Actelion drug flunks PhII but safety data bolsters confidence in blockbuster PhIII

Typically, when a drug fails a mid-stage study and the biotech announces it will shelve the program as a result, it's counted as a black mark. But there isn't anything typical about Actelion's development program for macitentan.

Billed as the crucial successor to Tracleer by the Swiss company ($ATLN), investigators zeroed in on data demonstrating that the drug had proved safe at the higher dose, with no signs of a spike in liver enzymes. And while the experimental drug failed to hit the primary endpoint for idiopathic pulmonary fibrosis, the study helped build confidence that macitentan can clear safety hurdles on pulmonary arterial hypertension, which is the key market. Tracleer earned more than $1.5 billion last year.

"The first indication that macitentan is safe at the highest investigated dose (10mg) is comforting and should restore some confidence in the pipeline in Actelion," noted Vontobel analyst Andrew Weiss. Investors agreed, sending shares of Actelion up about 3%.

Patients in the study were treated with macitentan for anywhere from 14 months to 24 months, providing researchers with a look at the effects of lengthy exposure.

"I am very encouraged to observe that, in this patient population, macitentan displays an excellent safety and tolerability profile, particularly in terms of liver enzyme elevations that are no different from placebo," says CEO Jean-Paul Clozel. "The 10 mg dose of macitentan is the higher of two doses under evaluation in our ongoing Phase III SERAPHIN study in pulmonary arterial hypertension. I expect this event-driven morbidity / mortality study with over 740 patients to report in the first half of 2012."

- see the Actelion release
- read the story from the Irish Times