Bosentan for chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a severe and underdiagnosed disease characterized by progressive hypertension secondary to organized thrombi in pulmonary vessels. The arteriolar lesions of CTEPH are similar to those seen in idiopathic pulmonary arterial hypertension (PAH). Surgical disobliteration of the vessels by pulmonary endarterectomy is the therapy of choice but this is not suitable for all cases. To date, there is no licensed specific drug for CTEPH. Endothelin-1, a vasoconstrictor and promoter of cell proliferation, is involved in the pathogenesis of both CTEPH and PAH. Bosentan, the first oral dual endothelin receptor antagonist, has been shown to be effective in PAH. Preliminary uncontrolled and/or unblinded studies reported efficacy of bosentan in CTEPH, and the only randomized, controlled trials showed a positive hemodynamic effect but failed its other co-primary end point, namely the improvement of 6-min walking distance. Nevertheless, bosentan has been shown to be sa...