The discovery of new antibacterial agents with novel mechanisms of action is necessary to overcome the problem of bacterial resistance that affects all currently used classes of antibiotics. Bacterial DNA gyrase and topoisomerase IV are well-characterized clinically validated targets of the fluoroquinolone antibiotics which exert their antibacterial activity through inhibition of the catalytic subunits. Inhibition of these targets through interaction with their ATP sites has been less clinically successful. The discovery and characterization of a new class of low molecular weight, synthetic inhibitors of gyrase and topoisomerase IV that bind to the ATP sites are presented. The benzimidazole ureas are dual targeting inhibitors of both enzymes and possess potent antibacterial activity against a wide spectrum of relevant pathogens responsible for hospital- and community-acquired infections. The discovery and optimization of this novel class of antibacterials by the use of structure-guided design, modeling, and structure-activity relationships are described. Data are presented for enzyme inhibition, antibacterial activity, and in vivo efficacy by oral and intravenous administration in two rodent infection models.

No abstract

We have synthesized a series of non-macrocyclic ligands to FKBP12 that are comparable in binding potency and peptidyl prolyl isomerase (PPIase) inhibition to FK506 itself. We have also solved the structure of one of these ligands in complex with FKBP12, and have compared that structure to the FK506-FKBP 12 complex. Consistent with the observed inhibitory equipotency of these compounds, we observe a strong similarity in the conformation of the two ligands in the region of the protein that mediates PPIase activity. Our compounds, however, are not immunosuppressive. In the FKBP12-FK506 complex, a significant portion of the FK506 ligand, its 'effector domain', projects beyond the envelope of the binding protein in a manner that is suggestive of a potential interaction with a second protein, the calcium-dependent phosphatase, calcineurin, whose inhibition by the FKBP 12-FK506 complex interrupts the T-cell activation events leading to immunosuppression. In contrast, our compounds bind within the surface envelope of FKBP12, and induce significant changes in the structure of the FKBP12 protein which may also affect calcineurin binding indirectly.

No abstract