The FDA has approved Tracleer (bosentan tablets, from Actelion), a dual endothelin receptor antagonist, for the treatment of patients with mildly symptomatic World Health Organization (WHO) Functional Class II pulmonary arterial hypertension (PAH). This approval is based on results from the clinical trial EARLY, a randomized, double-blind, placebo-controlled study. The primary endpoints for the EARLY trial were changes in pulmonary vascular resistance (PVR) and exercise capacity as measured by a six minute walk test (6-MWD). Disease progression was assessed by the secondary endpoints, which included time to clinical worsening and WHO Functional Class. A reduction of 22.6% in PVR (p<0.0001) and a 77% risk reduction in clinical worsening (p=0.011) were seen after 24 weeks of Tracleer treatment compared with placebo. Time to clinical worsening, defined by death, hospitalization for PAH and symptomatic progression of PAH, showed more patients treated with Tracleer remained stable without signs of deterioration compared with placebo (3.4% versus 13.2%, p=0.029). Improvement in 6-MWD did not reach statistical significance (p=0.076), this may reflect the fact that, on average, enrolled patients had a relatively well preserved exercise capacity at baseline, which can be more difficult to improve.
Tracleer is already approved for the treatment of PAH (WHO Group I) in patients with WHO Functional Class III or IV symptoms, to improve exercise ability and decrease the rate of clinical worsening.
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