Mavacamten is Being Developed to Treat the Most Common Inherited Form of Heart Disease, Hypertrophic Cardiomyopathy, for which No Targeted Medical Therapies Exist

Twelve-week Treatment with Mavacamten Demonstrated Reductions in Obstruction and Improvements in Patient Symptoms and Function

Learnings from Phase 2 Trial Informed and Guided Design of the Current Phase 3 
EXPLORER-HCM Pivotal Trial

SOUTH SAN FRANCISCO, Calif., April 30, 2019 – MyoKardia, Inc. (Nasdaq: MYOK), a clinical-stage biopharmaceutical company pioneering a precision medicine approach for the treatment of serious cardiovascular diseases, today announced the publication of results from the company’s Phase 2 PIONEER-HCM study of mavacamten in an upcoming issue of the Annals of Internal Medicine. A copy of the article, “Mavacamten Treatment for Obstructive Hypertrophic Cardiomyopathy” is now available online at the following link: http://annals.org/aim/article/doi/10.7326/M18-3016.