Targeting voltage-gated proton channel H_V1: Optimised 5-phenyl-2-aminoimidazoles with anticancer potential

The voltage-gated proton channel (H_V1) has been linked to the development of tumours, neuroinflammatory diseases, immune disorders and infertility, making H_V1 inhibitors promising candidates for therapeutic development. In this study, we designed and synthesized an optimised series of 5-phenyl-2-aminoimidazole-based H_V1 inhibitors, with the most potent compounds exhibiting low micromolar IC₅₀ values. Structural analysis highlighted the importance of an unsubstituted 2-aminoimidazole core and flexible linkers for optimal ligand-channel binding, driven by hydrogen bonding and hydrophobic interactions. Antiproliferative assays showed that the most potent H_V1 inhibitors had IC₅₀ values in the low micromolar range, with greater efficacy against THP-1 cells (human monocytic leukaemia), which express H_V1 at high levels, compared to MCF-7 cells (human breast cancer) with lower H_V1 expression. The type II compounds exhibited superior drug-like properties, including improved solubility, plasma protein binding and permeability compared to previous 5-phenyl-2-aminoimidazole-based H_V1 inhibitors, as well as robust metabolic stability. However, selectivity over the K_V1.3 and Na_V1.5 channels remained limited. This work advances the development of H_V1 inhibitors. It provides valuable chemical tools to study the role of H_V1 in disease pathogenesis and lays the foundation for new therapeutic strategies targeting H_V1-mediated signalling pathways.