How Do Cardiac Myosin Inhibitors Work?

Cardiac myosin inhibitors are a novel class of drug approved by the FDA in April 2022 to increase exercise capacity and improve the symptoms of a heart condition known as obstructive hypertrophic cardiomyopathy (HCM). Currently, mavacamten is the first and only drug to be approved by the FDA in this class of medications.

Hypertrophic cardiomyopathy is a genetic heart disorder that causes the muscle walls of the left ventricle to become enlarged, thick and stiff. The left ventricle is the heart chamber that pumps blood to all the organs and excessive muscle tissue in the left ventricular walls reduces the space available for blood in that chamber, and makes the heart contract too much while failing to pump blood efficiently.

Myosin is the protein in muscle fibers that converts chemical energy derived from food into mechanical energy, generating force and movement that results in muscle contraction. Myosin interacts with another protein known as actin and forms cross-bridges with actin filaments to enable the muscle fibers to contract and relax.

In hypertrophic cardiomyopathy, the left ventricular muscle fibers have excess myosin-actin cross-bridge formations and dysregulation of the relaxed state. Cardiac myosin inhibitors selectively bind to myosin in the cardiac muscle fibers and reduce the myosin-actin interactions, allowing the ventricle to relax sufficiently for blood to fill up before pumping.

Cardiac myosin inhibitors are capsules approved by the FDA to treat symptomatic New York Heart Association (NYHA) class II-III obstructive hypertrophic cardiomyopathy to improve exercise capacity and symptoms.

Side effects of cardiac myosin inhibitors may include the following:

• Dizziness
• Fainting (syncope)
• Reduced left ventricle ejection fraction (LVEF)

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of cardiac myosin inhibitors include:

• mavacamten