title: γ-H2AX foci formation as a pharmacodynamic marker of DNA damage produced by DNA cross-linking agents: results from 2 phase I clinical trials of SJG-136 (SG2000).
abstract: OBJECTIVE
  To evaluate γ-H2AX foci as a pharmacodynamic marker for DNA damage induced by DNA interstrand cross-linking drugs.
  
  
  METHODS
  γ-H2AX foci formation was validated preclinically in comparison with the Comet assay, and evaluated pharmacodynamically in two phase I studies of different dosing schedules of the novel cross-linking agent SJG-136 (SG2000).
  
  
  RESULTS
  The measurement of γ-H2AX foci in human fibroblasts and lymphocytes in vitro was more than 10-fold more sensitive than Comet assay measurement of cross-linking, with peak γ-H2AX response 24 hours after the peak of cross-linking. In lymphocytes from a phase I study (every three week schedule), γ-H2AX foci were detectable 1 hour following the end of administration, and in all patients, maximum response was observed at 24 hours. Significant levels of foci were still evident at days 8 and 15 consistent with the known persistence of the DNA damage produced by this agent. In two tumor biopsy samples, foci were detected 4 hours postinfusion with levels higher than in lymphocytes. Extensive foci formation was also observed before the third dose in cycle 1 in lymphocytes from a second phase I study (daily × 3 schedule). These foci also persisted with a significant level evident before the second cycle (day 21). An increased γ-H2AX response was observed during the second cycle consistent with a cumulative pharmacodynamic effect. No clear relationship between foci formation and administered drug dose was observed.
  
  
  CONCLUSIONS
  This is the first use of γ-H2AX as a pharmacodynamic response to a DNA cross-linking agent in a clinical trial setting.
authors.affiliation: CR-UK Drug-DNA Interactions Research Group, UCL Cancer Institute, Paul O'Gorman Building, Huntley Street, London, United Kingdom.
authors.forename: Jenny
authors.initials: J
authors.lastname: Wu
authors.forename: Peter H
authors.initials: PH
authors.lastname: Clingen
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Spanswick
authors.forename: Maria
authors.initials: M
authors.lastname: Mellinas-Gomez
authors.forename: Tim
authors.initials: T
authors.lastname: Meyer
authors.forename: Igor
authors.initials: I
authors.lastname: Puzanov
authors.forename: Duncan
authors.initials: D
authors.lastname: Jodrell
authors.forename: Daniel
authors.initials: D
authors.lastname: Hochhauser
authors.forename: John A
authors.initials: JA
authors.lastname: Hartley
mesh_terms: D001570:Benzodiazepinones / Q000494:pharmacology*; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D010597:Pharmacogenetics; D011758:Pyrroles / Q000494:pharmacology*
chemical_list: C423343:1,1'-((propane-1,3-diyl)dioxy)bis(7-methoxy-2-methylidene-1,2,3,10,11,11a-hexahydro-5H-pyrrolo(2,1-c)(1,4)benzodiazepin-5,11-dione); D001570:Benzodiazepinones; C468783:H2AX protein, human; D006657:Histones; D011758:Pyrroles