Pegbelfermin, a PEGylated FGF21 analogue, has pharmacology without bone toxicity after 1-year dosing in skeletally-mature monkeys.

Pegbelfermin (PGBF) is a PEGylated fibroblast growth factor 21 (FGF21) analogue in development for treatment of nonalcoholic steatohepatitis (NASH). Mouse models highlight potential utility of FGF21 in NASH, but also suggest negative effects on bone, though these findings are confounded by profound FGF21-related decreases in body mass/growth. This study aimed to profile PGBF-related bone effects in adult nonhuman primates after long-term, clinically-relevant exposures. Adult male cynomolgus monkeys received weekly subcutaneous PGBF (0.3, 0.75 mg/kg) or control injections for 1 year (n = 5/group). Assessments included body weight, clinical chemistry, adiponectin levels, bone turnover biomarkers, skeletal radiography, pharmacokinetics, immunogenicity, and histopathology. Bone densitometry and body composition were evaluated in vivo and/or ex vivo with dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and biomechanical strength testing. After 1 year of PGBF administration, there was clear evidence of sustained PGBF pharmacology in monkeys (peak increase in serum adiponectin of 1.7× and 2.35× pretest at 0.3 and 0.75 mg/kg PGBF, respectively) and decreased body weight compared with control at exposures comparable to those tested in humans. At 0.75 mg/kg PGBF, pharmacologically-mediated reductions in lean mass, lean area, and fat area were observed relative to controls. There were no PGBF-related effects on bone biomarkers, radiography, densitometry, or strength. Together, these data demonstrate that PGBF did not adversely alter bone metabolism, density, or strength following 1 year of dosing at clinically relevant (0.7-2.2× human AUC[0-168 h] at 20 mg once weekly), pharmacologically-active exposures in adult monkeys, suggesting a low potential for negative effects on bone quality in adult humans.

Tg.rasH2 Mouse Model for Assessing Carcinogenic Potential of Pharmaceuticals: Industry Survey of Current Practices.

The Tg.rasH2 mouse was developed as an alternative model to the traditional 2-year mouse bioassay for pharmaceutical carcinogenicity testing. This model has found extensive use in support of pharmaceutical drug development over the last few decades. It has the potential to improve quality and timeliness, reduce animal usage, and in some instances allow expedient decision-making regarding the human carcinogenicity potential of a drug candidate. Despite the increased use of the Tg.rasH2 model, there has been no systematic survey of current practices in the design, interpretation of results from the bioassay, and global health authority perspectives. Therefore, the aim of this work was to poll the pharmaceutical industry on study design practices used in the dose range finding and definitive 6-month studies and on results relative to the ongoing negotiations to revise The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use S1 Guidance. Twenty-two member companies of International Consortium for Innovation and Quality in Pharmaceutical Development DruSafe Leadership Group participated in the survey, sharing experiences from studies conducted with 55 test compounds between 2010 and 2018. The survey results provide very useful insights into study design and interpretation. Importantly, the results identified several key opportunities for reducing animal use and increasing the value of testing for potential human carcinogenicity using this model. Recommended changes to study designs that would reduce animal usage include eliminating the requirement to include positive control groups in every study, use of nontransgenic wild-type littermates in the dose range finding study, and use of microsampling to reduce or eliminate satellite groups for toxicokinetics.

Investigation on the Effect of Capillary Microsampling on Hematologic and Toxicokinetic Evaluation in Regulatory Safety Studies in Mice.

Microsampling techniques enable the minimization of blood collection volume from animals and subsequent handling of the blood samples or their derived plasma or serum samples. This offers advantages over conventional large-volume sampling, such as eliminating the need for satellite animals and improving animal welfare aspects, and providing the opportunity for additional assessments in small animals where blood volume constraints limit endpoints. This study evaluated the feasibility of implementation of capillary microsampling (CMS) in a single-dose study in mice with the ultimate goal of enabling its use in toxicology studies. The focus was on the impact of microsampling on toxicokinetic assessment and on the subsequent hematology assessment in the same animal. A seventy (70)-µL blood collection via CMS from the tail vein had a minimal effect on the hematology parameters of mice (strain C57BL/6) in samples taken within 24 h of blood collection. TK parameters were similar in plasma samples collected via CMS and cardiac puncture sampling. A bioanalytical assay was developed which enabled the quantification of concentration of both the parent drug and a metabolite using only 5-µL plasma sample per analysis. Incurred sample reanalysis (ISR), unexpected event investigation, and re-assay were successfully performed on the limited samples (≤ 20 µL) collected from CMS. The results of this study confirmed the feasibility of implementing CMS in regulated mouse toxicity studies and demonstrated that it is possible to eliminate or reduce satellite animals.

