A World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Framework outlines a pragmatic approach to the identification and consideration of priorities in the grouping and assessment of combined exposures to multiple chemicals. The Framework includes formal problem formulation followed by step wise consideration of both exposure and hazard in several tiers of increasingly data-informed analyses. These analyses build on recent developments in assessment, incorporating predictive approaches in early tiers and increasingly refined, more data-informed mode of action and probabilistic analyses in later tiers.
Recently, the Framework has been additionally developed in a number of initiatives in both research and application, including guidance of the Organization for Economic Cooperation and Development and the European Food Safety Agency, the development of tools within the European Horizon 2020 Research Project, Euromix and a recent WHO Publication on Chemical Mixtures in Source and Drinking Water.
The Framework also serves as an organizing construct for a “Roadmap” for methodological guidance on chemical risk assessment of the WHO/IPCS Harmonization Initiative. This Roadmap provides the basis for practical advice for the implementation of these various methodologies in tiered assessment and management strategies.
Tiered assessment incorporating methodological advances internationally will be illustrated through presentation of examples and case studies. The implications of increasing international experience in tiered assessment incorporating new and evolving methods will also be addressed.
Per- and Polyfluoroalkyl Substances (PFAS) are a group of synthetic substances that were originally developed in the late 1940s for uses as surfactants and surface protectors. The term PFAS includes both polymeric and non-polymeric fully (per-) and partially (poly-) fluoroalkyl substances. The most well studied PFAS are perfluorooctanoic acid (PFOA), a Substance of Very High Concern (SVHC) as designated by the European Union, and perfluorooctane sulfonate (PFOS). Contemporary uses include industrial applications such as polymeric non-stick coatings on cookware, cosmetics, fabric protectors, waxes, paint and firefighting foams. PFAS have made their way into the biosphere in all continents. Some, including PFSAs and PFCAs, are especially persistent due to their strong carbon-fluorine bonds. Due to growing evidence of bioactivity, public health guidance is being developed in numerous countries to limit human exposures through drinking water and food. Also included as PFAS are perfluoroalkanes, other perfluoroalkyl sulfonic acids (PFSA) and perfluoroalkyl carboxylic acids (PFCA), and recently described perfluoroalkyl ether carboxylic acids (PFECA) and sulfonic acids (PFESA), among other proposed subclasses. Information is rapidly emerging on PFAS chemical classification and grouping, environmental chemistry, detection technology, fate and transport, exposure potential, human health toxicity, and ecological toxicity. This presentation will review recent social and public health actions regarding PFAS exposure and toxicity.
Gene therapy can be defined as the introduction of nucleic acids into a host cell to result in the replacement or inactivation of a mutated gene, or to introduce something novel. The introduction of the nucleic acids can occur inside or outside of the body, often with the use of a viral vector, such as adeno-associated viruses (AAV). In the past several years, there has been a dramatic increase in the use of gene therapies to develop potential therapies for treating various diseases. However, there are multiple challenges associated with this relatively novel technique; such as antibody or cell mediated responses that limit efficacy, lack of data on the long term safety, and an evolving regulatory environment that establishes the requirements for drug development of gene therapies. This presentation will provide an overview of gene therapy, review the key aspects of the available nonclinical regulatory guidance, discuss things to consider when developing an nonclinical toxicology strategy, and examine case studies of nonclinical packages used for the development of novel therapies.
Much attention in toxicology has been given to the biotransformation of chemicals and the mechanism of action of toxicants. However, the toxicity of chemicals is also dependent upon the ability to adapt to the presence of the toxicant. One mechanism for adaptation to chemicals that his been examined in detail is the induction of the cytochrome P-450s (CYPs). However, while the induction of the CYPs will increase the biotransformation of many chemicals to less toxic products and results in adaptation, but for other chemicals the CYPs metabolize them to more toxic products and results in more toxicity. These same chemicals that induce the CYPs can also induce uptake and efflux transporters, which have the ability to also adapt cells to the presence of some chemicals, which will be addressed in this lecture. A second mechanism to be discussed is the adaptation to chemicals by the induction of metallothionein (MT). MT is a small protein that is made up of 1/3 cysteines and avidly binds metals such as zinc and cadmium. It is one of the most inducible proteins and plays in a major role in the adaptation to cadmium toxicity. The third mechanism of adaptation to be discussed is the Nrf2-Keap1 transcription factor induction of a plethora of enzymes and transporters that protect against numerous chemicals whose mechanism of toxicity is via electrophiles and oxidative stress. These and other mechanisms of adaptation play a major role in protecting us from the toxicity of chemicals.
