Mavacamten (Camzyos) is a novel cardiac myosin inhibitor indicated for the treatment of adults with symptomatic obstructive hypertrophic cardiomyopathy (HCM) of New York Heart Association (NYHA) functional Class Ⅱ–Ⅲ. It provides a new therapeutic option for these patients by improving their functional capacity and symptoms.

What are the precautions for mavacamten (Camzyos)?

Heart Failure Risk Warning

The core risk of mavacamten is the potential to cause heart failure due to systolic dysfunction.

The drug reduces left ventricular ejection fraction (LVEF). Initiation of treatment is absolutely contraindicated in patients with LVEF < 55%.

During treatment, if LVEF decreases to < 50%, or the patient develops heart failure symptoms or clinical deterioration, the drug must be interrupted immediately.

Any new or worsening symptoms such as dyspnea, chest pain, fatigue, palpitations, or lower extremity edema should prompt timely assessment of cardiac function.

Drug Interactions

Concomitant use is contraindicated:

Strong CYP2C19 inhibitors (e.g., fluconazole, fluvoxamine), and moderate to strong CYP2C19 or CYP3A4 inducers (e.g., rifampicin, carbamazepine, phenytoin sodium, St. John’s Wort).

Caution and dose adjustment:

When co-administered with weak to moderate CYP2C19 inhibitors (e.g., omeprazole, esomeprazole) or moderate to strong CYP3A4 inhibitors (e.g., verapamil, diltiazem, clarithromycin), dose adjustment of mavacamten and intensified monitoring are required.

Obligation to inform:

Patients must inform their doctors of all medications being taken, including over-the-counter drugs (e.g., certain gastric medications) and supplements.

Monitoring for Mavacamten (Camzyos)

Echocardiographic Monitoring

Baseline assessment before treatment:

Must include LVEF and left ventricular outflow tract (LVOT) gradient under Valsalva maneuver.

Treatment initiation and dose titration phase:

Per the algorithms in Figure 1 (initiation phase) and Figure 2 (maintenance phase), regularly assess LVEF and LVOT gradient at Weeks 4, 8, 12, etc., to guide dose adjustment. The goal is to achieve an appropriate reduction in LVOT gradient while maintaining LVEF ≥ 50%.

Long-term maintenance phase:

Even with a stable dose, clinical status and echocardiography should be repeated every 3–6 months.

Interruption and reinitiation guidance:

If LVEF < 50%, treatment must be interrupted immediately, with repeat assessments every 4 weeks until LVEF recovers to ≥ 50%, after which reinitiation at a lower dose may be considered.

Concomitant Medication and Health Status Monitoring

Comorbidities:

If patients develop concurrent illnesses that may affect cardiac function (e.g., severe infection) or arrhythmias (e.g., atrial fibrillation), dose escalation should be delayed and interruption of mavacamten should be considered.

Avoid specific combinations:

Concomitant use of negative inotropic drugs such as diltiazem, ranolazine, verapamil combined with beta-blockers should be avoided to reduce the risk of left ventricular systolic dysfunction and heart failure symptoms.