60 Years of the 3Rs symposium: Lessons learned and the road ahead.

When The Principles of Humane Experimental Technique was published in 1959, authors William Russell and Rex Burch had a modest goal: to make researchers think about what they were doing in the laboratory - and to do it more humanely. Sixty years later, their groundbreaking book was celebrated for inspiring a revolution in science and launching a new field: The 3Rs of alternatives to animal experimentation. On November 22, 2019, some pioneering and leading scientists and researchers in the field gathered at the Johns Hopkins Bloomberg School of Public Health in Bal-timore for the 60 Years of the 3Rs Symposium: Lessons Learned and the Road Ahead. The event was sponsored by the Johns Hopkins Center for Alternatives to Animal Testing (CAAT), the Foundation for Chemistry Research and Initiatives, the Alternative Research & Development Foundation (ARDF), the American Cleaning Institute (ACI), the International Fragrance Association (IFRA), the Institute for In Vitro Sciences (IIVS), John "Jack" R. Fowle III, and the Society of Toxicology (SoT). Fourteen pres-entations shared the history behind the groundbreaking publication, international efforts to achieve its aims, stumbling blocks to progress, as well as remarkable achievements. The day was a tribute to Russell and Burch, and a testament to what is possible when people from many walks of life - science, government, and industry - work toward a common goal.

William Russell and Rex Burch published their book The Principles of Humane Experimental Technique in 1959. The book encouraged researchers to replace animal experiments where it was possible, to refine experiments with animals in order to reduce their suffering, and to reduce the number of animals that had to be used for experiments to the minimum. Sixty years later, a group of pioneering and leading scientists and researchers in the field gathered to share how the publi­cation came about and how the vision inspired international collaborations and successes on many different levels including new laws. The paper includes an overview of important milestones in the history of alternatives to animal experimentation.

A Systematic Review to Compare Chemical Hazard Predictions of the Zebrafish Embryotoxicity Test With Mammalian Prenatal Developmental Toxicity.

Originally developed to inform the acute toxicity of chemicals on fish, the zebrafish embryotoxicity test (ZET) has also been proposed for assessing the prenatal developmental toxicity of chemicals, potentially replacing mammalian studies. Although extensively evaluated in primary studies, a comprehensive review summarizing the available evidence for the ZET's capacity is lacking. Therefore, we conducted a systematic review of how well the presence or absence of exposure-related findings in the ZET predicts prenatal development toxicity in studies with rats and rabbits. A two-tiered systematic review of the developmental toxicity literature was performed, a review of the ZET literature was followed by one of the mammalian literature. Data were extracted using DistillerSR, and study validity was assessed with an amended SYRCLE's risk-of-bias tool. Extracted data were analyzed for each species and substance, which provided the basis for comparing the 2 test methods. Although limited by the number of 24 included chemicals, our results suggest that the ZET has potential to identify chemicals that are mammalian prenatal developmental toxicants, with a tendency for overprediction. Furthermore, our analysis confirmed the need for further standardization of the ZET. In addition, we identified contextual and methodological challenges in the application of systematic review approaches to toxicological questions. One key to overcoming these challenges is a transition to more comprehensive and transparent planning, conduct and reporting of toxicological studies. The first step toward bringing about this change is to create broad awareness in the toxicological community of the need for and benefits of more evidence-based approaches.

Beyond the 3Rs: Expanding the use of human-relevant replacement methods in biomedical research.

This year marks the 60th anniversary of Russell and Burch's pioneering book, The Principles of Humane Experimental Technique. Their 3Rs framework has helped to inspire humane and scientific progress in experimental technique. However, it is time to update its strategic application. The 21st century has already seen the development of promising, high-tech non-animal models, such as organs-on-a-chip and computational approaches that, in our view, will replace animals as the default option in biomedical experimentation. How fast this transition will take place will depend on the pace at which these new models are optimized to reflect the biology of humans, rather than that of non-human animals. While the new methods are likely to reshape all areas in which animals are currently used in science, we particularly encourage their application in biomedical research, which accounts for the bulk of animals used. We call for the pursuit of a three-prong strategy that focuses on (1) advancing non-animal methods as replacements of animal experiments, (2) applying them to biomedical research, and (3) improving their relevance to human biology. As academics and scientists, we feel that educational efforts targeted at young scientists in training will be an effective and sustainable way to advance this vision. Our strategy may not promise an imminent end to the use of animals in science, but it will bring us closer to an era in which the 3Rs are increasingly perceived as a solution to a receding problem. Russell and Burch themselves surely would have welcomed these positive changes.

