Registration Dossier

Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental Starting Date: 04 August 2015 Experimental Completion Date: 01 December 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2016
Report Date:
2016

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Remarks:
clear, colorless
Specific details on test material used for the study:
Information as provided by the Sponsor.
Identification : 1,1,3,3-tetramethylbutyl peroxyneodecanoate (CAS# 51240-95-0)
Physical State/Appearance:Clear colorless liquid
Chemical Name:1,1,3,3-Tetramethylbutyl peroxyneodecanoate
Chemical Formula:C18H36O3
Purity:69.2%
Batch Number:1503447025
Label : TRIGONOX 423-C70 1,1,3,3-tetramethylbutyl peroxyneodecanoate 1kg Below -15°C Batch/lot: 1503447025 Expiry Date 14 June 2015
Date Received : 17 June 2015
Storage Conditions : Stored at approximately -20 °C, used/formulated under ambient conditions
Expiry Date : 15 April 2016
No correction for purity was made.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Limited, Margate, Kent
- Age at study initiation: Females prior to Day 3 of gestation
- Weight at study initiation: 187 - 285g
- Fasting period before study: No
- Housing: Individually in solid-floor polypropylene cages with stainless steel mesh lids furnished with softwood flakes (Datesand Ltd., Cheshire, UK).
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 50 ± 20%
- Air changes (per hr): at least 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From 04 August to 01 December 2015

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
arachis oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
VEHICLE
- Justification for use and choice of vehicle (if other than water): Oral gavage
- Concentration in vehicle: 0, 7.5, 43.8, 250 mg/mL
- Amount of vehicle (if gavage): 4 mL/kg
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples were taken of each test item formulation and were analyzed for concentration of 1,1,3,3-tetramethylbutyl peroxyneodecanoate (CAS# 51240-95-0) at Harlan Laboratories Ltd., Shardlow.

Stock solutions of the test item in acetonitrile were prepared for external standard calibration at a concetration of 1 mg/mL. Aliqupots of stock standard solutions were used to prepare working standard solutions in aceytonitrile with concentration of 0.1 mg/mL. On each occasion standard solutions derived from two standard stock solutions were used for calculation.

The fomulations received were extracted with acetonitrile. An aliquot of the test item formulation was accurately weighed into a volumetric flask and brought to volume with acetonitrile, ultra sonicated and centrifuged for 10 minutes. Where necessary sample solutions were further diluted with acetonitrile to achieve working concentrations. The test item concentration in the test samples was determined by gas chromatography (GC) using the external standard technique.
The accuracy and linearity determinations were determined under study number 41501125.

The formulations were found to comprise test item in the range of 98% to 103% and, thus, the required content limit of ±10% with reference to the nominal content was met. The results obtained during study number 41501125 indicate the accurate use of the test item in Arachis Oil BP as vehicle during this stiudy. The formulations were found to be homogeneoulsy prepared and sufficient formulation stability under storage conditions was proven.
The detection system was found to have acceptable linearity. The analytical system had acceptable recoveries of test item in vehicle. The method of analysis was validated and proven to be suitable for use.
Details on mating procedure:
The experimental animals were obtained time-mated from the supplier.
Duration of treatment / exposure:
The test item was administered by gavage to three groups each of twenty-four time mated Sprague-Dawley Crl:CD® (SD) IGS BR strain rats, between Days 5 and 19 of gestation inclusive at dose levels 30, 175 or 1000 mg/kg bw/day. A further group of twenty-four time mated females was exposed to the vehicle only (Arachis oil BP) to serve as a control.
Frequency of treatment:
Daily
Duration of test:
Experimental Starting Date: 04 August 2015
Experimental Completion Date: 01 December 2015
Doses / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
Control - 0 mg/mL
Dose / conc.:
30 mg/kg bw/day (actual dose received)
Remarks:
Low - 7.5 mg/mL
Dose / conc.:
175 mg/kg bw/day (actual dose received)
Remarks:
Intermediate - 43.8 mg/mL
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Remarks:
High - 250 mg/mL
No. of animals per sex per dose:
24 females per dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The animals were randomly allocated to treatment groups using a randomization procedure based on stratified body weight to ensure similarity between the treatment groups.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Yes
- Cage side observations checked in Table 2 and Appendix 1 were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Yes

BODY WEIGHT: Yes
- Time schedule for examinations: Yes

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

WATER CONSUMPTION: Yes
- Time schedule for examinations: Visual inspection

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: Ovaries and uteri
i) Number of corpora lutea
ii) Number, position and type of intrauterine implantation
iii) Fetal sex
iv) External fetal appearance
v) Fetal weight
vi) Placental weight
vii) Gravid uterus weight
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:
- Dead fetus

All implantations and viable fetuses were numbered according to their intrauterine position.

