Applicability of physicochemical data, QSARs and read‐across in Threshold of Toxicological Concern assessment

QSAR/QSPR models based on quantum chemistry for risk assessment of pesticides according to current European legislation

In Europe, agencies and official organizations involved in the pesticide control such as the EFSA, ECHA, JRC and ECETOC or even the OECD are pointing out that the software tools based on quantitative structure relationship models, i.e. QSAR and QSPR, have a huge potential to improve the pesticide risk assessment process. In this sense, these non-animal test methods can promote the competitiveness of agriculture in this region: the consumer safety is increased with them due to the possibility of perform an overall better risk assessment of the degradation products and metabolites from pesticides. However, the use of theses computational-based (in silico) tools must be much more systematised and harmonised, improving their validation and including case studies to test them. To open databases, incorporating critical data in an orderly manner for building the models, becomes also necessary. Moreover, quantum chemistry through the Density Functional Theory should be promoted as tool for calculation of quantum descriptors, especially for the study of similar compounds with the same carbon skeleton but differing substitution patterns, e.g. isomers.

A Summary Report of FSCJ Workshop "Future Challenges and Opportunities in Developing Methodologies for Improved Human Risk Assessments"

This is a summary report of FSCJ (Food Safety Commission of Japan) workshop entitled "Future Challenges and Opportunities in Developing Methodologies for Improved Human Risk Assessments, which held in November 2018. Scientific advancements have facilitated the development of new methods for chemical risk assessments with the expansion of toxicological databases. They are promising tools to overcome challenges, such as situations of data insufficiency, estimation of internal exposure and prediction of hazard, and enable us to improve our human health risk assessment in food safety. In this review, current understandings on developments in chemical risk assessments, especially focusing on Threshold of Toxicological Concern (TTC) approach, non-testing and in-silico approaches (e.g. read-across), and physiologically based pharmacokinetics (PBPK) modeling are discussed as possible promising tools. It also discusses future challenges and opportunities regarding social environment buildings in which all stakeholders including scientific experts, risk managers and consumers are able to accept these new risk assessment technologies. International collaboration would increase and enhance the efficiency in forming innovative ideas and in translating them into regulatory practices. It would strengthen technical capacity of experts who contribute to regulatory decisions and also promote acceptance of new methodologies among stakeholders. Cross-sectional collaboration such as making good use of human data of pharmaceutical drugs will facilitate a development of fresh tools for food safety domains. Once a new methodology is recognized in risk assessment agencies as implementable, it needs to be acknowledged and accepted by wider range of different stakeholders. Such stakeholders include scientific experts who conduct risk assessment for the risk assessment agencies, food industries and consumers. Transparency in the risk assessment work performed by regulatory agencies should strengthen their credibility and promote the acceptance of risk assessment including the new methodologies used in it. At the same time, efforts should be continued by regulatory agencies to further communicate with consumers about the concept of risk-based assessment as well as the concept of uncertainty.

High-resolution accurate mass spectrometry as a technique for characterization of complex lysimeter leachate samples

Lysimeter studies can be used to identify and quantify soil degradates of agrochemicals (metabolites) that have the potential to leach to groundwater. However, the apparent metabolic profile of such lysimeter leachate samples will often be significantly more complex than would be expected in true groundwater samples. This is particularly true for S-metolachlor, which has an extremely complex metabolic pathway. Consequently, it was not practically possible to apply a conventional analytical approach to identify all metabolites in an S-metolachlor lysimeter study, because there was insufficient mass to enable the use of techniques such as nuclear magnetic resonance. Recent advances in high-resolution accurate mass spectrometry, however, allow innovative screening approaches to characterize leachate samples to a greater extent than previously possible. Leachate from the S-metolachlor study was screened for accurate masses (±5 ppm of the nominal mass) corresponding to more than 400 hypothetical metabolite structures. A refined list of plausible metabolites was constructed from these data to provide a comprehensive description of the most likely metabolites present. The properties of these metabolites were then evaluated using a principal component analysis model, based on molecular descriptors, to visualize the entire chemical space and to cluster the metabolites into a number of subclasses. This characterization and principal component analysis evaluation enabled the selection of suitable representative metabolites that were subsequently used as exemplars to assess the toxicological relevance of the leachate as a whole. Environ Toxicol Chem 2016;35:1401-1412. © 2015 SETAC.

