Toxicologic Pathology

This brief communication describes a rare spontaneous background lesion in the lower urinary tract of two male laboratory beagles. Proliferative lesions comprising a constellation of histological features consistent with polypoid cystitis were observed in the bladder of two adolescent dogs from a routine preclinical toxicology study. Both animals were clinically asymptomatic and had only minor alterations in urinalysis parameters. While chronic polypoid cystitis is well-recognized in adult pet dogs, this is the first reported case in purpose-bred laboratory beagles...

Direct delivery of therapeutics to the central nervous system (CNS) greatly expands opportunities to treat neurological diseases but is technically challenging. This opinion outlines principal technical aspects of direct CNS delivery via intracerebroventricular (ICV) or intrathecal (IT) injection to common nonclinical test species (rodents, dogs, and nonhuman primates) and describes procedure-related clinical and histopathological effects that confound interpretation of test article-related effects. Direct dosing is by ICV injection in mice due to their small body size, while other species are dosed IT in the lumbar cistern...

Drug-induced liver injury (DILI) remains a major concern in drug development from a patient safety perspective because it is the leading cause of acute liver failure. One mechanism of DILI is altered bile acid homeostasis and involves several hepatic bile acid transporters. Functional impairment of some hepatic bile acid transporters by drugs, disease, or genetic mutations may lead to toxic accumulation of bile acids within hepatocytes and increase DILI susceptibility. This review focuses on the role of hepatic bile acid transporters in DILI...

Replication-incompetent adeno-associated virus (AAV)-based vectors are nonpathogenic viral particles used to deliver therapeutic genes to treat multiple monogenic disorders. AAVs can elicit immune responses; thus, one challenge in AAV-based gene therapy is the presence of neutralizing antibodies against vector capsids that may prevent transduction of target cells or elicit adverse findings. We present safety findings from two 12-week studies in nonhuman primates (NHPs) with pre-existing or treatment-emergent antibodies...

Toxicology studies in nonhuman primates were conducted to evaluate selective, brain penetrant inhibitors of LRRK2. GNE 7915 was limited to 7-day administration in cynomolgus monkeys at 65 mg/kg/day or limited to 14 days in rhesus at 22.5 mg/kg b.i.d. due to physical signs. Compound 25 demonstrated acceptable tolerability at 50 and 225 mg/kg b.i.d. for 7 days in rhesus monkeys. MK-1468 was tolerated during 7-day administration at 100, 200 or 800 mg/kg/day or for 30-day administration at 30, 100, or 500 mg/kg b...

The availability of large amounts of high-quality control data from tightly controlled regulated animal safety data has created the idea to re-use these data beyond its classical applications of quality control, identification of treatment-related effects and assessing effect-size relevance for building virtual control groups (VCGs). While the ethical and cost-saving aspects of such a concept are immediately evident, the potential challenges need to be carefully considered to avoid any effect which could lower the sensitivity of an animal study to detect adverse events, safety thresholds, target organs, or biomarkers...

The minipig has been used as a non-rodent species in nonclinical toxicology studies, but little is known about amyloid A (AA) amyloidosis in this species. Among domestic pigs, reports of AA amyloidosis have been limited to animals with mutations in the N-terminal residue of serum AA (SAA), which is thought to be a primary etiological factor. In this study, we histologically examined 26 microminipigs aged 0.6 to 10 years and observed amyloid deposition in one 0.6-year-old and six 5-year-old or older microminipigs...

This article reviews the presentation given at the 2023 annual meeting of the Society of Toxicologic Pathology (STP) on liver toxicity observed with adeno-associated viral vector (AAV) gene therapy. After decades as a therapeutic modality largely confined to the academic research environment, gene therapy has emerged in recent years as a rapidly expanding therapeutic approach in the biopharmaceutical industry with AAV as the most commonly used viral vector for gene delivery. This interest in the field of gene therapy by industry has been enhanced by the recent success of approved therapies for curing genetic diseases such as ZOLGENSMA for spinal muscular atrophy and LUXTURNA for Leber congenital amaurosis...

