Loyal

Loyal is a San Francisco biotechnology company, incorporated as Cellular Longevity, Inc., that develops drugs intended to extend the healthy lifespan of dogs. It was founded in 2019 by Celine Halioua, who had previously worked at the Longevity Fund, the venture firm started by Laura Deming. Its interest for geroscience is procedural as much as pharmacological: the veterinary arm of the US Food and Drug Administration will entertain "extension of lifespan" as a drug indication, and its human counterpart will not.

§Overview

The company's premise is that dogs sit closer to people than laboratory mice do and closer to a marketed product than any human aging drug. Companion dogs share human households, diets and sedentary habits, develop cancer, osteoarthritis and a cognitive decline syndrome resembling dementia, and are genetically diverse in a way inbred mouse colonies are not. They also die within about a decade, which is what makes a survival endpoint affordable: a trial powered on how long the animals live reads out in years rather than the decades a human equivalent would need, the arithmetic that pushed the proposed TAME trial in people onto a composite endpoint of age-related disease instead.

Loyal is small next to the best-capitalized longevity companies such as Altos Labs, and runs three programmes designated LOY-001, LOY-002 and LOY-003.

§History

1. 2019
   Founded
   Celine Halioua incorporates Cellular Longevity, Inc., trading as Loyal, to develop drugs for canine aging.
2. 2021–2023
   Large-dog programme
   The company builds its first programmes around reducing IGF-1 in large breeds, on the reasoning that breeding for size raised the hormone and shortened their lives.
3. 2023
   First effectiveness finding
   FDA's Center for Veterinary Medicine concludes that Loyal's data meet the reasonable expectation of effectiveness standard for a lifespan indication in large dogs — one requirement of a conditional approval, not an approval.
4. 2023–2025
   STAY study enrols
   A randomized, placebo-controlled trial of LOY-002 in senior dogs recruits through veterinary clinics across the United States, powered on how long the enrolled animals live.
5. 2025
   Second effectiveness finding
   The agency reaches the same reasonable-expectation conclusion for LOY-002, the programme the company expects to reach the market first.

Loyal attracted little public attention until late 2023, when the first FDA finding drew wide press coverage, some of it describing the milestone as an approval. It was not. The company has since said it intends LOY-002 to reach conditional approval first, which requires completing the rest of the application. As of mid-2026 no Loyal product is on sale, conditionally or otherwise; the file is an active one and may have moved since.

§Research programme

§The large-dog programmes

LOY-001 and LOY-003 target the same axis in large and giant breeds, the first as a long-acting injection given by a veterinarian and the second as a daily tablet. The rationale is the company's own reading of canine genetics. Within the domestic dog, body size correlates strongly with a shorter life, and large breeds appear to age faster rather than starting from a worse baseline.¹ A single variant near the IGF1 gene is a major determinant of small size across breeds,² and large breeds carry higher circulating insulin-like growth factor 1 than small ones. Loyal's proposition is that lowering IGF-1 in a large dog toward the level typical of a small one should slow that acceleration.

The underlying pathway has a strong pedigree: reduced insulin and IGF-1 signalling extends lifespan in nematodes, flies and mice, from the daf-2 mutants characterized by Cynthia Kenyon to growth-hormone-deficient dwarf mice, and nutrient sensing recurs throughout the Hallmarks of aging. The step from that literature to large dogs is an inference. The size–lifespan correlation is well documented; that IGF-1 causes it is a hypothesis, and no published trial has shown that lowering IGF-1 lengthens a dog's life.

§LOY-002 and the STAY study

LOY-002 is a daily tablet for senior dogs above a minimum weight, which the company describes as acting on age-related metabolic dysfunction rather than on the growth axis, framing the goal as extending healthy life rather than postponing death — the canine version of Compression of morbidity. It is being tested in the STAY study, a randomized, double-blind, placebo-controlled trial enrolling roughly a thousand older dogs through veterinary practices across the United States and powered on how long the enrolled animals live. No result has been published.

Nothing comparable exists in human healthspan research: a placebo-controlled trial in a naturally aging, free-living mammal population powered on how long the animals live, rather than on a movement in an Epigenetic clocks reading or another unvalidated surrogate.

§The regulatory route

A drug for dogs is approved in the United States through a new animal drug application reviewed by the Center for Veterinary Medicine. The application is assembled in technical sections — effectiveness, target animal safety, manufacturing chemistry, labelling — each reviewed as it is submitted. Full approval requires substantial evidence of effectiveness, the same statutory phrase used for human drugs.

Alongside it sits conditional approval. Created for minor species and minor uses and extended in 2018 to drugs for major species addressing serious conditions or unmet needs where a conventional effectiveness study would be particularly difficult,³ it lets a sponsor market a drug by prescription for up to five years while assembling the evidence full approval demands. The entry bar is lower: a reasonable expectation of effectiveness rather than substantial evidence. Loyal's argument is that a canine lifespan study is exactly what the provision was written for.

