Mavacamten is an investigational therapy for the treatment of hypertrophic cardiomyopathy (HCM), a condition where the heart muscle wall thickens, becomes stiff, and makes it harder for the heart to pump blood. In obstructive HCM (sometimes referred to as oHCM or HOCM), the thickened muscle also blocks blood flow from the heart. The EXPLORER-HCM trial compared mavacamten to placebo (a pill with no medicine/active substances) in symptomatic people with obstructive HCM who had exercise limitations and suffered from shortness of breath, tiredness, palpitations, and chest pain. The study showed that mavacamten reduced the obstruction that restricts blood flow and improved people's symptoms, well-being, and ability to participate in daily activities. Side effects, such as irregular heartbeat, palpitations, rapid heartbeat, and heart failure, were similar for people who received mavacamten or placebo. To read the full Plain Language Summary of this article, click on the View Article button above and download the PDF. Clinical Trial Registration: NCT03470545 (ClinicalTrials.gov).