Endothelins are a family of vasoactive peptides including ET-1, ET-2 and ET-3 in human. To date, two subtype of endothelin receptors have been identified from mammalian cells, EDNRA (ETA) and EDNRB (ETB). The EDNRA receptors (ETA) have a much greater affinity for ET-1 over ET-3 and are expressed abundantly in vascular smooth muscles and stromal tissues. The vasoconstrictor and proliferative effects of ET-1 are primarily mediated by the EDNRA receptor. This makes EDNRA a good target for drug development in a number of cardiovascular diseases, including congestive heart failure, hypertension, stroke, kidney failure, and a variety of non-cardiovascular conditions, such as asthma, chronic obstructive pulmonary disease, pain and cancer.