Ready-to-use feline OA stem cell therapy gains entry to FDA’s faster conditional approval pathway

The FDA is opening a faster lane for living-cell therapies in pets, starting with cats.

Gallant, an animal health biotechnology company developing off-the-shelf stem cell therapies for pets, has received eligibility for the FDA Center for Veterinary Medicine’s expanded conditional approval pathway for its intravenous uterine-derived mesenchymal stromal cell therapy for feline osteoarthritis (OA). The designation offers a faster route to market for products addressing a significant unmet need, while data on target animal safety, manufacturing quality, and effectiveness continue to be collected.¹

The stem cell therapy could have potential disease-modifying effects for feline OA.

The news came alongside positive results from a pilot clinical study in which more than 76% of treated cats showed meaningful improvement in quality of life over 90 days.¹

OA affects an estimated 90% of cats older than 12 years, and researchers estimate that approximately 45% of all cats develop the condition. Yet OA is frequently underdiagnosed, in part because cats tend to mask pain through subtle behavioral changes, such as reduced activity, reluctance to jump, or shifts in grooming habits,² rather than obvious signs of distress. And the treatments that do exist largely just manage symptoms.

For Rebecca Windsor, DVM, DACVIM (Neurology), vice president of veterinary affairs at Gallant, that gap reflects a broader systemic issue in how feline medicine has historically been treated as an afterthought. "Felines have long been overlooked in medical research and therapeutic development, leaving a significant gap in care for a population that deserves far more attention," she said in an announcement by Gallant.¹

A study designed to measure what cat owners and clinicians actually see

Gallant’s pilot study was randomized, masked, and placebo-controlled, conducted across 6 veterinary clinics in the US. It enrolled 35 client-owned cats with radiographically confirmed OA in at least 2 joints and pain in at least 1 of those joints.² Cats received 2 intravenous injections 14 days apart—either a low dose of 5 million cells, a high dose of 20 million cells, or a saline placebo—and were evaluated over a 90-day period.^1,2

Outcomes were tracked using 4 distinct measures; 2 were reported by cat owners, and 2 were assessed by veterinarians. Owner-reported tools included the Client-Specific Outcome Measure (CSOM), a validated quality-of-life instrument through which caregivers identified 3 specific activities their cat could no longer perform normally and rated each on a 5-point scale, and an owner’s overall assessment using a categorical scale ranging from "greatly improved" to "worsened." Veterinary assessments included a pain evaluation based on joint palpation, graded on a 1-to-5 scale, and an overall treatment response score rated as excellent, good, fair, or poor.²

Ninety days into the study, 76.2% of cats treated with uterine-derived mesenchymal stromal cell therapy met the threshold for improvement on the CSOM compared with 36.4% of placebo recipients. On the owner’s overall assessment, 81% of treated cats were rated as improved vs 36.4% in the placebo group. Veterinary pain scores improved in 81% of treated cats compared with 45.5% of the placebo group, and 60% of treated cats received a positive overall treatment response rating from their veterinarian compared with 20% of placebo-treated cats.² Efficacy results were similar between the 5 million and 20 million cell doses.²

Gallant describes the therapy as generally well tolerated across both dose levels. A continuation study evaluating the safety and efficacy of the low-dose formulation out to 1 year is ongoing, and the 90-day results have been submitted for publication.¹

Targeting the root cause, not just the symptoms

Mesenchymal stromal cell therapy differs from existing OA treatments in its mechanism of action. Current treatments work by blocking inflammatory and pain signaling pathways, whereas mesenchymal stromal cells modulate the immune response. This approach may be well suited to feline OA, which research suggests has an immune-mediated component to its onset and progression.²

"The majority of inflammatory and many degenerative diseases are rooted in immune dysregulation," Windsor said in an earlier interview with dvm360. "Stem cells are predominantly immunomodulatory. We [administer intravenous therapy], and they start working immediately to reduce that systemic inflammation. Then they follow chemotactic signals from the diseased tissue. Once they're there, they release cytokines, growth factors, exosomes—all things that can help rebalance the immune system to make it less inflammatory."³

A different approach from other existing regenerative treatments

Gallant’s cells are sourced from uterine tissue collected from healthy donor animals that were going to be spayed regardless. The off-the-shelf model makes the therapy available on demand and avoids the need to harvest cells from the patient, which Windsor noted is a meaningful difference from much of what currently exists in the regenerative medicine space. It also offers a more standardized alternative to existing approaches.

