A proposed testing framework for developmental immunotoxicology (DIT).

A group of thirty immunotoxicology experts from the U.S. and E.U. representing government, industry, and academia met in May 2003, in Washington, D.C., to reach consensus regarding the most appropriate methods to assess developmental immunotoxicology (DIT) for hazard identification, including under what conditions such testing might be required. The following points represent the major conclusions from this roundtable discussion: (1) the rat is the preferred model; (2) any DIT protocol should be based on immune assays already validated; (3) DIT methods should be incorporated into standard developmental and reproductive toxicity protocols to the extent possible rather than a "stand-alone" protocol; (4) the approach to address DIT potential should be similar for chemicals and drugs, but the experimental design should be flexible and should reflect the specific questions to be answered; (5) it is possible to utilize a study design that assesses all critical windows in one protocol, with the results leading to further study of specific effects, as warranted; (6) animals should be exposed throughout the treatment protocol; (7) the triggers for DIT may include structure-activity-relationships, results from other toxicity studies, the intended use of a drug/chemical and/or its anticipated exposure of neonates and/or juveniles.     

Report from the EPAA workshop: In vitro ADME in safety testing used by EPAA industry sectors

There are now numerous in vitro and in silico ADME alternatives to in vivo assays but how do different industries incorporate them into their decision tree approaches for risk assessment, bearing in mind that the chemicals tested are intended for widely varying purposes? The extent of the use of animal tests is mainly driven by regulations or by the lack of a suitable in vitro model. Therefore, what considerations are needed for alternative models and how can they be improved so that they can be used as part of the risk assessment process? To address these issues, the European Partnership for Alternative Approaches to Animal Testing (EPAA) working group on prioritisation, promotion and implementation of the 3Rs research held a workshop in November, 2008 in Duesseldorf, Germany. Participants included different industry sectors such as pharmaceuticals, cosmetics, industrial- and agro-chemicals. This report describes the outcome of the discussions and recommendations (a) to reduce the number of animals used for determining the ADME properties of chemicals and (b) for considerations and actions regarding in vitro and in silico assays. These included: standardisation and promotion of in vitro assays so that they may become accepted by regulators; increased availability of industry in vivo kinetic data for a central database to increase the power of in silico predictions; expansion of the applicability domains of in vitro and in silico tools (which are not necessarily more applicable or even exclusive to one particular sector) and continued collaborations between regulators, academia and industry. A recommended immediate course of action was to establish an expert panel of users, developers and regulators to define the testing scope of models for different chemical classes. It was agreed by all participants that improvement and harmonization of alternative approaches is needed for all sectors and this will most effectively be achieved by stakeholders from different sectors sharing data.     

Understanding mechanisms of toxicity: insights from drug discovery research

Toxicology continues to rely heavily on use of animal testing for prediction of potential for toxicity in humans. Where mechanisms of toxicity have been elucidated, for example endocrine disruption by xenoestrogens binding to the estrogen receptor, in vitro assays have been developed as surrogate assays for toxicity prediction. This mechanistic information can be combined with other data such as exposure levels to inform a risk assessment for the chemical. However, there remains a paucity of such mechanistic assays due at least in part to lack of methods to determine specific mechanisms of toxicity for many toxicants. A means to address this deficiency lies in utilization of a vast repertoire of tools developed by the drug discovery industry for interrogating the bioactivity of chemicals. This review describes the application of high-throughput screening assays as experimental tools for profiling chemicals for potential for toxicity and understanding underlying mechanisms. The accessibility of broad panels of assays covering an array of protein families permits evaluation of chemicals for their ability to directly modulate many potential targets of toxicity. In addition, advances in cell-based screening have yielded tools capable of reporting the effects of chemicals on numerous critical cell signaling pathways and cell health parameters. Novel, more complex cellular systems are being used to model mammalian tissues and the consequences of compound treatment. Finally, high-throughput technology is being applied to model organism screens to understand mechanisms of toxicity. However, a number of formidable challenges to these methods remain to be overcome before they are widely applicable. Integration of successful approaches will contribute towards building a systems approach to toxicology that will provide mechanistic understanding of the effects of chemicals on biological systems and aid in rationale risk assessments.     

