Actelion’s selexipag, the company’s third treatment for pulmonary arterial hypertension, has met its primary endpoint in a late-stage study.

The Swiss biotech major has presented top-line results from a Phase III study, the largest outcome trial ever conducted in PAH, involving 1,156 patients. The data shows that selexipag, the first selective oral prostacyclin IP receptor agonist, prolonged life by 39% versus placebo.

Actelion noted that the efficacy observed was “consistent across the key subgroups; age, gender, WHO functional class, PAH etiology and background PAH therapy”. Patients were treated for up to 4.3 years and tolerability was consistent with prostacyclin therapies, such as United Therapeutics’ oral treatment Orenitram (treprostinil), which was rather surprisingly approved by the US Food and Drug Administration in December.

Actelion chief executive Jean-Paul Clozel said he is “overwhelmed by the result of this long-term outcome study that evaluated selexipag in a setting where 80% of patients already received oral PAH therapy at baseline”. He added that together with partner Nippon Shinyaku, “we are now one step closer to bringing an effective oral therapy targeting the prostacyclin pathway to the PAH community”.

Dr Clozel added that “we will now work diligently to complete the analyses with the goal to initiate first regulatory filings with health authorities as soon as possible”. His enthusiasm was matched by Gérald Simonneau of the Université Paris-Sud, Le Kremlin-Bicêtre, France, who commented that “I have been prescribing intravenous prostacyclin therapies in PAH patients for almost twenty years”. He went on to note that “for the first time, with selexipag, we have an oral compound acting on the prostacyclin pathway showing a significant risk reduction on a highly clinically relevant endpoint”.

Getting approval for selexipag will cement Actelion’s dominant position in PAH. Last year, it received the green light on both sides of the Atlantic for Opsumit (macitentan), the follow-up to its hugely successful drug Tracleer (bosentan). Analysts predict it will be a blockbuster and offset declining sales of Tracleer which goes off-patent next year.

Investors are impressed and Actelion shares ended the day up 14.9% at 104.50 Swiss francs.