Considerations for the Identification and Conveyance of Clinical Pathology Findings in Preclinical Toxicity Studies: Results From the 9th ESTP International Expert Workshop

The European Society of Toxicologic Pathology (ESTP) organized a panel of 24 international experts from many fields of toxicologic clinical pathology (e.g., industry, academia, and regulatory) that came together in 2021 to align the use of terminology to convey the importance of clinical pathology findings in preclinical toxicity studies. An additional goal consisted of how to identify important findings in standard and nonstandard clinical pathology associated endpoints. This manuscript summarizes the information and opinions discussed and shared at the ninth ESTP International Expert Workshop, April 5 to 6, 2022. In addition to terminology usage, the workshop considered topics related to the identification and conveyance of the importance of test item-related findings. These topics included sources of variability, comparators, statistics, reporting, correlations to other study data, nonstandard biomarkers, indirect/secondary findings, and an overall weight-of-evidence approach.

Enemies or Allies? Hormetic and Apparent Non-Dose-Dependent Effects of Natural Bioactive Antioxidants in the Treatment of Inflammation

This review aims to analyze the emerging number of studies on biological media that describe the unexpected effects of different natural bioactive antioxidants. Hormetic effects, with a biphasic response depending on the dose, or activities that are apparently non-dose-dependent, have been described for compounds such as resveratrol, curcumin, ferulic acid or linoleic acid, among others. The analysis of the reported studies confirms the incidence of these types of effects, which should be taken into account by researchers, discarding initial interpretations of imprecise methodologies or measurements. The incidence of these types of effects should enhance research into the different mechanisms of action, particularly those studied in the field of basic research, that will help us understand the causes of these unusual behaviors, depending on the dose, such as the inactivation of the signaling pathways of the immune defense system. Antioxidative and anti-inflammatory activities in biological media should be addressed in ways that go beyond a mere statistical approach. In this work, some of the research pathways that may explain the understanding of these activities are revised, paying special attention to the ability of the selected bioactive compounds (curcumin, resveratrol, ferulic acid and linoleic acid) to form metal complexes and the activity of these complexes in biological media.

An evaluation of the genotoxicity and 90-day repeated-dose toxicity of a CBD-rich hemp oil

Currently, there is much interest in the sales and study of consumable Cannabis sativa L. products that contain relatively high levels of cannabidiol (CBD) and low levels of Δ-9-tetrahydrocannabinol. While there are published safety evaluations for extracts containing low concentrations of CBD, toxicological assessments for those with higher concentrations are still scant in the public domain. In this paper, genotoxicity tests and a 90-day repeated-dose toxicity study of an ethanolic extract of C. sativa containing ~85% CBD were performed following relevant OECD guidelines. No increased gene mutations were observed in a bacterial reverse mutation assay compared to controls up to the maximum recommended concentration of the guideline. An in vitro chromosomal aberration assay showed no positive findings in the short-term (3 h) treatment assays. Long-term treatment (20 h) showed an increased number of cells containing aberrations at the highest dose of 2 μg/mL, which was outside of historical control levels, but not statistically significantly different from the controls. An in vivo micronucleus study showed no genotoxic potential of the test item in mice. A 90-day repeated-dose gavage study using 0, 75, 125, and 175 mg/kg bw/day showed several slight findings that were considered likely to be related to an adaptive response to consumption of the extract by the animals but were not considered toxicologically relevant. These included increases in liver and adrenal weights compared to controls. The NOAEL was determined as 175 mg/kg bw/day, the highest dose tested (equivalent to approximately 150 mg/kg bw/day of CBD).

Retrospective analysis of the potential use of virtual control groups in preclinical toxicity assessment using the eTOX database

Virtual Control Groups (VCGs) based on Historical Control Data (HCD) in preclinical toxicity testing have the potential to reduce animal usage. As a case study we retrospectively analyzed the impact of replacing Concurrent Control Groups (CCGs) with VCGs on the treatment-relatedness of 28 selected histopathological findings reported in either rat or dog in the eTOX database. We developed a novel methodology whereby statistical predictions of treatment-relatedness using either CCGs or VCGs of varying covariate similarity to CCGs were compared to designations from original toxicologist reports; and changes in agreement were used to quantify changes in study outcomes. Generally, the best agreement was achieved when CCGs were replaced with VCGs with the highest level of similarity; the same species, strain, sex, administration route, and vehicle. For example, balanced accuracies for rat findings were 0.704 (predictions based on CCGs) vs. 0.702 (predictions based on VCGs). Moreover, we identified covariates which resulted in poorer identification of treatment-relatedness. This was related to an increasing incidence rate divergence in HCD relative to CCGs. Future databases which collect data at the individual animal level including study details such as animal age and testing facility are required to build adequate VCGs to accurately identify treatment-related effects.

