Toxicologic Pathology Forum*: Opinion on the Interpretation of Statistical Significance Testing Results From Anatomic and Clinical Pathology Data in Nonclinical Safety Studies

Toxicologic pathologists assess large data sets from nonclinical studies to identify treatment-related effects to assist in predicting human safety hazards. Statistical testing can facilitate data interpretation by highlighting group differences that have a low probability of random occurrence based on a pre-determined P-value cut-off (eg, P < .05). While this method has been used in the interpretation of pathology data for decades, the appropriateness of utilizing statistical testing in this way has been challenged. Here, we discuss common statistical pitfalls in the analysis of toxicologic pathology data, with emphasis on clinical pathology, reaffirming that appropriate use of statistical analysis requires an understanding of (1) the parameters assessed; (2) the inherent strengths and weaknesses of the statistical method used; and (3) that appropriate interpretation of pathology data is based on the pathologist's expertise. The presence or absence of statistical significance should not supersede expert judgment but should be one of many tools used to reach a conclusion.

European Food Safety Authority (EFSA), Castoldi AF, Coja T, Lanzoni A, Machera K, Mohimont L, Recordati C, Crivellente F. Specific effects on kidneys relevant for performing a dietary cumulative risk assessment of pesticide residues

In consistency with the 'EFSA-SANTE Action Plan on Cumulative Risk Assessment for pesticides residues' EFSA initiated a retrospective cumulative risk assessment (CRA) of the effects of pesticide residues on the kidneys. EFSA identified the following specific effects on kidneys of relevance for cumulative risk assessment: glomerular injury, tubular injury, tubular crystals, papillary necrosis, interstitial nephritis, pelvis erosion/ulceration, pelvis calculi/crystals, renal preneoplastic and neoplastic lesions, and pelvis preneoplastic and neoplastic lesions. A list of histological indicators was defined and will be used to collect information on these specific effects, as reported in the assessment reports of the different active substances used as plant protections products. The criteria for inclusion of active substances/metabolites into cumulative assessment groups (CAGs) were also defined, together with the hazard characterisation methodology and the lines of evidence for assessing CAG-membership probabilities. Since no acute CAGs for kidney effects are considered appropriate, the cumulative dietary risk assessment will focus on chronic exposure only. The process of data extraction and establishment of the CAGs is beyond the scope of this report. This part of the CRA process was outsourced and will be the subject of a separate report.

Implementing exposure limits for players in contact team sports: review of principles and practices

Concerns have been raised that professional athletes taking part in contact team sports, such as football and rugby union, are subject to the risk of post-career adverse health conditions. These health concerns include neurodegenerative diseases resulting from head impacts and osteoarthritis in lower limb joints due to wear and tear. There have been suggestions that athletes in contact team sports should be subject to exposure limitations to mitigate these risks. At the present time, little information or guidance is available for athletes and sport governing bodies about how such limitations should be identified and implemented. The criteria used for defining occupational health concerns and the role and nature of occupational exposure limits are discussed. Consideration is given to whether these criteria have been considered and embraced in research studies examining adverse health conditions in professional sport. Recommendations are presented for how future research studies investigating post-career, sport-related, adverse health concerns should be planned and implemented in order to provide the occupational health information required to make evidenced-based decisions about potential health concerns in professional sport.

European Food Safety Authority (EFSA), Castoldi AF, Coja T, Lanzoni A, Machera K, Mohimont L, Nepal M, Recordati C, Crivellente F. Specific effects on liver relevant for performing a dietary cumulative risk assessment of pesticide residues

