Mavacamten in Chinese Patients with Obstructive Hypertrophic Cardiomyopathy: Patient-Reported Health Status Analysis up to 78 Weeks in the EXPLORER-CN Study

INTRODUCTION: Improvement of symptoms, physical function, and quality of life is one treatment goal for patients with obstructive hypertrophic cardiomyopathy (HCM). Mavacamten improved left-ventricular outflow tract gradients in Chinese patients with obstructive HCM in the EXPLORER-CN trial. We report here a detailed analysis of patient-reported health status per the 23-item Kansas City Cardiomyopathy Questionnaire (KCCQ-23) in Chinese patients after 78 weeks of mavacamten. METHODS: Patients who completed the double-blind, placebo-controlled (DBPC) period of EXPLORER-CN with no active safety concerns could enter a long-term extension (LTE) period to receive mavacamten for 48 weeks at either the 30-week dose (mavacamten-mavacamten group) or a once-daily starting dose of 2.5 mg (subsequently adjusted via pharmacodynamics-based dose titration: placebo-mavacamten group). Health status endpoints included KCCQ-23 clinical summary score (CSS), overall symptom score (OSS), total symptom score (TSS), physical limitations score, and quality-of-life scores through week 78. Week 78 endpoint analyses were descriptive. RESULTS: In the DBPC period, 54 patients received mavacamten and 27 received placebo; of these, 54 and 25, respectively, entered the LTE period. KCCQ-23 CSS, OSS, and TSS improved with mavacamten and worsened with placebo during the DBPC period (mean change baseline to week 30: 5.7, 6.4, and 8.1, respectively [mavacamten-mavacamten group] and - 5.4, - 4.3, and - 4.8, respectively [placebo-mavacamten group]). CSS, OSS, and TSS continued to improve in the mavacamten-mavacamten group during the LTE period (mean change baseline to week 78: 7.1, 8.2, and 10.0, respectively). Scores improved in the placebo-mavacamten group after switching to mavacamten (mean change week 30 to week 78: 7.3, 9.5, and 5.7, respectively). Similar improvements in KCCQ-23 physical limitations and quality-of-life scores with mavacamten were observed throughout both study periods. CONCLUSIONS: Long-term mavacamten treatment for up to 78 weeks led to sustained improvements in patient-reported health status, supporting long-term treatment with mavacamten for Chinese patients with symptomatic obstructive HCM. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT05174416.