Dogs don’t live long enough. The family Lab might make it to 14; bigger beasts like Bernese mountain dogs are lucky to see 9. Celine Halioua thinks they deserve a few more years. A scientist, Oxford Ph.D. dropout and former chief of staff at the first venture capital fund focused on longevity-related biotechs, she has spent the last nearly six years building Loyal, a San Francisco startup developing drugs to delay canine aging by targeting metabolic and hormonal imbalances before they become disease. The company’s first beef-flavored longevity pill could hit the market by 2026, potentially extending dogs’ lives—and perhaps someday ours as well.
“I realized that to do this in humans would take billions of dollars, patent issues and trauma, but you could do it in dogs,” says Halioua, 30, whose own dog, Della, is a senior Rottweiler mix that she adopted three years ago.
Loyal doesn’t have any revenue yet, but Halioua is in conversations with the FDA and has cleared early hurdles. Under the agency’s conditional approval program for innovative veterinary drugs, Halioua hopes to get the okay to be on the market with its first drug, which changes the metabolism of senior dogs (ages 10 and up) to mimic a low-calorie diet, which has been shown to extend their lives, next year. Loyal also has both a shot and a pill in the works to lengthen large dogs’ short lifespans by limiting a growth hormone more prevalent in big dogs than small.
Halioua has raised $135 million in equity (and an additional $20 million in venture debt) from top investors that include Bain Capital, First Round, Khosla Ventures and Valor Equity Partners at a valuation of $425 million. The market is potentially enormous: There are nearly 90 million dogs across some 60 million households in the United States, according to the American Veterinary Medical Association. Last year those households spent an average of $1,852 on their pups, a 6% increase over 2023. Loyal’s drugs have the potential to quickly generate hundreds of millions in revenue, should they get the regulatory nod.
That’s why Loyal made the cut for this year’s Next Billion-Dollar Startups list, Forbes’ annual showcase of the 25 companies we think most likely to reach a $1 billion valuation. While artificial intelligence dominates this year’s cohort, Loyal shows that not every successful early-stage startup has to be in AI. “There are some things that are too important to not try. Loyal would be among those—and it seems to have worked out fairly well,” says investor Vinod Khosla, whose firm has invested in at least 10 longevity-related startups and whose own dogs are Newfoundlands, a giant breed that can weigh up to 150 pounds.
While Loyal’s initial market is dogs, it hopes that success there will someday open an even bigger one: people. But that’s a herculean task. Getting a longevity drug for dogs approved might cost $25 million and take five years. Creating one for humans and getting it approved would cost at least $1 billion and take well over a decade. Plus, the human longevity field is notorious for cranks, unproven supplements and fly-by-night clinics.
“People think of longevity and they think snake oil or billionaires trying to live forever and the exaggerated claims. Loyal’s approach is much more nuanced,” Halioua says. Ultimately, she thinks the science will win out. “I think the general public will be blown away when they realize they can go to the vet and get a drug to extend their dogs’ lifespan,” she says. “Then they’ll be like, ‘Why can’t I do this for my grandma?’”
Halioua, an alumna of the 2022 Forbes 30 Under 30 list in Science, grew up in Austin, Texas. Her mother, a Moroccan immigrant with a Ph.D. focused on nutrition, and her father, a German immigrant who worked as a carpenter, had settled there when it was known more for hippies than Teslas. She grew up with a menagerie that included more than 10 cats, multiple dogs and other rescue animals. “We would always have kittens and wild baby squirrels and opossums and turtles and birds with broken wings,” she says.
At the University of Texas at Austin, she started as an art major but soon discovered that her true passion was science. Long hours in the lab and two summers working on neurological diseases at the Sanford Consortium for Regenerative Medicine in San Diego further refined her interest in preventive medicine and longevity.
“It just didn’t make sense to me that we were waiting until these patients were diagnosed with an acutely terminal disease to then try to intervene and help them,” she says. “We don’t wait until our car’s engine is smoking on the highway to do maintenance on it. We do maintenance over time. Why aren’t we doing that with the human body?”
