In Vivo Mammalian Alkaline Comet Assay (OECD 489)

Additional Support and Regulatory Follow-Up

When standard genetic toxicology assays return positive results, additional assays may be required to determine mechanism of action and qualify human risk.

  • The comet assay, also known as the single-cell gel electrophoresis (SCGE) assay, measures DNA strand breaks in individual cells.
  • Appropriate tissues are collected and processed to a single-cell suspension layered over a slide in a thin film of agarose.
  • Electrophoresis is then performed to identify DNA damage by the migration of small fragments of broken DNA away from the nucleus forming a “tail” to the dense circular comet head of undamaged DNA.
  • Testing is available for blood, liver, kidney, lung, bronchoalveolar lavage cells, stomach, duodenum, intestine, bone marrow, nose and eye.
    • New tissues can be validated upon request.

When to Perform

  • IND-enabling studies
    • As part of the ICH S2(R1) standard battery (Option 2)
    • As a follow-up to a positive in vitro mammalian cell clastogenic response
  • REACH requirements
    • As a follow-up to a positive result in an Annex VII or VIII genotoxicity test

Comet quantification on liver cell of rat treated with ethyl methanesulfonate
Figure: Comet quantification on liver cell of rat treated with ethyl methanesulfonate

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