Integrated computational and experimental approaches for drug repurposing targeting key Mycobacterium tuberculosis proteins

Mycobacterium tuberculosis (Mtb) remains one of the deadliest pathogens worldwide, further complicated by the increasing prevalence of multidrug-resistant (MDR) and extensively drug-resistant strains. In this study, a structure-based virtual screening workflow was employed to repurpose approved drugs from the DrugBank database for six essential Mtb targets: InhA, MmpL3, DprE1, QcrB, GyrB, and LeuRS. Systematic evaluation of protein conformations followed by hierarchical docking and Prime MM-GBSA rescoring yielded 30 candidate compounds for biological testing. Among them, Ozenoxacin, Epirubicin, Idarubicin, Mitoxantrone, and Tosufloxacin showed significant antimycobacterial activity against the H37Rv strain, with Ozenoxacin exhibiting the strongest activity. Ozenoxacin, Epirubicin, and Idarubicin also retained in vitro activity against the tested MDR clinical isolate, and Ozenoxacin further showed additive interactions with rifampicin, isoniazid, ethambutol, and streptomycin, without detectable antagonism. Time-kill assays demonstrated that Ozenoxacin produced a clear dose-dependent delay in bacterial growth in both H37Rv and MDR strains, supporting its sustained growth-inhibitory effect. Molecular docking and molecular dynamics simulations further suggested plausible binding modes of Ozenoxacin and Epirubicin in GyrB and of Idarubicin in DprE1, providing structural hypotheses for their possible target interactions. Overall, these findings suggest that Ozenoxacin and several other active compounds warrant further investigation as potential repurposing candidates against Mtb.