In vitro activity: By targeting decaprenylphosphoryl-β-D-ribose 2'-epimerase, BTZ043 abolishes the formation of decaprenylphosphoryl arabinose, leading to cell lysis and death of Mycobacterium tuberculosis. BTZ043 displays similar activity against all clinical isolates of M. tuberculosis, including multidrug-resistant and extensively drug-resistant strains. BTZ043 displays significant activity against M. tuberculosis H37Rv and Mycobacterium smegmatis with MIC of 1 ng/mL (2.3 nM) and 4 ng/mL (9.2 nM), respectively, which is more potent than those of the existing tuberculosis (TB) drugs isoniazid (INH) and ethambutol (EMB) with MIC of 0.02-0.2 μg/mL and 1-5 μg/mL, respectively. BTZ043 is less effective in two different model systems (auxotrophy and starvation) involving metabolically inert M. tuberculosis, indicating that BTZ043 blocks a step in active metabolism similar to isoniazid (INH). BTZ043 treatment in M. smegmatis cells decreases the growth rate rapidly followed by a swelling of the poles and lysis of the cells after a few hours, which is similar but delayed in M. tuberculosis. BTZ043 (1/4 MIC 0.375 ng/mL) in combination with TMC207 (1/4 MIC 20 ng/mL) has a stronger cidal effect on M. tuberculosis but not BTZ-resistant M. tuberculosis mutant than TMC207 alone at a concentration of 80 ng/mL.

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: BTZ043 displayed similar activity against all clinical isolates of M. tuberculosis that were tested, including extensively drug-resistant and multidrug-resistant strains, indicating that it targets a previously unknown biological function. BTZ043 is bactericidal, reducing viability in vitro by more than 1000-fold in under 72 hours, which is comparable to the INH killing effect.