Endothelin receptors are a family of G protein-coupled receptors (GPCRs) comprised of two receptor types: ETA and ETB. These receptors are mainly located in blood vessels, and the activation of these receptors plays a key role in mediating vasodilation and vasoconstriction. While no ETA agonist has been found, both ET-1 and sarafotoxin S6c are selective ETB agonists. Selective ETA and ETB antagonists are used in the treatment of pulmonary arterial hypertension. There has also been development in the utility of endothelin receptor antagonists as an anti-cancer drug.