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The EFSA Scientific Committee was asked to provide guidance on the most appropriate in vivo tests to follow up on positive in vitro results for aneugenicity, and on the approach to risk assessment for substances that are aneugenic but not clastogenic nor causing gene mutations. The Scientific Committee confirmed that the preferred approach is to perform an in vivo mammalian erythrocyte micronucleus test with a relevant route of administration. If this is positive, it demonstrates that the substance is aneugenic in vivo. A negative result with evidence that the bone marrow is exposed to the test substance supports a conclusion that aneugenic activity is not expressed in vivo. If there is no evidence of exposure to the bone marrow, a negative result is viewed as inconclusive and further studies are required. The liver micronucleus assay, even though not yet fully validated, can provide supporting information for substances that are aneugenic following metabolic activation. The gastrointestinal micronucleus test, conversely, to be further developed, may help to assess aneugenic potential at the initial site of contact for substances that are aneugenic in vitro without metabolic activation. Based on the evidence in relation to mechanisms of aneugenicity, the Scientific Committee concluded that, in principle, health‐based guidance values can be established for substances that are aneugenic but not clastogenic nor causing gene mutations, provided that a comprehensive toxicological database is available. For situations in which the toxicological database is not sufficient to establish health‐based guidance values, some approaches to risk assessment are proposed. The Scientific Committee recommends further development of the gastrointestinal micronucleus test, and research to improve the understanding of aneugenicity to support risk assessment., This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2021.EN-6814/full

This is the report of the first workshop on the Validation of Toxicogenomics-based Test Systems held in Ispra, Italy on 11-12 December 2003. The workshop was hosted by the European Centre for the Validation of Alternative Methods (ECVAM) and organized jointly by ECVAM, the U.S. Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), and the National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM). The primary aim of the workshop was to discuss and define principles applicable to the validation of toxicogenomics platforms as well as validation of specific toxicological test methods that incorporate toxicogenomics technologies. The workshop was viewed as an opportunity for initiating a dialogue between technological experts, regulators, and the principal validation bodies, and for identifying those factors to which the validation process would be applicable. It was felt that to do so now, as the technology is evolving and associated challenges are identified, would serve as the basis for the future validation of the technology when it reached the appropriate stage. Due to the complexity of the issue, different aspects of the validation of toxicogenomics-based test methods were covered. The three focus areas included (a) biological validation of toxicogenomics-based test methods for regulatory decision-making, (b) technical and bioinformatics aspects related to validation, and (c) validation issues as they relate to regulatory acceptance and utilization of toxicogenomics-based test methods. This report summarizes the discussions and details the recommendations for future direction and priorities., JRC.I.2-Validation of biomedical testing methods