Registration Dossier

Toxicological information

Carcinogenicity

Currently viewing:

Administrative data

Description of key information

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
no
Remarks:
Conducted according to the guideline in effect at the time of study conduct.
Qualifier:
according to
Guideline:
EPA OPPTS 870.4300 (Combined Chronic Toxicity / Carcinogenicity)
Deviations:
no
Remarks:
Conducted according to the guideline in effect at the time of study conduct.
Qualifier:
according to
Guideline:
EU Method B.33 (Combined Chronic Toxicity / Carcinogenicity Test)
Deviations:
no
Remarks:
Conducted according to the guideline in effect at the time of study conduct.
Qualifier:
according to
Guideline:
other: JMAFF Japan Agricultural Chemicals Regulation Law 12 Nousan No. 8147
Deviations:
no
Remarks:
Conducted according to the guideline in effect at the time of study conduct.
GLP compliance:
yes
Species:
rat
Strain:
other: Crl:CD(SD)
Sex:
male/female
Route of administration:
oral: gavage
Vehicle:
other: deionized water
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
up to 104 weeks in males and up to 101 weeks in females
Frequency of treatment:
Daily
Remarks:
Doses / Concentrations:
0.1, 1, and 50 mg/kg/day for males
Basis:
actual ingested
Remarks:
Doses / Concentrations:
1, 50, and 500 mg/kg/day for females
Basis:
actual ingested
No. of animals per sex per dose:
80
Control animals:
yes, concurrent vehicle
Relevance of carcinogenic effects / potential:
Test article-related increases in hepatocellular adenoma and hepatocellular carcinoma were observed in females at 500 mg/kg/day. Equivocal increases in pancreatic acinar cell tumours and testicular interstitial (Leydig) cell tumours occurred in males administered 50 mg/kg/day. Clear thresholds were established for all of these tumour types, as test article-related tumor responses occurred only at the highest doses tested in males and females. Most research indicates that induction of these specific tumours in rats by non-genotoxic peroxisome proliferators likely has little or no relevance in humans, especially in plausible human exposure scenarios.
Dose descriptor:
NOAEL
Effect level:
1 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: see 'Remark'
Remarks on result:
other: Effect type: toxicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
50 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: see 'Remark'
Remarks on result:
other:
Remarks:
Effect type: other: toxicity and carcinogenicity (migrated information)

For additional information on results refer to 7.5.1 Repeated dose toxicity: oral: DI.K1.24Mon.Gav.RD/CARC.R.D18405-1238.KD.

Conclusions:
Clear thresholds were established for all of these tumour types, as test article-related tumor responses occurred only at the highest doses tested in males and females. Most research indicates that induction of these specific tumours in rats by non-genotoxic peroxisome proliferators likely has little or no relevance in humans, especially in plausible human exposure scenarios.
Executive summary:

This study was conducted to evaluate the potential chronic toxicity and oncogenicity of the test article when administered via oral gavage over the major portion of the life span of the test animals. Four treatment groups of 80 male and 80 female rats were administered the test article at respective dose levels of 0.1 (males only), 1, 50, and 500 (female only) mg/kg/day. One additional group of 80 animals/sex served as the control and received the vehicle, deionized water. The vehicle or test article was administered to all groups via oral gavage, once a day for up to 104 weeks, at a dose volume of 10 mL/kg/dose. Due to poor overall survival in females, all female dose groups were sacrificed at Week 101. In this report, this terminal interval will be referred to as 24 month.

Observations for morbidity, mortality, injury, and the availability of food and water were conducted twice daily (three times daily beginning in Week 53) for all animals. Observations for clinical signs and masses were conducted weekly. Body weight and body weight change were measured and recorded weekly for the first 14 weeks and then every other week thereafter. Food consumption was measured and recorded pretest (Week -1), weekly during the first 13 weeks, and for 2 week intervals starting on Week 14, and food efficiency was calculated. Ophthalmoscopic examinations were conducted all animals pretest and on all surviving animals prior to the interim and terminal necropsies. Blood and urine samples for clinical pathology evaluations were collected from designated animals at 3 (no coagulation or urine), 6, and 12 months. Peripheral blood smears were collected from designated animals at 12 and 18 months and prior to termination. At study termination (12 and 24 months), necropsy examinations were performed, organ weights were recorded, and tissues were microscopically examined.

