A Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic Non-Obstructive Hypertrophic Cardiomyopathy (nHCM)

Inclusion Criteria: * Between 18-85 years of age * Body mass index \< 40 kg/m2 * Diagnosed with nHCM and has a screening echocardiogram with the following: * End-diastolic left ventricular (LV) wall thickness: * ≥ 15 mm in one or more myocardial segments OR * ≥ 13 mm in one or more wall segments and a known disease-causing gene mutation or positive family history of HCM AND * Resting LVOT-G \< 30 mmHg AND Valsalva LVOT-G \< 50 mmHg AND * LVEF ≥ 60% * Participants with a history of intracavitary obstruction are eligible. * NYHA class II or III * Respiratory exchange ratio of ≥ 1.00 at screening by cardiopulmonary exercise testing (CPET) and predicted peak oxygen uptake (pVO2) ≤ 90% for age and sex * KCCQ-CSS score of ≤ 85 * NT-proBNP of: * NT-pro BNP ≥ 300 pg/mL or NT-proBNP ≥ 900 pg/mL if in atrial fibrillation or atrial flutter OR * For Black participants, an NT-pro BNP ≥ 225 pg/mL or NT-proBNP ≥ 675 pg/mL if in atrial fibrillation or atrial flutter Exclusion Criteria: * Significant valvular heart disease (per Investigator judgment) * Moderate or severe valvular aortic stenosis or fixed subaortic obstruction * Moderate or severe mitral regurgitation * Known or suspected infiltrative, genetic or storage disorder causing cardiac hypertrophy that mimics nHCM (eg, Noonan syndrome, Fabry disease, amyloidosis) * Known current unrevascularized coronary artery stenosis of ≥ 70% or documented history of myocardial infarction. * History of LV systoli…