Registration Dossier

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:
25th of October 2019 to 9th of June 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

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

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Version / remarks:
Adopted 25 June 2018
Deviations:
yes
Remarks:
General clinical observation were not recorded for several animals on one weekend
GLP compliance:
yes (incl. QA statement)
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Trimethoxyvinylsilane
EC Number:
220-449-8
EC Name:
Trimethoxyvinylsilane
Cas Number:
2768-02-7
Molecular formula:
C5H12O3Si
IUPAC Name:
ethenyltrimethoxysilane
Test material form:
liquid

Test animals

Species:
rabbit
Strain:
New Zealand White
Remarks:
Crl: KBL
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: Approximately 19-25 weeks
- Weight at study initiation: males: 4060 – 3377 g (mean: 3681 g ± 20 % = 2945 – 4418 g)
females: 4190 - 2519 g (mean: 3472 g ± 20 % = 2777 – 4166 g)
- Fasting period before study: no
- Housing: Housed in ABS-plastic or Noryl rabbit cages, floor 4200 cm2, semi barrier housing in an air-conditioned room.
- Diet: Altromin 2123 (manufactured by Altromin Spezialfutter GmbH & Co.KG, Im Seelenkamp 20, D-32791 Lage) maintenance diet for rabbits, rich in crude fibre, ad libitum
- Water: tap water (with municipal residue and microbiological controls at regular intervals), ad libitum
- Acclimation period: At least 5 days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 ± 3 °C
- Humidity (%): 55 ± 10 %
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): 12 hours light, 12 hours dark

IN-LIFE DATES: Not specified

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test substance was weighted and the vehicle was added to the appropriate final concentrations. The formulation was vortexed and/or stirred until visual homogeneity was achieved. After homogenisation, the formulation was overlaid with argon to prevent instability caused by repeated contact of the test substance formulation with air. The test substance formulations were prepared once every 9 days (within the stability time frame). Formulates were kept under magnetic stirring during the daily administration. The prepared formulation was stored protected from light and at room temperature.

VEHICLE
- Justification for use and choice of vehicle: The vehicle has been selected in consultation with the sponsor based on the test item’s characteristics. The test item was dissolved in dried and de-acidified corn oil.
- Concentration in vehicle: 0, 7.5, 25, 75 mg/mL
- Amount of vehicle: 1 mL/kg bw
- Lot/batch no.: Sigma-MKCH1635, MKCK6411, Caelo-19112904
- Purity: not specified
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Before beginning of the treatment period, formulation samples were prepared and analysed in order to obtain knowledge about stability and homogeneity of the test item in the selected vehicle. The test item was shown to be homogenous and samples were not collected during the main study for the investigation of homogeneity. Samples were taken in duplicate during the main study only for substance concentration analysis in the first, third, fifth and last weeks of the study for all doses including the vehicle control.
Details on mating procedure:
- Impregnation procedure: Cohoused
- If cohoused: A female was taken to a male’s cage
- M/F ratio per cage: 1:1 ratio (male to female)
- Length of cohabitation: Until mating was confirmed
- In case of unsuccessful mating, the female was taken back to its original cage and mating of the female with another male or at another time was considered.
- Further matings after two unsuccessful attempts: Not specified
- Verification of same strain and source of both sexes: Yes
- Proof of pregnancy: Visual inspection and based on the falling of male on its back or side and emittance of a typical cry. The day on which a confirmed mating was observed is referred to as day 0 of pregnancy
- Any other deviations from standard protocol: No
Duration of treatment / exposure:
Between GD 6 to GD 27
Frequency of treatment:
Daily
Duration of test:
28 days
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day
Remarks:
Control
Dose / conc.:
7.5 mg/kg bw/day
Remarks:
Low Dose, LD
Dose / conc.:
25 mg/kg bw/day
Remarks:
Middle Dose, MD
Dose / conc.:
75 mg/kg bw/day
Remarks:
High Dose, HD
No. of animals per sex per dose:
20 pregnant females per group.
16 males for mating only
100 females in total
In total 116 animals
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: A previous dose range finding study examined the developmental effects at doses of 0, 100, 250 and 400 mg/kg bw/day. Test item-related maternal toxicological effects in terms of reduced body weight gain, food consumption and gravid uterine weight were observed at 100, 250 and 400 mg/kg bw/day; slightly lower carcass weight was observed at the 400 mg/kg bw/day dose group; reduced male and female foetal weight was seen in all the dose groups and inflammatory, degenerative and hyperplastic lesions in the urinary tract organs were reported in all dose groups. Based on these results and and in consultation with the sponsor, the following doses were selected for the 3 dose groups: 0 mg/kg bw/day for the control (C) group, treated with the vehicle corn oil, 7.5 mg/kg bw/day for the low dose (LD), 25 mg/kg bw/day for the middle dose (MD) and 75 mg/kg bw/day for the high dose (HD).
- Rationale for animal assignment: randomised

