15 years out: reinventing ICCVAM

Drivers of and Obstacles to the Adoption of Toxicogenomics for Chemical Risk Assessment: Insights from Social Science Perspectives

BACKGROUND

Some 20 y ago, scientific and regulatory communities identified the potential of omics sciences (genomics, transcriptomics, proteomics, metabolomics) to improve chemical risk assessment through development of toxicogenomics. Recognizing that regulators adopt new scientific methods cautiously given accountability to diverse stakeholders, the scope and pace of adoption of toxicogenomics tools and data have nonetheless not met the ambitious, early expectations of omics proponents.

OBJECTIVE

Our objective was, therefore, to inventory, investigate, and derive insights into drivers of and obstacles to adoption of toxicogenomics in chemical risk assessment. By invoking established social science frameworks conceptualizing innovation adoption, we also aimed to develop recommendations for proponents of toxicogenomics and other new approach methodologies (NAMs).

METHODS

We report findings from an analysis of 56 scientific and regulatory publications from 1998 through 2017 that address the adoption of toxicogenomics for chemical risk assessment. From this purposeful sample of toxicogenomics discourse, we identified major categories of drivers of and obstacles to adoption of toxicogenomics tools and data sets. We then mapped these categories onto social science frameworks for conceptualizing innovation adoption to generate actionable insights for proponents of toxicogenomics.

DISCUSSION

We identify the most salient drivers and obstacles. From 1998 through 2017, adoption of toxicogenomics was understood to be helped by drivers such as those we labeled Superior scientific understanding, New applications, and Reduced cost & increased efficiency but hindered by obstacles such as those we labeled Insufficient validation, Complexity of interpretation, and Lack of standardization. Leveraging social science frameworks, we find that arguments for adoption that draw on the most salient drivers, which emphasize superior and novel functionality of omics as rationales, overlook potential adopters' key concerns: simplicity of use and compatibility with existing practices. We also identify two perspectives-innovation-centric and adopter-centric-on omics adoption and explain how overreliance on the former may be undermining efforts to promote toxicogenomics. https://doi.org/10.1289/EHP6500.

Non-animal methods to predict skin sensitization (II): an assessment of defined approaches *

Skin sensitization is a toxicity endpoint of widespread concern, for which the mechanistic understanding and concurrent necessity for non-animal testing approaches have evolved to a critical juncture, with many available options for predicting sensitization without using animals. Cosmetics Europe and the National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods collaborated to analyze the performance of multiple non-animal data integration approaches for the skin sensitization safety assessment of cosmetics ingredients. The Cosmetics Europe Skin Tolerance Task Force (STTF) collected and generated data on 128 substances in multiple in vitro and in chemico skin sensitization assays selected based on a systematic assessment by the STTF. These assays, together with certain in silico predictions, are key components of various non-animal testing strategies that have been submitted to the Organization for Economic Cooperation and Development as case studies for skin sensitization. Curated murine local lymph node assay (LLNA) and human skin sensitization data were used to evaluate the performance of six defined approaches, comprising eight non-animal testing strategies, for both hazard and potency characterization. Defined approaches examined included consensus methods, artificial neural networks, support vector machine models, Bayesian networks, and decision trees, most of which were reproduced using open source software tools. Multiple non-animal testing strategies incorporating in vitro, in chemico, and in silico inputs demonstrated equivalent or superior performance to the LLNA when compared to both animal and human data for skin sensitization.

The inadequacies of pre-market chemical risk assessment's toxicity studies-the implications

Industry provides essentially all the data for most (pre-market) chemical risk assessments (RA); academics study a chemical once it is marketed. For two randomly-chosen high production chemicals, despite new European Union mandates to evaluate all data, just 13% of the herbicide bentazon and 15% of the flame-retardant hexabromocyclododecane's published toxicity studies were found in their pre-market RA, and a systematic review on bentazon concludes it has greater hazards than indicated in its RA. More important, for both, academia's toxicity studies were designated as lower quality than industries were, despite showing hazards at lower doses. The accuracy of industry's test methods is analyzed and found to be replicable but insensitive, thus inaccurate. The synthetic pharmaceutical industry originated them, and by 1983 the Organization for Economic Cooperation & Development mandated their test guidelines (TG) methods be accepted for any new study for pre-market RA. For existing studies, industry's "Klimisch" criterion is universally used to evaluate quality, but it only states that TG studies produce the best data. However, no TG can answer the realistic exposure effect hypotheses of academics; therefore, crucially in pre-market RA, tens of thousands of published experimental findings (increasingly at low dose) are ignored to determine the safe dose. Few appreciate this, so scientific debate on the most accurate elements of toxicity tests is urgently indicated. Copyright © 2016 John Wiley & Sons, Ltd.

