Encysive Pharmaceuticals presented the data from a clinical study of Thelin (sitaxsentan) in pulmonary arterial hypertension (PAH), at the European Society of Cardiology Annual Congress in Munich.

Data from the extension of Encysive's multi-centre, pivotal Phase IIb/III STRIDE-1 (Sitaxsentan To Relieve ImpaireD Exercise) clinical trial was presented by clinical investigator Adaani Frost, Baylor College of Medicine, Houston, on Tuesday, August 31, an official release said.

"The long-term evaluation results presented by Dr. Frost suggest that patients may continue to benefit from Thelin with chronic therapy, which we believe provides valuable information to the physician and patient communities in PAH," said Bruce D Given, president and CEO of Encysive Pharmaceuticals. "In order to explore the full therapeutic potential of Thelin, our strategy has been to evaluate Thelin in the broadest population ever for this drug class, and to follow its long-term impact closely," he added.

In the abstract entitled, "Long-term Sitaxsentan Therapy in Pulmonary Arterial Hypertension (PAH)," data from the STRIDE-1 trial extension was analyzed to assess the time course to clinical improvement or deterioration with Thelin at doses of 100 mg and 300 mg.

According to the release, following treatment with a mean duration of 26 weeks and a maximum of 58 weeks, 53 per cent of the 79 patients on 100 mg and 44 per cent of the 91 patients on 300 mg improved at least one New York Heart Association (NYHA) functional class. A substantial portion of those individuals that improved did so within the initial 12 weeks of therapy-64 per cent for 100 mg and 70 per cent for 300 mg.

During the first 12 weeks, liver-function abnormalities greater than three times the upper limit of normal occurred in 0 per cent for 100 mg and 10 per cent for 300 mg. Overall rates of 5 per cent for 100 mg and 21 per cent for 300 mg were reported for the entire treatment course. During treatment, only 5 per cent of patients on 100 mg and 8 per cent on 300 mg experienced NYHA functional class deterioration. While both doses of Thelin are similarly effective in improving functional class, both short- and long-term, the more favourable safety/efficacy profile of 100 mg lends further support to its selection as the maximum clinical dose in ongoing trials of Thelin.

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 targeting the endothelin A receptor.