“Everybody was like, ‘It’s not possible.’ I was like, ‘It’s possible.’ ”
In January 2018, while at Oxford pursuing a Ph.D. in the health economics of gene therapy, she joined the Longevity Fund, a VC firm based in San Francisco (then officially dropped out of Oxford in 2019). There, she learned about early research that showed how a single genetic change could extend the life of a roundworm. She was blown away. She later read a seminal 14-year study of caloric restriction in Labrador retrievers from the Purina Institute, which found that cutting how much they ate by 25% could increase their lifespan by nearly two years. She now has a distinctive tattoo on her arm of the head of a Lab, the face of a mouse and the squiggly body of that worm, the trio representing some of the most successful lifespan extension studies that have been done. “This biology had existed for decades,” she says. “I had become extremely fascinated, somewhat obsessed, with it, but nobody had ever turned it into a medicine.”
She found a like-minded collaborator in 2019: investor Greg Rosen, now a partner at BoxGroup, who had been thinking about creating a dog-cloning startup based on some research he’d seen in South Korea. Halioua pitched him on an adjacent idea at Philz Coffee on Folsom Street in San Francisco. “She said, ‘Look, I know nothing about dog cloning, but all my work is on longevity. What about a dog longevity business?’ ” Rosen says. “We spent the next six months together hashing it out. ‘Is this remotely technologically feasible, and can we even raise money for it?’ ”
In January 2020, Loyal launched with $4.5 million in seed funding and a singular goal: to develop the first drug for life extension. “Everybody was like, ‘It’s not possible,’ ” Halioua says. “I was like, ‘It’s possible.’ ”
Her first idea was to develop a one-time gene therapy injection to slow aging in large dogs by inhibiting a growth hormone. But gene therapy is ridiculously expensive—a problem for cash-paying dog owners—and a one-time shot also raised the risks of something going wrong. “I wouldn’t give it to my dog if it had a one in 1,000 chance of killing them,” she says.
She went back to the drawing board and decided to focus on more traditional shots and pills that are cheaper and safer because the drugs don’t induce a permanent genetic change. While the company hasn’t set prices yet, she figures they could be somewhere between the cost of a heartworm medication and arthritis injections, or less than $150 a month. “I don’t plan on price gouging or anything,” she says.
Her timing was impeccable: In 2019, the FDA had expanded conditional approval for certain innovative animal medicines, allowing drugmakers like Loyal to sell their medications after demonstrating their safety and ability to manufacture them but before they’d fully proven their efficacy. They then have five years after approval to demonstrate that the drug works with continued clinical studies.
This February, Loyal passed a significant milestone toward conditional approval of its first drug, which mimics caloric restriction, when the FDA’s Center for Veterinary Medicine said the company had demonstrated it had a “reasonable expectation” of effectiveness. Halioua was attending a wedding in Panama with her boyfriend (now fiancé) when she got word from her regulatory team over Slack. Still in the pool, she star-ted screaming when she heard the news. The other guests “thought ‘this loud American,’ ” she says with a laugh. “Then they realized I was celebra-ting. I think they thought I got proposed to and brought Champagne.”
At the Barlow Trail Veterinary Clinic in Sandy, Oregon, near Mount Hood, Dr. Jaime Houston has enrolled 105 canines in Loyal’s study of its first therapeutic, which helps regulate old dogs’ metabolisms to help them live longer. “Most of my clients who have older dogs, I discuss Loyal with them, and nine out of ten want their dogs to be in the study,” Houston says.
Loyal dosed its first patient, an 11-year-old whippet named Boo, at the Animal Hospital of Dauphin County in Harrisburg, Pennsylvania, in December 2023. The double-blind, placebo- controlled study, which is expected to last around five years, has now enrolled 1,300 dogs at more than 70 veterinary clinics across the country. It’s the largest animal clinical trial ever conducted.
Halioua has a second drug in the works focused on large dogs. The pill version is based on a molecule created by publicly traded Crinetics Pharmaceuticals that was originally part of a human drug to treat problems with too much growth hormone. “They had this hypothesis about large dogs, and we had this clinical-class compound we weren’t going to do anything with,” says Crinetics cofounder and chief scientific officer Steve Betz. Better yet, from Loyal’s perspective, it had already been tested—and shown to reduce growth hormone—in rats and dogs.
Eventually, Loyal’s work with dogs might show the way for human longevity medications. But in the meantime, Halioua is convinced that the drugs will be a game changer for the millions of Americans with older dogs they wish had more time. “I’ve never really had any anxiety about us being wrong,” she says. “This is where the world is going to go.”
