Study of Short‑and Long‑Term Hemodynamic and Physiological Effects of Mavacamten in Patients with Obstructive Hypertrophic Cardiomyopathy

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What is this study about?

The condition being studied is Obstructive Hypertrophic Cardiomyopathy, a disease where the heart muscle becomes unusually thick, making it harder for blood to leave the heart. The medication being tested is mavacamten, supplied as hard capsules taken by mouth. The drug works by reducing the excessive contraction of the thickened heart muscle, helping blood flow more normally.

The purpose of the study is to evaluate how the drug affects heart blood flow and tissue characteristics over short and long periods. Participants will receive the medication and undergo a series of heart scans using cardiovascular magnetic resonance (CMR) imaging, a type of MRI that creates detailed pictures of the heart. The scans will measure the myocardial perfusion reserve, which reflects the ability of heart muscle to receive blood, as well as other imaging markers such as tissue signals called T1, T2 and the amount of space outside cells called extracellular volume (ECV) mapping, and a technique called Late Gadolinium Enhancement (LGE) that shows scar tissue. Additional measurements will look at how much work the heart does each beat (stroke work), how efficiently it pumps (ventricular efficiency), its ability to contract (contractility), and the stiffness of the arteries (arterial elastance) using a pressure‑volume analysis (P‑V‑loop‑analysis). Blood flow patterns will also be examined with a technique called 4D flow‑analysis. The size of the heart muscle (myocardial mass) and the volume of the upper left chamber (left atrial volume) will be tracked.

The study will last several years, with participants returning for follow‑up scans at about three months, one year, and two years after starting treatment. Each visit will include the imaging procedures and safety checks, while the medication will be taken daily throughout the study period.

1 initial visit and baseline assessments

you attend the first study visit after joining the trial. during this visit, a series of baseline measurements are performed.

a cardiac magnetic resonance (cMR imaging) scan is done to obtain detailed pictures of the heart structure and function.

blood samples are collected to evaluate basic health parameters.

the information gathered serves as the reference point for all future comparisons.

2 start of study medication

you begin taking camzyos capsules, which contain the active substance mavacamten.

the prescribed dose is 15 mg taken by mouth once each day.

the medication is continued for the entire duration of the study, up to two years, unless a safety concern arises.

3 first follow‑up at 12 weeks

approximately twelve weeks after starting the medication, you return for a follow‑up visit.

another cMR imaging scan is performed to assess changes in heart blood flow, measured as myocardial perfusion reserve (mpr).

additional scans evaluate tissue characteristics such as t1, t2, and extracellular volume (ecv).

the same safety assessments and blood tests from the baseline visit are repeated.

4 annual follow‑up at 1 year

around one year after the start of treatment, you attend a yearly assessment visit.

a comprehensive cMR imaging study is repeated, including measurements of mpr, t1, t2, ecv, and the extent of late gadolinium enhancement (lge).

functional measurements such as stroke work, ventricular efficiency, and arterial elastance are obtained using pressure‑volume loop analysis.

4d flow analysis is used to evaluate kinetic energy and regional pressure gradients within the heart.

standard heart size and left atrial volume are also measured.

5 final follow‑up at 2 years

at the end of the two‑year study period, you complete the final visit.

the same set of cMR imaging and functional assessments performed at earlier visits are repeated to determine long‑term effects.

the study medication is discontinued after this final evaluation.

all collected data are used to compare changes from the baseline measurements.

Who Can Join the Study?

