Carcinogenicity Studies In Rats Research Articles

Histological analyses of the Ishii (1981) rat carcinogenicity study of aspartame and comparison with the Ramazzini Institute studies

Researchers from the Ramazzini Institute have reported that lifespan dosing of rats with aspartame treatment is associated with an increased overall incidence of malignant tumors, including leukemias/lymphomas, transitional cell carcinomas of the renal pelvis/ureter, and malignant schwannomas of the peripheral nerves. Other carcinogenicity studies conducted on aspartame have shown no such carcinogenic potential in any organ system. Additional data to assess the carcinogenic potential of aspartame, especially in relation to the publications of the Ramazzini Institute, were obtained from a third-party histological evaluation of tissues from a carcinogenicity study previously conducted to assess the potential for aspartame to induce tumors of the brain. The results of this histological evaluation provide no evidence of a tumorigenic effect of aspartame in any organ group, including those organs/tissues reportedly affected in the Ramazzini Institute's studies. The only effects identified were an increased incidence of renal pelvic mineralization and renal pelvic hyperplasia secondary to the irritant properties of the mineralization process. The toxicological significance of these particular findings is widely considered minimal. There is no evidence that aspartame is carcinogenic in rats, at least to doses of 4 g/kg body weight/day administered over a 2-year period.

Re-evaluation of oxidised soya bean oil interacted with mono- and diglycerides of fatty acids (E479b) as a food additive.

The EFSA Panel on Food Additives and Flavourings (FAF) provides a scientific opinion re‐evaluating the safety of thermally oxidised soya bean oil interacted with mono‐ and diglycerides of fatty acids (TOSOM) (E 479b) when used as a food additive. The Scientific Committee on Food (SCF) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) derived an acceptable daily intake (ADI) of 25 and 30 mg/kg body weight (bw) per day, respectively. There was no reliable information regarding the absorption, distribution, metabolism, excretion (ADME) for TOSOM. No adverse effects have been detected in a limited subchronic toxicity study in pigs. The Panel identified a no observed adverse effect level (NOAEL) of 5,400, the highest dose tested, from a chronic and carcinogenicity study in rats. No genotoxicity data were available. No reliable studies for reproductive or developmental toxicity were available. From the chronic and carcinogenicity study, no lesions in reproductive organs were described and the lack of carcinogenic effect alleviated the concern for genotoxicity at the first site of contact. The Panel concluded that the available toxicological data were insufficient to support the current ADI, in particular, due to the lack of ADME data and absence of developmental toxicity studies TOSOM (E 479b) is only authorised in one food category and only one reported use level that equals the maximum permitted level was submitted. The estimated high (P95) exposure reached an upper value of 10.1 mg/kg bw per day for toddlers. When comparing the highest estimated exposure of 10 mg/kg bw per day in toddlers with the NOAEL of 5,400 mg/kg bw per day (the highest dose tested), the margin of safety (MoS) would be 540. Therefore, the Panel considered the use of TOSOM (E 479b) to be of no safety concern, in particular when considering the limited current use of this food additive. The Panel also recommended some modifications of the EU specifications for E 479b.

Mechanisms of Rodent Renal Carcinogenesis Revisited.

The important renal tumors that can be induced by exposure of rats to chemical carcinogens are renal tubule tumors (RTTs) derived from tubule epithelium; renal pelvic carcinoma derived from the urothelial lining of the pelvis; renal mesenchymal tumors (RMTs) derived from the interstitial connective tissue; and nephroblastoma derived from the metanephric primordia. However, almost all of our knowledge concerning mechanisms of renal carcinogenesis in the rodent pertains to the adenomas and carcinomas originating from renal tubule epithelium. Currently, nine mechanistic pathways can be identified in either the rat or mouse following chemical exposure. These include direct DNA reactivity, indirect DNA reactivity through free radical formation, multiphase bioactivation involving glutathione conjugation, mitotic disruption, sustained cell proliferation from direct cytotoxicity, sustained cell proliferation by disruption of a physiologic process (alpha 2u-globulin nephropathy), exaggerated pharmacologic response, species-dominant metabolic pathway, and chemical exacerbation of chronic progressive nephropathy. Spontaneous occurrence of RTTs in the rat will be included since one example is a confounder for interpreting kidney tumor results in chemical carcinogenicity studies in rats.