Adverse vacuolation in multiple tissues in cynomolgus monkeys following repeat-dose administration of a PEGylated protein.

PEGylation is considered a safe mechanism to enhance the pharmacokinetics (PK) and pharmacodynamics (PD) of biotherapeutics. Previous studies using PEGylation as a PK enhancement tool have reported benign PEG-related vacuolation in multiple tissues. This paper establishes a threshold for PEG burden beyond which there are alterations in tissue architecture that could potentially lead to dysfunction. As part of the nonclinical safety assessment of Compound A, a 12 kDa protein conjugated to a 40 kDa branched PEG molecule, monkeys were dosed subcutaneously twice weekly for 3 months at protein doses resulting in weekly PEG doses of 8, 24, 120, or 160 mg/kg. Consistent with previous reports with PEGylated biomolecules, Compound A administration resulted in intracellular vacuoles attributed to the PEG moiety in macrophages in numerous tissues and epithelial cells in the choroid plexus and kidney. Vacuolation occurred at all doses with dose-dependent severity and no evidence of recovery up to 2 months after dosing cessation. The vacuolation was considered nonadverse at PEG doses ≤120 mg/kg/week. However, at 160 mg/kg/week PEG, the vacuolation in choroid plexus, pituitary gland, kidney, and choroid of the eye was considered adverse due to significant alterations of tissue architecture that raised concern for the possibility of compromised tissue function. To our knowledge, this is the first report of potentially adverse cellular consequences of PEG accumulation in tissues other than kidney. Furthermore, the lack of reversibility of vacuolation coupled with the lack of a biomarker for intracellular PEG accumulation highlights a potential risk that should be weighed against the benefits of PK/PD enhancement for long-term administration of PEGylated compounds at high doses.

A practical workflow for capillary microsampling in nonclinical studies.

Aim: The result of investigation on the procedure of sample handling and bioanalysis of small volume of plasma sample for nonclinical studies stored in 0.5-ml micronic tubes was reported. Results/methodology: Sample integrity of the small volume (25 µl) during long-term storage and the feasibility and data reliability of performing multiple re-assays on the small volume sample using 5 µl aliquot per analysis was evaluated. Conclusion: Integrity was maintained in samples (25 µl) stored for up to 1 month in 0.5-ml micronic tubes at -20°C. A 25 µl sample is sufficient for four-times of re-assays. This evaluation demonstrated the feasibility of this workflow of handling and bioanalysis on small volume plasma sample for GLP studies under the US FDA guidance.

Evaluation of Uracil, Sodium Ascorbate, and Rosiglitazone as Promoters of Urinary Bladder Transitional Cell Carcinomas in Male Sprague-Dawley Rats.

The purpose of this study was to establish a 2-stage model of urinary bladder carcinogenesis in male Sprague-Dawley rats to identify tumor promoters. In phase 1 of the study, rats ( n = 170) were administered 100 mg/kg of the tumor initiator, N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), twice weekly by oral gavage (po) for a period of 6 weeks. Phase 2 consisted of dividing rats into 4 groups ( n = 40 per group) and administering one of the following for 26 weeks to identify putative tumor promoters: (1) vehicle po, (2) 25 mg/kg/day rosiglitazone po, (3) 5% dietary sodium l-ascorbate, and (4) 3% dietary uracil. Rats were necropsied after 7.5 months, and urinary bladders were evaluated by histopathology. BBN/vehicle treatments induced the development of urothelial hyperplasia (83%) and papillomas (15%) but no transitional cell carcinomas (TCCs). Rosiglitazone increased the incidence and severity of papillomas (93%) and resulted in TCC in 10% of treated rats. Uracil was the most effective tumor promoter in our study and increased the incidence of papillomas (90%) and TCC (74%). Sodium ascorbate decreased the incidence of urothelial hyperplasia (63%) and did not increase the incidence of urothelial papillomas or TCC. These data confirm the capacity of our 2-stage model to identify urinary bladder tumor promoters.

