Registration Dossier

Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Data waiving:
other justification
Justification for data waiving:
the study does not need to be conducted because a pre-natal developmental toxicity study is available
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In accordance with Column 2 of REACH Annex VIII, the screening study for reproductive/developmental toxicity does not need to be conducted if a pre-natal developmental toxicity study (Annex IX, 8.7.2) is available.
Cross-reference
Reason / purpose:
data waiving: supporting information
Reference
Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 2006-06-06 to 2006-07-14
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study performed according to US FDA guideline ICH S5A and in compliance with GLP with minor deviation: no gravid uterine weighting.
Qualifier:
according to
Guideline:
other: US FDA. Guideline for Industry: detection of toxicity to reproduction for medicinal products, (ICH) S5A; September, 1994.
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Crj: CD(SD)
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC
- Age at study initiation: 65 days at arrival
- Weight at study initiation: 221-257 at study assignment (GD0)
- Fasting period before study:
- Housing: Rats were individually housed in stainless steel, wire-bottomed cages, except during the cohabitation period. During cohabitation, each pair of male and female rats was housed in the male rat’s cage.
- Diet (e.g. ad libitum): ad libitum access to Certified Rodent Diet® #5002 (PMI® Nutrition International, St. Louis, MO) in individual feeders. Not contaminated.
- Water (e.g. ad libitum): Local water that had been processed by passage through a reverse osmosis membrane (R.O. water) was available to the rats ad libitum from an automatic watering access system and/or individual water bottles attached to the cages. Chlorine was added to the processed water as a bacteriostat.
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18°C to 26°C
- Humidity (%): 30% to 70%
- Air changes (per hr): minimum of ten changes per hour of 100% fresh air that had been passed through 99.97% HEPA filters.
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 2006-06-20 To: 2006-07-14
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The Testing Facility prepared suspensions of the test article on a weekly basis. These formulated suspensions were stored at room temperature and were stirred continuously during administration to the animals, sampling and aliquotting.
The dosage volume was adjusted daily on the basis of the individual body weights recorded before dosage. The rats were administered the test article and/or the vehicle at approximately the same time each day. Prepared formulations were stirred continuously during administration of the control and test article formulations.

VEHICLE
- Justification for use and choice of vehicle (if other than water): suitable vehicle
- Concentration in vehicle: 0, 4, 16 or 64 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg bw
- Lot/batch no. (if required): 7371H
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
- Concentrations: Test article samples prepared on June 29 and July 13, 2006, which were used for dosing, were within acceptable limits of ±15% error.
- Homogeneity: Homogeneity was determined for all dose formulation concentration levels. Mean concentration results from samples taken from the top, middle, and bottom of the formulations were calculated. Homogeneity was calculated by determining the percent relative standard deviation (RSD) of the three mean values. All of the results were within the acceptable range of ≤5% RSD. The values obtained were 0.4%, 1.2%, and 0.3% RSD for the 4 mg/mL, 16 mg/mL and 64 mg/mL formulations, respectively.
- Stability: The stability was evaluated for the 64 mg/mL dose formulation concentration level. Initial stability samples were analysed on June 30, 2006. Final stability samples were stored at 22±5°C and analysed on July 14, 2006, resulting in a 14-day stability period. The final stability sample results were compared with the initial results and expressed as percent errors. All of the results were within the acceptable range of ±10% error.
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Length of cohabitation: maximum of 5 days
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: vaginal plug or sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
From GD7 through GD20
Frequency of treatment:
Once daily
Duration of test:
Up to sacrifice on GD21
Dose / conc.:
40 mg/kg bw/day (nominal)
Dose / conc.:
160 mg/kg bw/day (nominal)
Dose / conc.:
640 mg/kg bw/day (nominal)
No. of animals per sex per dose:
25
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Dosages were selected on the basis of findings from a dosage-range study (Protocol TIF00021) in which 4-tBCHA dosages of 37.5, 50, 150 and 300 mg/kg/day were administered to pregnant rats once daily for 14 consecutive days (DGs 7 through 20). No mortality occurred at dosages as high as 300 mg/kg/day. At 50 mg/kg/day and higher, slight excessive salivation and urine-stained abdominal fur were observed. In the 50, 150 and 300 mg/kg/day dosage groups, increased numbers of rats lost weight after the first dosage (DGs 7 to 8), as compared with the vehicle control group incidence. A
dosage-dependent reduction in maternal body weight gain was observed after the second dosage (DGs 8 to 9). Body weights and body weight gains were comparable for the entire dosage period between the 4-tBCHA and vehicle control dosage groups. Absolute and relative feed values were reduced in the 50 and 300 mg/kg/day dosage groups for the first three days of treatment, as compared to the vehicle control group value. One rat in the 150 mg/kg/day dosage group had a very high feed consumption value during this period, which, when removed, resulted in a dose-dependent reduction in feed consumption for the first three days of treatment. Absolute and relative feed consumption values were comparable between the 4-tBCHA and control groups for the entire dosage period. Dosages of 4-tBCHA as high as 300 mg/kg/day did not adversely affect Caesarean-sectioning, litter, or foetal gross external evaluations. Because 300 mg/kg/day, the highest dosage of 4-tBCHA tested in the dosage-range finding study, produced only transient reductions in maternal body weight gain and feed
consumption values, a higher dosage, 640 mg/kg/day, was selected as the high dosage for the full study. This dosage was expected to reduce maternal body weight and feed consumption for the entire dosage period.
- Rationale for animal assignment (if not random): random
Maternal examinations:
VIABILITY OBSERVATIONS: Yes
- Time schedule: twice daily

