Best practices for veterinary toxicologic clinical pathology, with emphasis on the pharmaceutical and biotechnology industries

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.

Polyclonal Peptide Antisera

Polyclonal antibodies are relatively easy to produce and may supplement monoclonal antibodies for some applications or even have some advantages.The choice of species for production of (peptide) antisera is based on practical considerations, including availability of immunogen (vaccine) and animals. Two major factors govern the production of antisera: the nature of adaptive immune responses, which take place over days/weeks and ethical guidelines for animal welfare.Here, simple procedures for immunization of mice, rabbits, sheep, goats, pigs, horses, and chickens are presented.

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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Improving the Quality of EDTA-treated Blood Specimens from Mice

Nonterminal blood sampling in laboratory mice is a very common procedure. With the goal of improving animal welfare, different sampling sites and methods have been compared but have not achieved a consensus. Moreover, most of these studies overlooked the quality of blood specimens collected. The main preanalytical concern with EDTA-treated blood specimens for hematology analyses is platelet aggregation, which is known to cause analytical errors. Our objective was to find a nonterminal blood sampling method with minimal adverse effects on mice and few or no platelet aggregates. We tested and compared 2 collection sites, 4 sampling methods, and 3 antithrombotic drugs in 80 C57BL6/j male and female mice by evaluating platelet aggregates on blood smears and platelet, WBC, and RBC counts. In addition, the blood collection process was carefully evaluated, and adverse effects were recorded. Platelet aggregation was lower in specimens collected from the jugular vein than from the facial vein, with no effect of the sampling device or the presence of an antithrombotic additive. Highly aggregated specimens were significantly associated with lower platelet counts, whereas aggregation had no effect on WBC or RBC counts. Adverse events during sampling were significantly associated with more numerous platelet aggregates. The jugular vein is thus a satisfactory sampling site in mice in terms of both animal welfare and low platelet aggregation. Using antithrombotic agents appears to be unnecessary, whereas improving sampling conditions remains a key requirement to ensure the quality of EDTA-treated blood specimens from mice.

Research-Relevant Clinical Pathology Resources: Emphasis on Mice, Rats, Rabbits, Dogs, Minipigs, and Non-Human Primates

Clinical pathology testing for investigative or biomedical research and for preclinical toxicity and safety assessment in laboratory animals is a distinct specialty requiring an understanding of species specific and other influential variables on results and interpretation. This review of clinical pathology principles and testing recommendations in laboratory animal species aims to provide a useful resource for researchers, veterinary specialists, toxicologists, and clinical or anatomic pathologists.

Reference value of hematologic, urologic, and organ weights of 2- to 4-year-old long-tailed macaques (Macaca fascicularis fascicularis) in the context of toxicological studies

BACKGROUND

The long-tailed macaque (Macaca fascicularis fascicularis) is an Old World species, which is one among the most commonly used monkeys for pharmaceutical research. However, most of the available background data are not suitable for good laboratory practice (GLP)-regulated drug safety tests because the current reverence value covers fewer indices than necessary. Therefore, in this study, historical data for preclinical safety test were collected and managed.

METHODS

Twenty-five hematology, 20 clinical chemistry, 19 urine analysis, and 16 organ weights were evaluated in a drug safety test of 228 male and 140 female 2- to 4-year-old long-tailed macaques at the Korea Institute of Toxicology under GLP regulations.

RESULTS

The absolute and relative count of lymphocyte, basophil, and large unstained cell were higher, whereas neutrophil was lower in male than in female monkeys. In serum biochemistry, IP, GGT, ALP, and TCHO of male were higher than female.

CONCLUSION

Historical data suitable for preclinical safety analysis were determined.

Brief Synopsis: "Instruction Manual for Juvenile Clinical Pathology"

This symposium synopsis summarizes key points discussed related to clinical pathology data interpretation for reproduction and juvenile toxicology studies. In pregnant and growing animals, several changes in clinical pathology parameters linked to growth/maturation of organ and physiological functions can occur, and understanding these changes is important to enable accurate interpretation of clinical pathology data. A brief overview of the general approach to clinical pathology data analysis according to contemporary practices is provided, followed by a discussion focused specifically on reproductive and juvenile clinical pathology. In this context, the approach to recognize and differentiate changes that may be related to pregnancy and growth as opposed to those that may be related to test article effects is highlighted.