Verification of a false positive in a two-year rat carcinogenicity study using dual control groups.

There is sometimes controversy over whether or not statistically significant responses produced in carcinogenicity studies have biologically significance. Ambiguous results from our previous two-year oral carcinogenicity study on acotiamide hydrochloride hydrate (acotiamide-HH), a prokinetic drug for functional dyspepsia, in rats made it unclear whether the drug may exhibit uterine carcinogenicity. To check this finding, we performed a second long-term carcinogenicity study using two identical control groups to more accurately evaluate uterine carcinogenesis by considering the incidence of spontaneous neoplasms. Female Fischer 344 rats were divided into three groups: the two control groups (control 1 and 2) were administered vehicle (0.5% w/v methylcellulose) and the acotiamide-HH-treated group was administered 2,000 mg/kg/day of acotiamide-HH by oral gavage for two years. Among all groups, the incidence of endometrial adenocarcinoma (EmA) was highest in the control 2 group, followed by the acotiamide-HH-treated group and the control 1 group. Moreover, acotiamide-HH did not affect the incidence of precursor lesions of EmA. In cases where an ambiguous difference is observed, the use of two control groups allows for a more informed interpretation of the findings in the drug-treated groups. The outcomes in this study strongly support the hypothesis that the increase in EmA in rats treated with acotiamide-HH in our previous study is unrelated to administration of the drug.

Morphological and immunohistochemical diversity of endometrial stromal sarcoma in rats.

To clarify the histopathological characteristics of rat endometrial stromal sarcoma (ESS), we morphologically reviewed 12 malignant uterine tumors protruding into the lumen in previous rat carcinogenicity studies. The 12 cases were classified into the following 6 types based on their morphological features: spindle cell and collagen rich type, pleomorphic/spindle cell and compact type, decidual alteration type, histiocytic and multinucleated giant cell mixture type, Antoni A-type schwannoma type, and Antoni B-type schwannoma type. Immunohistochemically, tumor cells in all cases exhibited focal or diffuse positive reactions for vimentin, and 11 of the 12 cases were positive for S-100. Interestingly, 9 cases were positive for desmin or αSMA, indicating tumor cells expressing smooth muscle properties. Both Antoni A- and B-type schwannoma types showed low reactions for both muscle markers. Positive results for estrogen receptor α in the 11 cases suggested that they were derived from endometrial stromal cells. On the basis of their immunohistochemical profiles, they were considered to be derived from endometrial stromal cells while they showed morphological variation. The detection of a basement membrane surrounding tumor cells might not be a definitive indicator for differential diagnosis of ESS from malignant schwannoma. In conclusion, ESS could exhibit wide morphological and immunohistochemical variation including features of schwannoma or smooth muscle tumor.

Progression process and safety assessment adaptation of endometrial lesions in ENU-induced 2-stage uterine carcinogenicity in a Tg-rasH2 mouse model.

Although acotiamide hydrochloride hydrate (acotiamide-HH) has not been reported to have genotoxic findings in any of the genotoxicity studies or treatment-related toxicological findings in reproductive and developmental studies, suspicious uterine tumorigenesis was observed in the results of a long-term rat carcinogenicity study. To clarify the uterine tumorigenesis of acotiamide-HH, we performed a 2-stage uterine carcinogenicity model in the transgenic rasH2 mouse initiated by N-Ethyl-N-nitrosourea (ENU). This model facilitated the short-term detection of uterine carcinogenic potential, and it appears to be a very useful testing method for assessing the safety of chemicals that may affect uterine tumorigenesis. However, there have not been many reports on this model, and accumulation of case studies using this model is recommended to support its usability. In this study, we performed this carcinogenesis model to not only confirm uterine tumorigenesis of acotiamide-HH but also to confirm the reliability of the model. The results of this study revealed that the endometrial adenocarcinoma found in the long-term rat carcinogenicity study possibly arose spontaneously. Also, we confirmed early induction of a uterine tumor as in previous reports and confirmed that 26 weeks is the appropriate treatment period for this rasH2 mouse model according to time-course observations of uterine tumor development.

