Gilead Sciences Inc. announced that the US Food and Drug Administration (FDA) has accepted for filing and granted a priority review for the company's New Drug Application (NDA) for marketing approval of ambrisentan (5 mg and 10 mg) for the once-daily treatment of pulmonary arterial hypertension (PAH).

Priority review status is assigned to drug products that, if approved, would be a significant improvement compared to marketed products in the treatment, diagnosis or prevention of a disease. A Priority review means that the time it takes FDA to review a new drug application is reduced.

The FDA goal for reviewing a drug with Priority review is six months. Gilead submitted its NDA for ambrisentan on December 18, 2006. The FDA has established a target review date, under the Prescription Drug User Fee Act (PDUFA), of June 18, 2007.

Ambrisentan is a non-sulfonamide, propanoic acid-class, endothelin receptor antagonist that is selective for the endothelin type-A (ETA) receptor. Activation of the ETA receptor by endothelin, a small peptide hormone, leads to vasoconstriction and cell proliferation.

PAH is associated with elevated endothelin blood levels. Ambrisentan has been granted orphan drug designation for the treatment of PAH in both the United States and European Union.

PAH is a debilitating disease characterized by constriction of the blood vessels in the lungs leading to high pulmonary arterial pressures. These high pressures make it difficult for the heart to pump blood through the lungs to be oxygenated. Patients with PAH suffer from shortness of breath as the heart struggles to pump against these high pressures causing such patients to ultimately die of heart failure.