MyoKardia Inc. (NASDAQ: MYOK) shares made an incredible gain on Monday after the company announced positive results from its late-stage pivotal clinical trial of mavacamten in patients with symptomatic, obstructive hypertrophic cardiomyopathy (HCM).

Overall, mavacamten demonstrated a robust treatment effect. The primary and all secondary endpoints of the Explorer trial were met with statistical significance. 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 30-week treatment with mavacamten resulted in a highly statistically significant outcome relative to placebo for the primary endpoint in the Explorer-HCM trial.

All secondary endpoints also demonstrated statistically significant and clinically meaningful improvements for mavacamten as compared to placebo. Secondary endpoints in the trial evaluated improvements in post-exercise left ventricular outflow tract peak gradient and the HCM Symptom Questionnaire Shortness of Breath Domain Score.

Overall, mavacamten was well tolerated. Ninety-eight percent of patients enrolled completed the study. Of those 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.

Iacopo Olivotto, M.D., Careggi University Hospital and lead clinical investigator for the Explorer-HCM clinical trial, commented:

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. 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.

MyoKardia stock traded up about 64% on Monday to $100.54, in a 52-week range of $42.65 to $104.26. The consensus price target is $88.80.

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