Longer-term bosentan therapy improves functional capacity in Eisenmenger syndrome: Results of the BREATHE-5 open-label extension study

Abstract 

Background

Bosentan, an oral endothelin ET_A/ET_B receptor antagonist, improves hemodynamics and exercise capacity in patients with Eisenmenger syndrome but longer-term effects are unknown. This study investigated the efficacy and safety of bosentan up to 40 weeks in these patients.

Methods

Following the 16-week, double blind, placebo-controlled BREATHE-5 study of bosentan in patients with Eisenmenger syndrome, an open-label extension (OLE) was performed. Patients who completed BREATHE-5 received bosentan for an additional 24 weeks (62.5 mg b.i.d. for 4 weeks, then 125 mg b.i.d.) and were analyzed in two groups; ex-placebo and ex-bosentan, according to BREATHE-5 treatment.

Results

Thirty-seven patients with Eisenmenger syndrome who participated in BREATHE-5 were included in the OLE. At week 24, the 6-minute walk distance (mean±SE) increased from OLE baseline for the ex-placebo (+33.2±23.9 m) and ex-bosentan group (+6.7±10.0 m). The overall improvement from baseline of BREATHE-5 was +61.3±8.1 m (95% confidence interval: [44.7, 78.0]) for the ex-bosentan group. WHO functional class was improved in both groups. Bosentan did not reduce systemic arterial blood oxygen saturation; safety profile was comparable to previous trials.

Conclusions

In conclusion, these longer follow-up data support the efficacy and safety profile reported in the preceding BREATHE-5 study of bosentan treatment of Eisenmenger syndrome, challenging the notion that pulmonary vascular disease and severe functional impairment in these patients are not amenable to therapy.

Keywords: Bosentan, Endothelin receptor antagonism, Pulmonary arterial hypertension, Eisenmenger syndrome