Adaptation of the Systematic Review Framework to the Assessment of Toxicological Test Methods: Challenges and Lessons Learned With the Zebrafish Embryotoxicity Test.

Systematic review methodology is a means of addressing specific questions through structured, consistent, and transparent examinations of the relevant scientific evidence. This methodology has been used to advantage in clinical medicine, and is being adapted for use in other disciplines. Although some applications to toxicology have been explored, especially for hazard identification, the present preparatory study is, to our knowledge, the first attempt to adapt it to the assessment of toxicological test methods. As our test case, we chose the zebrafish embryotoxicity test (ZET) for developmental toxicity and its mammalian counterpart, the standard mammalian prenatal development toxicity study, focusing the review on how well the ZET predicts the presence or absence of chemical-induced prenatal developmental toxicity observed in mammalian studies. An interdisciplinary team prepared a systematic review protocol and adjusted it throughout this piloting phase, where needed. The final protocol was registered and will guide the main study (systematic review), which will execute the protocol to comprehensively answer the review question. The goal of this preparatory study was to translate systematic review methodology to the assessment of toxicological test method performance. Consequently, it focused on the methodological issues encountered, whereas the main study will report substantive findings. These relate to numerous systematic review steps, but primarily to searching and selecting the evidence. Applying the lessons learned to these challenges can improve not only our main study, but may also be helpful to others seeking to use systematic review methodology to compare toxicological test methods. We conclude with a series of recommendations that, if adopted, would help improve the quality of the published literature, and make conducting systematic reviews of toxicological studies faster and easier over time.

A primer on systematic reviews in toxicology.

Systematic reviews, pioneered in the clinical field, provide a transparent, methodologically rigorous and reproducible means of summarizing the available evidence on a precisely framed research question. Having matured to a well-established approach in many research fields, systematic reviews are receiving increasing attention as a potential tool for answering toxicological questions. In the larger framework of evidence-based toxicology, the advantages and obstacles of, as well as the approaches for, adapting and adopting systematic reviews to toxicology are still being explored. To provide the toxicology community with a starting point for conducting or understanding systematic reviews, we herein summarized available guidance documents from various fields of application. We have elaborated on the systematic review process by breaking it down into ten steps, starting with planning the project, framing the question, and writing and publishing the protocol, and concluding with interpretation and reporting. In addition, we have identified the specific methodological challenges of toxicological questions and have summarized how these can be addressed. Ultimately, this primer is intended to stimulate scientific discussions of the identified issues to fuel the development of toxicology-specific methodology and to encourage the application of systematic review methodology to toxicological issues.

The Emergence of Systematic Review in Toxicology.

The Evidence-based Toxicology Collaboration hosted a workshop on "The Emergence of Systematic Review and Related Evidence-based Approaches in Toxicology," on November 21, 2014 in Baltimore, Maryland. The workshop featured speakers from agencies and organizations applying systematic review approaches to questions in toxicology, speakers with experience in conducting systematic reviews in medicine and healthcare, and stakeholders in industry, government, academia, and non-governmental organizations. Based on the workshop presentations and discussion, here we address the state of systematic review methods in toxicology, historical antecedents in both medicine and toxicology, challenges to the translation of systematic review from medicine to toxicology, and thoughts on the way forward. We conclude with a recommendation that as various agencies and organizations adapt systematic review methods, they continue to work together to ensure that there is a harmonized process for how the basic elements of systematic review methods are applied in toxicology.

Guidance on assessing the methodological and reporting quality of toxicologically relevant studies: A scoping review.

