Step Forward in Treating Pulmonary Arterial Hypertension

FDA approved after seeing side effects in fewer patients

pretend capsule with hearts inside capsule

A new drug for treating Group 1 pulmonary hypertension (also called pulmonary arterial hypertension) is being hailed as an improvement over earlier medications because it has been found to cause side effects in fewer patients, and it only needs to be taken once a day.

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Swiss pharmaceutical company Actelion recently received FDA approval for the drug, macitentan (Opsumit®).

The drug was approved at a 10-mg dose, which was tested in a multi-center clinical study over a 36-month period, which is published in the New England Journal of Medicine.

 A step forward

“Macitentan is a notable improvement on old solutions, says Raed Dweik, MD, Director of the Pulmonary Vascular Program at Cleveland Clinic.

“The new drug is similar to two other available medications (bosentan and ambrisentan) but it only needs to be taken once a day. It also does not cause a common side effect of other drugs: leg swelling and risk of liver damage in some patients,” Dr. Dweik says.

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A drug that does not cause the legs to swell is significant because this side effect is already a symptom of pulmonary hypertension. “Not only does additional swelling increase discomfort for patients, but it also makes it hard for physicians to determine the cause of the swelling,” Dr. Dweik says.

How this drug works

Macitentan blocks the negative effects of endothelin, a powerful substance in the body that constricts blood vessels and increases blood pressure.

Even though it’s natural for the human body to produce endothelin, it can produce too much in response to inflammation, high blood pressure or high cholesterol.

In people with Group 1 pulmonary hypertension, constricted blood vessels due to overproduction of endothelin is especially serious. While rare, the disorder causes narrowing of the arteries that carry blood to the heart – making it difficult for blood to flow through the vessels.

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The disorder may be inherited or may be caused by drugs or toxins. It also may be caused by conditions such as HIV infection, liver disease or sickle cell disease or by conditions that affect the veins and small blood vessels of the lungs.   

Macitentan is now the third medication (after bosentan and ambrisentan) that is FDA-approved to treat Group 1 pulmonary hypertension through the endothelin pathway.

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