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:
Female body weight change, food consumption and gravid uterus weight: Shapiro Wilk normality test and Bartlett’s test for homogeneity of variance and one way analysis of variance, followed by Dunnett’s multiple comparison test or, if unequal variances were observed, on alternative multiple comparison test.
Most caesarean necropsy parameters and fetal parameters: Kruskal-Wallis non-parametric analysis of variance; and a subsequent pairwise analysis of control values against treated values using the Mann-Whitney ‘U’ test, where significance was seen.
Fetal evaluation parameters, including skeletal or visceral findings: Kruskal-Wallis non-parametric analysis of variance and Mann-Whitney ‘U’ test.
Probability values (p) are presented as follows:
p<0.001 ***
p<0.01 **
p<0.05 *
p≥0.05 (not significant)
Computerized sysyems used:
R Environment for Statistical Computing


Historical control data:
Historical control data used for comparison purposes for fetal examination findings and uterus weights.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Description (incidence and severity):
There were no clinical observations for any of the animals throughout the study.
Dermal irritation (if dermal study):
not specified
Mortality:
no mortality observed
Description (incidence):
There were no unscheduled deaths during the study.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
At all dose levels, females showed a dose-related reduction in group mean body weight gains over Days 5 to 6 of gestation with most animals from the 1000 mg/kg bw/day showing actual body weight losses. Subsequent recovery was evident for females receiving 30 or 175 mg/kg bw/day with periodic body weight gains for these animals remaining comparable with controls from Day 6 of gestation. Females treated with 1000 mg/kg bw/day also showed improvement in body weight performance following the initial affect such that body weight gains over Days 7 to 14 of gestation were comparable with controls; however, further reduction in body weight gain was observed over Days 14 to 17 of gestation resulting in lower cumulative body weight gains for these animals throughout the treatment period. The overall body weight gain for these females was approximately 21% lower than controls with body weight gain adjusted for gravid uterus contribution also being markedly lower than controls. The effect on body weight development for the 1000 mg/kg bw/day females was considered to be of toxicological significance.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
There was marked reduction in food consumption at the start of dosing for females given 1000 mg/kg bw/day. Gradual improvement was apparent, however, dietary intake for these animals remained statistically significantly lower than controls up to Day 17 of gestation. Taken together with the effect on body weight development at this dose level, this observation was considered to be of toxicological significance.
There was no effect of treatment on food intake at 30 or 175 mg/kg bw/day.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
no effects observed
Description (incidence and severity):
Daily visual inspection of water bottles did not reveal any overt intergroup differences.
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:
effects observed, treatment-related
Description (incidence and severity):
Group mean gravid uterus weight for females treated with 1000 mg/kg bw/day was also slightly lower than controls; however, it is worth noting that whilst 4/24 control females showed gravid uterus weights slightly above the historical data ranges the corresponding values for most females treated with 1000 mg/kg bw/day were within these ranges. Group mean body weight gain when adjusted for contribution from gravid uterus for these females was also markedly lower than controls and with most individual values below the historical control data ranges, this finding was deemed to be of toxicological relevance.
Gross pathological findings:
no effects observed
Description (incidence and severity):
For all dose groups, there were no statistically significant treatment-related trends in the proportion of fetuses (or litters) with evidence of external or visceral abnormalities. At 1000 mg/kg bw/day, a number of skeletal anomalies achieved statistical significance. These included incomplete ossification of occipital (supra-occipital) region, thoracic centrum and sternbrae, no ossification of metacarpal, and caudal vertebrae - less than 4 ossified. These observations are minor variants and although group mean values were outside the historical background data ranges, they were deemed likely due to a slightly slower fetal growth rate resulting from maternal toxicity rather than an indication of a direct effect of the test item on fetal development. Any other skeletal findings at all dose levels were considered to be within normal biological variation.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

Maternal developmental toxicity

Number of abortions:
not specified
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There was considered to be no detrimental effect of maternal treatment on litter data as assessed by numbers of implantations, in-utero offspring survival (as assessed by the mean numbers of early or late resorptions), live litter size, sex ratio and post-implantation losses at 30, 175 or 1000 mg/kg bw/day.
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Description (incidence and severity):
The number of late deaths for the 1000 mg/kg bw/day dose group was slightly higher than controls but the intergroup difference did not achieve statistical significance and with one litter (Female 86) from this dose group showing four late deaths this observation was deemed unlikely to be of any toxicological significance.
Changes in pregnancy duration:
not specified
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): no effects observed
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
All animals (24) in all dose groups, including control, became pregnant.
Other effects:
no effects observed
Details on maternal toxic effects:
The oral administration of 1,1,3,3-tetramethylbutyl peroxyneodecanoate (CAS# 51240-95-0) to pregnant rats by gavage during gestation Days 5 to 19, at dose levels of 30, 175 or 1000 mg/kg bw/day resulted in an adverse effect on body weight gain and food consumption at the high dose level. Although some improvement was evident, cumulative body weight gains for females treated with 1000 mg/kg bw/day remained lower than controls throughout the dosing period with body weight gain adjusted for the contribution of gravid uterus also being markedly lower than controls. Taking into consideration the overall results, the No Observed Adverse Effect Level’ (NOAEL) for the pregnant female was considered to be 175 mg/kg bw/day within the confines of this type of study.

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEL
Effect level:
<= 175 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
body weight and weight gain

Maternal abnormalities

open allclose all
Key result
Abnormalities:
effects observed, treatment-related
Localisation:
placenta
Description (incidence and severity):
Total placental weight for females at 1000 mg/kg bw/day was statistically significantly lower than controls (p<0.05). The corresponding values for the 30 or 175 mg/kg bw/day dose groups were comparable with controls.
Abnormalities:
effects observed, non-treatment-related
Localisation:
uterus
Description (incidence and severity):
The uterus of Female 77 at 1000 mg/kg bw/day was filled with yellow fluid but this female was pregnant at necropsy. This is an isolated finding, therefore unlikely to be related to treatment.

