Design, synthesis, and biological evaluation of benzoisonicotinamide derivatives as novel xanthine oxidase inhibitors guided by metabolic stability.

In our previous work, we identified TS10, an isonicotinamide-based xanthine oxidase (XO) inhibitor with excellent in vitro enzymatic activity. However, its poor metabolic stability, primarily caused by the metabolically labile phenyl benzyl ether moiety, may have contributed to its limited in vivo efficacy. In the present study, two optimization strategies, including all-carbon scaffold replacement and phenyl-O-piperidine/tetrahydropyrrole reconstruction, were employed to improve the metabolic stability and overall drug-like properties of TS10. Among the synthesized derivatives, S40 exhibited potent XO inhibitory activity comparable to TS10 and showed stable interactions within the XO active site as demonstrated by molecular modeling. Metabolic stability studies revealed that S40 displayed significantly improved stability over TS10 in both rat liver microsomes (t1/2 = 131.5 min) and rat plasma. Pharmacokinetic evaluation further demonstrated that S40 achieved measurable systemic exposure after oral administration, whereas TS10 showed plasma exposure below the lower limit of quantification (LLOQ). In hyperuricemic rat models, S40 dose-dependently reduced serum uric acid levels and ameliorated renal and hepatic histopathological damage. The improved metabolic stability and detectable systemic exposure of S40 support a potential correlation between these properties and its enhanced in vivo activity. Collectively, these findings identify S40 as a promising lead compound for further development as a novel anti-hyperuricemia agent.