Shares in Swiss biotechnology group Actelion were given a hefty boost on news that its key R&D candidate, the antihypertensive drug macitentan, has delivered an excellent performance in a late-stage clinical trial and could be on the market by 2013.

Initial analysis of the data show that the SERAPHIN trial - in which 742 patients with pulmonary arterial hypertension (PAH) were treated with two different doses of the drug or a placebo for three years - has met its primary endpoint, giving Actelion a solid basis for a marketing application.

Unusually, the primary endpoints of the study were focused on outcome benefits, and the findings show that both doses of macitentan - a novel dual endothelin receptor antagonist - reduced the risk of a morbidity/mortality event versus placebo, while patients were being treated.

Compared to the control group, patients taking 3mg of macitentan experienced a 30% lower risk, while the risk was reduced even further - by 45% - in those taking 10mg over the treatment period.

"I truly believe that these results with macitentan will translate into clinical benefits for patients suffering from PAH," said Guy Braunstein, head of global clinical development at Actelion, adding that the company "will now rapidly analyze this largest ever clinical study in PAH in full detail, in view of regulatory filings later this year".

Tracleer successor?

Actelion and its investors will no doubt be breathing a huge sigh of relief given that patent protection on its flagship drug Tracleer (bosentan), which rakes in around 1.5 billion Swiss francs a year and represents the majority of its sales, is due to crumble from 2015, potentially shaving a huge chunk off of revenues. 

Tracleer's performance is already slipping as rival drug Gilead Sciences' Letairis (ambrisentan) eats into its market share, but according to some estimates around 50% of revenues could be lost when generics version enter the market. 

Analysts are predicting peak sales of up to 2.5 billion Swiss francs a year, so if approved macitentan could do more than just help cushion the blow, and represents a real life-line for the firm.

Actelion also said macitentan was found to be well-tolerated, with the rate of adverse events reported and treatment discontinuations similar across all treatment arms, and this could give it an important edge of Tracleer , which is associated with potential liver problems.

All eyes will now be on full results of the SERAPHIN trial, to be unveiled at upcoming scientific congresses and publications, and whether interest in mergers or acquisitions with the company will be ignited.