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed for morbidity and mortality twice daily except on weekends and public holidays when observations were made once daily. However, one deviation from the protocol was that clinical signs were not recorded for some animals for 2 days, on a weekend.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: General clinical observations were made at least once per day. Clinical observations included spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size. Changes in gait, posture, response to handling, as well as the presence of colonic or tonic movements, stereotypes or bizarre behaviour were also recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: All animals were weighed once before initiation of pairing to ensure that the body weights were within ±20 % variation.
The mated females were weighed on GDs 0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 28.
Males were not weighed in this study except once before initiation of pairing

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
Food consumption of pregnant females were measured for the following intervals: GD 0-3, 3-6, 6-9, 9-12, 12-15, 15-18, 18-21, 21-24, 24-27 and 28.
Food consumption was not measured for males during the entire study or for females before confirmation of mating.

WATER CONSUMPTION AND COMPOUND INTAKE: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 28
- Organs examined: The urinary tract (kidneys, ureter and urinary bladder) and liver were examined histopathologically.
Ovaries and uterine content:
The ovaries and uterine content were 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: [all per litter]
- Skeletal examinations: Yes: [all per litter]
- Head examinations: Yes: [half per litter]
- Other: Once the soft tissue evaluation of all foetuses was completed, half of the foetuses were decapitated. Foetuses with intact heads and without heads were then processed for skeletal and cartilaginous double staining by Alcian blue and Alizarin red and evaluated for skeletal anomalies.
Statistics:
Toxicology and pathology data were captured either on paper according to appropriate SOPs or using the validated computerised system Ascentos® System (version 1.3.4, Pathology Data Systems Ltd.).
A statistical assessment of the results of the body weight and food consumption was performed by comparing values of dosed animals with control animals using a one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, thyroid hormones and foetal evaluation parameters like external, visceral, craniofacial and skeletal parameters were statistically analysed by comparing values of dosed with control animals using either a parametric one-way ANOVA and a post-hoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test, based on the results of homogeneity and normality tests. The statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.3.4 software (p<0.05 is considered as statistically significant).

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
There were no treatment-related clinical signs observed in the females of any of the treatment group.

Clinical signs observed on a few days during the treatment period of the study. LD group: skin and fur, hairless area (right hind paw) in one animal on GDs 26-27; in one animal on the right or left hind paw on GDs 20-28; skin and fur, hairless area (left forelimb and hind limb) in one animal on GDs 25-28 and skin and fur, hairless area (left hind limb) in one animal on GDs 19-22 and GDs 25-28.
MD group: skin and fur, scratch/cut (neck) was observed in one animal on GD 0. Skin and fur, hairless area (left fore and hind paw, right forepaw) was observed in one animal on GDs 7-28 and 8-17.
HD group: skin and fur, hairless area (left and right hind paw) was observed in one animal on GD 25-28; in one animal on the left and right hind limb on GDs 24-28 and 26-28 and in one animal on the left and right hind paw on GDs 21-25 and GDs 21-28, respectively.
These clinical signs are considered to be incidental findings and not related to treatment with test item.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Description (incidence):
No test item-related mortality was observed during the treatment period and all animals survived until the end of the study.

