Ambrisentan, the only endothelin-1 selective antagonist, was able to improve 6MWD in connective tissue disease (CTD)-associated PAH patients, even though survival was higher in idiopathic PAH patients, in the Ambrisentan in Pulmonary Arterial Hypertension, Randomized, Double-Blind, Placebo-Controlled, Multicenter, Efficacy Study (ARIES) 1 and 2 trials [56,57]. Here, EDN1 is linked to pulmonary arterial hypertension.