Synthesis and pharmacological evaluation of benzimidazole amine derivatives as novel allosteric antagonists for β2-adrenergic receptor.

Based on the previous research addressing the insufficient stability of benzimidazole amide derivatives, in this study we synthesized two novel classes of the allosteric antagonists for the β2-adrenergic receptor (β2AR) through structural optimization: nine benzimidazole amide derivatives (B series) and sixteen N-benzylbenzimidazole amine derivatives (C series), by eliminating aniline units and amide bonds, respectively. The GloSensor cAMP accumulation assay showed that most of the new compounds maintained good allosteric antagonism against the β2AR. Specifically, the allosteric activity of BY1 in B series was 2.44 times that of the lead compound Cmpd-15, and CY2 in C series was 2.53 times that of Cmpd-15. Moreover, both BY1 and CY2 were capable of negatively modulating the functional activity of isoproterenol, consistent with negative allosteric modulation. Drug-like evaluation showed that CY2 had no cellular or acute toxicity, its solubility (243.27 μM) was approximately 13 times that of Cmpd-15, and in in vivo pharmacokinetic studies, its half-life of 3.78 h was significantly superior to Cmpd-15. The results showed that the non-amide derivative CY2 exhibited excellent performance in terms of allosteric activity, solubility, safety, and pharmacokinetic properties, and has good development prospects.