Serum microRNAs-217 and -375 as biomarkers of acute pancreatic injury in rats.

Pancreatic injury in rats is primarily detected through histopathological changes and conventional serum biomarkers such as amylase and lipase. However, amylase and lipase have a short half-life and are markers of acinar, not islet cell injury. We investigated whether circulating microRNA (miR) levels that are enriched in acinar cells (miR-217, miR-216a/b) or islet cells (miR-375) could serve as markers of pancreatic injury. Rats were treated with a single dose of either vehicle, streptozotocin (STZ), caerulein, or acetaminophen (APAP), and necropsied at 4, 24, and 48h. Pancreas, liver, heart, kidney and skeletal muscle were analyzed for histopathology. Blood was collected at necropsy and processed to serum for amylase/lipase enzymatic determinations and miR qPCR analysis. Caerulein induced degeneration/necrosis of acinar cells at 4h that persisted for 48h. Caerulein-induced injury was associated with increases in serum amylase/lipase (4h), miR-216a/b (4, 24h). In contrast, serum miR-217 was detected at all time points examined. STZ did not induce increases in either amylase or lipase but did induce increases in miR-375 levels at 4 and 24h. No increases in miR-375 were observed in caerulein-treated rats, and no increases were observed in miR-217 and miR-216a/b in STZ-treated rats. APAP induced centrilobular necrosis in the liver 24h after treatment, but did not induce pancreatic injury or increases in miR-217 or miR-375. Our results suggest that miR-217 and miR-375 represent promising biomarkers of pancreatic injury in rats.

Evaluation of microRNAs-208 and 133a/b as differential biomarkers of acute cardiac and skeletal muscle toxicity in rats.

Conventional circulating biomarkers of cardiac and skeletal muscle (SKM) toxicity lack specificity and/or have a short half-life. MicroRNAs (miRNAs) are currently being assessed as biomarkers of tissue injury based on their long half-life in blood and selective expression in certain tissues. To assess the utility of miRNAs as biomarkers of cardiac and SKM injury, male Sprague-Dawley rats received a single dose of isoproterenol (ISO); metaproterenol (MET); allylamine (AAM); mitoxantrone (MIT); acetaminophen (APAP) or vehicle. Blood and tissues were collected from rats in each group at 4, 24 and 48h. ISO, MET, and AAM induced cardiac and SKM lesions and APAP induced liver specific lesions. There was no evidence of tissue injury with MIT by histopathology. Serum levels of candidate miRNAs were compared to conventional serum biomarkers of SKM/cardiac toxicity. Increases in heart specific miR-208 only occurred in rats with cardiac lesions alone and were increased for a longer duration than cardiac troponin and FABP3 (cardiac biomarkers). ISO, MET and AAM induced increases in MyL3 and skeletal muscle troponin (sTnl) (SKM biomarkers). MIT induced large increases in sTnl indicative of SKM toxicity, but sTnl levels were also increased in APAP-treated rats that lacked SKM toxicity. Serum levels of miR-133a/b (enriched in cardiac and SKM) increased following ISO, MET, AAM and MIT treatments but were absent in APAP-treated rats. Our results suggest that miR-133a/b are sensitive and specific markers of SKM and cardiac toxicity and that miR-208 used in combination with miR-133a/b can be used to differentiate cardiac from SKM toxicity.

Utilization of the Zucker Diabetic Fatty (ZDF) Rat Model for Investigating Hypoglycemia-related Toxicities.

