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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
06 March 2020 to 03 April 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2020

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
Sprague-Dawley
Remarks:
Crl:CD(SD)
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC
- Age at study initiation: 11–13 weeks old (on Gestation Day 1, 2, 3, or 4)
- Weight at study initiation: 221 and 300 g
- Fasting period before study: no
- Housing: Individually in polycarbonate, solid-bottom cages containing appropriate bedding material.
- Diet (e.g. ad libitum): PMI Nutrition International, LLC Certified Rodent LabDiet® 5002, ad libitum
- Water (e.g. ad libitum): Municipal tap water, ad libitum
- Acclimation period: yes

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20°C to 26°C
- Humidity (%): 30% to 70%
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours dark

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Dosing formulations were prepared at appropriate concentrations to meet dose level requirements, at weekly intervals. The dosing formulations were stirred continuously during dosing. The dosing formulations were stored at 18°C to 24°C, protected from light.


VEHICLE
- Justification for use and choice of vehicle (if other than water): Corn oil
- Concentration in vehicle: 0, 25, 75 and 250 mg/mL
- Amount of vehicle (if gavage): 4 mg/mL
- Lot/batch no. (if required): 2IH0387
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentration sample analysis was performed for all dose levels during the first and last preparation of the dose formulations. Dose analysis results were verified prior to dose administration at each sampling interval. If results were deemed unacceptable, the formulations were prepared again and analysed.
Test substance formulations have been previously shown to be stable and homogeneous over the range of concentrations used on this study for at least 8 days at room temperature (18°C to 24°C). Therefore, stability and resuspension homogeneity of test substance formulations were not assessed on this study.
Details on mating procedure:
The animals arrived at the lab on Gestation Day 1, 2, 3, or 4.
Duration of treatment / exposure:
Gestation Days (GD) 6–20
Frequency of treatment:
Daily
Duration of test:
20 days
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
Control group
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Remarks:
Low dose group (LD)
Dose / conc.:
300 mg/kg bw/day (actual dose received)
Remarks:
Middle dose group (MD)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Remarks:
High dose group (HD)
No. of animals per sex per dose:
25 females per group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The dosage levels were determined based on the results of a previous dose range-finding prenatal developmental toxicity study (Charles River, 2020b) and were provided by the Sponsor Study Monitor. In that study, the test substance was administered to 5 pregnant Sprague Dawley female rats per dose group via oral gavage from Gestation Days (GD) 6–20 at dose levels of 0, 500, 750, and 1000 mg/kg bw/day. See Charles River (2020b) for DRF study results.

- Rationale for animal assignment (if not random): random

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once daily
- Cage side observations checked included: mortality and general clinical observations

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once daily, beginning of the day of animal arrival and continuing through (and including) the day of euthanasia. Animals were removed from the cage.
Mortality and all signs of overt toxicity were recorded on the day observed. The observations included, but were not limited to, evaluations for changes in appearance of skin and fur, eyes, mucous membranes, respiratory and circulatory system, autonomic and central nervous systems, somatomotor activity, and behavior. On days of scheduled dosing, the observations were collected prior to dosing. At 0.5 to 2 hours post-dosing the animals were removed from the cage and were observed for findings that were potentially related to treatment.

BODY WEIGHT: Yes
- Time schedule for examinations: Gestation Days 5–21 (daily)

FOOD CONSUMPTION: Yes
- Time schedule for examinations: Gestation Days 5–21 (daily). Reported as g/animal/day for each corresponding body weight interval during gestation.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 21
- Organs examined: All surviving females were euthanized and subjected to a gross necropsy. The thoracic, abdominal, and pelvic cavities were opened, and the contents examined. The uterus of each dam was excised, and its adnexa trimmed. For all animals, the liver, kidneys, and thyroid gland were excised, weighed (thyroid post-fixation), and preserved in 10% neutral-buffered formalin. Gross lesions were also collected and preserved in 10% neutral-buffered formalin for possible future histopathologic examination. Thyroid glands for all animals in all groups were subjected to microscopic examination.

