Development and Evaluation of Bis-benzothiazoles as a New Class of Benzothiazoles Targeting DprE1 as Antitubercular Agents.

Benzothiazole-bearing compounds have emerged as potential noncovalent DprE1 (decaprenylphosphoryl-β-d-ribose-2'-epimerase) inhibitors active against . Based on structure-based virtual screening (PDB ID: 4KW5), a focused library of thirty-one skeletally diverse benzothiazole amides was prepared, and the compounds were assessed for their antitubercular activity against H37Ra. Most potent compounds and were further evaluated against the H37Rv strain by the microdilution assay method. Among the compounds evaluated, bisbenzothiazole amide emerged as a hit molecule and demonstrated promising antitubercular activity with minimum inhibitory concentration (MIC) values of 0.45 μg/mL and 8.0 μg/mL against HRa and HRv, respectively. Based on the preliminary hit molecule (, a focused library of 12 more bis-benzothiazole amide derivatives was further prepared by varying the substituents on either side to obtain new leads and generate a structure-activity relationship (SAR). Among these compounds, , and demonstrated remarkable antitubercular activity with MIC values of 0.5 μg/mL against H37Ra and 1.0, 2.0, and 8.0 μg/mL against HRv, respectively. The most active compound, , also displayed significant efficacy against four drug-resistant tuberculosis strains. Compound was assessed for cytotoxicity against the HepG2 cell line, and it displayed insignificant cytotoxicity. Furthermore, time-kill kinetic studies demonstrated time- and dose-dependent bactericidal activity of this compound. The GFP release assay revealed that compound targets the inhibition of a cell wall component. SNPs in gene assessment revealed that compound binds to tyrosine at position 314 of DprE1 and replaces it with histidine, causing resistance similar to that of standard TCA1. docking studies further suggest that the strong noncovalent interactions of these compounds may lead to the development of potent noncovalent DprE1 inhibitors.