Assessments of methodological and reporting quality are critical to adequately judging the credibility of a study's conclusions and to gauging its potential reproducibility. To aid those seeking to assess the methodological or reporting quality of studies relevant to toxicology, we conducted a scoping review of the available guidance with respect to four types of studies: in vivo and in vitro, (quantitative) structure-activity relationships ([Q]SARs), physico-chemical, and human observational studies. Our aims were to identify the available guidance in this diverse literature, briefly summarize each document, and distill the common elements of these documents for each study type. In general, we found considerable guidance for in vivo and human studies, but only one paper addressed in vitro studies exclusively. The guidance for (Q)SAR studies and physico-chemical studies was scant but authoritative. There was substantial overlap across guidance documents in the proposed criteria for both methodological and reporting quality. Some guidance documents address toxicology research directly, whereas others address preclinical research generally or clinical research and therefore may not be fully applicable to the toxicology context without some translation. Another challenge is the degree to which assessments of methodological quality in toxicology should focus on risk of bias - as in clinical medicine and healthcare - or be broadened to include other quality measures, such as confirming the identity of test substances prior to exposure. Our review is intended primarily for those in toxicology and risk assessment seeking an entry point into the extensive and diverse literature on methodological and reporting quality applicable to their work.

The usefulness of systematic reviews of animal experiments for the design of preclinical and clinical studies.

The question of how animal studies should be designed, conducted, and analyzed remains underexposed in societal debates on animal experimentation. This is not only a scientific but also a moral question. After all, if animal experiments are not appropriately designed, conducted, and analyzed, the results produced are unlikely to be reliable and the animals have in effect been wasted. In this article, we focus on one particular method to address this moral question, namely systematic reviews of previously performed animal experiments. We discuss how the design, conduct, and analysis of future (animal and human) experiments may be optimized through such systematic reviews. In particular, we illustrate how these reviews can help improve the methodological quality of animal experiments, make the choice of an animal model and the translation of animal data to the clinic more evidence-based, and implement the 3Rs. Moreover, we discuss which measures are being taken and which need to be taken in the future to ensure that systematic reviews will actually contribute to optimizing experimental design and thereby to meeting a necessary condition for making the use of animals in these experiments justified.

Incorporating new technologies into toxicity testing and risk assessment: moving from 21st century vision to a data-driven framework.

Based on existing data and previous work, a series of studies is proposed as a basis toward a pragmatic early step in transforming toxicity testing. These studies were assembled into a data-driven framework that invokes successive tiers of testing with margin of exposure (MOE) as the primary metric. The first tier of the framework integrates data from high-throughput in vitro assays, in vitro-to-in vivo extrapolation (IVIVE) pharmacokinetic modeling, and exposure modeling. The in vitro assays are used to separate chemicals based on their relative selectivity in interacting with biological targets and identify the concentration at which these interactions occur. The IVIVE modeling converts in vitro concentrations into external dose for calculation of the point of departure (POD) and comparisons to human exposure estimates to yield a MOE. The second tier involves short-term in vivo studies, expanded pharmacokinetic evaluations, and refined human exposure estimates. The results from the second tier studies provide more accurate estimates of the POD and the MOE. The third tier contains the traditional animal studies currently used to assess chemical safety. In each tier, the POD for selective chemicals is based primarily on endpoints associated with a proposed mode of action, whereas the POD for nonselective chemicals is based on potential biological perturbation. Based on the MOE, a significant percentage of chemicals evaluated in the first 2 tiers could be eliminated from further testing. The framework provides a risk-based and animal-sparing approach to evaluate chemical safety, drawing broadly from previous experience but incorporating technological advances to increase efficiency.

Evidence-based toxicology for the 21st century: opportunities and challenges.

The Evidence-based Toxicology Collaboration (EBTC) was established recently to translate evidence-based approaches from medicine and health care to toxicology in an organized and sustained effort. The EBTC held a workshop on "Evidence-based Toxicology for the 21st Century: Opportunities and Challenges" in Research Triangle Park, North Carolina, USA on January 24-25, 2012. The presentations largely reflected two EBTC priorities: to apply evidence-based methods to assessing the performance of emerging pathway-based testing methods consistent with the 2007 National Research Council report on "Toxicity Testing in the 21st Century" as well as to adopt a governance structure and work processes to move that effort forward. The workshop served to clarify evidence-based approaches and to provide food for thought on substantive and administrative activities for the EBTC. Priority activities include conducting pilot studies to demonstrate the value of evidence-based approaches to toxicology, as well as conducting educational outreach on these approaches.

