( First-Ever Placebo-controlled Study in...)Actelion Announces Positive Study with Bosentan (Tracleer) in,CTEPH,Health

First-Ever Placebo-controlled Study in Inoperable Chronic Thromboembolic Pulmonary Hypertension - Primary Endpoint of Reduction in Pulmonary Vascular Resistance Met - Six-Minute-walk Test Unchanged - Significant Effect on Dyspnoea Score and Biological Disease Marker

ALLSCHWIL, Switzerland, March 5, 2007 -Actelion Ltd (SWX: ATLN) announced today the initial results from the double-blind, placebo-controlled, multicenter study BENEFiT (Bosentan Effects in Inoperable Forms of Chronic Thromboembolic Pulmonary Hypertension). The study met its primary objective, as treatment with bosentan (Tracleer) was associated with a significant reduction in pulmonary vascular resistance PVR (p<0.0001). In this first-ever double-blind study in a patient population suffering from this form of pulmonary hypertension, the six-minute walk test remained stable over the four months of blinded evaluation in both treatment groups. Patients on bosentan showed a significant improvement in breathlessness (Borg dyspnoea score) with exercise and there was a trend in favor of bosentan towards prevention of worsening WHO functional class. Initial results also indicate that treatment with bosentan was associated with a significant decrease in NT-proBNP, an important biomarker of disease severity. In this study, Tracleer ®'s safety and tolerability profile was consistent with that observed in previous placebo-controlled clinical trials in pulmonary arterial hypertension (PAH).

Isaac Kobrin, MD and Head of Development at Actelion, commented: "With the BENEFiT study, Actelion has leveraged its leadership in pulmonary arterial hypertension to conduct the first randomized, placebo-controlled study in a specific form of pulmonary hypertension. For patients with inoperable CTEPH, there are currently no approved therapies available. Now, our dual endothelin receptor antagonist bosentan has shown in this patient population signi
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