STAY study: LOY-002 for healthy lifespan extension in senior dogs (Loyal)
The STAY study is Loyal's pivotal, placebo-controlled, four-year field trial of LOY-002, a daily pill intended to extend healthy lifespan in dogs aged 10 years or older weighing at least 14 lb. Enrolment reached 1,000 dogs at 70 US veterinary clinics and was expanded to 1,300, completing in July 2025. The FDA Center for Veterinary Medicine accepted the reasonable-expectation-of-effectiveness section in February 2025 and the target-animal-safety section in January 2026 under the expanded conditional approval pathway; no efficacy results have been published.
Record
| Design | company regulatory program |
|---|---|
| Status | ongoing |
| Setting | client owned |
| Intervention | LOY-002, a prescription daily pill targeting age-related metabolic dysfunction |
| Intervention class | drug |
| Comparator | placebo |
| Dose regimen | daily oral tablet (dose not disclosed) |
| Duration | four-year study |
| Dogs | 1,300 |
| Population note | enrolment completed July 2025 at 70 veterinary clinics in the US (initial goal 1,000 dogs, expanded by 300) |
| Breed | any; dogs of nearly every size |
| Age | 10 years or older, weighing at least 14 lb |
| Primary outcome | lifespan and quality of life compared with placebo; adverse effects |
| Lead organisation | Loyal (San Francisco) |
| Sponsor or funder | Loyal |
| Start year | 2024 |
| Tags | lifespan, drug, senior-dogs, pivotal-trial, fda-conditional-approval, loyal |
Notes: Company- and trade-press-sourced; no peer-reviewed publication of design or results as of 2026-10-01. The drug's mechanism and dose are not disclosed beyond 'targets age-related metabolic dysfunction'.
Sources and verbatim quotes
Clinical trial for Longevity drug meets goal of enrolling 1000 dogs (dvm360) (2025), snapshot dvm360-stay-enrollment (press)
The STAY study, a clinical trial investigating the developmental longevity drug LOY-002, has reached its goal of enrolling 1000 canine patients at 70 veterinary clinics across the US.
this 4-year study may be the world’s largest veterinary clinical trial, and a new goal has been set for expanding the trial to include an additional 300 patients.
Dogs age 10 years or older and weighing at least 14 pounds are eligible.
Loyal is collecting data on the drug’s potential impact on the lifespan and quality of life for dogs receiving LOY-002, compared to those receiving a placebo, as well as any adverse effects reported in the study population.
Lifespan extension drug in development for senior dogs reaches a new milestone (dvm360) (2026), snapshot dvm360-stay-milestone (press)
Scientific evidence also included the ongoing STAY study, which completed patient enrollment with 1300 dogs at 70 veterinary clinics across the US in July 2025.
LOY-002 is a prescription daily pill that targets age-related metabolic dysfunction and is designed to improve quality of life in canines 10 years and older, weighing at least 14 lb.
Loyal Receives FDA Acceptance of Safety Package for Senior Dog Lifespan Extension Drug (company release, 2026-01-13) (2026), snapshot yahoo-loyal-safety-acceptance (company)
announced today that the FDA's Center for Veterinary Medicine (CVM) has accepted the Target Animal Safety (TAS) technical section of its conditional approval application for LOY-002
TAS completion follows on several milestones for LOY-002 in the past year, including the FDA's acceptance of RXE in February 2025.
LOY-002, a prescription daily pill, aims to extend the healthy lifespan of senior dogs and maintain their quality of life as they age by proactively targeting the underlying metabolic drivers of aging and delaying the onset of disease.
At 1,300 dogs across 70 veterinary clinics, it's the largest clinical trial in the history of veterinary medicine.
Loyal: for dog owners (company page) (2026), snapshot loyal-for-dog-owners (company)
LOY-002 is our drug for senior dogs , a daily pill intended to help dogs of nearly every size live a longer, healthier life.
Our dog longevity drugs are all being developed under the FDA Center for Veterinary Medicine’s expanded conditional approval (XCA) pathway.
Reproduce: canine_trial_search(trial_id="loyal-stay-loy-002") in dog-geroscience-mcp; dataset canine-trial-registry.