Design, Synthesis, and Xanthine Oxidase Inhibitory Activity of 4-(5-Aminosubstituted-4-cyanooxazol-2-yl)benzoic Acids

Xanthine oxidase is a known therapeutic target for the treatment of hyperuricemia and related diseases. Despite the availability of current drugs such as allopurinol and febuxostat, the search for new compounds to effectively inhibit this enzyme remains relevant. In our study, 75 virtual structures of 4-(5-aminosubstituted-4-cyanooxazol-2-yl)benzoic acids with structural similarity to febuxostat were designed for evaluation of their potency against xanthine oxidase. After molecular docking simulations, eight compounds were selected for synthesis and in vitro testing. The synthesized compounds were found to exhibit in vitro xanthine oxidase inhibitory activity in the nanomolar concentration range. The most effective inhibitors with 4-benzylpiperidin-1-yl or 1,2,3,4-tetrahydroisoquinolin-2-yl substituents at position 5 of the oxazole ring had IC₅₀ values close to that of febuxostat. The kinetic data suggest a mixed-type inhibition when the inhibitor binds preferentially to the free enzyme rather than to the enzyme-substrate complex. Molecular docking and molecular dynamic simulations were carried out to get insight into the key interactions of the inhibitors bound to the xanthine oxidase active site.