title: Pharmacodynamics of RWJ-54428 against Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis in a neutropenic mouse thigh infection model.
abstract: RWJ-54428 (also known as MC-02,479) is a new cephalosporin with promising activity against gram-positive bacteria. The pharmacodynamics (PDs) of RWJ-54428 against Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis were studied in a neutropenic mouse thigh infection model. The RWJ-54428 MICs ranged from 0.25 to 1 mg/liter. Mice with ca. 10(6) CFU/thigh at the initiation of therapy were treated intraperitoneally with RWJ-54428 at doses that ranged from 3 to 1,200 mg/kg of body weight/day (in 2, 3, 4, 6, or 12 divided doses) for 24 h. The maximal reductions in bacterial counts in thigh tissues at 24 h for the methicillin-resistant S. aureus, penicillin-resistant S. pneumoniae, and E. faecalis strains were -2.8, -3.8, and -1.7 log10 CFU/thigh, respectively. The percentage of a 24-h dosing interval that the unbound serum RWJ-54428 concentrations exceeded the MIC (fT>MIC) was the pharmacokinetic (PK)-PD parameter that best described the efficacy of RWJ-54428. The fT>MICs for a bacteriostatic effect (no net change in the numbers of CFU/thigh over 24 h) ranged from 14 to 20% for staphylococci and streptococci; for maximal reductions in the numbers of CFU/thigh, the fT>MICs ranged from 22 to 36% for these strains. For E. faecalis, the ranges of fT>MICs for static and maximal effects were 30 to 46% and 55 to 60%, respectively. These data show that treatment with RWJ-54428 results in marked antibacterial effects in vivo, with the PK-PD parameters for efficacy being comparable to those for the efficacy of penicillins and carbapenems active against staphylococci and pneumococci.
authors.affiliation: Microcide Pharmaceuticals, Inc. Mountain View, CA 94043. dgriffith@mpexpharma.com
authors.forename: David C
authors.initials: DC
authors.lastname: Griffith
authors.forename: David
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Erik
authors.initials: E
authors.lastname: Corcoran
authors.forename: Michael N
authors.initials: MN
authors.lastname: Dudley
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D002511:Cephalosporins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D004195:Disease Models, Animal; D013293:Enterococcus faecalis / Q000187:drug effects; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy* / Q000382:microbiology; D006095:Gram-Positive Cocci / Q000187:drug effects*; D006801:Humans; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D009503:Neutropenia / Q000150:complications* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects; D013296:Streptococcus pneumoniae / Q000187:drug effects; D013848:Thigh / Q000382:microbiology; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; C420727:RWJ 54428