Michael Graziano

Cartilage Dysplasia and Tissue Mineralization in the Rat Following Administration of a FGF Receptor Tyrosine Kinase Inhibitor

PD176067 is a reversible and selective inhibitor of fibroblast growth factor receptor tyrosine kinase, and was in preclinical development as an angiogenesis inhibitor for the treatment of solid tumors. A 14-day oral toxicity study of PD176067 in young female rats (7 weeks old) was conducted at doses of 2.5, 5, and 10 mg/kg/day (15, 30, and 60 mg/m2, respectively). Skeletal changes, and vascular and soft tissue mineralization were observed as primary drug-related toxicities. To determine if these changes are specific to young, rapidly growing animals with increased vascular and osseous development, PD176067 was administered to mature (11 months old) rats. Female rats received PD176067 by gavage for 14 days at doses of 2.5, 5, and 10 mg/kg/day and necropsied on day 15. Clinical signs of toxicity were seen at ≥5 mg/kg and one death occurred at 10 mg/kg. Physeal dysplasia (distal femur, proximal tibia, sternum) occurred in all drug-treated animals and was characterized by dose-related increased thickness of the zones of chondrocyte proliferation and hypertrophy, and marked thickening of the zone of ossification. Cartilage hyperplasia was characterized by proliferation of chondrocytes along margins of the synchondrosis and subperiosteum of sternebrae. Serum phosphorus levels increased 47% and 166% at 5 and 10 mg/kg, respectively. Mineralization of cardiac myocytes, aorta, various arteries, renal tubules, and gastric mucosa and muscularis was seen at 10 mg/kg, and consistent with the presence of calcium-phosphorus deposition. Physeal changes occurred at similar plasma PD176067 exposures in young and mature rats (AUC ≥ 4.83 μg · hr/mL). PD176067 produced morphologically similar lesions in young and adult rats.

Retinal degeneration in rats induced by CI-1010, a 2-nitroimidazole radiosensitizer

The anti-cancer compound CI-1010, designated as (R)-α-([(2-bromoethyl)amino]methyl)-2-nitro-]H-imidazole-l-ethanol monohydrobromide, has a proposed dual mechanism of action due to alkylating and radiosensitizing activities. To assess potential toxicity, adult Wistar rats were treated with a single intravenous injection (0, 50, 100, 150, 225, or 350 mg/kg) and necropsied at 4 or 29 days following treatment. In a repeated dose experiment, rats were injected daily (0, 10, 40, or 80 mg/kg; 5 doses/wk) for 3 wk and necropsied at the end of week 3 or 7. CI-1010 induced retinal degeneration by 4 days after a single injection of ≥225 mg/kg or by 3 wk of repeated injections of ≥40 mg/kg. The locally extensive to diffuse retinal degeneration involved the photoreceptor and outer nuclear layer. The photoreceptor layer was vacuolated and compressed corresponding to ultrastructural evidence of inner segment swelling and outer segment fragmentation. The outer nuclear layer was thinned due to loss of nuclei and contained numerous pyknotic or karyorrhectic nuclei. These nuclear changes were morphologically consistent with apoptosis and many outer nuclear layer nuclei labeled with in situ TdT-mediated dUTP-digoxigenin nick end labeling (Apoptag®). The retinal degeneration was nonreversible, evidenced by increased lesion severity and incidence after CI-1010 was withdrawn for either 25 or 28 days.

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.

Nonclinical Toxicology Assessments Support the Chronic Safety of Dapagliflozin, a First-in-Class Sodium-Glucose Cotransporter 2 Inhibitor

Dapagliflozin, a first-in-class, selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), promotes urinary glucose excretion to reduce hyperglycemia for the treatment of type 2 diabetes. A series of nonclinical studies were undertaken to evaluate dapagliflozin in species where it was shown to have pharmacologic activity comparable with that in humans at doses that resulted in supratherapeutic exposures. In vitro screening (>300 targets; 10 μmol/L) indicated no significant off-target activities for dapagliflozin or its primary human metabolite. Once daily, orally administered dapagliflozin was evaluated in Sprague-Dawley rats (≤6 months) and in beagle dogs (≤1 year) at exposures >5000-fold those observed at the maximum recommended human clinical dose (MRHD; 10 mg). Anticipated, pharmacologically mediated effects of glucosuria, osmotic diuresis, and mild electrolyte loss were observed, but there were no adverse effects at clinically relevant exposures, including in the kidneys or urogenital tract. The SGLT2−/− mice, which show chronic glucosuria, and dapagliflozin-treated, wild-type mice exhibited similar safety profiles. In rats but not dogs, dapagliflozin at >2000-fold MRHD exposures resulted in tissue mineralization and trabecular bone accretion. Investigative studies suggested that the effect was not relevant to human safety, since it was partially related to off-target inhibition of SGLT1, which was observed only at high doses of dapagliflozin and resulted in intestinal glucose malabsorption and increased intestinal calcium absorption. The rigorous assessment of supra- and off-target dapagliflozin pharmacology in nonclinical species allowed for a thorough evaluation of potential toxicity, providing us with confidence in its safety in patients with diabetes.

