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Treatment for Pulmonary Arterial Hypertension (PAH)

Encysive Pharmaceuticals Submits New Drug Application for Thelin

HOUSTON, May 25, 2005 -- Encysive Pharmaceuticals today announced that it has completed the submission of a New Drug Application (NDA) with the U.S. Food and Drug Administration (FDA) for Thelin (sitaxsentan) 100 mg as a once daily oral treatment for patients with pulmonary arterial hypertension (PAH).

The NDA contains the largest database ever assembled in a regulatory filing for PAH, with approximately 900 PAH patients receiving Thelin in clinical evaluations. The Company conducted two randomized, placebo- controlled pivotal Phase III studies in support of worldwide product registrations. The second pivotal Phase III trial, STRIDE-2, was conducted under a Special Protocol Assessment with the FDA and met its primary objective of improved six-minute walk (6MW), with a statistically significant increase of 31.4 meters over placebo (p=0.03). Also in STRIDE-2, Thelin demonstrated a potential advantage in safety. The 100 mg dose of Thelin was associated with a 3% rate of liver function abnormality (elevation in liver enzymes to levels >3 times the upper limit of normal) in the 18-week study, compared to 6% for placebo and 11% for bosentan (Tracleer(R)), the only currently approved oral therapy for PAH.

About Thelin and PAH
Thelin is a small molecule that blocks the action of endothelin, a potent mediator of blood vessel constriction and growth of smooth muscle in vascular walls. Endothelin receptor antagonists may prove to be effective in the treatment of a variety of diseases where the regulation of vascular constriction is important. Thelin is 6,500-fold selective in the targeting of the endothelin A receptor versus the endothelin B receptor.

Pulmonary arterial hypertension (PAH) is a condition that involves high blood pressure and structural changes in the walls of the pulmonary arteries, which are the blood vessels that connect the right side of the heart to the lungs. PAH causes shortness of breath, limits activity, and is eventually fatal unless treated successfully with heart/lung or lung transplantation. PAH is estimated to afflict approximately 100,000 to 200,000 people worldwide, many of whom are children and young women.

The most frequent adverse events that occurred in patients receiving Thelin, which were more common than in placebo-treated patients, were headache, edema, nausea, upper respiratory tract infection, dizziness, insomnia, nasopharyngitis, and nasal congestion. Because Thelin inhibits the metabolism of warfarin, a decreased dose of warfarin is needed when co- administered with Thelin.

About Encysive Pharmaceuticals
Encysive Pharmaceuticals Inc. is a biopharmaceutical company engaged in the discovery, development and commercialization of novel, synthetic, small molecule compounds to address unmet medical needs. Our research and development programs are predominantly focused on the treatment and prevention of interrelated diseases of the vascular endothelium and exploit our expertise in the area of the intravascular inflammatory process, referred to as the inflammatory cascade, and vascular diseases. We have successfully developed one FDA-approved drug, Argatroban, for the treatment of heparin-induced thrombocytopenia that is marketed by GlaxoSmithKline. Our lead drug candidate, Thelin (sitaxsentan), is an endothelin receptor antagonist that has completed final Phase III clinical trials for the treatment of pulmonary arterial hypertension. In addition, we have earlier stage clinical product candidate in development, TBC3711, a next generation endothelin receptor antagonist.

Posted: May 2005

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