Adult: To improve functional capacity and symptoms in patients with NYHA class II-III: Initially, 5 mg once daily. Max: 15 mg once daily. Assess patients for early clinical response by left ventricular outflow tract (LVOT) gradient with Valsalva manoeuvre at 4 and 8 weeks of treatment and titrate dose accordingly. Dose reduction, dosing interruption or discontinuation may be required according to individual safety and tolerability (refer to detailed product guidelines).
What are the brands available for Mavacamten in Hong Kong?
Mavacamten is mainly metabolised by CYP2C19 enzyme. Genetic variation in CYP2C19 may affect the pharmacokinetics of mavacamten. The prevalence of individuals who are CYP2C19 poor metabolisers is approximately 2% in European ancestry, 4% in African ancestry, and 13% in East Asian ancestry. The European Medicines Agency (EMA) drug label requires genotyping for CYP2C19 considered prior to initiating mavacamten treatment; if treatment starts prior to genotyping, patient should follow the dosing instructions for poor metabolisers until CYP2C19 phenotype is determined.
CYP2C19 poor metabolisers
Individuals carrying 2 non-functional alleles (e.g. *2/*2, *2/*3, *3/*3) may have an increased mavacamten exposure (up to 3 times), resulting in an increased risk of systolic dysfunction compared to CYP2C19 normal metabolisers. The EMA drug label recommends a starting dose of 2.5 mg once daily. Max: 5 mg once daily. In contrast, the US Food and Drug Administration (US FDA) drug labelling does not recommend any alterations in therapy based on CYP2C19 genotype or phenotype and instead recommends a starting dose of 5 mg once daily in all patients. Both EMA and US FDA drug labelling recommend assessment of patients for early clinical response by LVOT gradient with Valsalva manoeuvre at 4 and 8 weeks of treatment.
Additionally, the EMA drug label recommends dose modifications and/or additional monitoring in patients initiating, discontinuing, or changing dose of concomitant CYP2C19/CYP3A4 inhibitors or inducers due to the risk of heart failure or loss of therapeutic response to mavacamten (refer to detailed product guidelines).
CYP2C19 intermediate, normal, rapid, or ultra-rapid metabolisers
The EMA drug label recommends a starting dose of 5 mg once daily for all other CYP2C19 phenotypes. Max: 15 mg once daily. In contrast, the US FDA drug labelling does not recommend any alterations in therapy based on CYP2C19 genotypes or phenotypes and instead recommends a starting dose of 5 mg once daily in all patients. Both EMA and FDA recommend assessment of patients for early clinical response by LVOT gradient with Valsalva manoeuvre at 4 and 8 weeks of treatment.
Additionally, the EMA drug label recommends dose modifications and/or additional monitoring in patients initiating, discontinuing, or changing dose of concomitant CYP2C19/CYP3A4 inhibitors or inducers due to the risk of heart failure or loss of therapeutic response to mavacamten (refer to detailed product guidelines).
Dosage recommendations may vary between countries. Refer to specific country guidelines for the appropriate clinical recommendations.
Hepatic Impairment
Mild to moderate (Child-Pugh class A or B): 2.5 mg once daily. Dosage recommendations may vary among individual products and between countries (refer to specific product guidelines).
Administration
Mavacamten May be taken with or without food. Swallow whole, do not break/crush/open.
Contraindications
Pregnancy and women of childbearing potential not using effective contraception. Concomitant use with moderate to strong CYP2C19 inhibitors or strong CYP3A4 inhibitors; moderate to strong CYP2C19 or CYP3A4 inducers. Concomitant use with strong CYP2C19 or CYP3A4 inhibitors in CYP2C19 poor metabolisers and those with undetermined CYP2C19 phenotype. Contraindications may vary among individual products and between countries (refer to specific product labelling for detailed information).
Special Precautions
Patient with serious intercurrent illness (e.g. infection), arrhythmia (e.g. atrial fibrillation or other uncontrolled tachyarrhythmias). Patient undergoing surgery. CYP2C19 poor metabolisers. Do not initiate treatment in patients with LVEF <55%. Hepatic and severe renal (eGFR <30 mL/min/1.73 m2) impairment. Lactation.