Integrated decision strategies for skin sensitization hazard

One of the top priorities of the Interagency Coordinating Committee for the Validation of Alternative Methods (ICCVAM) is the identification and evaluation of non-animal alternatives for skin sensitization testing. Although skin sensitization is a complex process, the key biological events of the process have been well characterized in an adverse outcome pathway (AOP) proposed by the Organisation for Economic Co-operation and Development (OECD). Accordingly, ICCVAM is working to develop integrated decision strategies based on the AOP using in vitro, in chemico and in silico information. Data were compiled for 120 substances tested in the murine local lymph node assay (LLNA), direct peptide reactivity assay (DPRA), human cell line activation test (h-CLAT) and KeratinoSens assay. Data for six physicochemical properties, which may affect skin penetration, were also collected, and skin sensitization read-across predictions were performed using OECD QSAR Toolbox. All data were combined into a variety of potential integrated decision strategies to predict LLNA outcomes using a training set of 94 substances and an external test set of 26 substances. Fifty-four models were built using multiple combinations of machine learning approaches and predictor variables. The seven models with the highest accuracy (89-96% for the test set and 96-99% for the training set) for predicting LLNA outcomes used a support vector machine (SVM) approach with different combinations of predictor variables. The performance statistics of the SVM models were higher than any of the non-animal tests alone and higher than simple test battery approaches using these methods. These data suggest that computational approaches are promising tools to effectively integrate data sources to identify potential skin sensitizers without animal testing. Published 2016. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Advances in the Development and Validation of Test Methods in the United States

The National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) provides validation support for US Federal agencies and the US Tox21 interagency consortium, an interagency collaboration that is using high throughput screening (HTS) and other advanced approaches to better understand and predict chemical hazards to humans and the environment. The use of HTS data from assays relevant to the estrogen receptor signaling data pathway is used as an example of how HTS data can be combined with computational modeling to meet the needs of US agencies. As brief summary of US efforts in the areas of biologics testing, acute toxicity, and skin sensitization will also be provided.

A new path forward: the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and National Toxicology Program's Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)

In 2000, the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) was congressionally established, with representatives from Federal regulatory and research agencies that require, use, generate, or disseminate toxicologic and safety testing information. For over 15 y, ICCVAM and the National Toxicology Program's Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) have worked together to promote the development, validation, and regulatory acceptance of test methods that replace, reduce, or refine the use of animals in regulatory testing. In 2013, both NICEATM and ICCVAM underwent major changes to their operating paradigms, to increase the speed and efficiency of regulatory approval and industry adoption of 3Rs testing methods within the United States and internationally. Accordingly, increased emphasis has been placed on international activities, primarily through interaction with the Organization for Economic Cooperation and Development and participation in the International Cooperation on Alternative Test Methods. In addition, ICCVAM has committed to increasing public awareness of and transparency about federal agencies' 3R activities and to fostering interactions with stakeholders. Finally, although it continues to support ICCVAM, NICEATM's work now includes validation support for Tox21, a collaboration aimed at identifying in vitro methods and computational approaches for testing chemicals to better understand and predict hazards to humans and the environment. The combination of more efficient operating paradigms, increased international collaboration, improved communication and interaction with stakeholders, and active participation in Tox21 likely will substantially increase the number of 3Rs methods developed and used in the United States and internationally.

Risk assessment's insensitive toxicity testing may cause it to fail

BACKGROUND

Risk assessment of chemicals and other agents must be accurate to protect health. We analyse the determinants of a sensitive chronic toxicity study, risk assessment's most important test. Manufacturers originally generate data on the properties of a molecule, and if government approval is needed to market it, laws globally require toxicity data to be generated using Test Guidelines (TG), i.e. test methods of the Organisation for Economic Cooperation and Development (OECD), or their equivalent. TGs have advantages, but they test close-to-poisonous doses for chronic exposures and have other insensitivities, such as not testing disease latency. This and the fact that academic investigators will not be constrained by such artificial methods, created a de facto total ban of academia's diverse and sensitive toxicity tests from most risk assessment.

OBJECTIVE

To start and sustain a dialogue between regulatory agencies and academic scientists (secondarily, industry and NGOs) whose goals would be to (1) agree on the determinants of accurate toxicity tests and (2) implement them (via the OECD).

DISCUSSION

We analyse the quality of the data produced by these incompatible paradigms: regulatory and academic toxicology; analyse the criteria used to designate data quality in risk assessment; and discuss accurate chronic toxicity test methods.

CONCLUSION

There are abundant modern experimental methods (and rigorous epidemiology), and an existing systematic review system, to at long last allow academia's toxicity studies to be used in most risk assessments.

Mechanistic validation

Validation of new approaches in regulatory toxicology is commonly defined as the independent assessment of the reproducibility and relevance (the scientific basis and predictive capacity) of a test for a particular purpose. In large ring trials, the emphasis to date has been mainly on reproducibility and predictive capacity (comparison to the traditional test) with less attention given to the scientific or mechanistic basis. Assessing predictive capacity is difficult for novel approaches (which are based on mechanism), such as pathways of toxicity or the complex networks within the organism (systems toxicology). This is highly relevant for implementing Toxicology for the 21st Century, either by high-throughput testing in the ToxCast/Tox21 project or omics-based testing in the Human Toxome Project. This article explores the mostly neglected assessment of a test's scientific basis, which moves mechanism and causality to the foreground when validating/qualifying tests. Such mechanistic validation faces the problem of establishing causality in complex systems. However, pragmatic adaptations of the Bradford Hill criteria, as well as bioinformatic tools, are emerging. As critical infrastructures of the organism are perturbed by a toxic mechanism we argue that by focusing on the target of toxicity and its vulnerability, in addition to the way it is perturbed, we can anchor the identification of the mechanism and its verification.