Results (fetuses)

Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
At 1000 mg/kg bw/day, group mean fetal weights were marginally lower than controls which resulted in slightly lower litter weight for this dose group. These findings were deemed likely due to maternal toxicity rather than a direct effect of treatment on fetal growth and development
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): effects observed, treatment-related
Field "Description (incidence and severity)" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.DescriptionIncidenceAndSeverityFetalPupBodyWeightChanges): At 1000 mg/kg bw/day, group mean fetal weights were marginally but statistically significantly lower than controls (p<0.001 for males, p<0.01 for females and p<0.001 for combined) resulting in statistically significantly lower litter weight (p<0.01).
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
There was considered to be no detrimental effect of maternal treatment on litter data as assessed by live litter size.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
There was considered to be no detrimental effect of maternal treatment on litter data as assessed by sex ratio.
Changes in litter size and weights:
effects observed, treatment-related
Description (incidence and severity):
At 1000 mg/kg bw/day, group mean fetal weights were marginally but statistically significantly lower than controls (p<0.001 for males, p<0.01 for females and p<0.001 for combined) resulting in statistically significantly lower litter weight (p<0.01).
Changes in postnatal survival:
not examined
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
At 1000 mg/kg bw/day, the number of small fetuses was slightly higher than controls, however, the mean percentage affected remained within the historical control data ranges and as such this finding was considered to be of no toxicological significance. Of other external findings, neither the type, incidence nor distribution indicated any obvious effect of maternal treatment on fetal development at any dose level
Skeletal malformations:
effects observed, treatment-related
Description (incidence and severity):
Skeletal Examination of fetuses/litters revealed a number of statistically significant anomalies in relation to controls (p<0.01). At 1000 mg/kg bw/day, these included incomplete ossification of occipital (supra-occipital) region (p<0.01), thoracic centrum (p<0.01) and sternbrae (p<0.05), no ossification of metacarpal (p<0.05), and caudal vertebrae - less than 4 ossified (p<0.001); group mean values for these anomalies were above the historical control data ranges and as such these intergroup differences were deemed to be treatment-related. These resulted in a higher percentage of the fetuses affected for the 1000 mg/kg bw/day dose group (p<0.01).

Fetuses/litters from 175 mg/kg bw/day dose group also showed statistically significantly higher incomplete ossification of thoracic centrum (p<0.05) although group mean value remained within the background data ranges and as such this observation was considered to be within normal biological variation.

Additionally, the skeletal anomaly of thoracic centrum – dumb bell shaped was statistically significantly higher for fetuses/litters from the 175 and 1000 mg/kg bw/day dose group when compared with controls (p<0.01); a dose-relationship was apparent but group mean values were within the background data ranges and as such these observations were considered to be incidental. Other statistically significant intergroup differences included interparietal (unossified areas) for the 30 and 175 mg/kg bw/day dose groups (p<0.05), incomplete ossification of hyoid and ossification of ventral arch for the 1000 mg/kg bw/day dose group (p<0.01) but corresponding mean values were lower than controls and these findings were considered to be incidental. Any other intergroup differences did not achieve statistical significance and group mean values were usually within the background data ranges.
Visceral malformations:
no effects observed
Other effects:
effects observed, non-treatment-related
Description (incidence and severity):
One fetus from a control litter appeared to be a conjoined twin showing a number of malformations including additional tail and forelimb, malpositioned and bulging eyes, open eye macroglossia, malpositioned pinnae, encephalocoele and full body oedema; these findings were deemed incidental.

Effect levels (fetuses)

open allclose all
Key result
Dose descriptor:
NOEL
Effect level:
<= 175 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
fetal/pup body weight changes
skeletal malformations
Key result
Dose descriptor:
NOAEL
Effect level:
<= 1 000 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
fetal/pup body weight changes
skeletal malformations

Fetal abnormalities

Key result
Abnormalities:
effects observed, treatment-related
Localisation:
skeletal: skull
skeletal: forelimb
skeletal: sternum
skeletal: vertebra
Description (incidence and severity):
Skeletal Examination of fetuses/litters revealed a number of statistically significant anomalies in relation to controls (p<0.01). At 1000 mg/kg bw/day, these included incomplete ossification of occipital (supra-occipital) region (p<0.01), thoracic centrum (p<0.01) and sternbrae (p<0.05), no ossification of metacarpal (p<0.05), and caudal vertebrae - less than 4 ossified (p<0.001); group mean values for these anomalies were above the historical control data ranges and as such these intergroup differences were deemed to be treatment-related. These resulted in a higher percentage of the fetuses affected for the 1000 mg/kg bw/day dose group (p<0.01).

Additionally, the skeletal anomaly of thoracic centrum – dumb bell shaped was statistically significantly higher for fetuses/litters from the 175 and 1000 mg/kg bw/day dose group when compared with controls (p<0.01); a dose-relationship was apparent but group mean values were within the background data ranges and as such these observations were considered to be incidental. Other statistically significant intergroup differences included interparietal (unossified areas) for the 30 and 175 mg/kg bw/day dose groups (p<0.05), incomplete ossification of hyoid and ossification of ventral arch for the 1000 mg/kg bw/day dose group (p<0.01) but corresponding mean values were lower than controls and these findings were considered to be incidental. Any other intergroup differences did not achieve statistical significance and group mean values were usually within the background data ranges.

