Regulatory milestone marks progress toward the first longevity drug for dogs, bringing it closer to potential FDA approval.
Clinical-stage animal health company Loyal has achieved a significant regulatory milestone with the US Food and Drug Administration (FDA) granting Reasonable Expectation of Effectiveness (RXE) acceptance for LOY-002, a drug designed to extend the lifespan and improve the health of senior dogs. This development moves the company one step closer to securing conditional approval for the drug, which could become the first FDA-approved treatment specifically targeting longevity in dogs.
In addition to this regulatory progress, Loyal announced that it had raised $22 million in a Series B-2 funding round led by Valor Equity Partners and Collaborative Fund, among others. This new investment follows the company’s $45 million Series B round in 2024, bringing the total funding for Loyal to more than $150 million.
Progress toward longevity-focused veterinary medicine
LOY-002 is designed for dogs aged 10 years and older, weighing at least 14 pounds, and aims to address metabolic dysfunction associated with aging. The drug’s efficacy is currently being evaluated through the STAY study, a large-scale clinical trial involving over 1,000 dogs across the United States. The study, which is double-blind and placebo-controlled, is expected to provide comprehensive data on LOY-002’s effectiveness over the next several years.
“Everything we do is in service of helping dogs live longer, healthier lives,” said Loyal Founder and CEO Celine Halioua.
“These two 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.”
RXE acceptance is a critical step in the FDA’s regulatory pathway for veterinary drugs; it indicates that preliminary data suggests LOY-002 has the potential to extend canine lifespan. Conditional approval, which Loyal is targeting in 2025, would allow the company to market the drug while continuing to collect additional safety and efficacy data.
The significance of RXE for Loyal’s research
Loyal has positioned itself as a pioneer in the emerging field of veterinary longevity medicine. The company’s portfolio includes LOY-002, as well as LOY-001 and LOY-003, which target IGF-1, a growth hormone associated with reduced lifespan in large-breed dogs. LOY-001, a monthly injectable therapy, previously received RXE acceptance in November 2023, while LOY-003, a daily pill, remains under development.
Dr Ellen Ratcliff, VP of Clinical and Veterinary Medicine at Loyal, emphasized the importance of this regulatory step “Achieving RXE acceptance is a testament to the ongoing importance of the STAY study,” she said. “Completing enrollment and seeing what the data shows over the next several years is critical, but this is an important step in the process. We now have validation from one of the highest quality regulatory agencies in the world that the drug we’re testing has a reasonable expectation of extending a dog’s life.”
The RXE decision follows a rigorous review process by the FDA’s Center for Veterinary Medicine, which evaluates safety, efficacy and manufacturing quality before granting full approval. The FDA’s recognition of LOY-002’s potential effectiveness signals confidence in the underlying science and the company’s approach to canine longevity.
What this means for pet owners and veterinarians
Should LOY-002 receive conditional approval in 2025, it will be available through veterinarians, who will assess whether a dog meets the criteria for treatment. Unlike supplements, which do not require regulatory approval, LOY-002 will be subject to FDA oversight, ensuring its safety and efficacy.
Loyal’s broader goal is not only to extend canine lifespan but also to enhance quality of life by delaying the onset of age-related diseases. The company’s research focuses on addressing fundamental mechanisms of aging, offering a science-driven approach to veterinary medicine.
With the latest funding round, Loyal intends to advance its clinical programs and prepare for potential commercialization. The company’s total investment now exceeds $150 million, reflecting strong investor confidence in the future of longevity-focused veterinary pharmaceuticals.
As Loyal continues its clinical research and regulatory engagement, the coming years will be critical in determining whether its drugs can achieve full FDA approval and reach the market. For now, RXE acceptance for LOY-002 represents a meaningful step forward in the pursuit of extending the healthy lifespan of companion dogs.
