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New Hope for a Rare Heart Condition

By Steven Reinberg HealthDay Reporter

THURSDAY, Nov. 12, 2020 (HealthDay News) -- An experimental drug might improve heart function for people with a condition called obstructive hypertrophic cardiomyopathy, a new study finds.

Hypertrophic cardiomyopathy is a thickening of heart muscle that can obstruct blood flow. The new drug, mavacamten, improves heart structure, reduces stiffness of the heart muscle and restores normal mitral valve motion, researchers said. The mitral valve separates the two chambers of the left side of the heart.

"The use of mavacamten as a disease-specific therapy would be a significant advance in therapy for this population," said lead researcher Dr. Sheila Hegde, a cardiovascular medicine specialist at Brigham and Women's Hospital in Boston.

But "it has not been approved yet, nor has it been compared to other treatments in a clinical study," she noted.

Currently, the treatment for obstructive hypertrophic cardiomyopathy relies on relieving symptoms. In this phase 3 trial, mavacamten not only relieved symptoms, but helped improve the underlying causes of the condition.

"Mavacamten is a first-in-class medication [myosin inhibitor] designed to target the heart muscle proteins that drive increased contractility in the heart, one of the hallmarks of patients with symptomatic hypertrophic cardiomyopathy," Hegde said.

The trial was paid for by California-based MyoKardia Inc., the maker of mavacamten.

About 1 in 500 people suffer from hypertrophic cardiomyopathy, which is caused by genes in heart muscle that cause the walls of the left ventricle (left lower chamber) to contract harder and thicken more than normal.

Specifically, the wall between the chambers of the heart thicken, and the walls of the chamber that pumps blood become stiff.

This thickening and stiffening can block or reduce the flow of blood from the left ventricle of the heart to the aorta, which sends blood throughout the body.

Treatments for hypertrophic cardiomyopathy focus on relieving chest pain and shortness of breath (especially with physical exertion), fatigue, abnormal heart rhythms, dizziness, fainting and swelling in the ankles, feet, legs, abdomen and veins in the neck.

This latest trial pitted mavacamten against a placebo in 244 patients, average age 58.

After 30 weeks, those taking the drug had significant improvement in blood flow through the heart, exercise capacity and symptoms.

"Since mavacamten has only been studied in patients in the phase 3 study for 30 weeks, there is an ongoing long-term extension study to help provide further details on the long-term impact on heart structure and function," Hegde said.

The findings were scheduled to be presented Nov. 13-17 at the American Heart Association's virtual annual meeting.

Dr. Gregg Fonarow, interim chief of the division of cardiology at the University of California, Los Angeles, said that hypertrophic cardiomyopathy results in substantial morbidity and is challenging to manage.

"Despite currently available medications, many patients have functional limitations and disabling symptoms," said Fonarow, who wasn't involved with the study. "This therapy appears to represent an important advance in treatment for patients with hypertrophic cardiomyopathy and could fill a very important unmet need."

Research presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.

More information

For more on hypertrophic cardiomyopathy, see the American Heart Association.

SOURCES: Sheila Hegde, M.D., M.P.H., cardiovascular medicine specialist, Brigham and Women's Hospital, Boston; Gregg Fonarow, M.D., interim chief, Division of Cardiology, University of California, Los Angeles; presentation, American Heart Association's virtual annual meeting, Nov. 13-17, 2020

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