Preclinical evaluation of the pharmacodynamic properties of 2,5-diaziridinyl-3-hydroxymethyl-6-methyl-1,4-benzoquinone.
OBJECTIVE
The purpose of our study was to investigate the cellular accumulation, DNA cross-linking ability, and cellular toxicity of RH1 (2,5-diaziridinyl-3-[hydroxymethyl[-6-methyl-1,4-benzoquinone), a novel DNA alkylating agent currently in clinical trials. In addition, the in vivo efficacy of RH1 formulated in different vehicles was also compared.


METHODS
RH1 is activated by the two-electron reducing enzyme NQO1 [NADPH:quinone oxidoreductase] forming a potent cytotoxic agent that cross-links DNA. We have used whole blood, cell lines, and primary explanted tumor cultures to measure both the cellular accumulation, DNA cross-linking, and cytotoxicity of RH1. Furthermore, the pharmacokinetic and pharmacodynamic characteristics of RH1 formulated in different vehicles were measured in vivo using the validated comet-X assay in mice bearing human tumor xenografts.


RESULTS
Accumulation of RH1 was shown to be both time and concentration dependent, reaching a maximum after 2 hours and correlated well with DNA cross-linking measurements. DNA cross-linking in vitro could be detected at low (1-10 nmol/L) concentrations after as little as 2 hours exposure. In primary tumor cultures, RH1 induces much higher levels of DNA cross-links at lower doses than either mitomycin C or cisplatin. In vivo efficacy testing using polyvinyl pyrrolidone, saline, or cyclodextrin as vehicles showed DNA cross-links readily detectable in all tissues examined and was enhanced when given in cyclodextrin compared with polyvinyl pyrrolidone or saline.


CONCLUSIONS
RH1 represents a potent bioreductive anticancer drug, which may prove effective in the treatment of cancers, particularly those that overexpress NQO1. DNA cross-linking can be reliably measured in tissue using the validated comet-X assay.
Ward
Timothy H
TH
Clinical and Experimental Pharmacology Group, Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK. tward@picr.man.ac.uk
Danson
Sarah
S
McGown
Alan T
AT
Ranson
Malcolm
M
Coe
Nic A
NA
Jayson
Gordon C
GC
Cummings
Jeff
J
Hargreaves
Robert H J
RH
Butler
John
J
D000818:Animals; D001388:Aziridines / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D016227:Benzoquinones / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D020552:Comet Assay / Q000379:methods; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005260:Female; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D016896:Treatment Outcome; D014316:Tritium; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
C117776:2,5-diaziridinyl-3-(hydroxymethyl)-6-methyl-1,4-benzoquinone; D001388:Aziridines; D016227:Benzoquinones; D003432:Cross-Linking Reagents; D014316:Tritium; D004247:DNA