In Vivo Rodent Micronucleus Test (OECD 474)

Screening and Regulatory Support

  • The micronucleus test (MNT) is used to determine if a compound is genotoxic by evaluating the presence of micronuclei.
    • Micronuclei may contain chromosome fragments produced from DNA breakage (clastogens) or whole chromosomes produced by disruption of the mitotic apparatus (aneugens).
  • Male and/or female rats or mice are treated with the test compound at three dose levels, usually two or three times at 24-hour intervals.
  • Approximately 24 hours after the last dose, bone marrow or peripheral blood is collected to determine the frequency of micronucleated polychromatic erythrocytes (MN-PCEs) or micronucleated reticulocytes (MN-RETs), respectively.
  • A positive outcome is characterized by a statistically significant, dose-dependent increase in MN-PCEs or MN-RETs that exceeds historical control limits.
  • Can be combined with standard toxicology tests, the comet assay and the Pig-a assay.
  • Administration routes include: oral, intravenous, infusion and inhalation
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When to Perform

  • Screening
    • Abbreviated formats available or can be added to non-GLP tolerability studies
  • IND-enabling
    • As part of the ICH S2(R1) standard battery (Option 1 or 2)
  • REACH requirement
    • To follow up a positive result in any of the Annex VII or VIII genotoxicity tests

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