Encysive Pharmaceuticals Announces Full Results for Sitaxsentan in Pulmonary Arterial Hypertension.

Business Editors/Health/Medical Writers

American Thoracic Society's International Conference

HOUSTON--(BUSINESS WIRE)--May 19, 2003

Results Presented at the American Thoracic Society's

International Conference, Investor Webcast to be Held Tuesday,

May 20, 2003 at 10:30 AM EST 

Encysive Pharmaceuticals (Nasdaq:ENCY) today presented full results from the STRIDE (Sitaxsentan To Relieve ImpaireD Exercise) in Pulmonary Arterial Hypertension Phase IIb/III, double-blind, placebo-controlled clinical trial. Researchers found that sitaxsentan 100 mg and 300 mg provided clinical benefit in these patients, while the 100 mg dose was better tolerated. The clinical results were presented by Robyn J. Barst, M.D., Director, New York Presbyterian Pulmonary Hypertension Center, Columbia University College of Physicians and Surgeons, New York, N.Y., in an oral presentation. Additional results of hemodynamic measurements were presented during a poster session at the meeting.

Both doses of sitaxsentan (100 mg and 300 mg, administered once daily) showed equivalent and statistically significant improvements in six-minute walk distance (P less than 0.01 vs. placebo) and New York Heart Association (NYHA) functional class (p less than 0.02 vs. placebo), while improving cardio-pulmonary hemodynamics. The 300 mg dose also showed an increase in percent predicted peak VO2. While percent predicted peak VO2 was the primary endpoint in the STRIDE trial, six-minute walk distance has been the regulatory standard. The U.S. Food and Drug Administration (FDA) has indicated acceptance of STRIDE as pivotal at 100 mg on the strength of the six-minute walk results. The soon-to-initiate second pivotal trial, STRIDE II, will utilize six-minute walk distance as the primary endpoint and will not include peak VO2 testing.

"STRIDE was ambitious in design, including patients with mild disease with high baseline six-minute walk distances and NYHA Class II disease, as well as, patients with pulmonary arterial hypertension (PAH) associated with congenital heart disease; patients which have been excluded from PAH clinical trials with epoprostenol and with other endothelin receptor antagonists," said Dr. Barst. "In an exploratory analysis using more traditional entry criteria, sitaxsentan showed robust performance."

Of the 178 patients enrolled in STRIDE, none of the patients in the 100 mg group discontinued due to adverse events or for other reasons, versus five patients from the placebo group and seven from the 300 mg group. The most frequent adverse events that occurred in patients receiving sitaxsentan and that were more common than in placebo-treated patients, were headache, peripheral edema, nasal congestion and dizziness. Liver abnormalities have previously been recognized as complications related to the endothelin antagonist class of drugs. Liver abnormalities in the STRIDE trial were defined as elevated serum aminotransferase values that were more than three times normal. Incidences of liver abnormalities in STRIDE, which reversed in all cases, were 3% for the placebo group, 0% for the sitaxsentan 100 mg group and 9.5% for the sitaxsentan 300 mg group. When total exposures from STRIDE and the extension trial are considered, 5% of patients receiving 100 mg and 21% receiving 300 mg of sitaxsentan developed elevations. All elevations resolved with discontinuation of drug.

"The increased six-minute walk distance and safety profile seen at the 100 mg dose is extremely encouraging," said Bruce D. Given, M.D., President and CEO of Encysive. "These positive results with the lower dose support our decision to include the 100 mg and an even lower 50 mg dose in the STRIDE II trial. We are determined to bring patients with PAH, many of whom are children or young adults, an important alternative to current therapies, one which combines endothelin A receptor selectivity with the convenience of once daily dosing."

ATS Webcast / Conference Call Information

Encysive Pharmaceuticals will host a webcast and conference call in conjunction with the American Thoracic Society's (ATS) International Conference on Tuesday, May 20 at 10:30 AM Eastern Time, hosted by Dr. Bruce Given, with Dr. Robyn Barst providing the data overview. The conference call will be available live on the Company's Web site (www.encysive.com) with accompanying slide presentation. To participate in the call, dial 651/291-0900. A replay of the conference call will also be available until Wednesday, May 21 at 11:59PM Eastern time. To access the replay, dial 320/365-3844 and use access code 684924. A replay of the conference call will also be available on the Company's Web site.

About STRIDE and STRIDE II

The STRIDE trial was designed to assess the safety and efficacy of sitaxsentan in patients with NYHA Class II, III and IV PAH. PAH could be of primary etiology or secondary to collagen vascular disease or congenital heart disease. The trial enrolled 178 patients who were randomized to either sitaxsentan 100 mg, sitaxsentan 300 mg or placebo treatment once a day and were treated for 12 weeks. Patients successfully completing the 12-week trial were eligible to enter a double-blind extension. Patients initially randomized to 100 mg or 300 mg of sitaxsentan stayed on those doses. Patients initially randomized to placebo were re-randomized to either of the two doses of sitaxsentan. Patients were treated for as long as 55 weeks.

STRIDE II will be a 240 patient trial including patients with WHO Class II-IV PAH of primary or secondary etiologies (due to collagen vascular disease or certain congenital heart defects) with an entry six-minute walk distance of less than or equal to 450 meters. Patients will be randomized to receive placebo, 50 or 100 mg of sitaxsentan or bosentan.

About Sitaxsentan and PAH

Sitaxsentan is a small molecule that antagonizes 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. Sitaxsentan is a highly selective endothelin A receptor antagonist and is 6000 times more selective for endothelin A than endothelin B receptors.

Pulmonary arterial hypertension 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 shortens life-expectancy. PAH is estimated to afflict over 100,000 people worldwide, many of whom are young adults.

About Encysive Pharmaceuticals

Encysive Pharmaceuticals (formerly Texas Biotechnology Corporation), a biopharmaceutical company focused on the discovery, development and commercialization of novel drugs, is recognized for our expertise in small molecule drug development and vascular biology. Argatroban, our first FDA-approved product, is being marketed by GlaxoSmithKline for heparin-induced thrombocytopenia. Encysive Pharmaceuticals is in Phase III development of the endothelin antagonist, sitaxsentan, for pulmonary arterial hypertension. Our majority-owned affiliate, Revotar Biopharmaceuticals AG, is in Phase II development with the selectin antagonist bimosiamose in asthma, psoriasis and atopic dermatitis. Encysive Pharmaceuticals has several other research and development programs ongoing for a range of cardiovascular and inflammatory diseases. 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 timing and cost of our clinical trials, attainment of research and clinical goals and milestones of product candidates, attainment of required government approvals, sales levels of our products and availability of financing and revenues sufficient to fund development of product candidates and operations. In particular, careful consideration should be given to cautionary statements made in the various reports Encysive Pharmaceuticals, including as Texas Biotechnology Corporation, has filed with the Securities and Exchange Commission. The company undertakes no duty to update of revise these forward-looking statements.