Mavacamten, First-in-Class Therapy, May Soon Be Available for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is a chronic disease in which excessive contraction of the heart muscle can lead to the development of debilitating symptoms and cardiac dysfunction.

In patients with hypertrophic cardiomyopathy, the heart muscle becomes abnormally thick, making it harder for the heart to pump blood. The thickened heart muscle can cause shortness of breath, chest pain, or problems in the heart’s electrical system, resulting in life-threatening arrhythmias or sudden death, according to the Mayo Clinic.

In obstructive disease, the thickened heart wall can block or reduce the flow of blood from the left ventricle to the aorta.

It’s estimated that 1 in every 500 people have hypertrophic cardiomyopathy, but a large percentage of patients are undiagnosed, says the American Heart Association. Of those diagnosed, two-thirds have the obstructive form of the disease.

Commonly prescribed medications include beta blockers, anti-arrhythmic medications, calcium channel blockers, and anticoagulants, all therapies used to treat other cardiac conditions. Currently, no medication is available to specifically treat hypertrophic cardiomyopathy

But a therapy on the horizon could be the first to specifically treat the underlying cause of hypertrophic cardiomyopathy. Bristol Myers Squibb’s mavacamten is a potential first-in-class therapy that addresses the excessive contraction of the heart that leads to severe disease where the blood flow is obstructed.

In March 2021, the FDA accepted Bristol Myers Squibb’s new drug application (NDA) for mavacamten, an investigational, novel, oral medication for patients with symptomatic obstructive hypertrophic cardiomyopathy. The agency’s target date for making a decision on the application — the PDUFA date— is January 28, 2022.

The NDA is based on data from the EXPLORER-HCM phase 3 clinical trial, which enrolled 251 patients. Results from the trial showed that mavacamten demonstrated a robust treatment effect with clinically meaningful improvements in symptoms, functional status, and quality of life, as well as the ability to relieve left ventricular obstruction. Investigators found that all primary and secondary endpoints were met. The data was published last year in The Lancet.

At the 70th American College of Cardiology Scientific Session in May 2021, an analysis of the data on mavacamten effect on patients’ quality of life was presented. Data were also reported in The Lancet. The analysis was based on patient responses on the Kansas City Cardiomyopathy Questionnaire, a disease-specific measure of patients' health status. Investigators found that mavacamten improved the health status of patients compared with placebo, and a greater proportion of mavacamten patients achieved clinically meaningful improvement (≥20 points), as measured by the Kansas City questionnaire, compared with placebo, 36% vs. 15%.

“By using this tool, we were able to demonstrate substantial clinical benefits for patients taking mavacamten in the trial, which diminished when patients ended treatment,” lead study investigator, John A. Spertus, M.D., M.P.H., clinical director of outcomes research at Saint Luke’s Mid America Heart Institute in Kansas City, said in a statement.