Microbiology Congress 2018: Identification of inhibitors of the anti-infective target DXS using ligand-based virtual screening - Adel Elmekes - Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)

The enzymes of the methylerythritol phosphate (MEP) pathway are important drug targets given that pathogens such as Mycobacterium tuberculosis and Plasmodium falciparum use this pathway for the biosynthesis of the essential isoprenoid precursor’s isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), while humans exclusively utilize an alternative pathway. The thiamine-diphosphate-dependent enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXS) catalyzes the first and rate-limiting step of the MEP pathway. To expand the structural diversity and obtain potent and selective inhibitors of DXS, we performed a ligand-based virtual screening (LBVS) campaign based on shape similarity to screen the ZINC database, starting from previously discovered DXS inhibitors as references. Biochemical evaluation of the top-scoring compounds against Mycobacterium tuberculosis DXS and further rounds of LBVS using the best hits as references afforded inhibitors in the single-digit micro molar range. In addition to the promising biochemical activity, the hits are active in cell based assays against Plasmodium falciparum and even drug-resistant strains of Mycobacterium tuberculosis. Further, assays demonstrated their selectivity over mammalian thiamine-diphosphate-dependent enzymes, their lack of cytotoxicity and validated DXS as the intracellular target.