According to the 'EFSA-SANTE Action Plan on Cumulative Risk Assessment for pesticides residues', EFSA initiated a retrospective cumulative risk assessment (CRA) of the effects of pesticide residues on the liver. For this CRA, EFSA identified the following liver-specific effects in accordance with the International Harmonisation of Nomenclature and Diagnostic Criteria (INHAND): (1) hypertrophy due to enzymatic induction, liver; (2) fatty change and/or phospholipidosis, hepatocellular; (3) degeneration/cell death, hepatocellular; (4) porphyria, hepatocellular, biliary duct; (5) cholestasis, hepatocellular, biliary duct; (6) preneoplastic and neoplastic changes, hepatocellular; (7) neoplastic changes, biliary duct. In addition, as gallbladder is part of the extrahepatic biliary system and can be affected by hepatic toxicity, the following specific effects in the gallbladder were defined: (1) erosion/ulceration, gallbladder (2) calculi, gallbladder and (3) neoplastic changes, gallbladder. Histopathology was considered as the most appropriate source of evidence together with the increase in relative liver weight, and a list of indicators was defined and will be used to collect information on these specific effects as included in the assessment reports of the different active substances used as plant protection products. The criteria for inclusion of active substances/metabolites into cumulative assessment groups (CAGs) were also defined, together with the hazard characterisation methodology and the lines of evidence for assessing CAG-membership probabilities. While primary indicators define the specific effect, secondary indicators and other endpoints (named ancillary endpoints) are considered not sufficiently informative to indicate a specific effect but are rather contributing to the overall evidence; these will be collected only for a limited number of substances (i.e. risk drivers based on hazard and exposure considerations) for determining the likelihood of the substances truly belonging to the CAGs (CAG-membership probabilities). Considering that it is not considered appropriate to establish CAGs for acute liver effects, CRAs on the liver will be only focused on chronic exposure. The process of data extraction and actual establishment of the CAGs is beyond the scope of this report. This part of the CRA process was outsourced and will be the subject of a separate report.

Suberosin attenuates rheumatoid arthritis by repolarizing macrophages and inhibiting synovitis via the JAK/STAT signaling pathway

BACKGROUND

Rheumatoid arthritis (RA) is a systemic disease that primarily manifests as chronic synovitis of the symmetric small joints. Despite the availability of various targeted drugs for RA, these treatments are limited by adverse reactions, warranting new treatment approaches. Suberosin (SBR), isolated from Plumbago zeylanica-a medicinal plant traditionally used to treat RA in Asia-possesses notable biological activities. This study aimed to investigate the effects and potential underlying pathways of SBR on RA.

METHODS

Tumor necrosis factor-alpha (TNF-α) induced inflammation in RA-derived fibroblast-like synoviocytes (RA-FLS), and the expression of proinflammatory mediators was assessed using q-RT PCR and ELISA after treatment with various SBR concentrations. Bone marrow-derived macrophages (BMDMs) were induced to differentiate into M1 and M2 macrophages, followed by treatment with various SBR concentrations and macrophage polarization assessment. Low-dose (0.5 mg/kg/d) and high-dose (2 mg/kg/d) SBR regimens were administered to a collagen-induced arthritis (CIA) mouse model for 21 days, and the anti-arthritic effects of SBR were evaluated. Network pharmacology and molecular docking analyses were used to predict the anti-arthritic targets of SBR. The effect of SBR on the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway was evaluated.

RESULTS

SBR suppressed macrophage polarization toward the M1 phenotype while enhancing their polarization toward the M2 phenotype. SBR reduced the levels of proinflammatory mediators in TNF-α-induced RA-FLS. Mechanistically, SBR inhibited the phosphorylation of the JAK1/STAT3 signaling pathway in RA-FLS and M1 macrophages and promoted the phosphorylation of the JAK1/STAT6 pathway in M2 macrophages, enhancing M2 polarization. In vivo, prophylactic treatment of low-dose SBR reduced M1 macrophage infiltration into synovial tissue, increased the proportion of M2 macrophages, and decreased the expression of inflammatory mediators in the serum and synovial tissue, alleviating synovial inflammation. SBR significantly alleviated arthritis in CIA mice through macrophage repolarization and inhibition of inflammation.

CONCLUSION

SBR significantly reduced clinical symptoms, joint pathological damage, and expression inflammatory cytokine expression in CIA mice. SBR exhibited anti-arthritic effects via the JAK1/STAT3 and JAK1/STAT6 signaling pathways, inhibiting synovial tissue inflammation and M1 macrophage polarization while promoting M2 macrophage polarization. Therefore, SBR may be an effective candidate for RA treatment.

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.