In a significant development for veterinary medicine and pet care, Loyal’s innovative anti-aging medication for dogs has achieved an important regulatory milestone. The biotech company’s drug LOY-002 recently received FDA certification for “reasonable expectation of efficacy,” representing a crucial step toward bringing this longevity-enhancing treatment to market. This advancement, alongside parallel research efforts like the Dog Aging Project, signals a new frontier in veterinary medicine focused on extending not just lifespan but the healthy, active years of companion animals. The research has profound implications not only for canine health but potentially for understanding aging processes that could benefit human medicine as well.

TL;DR

Loyal’s anti-aging drug LOY-002 has achieved FDA “reasonable expectation of efficacy” certification, marking a significant step toward market approval.
The company is developing three longevity-focused drugs targeting different dog populations: LOY-002 (senior dogs), LOY-001 (large breeds, injectable), LOY-003 (large breeds, pill form).
The STAY clinical trial is evaluating LOY-002’s impact on senior dogs across 70 U.S. veterinary clinics.
Dog Aging Project and rapamycin research explore additional longevity treatments with broader implications for human medicine.

Loyal’s Breakthrough in Canine Longevity Medicine

Loyal’s Canine Anti-Aging Drug Portfolio

Loyal’s research focuses on extending the healthy lifespan of dogs through three targeted drugs:

Drug	Target Audience	Mechanism	FDA Status
LOY-002	Senior dogs (10+ years, 14+ lbs)	Improves metabolic health to slow aging	Expecting conditional approval by late 2025
LOY-001	Large breeds (7+ years, 40+ lbs)	Modulates IGF-1 to slow growth-driven aging	FDA “reasonable expectation of efficacy” (Nov 2023)
LOY-003	Large breeds (7+ years, 40+ lbs)	Pill form alternative to LOY-001	In development

How Do These Drugs Work?

LOY-002: Enhances metabolic health in senior dogs to slow aging-related decline.
LOY-001 & LOY-003: Target IGF-1, a hormone linked to shorter lifespans in large breeds.

Regulatory Milestone & Market Path

Loyal’s FDA milestone brings LOY-002 closer to availability, but key steps remain:

Regulatory Step	Status
FDA “Reasonable Expectation of Efficacy”	✅ Approved (Feb 2025)
Safety & Manufacturability Certification	Pending
Conditional Approval (Market Entry)	Expected late 2025

Loyal has secured $150M in funding to support the final approval process and manufacturing scale-up.

STAY Clinical Trial: Real-World Testing of LOY-002

Loyal launched the STAY clinical trial in 2023 to evaluate LOY-002 in real-world settings:

Trial Feature	Details
Study Type	Randomized, double-blind
Participants	1,000 senior dogs (10+ years)
Locations	70 U.S. veterinary clinics
Timeline	4 years

Early Results & Pet Owner Perspectives

First participant: Boo, an 11-year-old Whippet, enrolled in Pennsylvania.
Owner sentiment: “If it can help my dog and others, it’s worth it.”

Scientific Basis of Canine Aging & Treatment Approaches

Loyal’s longevity approach is built on:

Aging Factor	Drug Response
Metabolic Decline	LOY-002 boosts metabolic health
IGF-1 Overactivity	LOY-001 & LOY-003 regulate IGF-1 in large breeds
Age-Related Functional Decline	LOY-002 shows early signs of improving quality of life

Loyal is not promising “immortal dogs” but aims to extend healthy years by delaying aging.

Parallel Research: The Dog Aging Project & Rapamycin Study

While Loyal pursues proprietary drug development, other longevity research is ongoing:

Project	Focus	Funding & Status
Dog Aging Project (DAP)	Large-scale study on dog longevity	$7M NIH Grant (2025)
TRIAD Clinical Trial	Testing rapamycin for lifespan extension	180+ dogs enrolled (Goal: 580)

Why Rapamycin?

Used in human medicine for immune suppression.
Early studies suggest it may extend lifespan and reduce age-related diseases in dogs.

