Gilead Says FDA Approves Drug To Treat PAH

Gilead Sciences Inc. (GILD) said the U.S. Food and Drug Administration late Friday approved its drug ambrisentan for the treatment of a lethal form of hypertension that strikes without warning and can kill within three years if untreated.

The drug, which will carry the U.S. trade name Letairis, is designed to treat a disease known as pulmonary arterial hypertension (PAH), in which arteries in the lungs constrict and thicken, raising blood pressure and eventually causing heart failure. Patients typically go to doctors complaining of exhaustion, breathlessness, and inability to walk distances or perform activities of normal daily living. Often no cause can be identified, although the condition also can be triggered by diseases like scleroderma or advanced HIV, or by certain medicines like the diet drug combo Fen-Phen.

Letairis belongs to a class of drugs called ERAs or endothelin receptor antagonists, compounds that relax the vessels, lowering blood pressure and lightening the load on the heart and lungs. However, such drugs can't be taken by pregnant women due to risk of major birth defects, and can cause liver damage.

In studies, the drug improved patients exercise capacity, as measured by a six-minute walking distance test. Gilead said it has priced the drug at $3,940 a month, comparable with other oral drugs for the disease. Gilead said it established a program to ensure greater access to patients who are underinsured or face high co-payment requirements.

Because of the risks of liver damage and birth defects, the drug's label will carry strong cautionary language in a black box, as do other drugs of its class. Gilead says its studies show that incidence of liver damage is less with Letairis than with other products in this class. The company said Letairis will be available only through a special restricted program to educate patients and doctors about safe usage.

Gilead acquired the drug as a result of its merger with the drug's developer Myogen Inc. in November 2006, and plans to make it the centerpiece of a third branch of its business in the cardio-pulmonary field. Gilead's core business has focused mainly on products for HIV and hepatitis.

Based on market research, Gilead said it estimates about 75,000 to 90,000 people in the U.S. suffer from PAH, and 200,000 people worldwide, although fewer than half of them are currently believed to be diagnosed. The condition is often misdiagnosed as exercise-induced asthma or other respiratory ailments.

Letairis will be marketed in the U.S. by Gilead, and by GlaxoSmithKline PLC (GSK) outside the U.S.