Abstract 14254: Pharmacodynamic Effects of a Single Dose of CK-3773274 in Cats With Hypertrophic Cardiomyopathy

Introduction: Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular (LV) hypertrophy in the absence of known causes. HCM can be due to genetic mutations that affect sarcomeric proteins, leading to myocardial hypercontractility. HCM is often complicated by left ventricular outflow tract obstruction (LVOTO) and patients may be at greater risk of cardiovascular death. Medications targeted to address the pathophysiology of HCM and ameliorate LVOTO are needed. CK-3773274 (CK-274) is a novel small molecule cardiac myosin inhibitor that reduces myocardial contractility in vitro and in vivo . Cats have naturally occurring HCM commonly complicated by LVOTO and are an excellent large animal model for investigation of HCM therapeutics. In this study, we aim to characterize the pharmacodynamic effect of a single oral dose of CK-274 on cardiac function in cats with hypertrophic cardiomyopathy and LVOTO. Methods: Eight purpose-bred cats with naturally occurring HCM and LVOTO due to the A31P mutation in cardiac myosin binding protein C (cMyBP-C) were included in a randomized, controlled, crossover study. Cats were randomized to receive vehicle, 0.3 mg/kg, or 1 mg/kg CK-274 treatment, and received echocardiograms at baseline, 6, 24, and 48 hours post-treatment. All cats were crossed over to all treatment groups. Results: CK-274 (1 mg/kg) reduced mean LV fractional shortening at 6, 24 and 48 hours post-treatment (mean reduction 13.6%, p=0.03; 15.4%, p=0.01; 11.6% p=0.02, respectively). CK-274 (1 mg/kg) increased LV systolic internal dimension at 6 and 24-hours post-treatment (mean increase 0.21 cm, p=0.046; 0.25 cm, p=0.03), and did not affect LV diastolic internal dimension. LVOT peak pressure gradient was reduced with CK-274 (0.3 mg/kg) treatment [median pressure gradient at baseline 27.1 mmHg (IQR 18.3-33.3) vs 24 hours post-drug, 7.3 mmHg (IQR 14.2-19.7) p=0.01]. Heart rate did not change for any treatment group over time. No differences were noted following vehicle administration at any time point. Conclusion: In HCM affected cats with the cMyBP-C A31P mutation, the cardiac myosin inhibitor CK-274 is well tolerated at the studied doses and caused dose-related changes in LV systolic function and reductions in LVOT peak pressure gradient.