Statistical analysis of preclinical inter-species concordance of histopathological findings in the eTOX database

Preclinical inter-species concordance can increase the predictivity of observations to the clinic, potentially reducing drug attrition caused by unforeseen adverse events. We quantified inter-species concordance of histopathological findings and target organ toxicities across four preclinical species in the eTOX database using likelihood ratios (LRs). This was done whilst only comparing findings between studies with similar compound exposure (Δ|C_max| ≤ 1 log-unit), repeat-dosing duration, and animals of the same sex. We discovered 24 previously unreported significant inter-species associations between histopathological findings encoded by the HPATH ontology. More associations with strong positive concordance (33% LR+ > 10) relative to strong negative concordance (12.5% LR- < 0.1) were identified. Of the top 10 most positively concordant associations, 60% were computed between different histopathological findings indicating potential differences in inter-species pathogenesis. We also observed low inter-species target organ toxicity concordance. For example, liver toxicity concordance in short-term studies between female rats and dogs observed an average LR+ of 1.84, and an average LR- of 0.73. This was corroborated by similarly low concordance between rodents and non-rodents for 75 candidate drugs in AstraZeneca. This work provides new statistically significant associations between preclinical species, but finds that concordance is rare, particularly between the absence of findings.

Scientific and Regulatory Policy Committee Points to Consider: Integration of Clinical Pathology Data With Anatomic Pathology Data in Nonclinical Toxicology Studies

Integrating clinical pathology data with anatomic pathology data is a common practice when reporting findings in the context of nonclinical toxicity studies and aids in understanding and communicating the nonclinical safety profile of test articles in development. Appropriate pathology data integration requires knowledge of analyte and tissue biology, species differences, methods of specimen acquisition and analysis, study procedures, and an understanding of the potential causes and effects of a variety of pathophysiologic processes. Neglecting these factors can lead to inappropriate data integration or a missed opportunity to enhance understanding and communication of observed changes. In such cases, nonclinical safety information relevant to human safety risk assessment may be misrepresented or misunderstood. This "Points to Consider" manuscript presents general concepts regarding pathology data integration in nonclinical studies, considerations for avoiding potential oversights and errors in data integration, and focused discussion on topics relevant to data integration for several key organ systems, including liver, kidney, and cardiovascular systems.

Scientific and Regulatory Policy Committee Points to Consider: Integration of Clinical Pathology Data With Anatomic Pathology Data in Nonclinical Toxicology Studies

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High-grade glioma therapy: adding flexibility in trial design to improve patient outcomes

INTRODUCTION

Outcomes for patients with high grade gliomas have changed little over the past thirty years. This realization prompted renewed efforts to increase flexibility in the design and conduct of clinical brain tumor trials.

AREAS COVERED

This manuscript reviews the development of clinical trial methods, challenges and considerations of flexible clinical trial designs, approaches to improve identification and testing of active agents for high grade gliomas, and evaluation of their delivery to the central nervous system.

EXPERT OPINION

Flexibility can be introduced in clinical trials in several ways. Flexible designs tout smaller sample sizes, adaptive modifications, fewer control arms, and inclusion of multiple arms in one study. Unfortunately, modifications in study designs cannot address two challenges that are largely responsible for the lack of progress in treating high grade gliomas: 1) the identification of active pharmaceutical agents and 2) the delivery of these agents to brain tumor tissue in therapeutic concentrations. To improve the outcomes of patients with high grade gliomas efforts must be focused on the pre-clinical screening of drugs for activity, the ability of these agents to achieve therapeutic concentrations in non-enhancing tumors, and a willingness to introduce novel compounds in minimally pre-treated patient populations.

Enhancing Student Learning by Integrating Anatomy in Pathology Teaching

BACKGROUND

Vertically integrating anatomy into pathology curricula is beneficial for student-centered learning. This study investigates the effectiveness of this approach on student learning outcomes.

ACTIVITY

Learners received a vertically integrated pathology curriculum; their pre- and post-course test data were collected.

RESULTS AND DISCUSSION

Two-hundred thirty-two learners participated in the activity. Upon completing the activity, their average post-course performance was significantly better than that of a control group (P < 0.05), with significantly higher scores on solving pathology case problems (P < 0.05), as well as on retaining anatomy concepts (P < 0.05). Vertically integrating anatomy in pathology instruction is an effective educational approach.

Evaluation of the toxic potential of the aqueous extract from Mangifera indica Linn. (Anacardiaceae) in rats submitted to experimental models of acute and subacute oral toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

The population has traditionally used the Mangifera indica plant leaves to treat diseases such as Diabetes Mellitus and alleviate signs and symptoms such as inflammation, diarrhea, and dysentery. In a previous study, we demonstrated that the flavonoids present in the aqueous extract from M. indica leaves (EAMI) exhibited a potent hypoglycemic effect in diabetic rats, promoting the widespread use of the plant by the population and highlighting the importance of investigating its oral toxicity.