Developmental immunotoxicology and risk assessment: a workshop summary

A workshop entitled 'Developmental Immunotoxicology and Risk Assessment' was held on 12-13 June 2001, in Washington, DC. The workshop was organized jointly by the Immunotoxicology Technical Committee (ITC) of the International Life Sciences Institute's (ILSI) Health and Environmental Sciences Institute (HESI) with input from the U.S. Environmental Protection Agency (EPA). Growing public concern that early exposure of the developing immune system to immunotoxic compounds may cause significant or persistent postnatal immunosuppression prompted the workshop. The main goal of the workshop was to examine scientific questions that underlie developmental immunotoxicity tests and the interpretation of the results as they relate to human risk assessment. A second goal was to provide a framework, based on current scientific knowledge, for the development of meaningful testing guidelines. The workshop focused on a series of questions that included how to address critical windows of exposure, how to develop and apply more predictive endpoints, does early chemical exposure cause transient or permanent effects on the immune system, as well as other related questions. On the first day, experts were invited to give scientific presentations relating to comparative developmental immunology, models of immunosuppression, and the regulatory aspects of developmental immunotoxicology. The second day was devoted to a panel discussion that included all the speakers as well as meeting participants, which attempted to answer each of the specific questions raised at the workshop. In general, it was acknowledged that there are a variety of techniques available for assessing immunosuppression in adult animal models, but there is uncertainty about how to apply these to a developing animal, especially if the goal is to have some standard procedure that can be applied for regulatory risk assessment. It was pointed out that although we know a lot about the developing immune system of individual species, we do not know how to relate the significance of drug or chemical effects on these systems in terms of human hazard. Overall, the panel deemed the area of developmental immunotoxicity to be still in its infancy and outlined strategies that could lead to the development of standard practices.     

Immunotoxicogenomics: the potential of genomics technology in the immunotoxicity risk assessment process.

Evaluation of xenobiotic-induced changes in gene expression as a method to identify and classify potential toxicants is being pursued by industry and regulatory agencies worldwide. A workshop was held at the Research Triangle Park campus of the Environmental Protection Agency to discuss the current state-of-the-science of "immunotoxicogenomics" and to explore the potential role of genomics techniques for immunotoxicity testing. The genesis of the workshop was the current lack of widely accepted triggering criteria for Tier 1 immunotoxicity testing in the context of routine toxicity testing data, the realization that traditional screening methods would require an inordinate number of animals and are inadequate to handle the number of chemicals that may need to be screened (e.g., high production volume compounds) and the absence of an organized effort to address the state-of-the-science of toxicogenomics in the identification of immunotoxic compounds. The major focus of the meeting was on the theoretical and practical utility of genomics techniques to (1) replace or supplement current immunotoxicity screening procedures, (2) provide insight into potential modes or mechanisms of action, and (3) provide data suitable for immunotoxicity hazard identification or risk assessment. The latter goal is of considerable interest to a variety of stakeholders as a means to reduce animal use and to decrease the cost of conducting and interpreting standard toxicity tests. A number of data gaps were identified that included a lack of dose response and kinetic data for known immunotoxic compounds and a general lack of data correlating genomic alterations to functional changes observed in vivo. Participants concluded that a genomics approach to screen chemicals for immunotoxic potential or to generate data useful to risk assessors holds promise but that routine use of these methods is years in the future. However, recent progress in molecular immunology has made mode and mechanism of action studies much more practical. Furthermore, a variety of published immunotoxicity studies suggest that microarray analysis is already a practical means to explore pathway-level changes that lead to altered immune function. To help move the science of immunotoxicogenomics forward, a partnership of industry, academia, and government was suggested to address data gaps, validation, quality assurance, and protocol development.     