During toxicology studies, fasting animals prior to clinical pathology blood collection is believed to reduce variability in some clinical chemistry analytes. However, fasting adds stress to animals that are already stressed from the administration of potentially toxic doses of the test article. The purpose of this study was to assess the impacts of different fasting durations on cynomolgus monkeys' welfare during toxicology studies. To this end, we assessed the cynomolgus monkeys traditional and ancillary clinical pathology endpoints at different fasting times...

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats...

No abstract text is available yet for this article.

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...

Certain biopharmaceutical products consistently affect dorsal root ganglia, trigeminal ganglia, and/or autonomic ganglia. Product classes targeting ganglia include antineoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, and anti-nerve growth factor agents. This article outlines "points to consider" for sample collection, processing, evaluation, interpretation, and reporting of ganglion findings; these points are consistent with published best practices for peripheral nervous system evaluation in nonclinical toxicity studies...

In situ hybridization (ISH) is used for the localization of specific nucleic acid sequences in cells or tissues by complementary binding of a nucleotide probe to a specific target nucleic acid sequence. In the last years, the specificity and sensitivity of ISH assays were improved by innovative techniques like synthetic nucleic acids and tandem oligonucleotide probes combined with signal amplification methods like branched DNA, hybridization chain reaction and tyramide signal amplification. These improvements increased the application spectrum for ISH on formalin-fixed paraffin-embedded tissues...

Branaplam is a splicing modulator previously under development as a therapeutic agent for Spinal Muscular Atrophy Type 1 and Huntington's disease. Branaplam increased the levels of survival motor neuron protein in preclinical studies and was well tolerated in early clinical studies; however, peripheral neurotoxicity was observed in a preclinical safety study in juvenile dogs. The aim of this study was to determine whether serum neurofilament light chain (NfL) concentrations in dogs could serve as a monitoring biomarker for branaplam-induced peripheral neurotoxicity...

In this study, we assessed the toxicity and toxicokinetics of racemic vigabatrin and its S- and R-enantiomers (vigabatrin consists of 50:50% of the two enantiomers) by administering doses of the three test articles to male Long Evans rats via oral gavage. The animals were housed under high-intensity light conditions and the study consisted of an escalating dose phase and a 21-day fixed-dose phase. Systemic toxicity of vigabatrin appears to be due to the Vig-S-enantiomer only, as increasing doses of Vig-S or Vig-RS caused body weight loss, decreased food consumption, and affected activity...

Dorsal root ganglia (DRG), trigeminal ganglia (TG), other sensory ganglia, and autonomic ganglia may be injured by some test article classes, including anti-neoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, nerve growth factor inhibitors, and aminoglycoside antibiotics. This article reviews ganglion anatomy, cytology, and pathology (emphasizing sensory ganglia) among common nonclinical species used in assessing product safety for such test articles (TAs)...

The European Society of Toxicologic Pathology (ESTP) initiated a survey through its Pathology 2.0 workstream in partnership with sister professional societies in Europe and North America to generate a snapshot of artificial intelligence (AI) usage in the field of toxicologic pathology. In addition to demographic information, some general questions explored AI relative to (1) the current status of adoption across organizations; (2) technical and methodological aspects; (3) perceived business value and finally; and (4) roadblocks and perspectives...

No abstract text is available yet for this article.

Vadadustat is an investigational oral hypoxia-inducible factor (HIF) prolyl-4-hydroxylase inhibitor to treat anemia due to chronic kidney disease (CKD). Some studies suggest that HIF activation promotes tumorigenesis by activating angiogenesis downstream of vascular endothelial growth factor, while other studies suggest that elevated HIF activity may produce an antitumor phenotype. To evaluate the potential carcinogenicity of vadadustat in mice and rats, we dosed CByB6F1/Tg.rasH2 hemizygous (transgenic) mice orally by gavage with 5 to 50 mg/kg/d of vadadustat for 6 months and dosed Sprague-Dawley rats orally by gavage with 2 to 20 mg/kg/d for approximately 85 weeks...