A Study of Mavacamten in Participants With HFpEF and Elevation of NT-proBNP With or Without Elevation of cTnT

Key Inclusion Criteria

• Is at least 50 years old at Screening.
• Body weight is greater than 45 kg at Screening.
• Documented prior objective evidence of heart failure as shown by 1 or more of the following criteria:
• Previous hospitalization for heart failure with documented radiographic evidence of pulmonary congestion.
• Elevated LV end-diastolic pressure or pulmonary capillary wedge pressure at rest (≥15 mm Hg) or with exercise (≥25 mm Hg).
• Elevated level of NT-proBNP (>400 pg/mL) or brain natriuretic peptide (BNP) (>200 pg/mL).
• Echocardiographic evidence of medial E/e' ratio ≥ 15 or left atrial enlargement (left atrial volume index >34 mL/m2) together with chronic treatment with spironolactone, eplerenone, or a loop diuretic.
• Meets 1 or more of the following criteria:
• A screening hs-cTnT ≥ 99th percentile AND a screening NT-proBNP > 200 pg/mL (if not in atrial fibrillation or atrial flutter) or > 500 pg/mL (if in atrial fibrillation or atrial flutter) OR if the screened participant is of African descent or has a body mass index (BMI) ≥ 30.0 kg/m2, a screening hs-cTnT ≥ 99th percentile, AND a screening NT-proBNP > 160 pg/mL (if not in atrial fibrillation or atrial flutter) or > 400 pg/mL (if in atrial fibrillation or atrial flutter).
• A screening NT-proBNP > 300 pg/mL (if not in atrial fibrillation or atrial flutter) or > 750 pg/mL (if in atrial fibrillation or atrial flutter) OR if the screened participant is of African descent or has a BMI ≥ 30.0 kg/m2, a screening NT-proBNP > 240 pg/mL (if not in atrial fibrillation or atrial flutter) or > 600 pg/mL (if in atrial fibrillation or atrial flutter).
• Has documented LVEF ≥60% at the Screening visit and no history of prior LVEF ≤ 45%.
• Has maximal left ventricular wall thickness ≥12 mm OR documented elevated left ventricular mass index by 2-dimensional imaging (>95 g/m2 if female and >115 g/m2 if male).
• Has high quality TTEs without or with echocardiographic contrast agents.
• Has NYHA class II or III symptoms at Screening.

Key Exclusion Criteria

• Has a prior diagnosis of HCM OR a known infiltrative or storage disorder causing HFpEF and/or cardiac hypertrophy, such as amyloidosis, Fabry disease, or Noonan syndrome with LV hypertrophy OR a positive serum immunofixation result.
• Has a history of syncope within the last 6 months or sustained ventricular tachycardia with exercise within the past 6 months.
• Has a history of resuscitated sudden cardiac arrest at any time or known appropriate implantable cardioverter defibrillator discharge within 6 months prior to Screening.
• Has persistent or permanent atrial fibrillation not on anticoagulation for at least 4 weeks prior to Screening and/or is not adequately rate controlled within 6 months prior to Screening.
• Currently treated or planned treatment during the study with either: (a) a combination of beta blocker and verapamil or a combination of beta blocker and diltiazem, (b) disopyramide, or (c) biotin or biotin-containing supplements/multivitamins.
• Has known moderate or severe aortic valve stenosis, hemodynamically significant mitral stenosis, or severe mitral or tricuspid regurgitation at Screening.
• Has severe chronic obstructive pulmonary disease, or other severe pulmonary disease, requiring home oxygen, chronic nebulizer therapy, chronic oral steroid therapy or hospitalized for pulmonary decompensation within 12 months.
• Has body mass index ≥45.0 kg/m2.
• Has left ventricular global longitudinal strain by TTE in the range from 0 to -12.0 (assessed by the central laboratory).
• Has NT-proBNP at Screening >2000 pg/mL.
• Has acute decompensated heart failure events requiring intravenous (IV) diuretics, IV inotropes, IV vasodilators, or a left ventricular assist device within 30 days prior to Screening.