One control group rabbit was found dead immediately after dosing on GD 7. It showed clinical signs of cough/sneezing at the post dose observation. Macroscopic observation revealed dark and abnormal red colour lungs. The cause of the death is assumed to be a gavage error during administration.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
The mean body weight remained unaffected by the treatment with the test item and slightly increased with the progress of the study in all groups throughout the study period. No statistical significance was achieved in any treatment groups on any day or interval of body weight measurement and all values in the treatment groups were comparable to the controls. The inconsistent and statistically non-significant decreases or increases observed on different days of body weights measurement in the treatment groups between GD 3 and GD 27 are considered to be incidental and not test item-related.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Food consumption in the LD, MD and HD groups was comparable to the control. Slightly lower food consumption was observed on GDs 9-12 and 21-24 in the LD group (9.31% and 16.38 % respectively, below control). Other slight differences in food consumption did not follow any dose-dependency in the treated groups and thus were not considered toxicologically relevant.
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 item-related effects of statistical or toxicological relevance were noted for the uterine weight
Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
No test item-related gross pathological changes of toxicological significance were observed during the macroscopic examination of the terminally sacrificed females of the control, LD, MD and HD groups.
A few specific macroscopic changes recorded in the female animals during the macroscopic examination at terminal sacrifice were dark/dark red colour lungs (1/25 in each control, LD and MD groups; abnormal coloured liver (1/25 in control), enlarged liver (1/25 in each control and MD group), red/white gallbladder (1/25 in control), small gallbladder (2/25 in LD group), enlarged gallbladder (1/25 in control, 2/25 in LD female, 2/25 in MD and 1/25 in HD), abnormal shape kidneys in one control, oviduct cyst (1/25 in control female and 2/25 in LD), abnormal shape uterus right horn in LD group (1/25 in LD group) and cyst in the uterus horns (2/25 in control, 1/25 in LD, 2/25 in MD group and 2/25 in HD group) and right uterus horn absent in LD female.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Microscopic changes that could be attributed to treatment with the test item were observed in the kidneys, urinary bladder and ureters of all groups treated with the test item.
In kidneys, diffuse transitional cell hyperplasia (urothelial hyperplasia) was observed in 5/25 and 4/25 animals from the MD and HD groups, respectively. Further, degenerative changes characterized by tubular dilatation (2/25, 10/25 and 8/25 in LD, MD and HD groups, respectively) and tubular basophilia (5/25, 8/25 and 1/25 in LD, MD and HD groups, respectively) were noted in animals from all dose groups.
In the urinary bladder, diffuse transitional cell hyperplasia (urothelial hyperplasia) was observed in 9/25, 12/25 and 17/25 animals from the LD, MD and HD treatment groups, respectively. The transitional cell hyperplasia was accompanied by submucosal oedema (2/25, 5/25 and 13/25 in LD, MD and HD groups, respectively) and congestion (5/25, 6/25 and 13/25 in LD, MD and HD groups, respectively) and in one MD group animal and one HD group animal, by accumulation of mixed cell infiltrates in the submucosa.
In ureters, diffuse transitional cell hyperplasia (urothelial hyperplasia) was noted in 10/25, 12/25 and 13/25 animals from the LD, MD and HD treatment groups, respectively.
Overall, the incidence and/or severity of the transitional cell hyperplasia increased in a dose-dependent manner, whereas for all the other changes described above, no clear dose-dependency was observed.
All the above-mentioned findings observed in the urinary tract were deemed to be adverse changes.
In the liver, no test item-related changes were observed. All observed hepatic changes were within the range of normal background lesions which may be observed in animals of this strain and age or were considered incidental lesions.
The remainder of microscopic findings recorded were within the range of normal background lesions which may be observed in animals of this strain and age or were incidental lesions that were not related to treatment with the test item.
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed

