Clinical trial for Longevity drug meets goal of enrolling 1000 dogs

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. According to Loyal, the biotechnology company developing LOY-002, 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.¹

“The STAY study is our pivotal field trial. This is the key component in getting FDA approval for LOY-002,” Brennen McKenzie, VMD, MSc, MA, director of veterinary medicine for Loyal, said in a dvm360 interview.

Photo courtesy of Loyal

Winston, a 10-year-old miniature dachshund, is the 1000th enrolled patient in Loyal's STAY study.

LOY-002 is being developed to extend healthy lifespan in senior dogs by improving metabolic health to delay the onset and reduce the impact of age-associated diseases. Launched in December 2023, the study’s first patient, an 11-year-old Whippet named Boo, was enrolled at the Animal Hospital of Dauphin County in Harrisburg, Pennsylvania.² The milestone 1000th patient was Winston, age 10 years, a miniature dachshund receiving veterinary care at the Franklin Animal Clinic in Indiana.¹

The STAY study goes beyond investigation of longevity. It also measures quality of life based on pet owners’ assessments of their dogs, according to Ellen Ratcliff DVM, vice president of clinical and veterinary medicine at Loyal. “It doesn’t do anybody any good if their dog lives longer, but they live longer in that period at the end of their life where they don’t feel well, and they’re sick, having all kinds of degenerative and aging diseases,” Ratcliff said in an earlier dvm360 interview.

With the STAY study, LOY-002 is being prescribed by veterinarians and administered to enrolled patients as a daily beef-flavored pill. Dogs age 10 years or older and weighing at least 14 pounds are eligible.²

Over the study’s span, 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.²

A total enrollment of 1300 canine patients would translate to an increase in the study’s sample size, providing even more scientific data for observing the drug’s effects.¹ The additional 300 patients “is going to give us even more power to be able to look at the effects of our drug on lifespan and health and wellbeing in these dogs,” McKenzie noted.

“I'm excited because I'd like to see the drug made available to veterinarians and dog owners, but I'm [also] excited because it's going to be a treasure trove of data on canine aging and how they age, and what we can potentially learn that we could then use to develop other targets to do things to help them live longer, healthier lives,” he added.

Reaching the milestone of 1000 enrolled patients follows Loyal’s February 2025 announcement that the FDA’s Center for Veterinary Medicine granted acceptance of the Reasonable Expectation of Effectiveness (RXE) section of the conditional approval application for LOY-002.³

Ratcliff noted that the RXE acceptance was an achievement that serves as a testament to the importance of the STAY study. Celine Halioua, CEO of Loyal, said RXE acceptance was important for advancing LOY-002.³

“Everything we do is in service of helping dogs live longer, healthier lives,” Halioua said.³ “These 2 milestones represent our ongoing commitment to that mission through years of diligence and hard work. Proving efficacy is one of the most challenging parts of developing a novel drug. While we still have significant work to do, RXE increases the probability that dogs will soon have access to our longevity drugs.”

In the meantime, McKenzie advised veterinary professionals to never accept ‘old age’ as an explanation for a patient’s condition, and keep in mind there are likely things that can be done to help improve outcomes. “What you can do now is what you already know,” he said. “Keep them a healthy weight, keep them engaged and active. Keep up with your preventive medicine, and watch this space, because there's going to be new things that you can do that we didn't even think were possible a few years ago.”

References

1. Lee J. Breaking records: the STAY study enrolls 1,000 dogs. News release. Loyal. April 14, 2025. Accessed April 14, 2025. https://loyal.com/posts/stay-enrolls-1000-dogs
2. A clinical trial is launched for a novel drug that could extend healthy lifespan in senior dogs. dvm360. February 1, 2024. Accessed April 14, 2025. https://www.dvm360.com/view/a-clinical-trial-is-launched-for-a-novel-drug-that-could-extend-healthy-lifespan-in-senior-dogs
3. Crossley KC. Second drug for canine healthy lifespan extension receives FDA support. dvm360. February 26, 2025. Accessed April 14, 2025. https://www.dvm360.com/view/second-drug-for-canine-healthy-lifespan-extension-receives-fda-support