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Sitaxsentan Improves Functional Class in Pulmonary Hypertension: Presented at ATS

By Jill Stein

SAN DIEGO, C.A. -- May 25, 2006 -- Investigators report a significant boost in functional class in patients with class II-IV pulmonary arterial hypertension (PAH) who are treated with 100 mg/day of sitaxsentan sodium (Thelin).

Sitaxsentan is an investigational, once-daily, oral selective endothelin A receptor antagonist. It is 6500 times more selective for endothelin A than endothelin B receptors, according to the poster presented here at the International Conference of the American Thoracic Society (ATS).

Robert J. Oudiz, MD, director, division of pulmonary hypertension, Harbor-UCLA Medical Center, Torrance, California, and colleagues conducted a combined analysis of the 12-week Sitaxsentan to Relieve ImpaireD Exercise (STRIDE)-1, 18-week STRIDE-2, and 18-week STRIDE-4 trials that examined sitaxsentan 50 mg, 100 mg, and 300 mg versus placebo for the treatment of PAH of primary or secondary etiologies (due to collagen vascular disease or certain congenital heart defects).

The 100-mg dose has been identified as the optimal dose based on a relative risk/benefit analysis. The current analysis compared only changes in New York Heart Association/World Health Organization (NYHA/WHO) functional class in the 147 patients treated with the 100-mg dose of sitaxsentan and the 153 placebo-treated patients for all 3 trials.

Because patients with mild PAH have frequently been excluded from PAH trials, a preplanned subanalysis was conducted for the change in functional class in patients with baseline functional class II separately from functional class III to IV. The subanalysis included 60 sitaxsentan- and 64 placebo-treated patients.

The treatment groups were similar with respect to baseline clinical and demographic characteristics.

At endpoint, functional class had improved significantly in sitaxsentan- versus placebo-treated patients (P =.0002), Dr. Oudiz reported.

In the subgroup with milder disease at enrollment, sitaxsentan-treated patients had improvement of at least 1 functional class in 18% of patients, there was no changed in 80%, and functional class worsened to class III to IV in 2%. Among placebo patients, changes were 9%, 77%, and 14%, respectively (P =.01).

Among patients with functional class III to IV at baseline, 32% of patients in the sitaxsentan group had an improvement in functional class, 68% had no change in functional class, and no patient had a deterioration in functional class. The corresponding figures for placebo were 20%, 72%, and 8%, respectively (P =.007).

Pulmonary arterial hypertension is a progressive disorder of the pulmonary vasculature characterized by progressive pulmonary vascular remodeling, increased pulmonary vascular resistance, sustained elevations of pulmonary arterial pressure, and progressive dyspnea. The condition results in profound functional limitations, right ventricular failure, and ultimately death.

The study was sponsored by Encysive Pharmaceuticals in Houston, Texas.


[Presentation title: Functional Class Improvement with Sitaxsentan in Patients With Class II-IV Pulmonary Arterial Hypertension (PAH). Abstract 824]

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