Table of Contents
Introduction
Camzyos is the brand name of mavacamten, an oral cardiac myosin inhibitor used in obstructive hypertrophic cardiomyopathy, commonly called obstructive HCM or oHCM.
Hypertrophic cardiomyopathy is a disease in which the heart muscle, especially the left ventricle, becomes abnormally thickened. In obstructive HCM, the thickened septum and abnormal ventricular contraction can narrow the left ventricular outflow tract, producing dynamic obstruction during blood ejection. This can cause symptoms such as shortness of breath, chest pain, palpitations, dizziness, syncope, fatigue, reduced exercise capacity, and heart failure-like symptoms.
At the sarcomere level, HCM is associated with excessive actin-myosin cross-bridge formation, hypercontractility, impaired relaxation, increased cardiac energy demand, and abnormal diastolic filling. Camzyos directly targets this sarcomeric abnormality by modulating cardiac myosin activity.
Mavacamten is described in the prescribing information as an allosteric and reversible inhibitor selective for cardiac myosin. It reduces the number of myosin heads that can enter power-generating “on actin” states, thereby reducing force-producing systolic and residual diastolic cross-bridge formation. It also shifts the myosin population toward an energy-sparing, recruitable super-relaxed state.
Camzyos is indicated for adults with symptomatic New York Heart Association class II–III obstructive HCM to improve functional capacity and symptoms.
For exam purposes, Camzyos should be remembered as an oral selective cardiac myosin inhibitor that reduces excessive actin-myosin cross-bridge formation, decreases hypercontractility, reduces left ventricular outflow tract obstruction, and improves symptoms in obstructive HCM.
Mechanism of Action (Step-wise)
Step 1: HCM involves abnormal sarcomere function
The sarcomere is the contractile unit of cardiac muscle. It contains actin and myosin filaments that interact to produce contraction. In hypertrophic cardiomyopathy, sarcomere function becomes abnormal, leading to excessive contractility and inefficient energy use.
Step 2: Excess myosin-actin interaction increases contractile force
In normal cardiac contraction, myosin heads bind to actin and form cross-bridges. These cross-bridges generate force and allow the heart muscle to contract. In obstructive HCM, too many myosin heads may remain available for actin binding, producing excessive force generation.
Step 3: Hypercontractility contributes to LVOT obstruction
Excessive contraction can worsen narrowing of the left ventricular outflow tract. The thickened interventricular septum, small ventricular cavity, and systolic anterior motion of the mitral valve can combine to obstruct blood flow from the left ventricle into the aorta.
Step 4: LVOT obstruction increases symptoms
Left ventricular outflow tract obstruction increases pressure inside the ventricle and reduces efficient forward blood flow. This contributes to dyspnea, chest pain, exertional intolerance, dizziness, syncope, and fatigue.
Step 5: Diastolic filling is also impaired
In HCM, the thickened and hypercontractile ventricle may relax poorly. Residual cross-bridge formation during diastole can contribute to impaired filling, increased filling pressures, pulmonary congestion, and shortness of breath.
Step 6: Cardiac energy demand increases
Excessive actin-myosin cycling consumes more ATP. This creates inefficient myocardial energy use and may worsen myocardial stress, ischemia-like symptoms, and elevated cardiac biomarkers.
Step 7: Camzyos binds cardiac myosin allosterically
Mavacamten binds to cardiac myosin at an allosteric regulatory site. Allosteric inhibition means the drug changes myosin function by binding away from the main actin-binding event rather than blocking a classic receptor at the cell membrane.
Step 8: Fewer myosin heads enter the power-generating state
Camzyos reduces the number of myosin heads that enter “on actin” power-generating states. This decreases the probability of force-producing systolic cross-bridge formation.
Step 9: Systolic hypercontractility decreases
Because fewer myosin heads generate force, excessive cardiac contraction is reduced. This is useful in obstructive HCM, where hypercontractility contributes to dynamic obstruction.
Step 10: Residual diastolic cross-bridge formation decreases
Mavacamten also reduces residual diastolic cross-bridge formation. This can improve relaxation and filling by reducing persistent myosin-actin interaction during diastole.
Step 11: Myosin shifts toward the super-relaxed state
Camzyos shifts the myosin population toward an energy-sparing, recruitable super-relaxed state. This helps reduce abnormal sarcomere activation and may improve myocardial efficiency.
Step 12: LVOT gradient decreases
By reducing excessive contractility, Camzyos decreases the dynamic left ventricular outflow tract gradient. In obstructive HCM, lowering the LVOT gradient can improve blood flow from the left ventricle to the aorta.
