Actelion Ltd has received a complete response letter from the US Food and Drug Administration (FDA) regarding the supplemental New Drug Application (NDA) the company filed in August 2007.

In this supplemental NDA, Actelion asked that the US product indication be expanded to include patients suffering from Pulmonary Arterial Hypertension (WHO Group I) with less severe disease (WHO Class II - IV symptoms). Since November 2001, Tracleer has been commercially available in the United States for PAH patients with WHO III-IV symptoms.

In its complete response letter, the FDA has informed Actelion that the REMS submission (Risk Evaluation and Mitigation Strategy) Actelion submitted in September 2008 needs to be finalized and approved before the FDA will then, in turn, be able to conclude the review of the supplemental Tracleer NDA expanding the indication to the less severe PAH patient population.

Jean-Paul Clozel, chief executive officer of Actelion, commented, "We will continue to diligently work with the US Food and Drug Administration on the ongoing REMS submission in order to expand the US product label to include less severe PAH patients."

Tracleer (bosentan), the first oral dual endothelin receptor antagonist, is approved for the treatment of pulmonary arterial hypertension (PAH) and made available by Actelion subsidiaries in the United States, the European Union, Japan, Australia, Canada, Switzerland and other markets worldwide.