in pictures and a few words
What it is and why it matters
Mavacamten is a once-a-day capsule for a disease in which the heart muscle is thickened and, as it contracts, itself blocks the outflow of blood from the heart.
- It is for people who have symptoms: breathlessness, chest pain, fainting on exertion
The heart is not weak but too strong
This is a disease written into the genes. The heart muscle is thickened, most often the wall between its two halves. The heart contracts too strongly and relaxes less well.
- As it contracts, the thickened wall together with a valve blocks the outflow of blood
- Hence breathlessness on exertion, chest pain, dizziness and fainting
How the medicine works
A muscle contracts when tiny “hooks” of one protein grab the filaments of another and pull them. In this disease there are too many such couplings.
- The medicine reduces the number of “hooks” ready to grab
- The heart contracts more calmly and relaxes better
- The obstruction to blood outflow shrinks and breathlessness eases
What is new about it
Earlier tablets eased the heart’s working conditions, and operations removed part of the thickened wall. Mavacamten is the first to act on the mechanism of excess contraction force itself.
- It is prescribed when usual treatment does not bring enough relief, not instead of it
Exercise becomes easier
In the study carried out before a medicine is approved, people on mavacamten more often than those on a dummy pill came to tolerate exertion better and get less breathless.
- The benefit held even when mavacamten was the only medicine for this disease
Tested in people. Tested in people: a study in people with this form of the disease and symptoms, compared with a dummy pill.
The effect comes gradually
Improvement develops gradually. It is judged by how a person tolerates exertion and by a heart ultrasound, not by a feeling that “it got easier at once”.
- If you stop taking it, the condition returns to where it started
- The medicine holds the disease in check but does not remove its genetic cause
How it is taken
One capsule a day. It usually starts at 5 mg, and then the dose is adjusted by heart ultrasound.
- The ultrasound is done before treatment starts, while the dose is being adjusted, and then every 12 weeks
Why so many heart ultrasounds
The medicine reduces the force of contraction. In the right measure this is treatment; in excess it is heart failure: the heart can no longer cope with its work.
- The ultrasound shows whether contraction has become too weak
- If the force of contraction falls below the set limit, treatment is paused
- In the US the medicine is dispensed only if the checks stay on schedule
Important. A heart ultrasound is part of the treatment, not a formality. The drug must not be used without it.
Who should see a doctor first
This is not a medicine “for the heart in general”: it is needed only for this form of the disease, confirmed by a heart ultrasound.
- Not for pregnant women; women who could become pregnant need reliable contraception
- With some medicines a different dose is needed, and some must not be combined with it
- If the heart already contracts weakly (heart failure), the drug is not prescribed
Important. During an infection or a bout of rapid heartbeat the force of contraction may drop — treatment is reviewed for that time.
In one sentence
Mavacamten calms an over-strong heart, and in the study people more often tolerated exertion better, while regular heart ultrasounds make the treatment safe.
Key points
Mavacamten (brand name Camzyos, Bristol Myers Squibb) is the first-in-class cardiac myosin inhibitor, taken once daily. It is the first to act on the mechanism of excessive contraction itself rather than easing the heart's working conditions.
| Situation | How it helps | What human studies showed |
|---|---|---|
| Symptomatic obstructive hypertrophic cardiomyopathy | the outflow obstruction eases, exercise is better tolerated, breathlessness lessens | EXPLORER-HCM (Lancet, 2020), phase 3: improved the composite endpoint — functional class and exercise capacity — significantly more often than placebo [1] |
| Monotherapy | helps even when it is the only drug for this cardiomyopathy | an integrated analysis of later data confirms the effect in monotherapy [2] |
How it helps
What happens in this disease
Hypertrophic cardiomyopathy is a genetically determined thickening of the heart muscle, most often the interventricular septum. The key misconception: the heart here is not weak but excessively strong.
At molecular level, contraction depends on cross-bridges: myosin heads grab actin filaments and pull. In this disease the proportion of myosin ready to engage is increased — the muscle contracts excessively and relaxes poorly.
Then mechanics take over: in systole the thickened septum together with the anterior mitral leaflet blocks the outflow of blood into the aorta. The resulting outflow tract obstruction produces breathlessness, chest pain, dizziness and syncope.
