MyoKardia Presents Additional Positive Data from Phase 2 PIONEER-HCM Study of Mavacamten (Formerly MYK-461) at the Heart Failure Society of America’s 21st Annual Scientific Meeting

09/18/2017

SOUTH SAN FRANCISCO, California (GLOBE NEWSWIRE)—MyoKardia, Inc. (Nasdaq:MYOK) (“MyoKardia” or the “Company”), a clinical stage biopharmaceutical company pioneering a precision medicine approach for the treatment of heritable cardiovascular diseases, today announced that additional positive data from the first patient cohort of its Phase 2 PIONEER-HCM study of mavacamten in symptomatic, obstructive hypertrophic cardiomyopathy (oHCM) patients were presented at the Heart Failure Society of America (HFSA)’s 21st Annual Scientific Meeting in Dallas, TX.

In an oral presentation as part of the “Big Trials of the Last Year” session at HFSA, Stephen Heitner, M.D., director of the HCM Clinic at Oregon Health and Science University’s Knight Cardiovascular Institute, and the lead investigator in the PIONEER-HCM study, presented new time-series plots of individual patient data on the primary endpoint, post-exercise peak left ventricular outflow tract (LVOT) gradient, and time-series plots of mean data on several additional measures, including resting LVOT gradient and resting left ventricular ejection fraction (LVEF) from baseline to week 12. Additional measures of exercise capacity, functional capacity and symptoms were also presented, as well as data on the safety profile of mavacamten.

MyoKardia initially reported positive topline results from this first patient cohort on August 7, 2017, which met the primary endpoint of change in post-exercise peak LVOT gradient from baseline to week 12 as well as key secondary endpoints, including peak oxygen consumption (peak VO2).

The additional results presented today by Dr. Heitner indicated that mavacamten treatment led to a meaningful reduction, in the first few weeks of treatment, in resting LVOT gradient with a less pronounced reduction in resting LVEF. The rapid reduction in LVOT gradient, observed in 9 out of 10 patients by week 2, supported the addition of a second, low-dose cohort in the PIONEER-HCM trial.

Furthermore, data following the washout period (from week 12 to week 16) were presented for the following measures: post-exercise peak LVOT gradient, resting LVOT gradient, resting LVEF, dyspnea score, NYHA Functional Class and NT-proBNP. For all of these measures, reversion towards baseline values was observed, on average across the cohort, after mavacamten therapy was discontinued.

“These data strengthen the case, initially seen with the release of the topline results, that mavacamten, by targeting the underlying biomechanical defect of the disease, can affect multiple clinically meaningful metrics that characterize the oHCM disease burden,” said Dr. Stephen Heitner. “On behalf of the investigators, I am pleased to present these additional data showing the concordant and positive effects of mavacamten, with patients feeling better and displaying improvements in exercise capacity.”

“Hypertrophic cardiomyopathy continues to be an area of serious unmet need and patients living with this disease have limited options,” said Marc Semigran, M.D., chief medical officer of MyoKardia. “These data increase our confidence in the mavacamten program and we look forward to advancing this program over the remainder of 2017, including the completion of study visits in our second, low-dose cohort in PIONEER-HCM, an End-of-Phase 2 meeting with the FDA and the initiation of our EXPLORER-HCM trial.”