OTHER: Thyroid hormone analysis
- Time schedule for examinations: Blood samples were collected at GD 21, prior to necropsy. Serum samples were analysed for T3, T4, and TSH levels.
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
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: Yes: [half per litter]
Statistics:
Numerical data and clinical and necropsy observations data were summarized by sex and occasion or by litter. Means, standard deviations, percentages, numbers, and/or incidences were reported, as appropriate by dataset. Calculated values on the Provantis tables may not be reproducible from the individual values presented because all calculations are conducted using non-rounded values. Inferential Statistical Methods.All statistical tests were conducted at the 5% significance level. All pairwise comparisons were conducted using two sided tests and were reported at the 1% and 5% levels, unless otherwise noted. Levene’s test was used to assess the homogeneity of group variances.
The groups were compared using an overall one-way ANOVA F-test if Levene’s test was not significant or the Kruskal-Wallis test if it was significant. If the overall F-test or Kruskal-Wallis test was found to be significant, then pairwise comparisons were conducted using Dunnett’s or Dunn’s test, respectively. The groups were compared using an overall Kruskal-Wallis test. If the overall Kruskal-Wallis test was found to be significant, then the above pairwise comparisons were conducted using Dunn’s test. A Fisher’s exact test was used to conduct pairwise group comparisons of interest. The groups were compared using an overall one-way ANOVA F-test. If the overall F-test was found to be significant, then pairwise comparisons were conducted suing Dunnett’s test.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Description (incidence and severity):
No test substance related clinical observations were noted at the daily examinations or 0.5–2 hours following dose administration at any dosage level. Observations noted in the test substance-treated groups, including thin fur cover over various body surfaces, pale skin discoloration over various body surfaces, and decreased activity, occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not dose-related.
Mortality:
no mortality observed
Description (incidence):
All females in the control, 100, 300, and 1000 mg/kg bw/day groups survived to the scheduled necropsy on Gestation Day 21.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Mean maternal body weights, body weight gains, corrected body weights and corrected body weight gains in the 100, 300, and 1000 mg/kg bw/day groups were unaffected by test substance administration. Differences from the control group were slight and not statistically significant.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Mean maternal food consumption, evaluated as g/animal/day, in the 100, 300, and 1000 mg/kg bw/day groups was unaffected by test substance administration. Differences from the control group were slight and not statistically significant.
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
No test substance-related organ weight changes were noted.
Gross pathological findings:
no effects observed
Description (incidence and severity):
At the scheduled necropsy on Gestation Day 21, no test substance-related gross findings were noted. The gross findings observed were considered incidental, of the nature commonly observed in this strain and age of rat, and/or were of similar incidence in control and treated animals and, therefore, were considered unrelated to administration of the test substance.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
No test substance-related microscopic findings were noted. The microscopic findings observed were considered incidental, of the nature commonly observed in this strain and age of rat, and/or were of similar incidence and severity in control and treated animals and, therefore, were considered unrelated to administration of the test substance.
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed
Description (incidence and severity):
No test substance-related effects on thyroid hormone levels were noted at any dosage level. Mean T3, T4, and TSH concentrations in the 100, 300, and 1000 mg/kg bw/day groups were generally comparable to and not statistically significantly different than the control group.

Maternal developmental toxicity

Number of abortions:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Pre- and post-implantation loss:
effects observed, non-treatment-related
Description (incidence and severity):
The mean litter proportion of postimplantation loss (primarily late resorptions) in the 1000 mg/kg bw/day group (10.54%) was slightly higher when compared to the concurrent control group (6.26%). This difference was attributed to 1 female in the 1000 mg/kg bw/day group with total litter loss and not related to test substance administration.
Mean litter proportions of postimplantation loss in the 100 and 300 mg/kg bw/day groups were generally comparable to the control group; differences were slight, not statistically significant, and/or did not occur in a dose related manner.
Mean numbers of corpora lutea and implantation sites and the mean litter proportions of pre implantation loss were similar across all groups.
Total litter losses by resorption:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Early or late resorptions:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Dead fetuses:
no effects observed
Description (incidence and severity):
There was no effect on mean number of live fetuses versus the control group and the mean values in all test substance treated groups were within the range of values in the Charles River Ashland historical control data.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Other effects:
no effects observed

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects were observed.