Overall developmental toxicity

Developmental effects observed:
yes
Lowest effective dose / conc.:
175 mg/kg bw/day
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes
Relevant for humans:
yes

Any other information on results incl. tables

Table1     Summary of Female Performance

Category

Number of Females at Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Initial Group Size

24

24

24

24

Pregnant

24

24

24

24

 


 

Table2     Summary Incidence of Daily Clinical Observations

Dose Level (mg/kg bw/day)

Number of Animals

Clinical Observations

0 (Control)

24

No Abnormalities Detected

30

24

No Abnormalities Detected

175

24

No Abnormalities Detected

1000

24

No Abnormalities Detected

 


 

Table 3     Group Mean Body Weight Values

Dose Level (mg/kg bw/day)

 

Body Weight (g) at Day of Gestation

3

5

6

7

8

11

14

17

20

0 (Control)

mean

232.8

243.8

248.9

253.8

257.3

275.7

295.1

326.0

367.4

sd

22.0

24.3

24.6

24.8

25.7

26.2

28.8

32.7

36.0

n

24

24

24

24

24

24

24

24

24

30

mean

235.2

247.9

250.8

255.9

261.0

279.3

299.0

328.3

373.0

sd

19.2

22.3

20.7

21.4

20.7

21.5

22.8

26.6

27.7

n

24

24

24

24

24

24

24

24

24

175

mean

235.4

249.9

251.5

257.5

263.5

281.5

301.7

331.5

375.5

sd

16.9

17.6

18.8

17.4

17.4

19.6

20.8

23.3

24.5

n

24

24

24

24

24

24

24

24

24

1000

mean

234.0

248.8

243.7

245.3

252.8

270.4

287.9

305.8*

346.4*

sd

21.0

20.9

20.0

18.9

20.1

23.5

24.1

25.9

30.5

n

24

24

24

24

24

24

24

24

24

 


 

Table 4     Group Mean Body Weight Change Values

Dose Level (mg/kg bw/day)

 

Body Weight Change (g) during Days of Gestation

3 to 5

5 to 6

6 to 7

7 to 8

8 to 11

11 to 14

14 to 17

17 to 20

0 (Control)

mean

11.0

5.1

5.0

3.5

18.4

19.4

30.9

41.4

sd

7.6

5.3

2.7

3.8

4.2

3.7

6.1

6.0

n

24

24

24

24

24

24

24

24

30

mean

12.7

2.9

5.1

5.1

18.3

19.7

29.3

44.8

sd

6.6

5.7

4.2

4.8

3.0

3.5

6.8

5.8

n

24

24

24

24

24

24

24

24

175

mean

14.5

1.6

6.0

6.0

18.0

20.1

29.8

44.0

sd

5.2

6.8

5.6

5.1

5.7

3.6

4.1

4.9

n

24

24

24

24

24

24

24

24

1000

mean

14.8

-5.1***

1.6*

7.5

17.6

17.5

17.9***

40.6

sd

5.2

4.9

4.7

5.9

7.6

6.0

6.4

11.3

n

24

24

24

24

24

24

24

24

 

Dose Level (mg/kg bw/day)

 

Cumulative Body Weight Change (g) from Day 5 of Gestation

6

7

8

11

14

17

20

0 (Control)

mean

5.1

10.0

13.5

31.9

51.3

82.2

123.6

sd

5.3

6.3

7.4

7.9

9.5

13.2

16.5

n

24

24

24

24

24

24

24

30

mean

2.9

8.0

13.1

31.4

51.1

80.4

125.1

sd

5.7

6.3

6.1

6.4

7.8

11.6

14.2

n

24

24

24

24

24

24

24

175

mean

1.6

7.6

13.6

31.6

51.8

81.6

125.6

sd

6.8

5.1

5.6

7.7

9.3

11.0

13.5

n

24

24

24

24

24

24

24

1000

mean

-5.1***

-3.5***

4.0***

21.6***

39.1***

57.0***

97.6***

sd

4.9

6.6

7.1

10.7

12.3

15.9

20.6

n

24

24

24

24

24

24

24


 

Table 5     Group Mean Gravid Uterus Weight and Adjusted Body Weight and Body Weight Change Values

Dose Level (mg/kg bw/day)

 

Body Weight (g) on Days of Gestation

Body Weight Change (g) during Days of Gestation

Gravid Uterus Weight
(g)

Adjusted
Body Weight (g)
 Day 20

Adjusted
Body Weight Change (g)
5-20

5

20

5-20

0 (Control)

mean

243.8

367.4

123.6

83.113

284.3

40.5

sd

24.3

36.0

16.5

11.341

29.7

12.5

n

24

24

24

24

24

24

30

mean

247.9

373.0

125.1

84.197

288.8

40.9

sd

22.3

27.7

14.2

9.787

27.1

12.4

n

24

24

24

24

24

24

175

mean

249.9

375.5

125.6

83.782

291.8

41.8

sd

17.6

24.5

13.5

6.764

22.8

12.3

n

24

24

24

24

24

24

1000

mean

248.8

346.4

97.6

73.972**

272.4

23.7***

sd

20.9

30.5

20.6

11.928

21.6

13.9

n

24

24

24

24

24

24

 


 

Table 6     Group Mean Food Consumption Values

Dose Level (mg/kg bw/day)

 

Food Consumption (g/rat/day) between Days of Gestation

3 - 5

5 - 8

8 - 11

11 - 14

14 - 17

17 - 20

0 (Control)

mean

21.3

21.7

23.5

24.3

23.5

25.9

sd

2.8

2.8

2.8

2.5

3.0

3.2

n

24

24

24

24

24

24

30

mean

22.1

22.1

24.1

24.6

23.1

26.4

sd

3.7

1.8

2.0

2.3

2.5

2.8

n

24

24

24

24

24

24

175

mean

22.1

21.8

23.4

24.7

23.6

26.9

sd

2.9

2.6

3.5

2.8

2.9

3.2

n

24

24

24

24

24

24

1000

mean

22.5

13.1***

19.8***

21.7**

18.8***

25.1

sd

2.6

2.7

3.5

3.2

3.0

4.5

n

24

24

24

24

24

24

 