You have signed a written consent form agreeing to join the study.
You are 18 years old or older.
You have been diagnosed with obstructive hypertrophic cardiomyopathy (a heart condition where the muscle wall is unusually thick) that shows an unexplained thickening of the left ventricle (the main pumping chamber) of at least 15 mm, and the heart chambers are not enlarged and are not caused by other diseases such as high blood pressure or valve problems.
You are eligible to receive on‑label mavacamten therapy according to the official Swedish prescribing information (the approved use of the medicine in Sweden).
Your left ventricular outflow tract (LVOT) pressure is at least 50 mmHg when you are at rest, during a Valsalva maneuver (a simple breathing technique), or after exercise.
Your left ventricular ejection fraction (the percentage of blood pumped out of the left ventricle with each heartbeat) is 55 % or higher.
You have symptoms that are classified as New York Heart Association (NYHA) class II or III (meaning you have mild to moderate shortness of breath or fatigue with ordinary activity).
If you could become pregnant, you must not be pregnant or lactating, and if you are sexually active you must use effective birth control from the screening visit until 6 months after the last dose of mavacamten.

Who Cannot Join the Study?

Electronic cardiac devices such as an ICD (a device that can deliver a shock to the heart) or a pacemaker are not allowed, whether they are already placed or planned to be placed.
Reduced kidney function with an estimated GFR (a measure of how well the kidneys filter blood) less than 30 ml/min/1.73 m².
Severe liver problems classified as Child‑Pugh class C or liver enzyme levels (ALT or AST) that are three times higher than the normal laboratory range.
Inability to follow the study rules and visits.
Inability to undergo CMR exams (a special type of heart MRI scan).
Body mass index (BMI) of 40 kg/m² or higher (a measure of body weight relative to height).
Participation in another clinical trial with an experimental medicine within the last 30 days.
Having taken part in this same trial before.
Known or suspected allergy to any medication or product used in the study.
Being pregnant (positive pregnancy test), breastfeeding, or planning to become pregnant.
Mental, language, or willingness issues that make it hard to understand the study.
History of, or planned, septal reduction therapy (procedures such as surgical myectomy or percutaneous alcohol ablation to thin the heart muscle) during the study period.
Any treatment or disease that the doctor believes could affect the study results.
Having a heart‑muscle disease that looks like oHCM, such as Fabry disease, amyloidosis, or Noonan syndrome with thickened heart walls.
Having occasional (paroxysmal) or ongoing (permanent) atrial fibrillation (an irregular heart rhythm) seen on the screening ECG.
Current use (within 14 days before screening) or planned use of strong medicines that block or speed up the enzymes CYP3A4 or CYP2C19, such as certain antibiotics, anti‑seizure drugs, antifungal drugs, omeprazole, esomeprazole, St. John’s Wort, etc.
Having documented obstructive coronary artery disease (more than 70 % blockage in a heart artery) or a previous heart attack (myocardial infarction).
Having moderate or severe narrowing of the aortic valve (aortic valve stenosis) as judged by the doctor.
Having any acute or serious additional illness (for example, a major infection, blood disorder, kidney problem, hormonal imbalance, stomach disease, or endocrine issue) that could cause early withdrawal or interfere with study measurements.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Region Skane Skanes Universitetssjukhus	Lund	Sweden
Karolinska University Hospital	Solna	Sweden

Trial status

Country	Status	Recruitment Start
Sweden	Not yet recruiting	01.08.2026

Trial locations

Investigated drugs:

Mavacamten

CAMZYOS is an oral capsule that contains the active ingredient mavacamten. It works by gently lowering the strength of the heart’s muscle contractions, which can help reduce the blockage that occurs in obstructive hypertrophic cardiomyopathy. In this study, patients took CAMZYOS to see how it changes blood flow and heart function over short‑term and long‑term periods, using advanced heart imaging techniques to measure any effects.

Obstructive Hypertrophic Cardiomyopathy – This condition is a disease of the heart muscle in which the walls become unusually thick, especially the part that separates the two ventricles. The thickened muscle can narrow the pathway through which blood leaves the heart, creating an obstruction. As the obstruction worsens, the heart must pump with greater effort to move blood forward. Over time, the increased workload may lead to changes in the size and shape of the heart chambers. Symptoms often become more noticeable as the thickening and blockage progress.

Trial ID:

2025-524722-17-00

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of Short‑and Long‑Term Hemodynamic and Physiological Effects of Mavacamten in Patients with Obstructive Hypertrophic Cardiomyopathy

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?