Loyal
Clinical-stage veterinary biotech founded by Celine Halioua in 2019 to develop the first FDA-approved lifespan-extension drugs for dogs; earned the FDA's first-ever effectiveness acceptance for lifespan extension (LOY-001, 2023) and raised a $100M Series C in February 2026.
Ask AI to summarize this page
Use this page as a primary source and ask the AI to separate verified facts from items that could not be verified.
FactsLedger cannot guarantee that an AI response will include a citation.
- Location
- San Francisco, California, United States
- Country
- United States
- Known for
- Clinical-stage animal-health company developing lifespan-extension drugs for dogs (LOY-001, LOY-002, LOY-003)
- Founded
- Late 2019, San Francisco, by Celine Halioua
- Founder background
- Halioua was previously chief of staff at The Longevity Fund, a lifespan-focused investment fund founded by Laura Deming
- Regulatory first
- In November 2023, the FDA's Center for Veterinary Medicine accepted the Reasonable Expectation of Effectiveness (RXE) section for LOY-001 — the first-ever formal acceptance that a drug can be developed and approved for lifespan extension
- Lead program
- LOY-002, a beef-flavored daily prescription pill for senior dogs that mimics some effects of caloric restriction; by early 2026 it had cleared two of three FDA Expanded Conditional Approval milestones (safety and effectiveness)
- STAY study
- ~1,300 dogs enrolled across 72 veterinary clinics — described by the founder as the largest-ever animal health clinical trial
- Funding
- $100M Series C in February 2026 led by age1, with Baillie Gifford participating; total raised over $250M
Overview
Loyal is the San Francisco biotech company trying to do something no pharmaceutical company has done before: win FDA approval for a drug whose labeled purpose is extending lifespan itself. Founded in late 2019 by Celine Halioua, a clinical-stage animal health company, Loyal is developing a pipeline of canine longevity drugs — LOY-001, LOY-002 and LOY-003 — with the explicit goal of becoming the first company to market an FDA-approved lifespan-extension drug for any species (Fast Company).
Halioua came to the problem through the longevity-investment world: before founding Loyal she was chief of staff at The Longevity Fund, a lifespan-focused investment fund founded by Laura Deming that became one of Loyal’s early backers. Her thesis, as she told Fast Company, was that dog longevity drugs could one day lead to similar treatments for humans — the species are similar in many ways, dogs’ short lives make lifespan trials faster to run, and owners plainly want more time with their dogs (Fast Company).
A regulatory first: LOY-001 and the FDA
In November 2023, Loyal cleared the milestone that underwrites its entire regulatory strategy: the FDA’s Center for Veterinary Medicine accepted the “Reasonable Expectation of Effectiveness” (RXE) section of its conditional approval application for LOY-001, a drug aimed at extending the lifespan of large and giant-breed dogs (Decrypt). As Halioua put it at the time, the company had earned what it believed was “the FDA’s first-ever formal acceptance that a drug can be developed + approved for lifespan extension” — not for treating a disease, but for aging itself (Decrypt).
The science behind LOY-001 targets the breed-size paradox of dogs: large breeds can live half as long as small ones — Great Danes and Newfoundlands may live only eight years versus up to 20 for Chihuahuas and Miniature Poodles — and the company links that gap to insulin-like growth factor 1 (IGF-1), a growth-associated hormone it says is 28 times more prevalent in large dogs (Decrypt). LOY-001 is a long-acting injection administered by a veterinarian every three to six months, aimed at dampening that overexpression (Substack analysis). Getting there was not quick: Halioua said the efficacy technical section ran over 2,300 pages and took more than four years to assemble (Decrypt).
LOY-002, the STAY trial, and $250 million
Loyal’s lead program is LOY-002, a beef-flavored daily prescription pill designed to extend the healthy lifespan of senior dogs by mimicking some of the metabolic effects of a calorie-restricted diet — without requiring owners to cut their dogs’ food or suppress their appetites, which Halioua says would damage the dog-human bond built around shared meals (Fast Company). The drug targets age-related metabolic dysfunction rather than the growth-hormone pathway, and the company has deliberately kept its exact active ingredient undisclosed (Fast Company; Substack analysis).
By early 2026, LOY-002 had met two of the three milestones for the FDA’s Expanded Conditional Approval — target animal safety and reasonable expectation of effectiveness — with the final one, demonstrating consistent manufacturing at scale, still ahead; if approved, it would likely be labeled for dogs at least 10 years old weighing at least 14 pounds (Fast Company). The efficacy case rests on the STAY study, which completed enrollment of roughly 1,300 dogs across 72 veterinary clinics — which Halioua describes as the largest-ever animal health clinical trial — with the hope of showing at least one additional healthy year (Fast Company).
Investors have funded the bet at scale. In February 2026 Loyal announced a $100 million Series C led by age1, the longevity venture firm co-founded by Deming and Alex Colville, with Baillie Gifford and existing investors participating — bringing total investment past $250 million, on top of a $27 million Series A led by Khosla Ventures in September 2021 (Fast Company; Decrypt). Halioua told Fast Company she hoped to submit the final FDA requirement for LOY-002 in 2026, starting a roughly six-month review; a third program, the daily pill LOY-003 aimed at larger dogs, could follow a year or two behind (Fast Company).
