Identification\nof an Isoxazole Derivative as an Antitubercular\nCompound for Targeting the FadD Enzymes of Mycobacterium\ntuberculosis

FadD32,\na fatty acyl-AMP ligase, plays an indispensable role in\nmycobacterial mycolic acid synthesis and is a validated target for\ntuberculosis (TB) drug development. The crystal structure of Mycobacterium tuberculosis (Mtb)FadD32 has laid the\nfoundation of structure-based drug discovery against this crucial\nenzyme. Here, we screened the “isoxazole” scaffold containing\nmolecules against MtbFadD32 and identified a compound 2,4-dibromo-6-[3-(trifluoromethyl)-1,2-oxazol-5-yl]phenol\n(M1) with specific inhibitory activity against Mtb. Kinetics experiments\nshowed that M1 inhibits MtbFadD32 and MtbFadD28 activity. The transcriptomics\nresponse of Mtb disclosed M1-mediated regulation of mycobacterial\ndecisive genes involved in cell wall synthesis, consequently creating\nunfavorable conditions for Mtb survival. Further, M1 curtails the\nMtb survival in infected macrophages and reduces Mtb burden and tubercular\ngranulomas in a chronic infection model of BALB/c mice. Our findings\nprovide an effective chemical scaffold to inhibit MtbFadD32 with the\npotential to inhibit multiple MtbFadD family of enzymes for further\ndevelopment as a promising candidate for treating TB.