A daily pill meant to help older dogs live longer and healthier lives has cleared two of the three technical reviews the US Food and Drug Administration (FDA) requires for conditional approval, according to recent reports on the company behind it, Loyal1. If it passes the last one, it would be the first FDA-approved drug for extending lifespan in any species1. The remaining step, a review of how the pill is made, is expected in 20271. Whether the pill actually adds years to dogs’ lives has not been shown: results from its large trial have not been released1.
What happened
Loyal’s pill, known in the lab as LOY-002, is a beef-flavored daily tablet for senior dogs2. It is aimed at dogs aged 10 and older that weigh at least 14 pounds1. Rather than treating one disease such as arthritis or cancer, it is meant to target aging itself2.
The FDA’s review of animal drugs is split into separate technical sections: effectiveness, safety in the target animal, and chemistry and manufacturing. The agency reviews and accepts each one in turn3. Two of the three sections for Loyal’s pill have now been accepted1, which Woman’s World described as putting the company “two-thirds of the way” to conditional approval2.
“Since founding Loyal six years ago, my goal has always been to get the first drug FDA approved for lifespan extension,” chief executive Celine Halioua said1.
What the FDA has accepted so far
The first step came in early 2025. The FDA’s Center for Veterinary Medicine accepted what is called the “reasonable expectation of effectiveness” section4. In plain words, regulators agreed the case that the pill could work is plausible enough to support the conditional pathway. It is not an approval3.
The second step came in January 2026, when the FDA signed off on the target animal safety section1. That package included a standard study giving dogs one, three and five times the normal dose, which reportedly turned up no clinically significant side effects, plus field data from more than 400 dogs1. Woman’s World reported that this data confirmed the drug is safe for its intended use2.
What is left is the manufacturing section. Loyal expects the FDA to review it in 2027, after which the company could seek expanded conditional approval1.
How the pill is meant to work, and where sources differ
Most accounts say the pill targets metabolic problems that come with age. Loyal describes it as copying the effects of eating less, an idea called “caloric restriction mimicry,” on the theory that this could slow aging1. One overview says the company has described its focus as age-related metabolic dysfunction, including how well the body responds to insulin3.
One report instead says the pill works by lowering the effects of IGF-1, a growth hormone linked to faster aging in larger dogs2. Another source says that IGF-1 approach belongs to Loyal’s other programs, LOY-001 and LOY-003, which target large and giant breeds, and not to the senior-dog pill3. Biohack could not settle the difference from the sources available.
Loyal’s director of veterinary medicine, Brennen McKenzie, told Newsweek the company’s aim is prevention:
“But we also need preventive tools to slow down the decline caused by aging and delay the onset of those problems. That’s where therapies like the ones Loyal is developing come in.”
That quote was reported by Woman’s World2.
What it does not show yet
The key question, whether dogs given the pill live longer, is still open. Results from the main trial are not out, so how many extra years the pill could add remains unproven1.
That trial is the STAY study. It is double-blind and placebo-controlled: half the dogs get the pill and half get a dummy pill, and neither owners nor vets know which is which2. It has enrolled about 1,300 dogs at 70 veterinary clinics, and the company calls it the largest clinical trial in veterinary history1. Dogs live at home with their families, owners give the pill daily, and dogs come in for scheduled check-ups3.
Conditional approval is built for exactly this gap. Congress created expanded conditional approval for animal drugs in 2018. It lets a company sell a drug once safety and manufacturing quality are shown and benefit looks reasonably likely, while it keeps gathering the stronger evidence needed for full approval3. A conditionally approved animal drug must be renewed every year and cannot stay in that status indefinitely. After a legal time limit, the company either wins full approval or the product comes off the market3.
Who is behind it
Loyal was founded in 2019 by Celine Halioua2. Its legal name is Cellular Longevity, Inc.3. Reports of how much money it has raised differ. Woman’s World and a 2025 report on a $22 million funding round put the total at more than $150 million24, while a pet-health blog lists more than $250 million in private funding5.
Much of what is publicly known about the pill’s progress comes from the company’s own announcements, relayed by news outlets. The safety findings described above have not been published as a full study in the sources Biohack reviewed.
How it fits the field
Loyal reached the same effectiveness milestone earlier for its large-breed program. It announced in late 2023 that the FDA had granted a reasonable expectation of effectiveness for LOY-001 in large-breed dogs3. Bigger dogs tend to live shorter lives than small ones; large breeds like Great Danes or Labradors typically live 8 to 12 years6.
A separate, academic effort is testing rapamycin, a drug already approved for people, in older pet dogs. The Dog Aging Project, co-founded by Daniel Promislow and Matt Kaeberlein, runs a trial called TRIAD3. Rapamycin has no FDA approval for canine aging3. One tracker lists TRIAD’s target at 580 dogs, with more than 180 enrolled, funding from a $7 million federal research grant, and results expected by 20295.
Supporters see wider stakes. Some longevity commentators argue that an approved lifespan drug for dogs could push regulators to think of aging as something that can be treated in people too6. Dogs age roughly seven times faster than people, so longevity treatments can be studied in years instead of decades2. Those are hopes, not findings.
What to watch next
- The manufacturing review. Loyal expects the FDA to review this last section in 20271. Woman’s World reported that the earliest a prescription could reach vets is next year2.
- Trial results. Data from the STAY study on whether treated dogs live longer or stay healthier than dogs on the dummy pill1.
- The renewal clock. If conditional approval is granted, it must be renewed each year while Loyal works toward full approval3.
Halioua has called the progress “one step closer to the first-ever FDA-approved drug for lifespan extension”2. Whether the pill does what it is meant to do will depend on the trial results that are still to come.
