A Study of Mavacamten in Obstructive Hypertrophic Cardiomyopathy

Inclusion Criteria: * Age 18 and greater, body weight ≥ 35kg * Has adequate acoustic windows to enable accurate transthoracic echocardiograms (TTEs) * Diagnosed with obstructive hypertrophic cardiomyopathy consistent with current American College of Cardiology Foundation/American Heart Association, European Society of Cardiology, and Japanese Circulation Society guidelines * Has documented left ventricular ejection fraction (LVEF) ≥60% NYHA Class II or III Exclusion Criteria: * Known infiltrative or storage disorder causing cardiac hypertrophy that mimics oHCM, such as Fabry disease, amyloidosis, or Noonan syndrome with LV hypertrophy * History of syncope or sustained ventricular tachyarrhythmia with exercise within 6 months prior to Screening * History of resuscitated sudden cardiac arrest (at any time) or known history of appropriate implantable cardioverter defibrillator (ICD) discharge for life-threatening ventricular arrhythmia within 6 months prior to Screening * Paroxysmal atrial fibrillation with atrial fibrillation present at the time of Screening. * Persistent or permanent atrial fibrillation not on anticoagulation for at least 4 weeks prior to Screening and/or not adequately rate controlled within 6 months prior to Screening * Treatment (within 14 days prior to Screening) or planned treatment during the study with cibenzoline, disopyramide or ranolazine * Treatment (within 14 days prior to Screening) or planned treatment during the study with a combination of beta blockers and verapamil or a combination of beta blockers and diltiazem * Has been successfully treated with invasive septal reduction (surgical myectomy or percutaneous alcohol septal ablation \[ASA\]) within 6 months prior to Screening or plans to have either of these treatments during the study * ICD placement within 2 months prior to Screening or planned ICD placement during the study * Has a history or evidence of any other clinically significant disorder, condition, or disease that, in the opinion of the investigator, would pose a risk to participant safety or interfere with the study evaluation procedures, or completion * Prior treatment with cardiotoxic agents such as doxorubicin or similar Other protocol-defined inclusion/exclusion criteria apply