title: Mechanism of action of NB2001 and NB2030, novel antibacterial agents activated by beta-lactamases.
abstract: Two potent antibacterial agents designed to undergo enzyme-catalyzed therapeutic activation were evaluated for their mechanisms of action. The compounds, NB2001 and NB2030, contain a cephalosporin with a thienyl (NB2001) or a tetrazole (NB2030) ring at the C-7 position and are linked to the antibacterial triclosan at the C-3 position. The compounds exploit beta-lactamases to release triclosan through hydrolysis of the beta-lactam ring. Like cephalothin, NB2001 and NB2030 were hydrolyzed by class A beta-lactamases (Escherichia coli TEM-1 and, to a lesser degree, Staphylococcus aureus PC1) and class C beta-lactamases (Enterobacter cloacae P99 and E. coli AmpC) with comparable catalytic efficiencies (k(cat)/K(m)). They also bound to the penicillin-binding proteins of S. aureus and E. coli, but with reduced affinities relative to that of cephalothin. Accordingly, they produced a cell morphology in E. coli consistent with the toxophore rather than the beta-lactam being responsible for antibacterial activity. In biochemical assays, they inhibited the triclosan target enoyl reductase (FabI), with 50% inhibitory concentrations being markedly reduced relative to that of free triclosan. The transport of NB2001, NB2030, and triclosan was rapid, with significant accumulation of triclosan in both S. aureus and E. coli. Taken together, the results suggest that NB2001 and NB2030 act primarily as triclosan prodrugs in S. aureus and E. coli.
authors.affiliation: NewBiotics, Inc., San Diego, California 92121, USA. gstone@ucsd.edu
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Stone
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhang
authors.forename: Rosario
authors.initials: R
authors.lastname: Castillo
authors.forename: V Ramana
authors.initials: VR
authors.lastname: Doppalapudi
authors.forename: Analia R
authors.initials: AR
authors.lastname: Bueno
authors.forename: Jean Y
authors.initials: JY
authors.lastname: Lee
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Maria
authors.initials: M
authors.lastname: Sergeeva
authors.forename: Gody
authors.initials: G
authors.lastname: Khambatta
authors.forename: Nafsika H
authors.initials: NH
authors.lastname: Georgopapadakou
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D001711:Biotransformation; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002511:Cephalosporins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D003001:Cloning, Molecular; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D054889:Fatty Acid Synthase, Type II; D006602:Hexosyltransferases / Q000378:metabolism; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D013777:Tetrazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D014260:Triclosan / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002511:Cephalosporins; D029968:Escherichia coli Proteins; C461664:NB 2001; C482454:NB 2030; D046915:Penicillin-Binding Proteins; D013777:Tetrazoles; D014260:Triclosan; D010088:Oxidoreductases; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); C493924:fabI protein, E coli; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D001618:beta-Lactamases; D054889:Fatty Acid Synthase, Type II