Maternal developmental toxicity

Number of abortions:
no effects observed
Description (incidence and severity):
None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice, except one LD female on GD 28.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
Mean preimplantation loss was 0.27, 0.09 and 0.26 in the LD, MD and HD groups, respectively, when compared to control (0.04). Mean post implantation loss was 0.91, 0.23 and 0.30 in the LD, MD and HD groups, respectively, when compared to control (1.50). These findings were observed without dose dependency and were considered to be a biological variation in this species.
Total litter losses by resorption:
not specified
Early or late resorptions:
no effects observed
Description (incidence and severity):
Mean early resorption was 0.27, 0.14 and 0.09 in the LD, MD and HD groups, respectively, when compared to control (0.79). Mean late resorption was 0.18, 0.09 and 0.22 in the LD, MD and HD groups, respectively, when compared to control (0.25). These findings were observed without dose dependency and were considered to be a biological variation in this species.
Dead fetuses:
no effects observed
Description (incidence and severity):
One pup in the control group and one pup in the LD group were dead at scheduled sacrifice. These findings were observed without dose dependency and were considered to be a biological variation in this species.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
None of the females showed signs of premature delivery prior to the scheduled sacrifice.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
Three LD, three MD, and two HD females were confirmed to be non-pregnant at scheduled sacrifice.
Other effects:
no effects observed
Description (incidence and severity):
Number of corpora lutea was not affected by the treatment.

Effect levels (maternal animals)

Key result
Dose descriptor:
LOAEL
Effect level:
ca. 7.5 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
histopathology: non-neoplastic

Maternal abnormalities

Key result
Abnormalities:
effects observed, treatment-related
Localisation:
other: Urinary tract

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
There were no test item-related effects of toxicological relevance observed for the mean foetus weight, male and female foetus weight on a per litter basis (group mean of individual litter mean) in any of the treatment groups when compared to control.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
There were no test item-related effects of toxicological relevance observed for the number of live offspring.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
The number of the difference in the sex ratio was unaffected by the test substance.
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
Foetal external examination on the day of terminal sacrifice revealed no test item-related external findings in foetuses of any of the treated groups.
Statistical analysis of data revealed no significant differences compared to the control group. One incidence of cleft palate was observed in one male pup no. 4 from animal no. 2 and considered to be incidental in nature.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Skeletal examination of the foetuses observed for skeletal and cartilaginous findings revealed a range of findings that were of a type or occurred at an incidence generally comparable to or slightly lower/higher in the treatment groups when compared to the control group.

