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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:
Oct 2018 - Jul 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Version / remarks:
2001
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Limit test:
no

Test material

Constituent 1

Test animals

Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River UK Ltd
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: approx. 75 days
- Weight at study initiation: females 225-270 g
- Fasting period before study: no
- Housing: 4 females per cage during acclimatisation, 1 male and 1 female per cage during pairing ,1 female per cage during gestation
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 9 days

DETAILS OF FOOD AND WATER QUALITY: SDS VRF1 certified pelleted diet; potable water from public supply

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 40-70%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 h / 12 h

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
propylene glycol
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The required amounts of test material were weighed and approx. 50% of the final volume of vehicle was added and mixed with a magnetic stirrer until homogeneous. Then the final volume was adjusted and stirred until homogeneous.

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: 20, 60, 200 mg/ml
- Amount of vehicle (if gavage): 5 ml/kg bw
- Lot/batch no. (if required):
- Purity:
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentrations of dose formulations were analysed by HPLC/MS. The mean concentrations of WS400123 analysed in test formulations were within 5% of the nominal concentrations.
Details on mating procedure:
- Impregnation procedure: cohoused
- M/F ratio per cage: 1 : 1
- Length of cohabitation: until evidence of mating
- Verification of same strain and source of both sexes: yes, a colony of stud males was maintained
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
from day 6 till day 19 of gestation
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
300 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
20 females per dose
Control animals:
yes, concurrent vehicle
Details on study design:
Dose selection rationale: In an OECD422 study in Sprague Dawley rats, oral administration of WS400123 at dose levels of 100, 300 and 1000 mg/kg/day was well tolerated without adverse effects.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations : visual inspection for ill-health or reaction to treatment

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: days 0, 5, 12, 18, and 20

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 3, and daily from 6-20

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: full macroscopic examination of tissues
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: number of fetuses (live and dead)
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes : all per litter
Statistics:
The following sequence of statistical tests was used for body weight, gravid uterus weight, food consumption, corpora lutea, implantations, live young, fetal, placental and litter weight data:
A parametric analysis was performed if Bartlett's test for variance homogeneity (Bartlett 1937) was not significant at the 1% level. For pretreatment data, analysis of variance was used to test for any group differences. Where this was significant (p<0.05) inter group comparisons using t-tests, with the error mean square from the one-way analysis of variance, were made. For all other comparisons t/The F1 approximate test was applied. This test is designed to detect significant departure from monotonicity of means when the main test for the comparison of the means is a parametric monotonic trend test, such as Williams’ test (Williams 1971, 1972). The test statistic compares the mean square, NMS, for the deviations of the observed means from the maximum likelihood means, calculated under a constraint of monotonicity with the usual error mean square, EMS. The null hypothesis is that the true means are monotonically ordered. The test statistic is F1 = NMS/EMS which can be compared with standard tables of the F-distribution with 1 and error degrees of freedom. If the F1 approximate test for monotonicity of dose-response was not significant at the 1% level, Williams' test for a monotonic trend was applied. If the F1 approximate test was significant, suggesting that the dose response was not monotone, Dunnett's test (Dunnett 1955, 1964) was performed instead.

A non-parametric analysis was performed if Bartlett's test was still significant at the 1% level following both logarithmic and square-root transformations. For pretreatment data, Kruskal-Wallis’ test (Kruskal and Wallis 1952, 1953) was used to test for any group differences. Where this was significant (p<0.05) inter group comparisons using Wilcoxon rank sum tests (Wilcoxon 1945) were made.
Indices:
Prenatal losses were separated into pre- and post-implantation phases. Pre-implantation loss was considered to reflect losses due to non-fertilization of ova and failure to implant. It was calculated from the formula:
Pre-implantation loss (%) = (Number of corpora lutea – Number of implantations) x 100 / Number of corpora lutea

Where the number of implantations exceeded the number of corpora lutea observed, pre implantation loss was assumed to be zero (i.e. no pre-implantation loss was considered to have occurred).
Post-implantation loss was calculated from the formula:
Post-implantation loss (%) = (Number of implantations – Number of live fetuses) x 100 / Number of implantations

All group values and SD (as appropriate) were calculated from the individual litter values
Historical control data:
Historical control data from 10 studies performed from April 2018 to February 2019 with the same rat strain are provided in the report.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Mortality:
mortality observed, non-treatment-related
Description (incidence):
one animal of the control group died due to mal-dosing during gavage administration.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Figure Body weight of dams
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
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:
not examined
Gross pathological findings:
no effects observed
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter data
Total litter losses by resorption:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter data
Early or late resorptions:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter data
Dead fetuses:
no effects observed
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Other effects:
no effects observed

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other:
Remarks on result:
not determinable due to absence of adverse toxic effects

Maternal abnormalities

Key result
Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter and fetal weights
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter data
Changes in sex ratio:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter data
Changes in litter size and weights:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Litter and fetal weights
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Fetal major abnormality findings
Skeletal malformations:
no effects observed
Description (incidence and severity):
see Table Fetal minor skeletal abnormality findings
Visceral malformations:
no effects observed
Description (incidence and severity):
see "overall remarks, attachments" : Table Fetal minor visceral abnormality findings
Other effects:
no effects observed

Effect levels (fetuses)

Key result
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:
Remarks on result:
not determinable due to absence of adverse toxic effects

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no

Applicant's summary and conclusion

Executive summary:

Treatment of pregnant rats with WS400123 was well tolerated and there were no test-item related deaths.  Clinical condition, body weight performance, gravid uterine weight, adjusted body weight gain and food consumption were not adversely affected by WS400123 at any dose level investigated.  There were no macroscopic abnormalities detected at scheduled termination.  

There was no effect of maternal treatment with WS400123 on the mean numbers of corpora lutea, implantations, resorptions, live young, pre- and post- implantation losses, sex ratio or on placental, litter and fetal weights at any dose level investigated.

Evaluation of the fetuses did not reveal any adverse major, minor, skeletal or visceral abnormalities which were considered to be related to maternal treatment with WS400123.  

Based on the results of this embryo-fetal toxicity study, it was concluded that the dose level of 1000 mg/kg/day represented the No Observed Adverse Effect Level (NOAEL) for maternal toxicity and for embryo-fetal survival, growth and development.