There were no test article-related effects on survival. There were no adverse clinical or ophthalmological observations attributed to test article exposure. No adverse, test article-related effects on body weight or nutritional parameters were observed in males at any dose. Mean food consumption and food efficiency values were generally comparable to control throughout the study. Exposure to 500 mg/kg/day (females) produced adverse reductions in body weight, body weight gain, and food efficiency. Mean body weight in this group was 13% below control at Week 52 (statistically significant), but was generally comparable to the control value at termination. Mean body weight gain in this group was 20% below controls over Weeks 1 to 52 but only slightly lower than the control value (not statistically significant) over the two year period. There was no test article-related effect on food consumption. The reduced body weight gain was associated with lower mean food efficiency over the first year although overall (2-year) food efficiency was comparable to controls. The body weight, body weight gain, and food efficiency differences were considered adverse at this dose based on the magnitude of difference during the first year of exposure. No adverse effects on body weight or nutritional parameters were observed in any other dose group.

There were no test article-related effects on survival over the course of this study. The only test article-related cause of death/morbidity was inflammation/necrosis of the kidneys in 500 mg/kg/day females. This cause of death/morbidity was assigned to animals whose early death was considered to be the result of renal papillary necrosis observed microscopically. There was no test-article related increase in masses or mass findings.

At the 3, 6, and 12 month intervals, there were mild decreases in red cell mass (erythrocytes, haemoglobin, and hematocrit) in females receiving 500 mg/kg/day (up to 28% below control). These changes were associated with an appropriate increase in reticulocytes (up to 106% above control). There were no effects on erythrocyte morphology. This collection of findings is suggestive of red cell loss or increased red cell turnover (haemolysis) although the exact mechanisms involved are unknown. All of these findings were considered test article related and adverse. Statistically significant decreases in red cell mass were also present in males receiving 50 mg/kg/day at the 3- and 6-month interval. However, the decreases were small, did not induce statistically significant changes in reticulocytes, and were transient (no statistically significant differences at 12 months), and values in individual animals in the 50 mg/kg/day group were similar to controls. Therefore, the red cell mass changes in 50 mg/kg/day males were considered to be test article-related but nonadverse. No other effects on haematological parameters were attributed to test article exposure in either sex at any dose or interval. There were no test article-related effects among coagulation times in either sex at any dose level. No test article-related effects among leukocytes were observed in either sex.

Increases in enzymes indicative of liver injury were observed at 12 months in males at 50 mg/kg/day, including mild increases in alanine aminotransferase (ALT) and sorbitol dehydrogenase, and were correlated with microscopic findings of minimal cystic degeneration and minimal to mild focal necrosis in the liver of males at 50 mg/kg/day. Therefore, these enzymes changes were considered test article-related and adverse. There were also mild increases in alkaline phosphatase at the 3 and 6 month intervals in males at this dose level; these increases were less than those present at 12 months and were not associated with statistically significant changes in other enzymes indicative of hepatic or hepatobiliary injury at these time points. Therefore, the changes in alkaline phosphatase at the 3 and 6 month intervals may be due in part or in whole to test article-related enzyme induction, as the test article was previously shown to produce an increase in total P450 enzyme activity in male rats at 30 mg/kg/day. There were no test article-related changes in liver enzymes in males receiving 1 or 0.1 mg/kg/day or in females at any of the dose levels tested (up to 500 mg/kg/day). Increases in albumin were present in 50 mg/kg/day males at all intervals and in 500 mg/kg/day females at the 3-month interval. Decreases in globulin were present in 500 mg/kg/day females at all intervals (with an associated decrease in total protein at the 6-month interval). No statistically significant decreases in group means for globulin were present in males at any dose or interval; however, small decreases in individual values for these parameters in individual animals in the 50 mg/kg/day male group may have been test article-related. The changes in albumin and globulin in the high-dose male and female groups also resulted in statistically significant increases in albumin/globulin ratio in these groups at all intervals. These changes in serum proteins in high dose males and females were considered test article-related but were not considered biologically relevant based on their small magnitude and lack of association with known adverse outcomes. Statistically significant increases in urine volume and decreases in urine specific gravity were observed at 6- and 12-months in 500 mg/kg/day females, suggestive of a minimal diuresis. Although minimal and not associated with changes in kidney-related chemistry parameters, these differences may be correlative to increased incidences and severity of chronic progressive nephropathy observed in this dose group at the 1-year interim sacrifice.

