2-Pyridinesulfonamide, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(2,2,2-trifluoroethoxy)-, sodium salt (1:1)

Endpoint summary

Description of key information

ORAL
The NOAEL was determined to be 83 mg/kg bw/day (male) according to a 4 week rat study performed in line with OECD Guideline 407 and EU Method B.7 – Gerspach 2001
The NOEL was determined to be 65.7 mg/kg bw/day (male) according to a 90 day rat study performed in line with EPA Guideline 82-1 and OECD 408 – Gerspach 1998a
The NOEL was determined to be 67.9 mg/kg bw/day (male) according to a 90 day mice study performed in line with EPA Guideline 82-1 and OECD 408 – Gerspach 1998b
The NOEL was determined to be 19.6 mg/kg bw/day (female) according to a 90 day dog study performed in line with EPA Guideline 82-1 and OECD 409 – Altmann 2000
The NOEL was determined to be 14.9 mg/kg bw/day (female) according to a 12 month study with dogs performed in line with OECD 409 and EPA OPP 82-1 - Altmann 2000b
The NOEL was determined to be 112 mg/kg bw/day (female) according to an 18 month study with mice performed in line with OECD 451 and EPA OPP 83-2 - Gerspach 2000a
The NOEL was determined to be 23.7 mg/kg bw/day (female) according to a 24 month study with rats performed in line with OECD 453 and EPA OPP 83-5 - Gerspach 2000b
DERMAL
The NOAEL was determined to be 100 mg/kg bw/day (female rats) according to a study performed in line with EPA Guideline 82-2, OECD 410 and EU Method B.9 -  Gerspach 1998

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

23.7 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Three subacute, three subchronic and three chronic studies are available for assessing the repeated dose (oral) toxicity of the test material. All studies were performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The studies were all assigned a reliability score of 1 in accordance with the criteria for assessing data quality as outlined in Klimisch (1997) and were considered suitable for assessment as an accurate reflection of the test material. The overall quality of the database is therefore high.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The study was performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality as outlined in Klimisch (1997) and was considered suitable for assessment as an accurate reflection of the test material. The overall quality of the database is therefore high.

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

subacute

Species:

rat

Quality of whole database:

The study was performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality as outlined in Klimisch (1997) and was considered suitable for assessment as an accurate reflection of the test material. The overall quality of the database is therefore high.

Additional information

Sub-acute oral toxicity

Three 28-day studies, two in dogs and one in rats, are available. A NOEL of 1000 ppm in food (equivalent to 83 mg/kg bodyweight in male rats and 88 mg/kg bodyweight in female rats) was determined in the rat study. Neither of the two dog studies determined a value for a NOEL. Findings indicate that the liver and hemotopoietic system appear to be primary target organs following exposure at higher dose levels.

More specifically, in the rat study in which animals were dosed with test material in diet for a period of 28 days, treatment was tolerated without occurrence of overt toxicity. Reduced bodyweight gains were measured in both sexes treated at 20000 ppm. At 20000 ppm, the laboratory examinations revealed decreased heamoglobin concentrations and a mild eosinopenia. At dose levels above 4000 ppm lower blood clotting activities were detected. Changes to some blood chemistry parameters indicated an effect on the liver. At necropsy, liver weights were increased in groups dosed at or above 4000 ppm in males and at 20000 ppm in females. Histopathology of the livers showed hepatocellular hypertrophy in both sexes at dose levels of 4000 ppm and above, and slight cytoplasmic vacuolation and necrosis in males treated at 20000 ppm. In addition, thymus weights were decreased at 12000 ppm (males) and at 20000 ppm (both sexes). It can be inferred from the observations made during the study, that the no observed effect level for the test material, when offered to rats continuously in their food over a period of four weeks, was 1000 ppm, corresponding to a mean daily intake of 83 mg/kg bw in males and 88 mg/kg bw in females.

In the first of the two dog studies, dogs were dosed test material in capsules. Under the conditions of the study none of the animals died and in-life observations, bodyweight development and food consumption were not affected by treatment and no treatment-related changes were observed during eye examinations and urine analysis. Towards the end of the treatment period white deposits were observed in faeces of high dose animals, which were subsequently identified as test material. Definitive effects of the test material were on heamotopoiesis at the high dose level and at the mid- and high dose level a hepatotrophic effect was evidenced by anemia and a slight thrombopenia and by increased liver weight. In addition, changes in globulin, albumin and electrolyte concentrations were observed at the high dose level. Microscopic examination revealed lymphoid follicular hyperplasia in the spleen of mid and high dose level animals and females of the low-dose level. Furthermore, single animals of the high dose group displayed reduced spermatogenesis and single cell necrosis in the testes, cortical atrophy in the thymus, hypertrophy of thyroid follicular cells and chronic destructive inflammation of the thyroid gland. Based on these data it was concluded that the heamatopoietic system and the liver were target organs of toxicity. Furthermore, histopathological changes point to spleen, testes, thymus and thyroid gland as further organs that might be affected by the test material. It is, however, unclear whether these effects are direct effects induced by the test material or whether they are incidental findings.

