Actelion has submitted Opsumit, its new treatment for pulmonary arterial hypertension, with regulators in Europe.

The European Medicines Agency has accepted the file for Opsumit (macitentan) a novel oral dual endothelin receptor antagonist, on the basis of data from a 742-patient Phase III trial. In the study, called SERAPHIN, the risk of a morbidity and mortality event was reduced by 45% for patients in the Opsumit 10mg dose group and by 30% for those on the 3mg dose compared to those on placebo.

Patients were treated for up to three and a half years, providing safety data which showed that the drug was well tolerated; the most common adverse events were nasopharyngitis, headache and anaemia.

The European filing comes a month after a submission to the US Food and Drug Administration. Actelion chief executive Jean-Paul Clozel said that "we have worked hard to prepare the dossiers for a timely submission" and the firm will continue to work on filings in Switzerland and other major markets.

Opsumit is seen as the successor to Actelion's flagship drug Tracleer (bosentan). The latter makes up the vast majority of the Switzerland-based drugmaker's turnover and first-half 2012 sales came in at 752.4 million Swiss francs.

However this represented a 4% decline as Tracleer, which goes off-patent from 2015 and is already struggling to hold market share against Gilead Sciences' rival drug Letairis (ambrisentan).