Open-label Extension Study to Evaluate the Long-term Safety and Tolerability of Aficamten in Adults With HCM

The purpose of this study is to collect long-term safety and tolerability data for aficamten.

Inclusion Criteria: * Completion of a Cytokinetics trial investigating aficamten * LVEF ≥ 55% at the Screening Visit Exclusion Criteria: * Has received treatment with mavacamten: (a) within 56 days prior to dosing and (b) has not received approval for participation from the Medical Monitor. * Has participated in another investigational device or drug study or received an investigational device or drug \< 1 month (or 5 half-lives for drugs, whichever is longer) prior to screening. Other investigational procedures while participating in this study are not permitted. * Since completion of a previous trial of aficamten has: * Developed new-onset paroxysmal or permanent atrial fibrillation requiring rhythm restoring treatment (eg, direct-current cardioversion, ablation procedure, or antiarrhythmic therapy) \< 30 days prior to screening. Patient may re-screen for CY 6022 after 30 days if heart rate (HR) \< 100 bpm and/or rhythm is stable \> 30 days * Undergone septal reduction therapy (surgical myectomy or transcatheter alcohol ablation) * Had a confirmed LVEF \< 40% with an associated dose interruption during participation in a prior study with aficamten * History of implantable ICD placement within 30 days prior to screening.