Startup's Pill Aims to Extend Dogs' Lifespans

Loyal's new drug targets aging's root causes to boost healthy years for man's best friend.

Apr. 11, 2026 at 9:20am by

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A ghostly, translucent X-ray image of a dog's pill capsule, its internal structure revealed in glowing lines against a dark background, conceptually representing the potential of this new longevity drug.An X-ray view of the innovative pill that could help dogs live longer, healthier lives.San Francisco Today

A San Francisco startup called Loyal is developing a daily prescription pill for senior dogs that the company believes can extend your loyal companion's healthy lifespan by targeting one of aging's most fundamental drivers: metabolic dysfunction. The drug, LOY-002, works as a caloric restriction mimetic, achieving some of the same benefits as a severely reduced-calorie diet, but without the hardship. Loyal is pursuing a conditional approval pathway from the FDA to bring the drug to market sooner, even as the large-scale STAY clinical trial continues.

Why it matters

If successful, Loyal's drug could rewrite the rulebook for canine and even human longevity science. The company's ambitious clinical trial is the largest ever conducted in veterinary medicine, aiming to show that targeting aging's root causes can meaningfully extend healthy lifespans for dogs, which could pave the way for similar breakthroughs in human medicine.

The details

Loyal's drug, LOY-002, works by mimicking the biological effects of caloric restriction without requiring dogs to actually restrict their food intake. The company believes this approach can help prevent or delay a range of age-related diseases like arthritis, cancer, and cognitive decline. Loyal is pursuing a conditional approval from the FDA to bring the drug to market sooner, even as the ongoing STAY study continues to monitor over 1,300 dogs across 72 veterinary clinics nationwide.

  • The STAY study, now about two and a half years in, will run a minimum of four years.
  • Loyal is pursuing a conditional approval pathway from the FDA, which is designed to allow drugs to reach the market before large-scale clinical trials are complete.

The players

Loyal

A San Francisco startup developing a prescription drug to extend healthy lifespans in senior dogs.

Dr. Brennen McKenzie

Loyal's director of veterinary medicine, who oversees the company's drug development and clinical trials.

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What they’re saying

“If we can pick off the underlying driver for all of these things, we can have a much greater impact on health and welfare and wellbeing than just working on each individual disease as it pops up.”

— Dr. Brennen McKenzie, Director of Veterinary Medicine, Loyal

“Part of the genius of the idea of LOY-002 is that it achieves some of the same goals biologically as caloric restriction without the hardship and the risks of doing that.”

— Dr. Brennen McKenzie, Director of Veterinary Medicine, Loyal

What’s next

The STAY study, which has enrolled over 1,300 dogs, will continue for at least another year and a half to monitor the long-term effects of Loyal's drug. If the results are positive, the company plans to pursue conditional approval from the FDA to bring the drug to market sooner.

The takeaway

Loyal's ambitious clinical trial represents a major step forward in the quest to extend healthy lifespans for man's best friend. If successful, the drug could not only transform canine care, but also pave the way for similar breakthroughs in human longevity science.