The evaluation of changes in the immune system serves to determine the efficacy and potential immunotoxicologic effects of new products under development. Toxicologic pathologists play critical roles in identifying immune system changes that drive the immunosafety determination. Standard pathology evaluations of therapies and chemicals remain similar; however, biopharmaceutical therapies have moved from simply affecting the immune system to being specifically developed to modify the immune system, which can impact interpretation. Recent explosive growth in immunomodulatory therapies presents a challenge to the toxicologic pathologist, toxicologist, and regulatory reviewer in terms of evaluating the clinical relevance and potential adversity of immune system changes. Beyond the recognition of such changes, there is an increasing expectation to evaluate, describe, and interpret how therapies affect complex immune system pathways for both immunomodulatory therapies and non-immunomodulatory drugs with off-target immunotoxic effects. In this opinion piece, considerations regarding immune system evaluation, the current landscape of immunomodulatory therapies, a brief description of immunotoxicologic (and immunopathologic) endpoints, the importance of integrating such immunosafety data, and relevance to adversity determination are discussed. Importantly, we describe how the current paradigm of determining adversity for immune system changes may be challenging or insufficient and propose a harmonized and flexible approach for assessing adversity.

The European Society of Toxicologic Pathology organized an expert workshop in May 2018 to address adversity considerations related to thyroid follicular cell hypertrophy and/or hyperplasia (FCHH), which is a common finding in nonclinical toxicity studies that can have important implications for risk assessment of pharmaceuticals, food additives, and environmental chemicals. The broad goal of the workshop was to facilitate better alignment in toxicologic pathology and regulatory sciences on how to determine adversity of FCHH. Key objectives were to describe common mechanisms leading to thyroid FCHH and potential functional consequences; provide working criteria to assess adversity of FCHH in context of associated findings; and describe additional methods and experimental data that may influence adversity determinations. The workshop panel was comprised of representatives from the European Union, Japan, and the United States. Participants shared case examples illustrating issues related to adversity assessments of thyroid changes. Provided here are summary discussions, key case presentations, and panel recommendations. This information should increase consistency in the interpretation of adverse changes in the thyroid based on pathology findings in nonclinical toxicity studies, help integrate new types of biomarker data into the review process, and facilitate a more systematic approach to communicating adversity determinations in toxicology reports.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative changes in rats and mice. The purpose of this publication is to provide a standardized nomenclature for classifying changes observed in the hematolymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissues, and other lymphoid tissues (serosa-associated lymphoid clusters and tertiary lymphoid structures) with color photomicrographs illustrating examples of the lesions. Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. The nomenclature for these organs is divided into 3 terminologies: descriptive, conventional, and enhanced. Three terms are listed for each diagnosis. The rationale for this approach and guidance for its application to toxicologic pathology are described in detail below.

Summary: Background & aims: Administration of glutamine in patients with renal dysfunction is considered to be potentially adverse. In a rat model of moderate kidney dysfunction dose-dependent effects of intravenous alanyl-glutamine infusion on possible biochemical and histological signs of toxicity were investigated. Methods: Rats with renal dysfunction resulting from 5/6 nephrectomy received a 9 days continuous intravenous infusion of either saline or 0.5 g/kg/day or 3.0 g/kg/day alanyl-glutamine (Dipeptiven®) or 3.0 g/kg/day alanine. Dose-dependent effects on kidney and other organs were assessed by analyzing blood levels of creatinine, ammonia, urea, ALT, AST, ALP, pH, pO2, pCO2, glutamine, and histopathology. Results: Continuous intravenous infusion of 3.0 g/kg/day alanyl-glutamine increased plasma glutamine concentrations up to 60% without aggravating the underlying kidney injury. In contrast, the morphology of the kidneys was improved due to reduced glomerulosclerosis and tubular proteinaceous casts. An increase in plasma urea concentrations observed in the 3.0 g/kg/day alanyl-glutamine group only was not associated with worsening of the phenotype. Conclusions: Continuous intravenous infusion of alanyl-glutamine at 0.5 and 3.0 g/kg/day up to 9 consecutive days is safe in a rat model of chronic moderate kidney dysfunction and improved the renal morphology by reducing glomerulosclerosis and tubular proteinaceous casts. In these animals a decreased incidence and severity of chronic progressive nephropathy was observed compared to the saline and alanine treated animals. Keywords: Renal dysfunction, Glomerulosclerosis, Proteinaceous casts, Glutamine, Urea