Re-evaluation of sodium nitrate (E 251) and potassium nitrate (E 252) as food additives.

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re‐evaluating the safety of sodium nitrate (E 251) and potassium nitrate (E 252) when used as food additives. The current acceptable daily intakes (ADIs) for nitrate of 3.7 mg/kg body weight (bw) per day were established by the SCF (1997) and JECFA (2002). The available data did not indicate genotoxic potential for sodium and potassium nitrate. The carcinogenicity studies in mice and rats were negative. The Panel considered the derivation of an ADI for nitrate based on the formation of methaemoglobin, following the conversion of nitrate, excreted in the saliva, to nitrite. However, there were large variations in the data on the nitrate‐to‐nitrite conversion in the saliva in humans. Therefore, the Panel considered that it was not possible to derive a single value of the ADI from the available data. The Panel noticed that even using the highest nitrate‐to‐nitrite conversion factor the methaemoglobin levels produced due to nitrite obtained from this conversion would not be clinically significant and would result to a theoretically estimated endogenous N‐nitroso compounds (ENOC) production at levels which would be of low concern. Hence, and despite the uncertainty associated with the ADI established by the SCF, the Panel concluded that currently there was insufficient evidence to withdraw this ADI. The exposure to nitrate solely from its use as a food additive was estimated to be less than 5% of the overall exposure to nitrate in food based on a refined estimated exposure scenario. This exposure did not exceed the current ADI (SCF, 1997). However, if all sources of exposure to dietary nitrate are considered (food additive, natural presence and contamination), the ADI would be exceeded for all age groups at the mean and the highest exposure.

Non-neoplastic lesions found only in the two-year bioassays but not in shorter toxicity studies of rats

International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) has been conducting a prospective evaluation period to validate the criteria for waiving some carcinogenicity studies in rats. Before the waiving strategy is practiced in ICH, it is crucial to elucidate whether non-neoplastic lesions are found only in 2-year rat carcinogenicity studies. To confirm possible importance of 2-year bioassays for evaluating chronic toxicity but not carcinogenicity, we retrospectively surveyed 59 pharmaceuticals approved by the Ministry of Health, Labour and Welfare (MHLW) from 2007 to 2010 in Japan for non-neoplastic lesions observed in carcinogenicity studies. Non-neoplastic histopathological lesions observed only in 2-year carcinogenicity studies but not in 6-month chronic toxicity studies using rats were compared with clinical adverse drug reactions (ADRs). Thirteen non-neoplastic lesions that may correlate with clinical ADRs were classified into three categories: Category 1, lesions not predictable from other nonclinical data except those from 2-year rat carcinogenicity studies; Category 2, lesions predictable mainly from chronic toxicity studies; Category 3, lesions predictable mainly from pharmacological actions. In the present survey, non-neoplastic lesions only found in 2-year rat carcinogenicity studies were neither significant in terms of frequency and severity nor useful for clinical risk management.

Non-clinical safety evaluation and risk assessment to human of aleglitazar, a dual PPAR α/γ agonist, and its major human metabolite

The non-clinical safety profile of aleglitazar, a peroxisome proliferator activated receptor alpha/gamma agonist, and its major human metabolite M6 was studied in a complete package consisting of drug metabolism and pharmacokinetics characterization, safety pharmacology, genotoxicity, repeat dose toxicity, reproductive toxicity and carcinogenicity studies. These studies identified the following main targets similar to other PPAR agonists: red blood cell parameters, liver, heart, kidney, ovaries, testes, bone marrow, adipose tissue, and fluid accumulation. Additionally, and in the 12-month monkey study only, an increased incidence of generalized hair loss/thinning was observed in all groups including controls. In the rat carcinogenicity study there was no statistically significant increase in tumors. In the mouse carcinogenicity study, there was an increased incidence of angiomatous tumors and there were three males with gallbladder adenoma. No relevant compound-related effects were observed in safety pharmacology, genotoxicity, and a 28-day immunotoxicity rat study. Effects observed in reproductive toxicity studies were similar to those known for other PPARγ agonists. Separate studies with the human metabolite M6 did not reveal findings that would prevent human dosing. Overall, the results from the non-clinical safety studies conducted with aleglitazar and the human metabolite M6 were considered to support the clinical Phase 3 program.

