Aprocitentan (ACT-132577) is the major and pharmacologically active metabolite of Macitentan. Aprocitentan is an orally active dual ETA/ETB antagonist with IC50s of 3.4 nM and 987 nM, and pA2 valus of 6.7 and 5.5, respectively. Aprocitentan is an antihypertensive agent[1].