Michael Otteneder

Novel Bacterial Acetyl Coenzyme A Carboxylase Inhibitors with Antibiotic Efficacy In Vivo

ABSTRACT The pseudopeptide pyrrolidinedione antibiotics, such as moiramide B, have recently been discovered to target the multisubunit acetyl coenzyme A (acetyl-CoA) carboxylases of bacteria. In this paper, we describe synthetic variations of each moiety of the modularly composed pyrrolidinediones, providing insight into structure-activity relationships of biochemical target activity, in vitro potency, and in vivo efficacy. The novel derivatives showed highly improved activities against gram-positive bacteria compared to those of previously reported variants. The compounds exhibited a MIC90 value of 0.1 μg/ml against a broad spectrum of Staphylococcus aureus clinical isolates. No cross-resistance to antibiotics currently used in clinical practice was observed. Resistance mutations induced by pyrrolidinediones are exclusively located in the carboxyltransferase subunits of the bacterial acetyl-CoA carboxylase, indicating the identical mechanisms of action of all derivatives tested. Improvement of the physicochemical profile was achieved by salt formation, leading to aqueous solubilities of up to 5 g/liter. For the first time, the in vitro activity of this compound class was compared with its in vivo efficacy, demonstrating a path from compounds weakly active in vivo to agents with significant efficacy. In a murine model of S. aureus sepsis, the 100% effective dose of the best compound reported was 25 mg/kg of body weight, only fourfold higher than that of the comparator molecule linezolid. The obvious improvements achieved by chemical derivatization reflect the potential of this novel antibiotic compound class for future therapy.

Biological Characterization of Novel Inhibitors of the Gram-Positive DNA Polymerase IIIC Enzyme

ABSTRACT Novel N-3-alkylated 6-anilinouracils have been identified as potent and selective inhibitors of bacterial DNA polymerase IIIC, the enzyme essential for the replication of chromosomal DNA in gram-positive bacteria. A nonradioactive assay measuring the enzymatic activity of the DNA polymerase IIIC in gram-positive bacteria has been assembled. The 6-anilinouracils described inhibited the polymerase IIIC enzyme at concentrations in the nanomolar range in this assay and displayed good in vitro activity (according to their MICs) against staphylococci, streptococci, and enterococci. The MICs of the most potent derivatives were about 4 μg/ml for this panel of bacteria. The 50% effective dose of the best compound (6-[(3-ethyl-4-methylphenyl)amino]-3-{[1-(isoxazol-5-ylcarbonyl)piperidin-4-yl]methyl}uracil) was 10 mg/kg of body weight after intravenous application in a staphylococcal sepsis model in mice, from which in vivo pharmacokinetic data were also acquired.