AIM OF THE STUDY

The present study aimed to assess the toxic potential of EAMI in rats submitted to experimental models of acute and subacute (short-term) oral toxicity.

MATERIAL AND METHODS

For the acute toxicity test, female Wistar rats received a single oral dose of 2000 mg/kg body weight of EAMI and were observed for 14 days. In the short-term toxicity test, male and female Wistar rats received repeated oral EAMI doses of 125, 250, 500 or 1000 mg/kg body weight and observed for 28 days.

RESULTS

The phytochemical analysis of EAMI demonstrated that the extract has high levels of flavonoids. No animals died in the acute toxicity test, and no clinical changes were observed that show signs of toxicity in the animals. There was no significant change in the weight of the organs of the animals submitted to tests with the EAMI, suggesting that LD50 is greater than 2000 mg/kg. In the conditions and doses tested in the short-term toxicity experiments, the treatment did not produce significant changes in the physiological, biochemical, hematological, and histopathological parameters in the animals evaluated.

CONCLUSIONS

Our study demonstrated that high doses of EAMI administered acutely, as well as all doses evaluated in the short-term oral toxicity model, should be considered safe during traditional therapeutic use.

Selected Aspects of Ocular Toxicity Studies With a Focus on High-Quality Pathology Reports: A Pathology/Toxicology Consultant's Perspective

Ocular toxicity studies are the bedrock of nonclinical ocular drug and drug-device development, and there has been an evolution in experience, technologies, and challenges to address that ensures safe clinical trials and marketing authorization. The expectations of a well-designed ocular toxicity study and the generation of a coherent, integrative ocular toxicology report and subreports are high, and this article provides a pathology/toxicology consultant's perspective on achieving that goal. The first objective is to cover selected aspects of study designs for ocular toxicity studies including considerations for contract research organization selection, minipig species selection, unilateral versus bilateral dosing, and in-life parameters based on fit-for-purpose study objectives. The main objective is a focus on a high-quality ocular pathology report that includes ocular histology procedures to meet regulatory expectations and a report narrative and tables that correlate microscopic findings with key ophthalmic findings and presents a clear interpretation of test article-, vehicle-, and procedure-related ocular and extraocular findings with identification of adversity and a pathology peer review. The last objective covers considerations for a high-quality ophthalmology report, which in concert with a high-quality pathology report, will pave the way for a best quality toxicology report for an ocular toxicity study.

Nonclinical Immunotoxicity Testing in the Pharmaceutical World: The Past, Present, and Future

An examination for potential direct or indirect adverse effects on the immune system (immunotoxicity) is an established component of nonclinical testing to support safe use of new drugs. Testing recommendations occur in various regulatory guidance documents, especially ICH S8, and these will be presented. Key evaluation usually occurs in toxicology studies with further investigative work a consideration if a positive signal is seen. Expectations around whether findings may occur are related to the type of compound being developed, including a chemically synthesized small molecule, a small molecule oncology drug, a biopharmaceutical, an oligonucleotide, a gene therapy/stem cell product, a vaccine, or reformulation of drugs in liposomes or depots. Examples of immunotoxicity/immunogenicity findings will be discussed for all of these types of compound. Overall, it can be concluded that our main tool for evaluation of potential immunotoxicity/immunogenicity for a new drug still remains standard toxicology study testing with key assessment for effects on clinical pathology and lymphoid organs/tissues (weights and cellularity). Additional evaluation from studies using a T cell-dependent antibody response (TDAR) and lymphocyte phenotyping is also valuable, if needed. Thus, using the tools from the past, it is the role of toxicologists to work with clinical teams now and in the future, to interpret findings from nonclinical testing to possible adverse findings in humans.

Curation and analysis of clinical pathology parameters and histopathologic findings from eTOXsys, a large database project (eTOX) for toxicologic studies

Large data sharing projects amongst the pharmaceutical industry have the potential to generate new insights using data on a scale that has not been previously available. A retrospective analysis of the preclinical toxicology data collected as part of the eTOX project was conducted with the aim to provide background rates and treatment-related value analysis on both clinical pathology and histopathology datasets. Incorporated into this analysis was an extensive data consolidation task to standardise all data. Reference intervals for common clinical pathology parameters in rat and dog were generated, alongside background histopathology incidence rates in the liver, heart and kidney. Systematically applied decision thresholds allowed consistent relabelling of data points considered anomalous, and maximum fold change estimates. Relabelling of anomalous data points was conducted for the histopathology data using a Bayesian model to identify dose-dependent increases in pathologies. The results of this study allow: newly generated data to be analysed using the same methodology, rates and distributions to be used when building predictive dose-response models, and the possibility to correlate clinical pathology findings with concurrent histopathology findings. In the first half of this paper we discuss data curation, in the second half we report on the analytical methods and results.