Ambrisentan (U.S. trade name Letairis; E.U. trade name Volibris; India trade name Pulmonext by MSN labs) is a drug indicated for use in the treatment of pulmonary hypertension.
The peptide endothelin constricts muscles in blood vessels, increasing blood pressure. Ambrisentan, which relaxes those muscles, is an endothelin receptor antagonist, and is selective for the type A endothelin receptor (ETA). Ambrisentan significantly improved exercise capacity (6-minute walk distance) compared with placebo in two double-blind, multicenter trials (ARIES-1 and ARIES-2).
Ambrisentan was approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency, and designated an orphan drug, for the treatment of pulmonary hypertension.