Current trends in in silico,in vitro toxicology,and safety biomarkers in early drug development

The development of new medicines is a long and expensive process. Despite growing efforts in R&D over the last decades, attrition rate due to safety issues (especially cardiac and hepatic toxicity) remains a major challenge for the pharmaceutical industry. This may lead to market withdrawal or late stage halting of a drug development program. Consequently, early detection of toxicity issues is critical to avoid late-stage failures. To this end, development of predictive toxicology assays and models have become a strategic matter for drug makers. An integrated approach confronting knowledge-based data sources with in vitro and in vivo experimental data should be performed. A well-defined balance between in vivo and in vitro assays should guide the safety assessment process and include a rationale taking into account ethical considerations as well as associated resourcing involved with animal use. Innovation in de-risking strategies may support refinement of regulatory testing and contribute to (i) improve drug safety evaluation alleviating assessment of the risk-benefit ratio and (ii) promote the access to safe drugs for patients. In this review, promising innovative approaches aiming at facilitating early detection of toxicity during drug development are described.     

Computational chemistry, systems biology and toxicology. Harnessing the chemistry of life: revolutionizing toxicology. a commentary

There is a continuing interest in, and increasing imperatives for, the development of alternative methods for toxicological evaluations that do not require the use of animals. Although a significant investment has resulted in some achievements, progress has been patchy and there remain many challenges. Among the most significant hurdles is developing non-animal methods that would permit assessment of the potential for a chemical or drug to cause adverse health effects following repeated systemic exposure. Developing approaches to address this challenge has been one of the objectives of the European Partnership for Alternative Approaches to Animal Testing (EPAA). The EPAA is a unique partnership between the European Commission and industry that has interests in all aspects of reducing, refining and replacing the use of animals (the '3Rs'). One possible strategy that emerged from a broad scientific debate sponsored by the EPAA was the opportunity for developing entirely new paradigms for toxicity testing based upon harnessing the increasing power of computational chemistry in combination with advanced systems biology. This brief commentary summarizes a workshop organized by the EPAA in 2010, that had the ambitious title of 'Harnessing the Chemistry of Life: Revolutionizing Toxicology'. At that workshop international experts in chemistry, systems biology and toxicology sought to map out how best developments in these sciences could be exploited to design new strategies for toxicity testing using adverse effects in the liver as an initial focus of attention. Here we describe the workshop design and outputs, the primary purpose being to stimulate debate about the need to align different areas of science with toxicology if new and truly innovative approaches to toxicity testing are to be developed.     

The ChemScreen project to design a pragmatic alternative approach to predict reproductive toxicity of chemicals

There is a great need for rapid testing strategies for reproductive toxicity testing, avoiding animal use. The EU Framework program 7 project ChemScreen aimed to fill this gap in a pragmatic manner preferably using validated existing tools and place them in an innovative alternative testing strategy. In our approach we combined knowledge on critical processes affected by reproductive toxicants with knowledge on the mechanistic basis of such effects. We used in silico methods for prescreening chemicals for relevant toxic effects aiming at reduced testing needs. For those chemicals that need testing we have set up an in vitro screening panel that includes mechanistic high throughput methods and lower throughput assays that measure more integrative endpoints. In silico pharmacokinetic modules were developed for rapid exposure predictions via diverse exposure routes. These modules to match in vitro and in vivo exposure levels greatly improved predictivity of the in vitro tests. As a further step, we have generated examples how to predict reproductive toxicity of chemicals using available data. We have executed formal validations of panel constituents and also used more innovative manners to validate the test panel using mechanistic approaches. We are actively engaged in promoting regulatory acceptance of the tools developed as an essential step towards practical application, including case studies for read-across purposes. With this approach, a significant saving in animal use and associated costs seems very feasible.     