医薬品開発における生殖発生毒性評価はサリドマイド事件を契機として大きく変わり、催奇形性評価においてラットとウサギの2種を用いることなどが義務付けられた。その後、いわゆる三節生殖発生毒性試験法が制定され、さらに医薬品規制調和国際会議（ICH）により毒性試験法の国際的な調和が飛躍的に進んだ。その結果、生殖発生毒性を評価する試験方法については、いわゆるICHガイドラインである「医薬品の生殖発生毒性試験法ガイドライン」（以下、ICHS5GL (R2)）が発出され、その後はこのICHS5GL(R2)に準じた非臨床試験が実施されてきた。それから15年余の歳月を経て、2015年にICHS5GL(R2)を全面改定するためのExpert Working Group (EWG)が結成され、約4年半の改定作業を経て、2020年にICH S5GL(R3)としてStep4に到達した。
一方、2013年に妊娠中の染色体異常に対する出生前検査としてnoninvasive prenatal test (NIPT)が開始された。NIPTは妊娠10週から検査可能な、非常に精度の高いスクリーニングである。そして妊娠女性からの採血検体で実施できる簡便さと、胎児に対しての非侵襲性により、非常に大きな話題となった。その為、出生前検査として受検を希望する妊婦が多く、NIPT認可施設のみでは全ての希望する妊婦に対応できない状況となっている。しかし、医学的な根拠を元に、妥当性のあるNIPTの対象となっている染色体異常は13トリソミー、18トリソミー、21トリソミーのみであり、これは先天性疾患のうちの一部である。
As a base of safety assessment of pharmaceuticals, the initial data management requires accurate toxicological data acquisition, which is based on regulatory safety studies according to guidelines, and computational systems have been developed under the application of GLP. In addition to these regulatory toxicology studies, investigative toxicological study data for the selection of lead compound and candidate compound for clinical trials are directed to the estimation by computational systems such as QSAR and related expert systems.
Furthermore, in the “Go”, “No-Go” decision of drug development, supportive utilization of a scientifically interpretable computational toxicology system is required for human safety evaluation. Pharmaceutical safety evaluator as a related toxicologist who is facing to practical decision does not need a data-driven AI (Artificial Intelligence) system that calls for the final consequence, rather requires an explainable AI that can provide comprehensive information necessary for evaluation and can help decision making. Through the explication and suggestion of information on the mechanism of toxic effects to safety assessment scientists, ultimately a subsidiary partnership system for risk assessment is to be a powerful tool that can indicate project-vector with data weight for the corresponding counterparts.
To bridge the gaps between the big-data and the knowledge, multi-dimensional thinking based on philosophical ontology theory is necessary to handle heterogeneous data such as interpretable computational toxicology related to drug safety assessment.
Development of cancer immunotherapeutics creates some unique challenges for nonclinical safety assessment. These can range from lack of pharmacological activity in standard toxicology models to exaggerated pharmacology that can be dose limiting. This presentation will describe two case studies, one checkpoint inhibitor (atezolizumab) and one T cell dependent bispecific (CD20/CD3 TDB), to serve as an example of each scenario. Furthermore, nonclinical regulatory guidances and strategies to support clinical combinations containing cancer immunotherapeutics will be discussed.
Micro-electrode array (MEA) assay using human iPSC-derived neurons are expected to one of in vitro assessment to predict the toxicity and predict the mechanism of action of chemical compounds. However, the analytical method that can predict the toxicity from MEA data are not established. In this study, we attempted to detect the risk ranking of pesticides from MEA data in cultured human iPSC-derived neurons. Human iPSC-derived neurons (Neucyte inc.) were cultured on Micro-electrode array (MEA) plate, and 15 pesticides were tested at 5 concentrations from 0.01 to 100μM. Using multivariate analysis of parameters for synchronized burst firings, we have succeeded in distinguishing the dose-dependent responses to pesticides into low, middle, and high risk. In addition, we found that deep learning using the divvied image data of raster plots can separate dose-dependent responses into low, middle, and high risk. Although there is a problem of in vitro to in vivo extrapolation, analytical methods using multivariate analysis and deep learning are useful for the detection of risk ranking of pesticides from MEA data in cultured hiPSC-derived neuronal networks.
