8-Substituted Triazolobenzodiazepines: In Vitro and In Vivo Pharmacology in Relation to Structural Docking at the α1 Subunit-Containing GABAA Receptor.

Lalit K Golani,Roman Furtmüller,Daniela Rüedi-Bettschen,James M Cook,Chitra Edwanker,Shenming Huang,James K Rowlett,Donna M Platt,Werner Sieghart,Michael M Poe

doi:10.3389/fphar.2021.625233

Abstract

In order to develop improved anxiolytic drugs, 8-substituted analogs of triazolam were synthesized in an effort to discover compounds with selectivity for α2/α3 subunit-containing GABAA subtypes. Two compounds in this series, XLi-JY-DMH (6-(2-chlorophenyl)-8-ethynyl-1-methyl-4H-benzo [f][1,2,4]triazolo[4,3-a][1,4]diazepine) and SH-TRI-108 [(E)-8-ethynyl-1-methyl-6-(pyridin-2-yl)-4H-benzo [f][1,2,4]triazolo[4,3-a][1,4]diazepine], were evaluated for in vitro and in vivo properties associated with GABAA subtype-selective ligands. In radioligand binding assays conducted in transfected HEK cells containing rat αXβ3γ2 subtypes (X = 1,2,3,5), no evidence of selectivity was obtained, although differences in potency relative to triazolam were observed overall (triazolam > XLi-JY-DMH > SH-TRI-108). In studies with rat αXβ3γ2 subtypes (X = 1,2,3,5) using patch-clamp electrophysiology, no differences in maximal potentiation of GABA-mediated Cl− current was obtained across subtypes for any compound. However, SH-TRI-108 demonstrated a 25-fold difference in functional potency between α1β3γ2 vs. α2β3γ2 subtypes. We evaluated the extent to which this potency difference translated into behavioral pharmacological differences in monkeys. In a rhesus monkey conflict model of anxiolytic-like effects, triazolam, XLi-JY-DMH, and SH-TR-108 increased rates of responding attenuated by shock (anti-conflict effect) but also attenuated non-suppressed responding. In a squirrel monkey observation procedure, both analogs engendered a profile of sedative-motor effects similar to that reported previously for triazolam. In molecular docking studies, we found that the interactions of the 8-ethynyl triazolobenzodiazepines with the C-loop of the α1GABAA site was stronger than that of imidazodiazepines XHe-II-053 and HZ-166, which may account for the non-sedating yet anxiolytic profile of these latter compounds when evaluated in previous studies.

Highlights

Anxiolytic and sedative benzodiazepines (BZs) produce their pharmacological effects by enhancing the inhibitory action of γ-aminobutyric acid (GABA) at type A GABA (GABAA) receptors throughout the brain
Its affinity was markedly lower than both triazolam and XLi-JY-DMH at all receptor subtypes
Over the past two decades, intense interest in exploiting the BZ-sensitive GABAA receptor subtypes has resulted in clinical candidates that lack some of the deleterious side effects associated with this class of drugs

Summary

Introduction

Anxiolytic and sedative benzodiazepines (BZs) produce their pharmacological effects by enhancing the inhibitory action of γ-aminobutyric acid (GABA) at type A GABA (GABAA) receptors throughout the brain. Recent research efforts have been directed at developing compounds that are “functionally selective” in that they may bind to all four BZ-sensitive subunits of the GABAA receptor, but have intrinsic efficacy at only the desired GABAA receptor subtypes. This functional subtype-selectivity framework has been used to develop anxiolytics that potentially have reduced side effects. One goal of our studies was to assess the extent to which the favorable in vitro and in vivo profile of imidazodiazepines may be extended to the 8-substituted triazolobenzodiazepine series

Methods

Results

Conclusion