Identification of novel xanthine oxidase inhibitors via virtual screening with enhanced characterization of molybdopterin binding groups

Xanthine Oxidase (XO) is an important therapeutic target for the treatment of hyperuricemia and gout. A virtual screening strategy with enhanced characterization of the molybdopterin binding group (MBG) was applied for the identification of novel XO inhibitors. Briefly, a 3D QSAR pharmacophore with fragment recognition capability was constructed by setting the MBG as a customized-pharmacophore feature. In addition, 2D QSAR was established with descriptors based on density functional theory (DFT), physical and chemical properties as well as topological properties. Descriptors related to metal ion recognition were emphasized to enhance the characterization of the MBG and to improve the screening efficiency. The 3D and 2D QSAR models were combined with the pharmacophore derived from XO-inhibitor complexes and docking with hydrogen bond constraints to screen the compound library of Specs. After two rounds of screening, six compounds with significant inhibition against XO were identified and the most active one XO-33 showed an IC₅₀ of 23.3 nM. These compounds are structurally distinct from the known XO inhibitors, and provide new chemical prototypes for further discovery of potent and novel XO inhibitors.