title: OP0595, a new diazabicyclooctane: mode of action as a serine β-lactamase inhibitor, antibiotic and β-lactam 'enhancer'.
abstract: OBJECTIVE
  The production of a growing diversity of β-lactamases by Gram-negative bacteria challenges antimicrobial chemotherapy. OP0595, discovered separately by each of Meiji Seika Pharma and Fedora Pharmaceuticals, is a new diazabicyclooctane serine β-lactamase inhibitor that also acts as an antibiotic and as a β-lactamase-independent β-lactam 'enhancer'.
  
  
  METHODS
  Inhibitory activity against serine β-lactamases and affinity for PBPs were determined using nitrocefin and Bocillin FL, respectively. MICs alone and in combination with β-lactam agents were measured according to CLSI recommendations. Morphological changes in Escherichia coli were examined by phase-contrast microscopy.
  
  
  RESULTS
  IC50s of OP0595 for class A and C β-lactamases were <1000 nM, with covalent binding demonstrated to the active-site serine of CTX-M-44 and AmpC enzymes. OP0595 also had direct antibiotic activity against many Enterobacteriaceae, associated with inhibition of PBP2 and conversion of the bacteria into spherical forms. Synergy between OP0595 and β-lactam agents was seen against strains producing class A and C β-lactamases vulnerable to inhibition. Lastly, OP0595 lowered the MICs of PBP3-targeted partner β-lactam agents for a non-β-lactamase-producing E. coli mutant that was resistant to OP0595 itself, indicating β-lactamase-independent 'enhancer'-based synergy.
  
  
  CONCLUSIONS
  OP0595 acts in three ways: (i) as an inhibitor of class A and C β-lactamases, covalently binding at their active sites; (ii) as an antibacterial, by inhibiting PBP2 of several Enterobacteriaceae; and (iii) as an 'enhancer' of β-lactam agents that bind to other PBPs besides PBP2 for several Enterobacteriaceae. OP0595 has considerable potential to overcome resistance when it is combined with various β-lactam agents.
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan akihiro.morinaka@meiji.com.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Morinaka
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tsutsumi
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Mototsugu
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Abe
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Furuuchi
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Inamura
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Sakamaki
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Nakako
authors.initials: N
authors.lastname: Mitsuhashi
authors.affiliation: Meiji Seika Pharma Co., Ltd, Yokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ida
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: David M
authors.initials: DM
authors.lastname: Livermore
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D053961:Azabicyclo Compounds / Q000737:chemistry / Q000494:pharmacology*; D020134:Catalytic Domain; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D006801:Humans; D006860:Hydrogen Bonding; D020128:Inhibitory Concentration 50; D007769:Lactams / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008968:Molecular Conformation; D065093:beta-Lactamase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D001618:beta-Lactamases / Q000737:chemistry / Q000378:metabolism; D047090:beta-Lactams / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D053961:Azabicyclo Compounds; D007769:Lactams; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; C000608518:nacubactam; D001618:beta-Lactamases