A statistically significant lower foetal incidence of pelvic girdle, caudal shift was observed in the MD and HD groups (0%) when compared to control (13%). A statistically significant higher litter incidence of vertebra thoracic centrum/centra was observed in the MD group (81.8%) when compared to control (30.4%) and higher foetal incidences in the MD group (21.3) when compared to control (8.3%). A statistically significant higher litter incidence of dumbbell ossification in vertebra thoracic centrum was observed in the MD group (50%) when compared to control (13%). A statistically significant higher foetal incidence of bipartite ossification in vertebra thoracic centrum was observed in the MD group (14.4%) when compared to control (4.2%). A statistically significant higher foetal incidence of misaligned ossification of hind limb proximal phalanx was observed in the HD group (3.2%) when compared to control (0%). A statistically significant lower foetal incidence of unossified forelimb medial phalanx was observed in the LD group (27.1%) when compared to control (52.4%). A statistically significant higher litter incidence of unossified 6th sternebra was observed in the MD group (54.5%) when compared to control (13%). A statistically significant lower foetal incidence of long costal cartilage was observed in the HD group (32.7%) when compared to control (59%). A statistically significant lower foetal incidence of interrupted costal cartilage was observed in the LD, MD and HD groups (0% in each) when compared to control (4.6%). All these statistically significant findings were observed without any dose dependency, hence they are not considered to be test item-related, but rather spontaneous in nature.
Higher or lower litter incidences, but without achieving statistical significance were observed as mentioned below. Higher litter incidences of hole in the xiphoid (LD, MD and HD groups (19%, 22.7% and 34.8%, respectively) were observed compared to 26.1 % in control. Higher litter incidences of unossified forelimb proximal phalanx (LD, MD and HD groups (14.3%, 18.2% and 30.4%, respectively) were observed compared to 8.7% in control. Higher or lower litter incidence of skull hyoid body (incomplete ossification, unossified) was observed in treated groups (76.2 %, 81.8 % and 91.3 % in the LD, MD and HD groups, respectively) and control group (91.3 %). Higher or lower litter incidence of hind limb talus (incomplete ossification, unossified) was observed in treated groups (19 %, 18.2 % and 30.4 % in the LD, MD and HD groups, respectively) and control group (21.7 %).
Higher or comparable litter incidence of pelvic girdle, caudal shift was observed in the treated groups 52.4 %, 50 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (52.2 %). Higher or lower litter incidence of unossified 5th sternebra was observed in treated groups (42.9 %, 54.5 % and 73.9 % in the LD, MD and HD groups, respectively) and control group (69.6 %). Higher or lower litter incidence of incomplete ossification of 5th sternebra was observed in treated groups (76.2 %, 77.3 % and 91.3 % in the LD, MD and HD groups, respectively) and control group (87 %). Lower litter incidence of interrupted vertebra cervical cartilaginous ventral plate was observed in treated groups (42.9 %, 40.9 % and 43.5 % in the LD, MD and HD groups, respectively) and control group (52.2 %). Higher litter incidence of rudimentary ribs was observed in treated groups (76.2 %, 95.5 % and 78.3 % in the LD, MD and HD groups, respectively) and control group (65.2 %). Higher or lower litter incidence of unossified hind limb medial phalanx was observed in treated groups (23.8 %, 27.3 % and 60.9 % in the LD, MD and HD groups, respectively) and control group (30.4 %).
Higher or lower litter incidence of unossified and incomplete ossification of pelvic girdle pubis was observed in treated groups (28.6 %, 22.7 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (30.4 %). Higher litter incidence of incomplete ossification of 6th sternebra was observed in treated groups (42.9 %, 68.2 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (39.1 %). Higher litter incidence of misaligned costal cartilage was observed in treated groups (28.6 %, 27.3 % and 39.1 % in the LD, MD and HD groups, respectively) and control group (8.7 %). Higher litter incidence of nodulated costal cartilage was observed in treated groups (0 %, 18.2 % and 30.4 % in the LD, MD and HD groups, respectively) and control group (4.3 %). Higher or lower litter incidence of short costal cartilage was observed in treated groups (14.3 %, 45.5 % and 56.5 % in the LD, MD and HD groups, respectively) and control group (21.7 %).
The observed incomplete ossification of a few bones and other skeletal findings in the treatment groups were either marginally lower or higher and were not considered to be adverse. Generally delayed ossification is not regarded to persist postnatally as it is not associated with long-term consequences on survival, general growth and development. There was no indication of a test item-related trend in the type and/or incidences of other skeletal findings, therefore they were considered to be spontaneous in nature.

All the above findings are considered to be incidental and without dose dependency, as frequencies were even less in number compared to controls. Therefore, these findings are not considered to be treatment-related, but rather spontaneous in nature.
There were further non-statistically significant findings that were considered to be spontaneous in nature and not related to the treatment with the test item.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Internal observation of the foetal viscera revealed a range of visceral findings in all groups including control.