Advancing the 3Rs in regulatory toxicology - Carcinogenicity testing: Scope for harmonisation and advancing the 3Rs in regulated sectors of the European Union.

Different government agencies operating in the European Union regulate different types of chemical products but all require testing for carcinogenicity to support applications for product marketing and commercialisation. A conference was held in Brussels in 2013 where representatives of the pharmaceutical, animal health, chemical and plant protection industries, together with representatives of regulatory agencies, universities and other stakeholders, met under the auspices of The European Partnership for Alternative Approaches to Animal Testing (EPAA) to discuss the varying requirements for carcinogenicity testing, and how these studies might be refined to improve hazard evaluation and risk assessment while implementing principles of the 3Rs (replacement, refinement and reduction in animal studies). While there are some similarities, the regulatory approaches in pharmaceutical, animal health, chemical and plant protection sectors have varying degrees of flexibility in requirements for carcinogenicity testing, to an extent reflecting concerns over the magnitude and duration of human exposure, either directly as in therapeutic exposure to pharmaceuticals, or indirectly through the ingestion of residues of veterinary drugs or plant protection chemicals. The article discusses these differences and other considerations for modified carcinogenicity testing paradigms on the basis of scientific and 3Rs approaches.

Hemangiosarcoma in Mice Administered Pregabalin: Analysis of Genotoxicity, Tumor Incidence, and Tumor Genetics

Pregabalin, (S)-3-(aminomethyl)-5-methylhexanoic acid, binds with high affinity to the α(2)δ subunit of voltage-gated calcium channels and exerts analgesic, anxiolytic, and antiseizure activities. Two-year carcinogenicity studies were completed in B6C3F1 and CD-1 mice and two separate studies in Wistar rats. Doses in mice were 200, 1000, and 5000 mg/kg/day, with systemic exposures (AUC(0-24 h)) up to 31 times the mean exposure in humans, given the maximum recommended clinical dose. In rats, doses were 50, 150, and 450 mg/kg/day in males and 100, 300, and 900 mg/kg/day in females; systemic exposures up to 24 times were achieved in clinical trials. In both strains of mice, pregabalin treatment was associated with an increased incidence of hemangiosarcoma primarily in liver, spleen, and bone marrow. The incidence of hemangiosarcoma was higher in B6C3F1 mice than in CD-1 mice, consistent with its spontaneous incidence. Pregabalin did not increase the incidence of any other tumor type in rats and was not genotoxic, based on an extensive battery of in vivo and in vitro tests in bacterial and mammalian systems. Thus, pregabalin is a single-species, single tumor-type, nongenotoxic mouse carcinogen. Hemangiosarcomas occurring in mice treated with pregabalin were genotypically distinct from hemangiosarcomas induced by genotoxic carcinogens in humans with respect to ras and p53 mutation patterns and were similar to spontaneous tumors. Furthermore, there was a strong association between pregabalin treatment and bone marrow changes in these studies in mice, suggesting a possible link between the effects observed in bone marrow and the increase in tumor incidence in pregabalin-treated mice.

Cutaneous Lesions in the Rat Following Administration of an Irreversible Inhibitor of erbB Receptors, Including the Epidermal Growth Factor Receptor