 

Table 7     Summary Incidence of Necropsy Findings

 

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

TERMINAL DEATH

 

 

 

 

Number of animals examined

24

24

24

24

Uterus: filled with yellow color fluid

0

0

0

1

No abnormalities detected

24

24

24

23

 

 

 


Table 8     Group Mean Litter DataValues

Dose Level (mg/kg bw/day)

 

Number of Corpora Lutea

Number of Implants

Number of Embryonic/Fetal Deaths

Implantation Loss
%

Number of Live Implants

%
Male
Fetuses

Mean Male Fetal Weight (g)

Mean Female Fetal Weight (g)

Mean Fetal Weight (g)

MeanPlacentalWeight
(g)

Litter Weight (g)

TotalPlacentalWeight
(g)

Early

Late

Total

Pre

Post

Male

Female

Total

0 (Control)

mean

13.8

13.5

0.0

0.1

0.2

2.1

1.1

6.9

6.5

13.4

52.0

4.062

3.881

3.982

0.581

53.128

7.717

sd

2.1

2.0

0.2

0.3

0.4

3.8

2.5

2.2

2.4

1.9

15.0

0.224

0.212

0.208

0.064

7.286

1.128

n

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

30

mean

14.1

13.8

0.3

0.0

0.3

2.8

2.4

6.8

6.6

13.4

50.7

4.187

4.008

4.095

0.582

54.687

7.798

sd

1.4

1.8

0.6

0.2

0.6

6.7

4.1

2.1

2.1

1.8

14.7

0.316

0.344

0.314

0.071

6.547

1.341

n

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

175

mean

14.0

13.7

0.2

0.1

0.3

1.7

2.1

6.6

6.8

13.5

49.7

4.113

3.899

4.014

0.554

53.839

7.415

sd

1.5

1.3

0.5

0.4

0.6

3.9

4.2

1.6

2.1

1.1

13.7

0.212

0.222

0.196

0.069

5.135

0.964

n

23

23

24

24

24

23

23

24

24

24

24

24

24

24

24

24

24

1000

mean

13.6

13.3

0.1

0.4

0.5

2.1

4.1

7.0

5.7

12.8

55.5

3.744***

3.602**

3.683***

0.544

46.796**

6.887*

sd

2.2

2.1

0.3

0.9

0.9

4.2

7.1

2.1

2.1

2.2

13.7

0.289

0.321

0.294

0.065

8.099

1.207

n

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

24

 


 

Table 9     Summary Incidence of Fetal External Findings

External Findings

Dose level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of fetuses (litters) examined

321 (24)

322 (24)

323 (24)

306 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Total Number Affected

3

3

1.1

4

4

1.2

3

2

0.9

6

6

1.9

Additional Tail

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Additional Forelimb

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Eyes malpositioned

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Full Body Odema

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Open Eye Macroglossia

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Encephalocoele

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Malpositioned Pinnae

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Bulging Eyes

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Small

1

1

0.3

1

1

0.3

2

1

0.6

5

5

1.6

Hematoma - Left Hind Limb

1

1

0.3

0

0

0.0

0

0

0.0

0

0

0.0

Hematoma - Above Tail

0

0

0.0

1

1

0.3

0

0

0.0

0

0

0.0

Thread Like Tail

0

0

0.0

1

1

0.3

0

0

0.0

0

0

0.0

Hematoma - Right Side of Head

0

0

0.0

1

1

0.3

0

0

0.0

0

0

0.0

Hematoma - Back

0

0

0.0

0

0

0.0

1

1

0.3

1

1

0.3

Hematoma - Top of Head

0

0

0.0

0

0

0.0

1

1

0.3

0

0

0.0

Pale

0

0

0.0

0

0

0.0

1

1

0.3

0

0

0.0

 


 

Table 10   Summary Incidence of Fetal Visceral Findings

Visceral Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

167 (24)

167 (24)

168 (24)

158 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

External/General

 

 

 

 

 

 

 

 

 

 

 

 

Hemorrhage

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Head

 

 

 

 

 

 

 

 

 

 

 

 

Tongue - short

0

0

0.0

2

2

1.1

0

0

0.0

0

0

0.0

Rugae - non-uniform patterning

15

13

8.9

15

9

10.0

9

7

5.2

6

6

3.8

Micropthalmia

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Anopthalmia

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Brain - lateral ventricle - enlarged

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Brain - third ventricle - enlarged

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Abdomen

 

 

 

 

 

 

 

 

 

 

 

 

Liver - additional lobe between right and left median

0

0

0.0

0

0

0.0

2

2

1.0

0

0

0.0

Liver - papillary process - reduced in size

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Spleen - reduced in size

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Umbilical artery - left-sided

1

1

0.7

1

1

0.6

0

0

0.0

2

2

1.2

Testis - partially undescended

0

0

0.0

0

0

0.0

0

0

0.0

1

1

0.5

Ureter - kinked

34

14

20.7

29

18

18.2

15

8

9.4

19

9

11.5

Ureter - dilated

30

12

18.4

20

13

12.9

15

7

9.2

12

8

7.2

Renal pelvis cavitation - increased

13

8

7.9

20

10

12.1

8

6

5.0

15

6

9.2

Renal papilla - absent

1

1

0.6

3

3

1.8

2

2

1.1

1

1

0.6

l


 

Table10(continued)           Summary Incidence of Fetal Visceral Findings

Visceral Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

167 (24)

167 (24)

168 (24)

158 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Thorax

 

 

 

 

 

 

 

 

 

