title: RWJ-54428 (MC-02,479), a new cephalosporin with high affinity for penicillin-binding proteins, including PBP 2a, and stability to staphylococcal beta-lactamases.
abstract: RWJ-54428 (MC-02,479) is a new cephalosporin active against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The potency of this new cephalosporin against MRSA is related to a high affinity for penicillin-binding protein 2a (PBP 2a), as assessed in a competition assay using biotinylated ampicillin as the reporter molecule. RWJ-54428 had high activity against MRSA strains COL and 67-0 (MIC of 1 micro g/ml) and also showed affinity for PBP 2a, with a 50% inhibitory concentration (IC(50)) of 0.7 micro g/ml. RWJ-54428 also displayed excellent affinity for PBP 5 from Enterococcus hirae R40, with an IC(50) of 0.8 micro g/ml and a MIC of 0.5 micro g/ml. The affinity of RWJ-54428 for PBPs of beta-lactam-susceptible S. aureus (MSSA), enterococci (E. hirae), and Streptococcus pneumoniae showed that the good affinity of RWJ-54428 for MRSA PBP 2a and E. hirae PBP 5 does not compromise its binding to susceptible PBPs. RWJ-54428 showed stability to hydrolysis by purified type A beta-lactamase isolated from S. aureus PC1. In addition, RWJ-54428 displayed low MICs against strains of S. aureus bearing the four classes of staphylococcal beta-lactamases, including beta-lactamase hyperproducers. The frequency of isolation of resistant mutants to RWJ-54428 from MRSA strains was very low. In summary, RWJ-54428 has high affinity to multiple PBPs and is stable to beta-lactamase, properties that may explain our inability to find resistance by standard methods. These data are consistent with its excellent activity against beta-lactam-resistant gram-positive bacteria.
authors.affiliation: Essential Therapeutics, Inc., Mountain View, California 94043, USA.
authors.forename: Francois
authors.initials: F
authors.lastname: Malouin
authors.forename: Johanne
authors.initials: J
authors.lastname: Blais
authors.forename: Suzanne
authors.initials: S
authors.lastname: Chamberland
authors.forename: Monica
authors.initials: M
authors.lastname: Hoang
authors.forename: Craig
authors.initials: C
authors.lastname: Park
authors.forename: Christin
authors.initials: C
authors.lastname: Chan
authors.forename: Kristina
authors.initials: K
authors.lastname: Mathias
authors.forename: Samia
authors.initials: S
authors.lastname: Hakem
authors.forename: Kelly
authors.initials: K
authors.lastname: Dupree
authors.forename: Eric
authors.initials: E
authors.lastname: Liu
authors.forename: Tien
authors.initials: T
authors.lastname: Nguyen
authors.forename: Michael N
authors.initials: MN
authors.lastname: Dudley
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D016983:Enterococcus / Q000187:drug effects*; D006602:Hexosyltransferases; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D013211:Staphylococcus aureus / Q000187:drug effects*; D013296:Streptococcus pneumoniae / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002511:Cephalosporins; D046915:Penicillin-Binding Proteins; C420727:RWJ 54428; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase