Comparative study of estrogenic activities of phytoestrogens using OECD in vitro and in vivo testing methods.

With growing scientific interest in phytoestrogens, a number of studies have investigated the estrogenic potential of phytoestrogens in a wide variety of assay systems. However, evaluations of individual phytoestrogens with different assay systems make it difficult for predicting their relative estrogenic potency. The objective of this study was to compare estrogenic properties of fifteen known phytoestrogens using an estrogen receptor-α (ER-α) dimerization assay and Organization for Economic Cooperation and Development (OECD) standardized methods including in vitro estrogen receptor (ER) transactivation assay using VM7Luc4E2 cells and in vivo uterotrophic assay using an immature rat model. Human ER-α dimerization assay showed positive responses of eight test compounds and negative responses of seven compounds. These results were consistently found in luciferase reporter assay results for evaluating ER transactivation ability. Seven test compounds exhibiting relatively higher in vitro estrogenic activities were subjected to uterotrophic bioassays. Significant increases in uterine weights were only found after treatments with biochanin A, 8-prenylnaringenin, and coumestrol. Importantly, their uterotrophic effects were lost when animals were co-treated with antagonist of ER, indicating their ER-dependent effects in the uterus. In addition, analysis of estrogen responsive genes revealed that these phytoestrogens regulated uterine gene expressions differently compared to estrogens. Test methods used in this study provided a high consistency between in vitro and in vivo results. Thus, they could be used as effective screening tools for phytoestrogens, particularly focusing on their interactions with ER-α.

Progress towards an OECD reporting framework for transcriptomics and metabolomics in regulatory toxicology.

Omics methodologies are widely used in toxicological research to understand modes and mechanisms of toxicity. Increasingly, these methodologies are being applied to questions of regulatory interest such as molecular point-of-departure derivation and chemical grouping/read-across. Despite its value, widespread regulatory acceptance of omics data has not yet occurred. Barriers to the routine application of omics data in regulatory decision making have been: 1) lack of transparency for data processing methods used to convert raw data into an interpretable list of observations; and 2) lack of standardization in reporting to ensure that omics data, associated metadata and the methodologies used to generate results are available for review by stakeholders, including regulators. Thus, in 2017, the Organisation for Economic Co-operation and Development (OECD) Extended Advisory Group on Molecular Screening and Toxicogenomics (EAGMST) launched a project to develop guidance for the reporting of omics data aimed at fostering further regulatory use. Here, we report on the ongoing development of the first formal reporting framework describing the processing and analysis of both transcriptomic and metabolomic data for regulatory toxicology. We introduce the modular structure, content, harmonization and strategy for trialling this reporting framework prior to its publication by the OECD.

A cross-industry survey on photosafety evaluation of pharmaceuticals after implementation of ICH S10.

A cross-industry survey was conducted by EFPIA/IQ DruSafe in 2018 to provide information on photosafety evaluation of pharmaceuticals after implementation of ICH S10. This survey focused on the strategy utilized for photosafety risk assessment, the design of nonclinical (in vitro and in vivo) and clinical evaluations, the use of exposure margins in risk assessment, and regulatory interactions. The survey results indicated that a staged approach for phototoxicity assessment has been widely accepted by regulatory authorities globally. The OECD-based 3T3 NRU Phototoxicity Test is the most frequently used in vitro approach. Modifications to this assay suggested by ICH S10 are commonly applied. For in-vitro-positives, substantial margins from in vitro IC50 values under irradiation to Cmax (clinical) have enabled further development without the need for additional photosafety data. In vivo phototoxicity studies typically involve dosing rodents and exposing skin and eyes to simulated sunlight, and subsequently evaluating at least the skin for erythema and edema. However, no formal guidelines exist and protocols are less standardized across companies. A margin-of-safety approach (based on Cmax at NOAEL) has been successfully applied to support clinical development. Experience with dedicated clinical phototoxicity studies was limited, perhaps due to effective de-risking approaches employed based on ICH S10.