Regulatory Forum.

Revision of the International Council for Harmonization (ICH) S1 guidance for rat carcinogenicity studies to be more selective of compounds requiring a 2-year rat carcinogenicity study has been proposed following extensive evaluation of rat carcinogenicity and chronic toxicity studies by industry and drug regulatory authorities. To inform the ICH S1 expert working group in their potential revision of ICH S1, a prospective evaluation study was initiated in 2013, in which sponsors would assess the pharmacologic and toxicologic findings present in the chronic toxicity studies and predict a positive or negative carcinogenicity outcome using a weight of evidence argument (a carcinogenicity assessment document [CAD]). The Scientific and Regulatory Policy Committee was asked by the Society of Toxicology Pathology (STP) executive committee to track these changes with ICH S1 and inform the STP membership of status changes. This commentary is intended to provide a brief summary of recent changes to the CAD guidance and highlight the importance of STP membership participation in the process of CAD submissions.

Effects of the Janus Kinase Inhibitor, Tofacitinib, on Testicular Leydig Cell Hyperplasia and Adenoma in Rats, and on Prolactin Signaling in Cultured Primary Rat Leydig Cells.

Tofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis. Tofacitinib preferentially inhibits receptor signaling through JAK3 and JAK1, relative to JAK2. In the 2-year rat carcinogenicity study, there were tofacitinib, dose-related increases in the incidences of testicular Leydig cell hyperplasia and benign adenomas in male rats, and decreased incidences of mammary tumors and duct dilatation/galactocele in female rats. Such findings in rats are typical of agents, such as dopamine agonists, which decrease prolactin (PRL) activity. Since prolactin signals through the JAK2 pathway, we hypothesized that these findings were off-target effects due to inhibition of PRL signaling via JAK2. The studies reported here were designed to investigate the interruption of PRL signaling pathways in Leydig cells. In isolated primary rat Leydig cells, PRL increased phosphorylated Signal Transducer and Activator of Transcription-5 protein, and mRNA levels for luteinizing hormone receptor. Tofacitinib, at concentrations observed in the rat carcinogenicity study, dose-dependently inhibited these effects. These observations illustrate a novel mechanism, the inhibition of prolactin signaling by which modulation of JAK activity can modulate PRL signaling pathways to induce Leydig cell tumors in rats. Since human Leydig cells lack this PRL dependence for normal function, these rodent tumors do not indicate a health risk to human patients.

Prediction of carcinogenic potential of chemicals using repeated-dose (13-week) toxicity data

Sub-chronic toxicity studies of 163 non-genotoxic chemicals were evaluated in order to predict the tumour outcome of 24-month rat carcinogenicity studies obtained from the EFSA and ToxRef databases. Hundred eleven of the 148 chemicals that did not induce putative preneoplastic lesions in the sub-chronic study also did not induce tumours in the carcinogenicity study (True Negatives). Cellular hypertrophy appeared to be an unreliable predictor of carcinogenicity. The negative predictivity, the measure of the compounds evaluated that did not show any putative preneoplastic lesion in de sub-chronic studies and were negative in the carcinogenicity studies, was 75%, whereas the sensitivity, a measure of the sub-chronic study to predict a positive carcinogenicity outcome was only 5%. The specificity, the accuracy of the sub-chronic study to correctly identify non-carcinogens was 90%. When the chemicals which induced tumours generally considered not relevant for humans (33 out of 37 False Negatives) are classified as True Negatives, the negative predictivity amounts to 97%. Overall, the results of this retrospective study support the concept that chemicals showing no histopathological risk factors for neoplasia in a sub-chronic study in rats may be considered non-carcinogenic and do not require further testing in a carcinogenicity study.

農薬評価におけるマウス発がん性試験の必要性、I. ラット発がん性試験に追加の意義

農薬評価におけるマウス発がん性試験の必要性、I. ラット発がん性試験に追加の意義

Evaluation of potential activity of luseogliflozin on vascular proliferation in the mesenteric lymph node with or without vascular tumors in Sprague-Dawley rats in a carcinogenicity study.

