Actelion says COMPASS-2 bosentan study fails primary endpoint

Europe’s largest biotech company Actelion (SIX: ATLN) has announced disappointing results of COMPASS-2, a Phase IV, prospective, randomized, double-blind, placebo-controlled, event-driven study evaluating the effect of bosentan (brand name Tracleer) on the time to first morbidity or mortality event in patients with symptomatic pulmonary arterial hypertension (PAH) already treated with sildenafil.

Sildenafil, the active ingredient of Pfizer’s (NYSE: PFE) blockbuster erectile dysfunction drug Viagra, is also approved and marketed by the pharma giant under the trade name Revatio for the treatment of PAH.

COMPASS-2 did not meet the primary endpoint of time to first morbidity or mortality event; bosentan showed a risk reduction of 17% versus placebo (p=0.25). In an exploratory analysis, bosentan on top of sildenafil showed an improvement of 21.8 meters in 6MWD at week 16 (p=0.01). The well characterized safety profile of bosentan was confirmed and a placebo-corrected incidence of 15.4% in liver enzyme elevations (aspartate aminotransferase (AST) or alanine aminotransferase (ALT)) greater than three times the upper limit of normal was observed over a median exposure to double-blind treatment of 23 months.