Mavacamten is a pioneering cardiac myosin allosteric inhibitor primarily used for the treatment of symptomatic obstructive hypertrophic cardiomyopathy (oHCM). Clinical studies have shown that it can significantly improve patient symptoms and exercise capacity. However, it is essential to strictly follow the dosage adjustment protocol, and gradually reduce the dosage when discontinuing the medication to avoid disease rebound.

1. Therapeutic effect

(1) Symptom improvement: The EXPLORER-HCM Phase III trial showed that after 30 weeks of treatment, 62% of patients experienced an improvement of ≥1 NYHA functional class, compared to 21% in the placebo group.

(2) Exercise endurance: The average increase in peak oxygen uptake was 1.4 mL/kg/min, which was significantly better than that of the placebo group (P<0.0001).

(3) Hemodynamics: The pressure gradient in the left ventricular outflow tract was reduced by an average of 36 mmHg, significantly alleviating the degree of obstruction.

2. Precautions for drug withdrawal

(1) Gradual dosage reduction: Discontinue the medication under the guidance of a doctor through a dosage reduction scheme with 4-week intervals (e.g., 15mg→10mg→5mg→2.5mg).

(2) Rebound monitoring: Abrupt discontinuation of medication may lead to symptom rebound and an increase in left ventricular outflow tract (LVOT) pressure gradient. Cardiac function and symptoms should be continuously monitored for 8 weeks after discontinuation.

(3) Restart conditions: If re-treatment is necessary, it must start from the lowest dose (2.5mg) and be gradually adjusted based on echocardiogram results.

3. Special precautions

(1) Cardiac function monitoring: During treatment, LVEF should be assessed every 4-6 weeks. If it is less than 50%, drug administration should be suspended.

(2) Drug interactions: Avoid concomitant use with strong CYP2C19 inhibitors/inducers, and dosage adjustments may be necessary.

(3) Pregnancy Contraindications: Animal studies have shown embryotoxicity, and women of childbearing age need to take highly effective contraceptive measures.

4. Adverse reaction management

(1) Common reactions: dizziness (27%), fatigue (12%), etc., which are usually mild and reversible.

(2) Serious risks: May cause worsening of heart failure. If breathing difficulty or edema occurs, seek medical attention immediately.