title: Biological profiling of novel tricyclic inhibitors of bacterial DNA gyrase and topoisomerase IV.
abstract: The objective of this study was to characterize the in vitro and in vivo biological properties of a novel series of small-molecule bacterial type IIA topoisomerase inhibitors.
  
  
  
  Bacterial susceptibility testing was performed by broth microdilution. Resistance frequencies were determined by plating bacteria onto agar containing test compound and enumerating mutants. Bacteria were passaged using subinhibitory concentrations of antibacterials to generate resistance. Target enzyme inhibition was determined by exposure to antibacterials and DNA; topoisomers were visualized by gel electrophoresis. Oral and intravenous pharmacokinetic profiles were determined in mice. In vivo efficacy was determined using a mouse model of septicaemia and thigh infection with MSSA and MRSA, respectively.
  
  
  
  Representative compounds REDX04139, REDX05604 and REDX05931 demonstrated in vitro potency against a range of Gram-positive and fastidious Gram-negative pathogens. Clinical isolate testing revealed REDX04139 and REDX05931 had MIC90 values of 0.25 and 0.5 mg/L, respectively, for MRSA and MIC90 values of 2 mg/L for streptococci. REDX04139 was bactericidal in vitro against Staphylococcus aureus at 8× MIC over 6 h. Pharmacokinetic profiling of REDX04139 and REDX05604 in mice revealed low clearance and excellent bioavailability (≥71%). REDX04139 provided 100% survival against S. aureus in a mouse septicaemia model, while REDX05604 reduced bacterial load by up to 3.7 log units in the MRSA mouse thigh infection model.
  
  
  
  Redx Pharma has discovered a novel series of topoisomerase inhibitors that are being further developed for drug-resistant bacteria.
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK v.savage@redxpharma.com.
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Savage
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Cédric
authors.initials: C
authors.lastname: Charrier
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Salisbury
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Moyo
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Henry
authors.initials: H
authors.lastname: Forward
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Nathan
authors.initials: N
authors.lastname: Chaffer-Malam
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Metzger
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Huxley
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Ralph
authors.initials: R
authors.lastname: Kirk
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Mario
authors.initials: M
authors.lastname: Uosis-Martin
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Gary
authors.initials: G
authors.lastname: Noonan
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Sarfraz
authors.initials: S
authors.lastname: Mohmed
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Best
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ratcliffe
authors.affiliation: Redx Pharma, BioHub, Alderley Park, Cheshire SK10 4TG, UK.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Stokes
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000494:pharmacology*; D001682:Biological Availability; D002470:Cell Survival / Q000187:drug effects; D027081:DNA Gyrase / Q000378:metabolism*; D027101:DNA Topoisomerase IV / Q000037:antagonists & inhibitors*; D004195:Disease Models, Animal; D056945:Hep G2 Cells; D006801:Humans; D006844:Hydrocarbons, Cyclic / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D018805:Sepsis / Q000188:drug therapy / Q000382:microbiology; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013210:Staphylococcus / Q000187:drug effects*; D013291:Streptococcus / Q000187:drug effects; D016019:Survival Analysis
chemical_list: D000900:Anti-Bacterial Agents; D006844:Hydrocarbons, Cyclic; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase