The FDA has approved Ambrisentan, or Letairis, an endothelin-receptor antagonist indicated for the once-daily treatment of pulmonary arterial hypertension (PAH), a rare, life-threatening condition characterized by continuous high blood pressure within the arteries of the lungs.

Use of the drug, manufactured by Gilead Sciences Inc, Foster City, Calif, has been shown to improve a patient’s ability to exercise and has delayed clinical worsening of PAH, according to the product’s labeling.

Because of the serious adverse teratogenic and hepatic events associated with the drug, Ambrisentan can be prescribed and obtained only through a restricted distribution program known as Letairis Education and Access Program, or LEAP. The drug is not recommended for use in patients with moderate or severe hepatic impairment.

The drug’s approval was based on the results of two short-term, randomized, double-blind, placebo-controlled trials involving 393 patients, according to Gilead. Patients receiving the drug could walk farther after 4 weeks of treatment than those in the placebo group, and a dose-response relationship became apparent after 12 weeks of treatment, the firm said.