Drug-induced liver injury (DILI) can cause hepatic failure and result in drug withdrawal from the market. Preclinical prediction of DILI risk is very challenging and safety assessments based on animals inadequately forecast human DILI risk. In contrast, human-derived in vitro cell culture-based models could improve DILI risk prediction accuracy. Here, we developed and validated a method to assess DILI risk associated with various compounds. Fifty-four marketed and withdrawn drugs classified as DILI risks of “most concern”, “less concern”, and “no concern” based on Liver Toxicity Knowledge Base were tested using a combination of four assays addressing mitochondrial injury, intrahepatic lipid accumulation, inhibition of biliary network, and bile acid-dependent toxicity. Using these in vitro testings, an algorithm with the highest available DILI risk prediction power was built by artificial neural network (ANN) analysis. The optimal combination of assays (or descriptors in general) may not yet be achieved, but the strategy we employed here may be one of the strategies to predict DILI risk whose precise pathogenesis is unknown.
Regarding the in vivo drug-induced toxicity, the production of reactive metabolite (s) is considered to be an initiation reaction for both intrinsic- and idiosyncratic-type of toxicity. GSH content in kidney, heart and muscle is much lower than in liver, lung and spleen in normal rodents. GSH levels in the kidneys and muscles decrease rapidly by drug administration and recover slowly. A series of animal models that have established and utilized for drug-induced toxicity by reducing the scavenge ability by administering GSH synthase inhibitor L-buthionine-(S, R)-sulfoximine (BSO) to experimental animals will be introduced. (1) BSO was administered to normal mice for 7 days, an acute kidney injury model was established, and this model was able to detect the renal damage of the drug with high sensitivity. (2) A mouse model of rhabdomyolysis was established using a combination of a new quinolone antibiotic and a statin and a combination of a fibrate and a statin. This required the use of BSO, and became a test system that could assess the risk of drug-interaction with statins. (3) In the liver injury model in mice, the involvement of immune/inflammation-related factors is clear, but in rats it is unclear and liver damage is unlikely to occur. Therefore, in rats, combined use of BSO is necessary to induce liver injury. (4) GSH-conjugation of acyl glucuronide metabolites was inhibited by BSO, indicating that acyl glucuronide metabolites were involved in vivo in renal injury. Although there are still unclear about idiosyncratic drug-induced organ damage in humans, information from in vivo animal models will be useful for future research.
Drug-induced lung injury is defined as a lung injury that results from the specific use of a drug including over-the-counter drugs, herbal medicines, supplements, and illegal narcotics. Drug-induced interstitial lung disease that is one of the most common types of drug -induced lung injury occasionally causes fatal outcome. Recent anti-cancer drugs, such as tyrosine kinase inhibitors, immune checkpoint inhibitors and antibody drug conjugates, are not only highly effective for tumors but also common causative medications of drug induced interstitial lung disease. Pathogenetic mechanisms of drug induced interstitial lung disease have not been well known but direct toxic effects on alveolar type I epithelial cells, airway epithelial cells, or vascular endothelial cells and activation immune cells as a hapten or an antigen are suspected one of the pathogenetic mechanisms. Radiological and pathological patterns are classified based on the morphologic patterns of idiopathic interstitial pneumonia, hypersensitivity pneumonitis and sarcoidosis and so on. These patterns are not specific and different with each case. But these patterns are useful to differentiate drug induced interstitial lung disease from other lung diseases and identify diffuse alveolar damage pattern as a poor prognostic factor. In this presentation, radiological/pathological findings of drug induced pneumonitis and clinical significance of the morphologic patterns will be reviewed.
Drug-induced lung injury (DLI) in cancer patients is a possibility with almost all anticancer drugs, including cytotoxic anticancer drugs, molecular targeted agents, and immune checkpoint inhibitors. Although the precise mechanisms involved in DLI are not fully understood, it is thought to be caused by direct toxicity to pulmonary tissue and/or immune-mediated effects. Furthermore, this condition is influenced by various host and environment factors. The risk factors for the development of DLI are as follows: preexisting pulmonary lesions (interstitial lung disease / pulmonary fibrosis / chronic inflammatory diseases), hyperoxia, postoperative acute lung injury, combination therapy with anticancer drugs, radiation therapy, genetic factors, aging, or smoking. Although preclinical safety studies indicated no evidence of injury to intact lungs, some clinical cases showed DLI. Furthermore, despite the observation of immune-related adverse events (irAEs) in animal models, the quality and quantity of irAEs in clinical, including prediction of target organs, has not been fully established. In this presentation, I will outline pathological features and issues affecting various preclinical lung injury models, and then introduce preclinical evaluations of DLI using the bleomycin-induced lung injury model. In addition, translational issues, which is the problem of difference between preclinical and clinical, will be discussed.
