Clinical efficacy and safety of switch from bosentan to macitentan in children and young adults with pulmonary arterial hypertension: extended study results.

BACKGROUND: Macitentan is an orally active, potent, dual endothelin receptor antagonist and is the only registered treatment for pulmonary arterial hypertension that significantly reduced morbidity and mortality in a long-term study. AIM: We have recently reported that switch from bosentan to macitentan significantly improved exercise capacity in children and young adults with pulmonary arterial hypertension in a 24-week prospective study and well tolerated without adverse events. We now aimed to evaluate clinical efficacy, safety of switch in a larger patient population, in a 24-month prospective study. METHODS: This is a single-institution, 24-month prospective study. Patients >/=12 years with idiopathic/heritable, pulmonary arterial hypertension, or related to CHD or residual pulmonary arterial hypertension due to repaired congenital systemic-to-pulmonary shunts and on bosentan treatment were included. Concomitant treatment with oral phosphodiesterase type 5 inhibitors/inhaled prostanoids was allowed. Outcome measures included change from baseline to 24 months, in the 6-minute walk distance, functional class, oxygen saturation at rest/after walk distance test, and natriuretic peptide levels. Safety end points included adverse events, laboratory abnormalities. RESULTS: Twenty-seven patients (19 adults/8 children, mean age: 21.1 +/- 6.3 years (12-36), weight: 53.1 +/- 15.7 kgs (26-87)) were included. Mean duration of macitentan treatment: 22.3 +/- 3.9 months (9-24). Six-minute walk distance significantly improved from baseline (mean: 458 +/- 79 m (300-620)) at 6 months (mean: 501 +/- 73 m (325-616) + 43 m) (p 0.05). Macitentan did not significantly change functional class, oxygen saturation, and natriuretic levels (p > 0.05). None of the patients had anaemia, hepatotoxicity, and peripheral edema. CONCLUSIONS: Our study is the first study which showed that switch from bosentan to macitentan improved exercise capacity in children and young adults with pulmonary arterial hypertension significantly in the first 6 months and compared to baseline in 24 months and well tolerated without adverse events.