RecruitingDrug trialA Study to Evaluate the Effect of Aficamten in Pediatric Patients With Symptomatic Obstructive Hypertrophic Cardiomyopathy (oHCM).The purpose of this study is to evaluate the efficacy, safety and PK of aficamten in a pediatric population with symptomatic obstructive hypertrophic cardiomyopathy (oHCM).