Higher litter incidence of dilated aortic arch - was observed in the MD group (9.1%) when compared to control (4.3%). Higher litter incidence of enlarged liver was observed in the HD group (8.7%) when compared to control (0%). Higher litter incidence of supernumerary liver lobe was observed in the MD and HD groups (36.4% and 30.4%, respectively) when compared to control (26.1%). Higher litter incidence of cleft at liver lobe was observed in the LD, MD and HD groups (23.8%, 50% and 34.8%, respectively) when compared to control (60.9%). Higher litter incidence of heart with large ventricle, thin ventricular wall and dilated ductus arteriosus was observed in the MD group (9.1% for each finding) when compared to control (0%). Higher litter incidences of small lung were observed in the MD group (9.1%) when compared to control (0%). Higher litter incidences of fluid-filled abdomen was observed in MD group (9.1%) when compared to control (4.3%). Higher litter incidences of discoloured kidney were observed in the MD group (9.1%) and dilated pelvis (13%) in the HD group when compared to control (0% for each observation). Higher litter incidences of large gall bladder were observed in the LD, MD and MD groups (14.3%, 13.6%, and 17.4%, respectively) when compared to control (0%).

Higher or lower litter incidences of small gall bladder were observed in LD, MD and MD groups (33.3%, 18.2%, and 17.4%, respectively) when compared to control (34.8%). Higher or lower litter incidences of discoloured gallbladder contents were observed in all treated groups (81%, 95.5%, and 87% in LD, MD and HD groups, respectively) when compared to control (87%).

Higher litter incidences of discoloured spleen were observed in the MD and HD groups (18.2%, and 8.7%, respectively) and small spleen in HD group (13%) when compared to control (4.3% for both observations). Higher litter incidences of discoloured thymus were observed in the LD, MD and HD groups (28.6%, 27.3%, and 30.4%, respectively) when compared to control (26.1%) and long thymus in the MD and HD groups (40.9% and 43.5%, respectively) when compared to control (39.1%).

Visceral findings observed in the dose groups were at frequencies generally comparable to or in some cases slightly higher or lower in frequency compared to controls. As observed findings were either minor variation and/or showed a lack of dose dependency and consistency, no serious toxicological significance can be attributed to these findings and they were considered to be spontaneous in nature.

There was no statistical significance observed in litter incidences of findings in treatment groups when compared with the control and no indication of a test item-related trend in the type and incidences of visceral findings.
Other effects:
effects observed, non-treatment-related
Description (incidence and severity):
Craniofacial examination by razor blade serial sectioning technique revealed no treatment-related findings in the dose groups when compared to the control group. However, a few findings were observed as described below;
A statistically non-significant lower or higher litter incidence of haemorrhages in the nasal cavity was observed in the LD, MD and HD groups (19%, 22.7% and 52.2%, respectively) when compared to control (30.4%). Though the findings for the HD group were slightly higher when compared to control, these findings are not considered to be treatment-related, but rather spontaneous in nature.
Single incidences of hematoma in the subdural region and subcutaneous hematoma in the head in the LD group (4.8 % above control for each observation) and subcutaneous hematoma in the head in the HD group (4.3%) were observed, when compared to control. These findings are not considered to be test item-related, but rather spontaneous in nature.

Statistical analysis of the data revealed no statistical significance for any of these findings.

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEL
Remarks:
foetal
Effect level:
>= 75 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no

Applicant's summary and conclusion

Conclusions:
In a prenatal developmental toxicity study in rabbits, conducted according to OECD Test Guideline 414 and in compliance with GLP, the LOAEL for maternal toxicity was concluded to be 7.5 mg/kg bw/day based on degenerative changes characterized by tubular dilatation and tubular basophilia in all dose groups; the NOAEL for developmental toxicity was concluded to be equal to or greater than 75 mg/kg bw/day based on no observed adverse effects in any of the foetuses.