Cardiac myosin (inhibitor)

Class

Selective cardiac myosin inhibitor

Cardiac myosin is the motor protein within heart muscle cells that, together with actin filaments, forms the contractile apparatus of the sarcomere—the basic unit responsible for generating force during each heartbeat. Myosin uses energy from ATP hydrolysis to cycle through binding and release of actin, producing the cross-bridge motion that shortens muscle fibers. In hypertrophic cardiomyopathy, a disease often caused by mutations in sarcomeric proteins, this cycling becomes excessive, leading to hypercontractility, thickened heart muscle, impaired relaxation between beats, and in many cases obstruction of blood outflow from the heart. A selective cardiac myosin inhibitor reduces the number of myosin heads available to engage actin at any given time, dampening excessive force generation without eliminating normal contraction. This rebalancing can ease outflow obstruction, improve the heart's ability to relax and fill with blood, and reduce the workload-related symptoms associated with hypertrophic cardiomyopathy. Because this mechanism targets the fundamental engine of contraction rather than a specific mutation, it is applicable across genetically diverse forms of the disease, including both obstructive and non-obstructive presentations. This approach represents a shift from earlier therapies that indirectly modulated heart rate or contractility toward directly correcting the underlying biomechanical abnormality at the sarcomere.