When is a Genotoxin not a Genotoxin?



May 1, 2012

Richard Walmsley, Professor University of Manchester and Gentronix Ltd

The in vitro genotoxicity tests were conceived to predict carcinogenicity in novel chemicals. The reality is more complex: a reproducibly positive in vitro genotoxicity result does not necessarily imply a human cancer hazard, and need not signal the end of a compound's development. There are many different reasons for this, aside from the more obvious examples of genotoxic drugs designed for life-threatening cancers. There are positive results which might be peculiar to a particular test system; there might be metabolites that are specific to rodent S9; there might be genotoxic intermediates in synthesis, breakdown products or other impurities which can avoided or excluded; the positive result might only be evident in the highest toxic dose reachable for a compound where exposure will be at trace levels; a compound showing a wider genotoxic dose response might show a clear threshold effect, such that low doses are entirely safe. This talk will consider some examples of non-concerning genotoxicity, with reference to some commonly used in vitro genotoxicity screening assays.

Drug DiscoveryGenomicsInformatics

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