CY 6031 Study Will Evaluate the Effects of Treatment With Aficamten (CK-3773274) Over a 24-week Period on Cardiopulmonary Exercise Capacity and Health Status in Patients With Symptomatic oHCM

Open to people ages 18-85

• Males and females between 18 and 85 years of age, inclusive, at screening.
• Body mass index <35 kg/m2.
• Diagnosed with HCM per the following criteria:
  • Has LV hypertrophy and non-dilated LV chamber in the absence of other cardiac disease and
  • Has an end-diastolic LV wall thickness as measured by the echocardiography core laboratory of:
    • ≥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
• Has resting LVOT-G ≥30 mmHg and post-Valsalva LVOT G ≥50 mmHg during screening as determined by the echocardiography core laboratory.
• LVEF ≥60% at screening as determined by the echocardiography core laboratory.
• NYHA Functional Class II or III at screening.
• Hemoglobin ≥10g/dL at screening.
• Respiratory exchange ratio (RER) ≥1.05 and pVO2 ≤90% predicted on the screening CPET per the core laboratory.
• Patients on beta-blockers, verapamil, diltiazem, or disopyramide should have been on stable doses for >6 weeks prior to randomization and anticipate remaining on the same medication regimen during the trial. Patients treated with disopyramide must also be concomitantly treated with a beta blocker and/or calcium channel blocker.

• Known or suspected infiltrative, genetic or storage disorder causing cardiac hypertrophy that mimics oHCM (eg, Noonan syndrome, Fabry disease, amyloidosis).
• Significant valvular heart disease (per investigator judgment).
  • Moderate-severe valvular aortic stenosis.
  • Moderate-severe mitral regurgitation not due to systolic anterior motion of the mitral valve.
• History of LV systolic dysfunction (LVEF <45%) or stress cardiomyopathy at any time during their clinical course.
• Inability to exercise on a treadmill or bicycle (eg, orthopedic limitations).
• Has been treated with septal reduction therapy (surgical myectomy or percutaneous alcohol septal ablation) or has plans for either treatment during the trial period.
• Documented paroxysmal atrial fibrillation during the screening period.
• Paroxysmal or permanent atrial fibrillation is only excluded IF:
  • rhythm restoring treatment (eg, direct-current cardioversion, atrial fibrillation ablation procedure, or antiarrhythmic therapy) has been required ≤6 months prior to screening.
  • rate control and anticoagulation have not been achieved for at least 6 months prior to screening.
• History of syncope or sustained ventricular tachyarrhythmia with exercise within 6 months prior to screening.
• Has received prior treatment with CK-3773274 or mavacamten.