Suggested guidelines for validation of real-time PCR assays in veterinary diagnostic laboratories

This consensus document presents the suggested guidelines developed by the Laboratory Technology Committee (LTC) of the American Association of Veterinary Laboratory Diagnosticians (AAVLD) for development, validation, and modification (methods comparability) of real-time PCR (rtPCR) assays. These suggested guidelines are presented with reference to the World Organisation for Animal Health (OIE) guidelines for validation of nucleic acid detection assays used in veterinary diagnostic laboratories. Additionally, our proposed practices are compared to the guidelines from the Foods Program Regulatory Subdivision of the U.S. Food and Drug Administration (FDA) and from the American Society for Veterinary Clinical Pathology (ASVCP). The LTC suggestions are closely aligned with those from the OIE and comply with version 2021-01 of the AAVLD Requirements for an Accredited Veterinary Medical Diagnostic Laboratory, although some LTC recommendations are more stringent and extend beyond the AAVLD requirements. LTC suggested guidelines are substantially different than the guidelines recently published by the U.S. FDA for validation and modification of regulated tests used for detection of pathogens in pet food and animal-derived products, such as dairy. Veterinary diagnostic laboratories that perform assays from the FDA Bacteriological Analytical Method (BAM) manual must be aware of the different standard.

Aspiration and Inspiration: Using Bronchoalveolar Lavage for Toxicity Assessment

Bronchoalveolar lavage (BAL) is a simple procedure that is used to investigate drug efficacy or lung toxicity. It is sensitive to lung changes and less invasive than histological evaluation. It can be performed repeatedly at interim time points or as a terminal procedure. Airborne contaminants and purposely inhaled compounds, resident and inflammatory cells, as well as different cellular soluble products can be harvested in bronchoalveolar fluid (BALF) and measured. Bronchoalveolar lavage can also be an important tool to understand drug exposure and its metabolism in the lung, although it should be rigorously performed and interpreted with caution, especially in the context of regulated toxicology studies. This review focuses on the methods and uses of BAL in animal research, primarily in the pharmaceutical industry, as well as for the assessment of drugs, pollutants, and chemical lung toxicity. Methods of collecting and analyzing BALF and parameters affecting variability are discussed in detail. Improved automated methods for cell counting and analysis of the inflammatory cellular differential using hematology analyzers, common markers of lung injury, and new methodologies are described. Correlation between BALF and histological evaluation should not be considered as repetitive but as complementary assessments in the context of efficacy and toxicity studies.

Scientific and Regulatory Policy Committee Points to Consider*: Approaches to the Conduct and Interpretation of Vaccine Safety Studies for Clinical and Anatomic Pathologists

The design and execution of toxicology studies supporting vaccine development have some unique considerations relative to those supporting traditional small molecules and biologics. A working group of the Society of Toxicologic Pathology Scientific and Regulatory Policy Committee conducted a review of the scientific, technical, and regulatory considerations for veterinary pathologists and toxicologists related to the design and evaluation of regulatory toxicology studies supporting vaccine clinical trials. Much of the information in this document focuses on the development of prophylactic vaccines for infectious agents. Many of these considerations also apply to therapeutic vaccine development (such as vaccines directed against cancer epitopes); important differences will be identified in various sections as appropriate. The topics addressed in this Points to Consider article include regulatory guidelines for nonclinical vaccine studies, study design (including species selection), technical considerations in dosing and injection site collection, study end point evaluation, and data interpretation. The intent of this publication is to share learnings related to nonclinical studies to support vaccine development to help others as they move into this therapeutic area. [Box: see text].

