The STAY study
What Loyal calls the largest trial ever run in animal health: 1,300 dogs aged 10 and over, half on LOY-002 and half on a placebo, for at least 4 years.
How it works
Each dog has an even chance of getting the pill or a look-alike placebo, and neither the owner nor the vet knows which (Loyal). Dogs come in six times in the first year and twice a year after that, and the study pays for their visits and lab work.
Who is in it
Loyal screened more than 1,500 dogs and enrolled 1,300 at 72 US vet clinics. Enrollment closed on July 14, 2025, so it is no longer taking dogs (Loyal). The first, an 11-year-old whippet called Boo, was dosed in December 2023 (Loyal).
What it measures
Lifespan, health and quality of life, compared between the two groups. Fortune reported in April 2026 that it is designed to detect a difference of at least one year (Fortune).
When results could come
Loyal has given no date. With the first dog dosed in December 2023 and a minimum of four years, late 2027 at the earliest. LOY-002 does not have to wait for it: conditional approval rests on the effectiveness case the FDA has already accepted, and STAY's results are what would turn it into a full approval (Loyal).
Sources
- Clinical trials, Loyal, read November 2, 2026.
- The STAY study finishes enrollment, Loyal, July 14, 2025.
- Meet Boo, the first dog dosed in the STAY study, Loyal, 2023.
- Dog lifespan drug and the FDA, Fortune, April 11, 2026.
- $100M for the first longevity drug, Loyal, February 11, 2026.