In the second of the two dog studies, dogs were dosed test material in diet at dose levels of 15000 ppm and 30000 ppm. It was hoped that this would help determine the level of test material to which the dogs were actually exposed. Under the conditions of the study animals of the high dose group were showing severe signs of toxicity and were sacrificed on test day 12. No other animal died or had to be sacrificed. Beginning on test day 9 to 10 high dose animals were found recumbent and had weakness of hind legs. Some of these animals additionally had hunched posture, reduced activity or were vomiting. From day 11 on similar signs were observed in the 15000 ppm dose group. These signs disappeared on test day 16 despite continuous exposure. Neurological examination conducted on test day 12 revealed reduced activity and impaired neuromotor functions in one animal of each dose group but did not provide any evidence for an involvement of peripheral nerves. All animals of the high dose group and one female of the low dose group lost bodyweight and had reduced food intake. Reduced food consumption developed gradually indicating absence of palatability problems. The hematopoietic system and the liver were confirmed as target organs of toxicity as evidenced by the normochromic anemia and thrombopenia seen at both dose levels and by increased liver weight. Furthermore, histopathological changes point to the testes, kidneys, thymus, spleen, lungs and lymph nodes as further organs that might be affected by the test material. Neuropathological examination did not reveal any lesion indicating a specific neuropathic effect of the test material.

 

Sub-chronic oral toxicity

In a 90 day feeding study in rats at dose levels up to 16000 ppm in food, a NOEL of 65.7 mg/kg bodyweight in males and 75.6 mg/kg bodyweight in females was found. Under the conditions of the study, treatment with test material resulted in decreased bodyweight gains of males and females treated at the highest concentration. The liver was confirmed as a target organ by changed laboratory parameters, increased absolute/relative liver weights, increased incidence and severity of hepatocellular hypertrophy, and increased single cell necrosis or necrosis. After a four week recovery period, most of these effects were reversible. Additionally, a slight increased incidence of small testes and an increase in the severity of tubular atrophy, especially in the recovery group, was found which may be related to treatment. Based on the bodyweight data and the occurrence of necrosis and of single cell necrosis in the liver of females, the Maximum Tolerated Dose level was met or slightly exceeded at 16000 ppm. The NOEL was at 1000 ppm and corresponded to 65.7 mg/kg bw in males and to 75.6 mg/kg bw in females. The NOAEL was defined at 8000 ppm and corresponded to 507 mg/kg bw in males and 549 mg/kg bw in females.

In a 90 day feeding study in mice at dose levels up to 7000 ppm in food, a NOEL of 67.9 mg/kg bodyweight was determined in males and a NOEL of 102 mg/kg bodyweight in females. Under the conditions of the study, treatment with the test material resulted in slightly decreased food intake during the first treatment week in all dosed groups. Later on, no effects on in-life endpoints were detected. Lower plasma bilirubin values occurred in animals dosed at 1750 ppm and above. At necropsy, males of the high dose group had slightly higher liver weights. Histopathological evaluation did not reveal treatment related findings. The NOEL was estimated at 500 ppm which is equivalent to 67.9 mg/kg bw for males and 102 mg/kg bw for females.

In a 90 day feeding study in dogs at dose levels up to 20000 ppm, a NOEL of 500 ppm (19.8 mg/kg bodyweight) was determined in males and a NOEL of 500 ppm (19.6 mg/kg bodyweight) was determined in females. Under the conditions of the study, treatment with the test material resulted in slightly decreased food intake during the first treatment week in all dosed groups. Later on, no effects on in-life endpoints were detected. Lower plasma bilirubin values occurred in animals dosed at 1750 ppm and above. At necropsy, males of the high dose group had slightly higher liver weights. Histopathological evaluation did not reveal treatment related findings.

