Actelion Pharmaceuticals Ltd (VTX:ATLN) Actelion's First-in-class Selective S1P1 Receptor Agonist To Enter Phase II Clinical Development

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ALLSCHWIL, SWITZERLAND - 13 November 2008 - Actelion Ltd (SWX: ATLN) announced that Actelion and Roche have jointly agreed that preclinical and clinical data support progressing Actelion's S1P1 receptor agonist into Phase II clinical development. An update will be presented at Actelion Day 2009, an event held at Actelion's headquarters in Allschwil on 19 February 2009. This event will be a combination of Actelion's annual Media and Analyst Conference and its Research and Development Day.

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The science behind selective S1P1 receptor agonists Sphingosine-1-phosphate (S1P) is a phospholipid released by platelets, mast and other cells. It is currently established [1,2] that S1P stimulates at least five different G-protein coupled receptors (GPCRs): S1P1,2,3,4, and 5. Activation of these GPCRs mediates a complex variety of biological responses, such as lymphocyte migration, endothelial cell proliferation, blood vessel constriction, heart rate modulation and others.

Actelion's efforts in the field of selective S1P1 receptor agonists started in 1999 by focusing on receptors found on the endothelium, the inner lining of blood vessels. The result of these research efforts is Actelion's orally active selective S1P1 receptor agonist.

About autoimmune disorders Autoimmune disorders are diseases caused by the body producing an immune response against its own tissues. The cause of autoimmune disorders is unknown. Some of the most common types of autoimmune disorders include psoriasis, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease and rejection of transplanted organs. These disorders affect millions of people worldwide.

Actelion/Roche Alliance Actelion and Roche entered into an exclusive worldwide collaboration in July 2006 to jointly develop and commercialize Actelion's selective S1P1 receptor agonist, an immunomodulator with the potential for once-a-day oral dosing. The two companies plan to jointly develop and commercialize this novel compound for multiple autoimmune disorders. For the current selective S1P1 receptor agonist, Actelion will fully fund all development activities up to the end of phase II for the first two indications. All subsequent development and commercialization costs will be shared equally between Roche and Actelion. Both companies will co-promote any product resulting from this collaboration and will equally share profit.

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 1800 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).

References 1. Huwiler A, Pfeilschifter J. Biochem Pharmacol. 2008 May 15;75(10):1893-900. Review. 2. Rivera J, Proia RL, Olivera A.Nat Rev Immunol. 2008 Oct;8(10):753-63. Review.

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; Listed: Main Market in SWX Swiss Exchange;



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Actelion Pharmaceuticals Ltd

http://www.actelion.com

ISIN: CH0010532478

Stock Identifier: XSWX.ATLN

US: OTC:ALIOF