Accelerating the development of 21st-century toxicology: outcome of a Human Toxicology Project Consortium workshop.

The U.S. National Research Council (NRC) report on "Toxicity Testing in the 21st century" calls for a fundamental shift in the way that chemicals are tested for human health effects and evaluated in risk assessments. The new approach would move toward in vitro methods, typically using human cells in a high-throughput context. The in vitro methods would be designed to detect significant perturbations to "toxicity pathways," i.e., key biological pathways that, when sufficiently perturbed, lead to adverse health outcomes. To explore progress on the report's implementation, the Human Toxicology Project Consortium hosted a workshop on 9-10 November 2010 in Washington, DC. The Consortium is a coalition of several corporations, a research institute, and a non-governmental organization dedicated to accelerating the implementation of 21st-century Toxicology as aligned with the NRC vision. The goal of the workshop was to identify practical and scientific ways to accelerate implementation of the NRC vision. The workshop format consisted of plenary presentations, breakout group discussions, and concluding commentaries. The program faculty was drawn from industry, academia, government, and public interest organizations. Most presentations summarized ongoing efforts to modernize toxicology testing and approaches, each with some overlap with the NRC vision. In light of these efforts, the workshop identified recommendations for accelerating implementation of the NRC vision, including greater strategic coordination and planning across projects (facilitated by a steering group), the development of projects that test the proof of concept for implementation of the NRC vision, and greater outreach and communication across stakeholder communities.

An animal protection perspective on 21st century toxicology.

The Humane Society of the United States (HSUS) strongly endorses the vision for the future of toxicity testing proposed in the 2007 National Research Council report Toxicity Testing in the 21st Century. Although crafted primarily with the aim of better assessing the public health risks from chemical exposures, the vision would have a major impact on advancing both alternative testing methods and animal welfare. Consequently, The HSUS seeks to have the vision implemented expeditiously. The HSUS is pleased that the report has elicited considerable discussion and debate and garnered a certain level of approval and applaud current implementation efforts. However, these efforts do not fully capture the vision and strategy outlined by the NRC. The HSUS believes that the timely implementation of the NRC vision warrants a large-scale "Human Toxicology Project" akin to the Human Genome Project of the late 20th century. The HSUS spearheaded the formation of the Human Toxicology Project Consortium to help marshal the necessary will, funding, and research for this effort. Our sister organization, the Humane Society International, is embarking on a related effort with European partners. The HSUS cofounded a website, AltTox.org, devoted exclusively to the scientific and policy issues central to advancing nonanimal methods of toxicity testing. The NRC report has provided a unified framework by which to systematically incorporate the fruits of modern biology and technology into hazard identification and risk assessment, to the betterment not only of toxicity testing and public health, but also of animal protection.

Noncompliance with Public Health Service (PHS) policy on humane care and use of laboratory animals: an exploratory analysis.

The National Institutes of Health (NIH) is a major biomedical research-funding body in the United States. Approximately 40% of NIH-funded research involves experimentation on nonhuman animals (Monastersky, 2008). Institutions that conduct animal research with NIH funds must adhere to the Public Health Service (PHS) care and use standards of the Office of Laboratory Animal Welfare (OLAW, 2002a). Institutions deviating significantly from the PHS's animal care and use standards must report these incidents to the NIH's OLAW. This study is an exploratory analysis of all the significant deviations reported by animal-research facilities to OLAW during a 3-month period. The study identifies the most common issues reported and species involved. The study found that the majority of the incidents resulted in animal pain and distress and that 75% ended in animal death. This study offers preliminary recommendations to address the most common problems identified in this analysis. This study urges OLAW and other stakeholders to analyze larger, more recent samples of reported deviations to compare with these results and ultimately improve adherence to animal welfare standards.

Personal reflections on Russell and Burch, FRAME, and the HSUS.

