Key Inclusion Criteria:  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 <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.  Key Exclusion Criteria:  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 requiring rhythm restoring treatment (eg, 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.