Toxicity studies of highly bioavailable isoniazid loaded solid lipid nanoparticles as per Organisation for Economic Co-operation and Development (OECD) guidelines.

Solid lipid nanoparticles (SLNs) are presently being promoted to improve bioavailability of encapsulated drugs. These are well tolerated in living systems, as they are made from biocompatible material. Despite finding extensive applicability, these systems have not been sufficiently investigated for the toxicity so far. We have reported use of SLNs to improve plasma bioavailability of isoniazid (INH), a hepatotoxic, antitubercular drug. Presently we evaluate acute and repeated (28-day) oral dose toxicity, with satellite group, of developed INH loaded COMBI-SLN. In addition to high bioavailability, the COMBI-SLN exhibited 3 times higher LD50 (2000 mg/kg BW) versus 650 mg/kg BW for free INH. Results were complemented with histopathological evidence in brain, sciatic nerve and liver tissue all of which indicated enhanced safety of INH upon incorporation into SLNs. In the repeated dose study at doses selected as per Organisation for Economic Co-operation and Development (OECD) guidelines, a series of behavioural and haematological tests, clinical biochemistry (kidney and liver function, lipid profile) and histopathological studies were performed to evaluate the effect of low (250 mg/kg BW), medium (500 mg/kg BW) and high oral dose (1000 mg/kg BW). Absence of adverse effects like hepatotoxicity and peripheral neuropathy observed in rats at an oral intake level of 500 and 1000 mg/kg BW of COMBI-SLN, that is 20-40 folds above the anticipated human intake levels (after normalizing the surface area correction for rats), supports the conclusion that SLN are an intrinsically safe nanocarrier system that improves both the efficacy and the safety of INH.

Analysis and reflection on the role of the 90-day oral toxicity study in European chemical risk assessment.

The 90-day toxicity study is one of the studies used in the safety assessment of food ingredients, medicines or other chemical substances. This paper reviews the current role of the 90-day oral toxicity study in European regulatory dossiers of chemicals by reviewing EU legislation and EU and OECD guidance documents. Regulatory provisions with regard to necessity, objectives and design of such 90-day toxicity studies vary between the different sectors addressed in this review. Most often the 90-day study is expected to be part of the standard test battery used for chemical risk assessment, without necessarily being a legal requirement and its objectives may vary between regulatory domains. Exceptions, when a 90-day study is not required are spelled out in the chemicals legislation and for food contact materials. The sectorial study design requirements of the 90-day toxicity study are very often embedded in the OECD TG 408 protocol. Differences in study objectives are not necessarily reflected in specific study designs. Considering the call for the reduction of using experimental animals for scientific purposes and the fact that a 90-day study may serve different purposes, consistency between the necessity to conduct such a study, its objectives and the study design to achieve these objectives may improve judicious use of laboratory animals. Thus there may be an opportunity to reflect and further optimise the design of in vivo toxicology studies, such as the 90-day study. This should be based on a systematic analysis of past studies and risk assessments.

Thorough evaluation of OECD principles in modelling of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives using QSARINS.

The human immunodeficiency virus is a lethal pathology considered as a worldwide problem. The search for new strategies for the treatment of this disease continues to be a great challenge in the scientific community. In this study, a series of 107 derivatives of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine, previously evaluated experimentally against HIV-I reverse transcriptase, was used to model antiretroviral activity. A model of linear regression, implemented in the QSARINS software, was developed with a genetic algorithm for variable selection. The fit of its parameters was good and exhaustive validation, according to the OECD regulatory principles, was performed. Also, the applicability domain was established. In addition, its robustness (r 2 = 0.84), stability (Q 2 LOO = 0.81; Q 2 LMO = 0.80) and good predictive power (r 2 EXT = 0.85) is proved. So, it was used to predict the antiretroviral activity of eight compounds obtained by rational drug design. Finally, it can be affirmed that the proposed tools allow the rapid and economic identification of potential antiretroviral drugs.

