Lab Animal

Have you ever reflected on your career or other experiences and thought, if I knew 10 or 20 years ago, what I know now, it would have enabled me to do this or that better—or I would have had a different attitude or perhaps even taken a different path? This article presents the proceedings from the symposium entitled “I Wish I Had Known That! Impactful Guidance and Perspectives for a Fulfilling Career in Toxicology” held at the 2023 annual meeting of the American College of Toxicology. In this session, toxicology professionals reflected on the highlights of their careers, the most impactful advice/mentoring they received or wish they had received, and the characteristics that have been key components of their success. This session consisted of didactic talks from a diverse panel representing various career stages and backgrounds, followed by a panel discussion and the opportunity for the audience to ask questions. Using a structured approach, speakers actively engaged the audience, providing insights gained through their professional journeys. This article offers experiential-based insights to help guide individuals in achieving successful and fulfilling careers in toxicology, considering both professional aspirations and the integration of personal values with life goals.

Fueled by the identification and invention of novel gene delivery vectors, gene therapy efforts now hold promise for treating a wide range of diseases and are seen as a crucial part of growth for the biopharmaceutical industry. Currently, recombinant adeno-associated virus vectors (rAAVs) and lentiviral vectors (LVs) are the main vectors used in gene therapies that are approved or tested in human clinical trials. Meanwhile, ongoing research continuously reveals unprecedented knowledge of viral vectors on the host genome, which may subsequently affect the mutagenic and carcinogenic potential of these therapies. This article summarizes the content and addresses the commentary from the scientific symposium entitled “Mutagenesis and Carcinogenesis Risk Evaluation for AAV and Lentiviral Gene Therapies,” conducted at the 43rd Annual Meeting of the American College of Toxicology, November 2022 in Denver, CO. The objective is to summarize the current understanding of rAAV and LV related mutagenicity/carcinogenicity risk, describe the methods and interpretation of results to guide risk assessments, as well as the current regulatory landscape on the carcinogenicity and mutagenicity assessment of rAAV and LV gene therapy products.

Sulfur mustard (SM) is a highly toxic bifunctional alkylating agent that inflicts severe damage on the respiratory tract. Although numerous studies have examined the mechanisms underlying SM-induced pulmonary injury, the exact pathways involved remain unclear. This study aims to investigate an acute pulmonary injury model, with SM administered as a single intraperitoneal injection (8 mg/kg) or single intratracheal instillation (2 mg/kg) at equal toxicity doses (1LD50). The results revealed that epithelial cells in the alveolar septa of the intraperitoneal SM group exhibited a significantly higher expression of apoptotic markers, including pro-apoptotic protein Bax, caspase-3, and caspase-9 proteins, than those in the tracheal SM group. Conversely, the expression of the anti-apoptotic protein Bcl-2 was significantly lower in the intraperitoneal SM group than in the tracheal SM group, as confirmed by TUNEL staining and immunohistochemical staining. The intraperitoneal SM group exhibited markedly higher expression of fibrosis-related proteins, including MMP-2, MMP-9, TIMP-1, TIMP-2, collagen type I, collagen type III, TGF-β1, and Smad7, than the tracheal SM group. These markers, detected through immunohistochemical immunolabeling, indicate a more significant fibrotic response in the intraperitoneal group. In summary, this study demonstrates that intraperitoneal exposure to SM results in increased apoptosis, elevated expression of pro-apoptotic proteins, and fibrosis-related proteins in the alveolar epithelial cells compared with intratracheal exposure, even at equivalent toxicity levels. Our findings highlight the suitability of the intraperitoneal route for further investigation and identify apoptotic and fibrosis-related proteins as potential targets for intervention in SM-induced pulmonary injury.

Seizures are complex electrophysiological disturbances affecting one or more populations of brain neurons. Seizures following test article (TA) exposure pose significant challenges in drug development. This paper considers the diverse neurological manifestations, mechanisms, and functional and structural assessments needed to investigate TA-related seizure liabilities, with a particular focus on nonclinical species. Accurate discrimination of seizures from convulsions (irregular involuntary body and/or limb movements) and the nuanced presentation of different seizure types (partial vs. general) and phases (prodromal, ictal, and postictal) are essential for discerning their clinical implications. In nonclinical safety testing, the most direct evaluation method to confirm existence of seizures is electroencephalography (EEG) while clinical endpoints (e.g., functional observational batteries [FOB], comprehensive neurological examinations) and neuropathological findings (e.g., neuronal necrosis in tissue sections, raised biomarker levels in cerebrospinal fluid or serum) can indicate a seizure liability and provide additional guidance to identify the origin, frequency, and severity of seizures needed to align nonclinical effects with clinical relevance. In general, the regulatory perspective is that seizures identified in nonclinical species as well as potential risk management strategies (e.g., safety margin considerations, dosing paradigms, and clinical monitoring) translate effectively for purposes of clinical risk assessment.

