[1,2,4]Triazolo[1,5-a]pyrimidine-2-sulfonamide, N-(2,6-difluorophenyl)-5-methyl-

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 February 1988 to 15 November 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 83-3 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

EC Number:

619-383-6

Cas Number:

98967-40-9

Molecular formula:

C12H9F2N5O2S

IUPAC Name:

N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

Constituent 2

Reference substance name:

2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide

IUPAC Name:

2',6'-difluoro-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonanilide

Constituent 3

Reference substance name:

N-(2',6'-difluorophenyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

IUPAC Name:

N-(2',6'-difluorophenyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

Details on test material:

- Name of test material (as cited in study report): XRD-498

- Analytical purity: 99.8%

- Lot/batch No.: AGR 240043

Test animals

Species:

rat

Strain:

Fischer 344

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory
- Age at study initiation: adult
- Weight at study initiation: 175-225 g
- Fasting period before study: no data
- Housing: one male per one female
- Diet (e.g. ad libitum): Purina Certified Chow #5002, ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period:

ENVIRONMENTAL CONDITIONS
Animal rooms are designed to maintain adequate environmental conditions concerning temperature, relative humidity, airflow, and lighting.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: Purina Certified Chow #5002

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: XRD-498 diets were prepared by serially diluting a test material-feed concentration according to Standard Operating Procedures.

DIET PREPARATION
- Rate of preparation of diet (frequency):Test diets were prepared once during the course of study, consistent with previous stability data, and samples from each mix were submitted for analytical verification of dietary concentrations. XRD-498 was shown to be stable in rodent chow for up to 37 days and to be dispersed homogeneously using standard dietary preparation techniques.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentration of XRD-498 was determined by high performance liquid chromatography using a UV detector, following extraction from the rodent chow and a partial clean-up procedure.

Details on mating procedure:

Adult virgin females were bred overnight with males of the same strain (one male: one female) with Day 0 of gestation determined by the presence of sperm in vaginal lavage samples.
- Impregnation procedure: [ cohoused]
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: overnight


- Verification of same strain and source of both sexes: [yes]
- Proof of pregnancy: [ sperm in vaginal smear] referred to as [day 0 ] of pregnancy

Duration of treatment / exposure:

Groups of 30 bred female rats were provided the test material in the diet on Days 6-15 of gestation. Control diet was provided on Days 0 through 5 and 16 through 21 days of gestation. On the morning of Day 6 of gestation, the control diets were replaced with diets containing the test material at concentrations sufficient to provide the targeted dose levels of 0, 100, 500, or 1000 mg/kg/day.

Frequency of treatment:

Daily

Duration of test:

Days 6-15 of gestation

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
100 mg/kg/day
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
500 mg/kg/day
Basis:
actual ingested

Doses / concentrations 4

Remarks:

Doses / Concentrations:
1000 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

30 bred females per dose

Control animals:

yes

Details on study design:

- Dose selection rationale: Test diets were prepared to provide targeted dose levels of 0, 100, 500 or 1000 mg/kg body weight/day based on projected growth curves and historical feed consumption data from previous teratology studies.
- Rationale for animal assignment (if not random): Random

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Days 0,3,6,9,12,16,18,and 21 days of gestation

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes



POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #21
- Organs examined: maternal liver, kidney, gravid uterina and cecal weights, kidneys.

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
- Other:

Fetal examinations:

- External examinations: Yes: [all per litter ]
- Soft tissue examinations: Yes: [half per litter ]
- Skeletal examinations: Yes: [all per litter ]
- Head examinations: Yes: [ half per litter ]

Statistics:

Descriptive statistics (means and standard deviations) were reported for feed and water consumption. Maternal body weight and weight gains, and absolute and relative organ weights, and average fetal body weights were evaluated by Bartlett's test for equality of variance. Based on the outcome of Bartlett's test, a parametric or nonparametric analysis of variance was performed. If the ANOVA was significant, analysis by Dunnett's test of the Wilcoxon Rank-Sum test with Bonferroni's correction was performed. Statistical evaluation of the frequency of pre-implantation loss, resorptions and fetal alterations among litters and the fetal population was performed using a censored Wilcoxon Test with Bonferroni's correction. The fetal sex ratio was analyzed by binomial distribution test. The pregnancy rate was analyzed by the Fisher exact probability test. The number of corpora lutea and implantations, and litter size were analyzed by the Wilcoxon Rank-Sum test with Bonferroni's correction. Statistical outliers were identified, however, only outliers for feed and water consumption values were excluded from analyses.

Indices:

No information

Historical control data:

All of the alterations observed in this study have been observed previously in this laboratory among historical control groups at comparable incidences.

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 clinical signs of changes in appearance observed in any of the test groups. No statistically significant effects were noted in maternal body weights or body weight gains in any of the treatment groups when compared to controls. There were no significant changes in feed or water consumption in any of the treated groups when compared to controls. Evaluation of organ weight data revealed statistically significant increases in absolute and relative cecal weights at 1000 mg/kg/day consistent with results observed in previous dietary studies.

Examination of the reproductive parameters revealed a statistically significantly higher pregnancy rate at 1000 mg/kg/day than in the controls, and a higher percentage of female pups than expected in this group as well. Number of implantations among rats given 1000 mg/kg/kday was 20% lower than among the controls, which resulted in a statistically significant increase in pre-implantation loss at this dose level. This decrease in the number of implantations also resulted in a 20% decrease in gravid uterine weight. These changes were not considered treatment-related. There were no significant differences in the percentage of implantations resorbed or fetal body weights in any treatment group when compared to controls. No statistically significant differences were observed at 100 or 500 mg/kg/day in any of the reproductive parameters measured.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

1 000 other: mg/kg bw/day (actual ingested)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOEL

Effect level:

1 000 other: mg/kg bw/day (actual ingested)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no significant differences in any of the test groups of fetuses when compared to controls. A total of five fetuses in this study exhibited malformations. Of these, one control fetus, two fetuses at 500 mg/kg/day and one fetus at 1000 mg/kg/day exhibited microphthalmia. The remaining malformed fetus (500 mg/kg/day) exhibited fused and hemi-vertebrae. All of the alterations observed in this study have been observed previously in this laboratory among historical control groups at comparable incidences. There were no indications of delays in skeletal ossificiation in any of the treatment groups when compared to the controls.

Effect levels (fetuses)

Dose descriptor:

NOEL

Effect level:

1 000 other: mg/kg bw/day (actual ingested)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

No evidence of embryo/fetotoxicity or teratogenicity was observed at any dose level tested. Based on these results, the developmental no-observed effect level for XRD-498 in rats was 1000 mg/kg/day.

Executive summary:

XRD-498 was evaluated for embryo/fetotoxic and teratogenic potential in Fischer 344 rats. Groups of 30 bred female Fischer 344 rats were given diets that provided targeted dose levels of 0, 100, 500 or 1000 mg/kg body weight/day on Days 6 through 15 of gestation. The fetuses were examined on Day 21 of gestation for potential alterations. Consistent with effects noted in previous dietary toxicity studies of XRD-498, statistically significant increases were observed in the absolute and relative full and empty cecal weights of rats given 1000 mg/kg/day. Cecal weights at lower dose levels were comparable to those of controls. No evidence of embryo/fetotoxicity or teratogenicity was observed at any dose level tested. Based on these results, the developmental no-observed-effect level (NOEL) for XRD-498 in rats was 1000 mg/kg/day.