New Thelin Data to be Presented at American Thoracic Society's International Conference

STRIDE-2 Pivotal Trial Results to be Highlighted in Oral Presentation


HOUSTON, April 20, 2005 (PRIMEZONE) -- Encysive Pharmaceuticals (NASDAQ:ENCY) today announced that new data on Thelin(tm) (sitaxsentan) from the Company's pivotal Phase III STRIDE-2 clinical trial in pulmonary arterial hypertension will be presented at the annual International Conference of the American Thoracic Society (ATS), May 20-25 in San Diego.

Results from STRIDE-2, Encysive's final Phase III trial, will be highlighted in an oral presentation entitled, "The STRIDE-2 Trial: Does Selectivity Matter in Endothelin Antagonism for PAH." The presentation will take place on Monday, May 23 at 9:30 a.m. PT, at the San Diego Convention Center, and be given by Robyn J. Barst, M.D., Professor of Pediatrics at Columbia University College of Physicians and Surgeons, and Director, New York Presbyterian Hospital Pulmonary Hypertension Center.

Six additional Thelin abstracts will be presented on Sunday, May 22 from 8:15 a.m. to 4:15 p.m. PT, during the ATS Thematic Poster Session for Pulmonary Hypertension:


 -- "Sustained Efficacy with the Highly Selective Orally-Active
    Endothelin-A Receptor Antagonist, Sitaxsentan, after Two
    Years of Therapy in Patients with Pulmonary Arterial
    Hypertension" (D. Langleben, M.D., et al.); Poster K16

 -- "No Clinical Interaction between Sitaxsentan and Sildenafil"
    (T.C. Coyne, M.D., et al.); Poster K70

 -- "Sitaxsentan for Pulmonary Arterial Hypertension (PAH)
    Patients with Clinical Deterioration or Significantly
    Abnormal Liver Function Test on Bosentan" (A. Frost, M.D.,
    et al.); Poster K52

 -- "Sitaxsentan Treatment for Patients with Pulmonary Arterial
    Hypertension (PAH) Failing Bosentan Treatment" (R. Benza, M.D.,
    et al.); Poster K68

 -- "Do Liver Function Abnormalities with Bosentan Recur with
    Sitaxsentan?" (P.C. Garces, M.D., et al.) Poster K65

 -- "Comparison of Placebo-Controlled and Open Label Trials in
    Pulmonary Arterial Hypertension" (A. Moeller, et al.)
    Poster K71

Additionally, the Company is supporting, via an unrestricted educational grant, an evening postgraduate seminar entitled "Pulmonary Arterial Hypertension: Future Therapeutic Options and Their Impact on Treatment Objectives," to be held Tuesday, May 24 from 7 p.m. to 9 p.m. PT in Marriott Hall 4-5-6, San Diego Marriott Hotel and Marina.

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 80,000 to 100,000 people worldwide, many of whom are children and young women.

Side effects of Thelin seen in the program to date, and which occurred more frequently than in placebo, include liver dysfunction (increased ALT and AST), headache, edema, constipation, nasal congestion and flushing. 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, ThelinTM (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 candidates in development including TBC3711, a next generation endothelin receptor antagonist, and bimosiamose, being developed by our majority-owned German affiliate, Revotar Biopharmaceuticals AG. To learn more about Encysive Pharmaceuticals please visit our web site: www.encysive.com.

This press release contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements are subject to certain risks, trends and uncertainties that could cause actual results to differ materially from those projected. Among those risks, trends and uncertainties are our estimate of the sufficiency of our existing capital resources, our ability to raise additional capital to fund cash requirements for future operations, timelines for initiating new clinical trials, planned announcements of clinical data, the possibility of obtaining regulatory approval, our ability to manufacture and sell any products, potential drug candidates, their potential therapeutic effect, market acceptance or our ability to earn a profit from sales or licenses of any drug candidate, our ability to discover new drugs in the future, and our ability to establish future collaborative arrangements. In particular, careful consideration should be given to cautionary statements made in the various reports Encysive, including as Texas Biotechnology Corporation, has filed with the Securities and Exchange Commission. Encysive undertakes no duty to update or revise these forward-looking statements.

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