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.