Mutagenic impurities in pharmaceuticals: a critique of the derivation of the cancer TTC (Threshold of Toxicological Concern) and recommendations for structural-class-based limits

The cancer TTC (Threshold of Toxicological Concern) concept is currently employed as an aid to risk assessment of potentially mutagenic impurities (PMIs) in food, cosmetics and other sectors. Within the pharmaceutical industry the use of one default cancer TTC limit of 1.5 μg/day for PMIs is being increasingly questioned. Its derivation, originally in the context of foodstuffs, can be broken down into five key elements: dataset composition; determination of carcinogenicity/mutagenicity status and carcinogenic potency (based on TD₅₀s) of compounds in the dataset; linear extrapolation of carcinogenic potencies; evaluation of the more potent compounds in each structural category, and presence of representative structural alerts amongst the more potent compounds. A detailed evaluation reveals that the derivation process is distorted by the use of the lowest statistically significant TD₅₀s (which can produce a false-carcinogen phenomenon) and by employing linear extrapolation for non-mutagenic carcinogens. By correcting for these two factors, it is concluded that only around 50% of conventional structural-alert categories were adequately addressed and that limits higher than the default value appear to be justified in many cases. Using similar criteria for PMIs in pharmaceuticals, four distinct potency categories of conventional structural alerts can be distinguished, ranging from alerts with questionable validity to those with high potency, which are considered to provide a range of flexible and pragmatic limits for such impurities.

Regulatory Forum Opinion Piece*

The advancement of technology and the growth of international commerce underscore the need for global harmonization of regulatory safety requirements and their assessment pertaining to consumer products such as drugs, medical devices, and food. This need is particularly relevant when safety requirements involve time-intensive and costly animal safety studies. Here we present the current regulatory requirements in Europe, the United States, and Japan for flavoring substances (FSs) used in foods and point out significant differences relevant to the international standardization for safety assessments that in our opinion need to be addressed and overcome. The safety assessments that are carried out for FSs in various countries are influenced by divergent definitions of FS, by the information required and available for regulatory submission, and by different regulatory procedures, including the use of decision tree approaches. The European Food Safety Authority (EFSA), the Expert Panel of the U.S. Flavor and Extract Manufacturers Association (FEMA), and the Joint Food and Agriculture Organization (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) are making efforts to improve and harmonize the safety assessment of FSs. The application of in silico methods such as quantitative structure–activity relationships and read-across strategies relying on expert input are useful as a first-step screening of the assessment. Application of the Threshold of Toxicological Concern (TTC) approach permits conclusions that are compatible with the risk assessment approaches currently used by international advisory committees.

The Japanese Regulatory Authority, on the other hand, does not yet consider in silico methods but still requires in vivo and in vitro genotoxicity test data as well as repeat-dose 90-day toxicity data in at least one species, to be submitted as the first step in the safety assessment of FSs. With this article, we echo requests that have been made for xenobiotics by the pharmaceutical industry worldwide, extending them to food-related products, especially FSs. We encourage regulatory agencies to adopt globally harmonized safety assessment procedures, regulatory guidelines, and review practices for FSs to foster global trade and to reduce costs and laboratory animal use.

Application of the threshold of toxicological concern concept when applied to pharmaceutical manufacturing operations intended for short-term clinical trials

In the manufacture of pharmaceuticals, if a multiproduct facility shares equipment amongst drug substances/products it is incumbent upon the manufacturer to demonstrate removal of the pharmaceutical through a robust cleaning validation/verification program. Removal must be to below limits considered acceptable from a quality and toxicological perspective. In order to address the toxicological concerns, an acceptable daily exposure (ADE) was developed which is the "dose that is unlikely to cause an adverse effect if...exposed, by any route...at or below this dose every day for a lifetime" (ISPE, 2010). For compounds in development, defaulted ADEs were proposed by Dolan et al. (2005) and adopted by the International Society of Pharmaceutical Engineers (ISPE) as conservative cutoffs for compounds with limited data. In Phase 1 clinical trials, exposure is typically short-term (single dose or repeated doses for ≤30 days) compared to the chronic doses used to derive ADE and defaulted ADEs. An analysis of publicly available databases for toxicological and pharmacological effects supports the use of 10-fold higher defaulted values when the residual drug substance is in a developmental pharmaceutical intended for Phase 1 clinical trials (exposure ≤30 days).