With no affinity for the prostaglandin E receptor 3 (EP3), selexipag exerts similar vasodilatory activity on both large and small pulmonary arterial branches [259] and its relaxant efficacy is not modified under conditions associated with PAH, whereas relaxation to treprostinil may be limited in the presence of mediators of disease such as ET-1 [260]. This evidence concerns the gene EDN1 and pulmonary arterial hypertension.