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
Mean fetal body weights (male, female, and combined sexes) in the 100, 300, and 1000 mg/kg bw/day groups were generally comparable to the control group; differences were slight, not statistically significant, and/or did not occur in a dose related manner.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
The numbers of fetuses (litters) available for morphological evaluation were 309(25), 293(24), 282(25), and 292(24) in the control, 100, 300, and 1000 mg/kg bw/day groups, respectively. There was no effect on mean number of live fetuses versus the control group and the mean values in all test substance treated groups were within the range of values in the Charles River Ashland historical control data.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Changes in litter size and weights:
no effects observed
Description (incidence and severity):
No effects were noted at any of the treatment groups.
Changes in postnatal survival:
not examined
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
No test substance-related external malformations were observed in fetuses in this study. In the 1000 mg/kg bw/day group, a single low-weight (4.48 g) fetus had oedema (entire subcutis). In the 300 mg/kg bw/day group, one fetus had a thread-like tail (5 mm in length) and an absent anus. Due to the occurrence in single fetuses (litters), and in the absence of signs of maternal/developmental toxicity at these dosage levels, these malformations were not considered test substance-related.
No external developmental variations were observed in fetuses in this study.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
No test substance-related skeletal malformations were observed in fetuses in the study.
One fetus in the 1000 mg/kg bw/day group had sternoschisis (sternebrae Nos. 5 and 6), another ferus had absent caudal vertebrae (corresponding with external malformation of threadlike tail, see Section 8.10.1.), and a third fetus in the 100 mg/kg bw/day group had absent lumbar vertebrae. Due to the occurrence in single fetuses (litters), the presence of a comparable findings in control group fetuses (absent lumbar vertebrae), and in the absence of signs of maternal/developmental toxicity at these dosage levels, these malformations were not considered test substance-related. Malformations of absent lumbar vertebrae were seen in five fetuses in the control group.
No test substance-related skeletal developmental variations were noted. Findings observed in the test substance treated groups were noted infrequently, similarly in the control group, were not observed in a dose-related manner, the differences in the mean litter proportions were not statistically significant compared to the concurrent control group, and/or the values were within the ranges of the Charles River Ashland historical control data.
Visceral malformations:
no effects observed
Description (incidence and severity):
No visceral malformations were observed in the fetuses in the study.
No test substance-related visceral developmental variations were noted. Findings observed in the test substance treated groups were noted infrequently, similarly in the control group, were not observed in a dose-related manner, the differences in the mean litter proportions were not statistically significant compared to the concurrent control group, and/or the values were within the ranges of the Charles River Ashland historical control data.
Other effects:
no effects observed
Description (incidence and severity):
Mean absolute and relative (to the cube root of body weight) anogenital distances (male, females, and combined sexes) in the 100, 300, and 1000 mg/kg bw/day groups were comparable to the control group.

Effect levels (fetuses)

Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were observed.

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
no

Any other information on results incl. tables

The analyzed dosing formulations contained 98.5% to 111% of the test substance which was within the protocol-specified range of target concentrations for suspensions (85% to 115%) and were homogeneous.

Applicant's summary and conclusion

Conclusions:
In the prenatal developmental toxicity study, conducted according to OECD Test Guideline 414 and in compliance with GLP, the maternal and developmental NOAELs for 3,3-bis[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-1,5-divinyltrisiloxane were concluded to be greater than 1000 mg/kg bw/day based on no adverse effects observed.