Newest Medication for Hypertrophic Cardiomyopathy
Mavacamten is the newest and currently only FDA-approved medication specifically designed to treat symptomatic obstructive HCM, representing a paradigm shift as the first cardiac myosin inhibitor available for clinical use. 1, 2
Cardiac Myosin Inhibitors: A New Drug Class
Mavacamten is FDA-approved for adults with symptomatic NYHA class II-III obstructive HCM to improve functional capacity and symptoms. 2 This first-in-class agent works by inhibiting actin-myosin interaction, thereby decreasing cardiac contractility and reducing left ventricular outflow tract (LVOT) obstruction at the molecular level—directly targeting the underlying pathophysiology rather than just treating symptoms. 1, 3
Clinical Positioning in Treatment Algorithm
According to the 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guidelines, mavacamten should be used when: 3
- First-line therapy fails: Beta-blockers or nondihydropyridine calcium channel blockers (verapamil/diltiazem) provide inadequate symptom relief
- Adult patients only: Not approved for pediatric use
- Class 1 recommendation: Adding a myosin inhibitor is recommended (not just "may be considered") for persistent symptoms despite first-line therapy 3, 1
The treatment hierarchy is now: beta-blockers or calcium channel blockers → mavacamten, disopyramide, or septal reduction therapy. 3
Efficacy Data
Mavacamten improves LVOT gradients, symptoms, and functional capacity in 30-60% of patients with obstructive HCM. 3 Clinical trials (EXPLORER-HCM, VALOR-HCM) demonstrated: 4, 5
- Significant reduction in both resting and post-exercise LVOT gradients
- Improvement in peak oxygen consumption (pVO₂)
- Reduction in NYHA functional class
- Enhanced quality of life scores (KCCQ)
- Ability to defer or obviate septal reduction therapy in appropriate candidates 4
Critical Safety Considerations
Mandatory monitoring is required due to Risk Evaluation and Mitigation Strategy (REMS) program: 3
- LVEF reduction <50% occurs in 5.7% of patients attributable to the drug alone, but up to 7-10% when considering other clinical conditions 3
- This reduction is reversible with dose adjustment or temporary discontinuation 6
- Must discontinue if persistent systolic dysfunction (LVEF <50%) develops 1, 3, 1
- Contraindicated in pregnancy due to teratogenic effects 1, 3, 1
- Regular echocardiographic monitoring is essential 6
Emerging Alternative: Aficamten
Aficamten is a next-generation cardiac myosin inhibitor currently in clinical trials (not yet FDA-approved) with potential advantages: 7
- Shorter half-life than mavacamten, allowing faster dose adjustments
- Fewer drug-drug interactions
- REDWOOD-HCM trial showed sustained LVOT gradient reduction up to 48 weeks 7
- Similar efficacy profile to mavacamten 6
However, mavacamten remains the only FDA-approved cardiac myosin inhibitor as of 2024. 1, 3, 2
Common Pitfalls to Avoid
- Do not use mavacamten as first-line therapy: Beta-blockers or calcium channel blockers remain initial treatment 3
- Do not combine with vasodilators: Discontinue ACE inhibitors, ARBs, and dihydropyridine calcium channel blockers as they worsen LVOT obstruction 3
- Do not ignore LVEF monitoring: Failure to monitor can lead to symptomatic systolic dysfunction 3, 6
- Do not use in nonobstructive HCM without caution: Preliminary phase 3 data (ODYSSEY-HCM) showed primary endpoints were not met in nonobstructive HCM 6