Ambrisentan: Pulmonary Arterial Hypertension Treatment

Ambrisentan was developed by Myogen before the company's acquisition by Gilead Sciences, Inc. for the treatment of pulmonary arterial hypertension (PAH). The drug acts like other PAH treatments: Tracleer and Thelin by blocking a endothelin in the blood (which the body uses to construct blood vessels) and is known as an Endothelin Receptor Antagonist (ERA). It is believed that these drugs block endothelin, resulting in less constriction of the blood vessels that narrow in PAH patients. Ambrisentan is in the midst of ongoing phase III clinical trials testing the safety and efficacy of the drug. Ambrisentan has already been granted orphan drug designation for the treatment of PAH in both the United States.

In February 2007, Gilead reported that the FDA granted a Priority Review for the company's New Drug Application for ambrisentan (5 mg and 10 mg) a once-daily treatment of pulmonary arterial hypertension (PAH). Priority Review status is given to drug products that, if approved, would represent a significant improvement compared to existing products in the treatment, diagnosis or prevention of a disease. This is a relatively hard standard to meet and the fact that it was granted is significant. Priority Review accelerates the FDA to review time to 6 months after a drug application. Gilead submitted its Application to the FDA for ambrisentan on December 18, 2006. Thus the FDA has established a target review date of June 18, 2007.

Ambrisentan: How it Works

As stated above, Ambrisentan is an endothelin receptor antagonist drug that works by blocking the action of endothelin, a very potent, naturally occurring vasoconstrictor that is capable of causing the narrowing of the blood vessels in the lungs. Researchers believe that endothelin is present in larger amounts in patients suffering from PAH. There are two types of naturally occurring endothelin receptors: ETA and ETB. When endothelin interacts or binds with ETA receptors, it causes the narrowing of the blood vessels (called vasoconstriction). When endothelin binds with ETB receptors, it produces nitric oxide and prostaglandin, relaxing and widening the blood vessels (vasodilation). The ETB receptors exist to counteract the ETA receptors and prevent against excessive narrowing of the blood vessels.

Ambrisentan is one of several newly developed drugs that specifically target the ETA receptors, the others being Tracleer and Thelin. Ambrisentan remains in the clinical trial process awaiting FDA approval, if approved will be a once-a-day oral medication taken in tablet form.

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Although Pulmonary Hypertension cannot be cured using existing medicine. It can be controlled with new drugs and therapies.

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