dogs 10 years and older, weighing at least 14 pounds. It has now cleared two of the three major FDA hurdles required for approval. The third — and final — is underway. A market launch is targeted before the end of 2026.
What the Drug Actually Does
LOY-002 works by targeting IGF-1 — Insulin-Like Growth Factor 1, a hormone that plays a central role in cellular growth, metabolism, and aging throughout a dog's life. Higher IGF-1 activity is associated with faster biological aging, which is part of why large breeds live significantly shorter lives than small dogs.
The drug mimics caloric restriction — one of the most consistently research-backed methods of extending lifespan across species. Decades of research have shown that reducing caloric intake (not to harmful levels) alters how cells process energy and can extend their lifespan. LOY-002 gives senior dogs those metabolic benefits without actually eating less.
"LOY-002 aims to extend a dog's healthy lifespan by about one year," Loyal CEO Celine Halioua told NBC News — which translates to approximately five dog years of additional healthy life. Not just more time. Healthier time, with delayed onset of the diseases that typically end a dog's life.
The Two Hurdles It's Already Cleared
The FDA's conditional approval pathway for veterinary drugs has three major technical sections. LOY-002 has cleared two of them.
The first — Reasonable Expectation of Effectiveness (RXE) — was accepted by the FDA in February 2025. This means the agency reviewed Loyal's data and agreed the drug can reasonably be expected to do what it claims: extend a dog's lifespan.
The second — Target Animal Safety (TAS) — was accepted by the FDA in January 2026. This means the FDA reviewed Loyal's safety data from multiple studies, including field safety data from over 400 dogs in the ongoing STAY efficacy trial, and agreed the drug is safe for its intended use in senior dogs.
What's left: the manufacturing section. Loyal needs to demonstrate that it can produce LOY-002 at scale under FDA-compliant manufacturing standards. This is typically the final step before conditional approval is granted.
Why the "Any Species" Part Matters
The FDA has never approved a drug explicitly designed to extend lifespan. Not for dogs. Not for any animal. Not for humans.
This would be the first. Officially. In the regulatory record. A government agency acknowledging that slowing aging is a medical goal worth pursuing — and certifying a drug that does it.
That matters beyond dogs. The science of longevity — targeting the metabolic mechanisms of aging rather than treating the diseases aging causes — is one of the most actively researched areas in medicine. Rapamycin, metformin, senolytics, and now IGF-1 inhibitors are all being studied for human lifespan extension. LOY-002 going through the FDA process and receiving approval would be proof of concept for the entire field.
If it works in dogs — and 1,300 dogs in 70 veterinary clinics enrolled in the STAY study are generating data on exactly that question — the implications for human longevity research are significant. Dogs age similarly to humans. They get many of the same age-related diseases. They live with us. They are, in many ways, the best available model for studying human aging.
What Dog Owners Can Do Right Now
LOY-002 is not yet available. Your vet cannot prescribe it. If you have a senior dog — 10 years or older, at least 14 pounds — the answer for now is: watch this space.
Loyal's STAY trial, with 1,300 dogs across 70 veterinary clinics, is the largest clinical trial in the history of veterinary medicine. Results are expected to form the basis of the final FDA submission. If the manufacturing section clears — and Loyal has given no indication of problems there — the pill could reach veterinary clinics before the end of 2026.
The company is also developing two companion drugs: LOY-001, for large and giant breeds aged 7 and older, which reduces IGF-1 through a veterinarian-administered injection every three to six months; and LOY-003, for giant breeds aged 5 and older. All three are in various stages of the FDA process.
The first drug in history to extend a dog's life — and by extension, to prove that lifespan itself can be treated — is closer than it has ever been. For anyone who has ever watched a dog get old too fast, that is not a small thing.