CLINICAL OBSERVATIONS: Yes
- Time schedule: at least weekly during the acclimation period and on DG0
The rats were also examined for clinical observations, abortions, premature deliveries and deaths before and between one and two hours after dosage and once daily during the postdosage period.

BODY WEIGHT: Yes
- Time schedule for examinations: at least weekly during the acclimation period, on DG 0 and daily during the dosage and postdosage periods

FOOD CONSUMPTION: Yes
- Time schedule: Feed consumption values were recorded on DGs 0, 7, 10, 12, 15, 18, 20 and 21.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: gross lesions. Caesarean-sectioned and a gross necropsy of the thoracic, abdominal and pelvic viscera was performed.
The 640 mg/kg/day dosage group rat that was sacrificed on DG 20 was examined for gross lesions, pregnancy status and uterine contents. The lungs, trachea and oesophagus were perfused with neutral buffered 10% formalin; these perfused tissues, along with the heart, liver, kidneys, stomach and spleen were retained in neutral buffered 10% formalin for possible histological evaluation.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
Statistics:
Clinical observations and other proportional data were analysed using the Variance Test for Homogeneity of the Binomial Distribution.
Continuous data (e.g., body weights, body weight changes, feed consumption values, organ weights and litter averages for percent male foetuses, percent resorbed conceptuses, foetal body weights and foetal anomaly data) were analyzed using Bartlett’s Test of Homogeneity of Variances and the Analysis of Variance, when appropriate [i.e., Bartlett’s Test was not significant (p>0.001)]. If the Analysis of Variance was significant (p≤0.05), Dunnett’s Test was used to identify the statistical significance of the individual groups. If the Analysis of Variance was not appropriate [i.e., Bartlett’s Test was significant (p≤0.001)], the Kruskal-Wallis Test was used, when less than or equal to 75% ties were present. In cases where the Kruskal-Wallis Test was statistically significant (p≤0.05), Dunn’s Method of Multiple Comparisons was used to identify the statistical significance of the individual groups. If there were greater than 75% ties,
Fisher’s Exact Test was used to analyse the data. Count data were evaluated using the procedures described above for the Kruskal-Wallis Test.
Indices:
None
Historical control data:
Not reported
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
The 160 and 640 mg/kg bw/day dosages of 4-tBCHA were associated with dosage-dependent, statistically significant increases (p≤0.05 or p≤0.01) in the incidences of excess salivation (total) and slight excess salivation, as compared with the vehicle control group values. The 640 mg/kg bw/day dosage of 4-tBCHA also resulted in statistically significant increases (p≤0.01) in the incidences of moderate excess salivation, red perioral substance and sparse hair coat on the limbs and increased incidences of extreme excess salivation, ungroomed coat, sparse hair coat (total incidence for underside and limbs) and localized alopecia of the limbs and/or neck. Excess salivation was observed after dosing, approximately one to two hours following intubation. Additional clinical signs observed only in the 640 mg/kg bw/day dosage group rat that was sacrificed on DG 20 for humane reasons included extreme excess salivation, scant feces, decreased motor activity, ptosis, coldness to touch and apparent dehydration.
Mortality:
mortality observed, treatment-related
Description (incidence):
