The loss of a beloved pet is a heartbreaking event, and while inevitable, there might soon be a way to delay that grief among dog owners, at least for a little while.

A new drug is currently in the works that could one day extend the lifespan of some large canine breeds.

The medicine has been developed by the veterinary biotech company, Loyal for Dogs, and while it still needs to undergo clinical trials, officials at the United States Food and Drug Administration (FDA) have said in a letter to the company that its initial data is "sufficient" to show "a reasonable expectation of effectiveness," according to a copy of the letter supplied to The New York Times.

"Today, I'm so proud to announce that Loyal has earned what we believe to be the FDA's first-ever formal acceptance that a drug can be developed and approved to extend lifespan," writes Loyal's founder and CEO Celine Halioua in a press release on November 28.

"In regulatory parlance, we have completed the technical effectiveness portion of our conditional approval application for LOY-001's use in large dog lifespan extension."

LOY-001 is the name of the first version of the drug, which is targeted at dogs 7 years of age and older, weighing at least 40 pounds (18 kilograms). It comes as an injection that can be given to dogs every three to six months by vets.

At the same time, scientists at Loyal are also working on two other versions, called LOY-002 and LOY-003, which would be taken as daily pills. LOY-003 is designed for all older dogs except for the smallest breeds.

All versions of the drug work by limiting the power of a growth-related hormone, called insulin growth factor-1 (IGF-1), which as well as contributing to growth is linked to aging and longevity in animals like roundworms, fruit flies, and mice.

Whether those associations also extend to dogs is unclear, but there is reason to suspect that high levels of IGF-1 may accelerate aging in canines.

Compared to smaller dogs, like Chihuahuas – which live between 14 and 16 years on average – larger dogs like Great Danes only live between 7 and 10 years.

Larger dog breeds also tend to show highly elevated levels of IGF-1 – up to 28 times as high as smaller dogs. In canines, this hormone drives cell growth and is part of what allows larger dog breeds to grow so large.

But at older ages, this hormone may have serious downsides. While no one hormone is likely responsible for all the processes of aging, this is one of the most well-studied pathways in animal models and an avenue worth exploring further.

An unpublished observational study from Loyal, which looked at the health of more than 450 large dogs, ultimately found that canines with lower insulin levels experienced reduced frailty and a higher quality of life.

After seeing these results and reading through more than 2,300 pages of Loyal's technical information, officials at the FDA have confirmed the potential for LOY-001 to extend dog lifespans.

Now that they have a validated proof of concept, Halioua and her team hopes to receive conditional approval for LOY-001 by 2026. This is a fast-tracked FDA authorization that would make the drug available on the market even while evidence is still being collected from clinical trials.

Halioua told The New York Times that she and her team are aiming to extend dog lifespans in clinical trials by at least a year.

Whether the company can achieve that result remains to be seen.

"If it proves true that it extends life span, I'm only interested in that if the period of life that is extended is good quality life," Kate Creevy, the chief veterinary officer of the Dog Aging Project, told The New York Times.

"I don't want to make my dog live an extra two years in poor health."

Experts at the Dog Aging Project are also working on a potential life-extending drug for canines, called rapamycin, which shows anti-aging effects in flies, worms, and rodents.

Rapamycin works by blocking a molecule called mTOR, which regulates cell proliferation and death. It is a hot target in drug research at the moment.

Scientists aren't just interested in trialing these types of drugs for the sake of dogs. Such pathways could also be relevant to human health.

To date, the FDA has yet to approve any longevity drug for animals or humans. While some experts are concerned that adding years to dog lives may not be in our pets' best interests, others argue that because we have bred dogs to have shorter lifespans, we owe it to our pets to try to improve their health and extend their lives in any way we can.

Loyal is currently recruiting more than a thousand senior dogs for clinical trials starting in 2024/2025.