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

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 April 1997 to 19 August 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was performed to GLP and in line with standardised guidelines OECD 414 and EPA OPP 83-3 with no deviations thought to impact on the reliability of the presented results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPP 83-3 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EU Method B.31 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: JMAFF 59 NohSan No. 4200

Deviations:

no

Test guideline 5

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4900 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

sodium 4,6-dimethoxy-N-({[3-(2,2,2-trifluoroethoxy)pyridin-2-yl]sulfonyl}carbamoyl)pyrimidin-2-aminide

EC Number:

688-332-8

Cas Number:

199119-58-9

Molecular formula:

C14H13F3N5O6SNa

IUPAC Name:

sodium 4,6-dimethoxy-N-({[3-(2,2,2-trifluoroethoxy)pyridin-2-yl]sulfonyl}carbamoyl)pyrimidin-2-aminide

Test material form:

solid: particulate/powder

Details on test material:

- Physical state: solid (powder)
- Storage condition of test material: room temperature

Test animals

Species:

rat

Strain:

other: Tif:RAI f

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at mating: minimum 8 weeks
- Housing: individually
- Diet: pelleted, certified standard feed ad libitum
- Water: tap water ad libitum
- Acclimation period: at least 7 days, between delivery and the first treatment on day 6 post coitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 50 ± 20 %
- Air changes (per hr): about 16 air changes/hour
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light

IN-LIFE DATES: From 18 April 1997 to 19 August 1997

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: 0.5% (w/w) sodium carboxymethylcellulose

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Test material - vehicle mixtures were prepared daily with a high speed homogeniser. Homogeneity of the mixtures during administration was obtained with a magnetic stirrer.

VEHICLE
- Concentration in vehicle: 0, 3.0, 30.0 and 100 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Duplicate samples of dosing solutions were taken once before and once after dosing on 30 April and 12 May 1997. The samples from before dosing were taken from the top, middle and bottom of the container; the samples after dosing were taken from the middle of the container. Test material concentrations were determined by HPLC.

Details on mating procedure:

- M/F ratio per cage: 1/3
- Length of cohabitation: overnight in mating cages
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

Animals received single daily doses from day 6 to day 15 post coitum

Frequency of treatment:

Daily from day 6 to day 15 post coitum

Duration of test:

Dams were sacrificed on day 21 post coitum

No. of animals per sex per dose:

24 females per dose group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected on the basis of results generated from a range finding study in which the test material was shown to elicit a slight effect on maternal parameters at 1000 mg/kg. No indication of teratogenesis was observed during the range finding study.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily (> 6 hours apart)
- Cage side observations checked included mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION : Yes (calculated as food consumption (g) per period/days per period)
- Time schedule: days 6, 11, 16 and 21

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: macroscopic pathological examination of the main organs of the thoracic and abdominal cavities, in particular the genitals.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Number of live and dead fetuses: Yes

Fetal examinations:

All foetuses were weighed and sexed before sacrifice. Necropsy examinations included:
- External examinations: Yes: all per litter. Special attention was paid to the body surface, head, trunk and extremities
- Soft tissue examinations: Yes: half per litter. Examination included morphology and position of the following organs and organ systems: skin, central nervous system, eyes, body cavities, respiratory system, digestive system, endocrine system, circulatory system, excretory system, genital system
- Skeletal examinations: Yes: half per litter. Investigation included: facial bones, cranial bones, sternum, shoulder girdle, forelimbs, pelvic girdle, hindlimbs, ribs and spinal column
- Head examinations: Yes: all per litter. Examination included: cranioschisis, encephalocele and cleft palate

Statistics:

Statistical analysis of continuous data was performed using the Analysis of Variance Procedure followed by Dunnett's t-Test in case of a significant result. Categorical data were analysed using Chi-Square test followed by Fischer's Exact test in case of a significant result. Non-parametric data were analysed using Kruskal-Wallis non parametric analysis of variance test followed by Dunn test.

Historical control data:

Historical control data was available for comparison of the findings.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
There were no premature mortalities during the study and no statistically significant differences in mean body weights across the groups.

Mean maternal body weight gains from day 16 to termination were approximately 10% and 7% less than that of the controls in the high and mid-dose groups, respectively although the difference were not statistically significant. Food consumption over the treatment period was reduced by approximately 11% and 6% in the high and mid-dose groups respectively, and the differences from control were deemed to be statistically significant.

Net weight change (carcass weight minus day 6 weight) was reduced by 21% in the high dose group and by 17% in the mid-dose group. Although not statistically significant, these differences correlate with the reduction in food consumption observed in both groups, and are therefore regarded as an indication of maternal toxicity.

In the low dose group, the slightly reduced net weight change was due to a higher than usual gravid uterus weight, and not considered treatment related.

Incidental clinical findings included chromodacryorrhea in one mid-dose animals, crust/scurf and/or wound in two mid-dose animals and hair loss in one high dose animal. Occasional vaginal bloody discharges were also observed in three low dose animals and in one high dose animal. These findings were not considered to be treatment related.

19, 22, 20 and 23 positively mated females were pregnant in the control, 30, 300 and 1000 mg/kg groups, respectively. All of them were sacrificed at termination on day 21 of pregnancy and were found to have viable fetuses. A non-dose response increase in the number of corpora lutea in the low and mid-dose groups resulted from the unusually low number observed in control animal ovaries compared to historical data, and therefore was not considered to be of any significance.