CI-1033 (canertinib) is an irreversible inhibitor of the erbB family of transmembrane tyrosine kinase receptors, including the epidermal growth factor (EGF) receptor. Various inhibitors of the EGF receptor, including CI-1033, have resulted in cutaneous toxicity in humans as a common adverse event. In a chronic toxicity study in rats, CI-1033 produced cutaneous lesions with morphologic characteristics similar to that reported in man. Here the authors describe in detail the dermal changes observed, along with other noteworthy findings of that study. Male and female Wistar rats (15/sex/group) were administered CI-1033 for 27 weeks at 2.5, 5, or 10 mg/kg (15, 30, or 60 mg/m2, respectively) by gavage. Control animals (15/sex) received vehicle alone (aqueous 0.5% methylcellulose) in a dose volume of 5 mL/kg. Six animals/sex/dose were included for toxicokinetic evaluations. Skin lesions were the primary drug-related toxicity and occurred at ≥2.5 mg/kg in a dose-dependent fashion. The major gross lesions were papules that evolved into crusts and scales that were first observed in weeks 1 and 3, respectively. Alopecia developed in conjunction with the papular eruptions. Skin changes were most pronounced in females, possibly due to higher drug levels. In week 13, CI-1033 plasma AUC(0–24) values were 527 to 1980 ng·h/mL in males and 844 to 2920 ng·h/mL in females at 2.5 to 10 mg/kg. Microscopic changes could be described as 3 patterns that affected the tail and body (haired skin). Pattern 1 consisted of epidermal changes that started as a superficial, perivascular spongiotic dermatitis with evolving epidermal hyperplasia, scale-crusts, and areas of ulceration. Areas of hyperplasia on the tail were often associated with the development of new hair follicles. Pattern 2 was characterized by a suppurative to pyogranulomatous infundibular folliculitis. Pattern 3 consisted of abnormally oriented hair follicles with malformed hair shafts that were associated with a deeper (isthmic) folliculitis; this correlated with alopecia. Elevations in bone marrow myeloid counts correlated with a peripheral leukocytosis, consistent with inflammatory changes in the dermis. In addition, hepatic cholestasis and epithelial atrophy in the gastrointestinal tract and vagina occurred at ≥2.5 mg/kg. In conclusion, CI-1033 produced cutaneous lesions involving the epidermis and hair follicle, and the morphologic characteristics were similar to that reported in clinical studies with various inhibitors of the EGF receptor. These changes are consistent with pharmacologic inhibition of the EGF receptor in these tissues and demonstrate that the rat can serve as an animal model for investigating the mechanisms for this toxicity.

The glucagon‐like peptide‐1‐based therapeutics exenatide and saxagliptin did not cause detrimental effects on the pancreas in mice, rats, dogs and monkeys

Recent reports in the literature have suggested that glucagon‐like peptide‐1 (GLP‐1)‐based therapies may lead to increased risk of pancreatic pathology leading to chronic pancreatic injury and pancreatic neoplasia. Extensive non‐clinical and clinical safety testing was conducted to support the global development of exenatide twice daily, exenatide once weekly and saxagliptin. Our aim was to integrate these non‐clinical data obtained with both mechanisms of GLP‐1‐based drugs to provide complementary data regarding the potential for drug‐induced pancreatic safety signals.

Granular Basal Cell Tumor in a Wistar Rat

A granular cell variant of a cutaneous basal cell tumor in a Wistar rat is described. The tumor resembles the variant as described in man and dogs. The granular basal cells contain cytoplasmic PAS positive granules, and immunostained positively with HMW cytokeratins. Ultrastructurally, the cytoplasmic granules were secondary lysosomes.

The Use of Minipigs for Preclinical Safety Assessment by the Pharmaceutical Industry: Results of an IQ DruSafe Minipig Survey.

The use of minipigs in preclinical safety testing of pharmaceuticals is considered an alternative to the more traditional dog and nonhuman primate (NHP) nonrodent species. Substantial evidence exists to suggest that the anatomy, physiology, and biochemistry of minipigs are similar enough to humans to consider them as valid nonrodent models for pharmaceutical safety testing. Since the utilization of minipigs was last assessed over 5 years ago, the Preclinical Safety Leadership Group (DruSafe) of the International Consortium for Innovation and Quality in Pharmaceutical Development conducted this survey to provide an updated assessment of the utility, perceived value, and impediments to the use of minipigs in preclinical safety testing. Of the 32 participating members of DruSafe, 15 responded to the survey representing both large and small companies. Respondents indicated that the minipig has been utilized mostly for short-term safety assessment studies with dermal, oral, and parenteral routes of administration. Minipigs are widely accepted as appropriate models for cardiovascular assessments and have been used to a limited extent for reproductive toxicology testing. Overall responses indicated that safety testing for large molecules using this species is relatively low due to a lack of background data, reagents or biomarkers, concerns regarding immune system characterization and poor suitability for developmental toxicity assessments. Most companies utilized contract research organizations for definitive safety toxicity assessment studies. Conclusions of this survey indicate that minipig is an acceptable nonrodent species largely limited to studies using small molecules, primarily dermal products, and results are comparable to those reported 5 years ago.