Me-too validation study for in vitro skin irritation test with a reconstructed human epidermis model, KeraSkin™ for OECD test guideline 439.

We conducted a me-too validation study to confirm the reproducibility, reliability, and predictive capacity of KeraSkin™ skin irritation test (SIT) as a me-too method of OECD TG 439. With 20 reference chemicals, within-laboratory reproducibility (WLR) of KeraSkin™ SIT in the decision of irritant or non-irritant was 100%, 100%, and 95% while between-laboratory reproducibility (BLR) was 100%, which met the criteria of performance standard (PS, WLR≥90%, BLR≥80%). WLR and BLR were further confirmed with intra-class correlation (ICC, coefficients >0.950). WLR and BLR in raw data (viability) were also shown with a scatter plot and Bland-Altman plot. Comparison with existing VRMs with Bland-Altman plot, ICC and kappa statistics confirmed the compatibility of KeraSkin™ SIT with OECD TG 439. The predictive capacity of KeraSkin™ SIT was estimated with 20 reference chemicals (the sensitivity of 98.9%, the specificity of 70%, and the accuracy of 84.4%) and additional 46 chemicals (for 66 chemicals [20 + 46 chemicals, the sensitivity, specificity and accuracy: 95.2%, 82.2% and 86.4%]). The receiver operating characteristic (ROC) analysis suggested a potential improvement of the predictive capacity, especially sensitivity, when changing cut-off (50% → 60-75%). Collectively, the me-too validation study demonstrated that KeraSkin™ SIT can be a new me-too method for OECD TG 439.

Reflections on the OECD guidelines for in vitro skin absorption studies.

At the 8th conference of Occupational and Environmental Exposure of the Skin to Chemicals (OEESC) (16-18 September 2019) in Dublin, Ireland, several researchers performing skin permeation assays convened to discuss in vitro skin permeability experiments. We, along with other colleagues, all of us hands-on skin permeation researchers, present here the results from our discussions on the available OECD guidelines. The discussions were especially focused on three OECD skin absorption documents, including a recent revision of one: i) OECD Guidance Document 28 (GD28) for the conduct of skin absorption studies (OECD, 2004), ii) Test Guideline 428 (TGD428) for measuring skin absorption of chemical in vitro (OECD, 2004), and iii) OECD Guidance Notes 156 (GN156) on dermal absorption issued in 2011 (OECD, 2011). GN156 (OECD, 2019) is currently under review but not finalized. A mutual concern was that these guidance documents do not comprehensively address methodological issues or the performance of the test, which might be partially due to the years needed to finalize and update OECD documents with new skin research evidence. Here, we summarize the numerous factors that can influence skin permeation and its measurement, and where guidance on several of these are omitted and often not discussed in published articles. We propose several improvements of these guidelines, which would contribute in harmonizing future in vitro skin permeation experiments.

Is there a rationale for direct dosing of chemicals to nursing pups in the EOGRTS (OECD 443)?

In OECD guideline 443 - Extended One Generation Reproductive Toxicity Study (EOGRTS) - to be used for testing industrial and agrochemicals, it has been indicated that careful consideration of benefits and disadvantages should be made prior to conducting direct-dosing studies in nursing pups. Nursing pups will not be directly dosed in dietary and drinking water studies whereas in oral gavage studies this possibility exists. Besides the risk of intubation trauma and overdosing due to direct exposure and exposure via the mother's milk, direct dosing could lead to a different hazard assessment of chemicals depending on the choice of the route of administration. In addition, in case of industrial and agrochemicals used in industrial or professional settings only, there will never be direct exposure of newborns. Moreover, direct dosing of nursing pups is an artificial, non-physiological, route of exposure and as such it would hamper risk assessment. It should therefore only be considered in exceptional cases and justified on a case-by-case approach.

A critical evaluation of thyroid hormone measurements in OECD test guideline studies: Is there any added value?

