Bioisosteric replacement strategy leads to novel DNA gyrase B inhibitors with improved potencies and properties

The identification of novel 4-hydroxy-2-quinolone-3-carboxamide antibacterials with improved properties is of great value for the control of antibiotic resistance. In this study, a series of N-heteroaryl-substituted 4-hydroxy-2-quinolone-3-carboxamides were developed using the bioisosteric replacement strategy. As a result of our research, we discovered the two most potent GyrB inhibitors (WBX7 and WBX18), with IC50 values of 0.816 µM and 0.137 µM, respectively. Additional antibacterial activity screening indicated that WBX18 possesses the best antibacterial activity against MRSA, VISA, and VRE strains, with MIC values ranging between 0.5 and 2 µg/mL, which was 2 to over 32 times more potent than that of vancomycin. In vitro safety and metabolic stability, as well as in vivo pharmacokinetics assessments revealed that WBX18 is non-toxic to HUVEC and HepG2, metabolically stable in plasma and liver microsomes (mouse), and displays favorable in vivo pharmacokinetic properties. Finally, docking studies combined with molecular dynamic simulation showed that WBX18 could stably fit in the active site cavity of GyrB.