Discovery and characterization of pyridazino[4,5-b]indol-4-one derivatives as NaV1.8 inhibitors: A novel approach for targeting chronic pain.

Voltage-gated sodium channel NaV1.8 plays a key role in the development and progression of neuropathic and inflammatory pain, making it an important target for chronic pain treatment. However, the development of drugs targeting NaV1.8 and other ion channels is still constrained by the low throughput and high cost of conventional patch-clamp techniques. Additionally, existing NaV1.8 inhibitors suffer from structural uniformity, poor analgesic activity and unfavorable pharmacokinetic properties. In this study, we built a customized virtual screening workflow that combines the structural features of the NaV1.8 binding pocket with large-scale molecular docking, and applied absolute binding free energy (ABFE) calculations to improve both accuracy and efficiency. Using cell membrane chromatography (CMC) combined with whole-cell patch-clamp assays, we identified compound 12 as a lead compound with potent inhibitory activity against NaV1.8. Based on compound 12, 17 derivatives were synthesized, and compound 12d was identified as the most promising one after a series of in vitro and in vivo evaluations. This study not only provides a promising lead compound for chronic pain therapy but also offers a paradigm for the precise design and development of drugs targeting other ion channels.