Recently several OECD test guidelines were updated to include thyroid hormone measurements for assessing endocrine disruptor potency, which led to an imperative need to align interpretation of these results by the different stakeholders. We therefore evaluated 124 repro screening studies, which showed in 38% of the studies a statistical significant finding for T4 in at least one treatment group, probably due to disturbances of normal homeostasis causing high variation. Consequently, for a thorough evaluation it is extremely important to take the historical control range into account. In conclusion, the current testing approach is not providing specific information needed to assess endocrine disruption, as too often a statistical significant finding is noted and as down-stream adverse effects are not evaluated. Therefore, major modifications are urgently needed. Instead of extending the in vivo experiments, it should be investigated if in vitro assessments will provide more relevant information on human endocrine disruptor potential.

Addressing potential ethical issues regarding the supply of human-derived products or reagents in in vitro OECD Test Guidelines.

The number and scope of Organisation for Economic Cooperation and Development (OECD) in vitro test guidelines (TGs) are increasing, in an effort to both improve human relevance and replace in vivo animal testing.  In vitro test methods being developed for TG use are increasing the use of human based reagents, in combination with, or replacing animal derived reagents, and demand for human reagents is likely to grow in the near future.  There are a range of issues associated with the ethical use of human reagents, particularly human serum, in the adaptation and development of in vitro TGs, especially to ensure that there is no human exploitation, legal requirements are adhered to, and that the origin of the reagent is assured. To address these concerns, the OECD has instigated a workshop on ethics, sources, availability and traceability of human based reagents for TG purposes, to be held in March, 2019. The focus is to provide guidance on acceptable sources of human serum for use in in vitro TGs, in terms of donor ethics and informed consent regarding commercial use and Quality Control for safety and consistent performance, with a view to providing guidance to support the adaptation and/or development of in vitro TGs using human reagents, and to ensure that in reporting the test results to regulators, clearly defined ethical and traceability aspects are adequately addressed, for the Mutual Acceptance of Data principle to be accepted in all OECD member countries. This thought-starter provides a discussion basis to achieve those objectives.

It's Still The Prices, Stupid: Why The US Spends So Much On Health Care, And A Tribute To Uwe Reinhardt.

A 2003 article titled "It's the Prices, Stupid," and coauthored by the three of us and the recently deceased Uwe Reinhardt found that the sizable differences in health spending between the US and other countries were explained mainly by health care prices. As a tribute to him, we used Organization for Economic Cooperation and Development (OECD) Health Statistics to update these analyses and review critiques of the original article. The conclusion that prices are the primary reason why the US spends more on health care than any other country remains valid, despite health policy reforms and health systems restructuring that have occurred in the US and other industrialized countries since the 2003 article's publication. On key measures of health care resources per capita (hospital beds, physicians, and nurses), the US still provides significantly fewer resources compared to the OECD median country. Since the US is not consuming greater resources than other countries, the most logical factor is the higher prices paid in the US. Because the differential between what the public and private sectors pay for medical services has grown significantly in the past fifteen years, US policy makers should focus on prices in the private sector.

Effectiveness of National Pricing Policies for Patent-Protected Pharmaceuticals in the OECD: A Systematic Literature Review.