Interpretative considerations for clinical pathology findings in nonclinical toxicology studies

The interpretation of clinical pathology results from nonclinical safety studies is a fundamental component in hazard identification of new drug candidates. The ever-increasing complexity of nonclinical safety studies and sophistication of modern analytical methods have made the interpretation of clinical pathology information by a highly trained subject matter expert imperative. Certain interpretive techniques are particularly effective in the identification and characterization of clinical pathology effects. The purpose of this manuscript is to provide an overview of contemporary interpretive practices for clinical pathology results and to provide nonbinding recommendations aimed at improving consistency, quality, and overall value of clinical pathology interpretations generated in support of nonclinical toxicology studies.

Evolving the Role of Discovery-focused Pathologists and Comparative Scientists in the Pharmaceutical Industry

GlaxoSmithKline has recently made significant organizational changes to its nonclinical safety, drug metabolism and pharmacokinetic, and laboratory animal science/veterinary functions, with the goal to increase our focus on scientific partnership with the discovery part of the organization. One specific change was bringing together pathologists and comparative medicine veterinarians and scientists into a single functional unit. We describe our early activities (assessing our capabilities and gaps, external benchmarking, listening to our discovery partners, redesigning some of our working practices) aimed at implementing these changes. In addition, early on we held a Discovery Engagement Workshop attended by all pathologists and comparative medicine veterinarians and scientists, as well as selected discovery scientists. The purpose of this workshop was to share learnings from the above activities and devise plans aimed at achieving our overall goal of functional integration: driving pathobiology expertise into drug discovery and increasing the human (translational) relevance of experimental data. This review describes the new organizational structure, the workshop activities, and implementation plans; updates our progress; and considers the opportunity for a pan-industry network of discovery-focused pathologists and comparative medicine veterinarians and scientists.

Bias due to Preanalytical Dilution of Rodent Serum for Biochemical Analysis on the Siemens Dimension Xpand Plus

Clinical pathology testing of rodents is often challenging due to insufficient sample volume. One solution in clinical veterinary and exploratory research environments is dilution of samples prior to analysis. However, published information on the impact of preanalytical sample dilution on rodent biochemical data is incomplete. The objective of this study was to evaluate the effects of preanalytical sample dilution on biochemical analysis of mouse and rat serum samples utilizing the Siemens Dimension Xpand Plus. Rats were obtained from end of study research projects. Mice were obtained from sentinel testing programs. For both, whole blood was collected via terminal cardiocentesis into empty tubes and serum was harvested. Biochemical parameters were measured on fresh and thawed frozen samples run straight and at dilution factors 2-10. Dilutions were performed manually, utilizing either ultrapure water or enzyme diluent per manufacturer recommendations. All diluted samples were generated directly from the undiluted sample. Preanalytical dilution caused clinically unacceptable bias in most analytes at dilution factors four and above. Dilution-induced bias in total calcium, creatinine, total bilirubin, and uric acid was considered unacceptable with any degree of dilution, based on the more conservative of two definitions of acceptability. Dilution often caused electrolyte values to fall below assay range precluding evaluation of bias. Dilution-induced bias occurred in most biochemical parameters to varying degrees and may render dilution unacceptable in the exploratory research and clinical veterinary environments. Additionally, differences between results obtained at different dilution factors may confound statistical comparisons in research settings. Comparison of data obtained at a single dilution factor is highly recommended.

Recommendations for Clinical Pathology Data Generation, Interpretation, and Reporting in Target Animal Safety Studies for Veterinary Drug Development

Clinical pathology testing is routinely performed in target animal safety studies in order to identify potential toxicity associated with administration of an investigational veterinary pharmaceutical product. Regulatory and other testing guidelines that address such studies provide recommendations for clinical pathology testing but occasionally contain outdated analytes and do not take into account interspecies physiologic differences that affect the practical selection of appropriate clinical pathology tests. Additionally, strong emphasis is often placed on statistical analysis and use of reference intervals for interpretation of test article–related clinical pathology changes, with limited attention given to the critical scientific review of clinically, toxicologically, or biologically relevant changes. The purpose of this communication from the Regulatory Affairs Committee of the American Society for Veterinary Clinical Pathology is to provide current recommendations for clinical pathology testing and data interpretation in target animal safety studies and thereby enhance the value of clinical pathology testing in these studies.

