By the new Medical Device Regulation (MDR, EU 2017/745) the use of certain phthalates which are carcinogenic, mutagenic, toxic to reproduction (CMR) or have endocrine-disrupting (ED) properties, above 0.1% by weight (w/w) is only allowed after a proper justification. The SCHEER provide Guidelines on the benefit-risk assessment (BRA) of the presence of such phthalates in certain medical devices. The Guidelines describe the methodology on how to perform a BRA for the justification of the presence of CMR/ED phthalates in medical devices and/or or parts or materials used therein at percentages above 0.1% w/w. They also describe the evaluation of possible alternatives for these phthalates used in medical devices, including alternative materials, designs or medical treatments. Relevant stakeholders e.g. manufacturers, notified bodies and regulatory bodies, can use the guidelines. The approach of these guidelines may also be used for a BRA of other CMR/ED substances present in medical devices. SCHEER noticed that a number of BRA methodologies are theoretically available. However, there is a considerable lack of data needed for the BRA for potential relevant alternatives to be used in medical devices. Therefore, SCHEER encourages manufacturers to generate data of high quality on such alternatives for CMR/ED phthalates in medical devices.

The Organisation for Economic Co-operation and Development Test Guideline 488 (TG 488) provides recommendations for assessing germ cell and somatic cell mutagenicity using transgenic rodent (TGR) models. However, important data gaps exist for selecting an optimal approach for simultaneously evaluating mutagenicity in both cell types. It is uncertain whether analysis of germ cells from seminiferous tubules (hereafter, tubule germ cells) or caudal sperm within the recommended design for somatic tissues (i.e., 28 days of exposure plus three days of fixation time, 28 + 3d) has enough sensitivity to detect an effect as compared with the analysis of sperm within the recommended design for germ cells (i.e., 28 + 49d and 28 + 70d for mouse and rat, respectively). To address these data gaps, the Germ Cell workgroup of the Genetic Toxicology Technical Committee of the Health and Environmental Sciences Institute reviewed the available TGR mutagenicity data in male germ cells, and, characterized the exposure history of tubule germ cells for different sampling times to evaluate its impact on germ cell mutagenicity testing using TG 488. Our analyses suggest that evaluating mutant frequencies in: i) sperm from the cauda epididymis at 28 + 3d does not provide meaningful mutagenicity data; ii), tubule germ cells at 28 + 3d provides reliable mutagenicity data only if the results are positive; and iii) tubule germ cells at 28 + 28d produces reliable positive and negative results in both mice and rats. Thus, the 28 + 28d regimen may provide an approach for simultaneously assessing mutagenicity in somatic tissues and germ cells from the same animals. Further work is required to support the 28 + 28d protocol for tissues other than slowly proliferating tissues as per current TG 488. Finally, recommendations are provided to guide the experimental design for germ cell mutagenicity data for regulatory submission, as well as other possible approaches to increase the reliability of the TGR assay.

The Organisation for Economic Co-operation and Development Test Guideline (TG) 488 for the transgenic rodent (TGR) mutation assay recommends two sampling times for assessing germ cell mutagenicity following the required 28-day exposure period: 28 + > 49 days for mouse sperm and 28 + >70 days for rat sperm from the cauda epididymis, or three days (i.e., 28 + 3d) for germ cells from seminiferous tubules (hereafter, tubule germ cells) plus caudal sperm for mouse and rat. Although the latter protocol is commonly used for mutagenicity testing in somatic tissues, it has several shortcomings for germ cell testing because it provides limited exposure of the proliferating phase of spermatogenesis when mutations are fixed in the transgene. Indeed, analysis of sperm at 28 + 3d has generated negative results with established germ cell mutagens, while the analysis of tubule germ cells has generated both positive and either negative or equivocal results. The Germ Cell workgroup of the Genetic Toxicology Technical Committee of the Health and Environmental Sciences Institute modelled mouse and rat spermatogenesis to better define the exposure history of the cell population collected from seminiferous tubules. The modelling showed that mouse tubule germ cells at 28 + 3d receive, as a whole, 42% of the total exposure during the proliferating phase. This percentage increases to 99% at 28 + 28d and reaches 100% at 28 + 30d. In the rat, these percentages are 22% and 80% at 28 + 3d and 28 + 28d, reaching 100% at 28 + 44d. These results show that analysis of tubule germ cells at 28 + 28d may be an effective protocol for assessing germ cell mutagenicity in mice and rats using TG 488. Since TG 488 recommends the 28 + 28d protocol for slow dividing somatic tissues, this appears to be a better compromise than 28 + 3d when slow dividing somatic tissues or germ cells are the critical tissues of interest.

The \'Organization for Economic Co-operation and Development (OECD) guidelines for the Testing of Chemicals\' aims to identify whether a chemical is a genotoxic hazard, and these guidelines \'are periodically reviewed in the light of scientific progress, changing regulatory needs and animal welfare considerations\'. OECD published a mammalian erythrocyte micronucleus test guideline for testing chemicals (1) that proposes: \'Animals are treated with the test chemical once…Samples of peripheral blood are taken at least twice (from the same group of animals), starting not earlier than 36 h after treatment, with appropriate intervals following the first sample, but not extending beyond 72 h\'. This guidelines are base on the report by the Collaborative Study Group for the Micronucleus Test (CSGMT), which was based on the sampling of mice peripheral blood every 24 h We investigated the kinetics of micronucleus induction by taking samples prior to administration and every 8 or 10 h after single treatment. The comparisons suggest that 24-h sampling could cause not only an underestimation of the responses to various agents but also a misestimation of the time of maximal induction. We proposed that samples of peripheral blood must be collected at two different times during an optimal 25-h sampling range (from 25 to 50 h). Besides, we hypothesize that the time of maximal EPC-MN induction depends on the time required for the mechanisms involved in micronucleus production; and we suggest that a kinetic analysis of MN-PCE induction by several agents with well-known mechanisms of micronuclei induction would allow derivation of a specific relationship between the kinetics of MN-PCE induction and some process of DNA breaks and/or micronuclei induction.