What the FDA agreed to, precisely

In late 2023 the Center for Veterinary Medicine concluded that Loyal's data met the reasonable expectation of effectiveness requirement for a lifespan indication, and reached the same conclusion for LOY-002 in 2025.⁴⁵ That is a finding on one technical section of a conditional-approval application. It is not a conditional approval, not a full approval, and not a finding that either drug extends any animal's life. Safety and manufacturing sections must still be accepted before a conditional approval can be granted.

The contrast with human medicine is the point. No regulator recognizes aging as an indication in people, no surrogate marker of aging has been qualified for registrational use, and a human survival trial would run for decades. That is why Calico Life Sciences and its peers develop drugs for named diseases and argue the biology generalizes, why Nir Barzilai and colleagues have spent years arguing a composite of age-related events into acceptability as an endpoint, and why the XPRIZE Healthspan competition had to invent its own. Veterinary medicine reached a lifespan indication first not because the science is further along but because the arithmetic is easier.

§Dogs as a model, and its limits

The academic version of the same bet is the Dog Aging Project, a separate effort based at the University of Washington and founded by Daniel Promislow and Matt Kaeberlein with colleagues at other institutions. It runs an open-science cohort of tens of thousands of companion dogs whose owners contribute health data,⁶ and within it TRIAD, a randomized placebo-controlled trial of Rapamycin in companion dogs.⁷ An earlier ten-week pilot from the same investigators reported improved cardiac measures in two dozen middle-aged dogs.⁸ The project is academic and tests a generic drug; Loyal is a company developing proprietary compounds toward a marketed product. Coverage frequently confuses the two.

Neither is the first intervention to move canine lifespan. A long-running paired-littermate study in Labrador retrievers found that dogs fed a restricted diet lived roughly two years longer than their freely fed siblings,⁹ which remains the best-supported way to extend a dog's life and the same dietary restriction result that anchors the rodent literature.

A dog result is not a human result

Every claim in this area concerns dogs. Should STAY report a survival benefit, it would establish that a drug extended lifespan in one population of companion dogs; a human programme would still begin again at first-in-human safety, against an indication no regulator accepts. The natural human experiment on the IGF-1 axis is instructive: people with growth hormone receptor deficiency show strikingly little cancer and diabetes without a demonstrated increase in lifespan.¹⁰

§Funding and business model

Loyal is venture-funded, has raised successive private rounds since 2019, and publishes no financial statements. Its commercial model is a prescription drug sold through veterinarians and paid for out of pocket, since pet insurance rarely covers preventive medication. A daily tablet for the rest of a senior dog's life is a recurring cost, so uptake would sort by household income along the lines the human access debate anticipates — with the wrinkle that the patient cannot consent.

§Reception

Specialists have generally welcomed the regulatory precedent while being careful about what it shows. A survival-powered trial in a free-living mammal is better evidence than most of what the field produces, including the mouse work behind Senolytics. Veterinary approval is also a real bar rather than a supplement pathway: the agency reviews safety, manufacturing and effectiveness.

The criticism runs in three directions. The press has repeatedly reported the effectiveness findings as approvals, a confusion the unfamiliar terminology invites and one that flatters the company however it arises. The IGF-1 rationale rests on a correlation whose causal reading is unsettled. And conditional approval, by design, permits sale before effectiveness is established, so owners could pay for years for a drug whose benefit remains unproven. That trade-off is deliberate, but it lands differently in a mass market of anxious owners than in a veterinary specialty setting.

Is the veterinary route a shortcut to human geroscience?

Proponents argue that a positive canine survival result would be the first controlled demonstration that a drug slows aging in a large outbred mammal sharing the human environment, and would pressure regulators to define a human aging endpoint. Skeptics reply that dogs metabolize drugs differently, and that the human bottleneck was never evidence from another species — it is that "aging" has no legal status as a condition to treat.

§Outlook

The events worth watching are narrow: whether the remaining technical sections are accepted, whether STAY reports a survival difference and how large, and whether a conditional approval converts to a full one inside the five-year window rather than lapsing. A drug marketed for years and then withdrawn for want of evidence would damage the argument that lifespan can be an indication more than never having tried.

The most useful outcome may be a negative one. A well-run placebo-controlled trial reporting no survival effect would be the first clean null for a candidate geroprotector in a naturally aging mammal outside the laboratory, and the field has produced far more positive mouse results than it has learned to interpret. What the FDA has conceded so far is that the question can be asked, not that anyone has answered it.

§See also

• Rapamycin
• Geroscience hypothesis
• Healthspan
• Aging biomarkers
• Metformin and the TAME trial
• Calico Life Sciences
• XPRIZE Healthspan
• Compression of morbidity

§References