Sitaxsentan Therapy for Pulmonary Arterial Hypertension

Sitaxsentan may benefit patients with pulmonary arterial hypertension by blocking the vasoconstrictor effects of endothelin-A while maintaining the vasodilator/clearance functions of endothelin-B receptors. Patients with pulmonary arterial hypertension that was idiopathic, related to connective tissue disease or congenital heart disease, were randomized to receive placebo (n = 60), sitaxsentan 100 mg (n = 55), or sitaxsentan 300 mg (n = 63) orally once daily for 12 weeks. The primary endpoint was change in peak VO(2) at Week 12. Secondary endpoints included 6-minute walk, New York Heart Association class, VO(2) at anaerobic threshold, VE per carbon dioxide production at anaerobic threshold, hemodynamics, quality of life, and time to clinical worsening. Although the 300-mg group increased peak VO(2) compared with placebo (+3.1%, p < 0.01), none of the other endpoints derived from cardiopulmonary exercise testing were met. However, both the 100-mg dose and the 300-mg dose, compared with placebo, increased 6-minute walk distance (100 mg: +35 m, p < 0.01; 300 mg: +33 m, p < 0.01); functional class, cardiac index, and pulmonary vascular resistance also improved (p < 0.02 for each parameter at both doses). The incidence of elevated aminotransferase values (> three times normal) was 3% for the placebo group, 0% for the 100-mg group, and 10% for the 300-mg group.