The incidence of mesenteric lymph node vascular tumors can vary in rats, and appropriate assessment of potential risk of tumorigenicity is needed when the incidence is higher in treated groups than in a control group. In a 2-year rat carcinogenicity study of luseogliflozin, a selective sodium-dependent glucose co-transporter 2 inhibitor for the treatment of type 2 diabetes mellitus, there was a slight but statistically significant increase in the total number of hemangiomas and hemangiosarcomas in the mesenteric lymph nodes in males at a high-dose. As part of the risk assessment for luseogliflozin, its effect on the vascular proliferation potential in the mesenteric lymph nodes was examined in a rat carcinogenicity study by performing an image analysis using specimens with double immunohistochemical staining for PCNA and CD34 in control and high-dose males. In addition, immunohistochemical staining for VEGF was performed to detect enhanced angiogenesis. In the high-dose males that did not have a hemangioma/hemangiosarcoma, neither an increased number of PCNA/CD34-positive cells nor changes in the expression pattern of VEGF was observed. On the other hand, in the high-dose males that had a hemangioma/hemangiosarcoma, the number of PCNA-positive cells was increased in the tumor areas, and the number in the hemangioma/hemangiosarcoma was approximately one-half of that in the hemangiosarcoma in the control male. In conclusion, no potential change leading to vascular proliferation/tumors was detected in the mesenteric lymph nodes of high-dose males receiving luseogliflozin.

Review of genotoxicity and rat carcinogenicity investigations with astaxanthin

Synthetic astaxanthin has been extensively tested for safety. Genotoxicity studies including Ames and in vitro Micronucleus Tests show absence of genotoxic potential. Although a long-term mouse study showed no carcinogenicity potential, the rat carcinogenicity study with dietary dosages of 0 (control), 0 (placebo beadlet), 40, 200 and 1000 mg astaxanthin/kg bw/day showed an increased incidence of benign, hepatocellular adenoma in females only, at 200 mg/kg bw/day and above. There was no clear evidence of toxicity during the in-life phase. Discoloration of feces was observed and a reduction in body weight gain in all groups receiving beadlets, probably reflecting a nutritional influence. Blood sampling confirmed systemic exposure and some minor clinical chemistry differences in females at 200 and 1000 mg/kg bw/day. There was no effect on adjusted liver weight. Histopathological examination showed hepatic changes indicative of slight hepatotoxicity and hepatocyte regeneration in females at 200 and 1000 mg/kg bw/day, in addition to the adenoma. Taking into account this pathological background in the female rat, and a wide variety of other supporting information, it is concluded that the hepatocellular adenoma in female rats was secondary to hepatotoxicity and regeneration, and is most probably a species-specific phenomenon of doubtful human relevance.

Scientific Opinion on the re‐evaluation of polyoxyethylene sorbitan monolaurate (E 432), polyoxyethylene sorbitan monooleate (E 433), polyoxyethylene sorbitan monopalmitate (E 434), polyoxyethylene sorbitan monostearate (E 435) and polyoxyethylene sorbitan tristearate (E 436) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) re-evaluated the safety of polysorbate 20 (E 432), polysorbate 80 (E 433), polysorbate 40 (E 434), polysorbate 60 (E 435) and polysorbate 65 (E 436) as food additives. The Joint Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) derived an Acceptable Daily Intake (ADI) of 25 mg/kg body weight (bw)/day (group ADI for polysorbates 20, 40, 60, 65 and 80) and the Scientific Committee on Food (SCF) derived a group ADI of 10 mg/kg bw/day. Small amounts of polyoxyethylene sorbitans are absorbed. Similar toxicokinetics would be expected for all polysorbates based on their similarities in structure and metabolic fate. The acute toxicity is very low. There is no concern regarding genotoxicity, carcinogenicity or developmental toxicity. From a limited number of studies, there is no indication of reproductive toxicity. The Panel considered the long-term carcinogenicity study in rats with a No Observed Adverse Effect Level (NOAEL) equivalent to 2 500 mg/kg bw/day – consistent with the NOAEL defined in subchronic studies – as the key study and allocated a group ADI of 25 mg/kg bw/day using an uncertainty factor of 100. The estimated exposure of toddlers at the highest level in non-brand loyal scenario remains very close to the ADI (24.5 mg/kg bw/day). The Panel is aware that for three food categories no reported uses have been obtained and that other dietary sources of exposure to polysorbates could not been considered in this opinion and therefore more data (usage and analytical data) are needed to decrease uncertainties in the refined exposure assessment scenario used.

