ERAs bind to either one or both ETA/ETB receptors on smooth muscle cells (SMC) or endothelial cells and reduce the vasoconstriction associated with ET-1.29, –31 ERAs improve the prognosis of World Health Organization (WHO) functional class II and III PAH patients32 and ETA-selective or dual ETA/ETB antagonism were shown to increase endothelial function and improve forearm33,34 and coronary artery35 blood flow in patients with atherosclerosis. The gene discussed is EDN1; the disease is pulmonary arterial hypertension.