First drug shown to reverse feline HCM expected to receive FDA conditional approval

Photo: nikkytok/Adobe Stock

A targeted formulation of the drug rapamycin, also known as sirolimus, has been shown to reverse hypertrophic cardiomyopathy (HCM) in cats, making it the first treatment to successfully treat HCM in felines. The drug’s major success in clinical trials has put it on track to receive expanded conditional approval from the FDA in March 2025, with a final pivotal study still in progress.

“Expanded conditional approval allows drugs that are undergoing their final clinical trial assessment and are supported by strong enough data and pilot studies to receive FDA permission to use the drug while the pivotal clinical trial is finishing,” Joshua Stern, DVM, PhD, DACVIM (Cardiology), associate dean for research and graduate studies at North Carolina State University (NC State) College of Veterinary Medicine, and lead of the research on the novel therapy, said in a news release.¹ “We’re enrolling cats in one of the largest feline clinical trials ever conducted now.”

The final study is being conducted at more than 20 sites throughout the United States, with researchers aiming to enroll 300 client-owned cats.¹ For the study, participants will be screened for a period of up to 14 days and will thereafter undergo a 12-month, once-weekly dosing period with 5 post-enrollment study visits.²

HCM is a serious and potentially fatal form of heart disease that causes the heart muscle to thicken, impairing the heart’s ability to pump blood. As the disease progresses, it can lead to fluid accumulation in the lungs; arterial thromboembolism, where blood clots obstruct flow to muscles and organs; congestive heart failure; and rhythm disturbances that can lead to sudden death.¹ Affecting approximately 15% of cats, the condition is the most common type of cardiac disease in felines.¹

Certain breeds, such as Maine Coons and Ragdolls, are genetically predisposed to developing the disease due to findings of mutations in the cardiac protein myosin binding protein C in affected Maine Coon and Ragdoll cats.³ The disease has been diagnosed in feline patients as young as 4 months and as old as 16 years old. Still, a definitive cause of feline HCM has not been found.³

Until now, there has been no therapeutic treatment for the disease—this may be changing as the novel therapy awaits conditional approval from the FDA and reaches the veterinary market thereafter. Stern predicts that the drug may become available to veterinarians for prescribing in June.¹

The research has been a collaboration between Stern and his team, and TriviumVet, an animal health company based in Ireland who funded the research and has patented the delayed-release formulation of rapamycin.¹ Both parties have worked to further the understanding of the molecular pathogenesis of HCM to develop the rapamycin drug specifically for cats.

According to NC State, Stern's lab discovered that rapamycin could slow or reverse the thickening of the heart muscle in felines with HCM before patients showed any symptoms of the disease.¹ The drug functions by inhibiting the mammalian target of rapamycin (mTOR) pathway, a central regulator of metabolism and physiology.¹

“This is a game-changer for us in terms of the reality of having something on the market that actually treats the underlying pathology of HCM, rather than just treating symptoms when they eventually develop,” Stern, the 2024 recipient of the Career Achievement in Feline Research Award from the American Veterinary Medical Foundation, said in the release.¹

For the final pivotal study, due to an overwhelming amount of owner queries, participation is restricted to those with direct referrals from veterinarians. Veterinarians interested in referring a feline patient with HCM for participation in the study can register their patient by visiting hcmincats.com.²

“Having a useful therapeutic will completely result in a paradigm shift for veterinarians,” concluded Stern.¹ “We’ve been playing defense against this disease for many, many years. We’re gonna go on the offensive now.”

References

1. Eplin Wheeler B. Studies led by NC State’s top researcher propelling first drug to treat feline heart condition to market. News release. North Caroline State University College of Veterinary Medicine. February 7, 2025. Accessed February 25, 2025. https://news.cvm.ncsu.edu/studies-led-by-nc-states-top-researcher-propelling-first-drug-to-treat-feline-heart-condition-to-market/
2. The HALT Study. TriviumVet. Accessed February 25, 2025. https://www.hcmincats.com/halt?__hstc=121558551.7990a16a3b08904537c796380c96c49e.1738598632651.1738616017841.1738617997523.4&__hssc=121558551.2.1738617997523&__hsfp=489374745
3. Hypertrophic cardiomyopathy (HCM). Cornell University College of Veterinary Medicine. Accessed February 25, 2025. https://www.vet.cornell.edu/hospitals/services/cardiology/hypertrophic-cardiomyopathy-hcm#:~:text=Hypertrophic%20cardiomyopathy%20(HCM)%20is%20the,old%20as%2016%20years%20old