 

Chronic oral toxicity

In a 12 month study test material was administered to beagle dogs in the diet at nominal dietary levels of 0, 50, 200, 500, 1500 and 4000 ppm. Overall, treatment with the test material was well tolerated. Bodyweight gain was decreased in males of groups dosed at 1500 and 4000 ppm. In addition, in these groups, increase in liver weight and alterations on blood chemistry parameters indicated a hepatotropic effect. In the absence of any treatment-related histopathological findings, these changes in the liver were considered not to be adverse. At 4000 ppm the test material mildly affected haematological parameters. Based on bodyweight and liver effects, the No Observed Effect Level was determined to be 500 ppm corresponding to a daily test material intake of 15.0 and 14.9 mg/kg bw/day for males and females, respectively. The No Observed Adverse Effect Level was determined to be 500 ppm for males, corresponding to 15.0 mg/kg bw/day, and 4000 ppm for females, corresponding to 121 mg/kg bw/day.

In an 18 month carcinogenicity study, test material was administered to mice, at dietary concentrations up to 7000 ppm. Overall, treatment with test material was well tolerated, and the survival rate was comparable to that of the respective control group. Treatment-related effects were restricted to reduced food consumption of females leading to slightly decreased body weight gain in high dose females. High dose males consumed more water through the first 3 months of treatment compared to the control animals and at the end of the treatment period only, slightly lower values for the erythrocyte parameters were measured. There were no macroscopic or microscopic findings related to the treatment. There was no evidence of treatment-related carcinogenicity during the study. Based on the findings, the NOEL after 18 months of treatment was 1000 ppm, equivalent to an average daily intake of 121 or 112 mg/kg bodyweight for males and females, respectively.

 

In a further study, test material was administered to rats at dietary concentrations up to 10000 ppm, for 24 months. Overall, treatment with test material was well tolerated without occurrence of overt toxicity. There was no adverse effect of treatment on the mortality rate and the animal's behaviour was normal. A significant decrease in body weight gain occurred in high dose group animals of both sexes indicating that the maximum tolerated dose had been met or exceeded at 10000 ppm. Treatment-related toxicity was mainly noted at this dose group and effects most often related to the decreased weight gain. These included marginal effects on hematology parameters and several increased organ weight to body weight ratios without laboratory or pathology correlates. Histopathologic evaluation showed a non-dose responsive increase in the incidence of kidney tubular atrophy in females dosed at 2000 and 10000 ppm. This common finding, greater than 25% in controls, was seen at greater than 60% at the two top doses, but with a severity grade of only minimal to slight. There were no data from other measured parameters to support the kidney as the target organ. In males, there was an increase in the incidence of Leydig cell hyperplasia at the high dose only. The grades were mostly minimal to slight with no differences in severity among the groups. At the same dose level, the mean testes to body weight ratios were increased. There were no treatment-related increases in neoplastic lesions in this study. Under the conditions of the study, a non-dose responsive increase in tubular atrophy was also noted in 2000 ppm females. Based on this kidney effect, the overall no observable effect level for females was 500 ppm, and corresponded to 23.7 mg/kg body weight/day. The no observable effect level for males was at 2000 ppm and corresponded to 82.6 mg/kg body weight. There was no evidence during the study for a carcinogenic effect in rats. 

 

Sub-acute dermal toxicity

In a 28 day dermal study in rats at dose levels up to 1000 mg/kg bw/day, dermal treatment with the test material was found to be well tolerated. Except for decreased bodyweight gain in females (-29% compared to the control group mean), at the high dose level, no treatment-related effects occurred. There was no irritating effect on the skin. The NOEL and NOAEL were at 1000 mg/kg bodyweight in males, and at 100 mg/kg bodyweight in females.

 

All studies were performed to GLP and followed standardised guidelines with a high standard of reporting. The studies were assigned a reliability score of 1 in accordance with the criteria for assessing data quality as outlined in Klimisch (1997) and considered suitable for assessment as an accurate reflection of the test material.

The available data is considered to be complete and the results determined, 2 year rat study NOAEL of 23.7 mg/kg bw/day, and 28 day dermal NOAEL of 100 mg/kg bw/day, were taken forward for risk assessment.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Eight repeated dose toxicity (oral) studies were considered in weight of evidence assessment. The 24 month rat study was selected as a basis for the effect level since it assesses test material toxicity over the largest time frame and was conducted in a standard test species. In comparison with findings in the other subacute, subchronic and chronic toxicity studies in rodents and dogs, the effect level selected is deemed to be highly conservative since effect levels in other studies were three to four times higher in most cases and the slightly lower NOAEL obtained in the 1 year dog study is considered due to the dosing spacing used in this study.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
Only one study is available.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
Only one repeated dose subacute dermal toxicity study was available. The study included observations of skin reactions.

Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I Point 3.9, Regulation 1272/2008, the test material does not require classification for repeated dose specific organ toxicity since the effects observed do not indicate any signs of organ dysfunction.

In accordance with criteria for classification as defined by Directive 2001/59/EC, Annex VI, Point 3.2.3, the test material does not require classification for repeated dose toxicity.