Tracleer receives label extension in the US for the treatment of patients with mildly symptomatic WHO Functional Class II pulmon

ALLSCHWIL, SWITZERLAND - 10 August 2009 - Actelion Ltd (SIX: ATLN)
announced today that the U.S. Food and Drug Administration (FDA) has
approved the company's supplemental New Drug Application (sNDA) for
Tracleer(R) (bosentan) to treat patients with mildly symptomatic WHO
Functional Class II (FC II) pulmonary arterial hypertension (PAH).
The U.S. FDA has also approved Actelion's Risk Evaluation and
Mitigation Strategy (REMS) for Tracleer(R).

Jean-Paul Clozel, M.D. and Chief Executive Officer of Actelion
commented: "Physicians in the United States of America who treat PAH
patients now have access to Tracleer(R) as an approved therapy for
patients not only in advanced, but also in the early stages of this
rapidly progressing and life-threatening disease. This label
extension is based on EARLY, the only randomized, double blind,
placebo controlled study in this mildly symptomatic patient
population. The EARLY results demonstrate that Tracleer(R)
significantly reduces risk of clinical worsening in early-stage
patients, thereby slowing down disease progression."

Vallerie McLaughlin, MD, Associate Professor of Medicine, Director,
Pulmonary Hypertension Program, University of Michigan Health System
added: "PAH is a progressive and devastating disease, and patients
are not always treated as early as they should be with therapies that
can impact disease progression. The approval of Tracleer(R) for the
treatment of patients with early-stage disease, offers physicians a
new, proven therapy that may result in beneficial clinical outcomes."

Kirk Taylor, M.D., Senior Vice President, U.S. Medical Group at
Actelion Pharmaceuticals US, Inc. commented: "The FDA's approval of
Tracleer(R) for use in patients with early-stage PAH provides the
opportunity to improve clinical outcomes. Tracleer(R) is the only PAH
medication that has consistently shown significantly reduced risk of
clinical worsening in PAH patients in three separate Phase III
studies."

Tracleer(R) is an oral dual endothelin receptor antagonist approved for
the treatment of PAH FC II, III and IV in the US [1] and for the
treatment of PAH FC II and III in the EU. [2] The company is working
with authorities on a worldwide basis to expand the label for
Tracleer(R) to include patients with FC II PAH.

Survey highlights benefits of treating patients with early treatment
Results from a 2008 Harris Interactive survey [3] showed that more
than 90 percent of US physicians who treat pulmonary arterial
hypertension (PAH) patients believe that the disease is often
diagnosed and treated later than it should be.

More than three quarters of physicians understand the clinical
benefits of treating early, and agree that goals of treatment include
delayed time to clinical worsening and improvement across relevant
hemodynamic parameters (pulmonary arterial pressure, pulmonary
vascular resistance, cardiac resistance and mean right arterial
pressure). However, just over half of these physicians were
prescribing endothelin receptor antagonists (ERAs) at the time of the
survey.

After reviewing the data from the Phase III EARLY study, more than 90
percent of physicians polled in the survey agreed that they would be
likely to prescribe Tracleer(R) alone or in combination therapy for FC
II PAH patients.

The survey polled more than 300 US pulmonologists, cardiologists and
rheumatologists who have treated more than five PAH patients in the
previous 12 months. Additional data garnered from the survey is as
follows:

* 94 percent of physicians agree that PAH is diagnosed later than
it should be
* 92 percent of physicians believe PAH is treated later than it
should be
* 81 percent of physicians agree that early diagnosis and treatment
of PAH would provide numerous positive clinical outcomes in this
patient population
* 51 percent of physicians currently prescribe pharmacologic
treatment for early stage FC II patients
* 66 percent of physicians would consider prescribing ERAs to FC
I/II patients

About the pivotal Phase III EARLY study
The objectives of the prospective, randomized, placebo-controlled,
multicenter EARLY (Endothelin Antagonist tRial in miLdlY symptomatic
PAH patients) trial were to gain more insights into early stage
disease and to investigate the effects of bosentan specifically in
patients with WHO FC II PAH.