Step 13: Cardiac filling pressures improve
The label notes that in HCM patients, myosin inhibition with mavacamten reduces dynamic LVOT obstruction and improves cardiac filling pressures.
Step 14: Symptoms and functional capacity improve
Reduced obstruction and improved filling can reduce dyspnea, fatigue, dizziness, chest discomfort, and exercise limitation. This explains why Camzyos is used to improve functional capacity and symptoms in symptomatic obstructive HCM.
Step 15: Excessive inhibition can reduce LVEF
Because Camzyos reduces cardiac contractility, excessive exposure or over-response can reduce left ventricular ejection fraction and cause heart failure due to systolic dysfunction. This is the major safety concern and the reason for mandatory echocardiographic monitoring and REMS restrictions.
Pharmacokinetics
Camzyos is administered orally as mavacamten capsules. The recommended starting dose is 5 mg orally once daily, with or without food. Allowable titration doses are 2.5 mg, 5 mg, 10 mg, and 15 mg once daily, and the maximum recommended dose is 15 mg once daily. Capsules should be swallowed whole and should not be broken, opened, or chewed.
Mavacamten has an estimated oral bioavailability of at least 85%. The median time to maximum plasma concentration is about 1 to 2 hours. Food does not produce clinically significant changes in mavacamten exposure, so it can be taken without regard to meals.
Plasma protein binding of mavacamten is high, approximately 97% to 98%. Its pharmacokinetics are strongly influenced by CYP2C19 metabolic status.
Mavacamten has a variable terminal half-life. In CYP2C19 normal metabolizers, the terminal half-life is about 6 to 9 days. In CYP2C19 poor metabolizers, the half-life is prolonged to about 23 days. This is important because poor metabolizers can have higher drug exposure and greater risk of excessive negative inotropy.
Mavacamten is extensively metabolized, primarily by CYP2C19, with additional metabolism by CYP3A4 and CYP2C9. The prescribing information reports approximate metabolic contributions of CYP2C19 74%, CYP3A4 18%, and CYP2C9 8%.
After radiolabeled mavacamten dosing, most drug-related material is recovered in urine, with a smaller amount recovered in feces. Only a small fraction is excreted unchanged.
Drug interactions are clinically very important. Strong CYP2C19 inhibitors are contraindicated because they can increase mavacamten exposure and raise the risk of heart failure due to systolic dysfunction. Moderate to strong CYP2C19 inducers and moderate to strong CYP3A4 inducers are also contraindicated because they can reduce mavacamten exposure and may reduce effectiveness; stopping an inducer can also raise mavacamten levels and increase heart failure risk.
Camzyos is also an inducer of CYP3A4, CYP2C9, and CYP2C19, so it may reduce plasma concentrations of drugs that are substrates of these enzymes. It can also reduce exposure to some hormonal contraceptive components, so contraception counseling is important.
Clinical Uses
Camzyos is used for adults with symptomatic New York Heart Association class II–III obstructive hypertrophic cardiomyopathy to improve functional capacity and symptoms.
It is used in obstructive HCM where excessive cardiac myosin activity, hypercontractility, and dynamic LVOT obstruction contribute to symptoms. The aim is to reduce obstruction, improve filling pressures, and improve exercise tolerance.
Camzyos is not a general heart failure drug. It is specifically used in symptomatic obstructive HCM, not routine systolic heart failure. Because it can reduce LVEF, it must be used carefully with echocardiographic monitoring.
Camzyos is not a beta-blocker, calcium channel blocker, antiarrhythmic, diuretic, anticoagulant, or surgical treatment. It is a disease-specific sarcomere-targeted therapy that directly reduces excessive cardiac myosin activity.
Camzyos is not a treatment for non-obstructive HCM unless specifically approved in a given jurisdiction or studied in a trial setting. In the U.S. label, the approved indication is symptomatic NYHA class II–III obstructive HCM in adults.
Camzyos may reduce the need for septal reduction therapy in some appropriately selected patients, but it is not the same as septal myectomy or alcohol septal ablation. Septal reduction procedures mechanically reduce obstruction, while mavacamten pharmacologically reduces hypercontractility and LVOT gradient.
Camzyos is not approved for pediatric patients. Pediatric safety and effectiveness have not been established in the U.S. prescribing information.
Adverse Effects
The most important safety warning of Camzyos is heart failure due to systolic dysfunction. Camzyos reduces left ventricular ejection fraction and can cause heart failure. Echocardiographic assessment of LVEF is required before and during treatment. Initiation is not recommended when LVEF is less than 55%, and treatment should be interrupted if LVEF falls below 50% or if heart failure symptoms or worsening clinical status occur.
