Phase 3 Study Update of Opsumit for Pulmonary Arterial Hypertension

Actelion announced results from the SERAPHIN Phase 3 long-term outcome study of macitentan (Opsumit) in patients with pulmonary arterial hypertension (PAH).

In this double-blind, placebo-controlled trial, 742 patients suffering from PAH were randomized to placebo, macitentan 3mg or macitentan 10mg. When entering the study, 64% of patients were already receiving therapy for PAH, almost exclusively in the form of phosphodiesterase-5 inhibitors. At baseline, 53% of patients were in WHO Functional Class I/II, 47% were in Functional Class III/IV.

In the study, macitentan administered once daily provided a significant and clinically relevant reduction in the risk of morbidity and mortality. SERAPHIN met its primary endpoint by demonstrating that macitentan 10mg  once daily reduced the risk of morbidity and mortality by 45% vs. placebo (P<0.0001), providing a strong and sustained benefit to patients suffering from PAH. Macitentan 3mg once daily reduced the risk of morbidity and mortality by 30% (P=0.0108).

The study also demonstrated that macitentan reduces the risk of death due to PAH or hospitalization for PAH, one of the secondary endpoints of the study, by 33% (3mg, P=0.0146) and 50% (10mg, P<0.0001) vs. placebo. In addition, the evaluation of survival, while not statistically significant, showed that macitentan 10mg reduced the risk of all-cause mortality by 36%  (P=0.2037).

Patients treated with macitentan 10mg once a day also experienced a clinically relevant functional improvement, as shown by the baseline adjusted, placebo corrected mean increase in 6-minute walking distance measured at Month 6 (secondary endpoint) by 23 meters (P=0.007) with a more pronounced treatment effect in patients in WHO Functional Class III/IV at baseline (+37 meters; P=0.009).

Macitentan is a novel dual endothelin receptor antagonist (ERA).

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