Effect of time and temperature on anticoagulant-dependent pseudothrombocytopenia in Göttingen minipigs

BACKGROUND

A marked decrease in thrombocyte count was observed between subsequent measurements of the same EDTA blood sample in several minipigs, but little information was available explaining this finding.

OBJECTIVES

The objective was to evaluate the impact of several preanalytic variables on thrombocyte counts in minipigs, in order to improve understanding of the in vitro thrombocyte decrease observed.

MATERIALS AND METHODS

Hematology blood samples from male and female Göttingen minipigs were collected using EDTA or citrate as an anticoagulant. Samples were stored under different conditions (room temperature, 4°C, or 37-38°C) and were analyzed approximately 0.5 to one h, 3.5-4 h, 7-7.5 h, and 28-29 h after collection.

RESULTS

In EDTA blood samples from male minipigs stored at room temperature, there was a progressive thrombocyte decrease over time up to -71% after 29 h, caused by in vitro aggregation. In females, no consistent change was seen up to 7.5 h, but there was a decrease up to -47% after 29 h. Thrombocyte count was most stable during storage at 4°C. No consistent marked decrease in thrombocyte counts was seen for citrated blood at room temperature, although such a decrease was present in a few individual animals.

CONCLUSIONS

Study results provide evidence for an anticoagulant-dependent pseudothrombocytopenia in minipigs progressing over time and depending on the storage temperature of the blood sample. It is therefore recommended to perform thrombocyte counts as soon as possible after blood collection, and in case of low counts, investigate for the presence of artifactual platelet clumping.

Interpreting and Integrating Clinical and Anatomic Pathology Results

The continuing education course on integrating clinical and anatomical pathology data was designed to communicate the importance of using a weight of evidence approach to interpret safety findings in toxicology studies. This approach is necessary, as neither clinical nor anatomic pathology data can be relied upon in isolation to fully understand the relationship between study findings and the test article. Basic principles for correlating anatomic pathology and clinical pathology findings and for integrating these with other study end points were reviewed. To highlight these relationships, a series of case examples, presented jointly by a clinical pathologist and an anatomic pathologist, were used to illustrate the collaborative effort required between clinical and anatomical pathologists. In addition, the diagnostic utility of traditional liver biomarkers was discussed using results from a meta-analysis of rat hepatobiliary marker and histopathology data. This discussion also included examples of traditional and novel liver and renal biomarker data implementation in nonclinical toxicology studies to illustrate the relationship between discrete changes in biochemistry and tissue morphology.

Preanalytical Considerations for Joint Fluid Evaluation

Synovial fluid analysis is a key component of the minimum database needed to diagnose and manage primary and secondary articular joint disorders. Unfortunately, preanalytical variables can drastically alter samples submitted for evaluation to veterinary laboratories and it is considered the stage at which most laboratory error occurs. This article addresses common sources of preanalytical variability and error that are seen in veterinary medicine. With consistent quality control and reporting of specimens, downstream clinical decision making and management of patients can be accelerated and improved.

STP Best Practices for Evaluating Clinical Pathology in Pharmaceutical Recovery Studies

The Society of Toxicologic Pathology formed a working group in collaboration with the American Society for Veterinary Clinical Pathology to provide recommendations for the appropriate inclusion of clinical pathology evaluation in recovery arms of nonclinical toxicity studies but not on when to perform recovery studies. Evaluation of the recovery of clinical pathology findings is not required routinely but provides useful information on risk assessment in nonclinical toxicity studies and is recommended when the ability of the organ to recover is uncertain. The study design generally requires inclusion of concurrent controls to separate procedure-related changes from test article–related changes, but return of clinical pathology values toward baseline may be sufficient in some cases. Evaluation of either a select or full panel of standard hematology, coagulation, and serum and urine chemistry biomarkers can be scientifically justified. It is also acceptable to redesignate dosing phase animals to the recovery phase or vice versa to optimize data interpretation. Assessment of delayed toxicity during the recovery phase is not required but may be appropriate in development programs with unique concerns. Evaluation of the recovery of clinical pathology data for vaccine development is required and, for efficacy markers, is recommended if it furthers pharmacologic understanding.

