CGP 20712 A (CGP 20712 mesylate) is a highly selective β1-adrenoceptor antagonist with an IC₅₀ of 0.7 nM. CGP 20712 A exhibits ~10,000-fold selectivity over β2-adrenoceptors^[1]. IC50 & Target: IC50: 0.7 nM (β1-adrenoceptor)^[1] In Vitro: In myocytes, the activation of adenylate cyclase causes by β2-adrenoceptors is not detected in the presence of 10 nM, 100 nM or 1000 nM CGP 20712 A (CGP 20712 mesylate), which selectively antagonized beta1-adrenoceptors^[2]. In Vivo: Pretreatment of 8-day-old rats with 5 mg/kg CGP 20712 A do not change the plasma ACTH response to insulin injection^[3].