Effect of Mavacamten on Chinese Patients With Symptomatic Obstructive Hypertrophic Cardiomyopathy

Abstract

IMPORTANCE Mavacamten has shown clinical benefits in global studies for patients with obstructive hypertrophic cardiomyopathy (oHCM), but evidence in the Asian population is lacking. OBJECTIVE To evaluate the safety and efficacy of mavacamten compared with placebo for Chinese patients with symptomatic oHCM. DESIGN, SETTING, AND PARTICIPANTS This phase 3, randomized, double-blind, placebo-controlled clinical trial was conducted at 12 hospitals in China. Between January 4 and August 5, 2022, patients with oHCM and a left ventricular outflow tract (LVOT) gradient of 50 mm Hg or more and New York Heart Association (NYHA) class II or III symptoms were enrolled and received treatment for 30 weeks. INTERVENTIONS Patients were randomized 2:1 to receive mavacamten (starting at 2.5 mg once daily) or placebo for 30 weeks. MAIN OUTCOMES AND MEASURES The primary end point was change in Valsalva LVOT peak gradient from baseline to week 30. Left ventricular outflow tract gradients and left ventricular ejection fraction (LVEF) were assessed by echocardiography, while left ventricular mass index (LVMI) was determined by cardiac magnetic resonance imaging. Analysis was performed on an intention-to-treat basis. RESULTS A total of 81 patients (mean [SD] age, 51.9 [11.9] years; 58 men [71.6%]) were randomized. Mavacamten demonstrated a significant improvement in the primary end point compared with placebo (least-squares mean [LSM] difference, -70.3 mm Hg; 95% CI, -89.6 to -50.9 mm Hg; 1-sided P