Mavacamten

How it works

It selectively and reversibly inhibits cardiac myosin, reducing the number of actin-myosin cross-bridges and thereby decreasing excessive contractility and left ventricular outflow tract obstruction while improving myocardial relaxation.

Prescribing in practice

• It can reduce left ventricular ejection fraction and precipitate heart failure, so treatment requires baseline and regular echocardiographic assessment with dose interruption if ejection fraction falls below the threshold in the SPC; it is used through a controlled-access programme.
• Exposure is affected by CYP2C19 and CYP3A4 status, so genotype and interacting medicines must be considered and certain combinations are contraindicated.
• It is contraindicated in pregnancy and may reduce the effectiveness of hormonal contraception; consult the SPC before prescribing.

Monitoring

Monitor left ventricular ejection fraction by echocardiography at baseline and at regular intervals, more frequently after initiation and dose changes or with intercurrent illness.

Counselling the patient

• Advise the patient to report breathlessness, swelling or other symptoms of worsening heart failure promptly.
• Explain that regular heart scans are required and that some other medicines must be avoided.
• Counsel on the need for effective non-hormonal or additional contraception and to avoid pregnancy.

Evidence & guidelines

Mavacamten improved symptoms and outflow obstruction in the EXPLORER-HCM trial; refer to current prescribing references for licensed use.