Glucokinase (GK) catalyzes the initial step in glycolysis and is a key regulator of glucose homeostasis. Therefore, glucokinase activators (GKa) have potential benefit in treating type 2 diabetes. Administration of a Bristol-Myers Squibb GKa (BMS-820132) to healthy euglycemic Sprague-Dawley (SD) rats and beagle dogs in 1 mo toxicology studies resulted in marked and extended hypoglycemia with associated clinical signs of toxicity and degenerative histopathological changes in the stomach, sciatic nerve, myocardium, and skeletal muscles at exposures comparable to those expected at therapeutic clinical exposures. To investigate whether these adverse effects were secondary to exaggerated pharmacology (prolonged hypoglycemia), BMS-820132 was administered daily to male Zucker diabetic fatty (ZDF) rats for 1 mo. ZDF rats are markedly hyperglycemic and insulin resistant. BMS-820132 did not induce hypoglycemia, clinical signs of hypoglycemia, or any of the histopathologic adverse effects observed in the 1 mo toxicology studies at exposures that exceeded those observed in SD rats and dogs. This indicates that the toxicity observed in euglycemic animals was secondary to the exaggerated pharmacology of potent GK activation. This study indicates that ZDF rats, with conventional toxicity studies, are a useful disease model for testing antidiabetic agents and determining toxicities that are independent of prolonged hypoglycemia.

Comparison of physiologic and pharmacologic parameters in Asian and mauritius cynomolgus macaques.

This comparative study was conducted to assess background physiologic and pharmacologic parameters of cynomolgus macaques (Macaca fascicularis) from Cambodia, from a mixed Asian source (Cambodia, Vietnam and Indonesia), and from Mauritius. This evaluation provides a comprehensive assessment of several of these parameters in a single study. Ten male and 10 female captive-bred, age-matched macaques from each source were evaluated. Criteria for evaluation included weight gain, assessment of drug metabolizing enzyme activity, metabolomic analysis, immunologic assessments (lymphocyte subsets, TDAR, and serum Ig isotyping), clinical pathology evaluations, physical (respiratory, neurologic, cardiovascular, and ophthalmologic) examinations, pathogen screening, organ weights, and gross and microscopic pathology analyses. The results of this evaluation indicate that, compared to macaques of Asian origin, macaques from Mauritius had the lowest incidence and/or severity of spontaneous pathologic findings in several organs and tissues (lymphoid organs, stomach, kidney, urothelium, heart, arteries and lung) and better testicular maturity at a given age with minimal variability in organ weights. Although slight differences were observed in other parameters, none were considered detrimental to the use of macaques of Asian or Mauritius origin in pharmaceutical candidate safety studies with the use of a consistent source, concomitant controls, and appropriate background knowledge and screening.

Use of animals for toxicology testing is necessary to ensure patient safety in pharmaceutical development.

There is an active debate in toxicology literature about the utility of animal testing vis-a-vis alternative in vitro paradigms. To provide a balanced perspective and add to this discourse it is important to review the current paradigms, explore pros and cons of alternatives, and provide a vision for the future. The fundamental goal of toxicity testing is to ensure safety in humans. In this article, IQ Consortium DruSafe, while submitting the view that nonclinical testing in animals is an important and critical component of the risk assessment paradigm in developing new drugs, also discusses its views on alternative approaches including a roadmap for what would be required to enhance the utilization of alternative approaches in the safety assessment process.

Occurrence of spontaneous pancreatic lesions in normal and diabetic rats: a potential confounding factor in the nonclinical assessment of GLP-1-based therapies.

Glucagon-like peptide 1-based therapies, collectively described as incretins, produce glycemic benefits in the treatment of type 2 diabetes. Recent publications raised concern for a potential increased risk of pancreatitis and pancreatic cancer with incretins based in part on findings from a small number of rodents. However, extensive toxicology assessments in a substantial number of animals dosed up to 2 years at high multiples of human exposure do not support these concerns. We hypothesized that the lesions being attributed to incretins are commonly observed background findings and endeavored to characterize the incidence of spontaneous pancreatic lesions in three rat strains (Sprague-Dawley [S-D] rats, Zucker diabetic fatty [ZDF] rats, and rats expressing human islet amyloid polypeptide [HIP]; n = 36/group) on a normal or high-fat diet over 4 months. Pancreatic findings in all groups included focal exocrine degeneration, atrophy, inflammation, ductular cell proliferation, and/or observations in large pancreatic ducts similar to those described in the literature, with an incidence of exocrine atrophy/inflammation seen in S-D (42-72%), HIP (39%), and ZDF (6%) rats. These data indicate that the pancreatic findings attributed to incretins are common background findings, observed without drug treatment and independent of diet or glycemic status, suggesting a need to exercise caution when interpreting the relevance of some recent reports regarding human safety.