The slow dissociation rate of K-1602 contributes to the enhanced inhibitory activity of this novel alkyl-aryl-bearing fluoroketolide.

Ketolides belong to the latest generation of macrolides and are not only effective against macrolide susceptible bacterial strains but also against some macrolide resistant strains. Here we present data providing insights into the mechanism of action of K-1602, a novel alkyl-aryl-bearing fluoroketolide. According to our data, the K-1602 interacts with the ribosome as a one-step slow binding inhibitor, displaying an association rate constant equal to 0.28 x 10(4) M-1 s(-1) and a dissociation rate constant equal to 0.0025 min(-1). Both constants contribute to produce an overall inhibition constant K-i equal to 1.49 x 10(-8) M, which correlates very well with the superior activity of this compound when compared with many other ketolides or fluoroketolides.