At the interim necropsy, test article-related effects included irregular surface of the kidney (500 mg/kg/day females) and increased liver weights (50 mg/kg/day males and 500 mg/kg/day females). Microscopic pathology findings in the interim sacrifice groups included minimal focal cystic degeneration and minimal to mild focal necrosis of the liver (50 mg/kg/day males), centrilobular hypertrophy of the liver (500 mg/kg/day females), and increased incidence and severity of chronic progressive nephropathy in the kidney (500 mg/kg/day females).

At termination (2-year), test article-related increases in liver weight and macroscopic observations in the kidneys (irregular surface) and liver (tan focus/foci and mass/nodule) were observed in 500 mg/kg/day females. These macroscopic observations were correlative to test article-related microscopic findings described below.

At termination, test article-related non-neoplastic microscopic changes were observed at the highest doses tested in each sex: in the liver of 50 mg/kg/day males and in the liver, kidneys, nonglandular stomach (limiting ridge), and tongue of 500 mg/kg/day females. In the liver of males at 50 mg/kg/day, there were statistically significantly increased incidences of focal cystic degeneration, centrilobular hepatocellular hypertrophy, and centrilobular hepatocellular necrosis. Test article-related findings in the liver of 500 mg/kg/day females were similar to those noted in 50 mg/kg/day males, and also included low incidences of panlobular hepatocellular hypertrophy and individual cell hepatocellular necrosis. Microscopic findings in the kidneys of 500 mg/kg/day females included tubular dilatation, oedema of the renal papilla, transitional cell hyperplasia in the renal pelvis, tubular mineralization, renal papillary necrosis, and chronic progressive nephropathy (CPN). In some 500 mg/kg/day females, the constellation of lesions diagnosed as CPN may be more representative of retrograde nephropathy, rather than typical CPN. Statistically significantly increased incidences of hyperplasia of squamous epithelium were observed in the nonglandular stomach (limiting ridge only) and the tongue in females at 500 mg/kg/day. In the tongue, subacute/chronic inflammation occurred in association with squamous epithelial cell hyperplasia. Test article-related neoplastic changes occurred in the liver of females administered 500 mg/kg/day, and consisted of an increased incidence of hepatocellular adenoma and hepatocellular carcinoma. The increased incidences of hepatocellular tumours occurred in association with degenerative/necrotic changes in the liver at this dose level (see above under discussion of non-neoplastic lesions). No hepatocellular tumours and no test article-related degenerative or necrotic changes were observed in lower dose females and the incidence of hepatocellular tumours in males was comparable between the controls and the 50 mg/kg/day group. Equivocal increases in pancreatic acinar cell tumours and testicular interstitial (Leydig) cell tumours occurred in males administered 50 mg/kg/day. In males at 50 mg/kg/day, a statistically significant increase was observed in the incidence of pancreatic acinar cell adenoma/carcinoma combined, but not adenoma or carcinoma alone. In addition, the incidences of acinar cell hyperplasia were not significantly different from controls in any of the treated male groups. However, based on the known PPARα agonist activity of the test article, the marginal increase in pancreatic acinar cell tumours in the 50 mg/kg/day male group provides equivocal evidence of a test article-related effect. The incidence of interstitial cell adenoma of the testes was increased in males at 50 mg/kg/day, and one interstitial cell adenoma was also present in one male in the 50 mg/kg/day group at the interim necropsy. The incidence of interstitial cell hyperplasia at 50 mg/kg/day was also higher than in control males. Since PPARα agonists are known to produce proliferative interstitial cell lesions (hyperplasia and adenoma) in the testes of rats, a relationship to treatment for these findings in the 50 mg/kg/day male group cannot be ruled out. However, based on the marginal nature of the increased incidences of these lesions, their lack of statistical significance, and the relatively high incidence of these lesions in concurrent controls, the relationship to treatment for these findings is equivocal. The incidences of proliferative interstitial cell lesions of the testes in the 0.1 and 1 mg/kg/day groups, were similar to or less than controls. No adverse pathology findings occurred in male rats administered 0.1 or 1 mg/kg/day or in females administered 1 or 50 mg/kg/day.

Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for chronic toxicity of the test substance was 1 mg/kg/day in male rats and 50 mg/kg/day in females. The NOAEL in males is based on increases in focal cystic degeneration, focal necrosis, and centrilobular necrosis of the liver, with associated increases in cytotoxic liver enzymes, and equivocal increases in pancreatic acinar cell tumours and testicular interstitial (Leydig) cell tumours, all observed at 50 mg/kg/day. In females the NOAEL is based on reductions in body weight, body weight gain, and food efficiency; mild decreases in red cell mass; increases in individual cell necrosis in the liver, hyperplasia and/or inflammation in the nonglandular stomach and tongue; an increase in incidence and severity of microscopic pathology in the kidneys; and an increase in hepatocellular adenomas and carcinomas, all observed at 500 mg/kg/day.

Test article-related increases in hepatocellular adenoma and hepatocellular carcinoma were observed in females at 500 mg/kg/day. Equivocal increases in pancreatic acinar cell tumours and testicular interstitial (Leydig) cell tumours occurred in males administered 50 mg/kg/day. Clear thresholds were established for all of these tumour types, as test article-related tumour responses occurred only at the highest doses tested in males and females. Most research indicates that induction of these specific tumours in rats by non-genotoxic peroxisome proliferators likely has little or no relevance in humans, especially in plausible human exposure scenarios.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Study duration:
chronic
Species:
rat
Quality of whole database:
OECD Guideline, GLP study

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

In a chronic toxicity/carcinogenicity study in rats, test substance-related neoplastic changes were limited to the high dose groups (50 and 500 mg/kg/day in males and females) and were consistent with the known effects of peroxisome proliferator alpha (PPARα) in rodents. Neoplastic effects included hepatocellular tumours in 500 mg/kg/day females and, equivocally, pancreatic acinar cell tumours and testicular interstitial cell tumours in 50 mg/kg/day males. All tumours occurred with a clear threshold in both males and females. In females, liver tumours in the 500 mg/kg/day dose group occurred in association with marked systemic toxicity, as well as liver toxicity, and no hepatocellular tumours were observed in females at lower doses where no liver toxicity was observed. In males, the only pancreatic acinar cell tumour that occurred in the lower dose groups (0.1 and 1 mg/kg/day) was an acinar cell adenoma in the 0.1 mg/kg/day group (not dose-related and well within the historical control range of 0-5.0%), and the incidences of interstitial cell tumours and hyperplasia in males at lower doses were less than or equal to those of controls.

Comparative Biology Of PPARα Agonists

The test substance belongs to a class of compounds known as PPARα agonists (Haas, 2008) which are known to produce liver, pancreatic, and testicular tumours in rats, and liver tumours in mice (Biegel et al., 1992; Klaunig et al., 2003). However, these compounds have not been shown to be carcinogenic in other species, including humans (Klaunig et al., 2003; Cunningham et al., 2010). Based on extensive research into the comparative biology of peroxisome proliferator-induced hepatic carcinogenesis, the induction of liver tumours in rodents by non-genotoxic peroxisome proliferators is not considered relevant to humans (Cunningham et al., 2010; Peters et al., 2005; Klaunig et al., 2012). In addition, while less definitive mechanistic data are available on the role PPARα in the induction of pancreatic acinar cell tumours in rats, the available data on a proposed mode of action—involving altered bile flow and increased cholecystokinin (CCK)—suggest that this mode of action is also likely not relevant to humans (Klaunig et al., 2012). Mechanistic data on the mode of action for induction of testicular interstitial cell tumours in rats by peroxisome proliferators is less robust. However, extensive research into the comparative biology and mechanisms of action of interstitial cell tumour induction in rodents by a wide class of non-genotoxic compounds indicate that these tumours most likely have low relevance to humans under most exposure condition (Prentice et al., 1995; Cook et al., 1999).