Chronic Toxicity and Carcinogenicity Studies of the Long-Acting GLP-1 Receptor Agonist Dulaglutide in Rodents.

The tumorigenic potential of dulaglutide was evaluated in rats and transgenic mice. Rats were injected sc twice weekly for 93 weeks with dulaglutide 0, 0.05, 0.5, 1.5, or 5 mg/kg corresponding to 0, 0.5, 7, 20, and 58 times, respectively, the maximum recommended human dose based on plasma area under the curve. Transgenic mice were dosed sc twice weekly with dulaglutide 0, 0.3, 1, or 3 mg/kg for 26 weeks. Dulaglutide effects were limited to the thyroid C-cells. In rats, diffuse C-cell hyperplasia and adenomas were statistically increased at 0.5 mg/kg or greater (P ≤ .01 at 5 mg/kg), and C-cell carcinomas were numerically increased at 5 mg/kg. Focal C-cell hyperplasia was higher compared with controls in females given 0.5, 1.5, and 5 mg/kg. In transgenic mice, no dulaglutide-related C-cell hyperplasia or neoplasia was observed at any dose; however, minimal cytoplasmic hypertrophy of C cells was observed in all dulaglutide groups. Systemic exposures decreased over time in mice, possibly due to an antidrug antibody response. In a 52-week study designed to quantitate C-cell mass and plasma calcitonin responses, rats received twice-weekly sc injections of dulaglutide 0 or 5 mg/kg. Dulaglutide increased focal C-cell hyperplasia; however, quantitative increases in C-cell mass did not occur. Consistent with the lack of morphometric changes in C-cell mass, dulaglutide did not affect the incidence of diffuse C-cell hyperplasia or basal or calcium-stimulated plasma calcitonin, suggesting that diffuse increases in C-cell mass did not occur during the initial 52 weeks of the rat carcinogenicity study.

Mode of action and human relevance of pronamide-induced rat thyroid tumors

Pronamide, a selective, systemic, pre- and post-emergence herbicide, caused an increased incidence of thyroid follicular cell adenomas in a rat carcinogenicity study. Thyroid tumors, as well as liver and pituitary changes, were limited only to the high-dose group. The evidence for and against specific potential modes of action (MoAs) for rat thyroid follicular cell adenomas and their relevance to humans is discussed. Pronamide is not mutagenic and therefore, direct DNA reactivity is not relevant as a MoA. The hypothesized MoA for this effect is altered homeostasis of the hypothalamic–pituitary–thyroid (HPT) axis mediated by the induction of hepatic enzymes, including uridine diphosphate glucuronosyltransferase (UGT). Evaluation of data from a series of regulatory guideline and MoA studies aimed at identifying the causative and associated key events supported a UGT-mediated MoA in the development of thyroid follicular tumors. This MoA for pronamide-induced thyroid tumors in rats, which involves increased thyroid hormone metabolism/clearance, altered thyroid hormone homeostasis and HPT stimulation is not considered relevant to humans based on quantitative species differences, making rats markedly more sensitive than humans to thyroid perturbations.

