Pharmacological profile of T-0201, a highly potent and orally active endothelin receptor antagonist

The authors studied the pharmacological properties of N-(6-(2-(5-bromopyrimidin-4-yl)-4-(2-hydroxy-1, 1-dimethylethyl)benzensulfonamide sodium salt sesquihydrate (T-0201), a new nonpeptide endothelin (ET) receptor antagonist, in vitro and in vivo. In binding studies, T-0201 competitively antagonized the specific binding of [125I]-ET-1 to human cloned ETA receptors (the Ki value was 0.015 +/- 0.004 nM). T-0201 weakly inhibited [125I]-ET-1-binding to human cloned ETB receptors; the Ki value was 41 +/- 21 nM. T-0201 shifted the concentration-response curve of ET-1-induced contraction of the isolated rat aorta (ETA receptors) to the right (pA2 = 9.0 +/- 0.2). In the isolated rat trachea, a selective ETB agonist sarafotoxin S6c-induced contraction was inhibited by T-0201 (pA2 = 6.8 +/- 0.3). T-0201 also caused the inhibition of ET-1-induced contraction of the isolated rabbit pulmonary artery (pA2 = 5.7 +/- 0.3). In anesthetized rats, T-0201 (0.01-1 mg/kg) inhibited the pressor response to exogenous big ET-1 (1 nmol/kg i.v.), after both i.v. and p.o. administration, in a dose-dependent manner. The significant inhibitory effect of orally administered T-0201 on big ET-1-induced pressor response lasted for 4 hr at 0.1 mg/kg and for 8 hr at 1 mg/kg. Thus the present study demonstrates that T-0201 is a highly potent, long-lasting, orally active and selective ETA receptor antagonist.