Identification of inhibitors of bacterial enoyl-acyl carrier protein reductase.

The FabI-related enoyl-ACP reductase enzymes of bacteria meet many of the criteria for antibacterial targets. These enzymes are essential for the growth of several pathogenic species, have no significant mammalian homologs, catalyze a rate-limiting step in a vital macromolecular biosynthetic pathway, and are already the targets of antibacterials used in the clinic (isoniazid) and in consumer products (triclosan). The suitability of FabI as an antibiotic target is diminished somewhat by the discovery that many pathogens carry an alternate unrelated enoyl-ACP reductase (FabK) or both reductases. However, a key human pathogen, Staphylococcus aureus and its increasingly common drug-resistant derivative MRSA are sensitive to FabI inhibitors. Screening for inhibitors of this target has resulted in the identification of five chemical classes of potent inhibitors. In addition, analogs of triclosan with increased potency and with pro-drug features have been engineered. At least one of these classes of inhibitors has been optimized and tested in animals for pharmacokinetic properties and efficacy. Further development of one or more of these classes and further screening are expected to generate new FabI inhibitors for application in the clinic against drug-resistant S. aureus.