ATZ1993, an Orally Active and Novel Nonpeptide Antagonist for Endothelin Receptors and Inhibition of Intimal Hyperplasia After Balloon Denudation of the Rabbit Carotid Artery

Abstract

The present experiments were designed to investigate the effect of ATZ1993 {3-carboxy-4, 5-dihydro-1-[1-(3-ethoxyphenyl)propyl]-7-(5-pyrimidinyl)methoxy-[1H]-benz[g]indazole} on the intimal hyperplasia after balloon endothelial denudation of the rabbit carotid artery. ATZ1993 inhibited the specific [¹²⁵I]endothelin (ET)-1 binding not only to ET-receptor subtype A (ET_A) with a pK_i value of 8.69±0.02, but also to ET-receptor subtype B (ET_B) with a pK_i value of 7.20±0.03. Counterscreening in the binding assay (30 different receptors) confirmed that ATZ1993 had a high selectivity for ET receptors. Increases in intima:media ratio and DNA content in the vessel wall were significantly (P<0.005) inhibited by ATZ1993 in a daily dose of 30 mg·200 ml^-1·kg^-1 for 1 week before and 6 weeks after balloon denudation. Inhibition of the intimal hyperplasia with ATZ1993 was determined as approximately 77% for increases in intima:media ratio and DNA content. Plasma concentrations of ATZ1993 ranged between 121.6±26.6 and 131.7±20.9 nM throughout experimental periods. Mean arterial blood pressure, heart rate and body weight gain remained unaffected by administering ATZ1993. These results demonstrate that ATZ1993 is a novel nonpeptide and nonselective ET_A/ET_B-receptor antagonist, and the agent when administered orally inhibits effectively intimal hyperplasia after balloon denudation of the rabbit carotid artery.