US Food and Drug Administration issues complete response letter regarding the Tracleer® supplemental New Drug Application - Completion and Approval of Risk Evaluation and Mitigation System (REMS) subm

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ALLSCHWIL/BASEL, SWITZERLAND - 02 March 2009 - Actelion Ltd (SIX:
ATLN) announced today it 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, M.D. and 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."
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Notes to the editor:

About Pulmonary Arterial Hypertension (PAH)
Pulmonary arterial hypertension (PAH) is a chronic, life-threatening
disorder characterized by abnormally high blood pressure in the
arteries between the heart and lungs of an affected individual. The
function of the heart and lungs is severely compromised, manifested
by a limited exercise capacity, and, ultimately, a reduced life
expectancy. Approximately 100,000 people in Europe and the United
States are afflicted with either primary or secondary forms of the
disease related to conditions or tissue disorders that affect the
lungs, such as scleroderma, lupus, HIV/AIDS or congenital heart
disease.
PAH is associated with structural changes in both the pulmonary
vasculature and the right ventricle. Recent advances [1] in the
understanding of the pathogenic factors leading to the pulmonary
vascular disease have led to the development of new therapies
targeting specific pathways (the prostacyclin pathway; the endothelin
pathway; and the nitric oxide pathway) [2]. The available therapies
have positive effects in PAH, but they do not provide a cure, and in
many patients the disease will progress. PAH remains a serious
life-threatening condition [2,3]. Early recognition and an
understanding of the selection and timing of therapeutic options
remain critical elements in the optimal management of patients with
this disorder.

About Tracleer® in Pulmonary Arterial Hypertension (PAH)
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.

Requires attention to two significant safety concerns: Potential for
serious liver injury (including rare cases of liver failure and
unexplained hepatic cirrhosis in a setting of close monitoring) -
Liver monitoring of all patients is essential prior to initiation of
treatment and monthly thereafter. Tracleer® treatment must not be
initiated in women of childbearing potential unless they practice
reliable contraception and participate in monthly pregnancy testing.
Due to these risks, Tracleer® is only supplied through a controlled
distribution.

References:

1. Farber HW; Loscalzo J. Mechanisms of disease: pulmonary
arterial hypertension. N. Eng. J. Med. 2004; 351:1655-65.
2. Humbert M; Sitbon O; Simonneau G. Treatment of pulmonary
arterial hypertension. N. Eng. J. Med. 2004;351:1425-36.
3. Humbert M; Morrell NW; Archer SL; et al. Cellular and
molecular pathobiology of pulmonary arterial hypertension. J. Am.
Coll. Cardiol. 2004; 43: Suppl. 12: 13S-24S.
4. Tracleer® SPC.

Actelion Ltd
Actelion Ltd is a biopharmaceutical company with its corporate
headquarters in Allschwil/Basel, Switzerland. Actelion's first drug
Tracleer®, an orally available dual endothelin receptor antagonist,
has been approved as a therapy for pulmonary arterial hypertension.
Actelion markets Tracleer® through its own subsidiaries in key
markets worldwide, including the United States (based in South San
Francisco), the European Union, Japan, Canada, Australia and
Switzerland. Actelion, founded in late 1997, is a leading player in
innovative science related to the endothelium - the single layer of
cells separating every blood vessel from the blood stream. Actelion's
over 1900 employees focus on the discovery, development and marketing
of innovative drugs for significant unmet medical needs. Actelion
shares are traded on the SIX Swiss Exchange (ticker symbol: ATLN) as
part of the Swiss blue-chip index SMI (Swiss Market Index SMI® )

For further information please contact:
Roland Haefeli
Vice President, Head of Investor Relations & Public Affairs
Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, CH-4123 Allschwil
+41 61 565 62 62
+1 650 624 69 36
http://www.actelion.com

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Actelion Pharmaceuticals Ltd
Gewerbestrasse 16 Allschwil
Switzerland

WKN: 936767; ISIN: CH0010532478; Index: SBIOM, SLIFE, SMCI, SMIEXP,
SMIM, SPI, SPIEX;
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