Preimplantation losses, the number of implantation sites, and early and late post implantation losses were regarded as similar in all groups. There were no dead or aborted foetuses. Maternal necropsy confirmed the clinical observations of skin lesions in two animals of the mid-dose group and hair loss in one animal of the high dose group. These findings were considered incidental. There were no other findings at gross necropsy.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: reduction in food consumption and net weight change

Details on embryotoxic / teratogenic effects:
Foetal weights were lower both in the high and mid-dose groups compared to controls but statistical significance was achieved in the high dose group only. Although the means were within the historical range, this body weight reduction was regarded as treatment-related and as an indication of delayed foetal development.

There were a number of visceral - thymus, liver and kidney findings, the incidences of which were similar in all dose groups. A collection of blood stained fluid was observed in the abdomen of two foetuses, one from each of the mid and high dose groups. This finding was considered to be incidental. A generalised oedema was observed in two foetuses from the low dose group. In the absence of any similar abnormalities in the mid and high dose groups, this was not attributed to treatment. No other findings were reported at foetal external examination. No skeletal malformations were found. Increased incidences of a few skeletal variations were observed in mid and high dose group foetuses, principally delayed ossifications of a few skeletal elements. The affected skeletal districts – sternum, thoracic vertebrae, metatarsus, fingers and toes became ossified late in the pregnancy and their incomplete ossification at day 21 was seen, together with the reduction in foetus weight, as an indication of developmental retardation in these two dose groups.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: fetotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Table 1: Mean Maternal Feed Consumption (g)

Time period	Treatment group (mg/kg)
	0	30	300	1000
Days 0-6	22.8	22.6	22.6	22.6
Days 6-11	24.5	23.9	22.8*	21.5**
Days 11-16	25.7	25.4	24.2*	23.3**
Days 16-21	25.9	25.1	24.6	24.7
Days 6-16	25.1	24.6	23.5*	22.4**

* p ≤ 0.05

** p ≤ 0.01

Table 2: Mean Uterine and Carcass Weights (g)

	Treatment group (mg/kg)
	0	30	300	1000
Gravid uterus	97.5	104.9	89.6	96.1
Carcass	263.5	257.1	255.7	255.7
Net weight change from day 6	37.0	32.2	30.8	29.4

 

Table 3: Mean Foetal Body Weights (g)

	Treatment group (mg/kg)
	0	30	300	1000
Foetal body weight (g)	5.6	5.4	5.3	5.3*

* p≤ 0.05

 

Table 4: Summary of all Foetal Skeletal Observations

	Treatment group (mg/kg)
	0	30	300	1000
Litters evaluated	19	22	20	23
Foetuses evaluated	127	162	140	160
Live	127	162	140	160
Dead	0	0	0	0
Total malformations
Foetal incidences	0	0	0	0
Litter incidences	0	0	0	0
Affected foetuses/litter	0	0	0	0
Total anomalies
Foetal incidences	11	14	9	31*
Litter incidences	7	11	6	16
Affected foetuses/litter	8.41	8.47	6.149	20.78
Total variations
Foetal incidences	126	162	140	160
Litter incidences	19	22	20	23
Affected foetuses/litter	99.25	100	100	100

* p≤ 0.05

Applicant's summary and conclusion

Conclusions:

Under the conditions of the study, administration of the test material at doses above 30 mg/kg bw/day elicited maternal toxicity, characterised by reduced maternal net weight loss. The litters of these animals showed reduced foetal weight and an increased incidence of skeletal abnormalities. In the remaining litters, the incidence of foetal effects did not greatly differ from normal values. There was no adverse effect of treatment, maternal or foetal, at 30 mg/kg/day in this study. The NOAEL for both maternal and embryo/foetotoxicity in this study was therefore considered to be 30 mg/kg bw/day.
The study is considered to be reliable, relevant and adequate for risk assessment and classification and labelling purposes.

Executive summary:

In a GLP compliant study conducted in line with standardised guidelines OECD 414 and EPA OPP 83-3, the effect of the test material on developmental toxicity was determined in the rat. Rats were administered the test material daily, by oral (gavage), at 0, 30, 300 and 1000 mg/kg bw from day 6 to day 15 post coitum. The animals were checked daily for clinical signs and mortality and body weight and food consumption were measured daily. Maternal animals were sacrificed on day 21 post coitum and subjected to gross necropsy. The uteri were dissected and contents examined. Foetuses were weighed, sexed and inspected for external, visceral and skeletal abnormalities. During the study there were no premature mortalities.

 

In the high dose group, maternal toxicity was evidenced by an 11% decrease in food consumption over the period of dosing and a 21% decrease of carcass weight minus day 6 weight. Slight but statistically significant reduction in foetal weight and increased incidences of a few skeletal variations were considered to be the consequence of a delay in foetal development and therefore secondary to maternal toxicity.

 

In the mid-dose group a significant 6 % reduction in food consumption over the period of treatment was also observed and the carcass weight minus day 6 weight was reduced by 17 %. Lower foetal weights and increased incidences of incomplete ossification of posterior digit phalanges were also recorded.

 

In the low dose group no treatment-related findings were observed.

 

Under the conditions of the study the test material was not embryotoxic, foetotoxic, or teratogenic in rats. A slight reduction in foetal weight and increased incidences of a few skeletal variations were considered related to delayed development and secondary to maternal toxicity at 300 and 1000 mg/kg and based on these observations, the maternal and foetal NOAELs were defined as 30 mg/kg.