The therapeutic window of antibody drug-conjugates (ADC) remains challenging due to safety issues such as interstitial lung disease (ILD) observed with specific deruxtecan-based ADCs. To avoid ILD, we designed M9140 by conjugating the maleimide-containing hydrophilic β-glucuronide linker to exatecan and our anti-CEACAM5 (CarcinoEmbryonic Antigen-related Cell Adhesion Molecule 5) specific antibody. Following repeated iv-infusion at 3 to 30 mg/kg of M9140 every 3 weeks, the pathological findings obtained in cynomolgus monkeys were confined to gastrointestinal and hematolymphoid tissues and resembled the toxicity of exatecan. At 24 mg/kg or higher, transient reductions in neutrophil and reticulocyte counts were observed with each dosing event along with reversible anemia throughout the study. The no observed adverse effect level was 24 mg/kg and the maximum tolerated dose was 30 mg/kg. The difference in toxicity by this small dose increment was correlated with a 2.5-fold difference in plasma exatecan exposure indicating antigen-independent toxicity. As anticipated, no lung toxicity was found with M9140 in these studies that were similar in study design to those used to confirm ILD with trastuzumab-deruxtecan in monkeys. Since the non-human primate model is regarded as predictive for the ILD risk in humans, this result indicates a low risk for ILD when applying M9140 to patients. The current M9140 safety data are discussed with special focus on the absence or presence of ILD with other antibody camptothecin-conjugates, for which a hypothetical pathogenic mechanism is postulated here. The favorable nonclinical profile of M9140 warrants further investigation in patients with CEACAM5-overexpressing tumors.

Endocrine-disrupting chemicals (EDCs) play an important role in the incidence of type-2 diabetes. Di-2-ethyl hexyl Phthalate (DEHP) is one of the endocrine-disrupting chemicals used as a plasticizer to impart flexibility and softness to plastic-containing materials. Mono-2-ethylhexyl Phthalate (MEHP), a DEHP’s primary metabolite, is preferentially absorbed once metabolized. A previous study from our laboratory showed that DEHP and MEHP altered the key proteins such as insulin receptor (INSR) and glucose transporter-4 (GLUT4) in L6 myotubes. In a sequel to the previous study, the present study hypothesized that DEHP and its metabolite MEHP may alter the Insr and Glut4 gene expression in L6 myotubes. Therefore, to find out the molecular mechanism behind the decreased INSR and GLUT4 protein levels in the previous study, the direct effect of DEHP and its metabolite MEHP in regulating Insr and Glut4 gene transcription in L6 myotubes was studied. The L6 myotubes were exposed to 50 and 100 μM DEHP and MEHP for 24 h, followed by insulin stimulation for 20 min. We observed decreased Insr and Glut4 mRNA levels in DEHP and MEHP-treated groups. Western blot data showed decreased protein levels of MEF2A and MyoD in treated groups. ChIP assay detected a decreased association of MEF2A and MyoD to the Glut4 gene promoter and HMGA1 to the Insr gene promoter. The study revealed that DEHP and MEHP diminished the Insr and Glut4 gene expression through weakened interaction of their transcription factors on the respective promoter.

The presence of polystyrene plastics in the human testis has raised concerns, yet their biological activity remains poorly characterized. This study aimed to investigate the biological effects and potential regulatory genes of polystyrene nanoplastics on spermatocyte line, GC-2spd(ts). After a 24-h exposure to polystyrene nanoplastics, the results indicated cell membrane disruption, impairment of mitochondrial membrane potential, increased levels of reactive oxygen species (ROS), and induced DNA damage. Furthermore, a comprehensive transcriptomic analysis was conducted, revealing differential gene expression patterns in GC-2spd(ts) cells in response to polystyrene nanoplastics. A total of 134 differentially expressed genes (DEGs) were identified, with 48 genes upregulated and 86 genes downregulated. The Gene Ontology analysis highlighted the involvement of these genes in various spermatogenesis-related biological processes, including acrosome reaction, sperm mitochondrial organization, sperm annulus, and outer acrosomal membrane. Subsequently, the quantification of gene expression through qRT-PCR identified five key genes (NSUN7, SEPTIN4, TRIM36, EQTN, and SYT8) screened from the DEGs. In conclusion, this study provides valuable insights into the biological effects of polystyrene nanoplastics on mouse spermatocytes using comprehensive transcriptomic analysis, contributing to the establishment of a foundation for future investigations into these relevant pathways.