药物非临床生殖发育毒性试验中逐案原则的建议

本文围绕药物非临床生殖发育毒性试验中逐案原则展开讨论,认为:①不同的研究目的决定着不同的研究策略。②受试物的种类不同选择试验种类亦各异。③在特定的研究机构需要设立阳性对照组。④实验动物的选择需要考虑受试物的特点。⑤实验动物的给药途径需要考虑实际可行。⑥根据受试物特色增设特异性指标的检测。⑦适时开展生殖毒性伴随毒代动力学试验。⑧基于多方面实际资料综合分析得出结论。因此,既要依从药物生殖发育毒性非临床安全性评价研究的通则,又要在对受试物充分认识的基础上,遵循"具体问题具体分析"的原则,避免因循守旧和循规蹈矩,最终经仔细观测、审慎分析,综合多方面信息对试验结果进行全面分析评价,以至能准确地下达结论。     

Considerations for the nonclinical safety evaluation of antibody drug conjugates for oncology

Antibody drug conjugates (ADCs) include monoclonal antibodies that are linked to cytotoxic small molecules. A number of these agents are currently being developed as anti-cancer agents designed to improve the therapeutic index of the cytotoxin (i.e., cytotoxic small molecule or cytotoxic agent) by specifically delivering it to tumor cells. This paper presents primary considerations for the nonclinical safety evaluation of ADCs and includes strategies for the evaluation of the entire ADC or the various individual components (i.e., antibody, linker or the cytotoxin). Considerations are presented on how to design a nonclinical safety assessment program to identify the on- and off-target toxicities to enable first-in-human (FIH) studies. Specific discussions are also included that provide details as to the need and how to conduct the studies for evaluating ADCs in genetic toxicology, tissue cross-reactivity, safety pharmacology, carcinogenicity, developmental and reproductive toxicology, biotransformation, toxicokinetic monitoring, bioanalytical assays, immunogenicity testing, test article stability and the selection of the FIH dose. Given the complexity of these molecules and our evolving understanding of their properties, there is no single all-encompassing nonclinical strategy. Instead, each ADC should be evaluated on a case-by-case scientifically-based approach that is consistent with ICH and animal research guidelines.     

The Biological Control of the Malaria Vector

The call for malaria control, over the last century, marked a new epoch in the history of this disease. Many control strategies targeting either the Plasmodium parasite or the Anopheles vector were shown to be effective. Yet, the emergence of drug resistant parasites and insecticide resistant mosquito strains, along with numerous health, environmental, and ecological side effects of many chemical agents, highlighted the need to develop alternative tools that either complement or substitute conventional malaria control approaches. The use of biological means is considered a fundamental part of the recently launched malaria eradication program and has so far shown promising results, although this approach is still in its infancy. This review presents an overview of the most promising biological control tools for malaria eradication, namely fungi, bacteria, larvivorous fish, parasites, viruses and nematodes.     

Putting the parts together: Combining in vitro methods to test for skin sensitizing potentials

Allergic contact dermatitis is a common skin disease and is elicited by repeated skin contact with an allergen. In the regulatory context, currently only data from animal experiments are acceptable to assess the skin sensitizing potential of substances. Animal welfare and EU Cosmetic Directive/Regulation call for the implementation of animal-free alternatives for safety assessments. The mechanisms that trigger skin sensitization are complex and various steps are involved. Therefore, a single in vitro method may not be able to accurately assess this endpoint. Non-animal methods are being developed and validated and can be used for testing strategies that ensure a reliable prediction of skin sensitization potentials. In this study, the predictivities of four in vitro assays, one in chemico and one in silico method addressing three different steps in the development of skin sensitization were assessed using 54 test substances of known sensitizing potential. The predictivity of single tests and combinations of these assays were compared. These data were used to develop an in vitro testing scheme and prediction model for the detection of skin sensitizers based on protein reactivity, activation of the Keap-1/Nrf2 signaling pathway and dendritic cell activation.     

