A Study of Mavacamten in Non-Obstructive Hypertrophic Cardiomyopathy

The KCCQ-23 is a 23-item, self-administered questionnaire that measures the impact of a participant's cardiovascular disease or its treatment on 6 distinct domains using a 2-week recall period: symptoms/signs, physical limitation, quality of life (QoL), social limitations, self-efficacy, and symptom stability. The KCCQ 23 Clinical Summary Score (CSS) is derived from the Total Symptom Score (TSS) and the Physical Limitations (PL) score of the KCCQ 23. The CSS, TSS, and the PL score range from 0 to 100 with higher scores representing less severe symptoms and/or physical limitations. The CSS is a mean of the TSS and the PL score. Baseline is defined as the last non-missing assessment prior to the first dose of the study treatment if both the time of the measurement and the time of first dose are available otherwise it is the last non-missing assessment on or prior to the first dose of the study treatment.

Clinically meaningful mean change from baseline(1.4ml/kg/min) of pVO2 at Week 48.

VE/VCO₂ slope was assessed using cardiopulmonary exercise testing (CPET). The slope was calculated as the linear regression of minute ventilation (VE) against carbon dioxide production (VCO₂). A decrease in VE/VCO₂ slope reflects improved ventilatory efficiency.

Blood samples were collected for assessing the concentration of NT-proBNP. Baseline is defined as last non-missing measurement prior to the first dose.

Participants with \>= 1 NYHA function class improvement.

The NYHA Functional Classification of heart failure assigns participants to 1 of 4 categories based on the participant's symptoms.

Class 1: No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea (shortness of breath).

Class 2: Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea (shortness of breath).

Class 3: Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitation, or dyspnea.

Class 4: Unable to carry on any physical activity without discomfort. Symptoms of heart failure at rest. If any physical activity is undertaken, discomfort increases.

The HCMSQ is a self- administered, 9-item questionnaire that assesses the core symptoms of HCM (shortness of breath, tiredness/fatigue, heart palpitations, chest pain, dizziness, and syncope). At each visit, a 7-day period will be defined, ending on the last day with a non-missing HCMSQ score prior to the actual clinic visit (or first dose date if baseline). If the participant completes the HCMSQ for 4 or more days within this period, the weekly average HCMSQ score will be calculated. If fewer than 4 days are completed, other 7-day periods will be considered. For baseline, any 7-day period with at least 4 days of HCMSQ prior to the first dose or randomization date (if first dose date is missing) will be used.

Each domain of the SoB scale is scored 1 to 6. The scores are added together to give a total score. Lower scores indicating low to no shortness of breath, higher scores indicating frequent episodes of shortness of breath.

the lower the score the better.