BioWorld International Correspondent

Actelion Ltd.'s dependency on its Tracleer (bosentan) franchise deepened with news on Monday that its urotensin-II receptor antagonist palurosan failed to demonstrate efficacy in a Phase IIa trial in diabetic nephropathy.

The Allschwil, Switzerland-based company said the preliminary efficacy data it obtained did not warrant the initiation of a full-fledged clinical development program. It said that it now plans to analyze the full data generated in three studies that involved close to 100 patients. Palurosan was the first urotensin-II receptor antagonist to undergo clinical trials. Actelion said that it may reinitiate development, should additional understanding of the role of urotensin-II, a vasoconstrictive peptide that is elevated in cardiac, renal and liver disease, emerge.

"Definitely the pipeline looks thinner now with palurosan gone," said Birgit Kulhoff, analyst at Bank Sal. Oppenheim in Zurich, Switzerland. However, the effect on the stock was minimal, as the project was still early stage, and Kulhoff said "the valuation attached to that was really pretty small."

Moreover, by Tuesday, the share price clawed back whatever ground it had conceded, on positive news of its flagship product, Tracleer (bosentan), which demonstrated long-term safety in a post-marketing surveillance study of almost 5,000 patients with pulmonary arterial hypertension, and from other news emerging from the American Thoracic Society meeting in San Diego.

Kulhoff said that Pfizer Inc., of New York, failed to demonstrate a decrease in clinical worsening with its forthcoming rival drug Revatio (sildenafil citrate), which is expected to gain approval this year. "Therefore Tracleer will remain the gold standard in Class III and IV pulmonary arterial hypertension patients," Kulhoff said.

The stock closed at CHF125.90 Tuesday, up CHF3 from Monday's close.

In a research note published Monday, analysts Mike Booth and Karl Keegan at Canaccord Capital's London office said that both Revatio and Thelin (sitaxsentan), which Houston-based Encysive Pharmaceuticals Inc. is developing, will offer competition to Tracleer. While neither product is likely to lead to a decrease in its sales, each could slow future growth.

For Actelion, line extensions to Tracleer in digital ulceration and in idiopathic pulmonary fibrosis offer the most immediate potential for additional growth, Kulhoff said. "For the time being, they should use their resources to speed up all the clinical trials ongoing with Tracleer."