A canine health startup called Loyal has now raised more than $250 million to develop drugs that could help dogs—and perhaps one day humans—live longer, healthier lives. 

The company on February 11 announced it had raised $100 million in Series C funding as it pursues FDA approval of LOY-002, a beef-flavored daily prescription pill designed to extend the healthy lifespan of senior dogs. The drug mimics some of the effects of a calorie-restricted diet in addressing age-related metabolic issues without requiring pet owners to cut their dogs’ food supply or curbing canine appetites.  

“People do not want their dogs to not have food motivation, because that’s how you train dogs,” says Loyal founder and CEO Celine Halioua. “How we domesticated dogs was sharing meals with them; losing that can actually really impact the dog-human bond.” 

But, of course, people do want to share that bond longer than the typical canine lifespan allows. Halioua started Loyal in late 2019 after a stint as chief of staff at The Longevity Fund, a lifespan-focused investment fund founded by Laura Deming and an early backer of Loyal. She says she realized that dog longevity drugs could one day lead to similar treatments for humans, since the species are similar in many ways, and are easier to test, since dogs’ short lives mean tests of lifespan extension can be run in a shorter amount of time. And as a dog lover—a recent interview with Fast Company also included Halioua’s freshly adopted Rottweiler, Wilma—she also saw the potential market among owners and pets. 

“It felt like a really tractable way to work on a problem that everyone cares about, which is having too little time with the dogs you love,” she says. 

LOY-002 is one of three canine longevity medications under development by the company, and Halioua says she’s hoping Loyal can submit the final requirement for the FDA’s expanded conditional approval of the drug this year. That would likely start a roughly six-month review process of what would be the first FDA-approved lifespan extension drug for any species. And its progress comes as interest rises overall in the potential of developing medical treatments that can help humans as well experience longer and healthier lives. 

“When I started pitching The Longevity Fund in 2013, it was a niche concept and people laughed me out of their offices,” Deming tells Fast Company in an email. “Now it’s a legitimate category of investment.” 

Loyal’s Series C backers include Age1, a new longevity-focused VC firm cofounded by Deming and Alex Colville, as well as Baillie Gifford and other existing investors in the company, which had previously raised more than $150 million in investments.  

“Aging is something that really affects everybody—every human and every dog on the planet  experiences aging,” Colville says.  “And I think that’s something that’s really unique about it as an opportunity and a space to work in.” 

Already, LOY-002 has met two of three milestones for FDA approval, known as the “target animal safety” and “reasonable expectation of effectiveness” sections of its conditional approval application. The final milestone involves demonstrating that the drug can be consistently manufactured at scale, Halioua says. The drug will likely be labeled for use by dogs at least 10 years old weighing at least 14 pounds, she says. Dosing, and thus costs, will depend on animal size, but Halioua says she’s optimistic the average dog will be able to take the drug for less than $100 per month.  

The company announced last July that it had completed enrolling dogs in a study it calls STAY, designed to test the effectiveness of LOY-002, which Halioua says is the largest-ever animal health clinical trial. Loyal has enrolled roughly 1,300 dogs in the study through 72 veterinary clinics, and Halioua says she’s hoping they’ll find that the drug confers at least one healthy to participants.  

Loyal also has two other dog drugs, a vet-administered injection called LOY-001 and a daily pill called LOY-003, in the works. Though Halioua says the company hasn’t publicized the exact biological mechanisms beyond the drugs, she says would look to extend lifespans of larger dogs by targeting a growth hormone that’s correlated with a shorter life, with big dogs usually living a shorter time than their smaller counterparts.  

“Once the dog is fully grown, you can then reduce the levels of growth hormone to hopefully extend their healthy lifespan and kind of compensate for the historical genetic issue that we gave them when we selectively bred for size,” says Halioua. 

If all goes well, those drugs could launch a year or two after LOY-002, she says. And if Loyal’s drugs prove helpful to dogs, they could one day lead to similar treatments for humans. 

“If we’re able to do something helpful for dogs, I think we’re going to learn a lot about how to do something helpful for humans, too,” says Halioua.