Trastuzumab deruxtecan (T-DXd; DS-8201) is a HER2-targeting antibody-drug conjugate composed of a humanized anti-HER2 antibody and an exatecan derivative (DXd), a topoisomerase I inhibitor, which are bound together by a cleavable peptide-based linker. Before clinical trials, 6-week toxicity studies (every 3 weeks totaling 3 doses) with T-DXd were conducted in cynomolgus monkeys (cross-reactive species) and in rats (non cross-reactive species). The major target organs/tissues in rats and monkeys were the intestines and bone marrow. This effect seemed to be attributable to the cytotoxic effects of DXd and typical dose-limiting factors in the clinical use of topoisomerase I inhibitors. T-DXd caused pulmonary toxicity in monkeys at ≥ 30 mg/kg, although it was not observed in rats. In a 3-month monkey toxicity study (T-DXd every 3 weeks for a total of 5 doses), pulmonary toxicity was observed at 30 mg/kg (the highest dose). An extended dosing period did not increase the severity of lesions. While comprehensive mechanisms of the pulmonary toxicity remain unclear, this finding in monkeys could be relevant to the understanding of mechanism of interstitial lung disease (ILD) in patients treated with T-DXd. In this presentation, nonclinical toxicity data are reviewed with an emphasis on relevant safety findings.
数理モデルを用いた薬物体内動態の定量的解析は医薬品開発の一環としてごく普通に行われるようになってきた。さらに近年、ヒト血流および臓器体積等の生理・解剖学的パラメータを直接用いる生理学的薬物速度論（PBPK）モデルを用いた薬物体内動態解析が急速な進歩をみせている。PBPKモデルを構成する個々のパラメータは、生理学的・生化学的に対応付けられた意味を必ず持っており、これらのパラメータ値は、遺伝子多型、民族、性別、単純な個体差等に起因してヒト個体間で一定のばらつきがあることは自明である。時にそのばらつきの集積は、一定の患者集団の中でごく少数の患者のみにみられる予期せぬ薬物の血中濃度プロファイルや薬効・副作用発現につながり得る。そのような事象は、少人数を対象に行われる臨床試験初期においては検出が困難である。一方でPBPKモデルを構成するパラメータの個人間変動、すなわちばらつきの情報は健常人をはじめ蓄積されつつある。これら個人間変動の情報をPBPKモデルに組み込み、コンピュータ上で仮想患者を発生させシミュレーションすることにより、特定の患者集団における薬物の体内動態・薬効・副作用の発現頻度を定量的に予測できるVirtual Clinical Study (VCS)の実現が期待されている。本発表では、VCSによるアプローチが、実際のヒト臨床試験から得られる薬物動態・薬効・副作用を示すパラメータの平均値およびばらつきを再現するin silico予測系としての解析事例をいくつか紹介する。
In recent years, tetrodotoxin (TTX) has drawn international attention as a shellfish toxin. “Mouse Unit (MU)” has been used for a long period for evaluation of shellfish toxin in Japan; MU is determined by “Mortality” considering the lethal time in an acute toxicity study (ATS). On the other hand, EFSA has reported evaluation of TTX in which the “Apathy” was used as endpoint (EP) in an ATS. ATSs are also essential for classification and labeling of substances, but are criticized both scientific and ethical grounds; not to provide information on possible target organs and possible mechanisms of toxicity, and Mortality is not a desirable EP from the viewpoint of animal welfare. It is considered an excellent way to improve ATSs by accurately measuring and quantifying the signs of toxicity across multiple items and creating reasonable criteria for the acute toxicity of a substance. However, this will be a complicated and expensive test compared to ATSs, which uses Mortality as the endpoint. For modernization of ATSs, we are focusing on vital signs and wearable devices with cutting-edge sensors, furthermore, to consider validity of the vital signs for acute toxicity, comprehensive gene expression analysis of central nervous system was conducted. In other words, it is the development of a test method that obtains vital signs from animals corresponding to tests that human acutely poisoned patients undergo in emergencies. In this symposium, we would like to share the effect on central nervous system of TTX as a case evaluated by modernization of ATS.