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA\'s direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin\'s lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

ICH/regional guidances and agency scrutiny provide the regulatory framework for safety assessment and control of impurities in small-molecule drug substances and drug products. We provide a critical assessment of the principal impurity guidances and, in particular, focus on deficiencies in the derivation of the threshold of toxicological concern (TTC) as applied to genotoxic impurities and the many toxicological anomalies generated by following the current guidelines on impurities. In terms of pharmacopoeial standards, we aim to highlight the fact that strictly controlling numerous impurities, especially those that are minor structural variants of the active substance, is likely to produce minimal improvements in drug safety. It is believed that, wherever possible, there is a need to simplify and rebalance the current impurity paradigm, moving away from standards derived largely from batch analytical data towards structure-based qualification thresholds and risk assessments using readily available safety data. Such changes should also lead to a minimization of in vivo testing for toxicological qualification purposes. Recent improvements in analytical techniques and performance have enabled the detection of ever smaller amounts of impurities with increased confidence. The temptation to translate this information directly to the regulatory sphere without any kind of safety evaluation should be resisted.

There is a pressing requirement to define a hazard identification and risk management strategy for nanomaterials due to the rapid growth in the nanotechnology industry and their promise of life-style revolutions through the development of wide-ranging nano-containing consumer products. Consequently, a battery of well defined and appropriate in vitro assays to assess a number of genotoxicity endpoints is required to minimise extensive and costly in vivo testing. However, the validity of the established protocols in current OECD recognised genotoxicity assays for nanomaterials is currently being questioned. In this report, we therefore consider the in vitro OECD genotoxicity test battery including the Ames, micronucleus and HPRT forward mutation assays, and their potential role in the safety assessment of nanomaterial induced DNA damage in vitro.

The OECD guideline for the in vitro mammalian cell micronucleus test (OECD 487) was recently adopted in July 22, 2010. Since its publication, it has become apparent that the guidance for testing chemicals where solubility is a limiting factor can be interpreted in a variety of ways. In this communication, we provide clarification for testing insoluble chemicals. The intent of the OECD 487 guideline is for the high dose to be the lowest precipitating concentration even if toxicity occurs above the solubility limit in tissue culture medium. Examination of precipitation can be done by the unaided eye or microscopically. Precipitation is examined at the onset or end of treatment, with the intent to identify precipitate present during treatment.

Reference genotoxic compounds 2-aminoanthracene, diethylstilboestrol and vinblastine were tested in the in vitro micronucleus assay using Chinese hamster V79 derived cells in the laboratories of British American Tobacco in the UK. The work was conducted in support of the cytotoxicity measures recommended in the 2007 version of the OECD Test Guideline 487. The three compounds were positive in the assay in the presence and absence of the cytokinesis blocking agent cytochalasin B at concentrations that did not exceed the recommended cytotoxic limits determined by relative population doubling, relative increase in cell counts, relative cell counts and cytokinesis block proliferation index. Consequently, this work supports the hypothesis that relative population doubling, relative increase in cell counts and relative cell counts are appropriate measures of cytotoxicity for the non-cytokinesis blocked in vitro micronucleus assay.

The reference genotoxic agents 2-aminoanthracene (a metabolism dependent weak clastogen), 5-fluorouracil (a nucleoside analogue, characterised by a steep dose response profile), colchicine (an aneugen that inhibits tubulin polymerisation), benzo[a]pyrene (a polycyclic aromatic hydrocarbon requiring metabolic activation), cadmium chloride (an inorganic carcinogen), and cytosine arabinoside (a nucleoside analogue that inhibits the gap-filling step of excision repair) were tested in the in vitro micronucleus assay using the Chinese hamster ovary (CHO) cell line at Covance Laboratories, Harrogate, UK. All chemicals were treated in the absence and presence of cytokinesis block (via addition of cytochalasin B) with this work forming part of a collaborative evaluation of the toxicity measures recommended in the draft OECD Test Guideline 487 on the In vitro Mammalian Cell Micronucleus Test (MNvit). The toxicity measures used, detecting a possible combination of both cytostasis and cell death (though not cell death directly), were relative population doubling, relative increase in cell counts and relative cell counts for treatments in the absence of cytokinesis block, and replication index in the presence of cytokinesis block. All of the chemicals tested either gave marked positive increases in the percentage of micronucleated cells with and without cytokinesis block, or did not induce micronuclei at concentrations giving approximately 50-60% toxicity (cytostasis and cell death) or less by all of the toxicity measures used. The outcome from this series of tests supports the use of relative increase in cell counts and relative population doubling, as well as relative cell counts, as appropriate measures of cytotoxicity for the non-cytokinesis blocked in vitro micronucleus assay.