 

 

 

Thymus - lobe partially undescended

4

4

2.3

2

2

1.1

10

8

6.1

11

9

7.1

Lungs - irregular surface throughout

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Right subclavian artery - retro-oesophageal

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Atrium - enlarged

0

0

0.0

0

0

0.0

1

1

0.6

0

0

0.0

Ventricular septal defect

1

1

0.7

0

0

0.0

1

1

0.6

0

0

0.0

Total

54

22

32.6

50

22

31.0

37

19

22.3

41

17

25.5

 


 

Table 11   Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Skull

 

 

 

 

 

 

 

 

 

 

 

 

Nasal - incomplete ossification

14

8

9.2

7

6

4.6

12

6

7.6

21

11

13.8

Frontal - incomplete ossification

3

3

1.7

3

3

2.0

1

1

0.7

3

3

1.8

Frontal - unossified area

4

2

2.9

0

0

0.0

3

3

1.9

0

0

0.0

Frontal - misshapen

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Intraorbital process of frontal - incomplete ossification

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Parietal - incomplete ossification

0

0

0.0

1

1

0.7

0

0

0.0

1

1

0.6

Parietal - unossified area(s)

0

0

0.0

0

0

0.0

0

0

0.0

1

1

0.5

Parietal - absent

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Interparietal - incomplete ossification

7

6

4.2

18

9

11.7

12

8

7.9

2

2

1.6

Interparietal - unossified area(s)

5

5

3.6

0

0

0.0*

0

0

0.0*

1

1

0.5

Interparietal - absent

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Occipital (Supra-occipital) - incomplete ossification

7

5

4.1

17

10

10.5

6

6

4.1

35

14

23.3**

Occipital (Supra-occipital) - unossified area(s)

7

5

4.3

15

10

9.7

6

5

3.6

13

10

8.1

Occipital - absent

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Squamosal - incomplete ossification

6

5

3.5

14

7

8.6

7

7

4.5

8

5

5.2

a


 

Table11(continued)           Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Skull (continued)

 

 

 

 

 

 

 

 

 

 

 

 

Squamosal - unossified area(s)

7

5

5.6

3

3

2.0

1

1

0.7

5

5

3.5

Squamosal - misshapen

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Jugal - incomplete ossification

1

1

0.5

4

3

2.6

2

2

1.4

0

0

0.0

Zygomatic process of maxilla - incomplete ossification

6

4

3.8

6

4

3.9

4

2

2.6

0

0

0.0

Zygomatic process of squamosal - incomplete ossification

0

0

0.0

1

1

0.7

0

0

0.0

0

0

0.0

Premaxilla - incomplete ossification

2

2

1.1

2

1

1.4

0

0

0.0

0

0

0.0

Hyoid - incomplete ossification

18

12

11.1

14

8

9.3

6

5

3.8

1

1

0.6**

Hyoid - not ossified

7

6

4.6

3

3

2.1

4

4

2.5

0

0

0.0

Presphenoid - incomplete ossification

0

0

0.0

0

0

0.0

2

2

1.4

0

0

0.0

Presphenoid - misshapen

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Basisphenoid - incomplete ossification

1

1

0.6

3

3

1.8

0

0

0.0

1

1

0.7

Basisphenoid - misshapen

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

a


 

Table11(continued)           Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Vertebral Column

 

 

 

 

 

 

 

 

 

 

 

 

Odontoid - ossification present

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Ventral arch of vertebra 1 - ossification present

27

17

18.0

44

12

28.9

34

16

22.0

11

5

6.7**

Cervical (neural) arch - incomplete ossification

5

4

2.9

7

5

4.4

1

1

0.7

2

2

1.3

Thoracic centrum - incomplete ossification

0

0

0.0

2

2

1.2

4

4

2.6*

12

7

7.8**

Thoracic centrum - not ossified

1

1

0.6

1

1

0.6

0

0

0.0

1

1

0.7

Thoracic centrum - bipartite ossification

0

0

0.0

0

0

0.0

2

2

1.4

2

1

1.0

Thoracic centrum - dumb-bell-shaped

5

4

2.9

11

10

6.7

17

13

11.1**

22

12

14.3**

Thoracic centrum - asymmetrically ossified

1

1

0.6

0

0

0.0

3

3

1.9

4

4

2.5

Lumbar centrum - absent

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Lumbar centrum - bipartite ossification

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Lumbar centrum - dumb-bell-shaped

0

0

0.0

0

0

0.0

0

0

0.0

1

1

0.5

Lumbar vertebra - absent (arches and centrum)

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Sacral (neural) arch - incomplete ossification

6

6

3.7

12

7

7.5

7

5

4.5

4

3

2.4

Sacral (neural) arch - not ossified

0

0

0.0

0

0

0.0

0

0

0.0

1

1

0.6

Sacral vertebrae - absent (arches and centrum)

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

a


 

Table11(continued)           Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Vertebral Column (continued)

 

 

 

 

 

 

 

 

 

 

 

 

Number of pre-sacral vertebrae = 25/27

0

0

0.0

2

2

1.3

0

0

0.0

2

2

1.2

Caudal vertebrae - less than 4 ossified

25

12

15.8

31

14

19.1

34

17

21.8

79

21

51.4***

Caudal vertebrae - all absent

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Conjoined twin fetuses

1

1

0.6

0

0

0.0

0

0

0.0

0

0

0.0

Ribs

 

 

 

 

 

 

 

 

 

 

 

 

