How Camzyos Targets Obstructive Hypertrophic Cardiomyopathy
Camzyos (mavacamten) treats symptomatic obstructive hypertrophic cardiomyopathy (oHCM), a condition where thickened heart muscle blocks blood flow from the left ventricle, causing symptoms like shortness of breath and fatigue. It reduces this obstruction by selectively inhibiting myosin, the motor protein powering heart muscle contraction.[1]
Mechanism: Blocking Excessive Myosin Activity
In oHCM, genetic mutations make heart muscle hypercontractile, with myosin heads overly active and cross-bridges forming too readily between actin and myosin filaments. Camzyos binds allosterically to myosin, stabilizing an inactive "super-relaxed" state. This reduces the pool of myosin available for contraction without fully stopping it, lowering left ventricular outflow tract (LVOT) pressure gradients by 47-50 mmHg on average in trials.[1][2]
The drug increases the energy-sparing off-state of myosin ATPase, mimicking normal regulation. Unlike broad muscle relaxants, its cardiac selectivity avoids effects on skeletal muscle.[1]
Effects on Heart Function in oHCM Patients
Patients see improved exercise capacity (peak oxygen uptake rises 3.5-4 mL/kg/min), reduced New York Heart Association class symptoms, and better quality of life scores. It eases mitral valve systolic anterior motion (SAM), a key obstruction driver, in 80%+ of cases. NT-proBNP, a heart stress marker, drops 53-80%.[2][3]
Dosing and Onset of Action
Started at 5 mg daily, titrated up to 15 mg based on echocardiogram gradients and troponin levels. Steady-state effects appear in 4 weeks; full LVOT improvement by 12-16 weeks. It's taken with food for consistent absorption.[1]
Key Trial Evidence
In the EXPLORER-HCM phase 3 trial (N=251), 37% of Camzyos patients achieved ≥30% LVOT gradient reduction plus symptom improvement vs. 17% on placebo (p<0.0005). VALOR-HCM showed 80% avoided surgery at 16 weeks vs. 35% placebo.[2][3]
Patient Monitoring and Risks
Requires regular echoes and blood tests due to heart failure risk (0.7-4% incidence). Contraindicated with moderate/severe LVEF drop (<55%). Common side effects: dizziness (19-27%), syncope (6%).[1]
Who Makes Camzyos and Availability
Bristol Myers Squibb manufactures Camzyos, FDA-approved in April 2022 for NYHA class II-III oHCM adults. It's the first cardiac myosin inhibitor.[1]
[1]: Camzyos Prescribing Information (BMS, 2023)
[2]: NEJM: EXPLORER-HCM Trial (Olivotto et al., 2020)
[3]: Lancet: VALOR-HCM Trial (Olivotto et al., 2022)