Functional assays are mandatory for a correct prediction of immunotoxic properties of compounds in vitro

An increasing aim in safety assessment of chemicals and drugs is to reduce, refine and replace animal testing, especially in the context of the new system for the registration, evaluation and authorisation of chemicals (REACH). Regarding immunosuppression, most methods are based on mitogen stimulation assays. To our knowledge the in vitro antibody response (Mishell–Dutton culture) has never been considered as an alternative to the existing animal tests nor has its potential of correctly predicting different immunosuppressant compounds been analyzed. Therefore, we designed a study comprising seven immunosuppressant and four negative compounds and compared the results to data obtained from rat mitogen stimulation experiments (analysis of proliferation, TNFα and IFNγ release). The in vitro antibody response showed a high sensitivity and specificity. It is a promising assay for the prediction of immunosuppressive properties of chemicals and drugs, whereas the results from rat spleen cell mitogen stimulation assays were rather poor in respect thereof. Mitogen stimulation assays are restricted to certain cell types and the chosen endpoints, while any compound-induced alteration is likely to be detected in a functional assay like the in vitro antibody response, when several immunocompetent cells have to cooperate to result in the humoral response analyzed.     

ReProComet: a new in vitro method to assess DNA damage in mammalian sperm.

The increasing request of chemical safety assessment demands for the validation of alternative methods to reduce the resort to animal experimentation. Methods that evaluate reproductive toxicity are among those requiring the largest use of animals. Presently, no validated in vitro alternative exists for the assessment of reproductive toxicity. Mammalian sperm are sensitive targets of DNA-reactive chemicals, which form premutagenic adducts. Here, we propose a new method based on comet assay to detect DNA damage induced by potential germ cell mutagens in bull sperm available from assisted reproduction practices. In somatic cells, chemical-induced adducts can be revealed by comet assay that detects DNA breaks produced during adduct repair. Mature sperm, however, are devoid of repair enzymes, and adducts are processed only after fertilization. For this reason, comet assay is not sensitive to detect DNA lesions induced in sperm by most chemicals. To overcome such limitation, we developed a modified comet assay based on the addition of a protein extract from HeLa cells to agarose-embedded sperm on microscopic slides. To test the method, sperm were treated in vitro with methyl methanesulfonate (MMS) or melphalan (MLP) and comet assay was conducted both with and without protein supplementation. No effect of MMS or MLP was detected without protein supplementation; on the contrary, a clear-cut dose-dependent effect was measured after addition of the cell extract. These results represent a proof of concept of a novel in vitro mutagenicity test on sperm that could offer a promising approach to complement previously validated in vivo germ cell genotoxicity assays.     

Toxicology, Environmental Health, and the “One Health” Concept

The One Health concept promotes collaboration among veterinarians, physicians, scientists, and other professions to promote human, animal, and ecosystem health. One Health illustrates the interconnectedness and interdependence of human, animal, and ecosystem health. This concept has traditionally focused on zoonoses that are infectious diseases, not on chemical- or poison-related illnesses in animals and their relationship to the detection and prevention of human illness. The purpose of this article is to describe key experiences of scientists in the Health Studies Branch within the National Center for Environmental of Health of the Centers for Disease Control and Prevention in which the study of animal illness facilitated a public health investigation into an outbreak of chemicalassociated human disease. The experiences highlight how utilizing the One Health approach may improve chemical-associated outbreak investigations and facilitate appropriate intervention strategies. An appropriate One Health approach in toxicology and environmental health in outbreak settings should include consideration of the common environments and food sources shared by humans and animals and consideration of the potential for contaminated animal products as food sources in human exposures.     

Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS)-Based Biowaivers: A workshop Summary Report