OBJECTIVES: The aim of this review is to assess the current state of empirical research regarding the effectiveness of national pricing regulations of the patent-protected market for prescription pharmaceuticals. Effectiveness is understood to be the capacity of policies to have a desired impact on outcomes, such as health status, patient access, healthcare expenditure, and research investments, among others. METHODS: A systematic review of the published literature on pricing regulations in OECD countries was performed. The PubMed, MEDLINE, Scopus, Web of Science, Cochrane Library and the OECD iLibrary databases were searched in September 2016 and December 2017, with an update in August 2018. Interrupted time series studies and additional empirical studies were included, as well as systematic reviews if appropriate methods were applied. The risk of bias was assessed based on the recommendations of the BMJ guidelines, Cochrane EPOC criteria, QHES instrument, HTA good practice guidelines, CRD's guidance and the CHEC criteria. The quality of evidence was evaluated using the suggestions from EPOC and GRADE. RESULTS: Thirty-one publications met the inclusion criteria. Most of the assessed empirical research included therapeutic (TRP) and/or external reference pricing (ERP), with a clear majority focusing on TRP. The main outcomes that were analysed were drug prices, expenditures and drug use. For value-based pricing (VBP), only limited empirical data were found. CONCLUSIONS: We found evidence that TRP may reduce pharmaceutical prices and expenditures in the short term. Furthermore, TRP may lead to substitution effects towards lower-priced pharmaceuticals. The effects of TRP on patient access, healthcare utilisation and R&D investments were found to be uncertain. No conclusions were drawn for ERP and VBP. No evidence was found for the effects on health outcomes for any of the analysed policies. There is a strong need for evidence generation regarding effective pricing policies, particularly for VBP, managed entry agreements and non-financial outcomes.

Determination of the relationship between patient satisfaction and some global economic indicators using multidimensional scaling.

CONTEXT: The importance of labor that contributes to the economy and economic power of the country is increasing recently. There is a strong link between health and economy. People are happier, more productive, and provide more contribution to the economy in communities of healthy individuals. In countries with strong economy, serious economic investments are made in the field of health to grow healthy individuals. AIM: The purpose of this study is to determine whether patient satisfaction in primary healthcare services is related to economic strength of countries. MATERIALS AND METHODS: The data of European Patients Evaluate General/Family Practice (EUROPEP) scale from 2011 at 17 Organization for Economic Co-operation and Development (OECD) countries are used. The data were compiled from OECD reports and Republic of Turkey Ministry of Health Refik Saydam Hygiene Center Presidency School of Public Health patient satisfaction with primary healthcare services reports. STATISTICAL ANALYSIS USED: 17 OECD member countries in 2011 health expenditure data, some health indicators, and patient satisfaction are determined to show how grouping in two-dimensional space with the multidimensional scaling. RESULTS: It was observed to vary by countries and groupings that they located in terms of all three criteria. In some countries' economic and health indicators, although quite high compared to the OECD average, citizen satisfaction of healthcare services was low. In some countries, although health expenditure and health indicators are far below the OECD average, citizens' satisfaction with health services has proved to be very high. CONCLUSION: Multidimensional scaling analysis findings reveal that countries have different positions and groups in terms of each three indicators. According to these results, it cannot be said that high expenditures in the field of health will affect patients satisfaction. Having a strong economy or spending too much money on health does not increase human satisfaction in health care. Effective expenditures on the field of health will increase healthcare service satisfaction. Policy-makers should consider international criteria and take the right steps according to citizens' expectation and satisfaction of healthcare service to implement effective spending.

Integration of sperm DNA damage assessment into OECD test guidelines for genotoxicity testing using the MutaMouse model.

The Organisation for Economic Co-operation and Development (OECD) endorses test guidelines (TG) for identifying chemicals that are genotoxic, such as the transgenic rodent gene mutation assay (TG 488). Current OECD TG do not include assays for sperm DNA damage resulting in a critical testing gap. We evaluated the performance of the Sperm Chromatin Structure Assay (SCSA) and the Terminal Deoxynucleotidyl Transferase-Mediated Deoxyuridine Triphosphate Nick end Labeling (TUNEL) assay to detect sperm DNA damage within the recommended TG 488 protocol. MutaMouse males received 0, 0.5, 1, or 2 mg/kg/day triethylenemelamine (TEM), a multifunctional alkylating agent, for 28 days orally and tissues were collected two (blood) and three (sperm and bone marrow) days later. TEM significantly increased the frequency of lacZ mutants in bone marrow, and of micronuclei (MN) in both reticulocytes (%MN-RET) and normochromatic erythrocytes (%MN-NCE) in a dose-dependent manner (P < 0.05). The percentage of DNA fragmentation index (%DFI) and %TUNEL positive cells demonstrated dose-related increases in sperm (P < 0.05), and the two assay results were strongly correlated (R = 0.9298). Within the same animal, a good correlation was observed between %MN-NCE and %DFI (R = 0.7189). Finally, benchmark dose modelling (BMD) showed comparable BMD10 values among the somatic and germ cell assays. Our results suggest that sperm DNA damage assays can be easily integrated into standard OECD designs investigating genotoxicity in somatic tissues to provide key information on whether a chemical is genotoxic in germ cells and impact its risk assessment.