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of Mannitol, Sorbitol, and Xylitol as used in cosmetics. These ingredients are reported to function as humectants, skin-conditioning agents, or flavoring agents. The Panel considered the available data and concluded that these sugar alcohol ingredients are safe in cosmetics in the present practices of use and concentration described in the safety assessment.

Oral toxicity and toxicokinetic properties of human lactoferrin (LF) alpha produced in Komagataella phaffii (effera™) were investigated in adult Sprague-Dawley rats over a 28-day period under good laboratory practice conditions. Main study dosing used groups of 10 rats/sex/dose, and a secondary study evaluating toxicokinetic parameters used 6 rats/sex/dose. The vehicle control group received sodium citrate buffer, test groups received daily doses of 200, 600, and 2000 mg of effera™ per kg body weight, and the comparative control group received 2000 mg bovine LF (bLF)/kg body weight per day. T-cell-dependent antibody response against keyhole limpet hemocyanin and immunophenotyping of the spleen were performed as measures of immunotoxicity. Clinical observations, body weight, hematology, coagulation, clinical chemistry, urinalysis, immunotoxicity, gross necropsy, and histopathology were assessed. Toxicokinetic parameters were analyzed as an indication of LF bioavailability, and anti-LF antibody assays were conducted to detect antibodies produced against LF to measure immunogenicity. No treatment related toxicologically significant changes were observed. Based on the absence of toxicologically relevant changes, effera™ is well tolerated in rats at doses up to 2000 mg rhLF/kg/day, an amount ∼400 times that of the estimated daily intake at the 90th percentile proposed for human adult use.

Felzartamab is a recombinant fully human immunoglobulin G1 anti-CD38 monoclonal antibody under clinical investigation for immune-mediated diseases. In support of felzartamab clinical development, toxicology studies were conducted in marmoset monkeys, which was the most relevant species based on CD38 binding affinity, pharmacologic activity, and target expression. The felzartamab toxicology program included an enhanced prenatal and postnatal development (ePPND) study to identify potential reproductive and postnatal development risks. In this ePPND study, pregnant marmoset monkeys were randomized to receive vehicle (0 mg/kg) or felzartamab at two dose levels (15 mg/kg and 75 mg/kg) twice per week until parturition, and maternal animals and infants were evaluated for 6 months thereafter. Felzartamab exposure was confirmed in maternal animals and infants in both dosing groups. Overall, felzartamab was well tolerated by pregnant animals at the evaluated doses, with no effect on body weight or body weight gain during pregnancy. No felzartamab-related effects on pregnancy loss or stillbirth rate were observed, and litter counts and numbers of liveborn infants were similar between the vehicle and felzartamab groups. Among infants, there were no felzartamab-related malformations or variations in external anatomy or skeletal morphology and no felzartamab-related observations in histopathology, hematologic and immune cell development, or humoral immune response to vaccination. In conclusion, among pregnant marmoset monkeys dosed with felzartamab, the lack of reproductive toxicity and felzartamab-related effects on offspring supports the clinical evaluation of felzartamab in women of childbearing potential and further demonstrates the suitability of the marmoset monkey for ePPND studies.

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 27 wheat-derived ingredients. Most of these ingredients are reported to function as skin conditioning agents in cosmetic products. The Panel reviewed the available data to determine the safety of these ingredients. Industry should continue to use good manufacturing practices to limit impurities that could be present in botanical ingredients. The Panel concluded that 21 wheat-derived ingredients are safe in cosmetics in the practices of use and concentration described in this safety assessment. However, the Panel also concluded that the available data are insufficient to make a determination of safety that the remaining six wheat-derived ingredients are safe under the intended conditions of use in cosmetic formulations.

The Expert Panel for Cosmetic Ingredient Safety (Panel) reviewed the safety of Ascorbyl Glucoside and Sodium Ascorbyl Glucoside in cosmetic products. These ingredients are reported to have the following functions in cosmetics: antioxidant, and skin-conditioning agent—miscellaneous. The Panel reviewed data relevant to the safety of these ingredients in cosmetic formulations, and concluded that Ascorbyl Glucoside and Sodium Ascorbyl Glucoside are safe in cosmetics in the present practices of use and concentration described in this safety assessment.

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 14 alkyl amide MIPA ingredients as used in cosmetics. All of these ingredients are reported to function in cosmetics as a surfactant – foam booster and/or viscosity increasing agent. The Panel considered the available data, as well as data on read-across sources, and concluded these ingredients are safe in cosmetics in the present practices of use and concentration described in this safety assessment when formulated to be non-irritating.