The Secret to Longevity Lies in Dogs

Episode 37 of S³

Loyal is creating drugs for dogs to live longer & healthier lives. Last Friday they raised an additional $45M to bring their first longevity drug LOY-1 to market. We filmed with CEO and Founder Celine Halioua the next day for Episode 37 of S³!

Note: The following is not written by me, but instead my friend, the incredible Niko McCarty! Niko is the founding editor at Asimov Press and bio-genius who takes the times to explain cutting edge bio to folks like me — I highly recommend checking out his Highlights on Twitter/X. I asked him to do a write up on Loyal in relation to this episode, so here it is!

For Episode 37 of S³, Jason features Loyal. Jason asked me to give some context on the company, what they're doing, and what I think about them.

My verdict: I think they’re already one of the most important biotech companies of the 21st century. Here’s why.

I’m glad Jason is featuring Loyal for two reasons.

  1. Biotechnology is under-covered relative to its importance in the world.

  2. Loyal is setting the stage for the F.D.A. to one day approve a drug that targets the only condition that affects everyone: aging.

Loyal was founded in 2019 by then 24-year-old Celine Halioua. Celine went from a PhD at Oxford to work with Laura Deming at the Longevity Fund. Later, Celine convinced Laura to invest in a new startup: Cellular Longevity (of which Loyal is a part).

In less than 5 years, the company has achieved two major milestones:

  1. "The first longevity clinical study design supported by the FDA."

  2. Earned the first formal acceptance from the FDA “that a drug can be developed and approved to extend lifespan.”

More on these later.

For now, it's important to know that the FDA doesn’t currently approve drugs for lifespan extension; only for specific diseases. If Loyal makes a drug that extends lifespan in dogs, it could also open up a regulatory path to approval for drugs that do the same for humans.

(Side note) Even if Loyal succeeds in bringing longevity drugs to market for people, they will not stop making drugs for dogs. In other words, dogs are not “just” a route to humans, but will remain a part of the company's portfolio forever.

There are good reasons to make anti-aging drugs for dogs, and then work up to humans. The first reason is that it’s difficult to study life-extending drugs in people because we live a long time, and the studies would take too long and therefore cost too much money.

The second is that there’s already a ton of data on aging on dogs. The Dog Aging Project includes data from ~30,000 dog owners on “genetic and environmental factors affect dogs’ aging processes,” wrote Ashlee Vance in Bloomberg.

And a third reason, Deming once said, is that a “dog-first approach” could help people get used to anti-aging drugs. If we give pills or injections explicitly designed for aging — rather than a specific disease — to our animal friends, the drugs could more easily go mainstream.

And Loyal is on track to make that happen. They've raised $125M+ so far. A $45M Series B was announced last week. The latest funding is expected to help the company “bring the first FDA-approved lifespan extension drug to market in 2025,” said Halioua.

The company has three drug “assets” in the pipeline. All of these drugs have codenames, and I don't know what the specific molecules are. But they are called LOY-001, 002, and 003. I’ll focus on LOY-001 and LOY-002 in this thread.

But first, a note about dog aging: There's an inverse relationship between a dog’s size and lifespan. Big dogs live ~7-10 years. Chihuahuas live 14-16 years. Big dogs also have up to 28x more IGF-1, a protein growth hormone that tells cells to divide, compared to small dogs.

LOY-001 works by reducing IGF-1 levels in large dogs. It is an injectable given to the dog by a veterinarian every 3-6 months. Conditional approval is expected in 2026. (LOY-003 also targets IGF-1, but is instead given as a daily pill.)

In November, Loyal achieved “the most important milestone in the history of longevity biotech,” in part based on data from LOY-001, according to Deming. The milestone? The “FDA’s first-ever formal acceptance that a drug can be developed and approved to extend lifespan.”

This milestone toward "conditional approval" took ~4 years of work. The company assembled a “2,300+ page technical section" that includes observational data on aging in 451 dogs and interventional data on LOY-001. The FDA looked and said, “Seems legit."

This doesn't mean that Loyal can sell LOY-001. The company still needs to complete safety and manufacturing requirements. The company will also run larger trials to apply for full approval. But soon, vets may be able to prescribe LOY-001 to extend the lifespan of large dogs.

When Loyal first started, even serious investors in the longevity field doubted that the FDA would ever approve drugs for aging. Laura Deming, a lead investor, recalled an early discussion with Halioua on the 80,000 Hours podcast, saying:

Loyal made the bet that if they tried to compile evidence from the literature about the aging field, and present it in a way that is scientifically fair to the...FDA, that they would consider this literature...and...lifespan extension as a claim.

I think it was a risk, and it took an act of imagination to make that step. was great credit to the FDA...that they actually considered this indication.

This is something that I thought was impossible, like, five years ago. And the company got it done in four."

Laura Deming

The other major milestone that Loyal has achieved is called "protocol concurrence." In March 2023, Loyal announced that the FDA had looked at their designs for a longevity study with LOY-002 and agreed to validate whether the drug extends canine lifespan and healthspan.

“In other words, if our study demonstrates that our dog longevity drug extends healthy lifespan, those results will be sufficient to support bringing the drug to market for dogs across the country," the company wrote in a blog.

On the back of this FDA decision, Loyal launched a pivotal study with LOY-002, a daily pill designed to extend healthy lifespan of dogs over 14lbs and 10+ years of age. The study will enroll 1,000+ dogs in a randomized, placebo-controlled study. It will take 4 years.

The trial, called STAY, is “likely one of the largest veterinary clinical trials ever run,” according to a company blog. And the first dog (named Boo) has already been dosed!

Loyal is already pursuing "conditional approval" for LOY-002 based on existing data from a smaller trial. The goal of the large trial, then, is to collect the data needed for a full approval later on. (Conditional approval means the drug can only be sold for 5 years.)

So again, Loyal is significant because they are making it possible to bring longevity drugs onto the market. They are collecting data in dogs to convince the FDA that age, and not just specific diseases, should be a thing that we can design and market drugs for.

That's huge.

But despite the company's success, the first anti-aging drug for humans won’t necessarily come from Loyal. There are basically two routes to market:

  1. A direct play (bring a new drug to market explicitly for ageing).

  2. Expand the indications for existing drugs, such as GLP-1s.

GLP-1s are already approved for diabetes and weight loss. Evidence also suggests they may help with heart disease, kidney disease, and Alzheimer's. In other words, GLP-1 drugs can expand healthspan. A true aging drug is no longer a question of ‘if,' but a matter of 'when.'

Thanks for writing this Niko and thank you for reading!

Keep on building the future,

— Jason