Determining the effect of storage conditions on prothrombin time, activated partial thromboplastin time and fibrinogen concentration in rat plasma samples

Coagulation parameters are usually included in clinical and preclinical safety studies to evaluate the effect of xenobiotics on the extrinsic or intrinsic pathways of coagulation. The analysis is generally performed at the time of terminal sacrifice where many activities are scheduled. Chances of delay in analysis are likely particularly when blood is collected for coagulation via the abdominal vena cava. This experiment was planned to assess the variations in coagulation parameters caused by delay in analysis as well as by storage conditions. Blood was collected from the posterior vena cava under isoflurane anesthesia, and the plasma was separated immediately. Coagulation parameters were evaluated at 0, 6, 24 and 48 h from the plasma stored at room temperature, as well as plasma stored under refrigerated and freezing conditions. Stability of the analytes in blood was also evaluated under refrigerated conditions for 6 h. All parameters were analyzed using a semi-automated coagulometer. Prothrombin time (PT) was stable under all three storage conditions for up to 6 h. Although statistically significant differences were observed for activated partial thromboplastin time (APTT) at room and refrigeration temperatures for up to 6 h, the difference was clinically non-relevant. Fibrinogen was found to be the most stable parameter that showed consistency in results even up to 48 h under all three storage conditions. Plasma for PT can be stored and analyzed without any significant changes for up to 6 h from the actual blood collection, while fibrinogen level testing can be extended for up to 48 h after collection under any storage condition. For reliable APTT results, plasma samples should be run immediately after collection.

Factors affecting urine reagent strip blood results in dogs and nonhuman primates and interpretation of urinalysis in preclinical toxicology studies: a Multi-Institution Contract Research Organization and BioPharmaceutical Company Perspective

BACKGROUND

Urinalysis data in preclinical toxicology studies can be influenced by preanalytic and analytic factors which have the potential to confound interpretation. There is a paucity of information regarding positive reagent strip urinary blood reactions in healthy nonhuman primates (NHP) and Beagle dogs used in preclinical toxicology studies.

OBJECTIVES

The objectives were (1) to establish historical control data for reagent strip urinary blood reactions in healthy NHP and Beagle dogs, (2) to determine the incidence of positive urinary blood reactions during predose and dosing phases, and (3) to determine if collection practice was a relevant parameter.

METHODS

Historical control data from 2 institutions in the biopharmaceutical industry were retrospectively analyzed for reagent strip urinary blood reactions in healthy NHP and Beagles. The incidence of positive results between the 2 institutions with different urine collection practices and between males and females was compared.

RESULTS

The incidence of positive urinary blood reactions in NHP was comparable between institutions (≤ 14% in males; ≤ 33% in females), while the incidence of positive urinary blood reactions in Beagles was more variable (≤ 77% in males; ≤ 69% in females), and higher in females during the dosing phase.

CONCLUSIONS

Positive urinary blood results that could potentially be misinterpreted as toxicologically relevant were identified in healthy NHP and Beagles during predose and dosing phases. Different incidences of positive results between the 2 institutions were likely related to collection practices. Strategies to reduce feces and food contamination of collected urine samples should help minimize false-positive urinary blood reactions.

Polyclonal Peptide Antisera

Polyclonal antibodies are relatively easy to produce and may supplement monoclonal antibodies for some applications or even have some advantages. The choice of species for production of (peptide) antisera is based on practical considerations, including availability of immunogen (vaccine) and animals. Two major factors govern the production of antisera: the nature of adaptive immune responses, which take place over days/weeks and ethical guidelines for animal welfare. Here, simple procedures for immunization of mice, rabbits, sheep, goats, pigs, horses, and chickens are presented.