Mass General - Division of Clinical Research

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 (CK-3773274)

Completion of a Cytokinetics trial investigating CK-3773274 - LVEF ≥55% at the Screening Visit

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 CK-3773274 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) since the completion of a prior trial of CK-3773274. - Had a confirmed LVEF <40% with an associated dose interruption during participation in a prior study with CK-3773274 - History of appropriate ICD shock within 30 days prior to screening

Arm	Description	Assigned Intervention
Experimental CK-3773274 up to 20 mg	Patients in this arm take daily dose of CK-3773274. Each patient will start at the lowest prespecified dose and titrate up to their maximum tolerated dose.	Drug: CK-3773274 (5 - 20 mg) CK-3773274 tablets administered orally