Randomized study of adding inhaled iloprost to existing bosentan in pulmonary arterial hypertension

Rationale: Small, open-label studies suggest that combinations of existing therapies may be effective for pulmonary arterial hypertension (PAH). Objective: To evaluate the safety and efficacy of adding inhaled iloprost, a prostacyclin analog, to the endothelin receptor antagonist bosentan in patients with PAH. Methods: In a randomized, multicenter, double-blind trial, inhaled iloprost (5 μg) or placebo was added to stable monotherapy with bosentan for 12 wk. Efficacy endpoints included change from baseline in 6-min-walk distance (6-MWD), modified New York Heart Association (NYHA) functional class, hemodynamic parameters, and time to clinical worsening. Measurements and Main Results: A total of 67 patients with PAH (55% idiopathic PAH, 45% associated PAH, 94% NYHA class III, and mean baseline 6-MWD of 335 m) were randomized. At Week 12, patients receiving iloprost had a mean increase in 6-MWD of 30 m (p = 0.001); placebo patients had a mean 6-MWD increase of 4 m (p = 0.69), with a placebo-adjusted difference of +26 m (p = 0.051). NYHA status improved by one class in 34% of iloprost versus 6% of placebo patients (p = 0.002). Iloprost delayed the time to clinical worsening (p = 0.0219). Improvements were noted in postinhalation placebo-adjusted change in mean pulmonary artery pressure (-8 mm Hg; p < 0.001) and pulmonary vascular resistance (-254 dyn·s· cm^-5; p < 0.001). Combination therapy was well tolerated. Conclusions: Within the limitations of a relatively small sample size, results of this study demonstrate that the addition of inhaled iloprost in patients with PAH with reduced exercise capacity on bosentan monotherapy is safe and efficacious.