Even though pulmonary arterial hypertension (PAH) remains an incurable disease, the combination of PAH-specific therapies allowed treatment strategies to evolve from symptom-based ones to others that aim to move patients to low-risk conditions. Endothelin-1 (ET-1) receptor antagonists emerged as specific-PAH drugs that can be used in combination with other specific therapies. This work aimed to perform a prospective clinical assessment of patients with PAH that switched from bosentan to macitentan (POTENT), due to inadequate response.POTENT is a prospective, open-label, single-arm, uncontrolled study including PAH patients from our ongoing SAUDIPH registry. It enrolled 50 PAH patients divided as follows: idiopathic/heritable pulmonary arterial hypertension (I/HPAH); n = 24; PAH associated with congenital heart disease, n = 19; PAH associated with connective tissue diseases, n = 5; and pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis (PVOD/ PCH), n = 2. At baseline, most patients were in World Health Organization Functional Class (WHO FC) II/III (52.0%). After switching to macitentan, patients were more likely to be in WHO FC I/II (78%) and 22% of the overall cohort moved to a lower risk condition, with three low risk stratification parameters. Mean 6-min walking distance increased about 34 m after