Mavacamten is a novel cardiac myosin inhibitor approved for symptomatic obstructive HOCM. Its mechanism of action and the key monitoring requirement during treatment are:

• A Inhibits cardiac beta-myosin heavy chain ATPase, reducing actin-myosin cross-bridge formation; echocardiographic monitoring of LVEF required (hold if LVEF < 50%) ✓
• B Inhibits cardiac troponin I; monitor troponin levels weekly
• C Blocks L-type calcium channels; monitor QTc prolongation
• D Allosteric activator of cardiac myosin; echo not required

Explanation

Mavacamten (CAMZYOS) is a first-in-class allosteric inhibitor of cardiac beta-myosin heavy chain ATPase that reduces the number of actin-myosin cross-bridges in the systolic state, decreasing myocardial contractility and dynamic LVOT obstruction. The EXPLORER-HCM trial showed significant reduction in LVOT gradient and improved symptoms. Because excessive myosin inhibition can reduce LVEF, regular echocardiographic surveillance is mandatory; the drug must be withheld if LVEF falls below 50% and dose-adjusted for LVEF 50–55%. It is also a CYP2C19 substrate with significant drug interactions.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.