Mavacamten
Cardiac myosin inhibitors
Cardiac myosin inhibitorsPregnancy: contraindicated
May harm the fetus: a pregnancy test is done before starting and effective non-hormonal contraception is used during treatment and for several months after stopping.
The first cardiac myosin inhibitor: an oral drug that reduces excess heart contraction in symptomatic obstructive hypertrophic cardiomyopathy.
Quick facts
- Group
- Cardiac myosin inhibitors
- Target
- Cardiac β-myosin (MYH7), motor domain ATPase
- Key effects
- Dizziness · Fainting
- Monitor
- Echocardiography · Symptoms of heart failure
- ATC
- C01EB24
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows mavacamten bound to human β-cardiac myosin in the folded, energy-saving 'interacting-heads' state.
Mavacamten is an allosteric, reversible and selective inhibitor of cardiac myosin ATPase. It lowers the number of myosin heads that can enter force-producing 'on-actin' states and shifts the myosin population towards the energy-sparing super-relaxed state. Systolic hypercontractility and the dynamic left ventricular outflow tract obstruction fall, and diastolic relaxation improves.
- Binds cardiac myosin at an allosteric site
- Fewer myosin heads bind actin (super-relaxed state)
- Contraction is less forceful; outflow obstruction eases
- Symptoms and exercise capacity improve
Indications
- Symptomatic obstructive hypertrophic cardiomyopathy in adults, to improve symptoms and functional capacity Hypertrophic cardiomyopathy →
Adverse effects
Common
- Dizziness
- Fainting (syncope)
Contraindications
- Starting when the left ventricular ejection fraction is already reduced (it is reserved for a preserved ejection fraction)
- Use with drugs that strongly change its levels (certain CYP2C19 or CYP3A4 inhibitors or inducers)
- Pregnancy
Key interactions
- CYP2C19 inhibitors (omeprazole, esomeprazole, fluconazole, some antidepressants) and CYP3A4 inhibitors; cimetidine
- Raise mavacamten levels and the risk of heart failure.
- CYP inducers such as St John's wort
- Lower mavacamten levels and its effect.
- Hormonal contraceptives
- Made less effective; a non-hormonal or additional method is used during treatment and for months after.
What is monitored
- Echocardiography (ejection fraction) before starting and during treatment
- Symptoms of heart failure: breathlessness, fatigue, swelling, rapid weight gain
- New medicines or supplements (interactions)
- Pregnancy test before starting
Administration and safety
- Oral, once a day, with or without food, swallowed whole.
- Available only through a restricted programme (REMS) because of heart failure risk.
- The dose is adjusted according to echocardiography; changes take weeks to show.
- Any new prescription, over-the-counter acid reducer or herbal product is checked for interactions first.
Pregnancy and breastfeeding
May harm the fetus: a pregnancy test is done before starting and effective non-hormonal contraception is used during treatment and for several months after stopping.
Nursing care
- Before: echocardiogram, pregnancy test, full medicine list (including omeprazole and St John's wort).
- During: breathlessness, oedema, weight gain, palpitations; intercurrent illness or new arrhythmia.
- Teach to report heart failure symptoms promptly.
- Teach that hormonal contraception is not reliable on mavacamten.
Pharmacokinetics
- Absorption
- Oral capsule.
- Metabolism
- Extensive, mainly by CYP2C19 and also CYP3A4; CYP2C19 poor metabolizers have much higher exposure.
- Half-life
- Very long (days, and longer in CYP2C19 poor metabolizers), so changes take weeks to settle (G&G).
Test yourself
Think of the answer, then tap the question to see it.
Which disease does mavacamten treat and what is its target?
Symptomatic obstructive hypertrophic cardiomyopathy; it inhibits cardiac β-myosin.
Why is mavacamten distributed through a restricted programme?
It can reduce contractility too much and cause systolic heart failure, so echocardiographic monitoring is mandatory.
Why can omeprazole be a problem with mavacamten?
It inhibits CYP2C19, raising mavacamten levels and the risk of heart failure.
What advice about contraception goes with mavacamten?
Hormonal contraceptives are less effective, so another method is needed during treatment and for months after.
Connections
← Back to the class: Cardiac myosin inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Mavacamten: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2022); Cryo-EM structure of human beta-cardiac myosin bound to mavacamten in the interacting-heads motif and S2-FH docked state (RCSB Protein Data Bank, 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.