Mavacamten (Camzyos) is a cardiac myosin inhibitor indicated for the treatment of adults with symptomatic obstructive hypertrophic cardiomyopathy (HCM), New York Heart Association (NYHA) functional class II–III, to improve functional capacity and symptoms. However, its use is associated with a range of potential risks, side effects, and strict medication management requirements that require close attention.

Side Effects of Mavacamten (Camzyos)

Cardiac Effects

(1) The primary mechanism of mavacamten is to inhibit excessive myocardial contraction, which will inevitably lead to a certain reduction in left ventricular ejection fraction (LVEF).

(2) Approximately 6% of treated patients experienced a reversible decrease in LVEF to below 50%, most of which recovered after treatment discontinuation.

Common Systemic Adverse Reactions

(1) Dizziness: Approximately 27% of patients developed dizziness.

(2) Syncope: Approximately 6% of patients reported syncope.

Side Effects of Mavacamten (Camzyos)

Heart Failure Risk

(1) This is the most serious risk of mavacamten. The drug reduces cardiac contractile function and may cause or worsen heart failure due to systolic dysfunction.

(2) Heart failure risk is significantly increased in patients with severe comorbidities (e.g., severe infection).

(3) Presence of arrhythmias (e.g., atrial fibrillation or other uncontrolled rapid arrhythmias).

(4) Concomitant use of other drugs that reduce cardiac contractility or interact with mavacamten.

Embryo-Fetal Toxicity

(1) Based on animal data, mavacamten may cause fetal harm, leading to fetal malformations, decreased fetal weight, and abnormal skeletal development.

(2) Pregnancy must be excluded in females of reproductive potential prior to initiation of treatment.

(3) Effective contraception must be used during treatment and for 4 months after the last dose.

(4) Note that mavacamten may reduce the efficacy of some progestin-containing combined hormonal contraceptives; additional non-hormonal contraceptive methods (e.g., condoms) are recommended.

Precautions for Mavacamten (Camzyos)

Pre-Treatment Evaluation

(1) Pre-treatment evaluation: LVEF must be ≥55% before initiating treatment.

(2) Regular monitoring: During treatment, LVEF and left ventricular outflow tract (LVOT) gradient under Valsalva maneuver should be monitored regularly by echocardiography (e.g., at Weeks 4, 8, 12, and every 3–6 months thereafter).

Dose Interruption and Adjustment

(1) Treatment must be interrupted if LVEF is <50% at any visit.

(2) If LVEF is between 50% and 55%, maintain the current dose and intensify monitoring.

(3) Treatment may be resumed at a reduced dose level once LVEF recovers to ≥50%.

(4) Individualized titration: Doses should be adjusted individually based on echocardiographic results and clinical symptoms, aiming to effectively reduce the LVOT gradient while maintaining LVEF ≥50%.