In vitro activity: In vitro, PA-824 exhibits the high activity against multidrug-resistant clinical isolates from Asia (India and South Korea) and from throughout the United States (MIC < 1 μg/ml) and is equally active against the drug-sensitive and multidrug-resistant isolates of M. tuberculosis (MICs range, 0.039 to 0.531 μg/ml). A recent study shows that single-nucleotide polymorphisms of PA-824 resistance genes (fgd1 [Rv0407] and ddn [Rv3547]) don't significantly affect the PA-824 MICs (≤ 0.25 μg/ml).

Kinase Assay: Pretomanid (PA-824) is a small-molecule nitroimidazopyran drug candidate for the treatment of tuberculosis; the MIC values of PA-824 against a panel of MTB pan-sensitive and rifampin mono-resistant clinical isolates ranged from 0.015 to 0.25 ug/ml. IC50 value: 0.015 to 0.25 ug/ml (MICs).

Cell Assay: A method is used to determine the MICs by a microdilution plate assay by using M. tuberculosis H37Rv. INH is dissolved in sterile, double-distilled water at a stock concentration of 500 μg/ml. PA-824 is dissolved in 100% dimethyl sulfoxide (DMSO) to a stock concentration of 100 μg/ml. A 1:2 dilution series of both compounds is made in a separate 96-well microtiter plate by using the same diluents. The interior 60 wells of a 96-well round-bottom microtiter assay plate are seeded with 98 μl of bacterial suspension. Two microliters of each drug is transferred to the assay plate wells containing bacteria. The final concentrations of INH in the wells range from 10.0 to 0.039 μg/mL; the final concentrations of PA-824 range from 2.0 μg/mL to 8.0 pg/mL. The assay plates are incubated at 37 °C for at least 21 days and are observed every 3 to 4 days to evaluate changes in growth. Inhibition of growth is determined both by visual examination and with a spectrophotometer at an OD600.