Loyal’s breakthrough in veterinary longevity medicine could transform pet care by extending healthy lifespan in dogs. Their research, combined with initiatives like the Dog Aging Project, is paving the way for future advancements—potentially even for human aging treatments.

This medication targets age-related metabolic dysfunction, which is a key factor in canine aging and associated health decline

Loyal has developed a comprehensive approach to addressing age-related decline in dogs through three distinct drug formulations, each targeting specific segments of the canine population. LOY-002, the company’s most advanced product in the regulatory pipeline, is a beef-flavored pill designed specifically for senior dogs aged 10 years and older weighing at least 14 pounds1. This medication targets age-related metabolic dysfunction, which is a key factor in canine aging and associated health decline2. The drug aims to improve metabolic health with the specific goal of reducing age-associated disease while extending healthy lifespan, allowing dogs to maintain their quality of life as they age3.

In addition to LOY-002, Loyal has developed LOY-001, an injectable medication specifically formulated for large and giant-breed dogs such as Rottweilers, Great Danes, and Bernese Mountain Dogs2. This treatment received its own FDA reasonable expectation of effectiveness acceptance in November 2023, marking Loyal’s first regulatory achievement2. The third drug in development, LOY-003, provides the same benefits as LOY-001 but in a more convenient daily pill form, also targeting large and giant-breed dogs aged 7 years and older weighing at least 40 pounds2 3.

The company’s approach to large-breed longevity differs mechanistically from its senior dog treatment. LOY-001 and LOY-003 specifically target insulin-like growth factor 1 (IGF-1), a hormone that drives cell growth and is believed to accelerate aging and reduce lifespan in larger dogs5. By modulating IGF-1 levels, these medications aim to address one of the fundamental biological factors behind the shorter lifespans commonly observed in larger dog breeds. This multi-pronged approach demonstrates Loyal’s comprehensive strategy for addressing canine aging across different populations and through different biological mechanisms.

The company has stated they plan to earn conditional approval from the FDA by the end of 2025, which would allow them to begin marketing the product while continuing to gather additional clinical data

The FDA’s certification of “reasonable expectation of efficacy” for LOY-002 represents a crucial regulatory milestone, though several steps remain before the drug becomes available for prescription. This certification, granted in February 2025, acknowledges that sufficient preliminary evidence exists to support the drug’s effectiveness claims for extending healthy lifespans in senior dogs1 2. However, Loyal must still receive FDA certification that the drug is safe for use and can be manufactured at commercial scale before veterinarians can begin prescribing it1.

Loyal appears confident in meeting these remaining regulatory requirements, noting they have “extensive data supporting both” safety and manufacturability1. The company has stated they plan to earn conditional approval from the FDA by the end of 2025, which would allow them to begin marketing the product while continuing to gather additional clinical data1 2. This conditional approval pathway provides a balanced approach that could bring innovative treatments to market more quickly while ensuring ongoing safety and efficacy monitoring.

The company’s progress in navigating these regulatory challenges has impressed industry observers, particularly since they are “breaking new regulatory ground,” according to Linda Rhodes, VMD, PhD, a member of Loyal’s Board of Directors2. This pioneering work establishes precedents that could streamline future developments in the emerging field of veterinary longevity medicine. To support these efforts, Loyal has secured substantial financial backing, raising $22 million in their B-2 funding round from investors including Valor Equity Partners and Collaborative Fund, bringing their total investment to more than $150 million2. These resources will support both the regulatory process and manufacturing scale-up necessary to bring their products to market.

The STAY Clinical Trial: Testing LOY-002 in Real-World Settings

To generate the necessary data for full regulatory approval, Loyal launched the STAY clinical study in late 2023, which represents one of the most ambitious veterinary clinical trials to date2 6. This large-scale study has enrolled dogs across approximately 70 U.S. veterinary clinics and aims to include 1,000 participants over its four-year duration2 5. The study design follows a randomized, double-blind protocol where half of the enrolled dogs receive the beef-flavored LOY-002 pill while the other half receive a placebo, allowing for robust scientific evaluation of the drug’s effects2.