The workshop “Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS) Based Biowaivers” was held virtually on December 6, 2021, organized by the University of Maryland Center of Excellence in Regulatory Science and Innovation (M-CERSI), and the Food and Drug Administration (FDA). The workshop focused on the industrial, academic, and regulatory experiences in generating and evaluating permeability data, with the aim to further facilitate implementation of the BCS and efficient development of high-quality drug products globally. As the first international permeability workshop since the BCS based biowaivers was finalized as the ICH M9 guideline, the workshop included lectures, panel discussions, and breakout sessions. Lecture and panel discussion topics covered case studies at IND, NDA, and ANDA stages, typical deficiencies relating to permeability assessment supporting BCS biowaiver, types of evidence that are available to demonstrate high permeability, method suitability of a permeability assay, impact of excipients, importance of global acceptance of permeability methods, opportunities to expand the use of biowaivers (e.g. non-Caco-2 cell lines, totality-of-evidence approach to demonstrate high permeability) and future of permeability testing. Breakout sessions focused on 1) in vitro and in silico intestinal permeability methods; 2) potential excipient effects on permeability and; 3) use of label and literature data to designate permeability class.     

A tiered approach to the use of alternatives to animal testing for the safety assessment of cosmetics: Genotoxicity. A COLIPA analysis

For the assessment of genotoxic effects of cosmetic ingredients, a number of well-established and regulatory accepted in vitro assays are in place. A caveat to the use of these assays is their relatively low specificity and high rate of false or misleading positive results. Due to the 7th amendment to the EU Cosmetics Directive ban on in vivo genotoxicity testing for cosmetics that was enacted March 2009, it is no longer possible to conduct follow-up in vivo genotoxicity tests for cosmetic ingredients positive in in vitro genotoxicity tests to further assess the relevance of the in vitro findings. COLIPA, the European Cosmetics Association, has initiated a research programme to improve existing and develop new in vitro methods. A COLIPA workshop was held in Brussels in April 2008 to analyse the best possible use of available methods and approaches to enable a sound assessment of the genotoxic hazard of cosmetic ingredients. Common approaches of cosmetic companies are described, with recommendations for evaluating in vitro genotoxins using non-animal approaches. A weight of evidence approach was employed to set up a decision-tree for the integration of alternative methods into tiered testing strategies.     

The 6th Drug Discovery for Neurodegeneration Conference: An Intensive Course on Translating Research into Drugs

Neurodegenerative disorders are rapidly becoming one of the greatest unmet health needs. This annual workshop facilitates innovation and progress in neurodegenerative disease drug discovery by convening stakeholders from charitable foundations, government, academia and industry who introduce scientists to the drug development and approval process. New to the 2012 workshop were candid discussions about re-visiting the CNS therapeutic development process. The continuing challenge is partly due to the poor forecasting potential of models of CNS diseases, as well as the lack of reproducibility of published studies, and greater need to increase focus on pharmacodynamic end points. Significant discussion centered on how to improve discovery approaches using examples of recent successes in the field. For example, the idea of combining reductionist, single-target strategies with functional-approach logic was suggested by several speakers, and widely discussed in the workshop. The didactic aspects of the workshop highlighted underlying concepts, best practices and trends that have characterized successful campaigns. The technical and scientific guidance was complemented by discussions of practical ways to approach the major funding gaps required for translation of projects from basic science to clinical investigations. This workshop has evolved to serve a critical educational need, with a wide range of investigator participation.     

Application of toxicokinetics to improve chemical risk assessment: Implications for the use of animals

While toxicokinetics has become an integral part of pharmaceutical safety assessment over the last two decades, its use in the chemical industry is relatively new. However, it is recognised as a potentially important tool in human health risk assessment and recent initiatives have advocated greater application of toxicokinetics as part of an improved assessment strategy for crop protection chemicals that could offer greater efficiency, use fewer animals and provide better data for risk assessment purposes. To explore the potential scientific and animal welfare benefits of increased use of toxicokinetic data across the chemical industry, an international workshop was held in 2008. Experts from a wide range of chemical industry sectors, including industrial chemicals, agrochemicals and consumer products, participated in the meeting as well as representatives from relevant regulatory authorities. Pharmaceutical industry experts were also invited, in order to share experiences from the extensive use of toxicokinetics in drug development. Given that increased generation of toxicokinetic data could potentially result in an increased number of animals undergoing testing, technologies and strategies to reduce and refine animal use for this purpose were also considered. This paper outlines and expands upon the key themes that emerged from the workshop.