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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:
2000
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Analogue substance tested; GLP study using standard method;

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report Date:
2000

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
other: Annex V (Developmental toxicity)
Qualifier:
according to
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
Qualifier:
equivalent or similar to
Guideline:
EU Method B.31 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rabbit
Strain:
New Zealand White
Details on test animals and environmental conditions:
TEST ANIMALS
time mated females from
- Source:Covance Research Products, Kalamazoo USA
- Age at study initiation: no data
- Weight at study initiation:no data
- Fasting period before study: none
- Housing: individually
- Diet : 170 g/d
- Water (e.g. ad libitum): ad lib
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19,4 - 21,1 ( 67 - 70 F)
- Humidity (%): 53-69
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Remarks:
0.5% carboxymethylcellulose
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test material was mixed to the 5 % CMC in water weekly to give an application volume of 10 ml/kg bw.

VEHICLE
- Concentration in vehicle: 0,5 % CMC in water
- Amount of vehicle (if gavage): 10 ml/kg bw
- Purity: no data
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
no data
Details on mating procedure:
no data; animals were purchased as "time-mated"
Duration of treatment / exposure:
day 7 through day 28 of gestation;
Frequency of treatment:
once daily
Dosing regime: 7 days/week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
100 mg/kg bw
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
400 mg/kg bw
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
800 mg/kg bw
Basis:
nominal conc.
No. of animals per sex per dose:
25 females
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Pilot study

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations: mortality, sign of toxicity, other findings were recorded on the day of observation

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule:daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION : Yes
- Food consumption for each animal determined and mean diet consumption calculated as g food/kg body weight/day: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #29
- Organs examined: general necropsy; special attention to: Uterus + contents, mammary glands
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: all per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter
Statistics:
yes
Group pairwise comparisons for each endpoint and time period (Levene's test, Dunnett's test & Welch test with Bonferroni correction)
Arcsine-Square root transformation for perdent values
Chi square test for sex distribution
Covariate analysis for each endpoint and time period litter size was used as a covariate
Kruskal-Wallis test for external and visceral abnormalities per litter
Pearson Chi-Square test for litter incidence for individual and total malformations.
Descriptive statistics: means + standard deviations
Historical control data:
no data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Eight females from the 800 mg/kg/day group died during the study and an additional one was terminated in extremis;
treatment-related clinical signs at this dose included convulsions, decreased defaecation, soft stool, discoloured faeces and reddish fluid in the refuse pan. As a result of the excessive mortality and maternal toxicity six females were selectively euthanised. Only three females survived to Day 29. Seven females in this treatment group aborted during the study and this effect was considered to be treatment- related.

All further information refers to the control, 100 and 400 mg/kg/day groups only.
Two females in the control group died on gestation day 23 and one from the 400 mg/kg/day grou died on gestation day 11. These deaths were not considered to be treatment-related and were due to intubation errors or mechanical injury.
Two females from the 400 mg/kg/day delivered early, this was considered to be treatment-related. Increased incidences of soft stool and decreased defaecation compared to the control group were also observed at 400 mg/kg/day. One female from the 100 mg/kg/day group aborted during the study, this effect was not thought to be treatment-related, as necropsy revealed injuries consistent with intubation error. One female from the the 400 mg/kg/day group aborted during the study, this effect was however considered to be treatment-related.
No treatment-related effects were observed on group mean bodyweight, bodyweight gain or food consumption at 100 or 400 mg/kg/day. Statistically significant differences were not observed in mean gravid uterine weights. There were no treatment-related internal findings noted at scheduled necropsy. Pregnancy rates were similar for each treatment group.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (nominal)
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEL
Effect level:
400 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes. Remark: secondary effects to maternal toxicity

Details on embryotoxic / teratogenic effects:
Effects on fetus - Gross:
No significant differences between treated or control animals were observed in the numbers of viable foetuses, litter size, pre-implantation losses or numbers of corpora lutea per dam. There were no treatment-related effects on the sex ratio of foetuses. A statistically significant decrease in male (8%) and female (8%) foetal bodyweight was observed at 400 mg/kg/day, resulting in a statistically significant decrease (8.7%) in combined sex foetal bodyweight at this dose. These changes may have been secondary to the maternal toxicity observed at this dose.
One foetus from each of the 100 and 400 mg/kg/day groups was observed with different major external abnormalities, but these were not considered to be toxicologically significant.
Effects on fetus - Soft tissue:
The only soft tissue malformation observed was gallbladder agenesis where 1 foetus in the 400 mg/kg/day group was affected, however the litter incidence was within historical control values. A number of soft tissue developmental variations (hypoplasia of the gall bladder, azygous lobe of lung absent and haemorrhagic iris) were also noted but these were not dose-related, were observed at similar frequencies in historical controls and therefore were not considered to be treatment-related. The litter incidence (9%) of the developmental variation, haemorrhagic iris, in the 400 mg/kg/day group was above the laboratory historical control value (6%) for this strain; this effect may have been secondary to the maternal toxicity observed at this dos e.
Effects on fetus - Skeletal:
No treatment-related increases in skeletal malformations or variations were observed in 100 or 400 mg/kg/day groups. Any skeletal malformations and developmental variations that were recorded were not dose-related, spontaneous in origin or were observed at similar frequencies in historical controls and therefore were not considered to be treatment-related.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The analogue substance 2 (refer to IUCLID chapter 13) did not cause direct developmental effects in rabbits treated from day 6 to 28 of gestation. Thus, the registered substance is also not expected to directly influence the prenatal development of rabbit offspring. Effects of maternal toxicity at high doese cannot be excluded.