Identification of novel <i>Mycobacterium tuberculosis</i> leucyl-tRNA synthetase inhibitors with antibacterial activity

Tuberculosis has become the world’s most lethal infectious disease. A major challenge in treating tuberculosis is the multidrug resistance of <i>Mycobacterium tuberculosis</i> to existing antibiotics. Therefore, there is an urgent need to discover new antituberculosis agents with unexploited mechanisms of action. The aim of the work was to develop inhibitors of mycobacterial leucyl-tRNA synthetase (LeuRS) with antibacterial activity. The virtual screening of compound collection containing about 250,000 ligands into aminoacyl-adenylate binding site of <i>M. tuberculosis</i> LeuRS was performed with AutoDock 4.2 software. The inhibitory activity of compounds toward recombinant LeuRS was studied in aminoacylation assay using ¹⁴C-labeled L-leucine. Antibacterial activity was investigated toward <i>M. tuberculosis</i> H37Rv strain under four different conditions. According to the data of biochemical screening, we have found <i>M. tuberculosis</i> LeuRS inhibitors among <i>N</i>-(5-Benzyl-thiazol-2-yl)-2-(1-phenyl-1H-tetrazol-5-ylsulfanyl)-acetamide deivatives, which decrease enzyme activity with IC₅₀ values in micromolar range. The most promising compound, N-(5-Benzyl-thiazol-2-yl)-2-[4-(4-methoxy-phenyl)-1H-tetrazol-5-ylsulfanyl]-acetamide, reveals potent antibacterial activity with the best minimum inhibitory concentration (MIC) value of 4.7 µM. <i>N</i>-(5-Benzyl-thiazol-2-yl)-2-(1-phenyl-1H-tetrazol-5-ylsulfanyl)-acetamide scaffold can be valuable for further biological research and chemical optimization. Using molecular docking approach followed with in vitro aminoacylation assay, we found novel chemical class of <i>Mycobacterium tuberculosis</i> leucyl-tRNA synthetase (LeuRS) inhibitors decreasing the enzyme activity with IC₅₀ values in micromolar range. Among them we identified one compound – N-(5-Benzyl-thiazol-2-yl)-2-[4-(4-methoxy-phenyl)-1H-tetrazol-5-ylsulfanyl]-acetamide, which demonstrates potent antibacterial activity with the MIC value of 4.7 μM.