Adverse Reactions
Significant: Decreased LVEF which may cause heart failure. Cardiac disorders: Systolic dysfunction. Nervous system disorders: Dizziness, syncope. Respiratory, thoracic and mediastinal disorders: Dyspnoea.
PO: Z (Embryo-foetal toxicities were observed in animal studies. Not recommended.)
Patient Counseling Information
This drug may cause dizziness, if affected, do not drive or operate machinery. Women of childbearing potential must use proven birth control methods during therapy and for 6 months after the treatment; additional non-hormonal methods of effective contraception may be required when used with certain combined hormonal contraceptives.
Monitoring Parameters
Perform ECG and assess LVEF and LVOT gradient prior to treatment initiation, during dose titration, and regularly during therapy. Confirm pregnancy status before treatment initiation. Monitor for signs and symptoms of heart failure (e.g. new or worsening dyspnoea, chest pain, fatigue, palpitations, leg oedema).
Overdosage
Symptoms: Dizziness, syncope, reduced LVEF, vasovagal reaction, hypotension, asystole. Management: Supportive treatment. Closely monitor vital signs and LVEF. Administration of activated charcoal within 2 hours (fasted state) or beyond 2 hours (under fed conditions) of ingestion may be considered to reduce absorption.
Drug Interactions
Increased serum concentration and risk of heart failure due to systolic dysfunction with moderate to strong CYP2C19 inhibitors and strong CYP3A4 inhibitors. Reduced therapeutic effect with moderate to strong CYP2C19 or CYP3A4 inducers. Increased risk of left ventricular systolic dysfunction and heart failure symptoms with disopyramide, ranolazine, verapamil, β-blockers, or diltiazem. May reduce plasma concentrations of CYP3A4, CYP2C9, or CYP2C19 substrates. May decrease exposure of certain progestins, leading to contraceptive failure.
Food Interaction
Increased serum concentration with grapefruit juice.
Action
Description: Mechanism of Action: Mavacamten is a selective, reversible, allosteric cardiac myosin inhibitor. It modulates the number of myosin heads that enter the power-generating states during systole and diastole, thereby reducing actin-myosin cross-bridge formation. This action leads to stable cardiac contractility, reduced dynamic left ventricular outflow tract (LVOT) obstruction, and improved cardiac filling pressures. Pharmacokinetics: Absorption: Readily absorbed from the gastrointestinal tract. Bioavailability: ≥85%. Time to peak plasma concentration: 1 hour (fasted state); 4 hours (with high-fat meal). Distribution: Plasma protein binding: 97-98%. Metabolism: Extensively metabolised in the liver mainly by CYP2C19, CYP3A4 and CYP2C9 enzymes. Excretion: Mainly via urine (85%; 3% as unchanged drug); faeces (7%; 1% as unchanged drug). Elimination half-life: 6-9 days (CYP2C19 normal metabolisers); 23 days (CYP2C19 poor metabolisers).
Chemical Structure
Mavacamten Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 117761397, Mavacamten. https://pubchem.ncbi.nlm.nih.gov/compound/Mavacamten. Accessed June 26, 2025.
C01EB24 - mavacamten ; Belongs to the class of other cardiac preparations.
References
Annotation of EMA Label for Mavacamten and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org. Accessed 30/04/2025.Annotation of FDA Label for Mavacamten and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org. Accessed 30/04/2025.Annotation of HCSC Label for Mavacamten and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org. Accessed 30/04/2025.Brayfield A, Cadart C (eds). Mavacamten. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 30/04/2025.Camzyos 2.5 mg Hard Capsules (Bristol-Myers Squibb Pharma EEIG). MHRA. https://products.mhra.gov.uk. Accessed 30/04/2025.Camzyos Capsule, Gelatin Coated (Myokardia, Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 30/04/2025.CYP2C19 - Mavacamten. UpToDate Lexidrug, Pharmacogenomics Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 30/04/2025.Joint Formulary Committee. Mavacamten. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 30/04/2025.Kopozgo 2.5 mg, 5 mg, 10 mg, 15 mg Capsules (DKSH Malaysia Sdn Bhd). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 30/04/2025.Mavacamten. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 30/04/2025.Mavacamten. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 30/04/2025.
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