Summary: Background & aims: Administration of glutamine in patients with liver failure is thought to possibly increase blood ammonia levels, thereby contributing to hepatic encephalopathy. In a rat model of moderate liver dysfunction with elevated plasma glutamine concentrations dose-dependent effects of intravenous alanyl-glutamine infusion on possible biochemical and histological signs of toxicity were investigated. Methods: Rats with moderate liver dysfunction resulting from alpha-naphthylisothiocyanate (ANIT) induced cholestasis received a 9 days continuous intravenous infusion of 0.5 g/kg/day or 3.0 g/kg/day alanyl-glutamine (Dipeptiven®). Dose-dependent effects on liver injury were assessed by analyzing blood levels of ammonia, urea, ALT, AST, and ALP, glutamine, and histopathology. Results: Continuous intravenous infusion of 3.0 g/kg/day alanyl-glutamine increased plasma glutamine concentrations up to 30% without increasing blood ammonia levels or inducing astrocyte swelling. Alanyl-glutamine did not aggravate underlying liver injury shown by absent increase in plasma levels of ALT, AST, ALP and no signs of histopathologic alterations. Conclusions: Continuous intravenous infusion of alanyl-glutamine at 0.5 and 3.0 g/kg/day up to 9 consecutive days is safe in a rat model of moderate liver dysfunction based on ANIT-induced cholestasis. Keywords: Ammonia, Astrocyte swelling, Brain edema, Cholestasis, Glutamine, Liver injury

Plasma amino acid level changes occur in mild, moderate and severe stages of liver injury in human patients. In animal models, however, data are mainly restricted to severe liver injury models in rats. Here we present the characterization of a rat model of moderate liver dysfunction secondary to alpha-napthylisothiocyanate (ANIT)-induced cholestasis. Rats treated with 30 mg/kg/day ANIT for 3 weeks exhibited a time-dependent increase in plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST) and bilirubin levels and a decrease in albumin concentration. According to a liver dysfunction evaluation based on the human Child-Pugh-Score, animals developed a moderate liver dysfunction in the first two weeks of ANIT treatment, while only a mild dysfunction was observed at the end of week 3 despite ongoing ANIT administration. Univariate analysis of branched-chain amino acid plasma levels indicated that reduced levels of branched chain amino acids were associated with the ANIT treatment. These data may set the stage for further research of amino acid disturbances and requirements in non-severe cholestasis.

The identification of adverse health effects has a central role in the development and risk/safety assessment of chemical entities and pharmaceuticals. There is currently a need for better alignment regarding how nonclinical adversity is determined and characterized. The European Society of Toxicologic Pathology (ESTP) therefore coordinated a workshop to review available definitions of adversity, weigh determining and qualifying factors of adversity based on case examples, and recommend a practical approach to define and characterize adversity in toxicology reports, to serve as a valuable prerequisite for future organ- or lesion-specific workshops planned by the ESTP.

Background: The compliance of lipid admixtures to physical emulsion stability parameters is extremely important to ensure the safety of patients. For example, admixtures containing a percentage of fat globules larger than 5 μm in diameter (concept known as PFAT5) of more than 0.05% might produce toxic effects in lung and liver. This concern is mainly based on a limited number of animal studies investigating admixtures with high PFAT5 levels resulting from 48 h of admixture storage. However, all effects observed in these studies might as well be attributed to chemical instability like lipid oxidation, which was not analysed and therefore could not be excluded. Aims: This study aims at investigating the correlation of high levels of PFAT5 in lipid emulsion admixtures with lipid oxidation parameters under different storage conditions. Methods: We studied the physical (PFAT5 value) as well as the chemical (pH, primary and secondary oxidation parameters) stability of an admixture of a lipid emulsion and an amino acid solution after up to 48 h following different storage conditions (exposure to oxygen, exposure to artificial light). Results: High levels of PFAT5 were only observed after exposure of the admixture to oxygen. Additional exposure to artificial light led to a parallel increase in the primary and secondary oxidation parameters, while the pH was unchanged. Conclusions: The admixtures investigated in the former animal studies were obviously both physically and chemically unstable and all effects observed in the studies could just as well be caused by chemical instability, namely the administration of lipid peroxides with the admixture.

