Inclusion Criteria:

• Males and females between 18 and 85 years of age, inclusive, at screening.
• Body mass index < 35 kg/m^2.
• 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 < 80% 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.

Exclusion Criteria:

• Known or suspected infiltrative, genetic or storage disorder causing cardiac hypertrophy that mimics oHCM (e.g., 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 (e.g., 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 requiring rhythm restoring treatment (e.g., direct-current cardioversion, atrial fibrillation ablation procedure, or antiarrhythmic therapy) ≤ 6 months prior to screening. (This exclusion does not apply if atrial fibrillation has been treated with anticoagulation and adequately rate-controlled for > 6 months).
• History of syncope or sustained ventricular tachyarrhythmia with exercise within 6 months prior to screening.
• Has received prior treatment with CK-3773274 or mavacamten.

Eligibility last updated 2/24/22. Questions regarding updates should be directed to the study team contact.