Clinical Study to Evaluate Mavacamten (MYK-461) in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy

A Randomized, Double Blind, Placebo Controlled Clinical Study to Evaluate Mavacamten (MYK-461) in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy

This is a multicenter, international, double-blind study of the administration of mavacamten in participants with symptomatic obstructive HCM (oHCM). Approximately 220 participants will be randomized to receive placebo or mavacamten.

Key Inclusion Criteria:

• Age 18 and greater, body weight ≥ 45kg
• Has adequate acoustic windows to enable accurate transthoracic echocardiograms (TTEs)
• Diagnosed with oHCM consistent with current American College of Cardiology Foundation/American Heart Association and European Society of Cardiology guidelines and satisfy both criteria:
• Has documented left ventricular ejection fraction (LVEF) ≥55%
• NYHA Class II or III
• Has documented oxygen saturation at rest ≥90% at Screening
• Is able to perform an upright CPET and has a respiratory exchange ratio (RER) ≥1.0 at Screening per central reading

Key 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, intermittent atrial fibrillation with atrial fibrillation present at 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 disopyramide or ranolazine
• Treatment (within 14 days prior to Screening) or planned treatment during the study with a combination of β-blockers and calcium channel blockers
• LVOT gradient with Valsalva maneuver <30 mmHg at Screening
• 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