Chemical exploration of a highly selective scaffold with activity against intracellular Mycobacterium tuberculosis

We previously identified a phenylthiourea series with activity against intracellular Mycobacterium tuberculosis using a high throughput, high content assay. We conducted a catalog structure-activity relationship study with a collection of 35 analogs. We identified several thiourea derivatives with excellent potency against intracellular bacteria and good selectivity over eukaryotic cells. Compounds had much lower activity against extracellular bacteria which was not increased by using cholesterol as the sole carbon source. Compounds were equally active against strains with mutations in QcrB or MmpL3, thereby excluding common, promiscuous targets as the mode of action. The phenylthiourea series represents a good starting point for further exploration to develop novel anti-tubercular agents.