Ossification centre - associated with 7th cervical vertebra

1

1

0.7

0

0

0.0

0

0

0.0

1

1

0.7

Ossification centre - associated with 1st lumbar vertebra

4

1

2.4

3

2

1.8

1

1

0.8

7

5

4.7

One or more ribs - thickened

1

1

1.0

0

0

0.0

0

0

0.0

0

0

0.0

Rib - short

6

2

3.8

0

0

0.0

1

1

0.6

2

2

1.3

Rib - rudimentary

1

1

0.7

0

0

0.0

1

1

0.7

0

0

0.0

Costal cartilage - misaligned

4

4

2.9

3

3

1.7

2

2

1.3

4

4

3.4

Costal cartilage - not fused to sternebra

18

10

12.0

21

12

13.1

16

10

10.2

33

16

23.6

a


 

Table11(continued)           Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Sternebrae

 

 

 

 

 

 

 

 

 

 

 

 

Sternebra - incomplete ossification

2

2

1.2

1

1

0.6

5

5

3.1

8

8

5.3*

Sternebra - not ossified

1

1

0.6

3

1

1.8

1

1

0.7

2

2

1.2

Sternebra - bipartite ossification

1

1

0.6

1

1

0.6

0

0

0.0

2

1

1.4

Sternebra - misaligned

2

2

1.1

0

0

0.0

4

4

2.6

9

6

6.2

Xiphoid cartilage - partially split

2

2

1.4

1

1

0.8

6

5

3.7

9

8

5.9

Pectoral Girdle

 

 

 

 

 

 

 

 

 

 

 

 

Scapula - misshapen

2

2

1.2

2

1

1.0

9

6

5.8

12

7

7.4

Pelvic Girdle

 

 

 

 

 

 

 

 

 

 

 

 

Ischium - incomplete ossification

0

0

0.0

1

1

0.6

1

1

0.7

0

0

0.0

Pubis - not ossified

0

0

0.0

0

0

0.0

1

1

0.7

0

0

0.0

Pubis - incomplete ossification

2

2

1.1

5

4

3.2

3

3

2.0

5

5

3.3

a


 

Table11(continued)           Summary Incidence of Fetal Skeletal Findings

Skeletal Findings

Dose Level (mg/kg bw/day)

0 (Control)

30

175

1000

Number of Fetuses (litters) Examined

154 (24)

155 (24)

155 (24)

148 (24)

NF

NL

%†

NF

NL

%†

NF

NL

%†

NF

NL

%†

Forelimbs

 

 

 

 

 

 

 

 

 

 

 

 

Metacarpal - not ossified

23

11

14.2

42

14

26.2

20

12

13.1

52

18

34.7*

Metacarpal - incomplete ossification

0

0

0.0

2

2

1.4

2

2

1.4

0

0

0.0

Forepaw phalanges - 1 or more - ossified

26

9

17.3

33

11

21.0

36

11

22.0

30

12

20.7

Humerus - incomplete ossification

0

0

0.0

4

3

2.5

0

0

0.0

0

0

0.0

Humerus - hole

0

0

0.0

1

1

0.7

0

0

0.0

0

0

0.0

Humerus - short

2

1

1.2

0

0

0.0

0

0

0.0

0

0

0.0

Hindlimbs

 

 

 

 

 

 

 

 

 

 

 

 

Metatarsal - incomplete ossification

0

0

0.0

0

0

0.0

1

1

0.6

5

2

3.0

Femur - incomplete ossification

0

0

0.0

1

1

0.6

0

0

0.0

0

0

0.0

Total

117

24

75.9

126

24

80.5

122

24

78.5

136

24

91.2**

NOTE: a fetus may appear in more than one category

 

Number of dams with abortions, early deliveries, stillbirths, resorptions, and/or dead foetuses

 

Dose level

0 mg/kg (control)

30 mg/kg

175 mg/kg

1000 mg/kg

Abortions

0

0

0

0

Early deliveries

0

0

0

0

Still births

0

0

0

0

Resorptions/ dead fetuses

4/24

7/24

5/24

9/24

 

 

Pre-and post-implantation (fetus) loss, number and percent

 

Dose level

Number pre-implantation

Number post implantation

Percentage live offspring#

0 mg/kg (control)

332-325=7

325-321=4

13.4/13.5*100=99.26%

30 mg/kg

339-330=9

330-322=8

13.4/13.8*100=97.1%

175 mg/kg

322-316=6

316-309=7

13.5/13.7*100=98.54%

1000 mg/kg

326-319=7

319-306=13

12.8/13.3*100=96.24%

 

 

 

Applicant's summary and conclusion

Conclusions:
The oral administration of 1,1,3,3-tetramethylbutyl peroxyneodecanoate (CAS# 51240-95-0) to pregnant rats by gavage during gestation Days 5 to 19, at dose levels of 30, 175 or 1000 mg/kg bw/day resulted in an adverse effect on body weight gain and food consumption at the high dose level. Although some improvement was evident, cumulative body weight gains for females treated with 1000 mg/kg bw/day remained lower than controls throughout the dosing period with body weight gain adjusted for the contribution of gravid uterus also being markedly lower than controls. Taking into consideration the overall results, the No Observed Adverse Effect Level’ (NOAEL) for the pregnant female was considered to be 175 mg/kg bw/day within the confines of this type of study.
At 1000 mg/kg bw/day, fetal and litter weights were marginally lower than control with skeletal examination identifying a number of treatment-related variants. These observations were, however, considered to be due to maternal toxicity which results in slight reduction in fetal growth rather than an indication of a direct effect of the test item on fetal growth and development. The ‘No Observed Adverse Effect Level’ (NOAEL) for developmental toxicity was therefore considered to be 1000 mg/kg bw/day whilst the ‘No Observed Effect Level’ (NOEL) for developmental toxicity was deemed to be 175 mg/kg bw/day within the confines of this type of study.
Executive summary:

Introduction

The study was performed according to the study plan and was designed to investigate the effects of the test item on embryonic and fetal development following repeated administration by gavage to the pregnant female during gestation including the period of organogenesis.

