CG400462, a novel FabI inhibitor, has a potent antibacterial activity against staphylococci. The minimal inhibitory concentration at which 90% of bacterial strains tested were inhibited (MIC(90)) of CG400462 was 0.5 microg/mL against 238 strains of Staphylococcus aureus and 1.0 microg/mL against 51 strains of coagulase-negative staphylococci, irrespective of whether the strains were methicillin-susceptible or -resistant. CG400462 was also effective by subcutaneous administration against systemic infections in mice. In time-kill studies, CG400462 at concentrations of 1x, 2x and 4x MIC had a bacteriostatic activity over 24h. Genetic approaches have confirmed that the mode of action of CG400462 is via inhibition of FabI, which is involved in the biosynthesis of fatty acids in bacteria. Study of the resistance mechanism of S. aureus showed that CG400462-resistant mutants had an alteration in FabI of Met99-->Thr or Tyr147-->His.