Simulation of mouse and rat spermatogenesis to inform genotoxicity testing using OECD test guideline 488.

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.

Identifying germ cell mutagens using OECD test guideline 488 (transgenic rodent somatic and germ cell gene mutation assays) and integration with somatic cell testing.

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.

Integrated Approaches to Testing and Assessment.

The concept of Integrated Approaches to Testing and Assessment (IATA) has been advanced by the Organisation for Economic Cooperation and Development (OECD) member countries to enable a progressive shift from traditional chemical assessments largely based on the observation of the adverse effect in animal models, using individual methods or predefined batteries of standard toxicity tests, to assessment strategies integrating diverse lines of evidence. The flexible nature of IATA allows the inclusion of mechanistic data generated with non-animal methods and with new technologies (e.g. high-throughput and high content methods). The assessment process within IATA is typically conducted through weight-of-evidence which inevitably includes the elements of subjective expert judgement. For these reasons, IATA cannot be fully harmonized across sectors and countries. Nevertheless, some of the IATA components, such as defined approaches, which consist of a fixed data interpretation procedure (DIP) applied to data generated with a defined set of information sources, can be harmonized. The focus of this MiniReview is to provide an illustration of the differences between the IATA developed so far in the areas of regulatory toxicology, and ongoing activities related to the international harmonization of defined approaches that rely on multiple non-animal information sources.

Integrated Approaches to Testing and Assessment: OECD Activities on the Development and Use of Adverse Outcome Pathways and Case Studies.

The Organisation for Economic Co-operation and Development (OECD) works with member countries and other stakeholders to improve and harmonize chemical assessment methods. In 2012, the OECD Adverse Outcome Pathways (AOPs) Development Programme started. The Programme has published six AOPs thus far and more than 60 AOPs are under various stages of development under the Programme. This article reviews recent OECD activities on the use of AOPs in developing Integrated Approaches to Testing and Assessments (IATAs). The guidance document for the use of AOPs in developing IATA, published in 2016, provides a framework for developing and using IATA and describes how IATA can be based on an AOP. The guidance document on the reporting of defined approaches to be used within IATA, also published in 2016, provides a set of principles for reporting defined approaches to testing and assessment to facilitate their evaluation. In the guidance documents, the AOP concept plays an important role for building IATA approaches in a science-based and transparent way. In 2015, the IATA Case Studies Project was launched to increase experience with the use of IATA and novel hazard methodologies by developing case studies, which constitute examples of predictions that are fit-for-regulatory use. This activity highlights the importance of international collaboration for harmonizing and improving chemical safety assessment methods.

Biometrical evaluation of the performance of the revised OECD Test Guideline 402 for assessing acute dermal toxicity.

A comprehensive biometrical assessment was conducted to compare the performance of multiple test designs for acute dermal systemic toxicity to support the animal welfare update to the original OECD Test Guideline (TG) 402 for acute dermal toxicity. The test designs evaluated included: (1) two, three, or five animals per dose group (2) evident toxicity or lethality endpoints and (3) absence or presence of a one-animal sighting study. The revision of TG 402 respected the 3R principles (replace, reduce, refine) of animal testing. The results demonstrate that the TG 402 test design can be optimised with reduced animal numbers per test group, such that a scenario of two animals per group following a sighting study at a starting dose of 200 mg/kg bw (unless further information is available to better define the starting dose) would provide a classification which in most cases is conservative, without compromising both the statistical ability of the study to assess dermal toxicity, or the relevant classification outcome.