The study was designed to comply with the following guidelines:

·        OECD Guidelines for Testing of Chemicals, No 414, ‘Prenatal Developmental Toxicity Study’ (adopted 22 January 2001)

Methods

The test item was administered by gavage to three groups each of twenty-four time mated Sprague-Dawley Crl:CD®(SD) IGS BR strain rats, between Days 5 and 19 of gestation inclusive at dose levels 30, 175 or 1000 mg/kg bw/day. A further group of twenty-four time mated females was exposed to the vehicle only (Arachis oil BP) to serve as a control.

Clinical signs, body weight change, food and water consumptions were monitored during the study. 

All females were terminated on Day 20 of gestation and subjected to gross necropsy including examination of the uterine contents. The number of corpora lutea, number, position and type of implantation, placental weights, fetal weight, sex and external and internal macroscopic appearance were recorded. Half of each litter were examined for detailed skeletal development and the remaining half were subjected to detailed visceral examination.

Results…….

Mortality

There were no unscheduled deaths during the study.

Clinical Observations

There were no clinical signs for any of the animals throughout the study.

Body Weight

At all dose levels, females showed a dose-related reduction in group mean body weight gains over Days 5 to 6 of gestation with most animals from the 1000 mg/kg bw/day showing actual body weight losses. Subsequent recovery was evident for females receiving 30 or 175 mg/kg bw/day with periodic body weight gains for these animals remaining comparable with controls from Day 6 of gestation. Females treated with 1000 mg/kg bw/day also showed improvement in body weight performance following the initial affect such that body weight gains over Days 7 to 14 of gestation were comparable with controls; however, further reduction in body weight gain was observed over Days 14 to 17 of gestation resulting in lower cumulative body weight gains for these animals throughout the treatment period. The overall body weight gain for these females was approximately 21% lower than controls with body weight gain adjusted for gravid uterus contribution also being markedly lower than controls. The effect on body weight development for the 1000 mg/kg bw/day females was considered to be of toxicological significance.

Food Consumption

There was marked reduction in food consumption at the start of dosing for females given 1000 mg/kg bw/day. Gradual improvement was apparent, however, dietary intake for these animals remained statistically significantly lower than controls up to Day 17 of gestation. Taken together with the effect on body weight development at this dose level, this observation was considered to be of toxicological significance.

There was no effect of treatment on food intake at 30 or 175 mg/kg bw/day.

Water Consumption

Daily visual inspection of water bottles did not reveal any treatment-related intergroup differences.

Post Mortem Studies

There were no treatment-related macroscopic findings at terminal necropsy.

Litter Data and Litter Placental and Fetal Weights

Treatment with the test item at 30, 175 or 1000 mg/kg bw/day did not result in any treatment-related effects onin uterosurvival. Sex ratios were also similar across all dose groups including controls. At 1000 mg/kg bw/day, group mean fetal weights were marginally lower than controls which resulted in slightly lower litter weight for this dose group. These findings were deemed likely due to maternal toxicity rather than a direct effect of treatment on fetal growth and development. Group mean total placental weight for the dams treated with 1000 mg/kg bw/day was also slightly lower than controls which was also considered likely to be due to maternal toxicity.

Fetal Examination

For all dose groups, there were no statistically significant treatment-related trends in the proportion of fetuses (or litters) with evidence of external or visceral abnormalities. At 1000 mg/kg bw/day, a number of skeletal anomalies achieved statistical significance. These included incomplete ossification of occipital (supra-occipital) region, thoracic centrum and sternbrae, no ossification of metacarpal, and caudal vertebrae - less than 4 ossified. These observations are minor variants and although group mean values were outside the historical background data ranges, they were deemed likely due to a slightly slower fetal growth rate resulting from maternal toxicity rather than an indication of a direct effect of the test item on fetal development. Any other skeletal findings at all dose levels were considered to be within normal biological variation.

Conclusion

The oral administration of 1,1,3,3-tetramethylbutyl peroxyneodecanoate (CAS# 51240-95-0) to pregnant rats by gavage during gestation Days 5 to 19, at dose levels of 30, 175 or 1000 mg/kg bw/day resulted in an adverse effect on body weight gain and food consumption at the high dose level. Although some improvement was evident, cumulative body weight gains for females treated with 1000 mg/kg bw/day remained lower than controls throughout the dosing period with body weight gain adjusted for the contribution of gravid uterus also being markedly lower than controls. Taking into consideration the overall results, the No Observed Adverse Effect Level’ (NOAEL) for the pregnant female was considered to be 175 mg/kg bw/day within the confines of this type of study.

At 1000 mg/kg bw/day, fetal and litter weights were marginally lower than control with skeletal examination identifying a number of treatment-related variants. These observations were, however, considered to be due to maternal toxicity which results in slight reduction in fetal growth rather than an indication of a direct effect of the test item on fetal growth and development. The ‘No Observed Adverse Effect Level’ (NOAEL) for developmental toxicity was therefore considered to be 1000 mg/kg bw/day whilst the ‘No Observed Effect Level’ (NOEL) for developmental toxicity was deemed to be 175 mg/kg bw/day within the confines of this type of study.