Actelion Initiates Phase IIb/III Program With Clazosentan

New Study CONSCIOUS-1 to Determine Dose and Clinical Impact Following Encouraging Phase IIa Study Data


ALLSCHWIL, Switzerland, Dec. 22, 2004 (PRIMEZONE) -- Actelion Ltd (Other OTC:ALIOF) (SWX:ATLN) announced today it has initiated the comprehensive global Phase IIb/III development program for clazosentan, an intravenous endothelin receptor antagonist. This follows the completion of discussions with regulatory authorities in both the US and the European Union on all aspects of the clinical program, including clinical efficacy endpoints.

The multi-center, international, double-blind, randomized, placebo-controlled, parallel group, dose-finding study CONSCIOUS-1 (Clazosentan to Overcome Neurological iSChemia and Infarct OccUrring after Subarachnoid hemorrhage) will analyze the efficacy of 3 dose levels of clazosentan in preventing the occurrence of cerebral vasospasm following SAH, assessed by angiography. As a secondary endpoint, the study will also assess the ability of clazosentan to reduce the occurrence of early morbidity/mortality as well as the effect of clazosentan on clinical outcome, and overall tolerability.

First centers in Europe have started to screen patients for enrollment in the study, with centers in North America and Israel to follow in early 2005. Overall, the study is expected to recruit 400 patients in 65 centers worldwide. Study results are expected in the first half of 2006. These results will determine the need, size and duration of a potential Phase III study.

Promising Phase IIa data shows prevention of vasospasm following SAH

Actelion decided to embark on a large-scale pivotal program for clazosentan given the promising results in an earlier Phase IIa study. In this placebo-controlled study with 34 patients, there were significantly fewer and also less severe cases of vasospasms reported in the clazosentan group compared to placebo. Importantly, there were also fewer patients with new cerebral infarcts in the clazosentan group. Infusions of clazosentan were generally well tolerated, with no effects on blood pressure or other vital signs.

The full data of this promising Phase IIa study will become available through publication in a peer-reviewed scientific journal in the first half of 2005. In early February, the data will also be presented at the 2005 Joint Annual Meeting of the AANS/CNS Cerebrovascular Section and The American Society of Interventional & Therapeutic Neuroradiology in New Orleans.

Actelion and Axovan

Actelion acquired clazosentan through its acquisition of privately held Axovan in the fall of 2003. At this point in time, the company paid CHF 53 million out of a total consideration of CHF 231 million. Upon now initiating Phase IIb/III development, Actelion is now making an additional capital payment to Axovan shareholders of CHF 32.5 million. This capital payment, as well as further milestones due upon achieving additional development steps as well as registering and marketing the drug on a global basis, are expected to be treated as Goodwill and are therefore not P&L effective on payment.

About vasospasm following subarachnoid hemorrhage (SAH)

Vasospasms following subarachnoid hemorrhage (SAH) occur when the rupture of an aneurysm on the cerebral vessels leads to release of blood into the subarachnoid space of the brain. Intravascular coiling or surgical clipping is usually required to stop the bleeding and prevent further episodes. Vasospasm leading to neurological deficits and death tend to occur in the first 3-12 days following the hemorrhage. Currently, there is no satisfactory prevention or treatment option.

Actelion Ltd

Actelion Ltd is a biopharmaceutical company with its corporate headquarter 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 as well as 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).



 For further information please contact:
 Actelion Ltd, Gewerbestrasse 16, CH-4123 Allschwil

 Investor Contact    Roland Haefeli   +41 61 487 34 58
                                      +1 650 624 6936

 Media Contact       Peter Engel      +41 61 487 36 28
                                      +1 650 624 6996
 http://www.actelion.com

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