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.

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

What this study is about