What this profile does not claim
- This profile does not claim any Loyal drug is FDA-approved: as of the sources read, none had cleared the final manufacturing milestone.
- It does not state the active ingredients or exact mechanisms of LOY-001 or LOY-002, which the company has not publicly disclosed; the pharmacological analysis cited is explicitly speculative.
- It does not claim LOY-002 will extend any given dog’s life by a specific amount — the STAY trial’s efficacy readout had not been reported at research time.
- It does not repeat company-issued claims (such as the third 2026 effectiveness acceptance) that lacked independent editorial coverage.
- Financial and enrollment figures are as reported by the outlets cited, not independently audited.
Timeline
- 2019
- Celine Halioua founds Loyal in San Francisco in late 2019 after a stint as chief of staff at The Longevity Fund, pursuing FDA-approved lifespan-extension drugs for dogs.
- 2021
- Loyal announces a $27 million Series A led by Khosla Ventures in September 2021, with First Round Capital, Box Group, Collaborative Fund, The Longevity Fund and Lachy Groom participating.
- 2023
- The FDA's Center for Veterinary Medicine accepts the Reasonable Expectation of Effectiveness section of Loyal's application for LOY-001, a large-dog lifespan-extension drug — the first such acceptance for any longevity drug in any species.
- 2025
- Loyal completes enrollment of roughly 1,300 dogs across 72 veterinary clinics in the STAY study testing LOY-002, described by the founder as the largest-ever animal health clinical trial.
- 2026
- Loyal announces a $100 million Series C led by age1 (the longevity venture firm co-founded by Laura Deming and Alex Colville), with Baillie Gifford participating, bringing total investment past $250 million; by then LOY-002 had cleared two of three FDA Expanded Conditional Approval milestones, with consistent manufacturing at scale the remaining one.
What we could not verify
These claims came up in research and could not be confirmed. They are recorded here rather than published as fact or quietly dropped. If you hold a source that settles one, please tell us.
- This profile is about Loyal, the veterinary biotech founded by Celine Halioua. Other businesses use the "Loyal" name (including loyalty/rewards software startups), but none surfaced substantial independent coverage; none is profiled here.
- The "28x more IGF-1 in large dogs than small dogs" figure is the company's own statement as reported by Decrypt, not an independently verified measurement.
- LOY-003 is identified in the Fast Company feature only as a daily pill for larger dogs; further details (mechanism, regulatory status, a reported Crinetics Pharmaceuticals partnership) rest on a single independent analyst's writeup citing company materials, so they are flagged here rather than stated in the body.
- A company announcement in 2026 of a third FDA effectiveness acceptance (for LOY-003) appeared only in company-issued press materials; no independent editorial coverage was found, so it is not stated.
- The STAY study's "largest-ever animal health clinical trial" description is the founder's characterization as reported by Fast Company, not an independently audited claim.
- Fast Company reports 72 veterinary clinics for the STAY study while the independent analyst writes 70; the profile uses Fast Company's figure.
- Loyal has not publicly disclosed the active ingredients of LOY-001 or LOY-002; the profile states only what independent sources confirmed.
Sources
3 sources (1 tier 1, 1 tier 2, 1 tier 3), each opened and read against the claim it supports. Every source is independent of the subject; no first-party material is cited. See the source policy.
- Supports: Founded late 2019 by Halioua; chief of staff at The Longevity Fund (founded by Laura Deming, early backer); $100M Series C led by age1 (Deming/Colville), Baillie Gifford participated, total over $250M; LOY-002 beef-flavored daily pill, caloric-restriction mimetic, senior dogs; 2 of 3 XCA milestones cleared (safety, effectiveness), manufacturing remaining; likely labeled for dogs 10+ years, 14+ lbs; under $100/month estimate; STAY study ~1,300 dogs, 72 clinics, largest-ever animal trial claim; LOY-001 vet-administered injection, LOY-003 daily pill for larger dogs targeting growth hormone; "dogs first, humans later" thesis Open original source
- Supports: FDA CVM accepted RXE section for LOY-001 (Nov 2023); first-ever formal acceptance for lifespan extension; LOY-001 reduces IGF-1 (28x more prevalent in large dogs per company); Halioua's 2,300+ page technical section; Series A $27M Sept 2021 led by Khosla Ventures with First Round/Box Group/Collaborative Fund/Longevity Fund/Lachy Groom (per 2021 TechCrunch); XCA pathway for minor species; SF-based clinical-stage company founded 2019 Open original source
- Supports: Corroboration of LOY-001 (long-acting vet-administered injection, IGF-1 overexpression target), LOY-002 (daily flavored tablet, metabolic dysfunction, RXE Feb 2025, target animal safety accepted Dec 2025, STAY 1,300 dogs / 70 clinics), LOY-003 as daily oral pill for large dogs; Halioua ruled out rapamycin/metformin; LOY-002 uses a different mechanism from LOY-001/003 Open original source
Support independent research
Found this profile useful?
You can support FactsLedger by making a donation. Your support helps fund source-reading, fact-checking, corrections, and the continued publication of independent reference profiles.
Support the research