Conclusions

The induction of liver tumours in female rats at 500 mg/kg/day, and the equivocal increase in pancreatic acinar and testicular interstitial cell tumours in male rats at 50 mg/kg/day are likely not relevant to humans based on the following: most research indicates that induction of these specific tumours in rats by non-genotoxic peroxisome proliferators likely has little or no relevance to humans, especially in plausible human exposure scenarios; the test material was determined to be non-genotoxic based on a battery of in vivo and in vitro genotoxicity studies; liver tumours were produced only in females and only at doses associated with marked hepatic and systemic toxicity (including lethality); and thresholds were established for all tumour types in both males and females.

References

Ashby J and Lefevre PA (2000). The peripubertal male rat assay as an alternative to the Hershberger castrated male rat assay for the detection of anti-androgens, oestrogens and metabolic modulators. Journal of Applied Toxicology, 20:35-47.

Carney EW, Zablotny TL, Marty MS, Crissman JW, Anderson P, Woolhiser M, and Holsapple M (2004). The effects of feed restriction during in utero and postnatal development in rats. Toxicological Sciences, 82:237-249.

Cunningham ML, Collins BJ, Hejtmancik MR, Herbert RA, Travlos GS, Vallant MK, and Stout MD (2010). Effects of the PPARα agonist and widely used antihyperlipidemic drug gemfibrozil on hepatic toxicity and lipid metabolism. PPAR Research, Volume 2010, Article ID 681963.

DuPont (2009). DuPont-17751-1026. A 90-day oral (gavage) toxicity study of H-28548 in rats with a 28-day recovery. Unpublished data.

DuPont (2010). DuPont-18405-1307. H-28548: Subchronic Toxicity 90-Day Gavage Study in Mice. Unpublished data.

DuPont (2010). DuPont-18405-1037. An Oral (Gavage) Reproduction/DevelopmentalToxicity Screening Study of H-28548 in Mice. Unpublished data.

Holson JF, Nemec MD, Stump DG, Kaufman LE, Lindstrom P, and Varsho BJ (2006). Significance, Reliability, and Interpretation of Developmental and Reproductive Toxicity Study Findings. In: Developmental and Reproductive Toxicology - A Practical Approach;Hood RD, Ed. CRC Press: Boca Raton, FL, p. 381.

Mitchell BF and Taggart MJ (2009). Are animal models relevant to key aspects of human parturition? Am J Physiol Regul Integr Comp Physiol, 297:R525–R545.

Wickramaratne GA (1998). The post-natal fate of supernumerary ribs in rat teratogenicity studies. Journal of Applied Toxicology, 3(2):91-94.

Justification for classification or non-classification

The induction of liver tumours in female rats at 500 mg/kg/day, and the equivocal increase in pancreatic acinar and testicular interstitial cell tumours in male rats at 50 mg/kg/day are likely not relevant to humans based on the following: most research indicates that induction of these specific tumours in rats by non-genotoxic peroxisome proliferators likely has little or no relevance to humans, especially in plausible human exposure scenarios; the test material was determined to be non-genotoxic based on a battery of in vivo and in vitro genotoxicity studies; liver tumours were produced only in females and only at doses associated with marked hepatic and systemic toxicity (including lethality); and thresholds were established for all tumour types in both males and females. Based on the above information, the substance is not classified for carcinogenicity according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) regulation (EC) no. 1272/2008.