Symptoms that may suggest heart failure include new or worsening shortness of breath, chest pain, fatigue, palpitations, leg swelling, rapid weight gain, dizziness, syncope, or reduced exercise tolerance.
Because of the risk of heart failure due to systolic dysfunction, Camzyos is available only through the Camzyos REMS Program. Prescribers, patients, and pharmacies must follow REMS requirements, including ongoing monitoring.
Drug interactions are a major safety issue. Camzyos is primarily metabolized by CYP2C19 and CYP3A4. Drugs that inhibit or induce these enzymes can cause life-threatening interactions, including heart failure or loss of effectiveness. Patients should inform healthcare providers about all prescription drugs, over-the-counter drugs, and supplements before and during treatment.
Concomitant use with other negative inotropes can increase the risk of systolic dysfunction. The label advises avoiding Camzyos with disopyramide, ranolazine, verapamil with a beta-blocker, or diltiazem with a beta-blocker because these combinations may increase the risk of heart failure symptoms and reduced ventricular function.
Dizziness and syncope are important adverse reactions. In clinical trial labeling, adverse reactions occurring in more than 5% of patients and more commonly with Camzyos than placebo were dizziness and syncope.
Embryo-fetal toxicity is another warning. Camzyos may cause fetal harm. Females of reproductive potential should use effective contraception during treatment and for 4 months after the last dose. Combined hormonal contraceptives may be affected because mavacamten can induce CYP enzymes, so counseling on reliable contraception is important.
Overexposure can cause excessive reduction in contractility. Potential overdose-related cardiovascular effects include reduced LVEF, heart failure, hypotension, and asystole. Neurological effects may include dizziness and syncope.
Comparative Analysis
Camzyos is commonly compared with beta-blockers, non-dihydropyridine calcium channel blockers, disopyramide, septal myectomy, alcohol septal ablation, and other emerging cardiac myosin inhibitors.
Compared with beta-blockers such as metoprolol, atenolol, or propranolol, Camzyos has a more disease-specific sarcomeric mechanism. Beta-blockers reduce heart rate, myocardial oxygen demand, and adrenergic stimulation. Camzyos directly inhibits cardiac myosin and reduces excessive actin-myosin cross-bridge formation.
Compared with verapamil or diltiazem, Camzyos targets cardiac myosin rather than L-type calcium channels. Verapamil and diltiazem reduce contractility and heart rate through calcium-channel blockade, while Camzyos reduces hypercontractility at the myosin-actin level. Combining some negative inotropes with Camzyos may increase systolic dysfunction risk.
Compared with disopyramide, Camzyos is not primarily an antiarrhythmic sodium-channel blocker. Disopyramide reduces obstruction mainly through its negative inotropic effect, while Camzyos reduces sarcomere hypercontractility by selectively inhibiting cardiac myosin.
Compared with diuretics, Camzyos does not primarily remove fluid. Diuretics may relieve congestion in selected patients but can worsen obstruction in some HCM patients if preload falls too much. Camzyos directly targets the contractile mechanism behind dynamic obstruction.
Compared with septal myectomy, Camzyos is a non-surgical oral therapy. Septal myectomy physically removes part of the thickened septum to relieve obstruction, while Camzyos pharmacologically reduces hypercontractility and LVOT gradient.
Compared with alcohol septal ablation, Camzyos does not intentionally create a septal infarct. Alcohol septal ablation reduces obstruction by causing controlled thinning of septal tissue. Camzyos reduces obstruction by changing cardiac myosin activity.
Compared with conventional heart failure drugs used for reduced ejection fraction, Camzyos has the opposite clinical concern. Many heart failure therapies aim to improve outcomes in systolic dysfunction, whereas Camzyos can reduce systolic function and must be monitored carefully to avoid excessive LVEF reduction.
MCQs
- Camzyos contains which active drug?
a) Aficamten
b) Mavacamten
c) Metoprolol
d) Disopyramide
Answer: b) Mavacamten
- Camzyos belongs to which pharmacological class?