The identification of adverse health effects has a central role in the development and risk/safety assessment of chemical entities and pharmaceuticals. There is currently a need for better alignment regarding how nonclinical adversity is determined and characterized. The European Society of Toxicologic Pathology (ESTP) therefore coordinated a workshop to review available definitions of adversity, weigh determining and qualifying factors of adversity based on case examples, and recommend a practical approach to define and characterize adversity in toxicology reports, to serve as a valuable prerequisite for future organ- or lesion-specific workshops planned by the ESTP.

Background: Ticagrelor is an orally available, direct acting and reversible P2Y(12) receptor antagonist approved for treatment of acute coronary syndrome. The objectives of these studies were to (1) evaluate the Ticagrelor 2-year rat carcinogenicity bioassay data; (2) investigate potential mode of action (MOA) and (3) interpret human relevance.Methods: The following studies were done (1) rat two-year carcinogenicity study in male and female rats, (2) in vitro and in vivo genotoxicity assays, (3) quantitative whole body autoradiography (QWBA; male and female rats), (4) in vitro pharmacological profiling for more than 300 assays, and (5) in vivo ovariectomized rat assay.Results: The carcinogenicity study indicated Ticagrelor increased uterine tumor incidence while decreasing mammary and pituitary tumors/hyperplasia incidences in only high dose female rats. However, this altered tumor incidences were not P2Y(12) target related since marketed non-reversible P2Y(12) receptor antagonists were not associated with alter tumor incidences. MOA studies determined Ticagrelor exposure in the anterior pituitary and Ticagrelor was (1) non-genotoxic, (2) peripherally-restricted, (3) a dopamine transport (DAT) inhibitor with an IC(50)lower than systemic free exposure in the rat carcinogenic study and more than a log higher than the free systemic exposure seen in clinical trials and (4) an inhibitor of estradiol-induced prolactin secretion.

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicological Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in the female reproductive tract of laboratory rats and mice, with color photomicrographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. There is also a section on normal cyclical changes observed in the ovary, uterus, cervix and vagina to compare normal physiological changes with pathological lesions. A widely accepted and utilized international harmonization of nomenclature for female reproductive tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Wistar rats are frequently selected for use in carcinogenicity studies because of their advantageous survival rate, which is more favorable than other strains such as the Sprague-Dawley (SD) strain. Uterine and mammary tumors are relatively common spontaneous neoplasms of both strains. We examined the incidence and coincidence of uterine tumors and mammary tumors in control animals of both strains within the RITA database. There was a strong inverse relationship between these tumor types in Wistar rats ( p < .001). A less strong relationship was present in SD rats ( p = .057). This association is likely to be related to prolactin. A short review of the role of prolactin in rats is given. These results are also discussed in the background of nonspecific toxicity at high dose levels in carcinogenicity studies above MTD levels resulting in reduction in body weights of >10%.

ABSTRACT Drug‐induced changes in prolactin signaling may obscure interpretation of preclinical toxicological endpoints. However, with informed consideration, classic hallmarks of hypo‐/hyperprolactinemia can be recognized in short‐ and long‐term rodent bioassays. Findings can be supported and expanded with additional in vivo and in vitro datasets. When taken together with human epidemiological evidence pertaining to the consequences of drug‐induced hypo‐/hyperprolactinemia, such findings permit both an analysis of human relevance and an assessment of human risk. Copyright © 2011 John Wiley & Sons, Ltd.

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicological Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in the female reproductive tract of laboratory rats and mice, with color photomicrographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. There is also a section on normal cyclical changes observed in the ovary, uterus, cervix and vagina to compare normal physiological changes with pathological lesions. A widely accepted and utilized international harmonization of nomenclature for female reproductive tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.