A Study of Mavacamten in Obstructive Hypertrophic Cardiomyopathy

Inclusion Criteria:

1. Age 18 and greater, body weight ≥ 35kg
2. Has adequate acoustic windows to enable accurate transthoracic echocardiograms (TTEs)
3. 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
4. Has documented left ventricular ejection fraction (LVEF) ≥60% NYHA Class II or III

Exclusion Criteria:

1. Known infiltrative or storage disorder causing cardiac hypertrophy that mimics oHCM, such as Fabry disease, amyloidosis, or Noonan syndrome with LV hypertrophy
2. History of syncope or sustained ventricular tachyarrhythmia with exercise within 6 months prior to Screening
3. 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
4. Paroxysmal atrial fibrillation with atrial fibrillation present at the time of Screening.
5. 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
6. Treatment (within 14 days prior to Screening) or planned treatment during the study with cibenzoline, disopyramide or ranolazine
7. 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
8. 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
9. ICD placement within 2 months prior to Screening or planned ICD placement during the study
10. 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
11. Prior treatment with cardiotoxic agents such as doxorubicin or similar

Other protocol-defined inclusion/exclusion criteria apply