Rifalazil is a rifamycin derivative, inhibits the bacterial DNA-dependent RNA polymerase and kills bacterial cells by blocking off the β-subunit in RNA polymerase. Rifalazil is an antibiotic, exhibits high potency against mycobacteria, gram-positive bacteria, Helicobacter pylori, C. pneumoniae and C. trachomatis (MIC: 0.00025 to 0.0025 μg/ml).

Rifalazil demonstrates antimicrobial (antimicrobal) activity against a broad spectrum of bacteria, effectively inhibiting various strains. Against Gram-positive enteric bacteria, it is potent, with minimum inhibitory concentrations (MIC50) for Clostridium difficile, Clostridium perfringens, and Bacteroides fragilis at 0.0015, 0.0039, and 0.0313 µg/ml, respectively. In combating Gram-negative enteric pathogens, it hampers the growth of Escherichia coli and Klebsiella pneumoniae, each with an MIC50 value of 16 µg/ml. Moreover, Rifalazil is efficacious against non-enteric Gram-positive bacteria, including various strains of Staphylococcus aureus (Methicillin-susceptible, Methicillin-resistant, and Methicillin- and quinolone-resistant), Staphylococcus epidermidis, Streptococcus pyogenes, and Streptococcus pneumoniae, with MIC50 values ranging from 0.0001 to 0.0078 µg/ml. Furthermore, it shows activity against Helicobacter pylori, Chlamydia pneumoniae, and Chlamydia trachomatis, with MIC50 values of 0.004, 0.000125, and 0.00025 µg/ml, respectively[3].

Rifalazil (p.o.; 20, 25, and 150 mg/kg; 6-8 weeks) combines with isoniazid for 6 weeks or greater significantly reduced the number of mice per group in which?M. tuberculosis?is detected in both spleens and lungs compared to the reductions for the early and late controls [2].