N-(3-cyano-1H-indol-5-yl)isonicotinamide and N-(3-cyano-1H-indol-5-yl)-1H-benzo[d]imidazole-5-carboxamide derivatives: Novel amide-based xanthine oxidase inhibitors

Our previous work demonstrated that amide is an efficient linker to explore chemical space of xanthine oxidase (XO) inhibitors that are entirely different from febuxostat and topiroxostat. In this effort, with 3-cyano-1H-indol-5-yl as a key moiety, two series of amide-based XO inhibitors, N-(3-cyano-1H-indol-5-yl)isonicotinamides (2a-w) and N-(3-cyano-1H-indol-5-yl)-1H-benzo[d]imidazole-5-carboxamides (3a-i), were designed and synthesized. The structure-activity relationship investigation identified N-(3-cyano-1-cyclopentyl-1H-indol-5-yl)-1H-benzo[d]imidazole-5-carboxamide (3i, IC50 = 0.62 μM) as the most promising compound, with 14.4-fold higher in vitro inhibitory potency than allopurinol (IC50 = 8.91 μM). Molecular simulations provided reasonable interaction modes for the representative compounds. Furthermore, in vivo activity evaluation demonstrated that compound 3i (oral dose of 12.8 mg/kg) has obviously hypouricemic effect on a potassium oxonate induced hyperuricemic rat model. Cytotoxicity assay and ADME prediction also supported that 3i is an excellent lead for further exploration of amide-based XO inhibitors.