The Dog Longevity Drug: What LOY-002 Is and Where FDA Review Stands

You may have seen the headlines about a pill that could help your dog live longer, especially if she's gray around the muzzle and sleeps through the mail carrier now. It's LOY-002, the dog longevity drug from a San Francisco company called Loyal. It's further along than most people realize, and it also isn't something your vet can prescribe yet.

Let's start with what it is, who it's for, where its review stands as of October 2026, and what we know about its side effects.

What the dog longevity drug LOY-002 actually is

LOY-002 is a once-daily prescription pill for senior dogs. Loyal says it works on metabolism: the goal is to improve insulin sensitivity and lower insulin levels, since both tend to drift the wrong way in older dogs and are tied to a lot of age-related disease. ^[1]

It's not about getting more years, it's about getting more healthy years. If FDA approves it, it would be the agency's first approval of a drug for lifespan extension in any species, dogs or people. ^[2]

This is a drug and not a supplement. That's why it has to pass FDA's animal drug process, and why it would come from your vet with a prescription and not from a store shelf.

Which dogs the dog longevity pill is meant for

LOY-002 is aimed at dogs 10 and older that weigh at least 14 pounds. ^[1] Loyal's page for vets puts the top of the range at 179 pounds, so past that 14 pound minimum, size isn't much of a limit. ^[3]

Loyal has two other drugs in the pipeline for large dogs, because large and giant breeds tend to have shorter lives. LOY-001 is an injection for dogs 7 and older that weigh 40 pounds or more. LOY-003 is a once-a-day pill for dogs 5 and older at 60 pounds or more. Both go after IGF-1, a growth signal linked to the shorter lifespans of bigger breeds, and both are a few steps behind LOY-002. ^[1]

Wondering what her age means in human years? Our dog years to human years chart and calculator shows what 10 means for a dog her size.

How FDA conditional approval works for a dog drug

Most animal drugs only get full approval once they've shown they work. Conditional approval is a faster route FDA allows for a drug that meets an unmet need when proving effectiveness takes a long or complex study. Waiting to see if a pill helps dogs live longer is about as long as a study can get.

There are three big sections a company has to clear:

• Reasonable expectation of effectiveness (RXE): preliminary evidence that the drug will likely have the desired effect.
• Target animal safety (TAS): complete safety testing in the type of dog it's meant for.
• Manufacturing (CMC): proof that it can be made at the same quality, batch after batch.

A conditionally approved drug can be marketed for up to five years while its full effectiveness study is finished. If that study doesn't show it works, or is never completed, the drug has to come off the market. ^[4]

Where the FDA review of LOY-002 stands

Two of the three sections are done. FDA accepted the effectiveness section in February 2025 and the safety section in January 2026. ^{[5] [6]} Manufacturing is the last big piece, and Loyal's own site still lists it as in progress when we checked on October 7, 2026. ^[7]

So no, it isn't approved yet. When the safety section went through, dvm360 reported that the manufacturing section was expected to be reviewed in 2027. ^[2] Dates have slipped before. Back in early 2025, Loyal hoped to wrap up the manufacturing and safety sections by the end of that year. ^[5] If you're planning around a date, check the news again first.

What's known about LOY-002 side effects

Less than you'd probably like, but what's public so far is reassuring. In the standard safety study, dogs got 1, 3 and 5 times the intended dose, and Loyal reports no clinically significant adverse events at those doses. ^[8] The safety package also had field data from over 400 dogs in the ongoing STAY study, some treated for up to a year, including dogs with other health problems and dogs on other medications. ^[2] FDA agreed the data supports the drug's safety for the way it's meant to be used. ^[6]

What you won't find yet is a list of side effects with percentages, the kind you'd see on a package insert. Loyal says it will share more data as launch gets closer, and FDA publishes a summary of the evidence (a Freedom of Information summary) when a drug is approved. ^{[3] [4]} Until then, there's no public answer to how often any particular side effect shows up.

The STAY study is what will show if it works

STAY is the big one. It's a double-blind, placebo-controlled study of about 1,300 dogs at 70 vet clinics across the US, and neither the owners nor the vets know which dogs get the real pill. ^{[9] [6]} The first dog was dosed in December 2023, and the study runs about four years. ^[5] It tracks quality of life along with lifespan, since a few extra months don't mean much if she spends them feeling bad. ^[10]

Enrollment is full, so you can't sign your dog up now. ^[9] Full approval depends on these results. Conditional approval, if it comes first, would mean FDA thinks the drug is safe and likely to work, not that it's been shown to add years.

How much the dog longevity drug might cost

Loyal hasn't announced a price. CEO Celine Halioua has said the company wants to keep it at an accessible price point. ^[11] GoodRx has reported it may sell for under $100 a month, which is a guess at this stage, not a price list. ^[12]

Whatever the number turns out to be, it'll be a prescription drug, so it would start with a conversation at your vet's office.

What you can do for an older dog right now

You don't have to wait on FDA to give her a better shot at a long, good life. The best-proven step is a boring one: keep her lean. In a lifetime study of 48 Labrador retrievers, the dogs fed 25% less than their littermates lived a median of 13 years, against 11.2 for the others. That's about 1.8 extra years. ^[13] That study was about how much food they got, not a pill, and it's still one of the strongest results we have on dog lifespan.

Regular checkups matter more as she gets older too, because a lot of the changes that shorten a dog's life start quietly in middle age. We went through those in our post on when a dog is middle-aged.

And if you like the research side, the Dog Aging Project has more than 50,000 dogs enrolled. Its TRIAD trial is testing rapamycin, an older generic drug, in dogs over 7 that weigh at least 44 pounds, and owners commit to three years of visits. ^[14]

Questions to ask your vet about the dog longevity drug

If you're curious about LOY-002 for your dog, bring these to her next visit:

• Would she fit the criteria for it, given her age, weight and health?
• How would it fit with the medications and supplements she takes now?
• What would you want to check before she started, and how often after?
• What's worth doing for her now while it's still in review?

Until it's approved, the only dogs getting LOY-002 are the ones in Loyal's study, so be wary of anything sold online as a longevity drug for dogs. Unapproved products reach dog owners fast, as we saw in our post on what peptides for dogs really means.