Oxadiazolone derivatives against M. tuberculosis

Oxadiazolone (OX) derivatives have been investigated for their antimycobacterial activity against three pathogenic slow-growing mycobacteria: Mycobacterium marinum, Mycobacterium bovis BCG and the avirulent Mycobacterium tuberculosis (M. tb) mc26230. The encouraging MIC values obtained prompted us to test them against virulent M. tb H37Rv growth either in broth medium or inside macrophages. The OX compounds displayed a diversity of action and were found to act either on extracellular M. tb growth only with moderated MIC, or both intracellularly on infected macrophages as well as extracellularly on bacterial growth. One OX derivatives, HPOX, was selected and used in a competitive labelling/enrichment assay against the activity-based probe Desthiobiotin-FP in order to identify its putative target(s). This approach, combined with mass spectrometry, identified 18 potential candidates, all being serine or cysteine enzymes involved in M. tb lipid metabolism and/or in cell wall biosynthesis. Among them, Ag85A, CaeA, TesA, KasA and MetA have been reported as essential for in vitro growth of M. tb and/or its survival and persistence inside macrophages. Overall, our findings support the assumption that OX derivatives may represent a novel class of multi-target inhibitors leading to the arrest of M. tb growth through a cumulative inhibition of a large number of Ser- and Cys-containing enzymes involved in various important physiological processes.