How Mavacamten (Camzyos) Treats Obstructive Hypertrophic Cardiomyopathy
Camzyos, or mavacamten, treats a specific form of heart disease called obstructive hypertrophic cardiomyopathy (oHCM), where the heart muscle thickens abnormally, obstructing blood flow from the left ventricle during contraction. It reduces this obstruction by targeting the root cause in the heart's contractile machinery.[1]
Mechanism: Blocking Excessive Heart Muscle Contraction
Mavacamten is an allosteric modulator of cardiac myosin, the motor protein powering heart muscle contraction. In oHCM, a genetic mutation keeps myosin in an active state, causing hypercontractility—too-strong contractions that block outflow and strain the heart. Mavacamten binds myosin and shifts it to an energy-sparing, inactive state, reducing contractility without fully stopping the heart. This eases obstruction, lowers pressure gradients (often from >50 mmHg to <30 mmHg), and improves symptoms like shortness of breath and fatigue.[1][2]
Who Qualifies and How It's Taken
Approved by FDA in 2022 for adults with symptomatic oHCM (NYHA class II-III) despite beta-blockers or disopyramide. Patients start at 5 mg daily oral dose, titrated up to 15 mg based on echocardiogram results and drug levels to avoid under- or over-dosing. Regular monitoring (echo every 12 weeks) is required due to risks like heart failure if contraction weakens excessively.[1][3]
Clinical Results from Trials
In the EXPLORER-HCM phase 3 trial, 37% of mavacamten patients achieved ≥1.5 mL/kg/min increase in peak oxygen consumption (pVO2) plus symptom improvement, versus 17% on placebo. Post-hoc analysis showed sustained benefits over 3 years in VALOR-HCM, with 80% avoiding surgery. Improvements include better exercise capacity, quality of life, and NT-proBNP levels (a heart stress marker).[2][4]
Common Side Effects and Monitoring Needs
Dizziness (28%), heart failure (5%), syncope (6%), and palpitations occur most. Black box warning for heart failure risk requires REMS program enrollment—echo before starting, at week 4/8/12, then every 12 weeks. Avoid in pregnancy; taper off before procedures needing high cardiac output.[1][3]
How It Differs from Standard HCM Treatments
Beta-blockers or calcium channel blockers slow heart rate but don't fix hypercontractility. Mavacamten addresses the myosin defect directly, often allowing dose reductions of other drugs. Unlike surgery (septal myectomy) or alcohol ablation, it's non-invasive but requires lifelong monitoring.[2]
When Exclusivity Ends and Biosimilar Outlook
Pfizer holds U.S. patent until at least 2036 (with extensions possible). No biosimilars yet; ongoing trials test next-gen myosin inhibitors like aficamten (BMS) and CK-586.[5]
[1]: FDA Label for Camzyos
[2]: NEJM: EXPLORER-HCM Trial
[3]: Camzyos REMS Program
[4]: JACC: Long-term VALOR-HCM Data
[5]: DrugPatentWatch: Mavacamten Patents