What was available before, and what changed
| Approach | What it does | Limitation |
|---|---|---|
| Beta blockers | Lower rate and indirectly force of contraction | Do not address the molecular cause; effect often incomplete |
| Verapamil, disopyramide | Affect contractility and filling | Tolerability, limited effect |
| Septal myectomy (surgery) | Removes part of the thickened septum | Surgery, requires an experienced centre |
| Alcohol septal ablation | Induces a controlled infarct of septal tissue | Invasive, risk of conduction block |
| Mavacamten | Reduces the number of active actin-myosin bridges | Requires ejection fraction monitoring |
Aficamten (Myqorzo): the next generation
| Mavacamten | Aficamten | |
|---|---|---|
| Class | Cardiac myosin inhibitor | Cardiac myosin inhibitor |
| Half-life | Long | Shorter |
| Titration | Slower, less frequent steps | Faster and more flexible |
| Reversibility if over-suppressed | Slower | Faster |
| Evidence | EXPLORER-HCM and subsequent data | SEQUOIA-HCM [3] |
How to take it
One capsule a day; the usual start is 5 mg, after which the dose is adjusted by echocardiography.
▸The effect develops gradually and is judged by exercise tolerance and gradient, not by an immediate sense of relief. ▸Stopping returns the baseline state — the drug manages the disease rather than curing its genetic cause.
Who should see a doctor first
▸This is not a general "heart medicine". The indication is narrow: symptomatic obstructive hypertrophic cardiomyopathy confirmed on echocardiography. ▸Echocardiography is part of the treatment, not a formality. The drug cannot be used without it.
Ejection fraction monitoring
Here benefit and principal risk are the same action at different doses. The drug reduces contractility: in the right measure that is treatment, in excess it is heart failure.
| Stage | What happens |
|---|---|
| Before starting | Echocardiography: ejection fraction, outflow tract gradient |
| Start | Usually 5 mg daily |
| Titration | Dose adjusted according to echocardiography and gradient |
| Maintenance | Echocardiography every 12 weeks |
| If ejection fraction falls below threshold | Treatment interrupted |
Interactions and limitations
▸Metabolism runs through CYP2C19 and CYP3A4 — combination with strong inhibitors or inducers requires dose adjustment or is prohibited; ▸pregnancy is a contraindication; women of childbearing potential need reliable contraception; ▸heart failure with reduced ejection fraction — the drug is not prescribed; ▸intercurrent illness (infection, tachyarrhythmia) can lower ejection fraction — therapy is reassessed at such times.
Bottom line
Mavacamten is the first drug to target the mechanics of excessive contraction, and regular echocardiography is what makes treatment safe.
The diagnosis and management can be discussed at a consultation; the product can be ordered here.
References
1. Olivotto I, et al. Mavacamten for treatment of symptomatic obstructive hypertrophic cardiomyopathy (EXPLORER-HCM): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet. 2020;396(10253):759–769. PMID 32871100
2. Olivotto I, et al. Mavacamten monotherapy in obstructive hypertrophic cardiomyopathy: an integrated analysis of phase 3 data. Am Heart J. 2026. PMID 42636950
3. Maron MS, et al. Aficamten for symptomatic obstructive hypertrophic cardiomyopathy (SEQUOIA-HCM). N Engl J Med. 2024;390(20):1849–1861. PMID 38739079
4. CAMZYOS (mavacamten) US Prescribing Information, Bristol Myers Squibb.
Caveats
▸Mavacamten or aficamten: no head-to-head trials exist — the cardiologist chooses according to the clinical situation, availability and convenience of monitoring.
This material is for information only and does not replace a consultation with a doctor.
Key facts
- Mavacamten (brand name Camzyos, Bristol Myers Squibb) is the first-in-class cardiac myosin inhibitor, approved by the FDA in April 2022 for symptomatic obstructive hypertrophic cardiomyopathy.
- Mechanism: it reduces the number of active cross-bridges between actin and myosin — the couplings that make muscle contract. The heart contracts less forcefully, relaxes better, and outflow tract obstruction eases.
- EXPLORER-HCM (Lancet, 2020): in this phase 3 trial the drug improved functional status and exercise capacity significantly more often than placebo in patients with the obstructive form.
- Doses are titrated, typically starting at 5 mg daily and adjusted according to echocardiography and the outflow tract gradient. The key risk is excessive suppression of contractility: ejection fraction is monitored by echocardiography on a schedule, and treatment is interrupted if it falls below threshold.
- Interactions matter: metabolism runs through CYP2C19 and CYP3A4, so combination with strong inhibitors or inducers requires dose revision or is prohibited. Pregnancy is a contraindication: the drug may harm the fetus, and women of childbearing potential require contraception.
