Mavacamten Controlled Hypertrophic Cardiomyopathy for >1
The study followed 231 patients with symptomatic HOCM who had completed the 30-week pivotal trial of mavacamten, EXPLORER-HCM, and opted to continue on open-label extended treatment with mavacamten, either continuing the treatment they started during the trial or crossing over to receive mavacamten after receiving placebo during the trial.

The major findings from EXPLORER-LTE (long-term extension) were that continued treatment for a median of about 62 weeks maintained the safety and efficacy findings seen at the end of the blinded, randomized, initial 30-week phase. The patients on mavacamten included in the long-term extension reported by Dr. Rader averaged 60 years of age, and 61% were men. They averaged a 35.6–mm Hg drop in their resting left ventricular outflow tract (LVOT) gradient after 48 weeks on treatment, and a 32.8–mm Hg reduction after 84 weeks. When the investigators measured their LVOT gradient during a valsalva maneuver, their reductions from baseline averaged 45.3 mm Hg after 48 weeks and 46.4 mm Hg after 84 weeks.

Resting left ventricular ejection fraction also fell, by an average of 7.0 percentage points from baseline after 48 weeks, and by an average of 9.0 percentage points after 84 weeks. After 48 weeks on treatment, 68% of patients had at least a one-class improvement from baseline in their New York Heart Association functional class.

The safety results showed that most treatment-related adverse events were mild or moderate, and about 2% of patients had a serious drug-related adverse event. Ten of the 231 patients discontinued mavacamten because of a treated-related adverse event.