Actelion and Nippon Shinyaku enter into a license agreement on novel PAH compound

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ALLSCHWIL/BASEL, SWITZERLAND and KYOTO - 21 April 2008 - Actelion Ltd
(SWX: ATLN) and Nippon Shinyaku (TYO: 4516) announced today that the
two companies have signed a license agreement on a novel orally
available PGI2 receptor agonist NS-304 originally discovered and
synthesized by Nippon Shinyaku for the treatment of pulmonary
arterial hypertension (PAH), based on the previous binding letter of
intent.

The agreement was signed in a formal ceremony at Nippon Shinyaku
Headquarters in Kyoto by Jean-Paul Clozel, M.D. and Chief Executive
Officer of Actelion and Shigenobu Maekawa, President of Nippon
Shinyaku. Also present at the ceremony was Satoshi Tanaka, Dr. med.
Sci., President and Representative Director of Actelion
Pharmaceuticals Japan Ltd.

Under the terms of this license agreement, Nippon Shinyaku will
receive from Actelion an upfront payment and additional milestone
payments based on development stage and sales achievement. Nippon
Shinyaku will also receive royalties on sales. In addition, this
agreement enables Nippon Shinyaku to explore the possibility of
co-development in Japan of a compound which is being developed by
Actelion globally.

In order to promptly bring NS-304 to the market of PAH and other
possible indications, Actelion will take over the phase IIa clinical
study being conducted by Nippon Shinyaku in Europe and be responsible
for global development and commercialization of NS-304 outside Japan.
The two companies will co-develop and co-commercialize NS-304 in
Japan.

NS-304, originally discovered and synthesized by Nippon Shinyaku, is
an orally available long acting prostaglandin I2 receptor agonist),
which stimulates PGI2 receptor in blood vessels and exerts
vasodilating effects. NS-304 has major potential as a novel treatment
of PAH. Nippon Shinyaku has recently completed phase I evaluation in
the United Kingdom. A phase II program in PAH patients was initiated
in Europe at the end of 2007.

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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
focuses on the discovery, development and marketing of innovative
drugs for significant unmet medical needs. Actelion shares are traded
on the SWX Swiss Exchange (ticker symbol: ATLN).
Nippon Shinyaku
For further information on Nippon Shinyaku please visit:
http://www.nippon-shinyaku.co.jp/english/index.html

For further information please contact:
Nippon Shinyaku Co., Ltd.
Toshihiro Yoshioka
General Manager of Corporate Communications Dept.
+81 75 321 9103
+81 357 745 114
http://www.nippon-shinyaku.co.jp/english/index.html

Actelion Pharmaceuticals Ltd, Gewerbestrasse 16, CH-4123 Allschwil
Roland Haefeli
Vice President, Head of Investor Relations & Public
Affairs
+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;
Listed: Main Market in SWX Swiss Exchange;