The results from EARLY - published in "The Lancet" in June, 2008 [4]
- reinforce the relentlessly progressive nature of PAH even in its
early stages. This was evident from the placebo group deterioration
reflected in the rate of clinical worsening events. The primary
endpoints for the EARLY trial were changes in pulmonary vascular
resistance (PVR) and exercise capacity as measured by a six minute
walk test (6-MWD). Disease progression was assessed by the secondary
endpoints, which included time to clinical worsening and WHO
Functional Class.

A highly significant reduction of 22.6% in PVR (p <0.0001) and a
significant 77% risk reduction in clinical worsening (p = 0.011) were
seen after 24 weeks of bosentan treatment compared with placebo. Time
to clinical worsening, defined by death, hospitalization for PAH and
symptomatic progression of PAH, showed that more patients remained
stable without signs of deterioration in the bosentan-treated group
compared with placebo (3.4% vs. 13.2%, p = 0.029). In addition, a
significant delay in WHO functional class deterioration was observed
in the bosentan group compared with placebo, providing further
evidence of delayed disease progression.

Although the improvement in 6-MWD did not reach statistical
significance (p = 0.076) this may reflect the fact that, on average,
enrolled patients had a relatively well preserved exercise capacity
at baseline, which can be more difficult to improve. A subgroup of
patients who received concomitant sildenafil showed improvements in
the bosentan treatment group consistent with the overall results. The
safety and tolerability profile of bosentan was consistent with that
observed in previous placebo-controlled clinical trials.

###

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 [5] 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) [6]. The available therapies
have shown positive treatment effects in patients with PAH, but they
do not provide a cure, and in many patients the disease will
progress. PAH remains a serious life-threatening condition [6,7].
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(R) in Pulmonary Arterial Hypertension (PAH)
Tracleer(R) (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 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. High potential for major birth
defects -Pregnancy must be excluded and prevented by two forms of
birth control; monthly pregnancy tests should be obtained. Tracleer(R)
is contraindicated for use with cyclosporine A and glyburide. Due to
these risks, in the US, Tracleer(R) is only supplied through a
controlled distribution.

References
1. Tracleer(R) Prescribing Information
2. Tracleer(R) Summary of Product Characteristics
3. Online survey conducted by Harris Interactive, May 16-22,
2008, among 303 U.S. pulmonologists, cardiologists and
rheumatologists who treated at least 5 PAH patients in the previous
12 months. Survey was commissioned by Actelion.
4. Galie N, Rubin LJ, Hoeper MM, et al. Treatment of patients
with mildly symptomatic pulmonary arterial hypertension with bosentan
(EARLY study): a double-blind, randomised controlled trial. Lancet
2008;371:2093-100.
5. Farber HW; Loscalzo J. Mechanisms of disease: pulmonary
arterial hypertension. N. Eng. J. Med. 2004; 351:1655-65.
6. Humbert M; Sitbon O; Simonneau G. Treatment of pulmonary
arterial hypertension. N. Eng. J. Med. 2004;351:1425-36.
7. 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.

Actelion Ltd
Actelion Ltd is a biopharmaceutical company with its corporate
headquarters in Allschwil/Basel, Switzerland. Actelion's first drug
Tracleer(R), an orally available dual endothelin receptor antagonist,
has been approved as a therapy for pulmonary arterial hypertension.
Actelion markets Tracleer(R) 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 2000 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(R)).

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

Medical Media Contact
Danielle Bertrand, WeissComm Partners for Actelion
+1 415 946 1056
dbertrand@wcpglobal.com

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Actelion Pharmaceuticals Ltd
Gewerbestrasse 16 Allschwil
Switzerland

WKN: 936767; ISIN: CH0010532478; Index: SBIOM, SLIFE, SMCI, SMIEXP,
SMIM, SPI, SPIEX;
Listed: Main Market in SIX Swiss Exchange;

SOURCE: Actelion Pharmaceuticals Ltd

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