The first dog to participate in this groundbreaking study was Boo, an 11-year-old Whippet from Pennsylvania who competes in a dog sport called scent work5. Boo’s owner, Deb Hanna, expressed enthusiasm about participating in research that could help not only her dog but potentially benefit many others: “It could help other dogs, including my younger dogs someday. It’s very important. I think anybody that has an older dog that could participate would jump at the chance.”5 This sentiment reflects the strong interest among pet owners in extending the healthy lifespan of their companion animals.

The STAY study is notable not only for its scale but also for its inclusivity in engaging veterinary practices that have not previously participated in clinical research. Ellen Ratcliff, DVM, vice president of clinical and veterinary medicine at Loyal, highlighted that they are “using a lot of clinical trial-naïve study sites—veterinarians who have never participated in clinical research or doing clinical research at their clinics.”2 This approach broadens the base of veterinary science while ensuring diverse geographical representation across rural, urban, and metropolitan areas. The study is collecting data not just on longevity but also on quality of life as assessed by pet owners, recognizing that extending lifespan without maintaining well-being would not be meaningful improvement2.

As Celine Halioua, Loyal’s founder and CEO, explained: “We’re not making immortal dogs. The way the drug extends lifespan, we hypothesize, is by extending health and thus shortening the rate of aging.”

LOY-002’s approach to extending canine lifespan centers on improving metabolic health, which naturally declines as dogs age1 3. Metabolic dysfunction contributes to numerous age-related conditions and generally reduces vitality in senior dogs. By addressing these metabolic issues, Loyal hypothesizes that LOY-002 can extend healthy lifespan by at least one year1. However, the company has been careful to set realistic expectations about what their drug can achieve. As Celine Halioua, Loyal’s founder and CEO, explained: “We’re not making immortal dogs. The way the drug extends lifespan, we hypothesize, is by extending health and thus shortening the rate of aging.”1

The mechanism behind LOY-002 represents what the company describes as more of a “reversal mechanism” compared to their other drugs. While it won’t transform a senior dog back into a puppy, Halioua reports that they’ve “seen a rescuing in age-related functional decline in dogs that have been treated with this drug.”6 This suggests the medication may not only slow further decline but potentially improve certain aspects of health that have already begun to deteriorate.

For large-breed dogs, Loyal’s approach with LOY-001 and LOY-003 targets a different biological mechanism. These medications focus on insulin-like growth factor 1 (IGF-1), a hormone that stimulates cell growth and development5. While IGF-1 is essential during development, its elevated levels in large dogs may contribute to their accelerated aging and shorter lifespans compared to smaller breeds. By modulating IGF-1 levels, these drugs aim to address one of the fundamental factors behind breed-specific longevity differences.

Parallel Research: The Dog Aging Project and Rapamycin Investigation

While Loyal advances its proprietary drugs, another significant research initiative, the Dog Aging Project (DAP), is investigating rapamycin’s potential to extend canine lifespan4. This longitudinal community science project, launched in 2019 with a $29 million grant from the National Institutes of Health’s National Institute on Aging (NIA), faced funding challenges in 2024 but has recently secured a new five-year, $7 million NIA grant to continue its work4.

The DAP’s “Test of Rapamycin in Aging Dogs” (TRIAD) clinical trial is evaluating rapamycin, a drug commonly used as an immunosuppressant in humans after organ transplants, for its potential anti-aging properties in dogs4. TRIAD is described as “the first rigorous test of a pharmacologic intervention against biological aging with lifespan and healthspan metrics as endpoints to be performed outside of the laboratory in any species,” according to the researchers’ methodology review published in February 20254.

This multicenter trial is enrolling dogs at least 7 years old to receive oral rapamycin or a placebo for one year, followed by a two-year observation period4. With a target enrollment of 580 dogs, the study has already included over 180 participants. The new funding will accelerate enrollment with the goal of completing recruitment by the end of 2025 and initiating medication by spring 20264.