"The majority of [other] therapies are going to be sourced from the patient [who is sick or older, which requires] putting the patient through a lot," Windsor told dvm360.³ "The other thing is [that] people are getting products that are not the same as a pure stem cell therapy [and] are not going through FDA regulations, so you're not quite sure exactly what you're getting."

Skeptics and safety questions

Stem cell therapy as a category carries some skepticism among some people, and Windsor acknowledged that two concerns surface most frequently.

"The No. 1 [concern] is whether or not it's going to cause an immune reaction," she said.³ Windsor explained that mesenchymal stromal cells carry a low number of major histocompatibility complex class receptors, which reduces the likelihood that the recipient's immune system will recognize the donor cells as foreign.

"The other common one is whether or not they're going to cause tumors. Mesenchymal stromal cells really stick inside their lane—they're not going to go form a bunch of other cells—and we've got good long-term data that show that they don't form tumors,” she said.

The profession is ready if the product is

Interest in regenerative medicine across the veterinary field has been growing. A survey conducted by the American Animal Hospital Association and Gallant, gathering input from 1095 small-animal professionals across the US, found that nearly 90% of respondents agreed that current therapies primarily manage symptoms rather than the root cause of disease.⁴ Ninety-five percent said they believed stem cell therapy would become part of the standard spectrum of care within the next decade, and 93% reported they would be more likely to offer clients regenerative therapy if it were available off the shelf through a simple intravenous protocol.⁴ Nearly half reported that clients had already begun asking about regenerative medicine options.⁴

"There's growing recognition that regenerative medicine can offer more than symptom management, and veterinary professionals want to feel confident discussing these new options," Windsor said.⁴

What comes next, and why cats are first

The feline OA treatment is Gallant's second stem cell therapy for cats. The company's lead product—sonruvetcel injectable suspension, targeting refractory feline chronic gingivostomatitis (rFCGS)—is currently under FDA review and is anticipated to receive conditional approval later this year.¹ If approved, the therapy would represent the first FDA-labeled, allogeneic, off-the-shelf stem cell therapy in veterinary medicine.⁵

In November 2025, the FDA Center for Veterinary Medicine issued a technical section complete letter for target animal safety for sonruvetcel, confirming that the company's data support the 365-day safety requirement.⁶ A study published in the Journal of Feline Medicine and Surgery, involving 46 cats with rFCGS, found that 75% of treated cats demonstrated a clinically relevant improvement in quality of life, and none experienced serious treatment-related adverse events.⁴

Gallant has indicated that it plans to focus on feline conditions first, with canine programs expected to follow. "We want cats to go first," Windsor told dvm360, noting that canine OA is closely behind in the pipeline, followed by atopic dermatitis and inflammatory bowel disease.³ Additional therapies for feline chronic kidney disease and canine atopic dermatitis are also in development,^1,5 supported in part by the $18 million that the company raised in a Series B funding round.⁵

References

1. Gallant reports positive pilot data for feline osteoarthritis stem cell therapy; receives FDA eligibility for expanded conditional approval pathway. News release. Gallant. April 15, 2026. Accessed April 15, 2026. https://tinyurl.com/ykd4bpv5
2. Windsor R. Mesenchymal stromal cell (MSC) therapy for feline osteoarthritis. Gallant. April 14, 2026. Accessed April 15, 2026. https://www.gallant.com/science-library/mesenchymal-stromal-cell-msc-therapy-for-feline-osteoarthritis/
3. Alaburda B, Windsor R. How off-the-shelf stem cells are aiming to treat systemic inflammation quickly. dvm360. November 14, 2025. Accessed April 15, 2026. https://www.dvm360.com/view/how-off-the-shelf-stem-cells-are-aiming-to-treat-systemic-inflammation-quickly
4. McCafferty C. Survey highlights veterinary consensus on stem cell efficacy for inflammatory conditions. dvm360. March 12, 2026. Accessed April 15, 2026. https://www.dvm360.com/view/survey-highlights-veterinary-consensus-on-stem-cell-efficacy-for-inflammatory-conditions
5. Bautista-Alejandre A. Veterinary stem cell therapy advances toward FDA approval with $18M in funding. dvm360. July 8, 2025. Accessed April 15, 2026. https://www.dvm360.com/view/veterinary-stem-cell-therapy-advances-toward-fda-approval-with-18m-in-funding
6. McCafferty C. Gallant achieves drug approval milestone. dvm360. November 12, 2025. Accessed April 15, 2026. https://www.dvm360.com/view/gallant-achieves-drug-approval-milestone