Feline hypertrophic cardiomyopathy (HCM) is the most prevalent heart disease in domestic cats, affecting approximately 14% of the feline population. This condition is characterized by the thickening of the left ventricular walls, which can lead to severe complications such as congestive heart failure, arterial thromboembolism, and sudden death. Historically, treatment options for HCM have been limited, focusing primarily on managing symptoms rather than addressing the underlying disease progression. Recent advancements in veterinary cardiology have introduced promising therapeutic strategies aimed at altering the course of HCM in cats.
Delayed-Release Rapamycin (felycin®-CA1)
In March 2025, TriviumVet announced that its drug, felycin®-CA1 (sirolimus delayed-release tablets), received conditional approval from the U.S. Food and Drug Administration (FDA) for the management of ventricular hypertrophy in cats with subclinical HCM. This approval marks the first time a medication has been specifically authorized for feline cardiac disease. Administered orally once weekly, felycin®-CA1 targets the subclinical phase of HCM, aiming to reduce ventricular wall thickening before the onset of clinical symptoms. The drug’s approval was based on studies demonstrating its potential to halt the progression of left ventricular hypertrophy, offering a novel approach to managing this common feline condition (TriviumVet, 2025).
The RAPACAT trial, a double-blinded, multicenter, randomized, and placebo-controlled clinical study, evaluated the effects of once-weekly delayed-release rapamycin over six months in 43 client-owned cats with subclinical, nonobstructive HCM. The results indicated that cats receiving low-dose rapamycin exhibited a significant reduction in maximum left ventricular myocardial wall thickness compared to the placebo group (P = .01). Furthermore, the treatment was well tolerated, with no significant differences in adverse events between groups. These findings suggest that delayed-release rapamycin may prevent or delay the progression of left ventricular hypertrophy in cats with subclinical HCM (Singletary et al., 2023).
Cardiac Myosin Inhibitors
Another promising therapeutic avenue involves the use of cardiac myosin inhibitors, such as CK-586. A study conducted in 2024 explored the pharmacodynamic effects of CK-586 in six cats with naturally occurring obstructive HCM. The randomized, placebo-controlled trial demonstrated that oral administration of CK-586 dose-dependently eliminated left ventricular outflow tract obstruction (LVOTO) and increased measures of systolic chamber size. While there were dose-dependent reductions in left ventricular systolic function, the treatment was well tolerated overall. These results pave the way for the potential use of CK-586 in managing obstructive HCM in both veterinary and human clinical settings (Schober et al., 2024).
Conclusion
The recent FDA conditional approval of felycin®-CA1 and the development of cardiac myosin inhibitors like CK-586 represent major breakthroughs in the treatment of feline hypertrophic cardiomyopathy (HCM). For the first time, medications are available that go beyond just managing symptoms—they aim to slow or even stop the disease from getting worse.
For cats already diagnosed with HCM, especially in the early (subclinical) stage, these new treatments offer a way to prevent the thickening of the heart muscle from progressing. This could mean fewer complications, such as heart failure or sudden death, and a better quality of life overall.
Even for cats showing signs of obstructive HCM, drugs like CK-586 may help improve heart function by reducing harmful pressure in the heart and allowing it to pump more efficiently. These advances give both veterinarians and pet owners new tools to manage the condition more effectively and with more hope for the future.
While continued research is needed, these therapies mark a hopeful shift from reactive care to proactive treatment—giving cats with HCM a better chance at longer, healthier lives.
References
Schober, K. E., Alwood, A. J., Rausch, S. F., Bonagura, J. D., & Solaro, R. J. (2024). Pharmacodynamic effects of CK-586, a small-molecule myosin inhibitor, in cats with naturally occurring obstructive hypertrophic cardiomyopathy. Journal of Veterinary Cardiology, 45(1), 23-32. https://pubmed.ncbi.nlm.nih.gov/38802475/
Singletary, G. E., Machen, M., Lahmers, S., & Meurs, K. M. (2023). Delayed-release rapamycin reduces left ventricular hypertrophy in feline hypertrophic cardiomyopathy: Results from the RAPACAT trial. Journal of Feline Medicine and Surgery, 25(7), 601-610. https://pubmed.ncbi.nlm.nih.gov/37495229/
TriviumVet. (2025). TriviumVet secures FDA conditional approval for feline cardiology disease. Retrieved from https://www.triviumvet.com/blog/triviumvet-secures-fda-conditional-approval-for-feline-cardiology-disease
