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MyoKardia announces positive Phase 3 results

MyoKardia has announced positive topline data from the company’s Phase 3 pivotal EXPLORER-HCM clinical trial of mavacamten for the treatment of patients with symptomatic, obstructive hypertrophic cardiomyopathy (HCM) (clinicaltrials.gov NCT03470545).  Mavacamten demonstrated a robust treatment effect: the primary and all secondary endpoints of the EXPLORER trial were met with statistical significance (p≤0.0006 for all endpoints). Mavacamten was well tolerated, and meaningful improvements in symptoms, functional status and quality of life, as well as reduction or elimination in obstruction of the left ventricle, were observed among patients on treatment versus placebo.

“The extraordinary data from the EXPLORER pivotal trial confirm mavacamten’s ability to relieve dynamic outflow obstruction, control symptoms and improve quality of life in patients with hypertrophic cardiomyopathy,” said Iacopo Olivotto, M.D., Careggi University Hospital and lead clinical investigator for the EXPLORER-HCM clinical trial. “HCM is the most common inherited cardiovascular disease, and patients face an uncertain journey that all too frequently includes debilitating symptoms, as well as serious complications, such as heart failure, stroke and cardiac arrest.  Mavacamten is the first drug developed to target the specific molecular defect of the disease.  EXPLORER 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 30-week treatment with mavacamten resulted in a highly statistically significant outcome relative to placebo (p=0.0005) for the primary endpoint in the EXPLORER-HCM trial, a composite functional analysis designed to capture the treatment effect of mavacamten relative to placebo on both symptoms and cardiac function. 

All secondary endpoints also demonstrated statistically significant and clinically meaningful improvements for mavacamten as compared to placebo.  Secondary endpoints in the EXPLORER-HCM trial evaluated improvements in post-exercise left ventricular outflow tract (LVOT) peak gradient (p<0.0001), New York Heart Association (NYHA) functional classification (p<0.0001), peak VO2 (p=0.0006), the Kansas City Cardiomyopathy Clinical Summary Score (KCCQ-CSS) (p<0.0001), and the HCM Symptom Questionnaire Shortness of Breath Domain Score (p<0.0001).

Mavacamten was well tolerated and demonstrated safety results comparable to placebo, with no new findings observed. Ninety-eight percent of patients enrolled completed the study.  Of the two percent who dropped out, none were due to reduced ejection fraction or symptoms of heart failure.  Overall rates of adverse events, serious adverse events, and cardiac adverse events, including atrial fibrillation, were comparable for patients treated with mavacamten and placebo.

“The resoundingly positive data from EXPLORER bring us a significant step closer to improving the lives of people with serious cardiovascular conditions, starting with HCM, a debilitating disease estimated to affect one in every 500 people,” said Tassos Gianakakos, Chief Executive Officer of MyoKardia.  “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.” 

The EXPLORER-HCM clinical trial is part of MyoKardia’s pivotal program studying mavacamten as a treatment for symptomatic, obstructive hypertrophic cardiomyopathy.  MyoKardia plans to submit a New Drug Application to the U.S. Food and Drug Administration (FDA) in the first quarter of 2021. Results from the Phase 3 EXPLORER-HCM clinical trial will be submitted to a future professional meeting in 2020.

Source: Myocardia (press release)