* Developing drug to treat chronic plaque psoriasis
* 46 pct of patients saw 75 pct improvement at week 16
* Plan to proceed to late-stage trials
* Shares rise 1.2 pct (Adds shares, analyst comment)
By Caroline Copley
ZURICH, Dec 18 Actelion, Europe's biggest biotech company, reported positive results from a mid-stage clinical trial of a treatment for skin disease psoriasis, adding to recent good news for its key next-generation heart and lung drug.
The Swiss firm said on Tuesday its ponesimod drug achieved its main goal in the trial, with 46 percent of patients suffering from moderate to severe chronic plaque psoriasis seeing a 75 percent improvement in an index for monitoring the disease at 16 weeks when treated with a 20 milligramme dose.
This compares with a 13.4 percent improvement in patients treated with a placebo. Patients receiving ponesimod continued to show improvement after the initial 16 weeks, Actelion added.
The results are a further boost to Actelion, which is currently dependent on heart and lung drug Tracleer but has seen its future brighten since macitentan - a next-generation replacement for Tracleer - beat expectations in a trial.
Its shares were up 1.2 percent to 45.54 Swiss francs by 0925 GMT, outperforming a 0.2 percent fall in the European healthcare index.
Vontobel analyst Andrew Weiss noted there was stiff competition in the psoriasis field from Amgen's brodalumab, which showed a greater improvement in a mid-stage study published earlier this year.
"We regard Amgen's brodalumab as (a) superior compound in the global psoriasis pipeline," Weiss said. "However, a strength of Actelion's compound is the oral route of administration." Brodalumab is injected.
Psoriasis is a chronic, inflammatory skin disease which affects about 1-3 percent of the world population, with plaque psoriasis the most common form, making up 85 percent of cases.
Actelion said it now planned to start late-stage trials for ponesimod - which is also being developed as a treatment for multiple sclerosis - once the data has been fully analysed.
The company is banking on macitentan to replace Tracleer, which goes off patent in 2015 and is already facing competition from U.S. rival Gilead's Letairis.
"The main investment case remains based on Actelion's two drugs for the treatment of high lung blood pressure, but the additional diversification that ponesimod in psoriasis could provide would be welcome," said Sarasin analyst David Kaegi.
Last week, Actelion said the U.S. health regulator had agreed to evaluate macitentan - also called Opsumit - for the treatment of patients with a potentially life-threatening lung condition. (Reporting by Caroline Copley; Editing by Mark Potter and Emma Thomasson)