Identification of 2-amino benzothiazoles with bactericidal activity against Mycobacterium tuberculosis
We identified an amino-benzothiazole scaffold from a whole cell screen against recombinant Mycobacterium tuberculosis under expressing the essential signal peptidase LepB. The seed molecule had two-fold higher activity against the LepB hypomorph. Through a combination of purchase and chemical synthesis we explored the structure activity relationship for this series; 34 analogs were tested for anti-tubercular activity and for cytotoxicity against eukaryotic cells. We identified molecules with improved potency and reduced cytotoxicity. However, molecules did not appear to target LepB directly and did not inhibit protein secretion. Key compounds showed good permeability, low protein binding, and lack of CYP inhibition, but metabolic stability was poor with short half-lives. The seed molecule showed good bactericidal activity against both replicating and non-replicating bacteria, as well as potency against intracellular M. tuberculosis in murine macrophages. Overall, the microbiological properties of the series are attractive if metabolic stability can be improved, and identification of the target could assist in development of this series.