a) Cardiac myosin inhibitor
b) Beta-1 selective blocker
c) Calcium channel blocker
d) Sodium channel blocker
Answer: a) Cardiac myosin inhibitor
- Camzyos is mainly used for:
a) Acute myocardial infarction
b) Symptomatic obstructive hypertrophic cardiomyopathy in adults
c) Bacterial endocarditis
d) Pulmonary embolism
Answer: b) Symptomatic obstructive hypertrophic cardiomyopathy in adults
- Mavacamten is best described as:
a) Irreversible beta receptor antagonist
b) Allosteric and reversible cardiac myosin inhibitor
c) Direct thrombin inhibitor
d) ACE inhibitor
Answer: b) Allosteric and reversible cardiac myosin inhibitor
- Camzyos reduces the number of myosin heads that enter:
a) “On actin” power-generating states
b) Dopamine-bound states
c) Acetylcholine-bound states
d) Insulin-bound states
Answer: a) “On actin” power-generating states
- In obstructive HCM, Camzyos helps reduce:
a) Left ventricular outflow tract obstruction
b) Bacterial growth
c) Blood glucose
d) Platelet aggregation
Answer: a) Left ventricular outflow tract obstruction
- The sarcomeric interaction directly modified by Camzyos is:
a) Actin-myosin cross-bridge formation
b) DNA base pairing
c) Antigen-antibody binding
d) Dopamine transporter recycling
Answer: a) Actin-myosin cross-bridge formation
- Camzyos shifts myosin toward which state?
a) Super-relaxed energy-sparing state
b) Fully phosphorylated platelet state
c) Activated coagulation state
d) GABA-bound inhibitory state
Answer: a) Super-relaxed energy-sparing state
- The recommended starting dose of Camzyos is:
a) 5 mg orally once daily
b) 40 mg orally twice daily
c) 300 mg IV every 4 weeks
d) 1 mg subcutaneously weekly
Answer: a) 5 mg orally once daily
- The maximum recommended dose of Camzyos is:
a) 15 mg orally once daily
b) 80 mg orally once daily
c) 200 mg twice daily
d) 600 mg IV every 6 months
Answer: a) 15 mg orally once daily
- Camzyos therapy requires monitoring of:
a) Left ventricular ejection fraction by echocardiography
b) Blood glucose every hour only
c) Serum lithium only
d) INR in every patient
Answer: a) Left ventricular ejection fraction by echocardiography
- Camzyos should be interrupted if LVEF falls below:
a) 50%
b) 80%
c) 75%
d) 90%
Answer: a) 50%
- The boxed warning of Camzyos is mainly for:
a) Heart failure due to systolic dysfunction
b) Severe hypoglycemia
c) Thyroid C-cell tumors
d) Ototoxicity
Answer: a) Heart failure due to systolic dysfunction
- Camzyos is available only through:
a) Camzyos REMS Program
b) iPLEDGE only
c) Clozapine REMS only
d) Opioid REMS only
Answer: a) Camzyos REMS Program
- Which statement best describes Camzyos?
a) It selectively and reversibly inhibits cardiac myosin, reducing excessive actin-myosin cross-bridge formation in obstructive HCM
b) It blocks beta-1 receptors to reduce heart rate only
c) It inhibits bacterial cell wall synthesis
d) It dissolves coronary thrombi by activating plasminogen
Answer: a) It selectively and reversibly inhibits cardiac myosin, reducing excessive actin-myosin cross-bridge formation in obstructive HCM
FAQs
What is the mechanism of action of Camzyos?
Camzyos, or mavacamten, is a selective, allosteric, reversible cardiac myosin inhibitor. It reduces the number of myosin heads entering power-generating actin-bound states, decreases actin-myosin cross-bridge formation, lowers hypercontractility, reduces LVOT obstruction, and improves filling pressures in obstructive HCM.
What is the generic name of Camzyos?
The generic name of Camzyos is mavacamten.
What is Camzyos used for?
Camzyos is used for adults with symptomatic New York Heart Association class II–III obstructive hypertrophic cardiomyopathy to improve functional capacity and symptoms.
Is Camzyos a beta-blocker?
No. Camzyos is not a beta-blocker. Beta-blockers reduce adrenergic stimulation and heart rate, while Camzyos directly inhibits cardiac myosin at the sarcomere level.
Is Camzyos a calcium channel blocker?
No. Camzyos is not a calcium channel blocker. It does not primarily block L-type calcium channels. It directly reduces cardiac myosin activity and actin-myosin cross-bridge formation.
Why can Camzyos cause heart failure?
Camzyos reduces cardiac contractility. If contractility is reduced too much, left ventricular ejection fraction can fall and heart failure due to systolic dysfunction can occur.
Why is echocardiography required with Camzyos?
Echocardiography is required to monitor LVEF and obstruction during treatment. Camzyos dosing is adjusted based on cardiac function and clinical status.
What is the Camzyos REMS Program?
The Camzyos REMS Program is a restricted safety program required because Camzyos can cause heart failure due to systolic dysfunction. It ensures prescriber, patient, and pharmacy requirements are followed.
References
Goodman & Gilman’s The Pharmacological Basis of Therapeutics
Katzung Basic & Clinical Pharmacology
