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The in vitro micronucleus test is commonly used in the early stages of pharmaceutical development as a predictive tool for the regulatory mouse lymphoma assay or in vitro chromosome aberration test. The accumulated data from this assay leads to the suggestion that it could be used as an alternative to the chromosome aberration test or the mouse lymphoma assay in the regulatory genotoxicity battery. In this paper, we present the results of the in vitro micronucleus test on L5178Y mouse lymphoma cells with 25 compounds from Servier research and have compared these results to those obtained in the genotoxicity regulatory battery. All the negative compounds were also negative in the in vitro micronucleus assay. Among the 14 positive compounds, two of them, positive in the mouse lymphoma assay, were found negative in the in vitro micronucleus test. However, this apparent discordance was likely to be due to cytotoxicity- or high concentration-related false positive responses in the mouse lymphoma assay. In addition, we confirmed that the in vitro micronucleus assay is useful for detecting aneugens, especially, when cells in metaphasis and multinucleated cells are also scored and when cells are allowed to recover after the long treatment. On this series of compounds, the in vitro micronucleus assay showed high sensitivity and possibly a better specificity than the mouse lymphoma assay. Thus, the in vitro micronucleus assay was shown to be at least as adequate as the mouse lymphoma assay or the in vitro chromosome aberration test to be used in the standard genotoxicity battery.

The minimal three-test battery of the International Conference on Harmonization guideline has been in use since 1997 for the development of new pharmaceuticals (ICH, 1997). After a 10-year experience of this core battery in regulatory genotoxicity testing, everywhere the time has come for reflection about what was learned from this experience. Different aspects of genotoxicity testing are currently being debated under different organizations (HESI, 2006; IWGT, 2007; Kirkland et al., 2007). The main concerns are to develop relevant strategies and adequate complementary tests to the minimal battery, appropriate for each specific case to assess risk for humans when in vitro positive results or findings in rodent bioassays for carcinogenicity are found. In this article, an example of an in-house decision tree is shown, with some options which can contribute to the current reflections. Additionally, tools built for early genotoxicity are presented.

This review presents a European Federation of Pharmaceutical Industries and Association/PreClinical Development Expert Group (EFPIA‐PDEG) topic group consensus on a data‐driven approach to harmonized contraception recommendations for clinical trial protocols and product labeling. There is no international agreement in pharmaceutical clinical trial protocols or product labeling on when/if female and/or male contraception is warranted and for how long after the last dose. This absence of consensus has resulted in different recommendations among regions. For most pharmaceuticals, contraception recommendations are generally based exclusively on nonclinical data and/or mechanism. For clinical trials, contraception is the default position and is maintained for women throughout clinical development, whereas appropriate information can justify removing male contraception. Conversely, contraception is only recommended in product labeling when warranted. A base case rationale is proposed for whether or not female and/or male contraception is/are warranted, using available genotoxicity and developmental toxicity data. Contraception is generally warranted for both male and female subjects treated with mutagenic pharmaceuticals. We propose as a starting point that contraception is not typically warranted when the margin is 10‐fold or greater between clinical exposure at the maximum recommended human dose and exposure at the no observed adverse effect level (NOAEL) for purely aneugenic pharmaceuticals and for pharmaceuticals that induce fetal malformations or embryo‐fetal lethality. Other factors are discussed, including contraception methods, pregnancy testing, drug clearance, options for managing the absence of a developmental toxicity NOAEL, drug‐drug interactions, radiopharmaceuticals, and other drug modalities. Overall, we present a data‐driven rationale that can serve as a basis for consistent contraception recommendations in clinical trials and in product labeling across regions.

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