MyoKardia Announces Positive Results from Low-Dose Cohort of Phase 2 PIONEER-HCM Study of Mavacamten in Symptomatic, Obstructive Hypertrophic Cardiomyopathy Patients Met Primary Endpoint and Key Secondary Endpoints with Statistical Significance Study Results Inform Phase 3 EXPLORER-HCM Dosing; First Patient Planned for Q2 2018 Conference Call Today...