In vitro activity: BTZ043, also known as 8-Nitro-benzothiazinones (BTZs), is a potent inhibitor of decaprenyl-phosphoribose-epimerase (DprE1) with MIC values of of 2.3 nM and 9.2 nM for M. tuberculosis H37Rv and Mycobacterium smegmatis, respectively. It can display nanomolar bactericidal activity against Mycobacterium tuberculosis in vitro. The inhibition of BTZ-resistant DprE1 followed the trend observed in the MIC measurements, with the C387G mutant being more resistant to inhibition by PyrBTZ01, PyrBTZ02, and BTZ043 (7- to 9-fold increases in IC50) than the C387S mutant (2.5- to 4-fold increases in IC50). Structure-activity relationship (SAR) studies revealed the 8-nitro group of the BTZ scaffold to be crucial for the mechanism of action, which involves formation of a semimercaptal bond with Cys387 in the active site of DprE1. BTZ043 presented favorable in vitro absorption-distribution-metabolism-excretion/toxicity (ADME/T) and in vivo pharmacokinetic profiles. BTZ043 did not show efficacy in a mouse model of acute tuberculosis, suggesting that BTZ-mediated killing through DprE1 inhibition requires a combination of both covalent bond formation and compound potency.

Kinase Assay: BTZ043, also known as 8-Nitro-benzothiazinones (BTZs), is a potent inhibitor of decaprenyl-phosphoribose-epimerase (DprE1) with MIC values of of 2.3 nM and 9.2 nM for M. tuberculosis H37Rv and Mycobacterium smegmatis, respectively.

Cell Assay: The MIC of BTZ043 against M. tuberculosis H37Rv and Mycobacterium smegmatis are 1 ng/mL (2.3 nM) and 4 ng/mL (9.2 nM), respectively. The in vitro activity of BTZ043 against 30 Nocardia brasiliensis isolates is also tested. The MIC50 and MIC90 values for BTZ043 are 0.125 and 0.25 μg/mL. The MIC for N. carnea ATCC 6847 is 0.003μg/mL, for N. transvalensis ATCC 6865 is 0.003μg/mL, for N. brasiliensis NCTC10300 is 0.03 μg/mL, and for N. brasiliensis HUJEG-1 is 0.125μg/mL. The MIC value for M. tuberculosis H37Rv is 0.000976 μg/mL. The MIC value of BTZ-043 is>64 μg/mL for Escherichia coli ATCC 25922 and S. aureus ATCC 2921.