Synthesis and evaluation of a novel inhibitor for the α5-GABAA receptor in the treatment of peripheral neuralgia: Evidence from MD simulation and in vivo studies.

Background and purpose: Peripheral neuropathic pain (PNP) remains challenging to treat, because of the limited efficacy of current therapies and their central nervous system side effects. Targeting the α5-GABA_A receptor (GABRA5) has shown potential in addressing the limitations of existing therapies. This study aimed to develop and evaluate SR-419, a novel GABRA5 inhibitor, for its potential therapeutic application in PNP.

Experimental approach: SR-419 was synthesised via an optimised route and characterised using nuclear magnetic resonance (NMR). Molecular docking and molecular dynamics (MD) simulations were performed to predict its binding mode. Analgesic efficacy was assessed in rat models of post-herpetic neuralgia (PHN) and spared nerve injury (SNI). Mechanistic studies included cellular thermal shift assays (CETSA) and pharmacological validation using QH-II-66, a GABRA5-selective agonist.

Key results: The results of NMR analysis confirmed that we had successfully developed a novel chemistry route to synthesise the target compound. SR-419 bound stably to GABRA5 in silico and showed high selectivity in vitro. CETSA confirmed direct engagement of SR-419 with intracellular GABRA5. SR-419 produced dose-dependent analgesia in vivo, without crossing the blood-brain barrier or causing sedation or motor impairment. Its analgesic effect was abolished by QH-II-66, confirming GABRA5 involvement. Toxicology studies revealed excellent safety in acute and chronic settings.

Conclusions and implications: SR-419 is a peripherally acting GABRA5 inhibitor with potent analgesic efficacy and a favourable safety profile. Its target-specific mechanism suggests that it is a promising candidate for treating PNP and avoiding central side effects.