The coincidence of anniversaries associated with the publication of William Russell and Rex Burch's The Principles of Humane Experimental Technique, the founding of the Fund for the Replacement of Animals in Medical Experiments (FRAME), and the establishment of the collaboration between FRAME and the University of Nottingham, provides an opportunity to reflect on Russell and Burch's legacy and how it was carried forward by FRAME. The Principles, published in 1959, was the pioneering work in what later became the alternatives or Three Rs field of replacement, reduction, and refinement of animal use. Such was the book's initial and undeserved obscurity, however, that FRAME, following its founding in 1969, pioneered a similar approach independently of Russell and Burch's work. The Humane Society of the United States (HSUS) was also an early champion of the alternatives framework, and through the establishment of the Russell and Burch Award, helped unite Russell and Burch with what had emerged as the alternatives community. Thanks largely to FRAME, Russell and Burch were able to participate in Three Rs activity before their deaths. They lived long enough to see their ideas take hold, but not long enough to see the emerging revolution currently under way in toxicity testing, toward the use of non-animal methods.

Report of the Working Group on Animal Distress in the Laboratory.

Finding ways to minimize pain and distress in research animals is a continuing goal in the laboratory animal research field. Pain and distress, however, are not synonymous, and measures that alleviate one may not affect the other. Here, the authors provide a summary of a meeting held in February 2004 that focused on distress in laboratory animals. They discuss the difficulties associated with defining 'distress,' propose methods to aid in recognizing and alleviating distressful conditions, and provide recommendations for animal research conduct and oversight that would minimize distress experienced by laboratory animals.

A demographic analysis of primate research in the United States.

An analysis of primate research in the USA, including the number and species of non-human primates used, types of research, levels of invasiveness, housing conditions and funding, is an important step in addressing various concerns (ethical and scientific) surrounding primate research. An analysis of monkey and chimpanzee research, conducted by The Humane Society of the United States (HSUS), demonstrated that the USA uses more non-human primates (including great apes) in research per year, than any other country in the world. The US government devotes approximately $575-800 million per year to primate research and care. Chimpanzees are most commonly used for hepatitis research; monkeys are most commonly used for HIV research, and other research areas include vaccine and drug testing, cognition, human pathologies/diseases, drug abuse and xenotransplantation. Legislation (including great ape research bans), media attention and proposed increased primate use also contribute to the overall picture of current and future non-human primate research in the USA and throughout the world. The HSUS proposes that cost-benefit analyses of non-human primate research in the USA be conducted to properly assess "value added" to relevant fields of research and whether the use of non-human primates is the only, or most effective, strategy for biomedical progress. Finally, The HSUS proposes a ban on the use of apes in research in the USA and worldwide.

The HSUS's Pain and Distress Initiative: overview and update.

The Humane Society of the United States (HSUS) publicly launched its Pain and Distress Initiative in 2000, to encourage greater attention to the prevention and alleviation of pain and distress in research animals. The initiative's ultimate goal is the phasing out of all significant pain and distress in animal research by 2020. There have been several developments to date. A survey conducted for The HSUS revealed that Americans strongly oppose the use of animals in experiments that cause them to suffer. The HSUS has begun producing a newsletter, The Pain & Distress Report, distributed periodically to over 2000 Institutional Animal Care and Use Committees, scientists and regulators. In 2000, the US Department of Agriculture issued a proposal to upgrade the regulation and reporting of pain and distress. We have challenged the leading research institutions over their under-reporting of unrelieved pain and distress in animals. We have written a comprehensive critique of CO2 euthanasia, arguing that it causes avoidable pain and distress in animals. The National Institutes of Health has issued new guidance on CO2 euthanasia. These developments lay the groundwork for a sustained effort to eliminate animal suffering in research.

Biology teachers' attitudes to dissection and alternatives.

A survey of 5000 American middle and high school level biology teachers was completed to assess attitudes and classroom practice relating to dissection and alternative teaching methods. A preliminary sample of 494 respondents revealed that 79% of teachers used dissection to teach biology. While 72% believed that dissection was an important part of the curriculum, 17% disagreed; 69% considered dissection to be an essential hands-on activity. While 31% believed that alternatives were as good as dissection for teaching anatomy and physiology, 55% disagreed. The primary reason given for continuing dissection, rather than exclusively using alternatives, was the hands-on aspect of dissection (69%). While the majority (66%) of biology teachers favoured student choice between dissection and other learning methods, 20% disagreed. Although the effectiveness of alternative methods has been documented, and ethical arguments against dissection have been advanced, the mainstream introduction of humane alternatives to dissection requires a transformation of the beliefs, experience and practice of biology teachers.