MyoKardia’s Experimental HCM Treatment Hits All Primary and Secondary Endpoints in Phase III Study


Shares of MyoKardia shot up more than 64% in morning trading following the company’s announcement that its lead drug mavacamten hit the mark in a Phase III study of patients with symptomatic, obstructive hypertrophic cardiomyopathy (HCM).

Following the positive results, California-based MyoKardia said it is eying early 2021 to file its first New Drug Application for mavacamten, an allosteric modulator of cardiac myosin. In the Phase III EXPLORER-HCM clinical trial, mavacamten demonstrated a robust treatment effect and met all primary and secondary endpoints. Patients who receive the drug during the trial saw meaningful improvements in symptoms, functional status and quality of life, as well as reduction or elimination in obstruction of the left ventricle, the company said. All secondary endpoints demonstrated statistically significant and clinically meaningful improvements for mavacamten as compared to placebo.  Additionally, mavacamten was well-tolerated and demonstrated safety results comparable to placebo. Full trial results from the Phase III EXPLORER-HCM study will be submitted to a future professional meeting in 2020.

MyoKardia Chief Executive Officer Tassos Giankakos said the data from the EXPLORER study takes the company closer to improving the lives of patients with serious cardiovascular conditions such as HCM. Hypertrophic cardiomyopathy is a chronic, progressive disease in which excessive contraction of the heart muscle and reduced ability of the left ventricle to fill can lead to the development of debilitating symptoms and cardiac dysfunction. It is estimated that one in every 500 people is affected by HCM, which can result in fatigue or shortness of breath, interfering with a patient’s ability to participate in activities of daily living. The condition has been associated with increased risks of atrial fibrillation, stroke, heart failure and sudden cardiac death.

“The activity and tolerability profile observed for mavacamten in this pivotal study underscores the profound impact and potential for therapeutics that target the underlying biology of disease.  We look forward to the submission of MyoKardia’s first New Drug Application and, importantly, to serving the many patients that stand to benefit from mavacamten,” Giankakos said in a statement.

Iacopo Olivotto, the lead clinical investigator for the trial, said the data from the study confirm mavacamten’s ability to relieve dynamic outflow obstruction, control symptoms and improve quality of life in patients with HCM. Mavacamten is the first drug developed to target the specific molecular defect of the disease, Olivotto noted and added that the EXPLORER study “represents a major achievement toward a precision-medicine approach in cardiomyopathies and should provide great hope to a community painfully aware of the lack of disease-specific treatment options.”

The EXPLORER-HCM clinical trial is part of MyoKardia’s pivotal program studying mavacamten as a treatment for symptomatic, obstructive hypertrophic cardiomyopathy.  In March, the company announced mavacamten demonstrated statistically significant improvements in key biomarkers of cardiac injury and wall stress in a Phase II study of patients with non-obstructive hypertrophic cardiomyopathy.


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