Mosapride

The Food Safety Commission of Japan (FSCJ) conducted a risk assessment of mosapride citrate (CAS No. 112885–42-4), a gastrointestinal agent, based on documents including a written application for marketing approval of a new veterinary medicinal product. Although hepatocellular and thyroid follicular cell tumors were induced in carcinogenicity studies in rats and mice, no genotoxicities were suggested in all the studies of mosapride citrate. The involvement of genotoxic mechanism is thus unlikely. Therefore, an acceptable daily intake (ADI) for mosapride citrate is able to be specified. In a 26-week subacute toxicity study using both sexes of rats, the no-observed-adverse-effect level (NOAEL) and the lowest-observed-adverse-effect level (LOAEL) values were obtained, respectively, to be 2 mg/kg bw/day and 10 mg/kg bw/day for the female, and to be 10 mg/kg bw/day and 50 mg/kg bw/day for the male. However, hepatocellular swelling observed in the female in the 26-week subacute toxicity study was also observed in the 104-week carcinogenicity study in the male given 10 mg/kg bw/day (lowest dose) and in the female given 30 mg/kg bw/day. Liver altered foci were observed in the female given 10 mg/kg bw/day (LOAEL), and the NOAEL value for the female was 3 mg/kg bw/day. Lowest values for all the hepatic lesion was 10 mg/kg bw/day for the female on both the 26-week and 104-week studies. A clear sex-related difference was observed in the plasma levels of mosapride in rats, in which the higher levels were observed in the female. The result, together with the data on the 26-week study, suggests that the NOAEL value in the male rats is unlikely to be lower than 3 mg/kg bw/day. FSCJ judged it appropriate to adopt this value as the NOAEL for the ADI of mosapride citrate, based on the following reasons: 1) The clear sex-related difference was observed in the plasma levels of mosapride in rats, in which the higher levels were observed in the female; and 2) The common ratio of the dose was smaller in the 104-week carcinogenicity study than that in the 26-week subacute toxicity study. Consequently, FSCJ established an ADI of 0.03 mg/kg bw/day, applying a safety factor of 100 (10 for species difference, 10 for individual difference) to the NOAEL obtained in the 104-week carcinogenicity study in rats.

Ochratoxin A

The Food Safety Commission of Japan (FSCJ) conducted a risk assessment on ochratoxin A (hereinafter referred to as OTA) as a self-tasking risk assessment. OTA is a mycotoxin produced by fungal species such as Aspergillus ochraceus and Penicilium verrucosum, which occur mainly in stored foods. Food contamination with OTA has been reported in various food commodities including cereal, coffee, cocoa, beer and wine. Nephrotoxicity was observed in all the animal species examined in the subacute toxicity studies. Pathological changes observed in the studies are karyomegaly and cytomegaly as well as tubular atrophy and degeneration in proximal tubules at the outer zone of renal medulla. The dose- and treatment period-dependent changes were observed in kidneys in rats and pigs. In chronic toxicity/carcinogenicity studies with oral administration, tumor induction was observed at the outer zone of renal medulla in rodents, mainly in male rats. Chromosome aberration was observed both in in vitro and in vivo genotoxicity studies, but gene point mutation was not detected. After reviewing the results of various toxicological studies, FSCJ considered that OTA is a non-genotoxic carcinogen acting indirectly on DNA, and that tolerable daily intake (TDI) is able to be specified for OTA. Regarding non-carcinogenic toxicity of OTA, the effects observed at the lowest dose in various studies were decreased ability to concentrate urine and degenerative changes in epithelial cells of the tubules observed in a 120-day subacute toxicity study in pigs. The lowest-observed-adverse-effect level (LOAEL) in these studies was set at 8 µg/kg bw/day. FSCJ specified the TDI of 16 ng/kg bw/day, applying an uncertainty factor of 500 (10 for species difference, 10 for individual difference and 5 for the use of LOAEL based on irreversible renal failure indices) to the LOAEL. Regarding carcinogenicity of OTA, FSCJ specified the TDI of 15 ng/kg bw/day, applying an uncertainty factor of 1000 (10 for species difference, 10 for individual difference and 10 for carcinogenicity) to the no-observed-adverse-effect level (NOAEL) of 15 µg/kg bw/day, which was derived from a two-year carcinogenicity study in rats (administered 5 times a week at 21 µg/kg bw) performed by the National Toxicology Program (NTP). The estimated exposure levels of OTA in Japan for average (the 50th percentile) and high risk consumers (the 95th percentile) are 0.14 ng/kg bw/day and 2.21 ng/kg bw/day, respectively. These estimations suggest the intake of OTA to be below the TDI even in the high risk consumers. Therefore, FSCJ considers that no apparent adverse effect is expected in Japan from the current risk estimate. OTA-producing fungi grow in agricultural products and food under different environmental conditions. OTA contamination in these products varies depending on environmental conditions such as climate. Therefore, the risk management organizations are encouraged to monitor OTA contamination in foods continuously. The monitoring is a key importance to consider the necessity of the regulation for OTA.