The rapamycin study operates under the hypothesis that a once-weekly, weight-adjusted low dose will extend the lifespan of mature or senior dogs—the study’s primary endpoint4. Secondary endpoints include improvements in physiologic health and age-related disease markers such as arthritis and kidney function. Dr. Kate Creevy, the project’s chief veterinary officer and co-principal investigator, emphasized the broader significance of this research: “We all want our dogs to live longer, healthier lives. But the other thing that’s really important about TRIAD is that it’s another terrific example of how relevant veterinary medicine is to human health, and to the basic biology and science that we can learn about in diverse species.”4

The development of effective anti-aging medications for dogs could fundamentally transform geriatric veterinary medicine and the experience of pet ownership. Currently, pet owners often face difficult decisions as their companions age and develop multiple health issues that impact quality of life. If medications like LOY-002 can successfully extend healthy lifespan, they could delay the onset of age-related diseases and provide more quality time between pets and their owners.

One critical aspect of these medications is that they aim to extend healthspan—the period of life spent in good health—rather than simply prolonging life regardless of condition. This approach aligns with what most pet owners want for their aging companions. As Loyal develops its products, the company appears mindful of this distinction. The STAY clinical trial is measuring not just longevity but quality of life according to owner assessment, recognizing that “it doesn’t do anybody any good if their dog lives longer, but they live longer in that period at the end of the life where they don’t feel well, and they’re sick, having all kinds of degenerative and aging diseases.”2

The availability of these medications could also change preventive care practices in veterinary medicine. Rather than focusing solely on treating age-related diseases as they emerge, veterinarians might begin prescribing anti-aging medications proactively to slow the aging process itself. This paradigm shift would represent a move toward treating aging as a modifiable biological process rather than an inevitable decline.

The Future Landscape of Canine Longevity Research

Looking ahead, the field of canine longevity research appears poised for significant growth. Loyal expects that LOY-002 will be available for prescription in early 2025, with LOY-001 and LOY-003 launching in late 20263. If these products demonstrate meaningful benefits in real-world use, they could inspire additional research and product development targeting other aspects of canine aging.

The concurrent advancement of multiple approaches to extending canine lifespan—Loyal’s metabolic and IGF-1 targeting drugs alongside the Dog Aging Project’s investigation of rapamycin—suggests that the field is exploring diverse biological pathways that influence aging. This multifaceted approach increases the likelihood of developing effective interventions and deepens our understanding of the complex biology of aging across species.

Success in extending canine healthspan could also accelerate translation to human applications. Dogs naturally develop many age-related conditions similar to humans and share our environments, making them excellent models for studying interventions that might eventually benefit human health. As Dr. Creevy noted regarding the rapamycin study, if their findings support their hypothesis, it will shed light on rapamycin’s mechanisms at a molecular level, potentially explaining “why rapamycin improves healthy aging, not just that it did,” which would be “directly relevant to people because all molecular pathways are the same.”4

The recent FDA certification of Loyal’s LOY-002 as having a “reasonable expectation of efficacy” marks a significant milestone in the development of interventions specifically designed to extend healthy lifespan in dogs. This regulatory recognition, alongside the ongoing STAY clinical trial and parallel research like the Dog Aging Project’s rapamycin study, indicates growing momentum in the scientific and commercial pursuit of extending quality life for companion animals.

While challenges remain—including completing the regulatory process, scaling up manufacturing, and demonstrating long-term safety and efficacy—the progress to date suggests that veterinarians and pet owners may soon have new options for addressing age-related decline in dogs. These developments reflect a deeper shift in how we conceptualize aging, moving from viewing it as an inevitable process to understanding it as a biological phenomenon that can potentially be modified to improve health outcomes.

As research continues and these interventions move closer to market, they may not only transform how we care for aging pets but also contribute valuable insights to the broader scientific understanding of aging across species. The coming years will reveal whether these promising approaches deliver on their potential to give dogs—and the humans who care for them—more healthy years together.