One rat in the 640 mg/kg bw/day dosage group was sacrificed on day 20 of gestation (DG 20) because it had adverse clinical observations. These observations were considered to be effects of treatment with 4-tert butylcyclohexyl acetate (4-tBCHA) because they occurred at the highest dosage level tested and some of these adverse clinical observations also occurred in surviving rats in this dosage group.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
The 640 mg/kg bw/day dosage group had significantly reduced (p≤0.05 or p≤0.01) average maternal body weights on DGs 9 through 21 (with the exception of DG 11, when the reduction in body weight gain was not significantly less than the vehicle control group value). These values reflected a significant reduction (p≤0.01) in maternal body weight gain for the entire treatment period (calculated as DGs 7 to 21) to 32% of the vehicle control group value and weight losses or reduced weight gains within this period, as described in the following information. Significant body weight losses (p≤0.01) occurred
on DGs 7 to 8 and 8 to 9, after the first two 640 mg/kg bw/day dosages of 4-tBCHA were administered, and significant reductions (p≤0.01) in body weight gains occurred on DGs 15 to 18 and 18 to 21, as compared with the vehicle control group values. Maternal body weight gains on DGs 7 to 10 and for the entire gestation period (DGs 0 to 21) were also significantly reduced (p≤0.01), as compared with the vehicle control group value. Dosages of 4-tBCHA as high as 160 mg/kg bw/day did not affect maternal body weight gains or body weights. All values in the 40 and 160 mg/kg/day dosage groups were comparable to and did not significantly differ from those of the vehicle control group. Average body weight gains in the 40 and 160 mg/kg/day dosage groups were 103% and 102% of the vehicle control group value, respectively, on DGs 7 to 21.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Absolute and relative feed consumption values were significantly reduced (p≤0.01) for the entire dosage period (calculated as DGs 7 to 21) and at all intervals within this dosage period in the 640 mg/kg bw/day dosage group, as compared with the vehicle control group values. Absolute feed consumption values in the 40, 160 and 640 mg/kg/day dosage groups were 100%, 102% and 71% of the vehicle control group value, respectively, on DGs 7 to 21. Relative feed consumption values in these same respective dosage groups were 100%, 102% and 74% of the vehicle control group value on DGs 7 to 21. Absolute and relative feed consumption values were unaffected by dosages of 4-tBCHA as high as 160 mg/kg bw/day.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
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:
not examined
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
The only necropsy observations associated with treatment with 4-tBCHA were those observed in the 640 mg/kg bw/day dosage group rat that was sacrificed on DG 20 (distention of the stomach with gas and yellow fluid and a litter of 17 dead foetuses).
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed
Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
Pregnancy occurred in 24 or 25 rats in each dosage group. As a result of the mortality in the 640 mg/kg bw/day dosage group, Caesarean-sectioning observations on DG 21 were based on 24, 24, 25 and 24 pregnant rats with one or more live foetuses in the four respective dosage groups.
Other effects:
no effects observed
Details on maternal toxic effects:
The litter averages for corpora lutea, implantations, litter sizes, live foetuses, early and late resorptions, the percentage of resorbed conceptuses and the percentage of live male foetuses were comparable among the four dosage groups and did not significantly differ. No dam had a litter consisting of only resorbed conceptuses, and there were no dead foetuses. All placentae appeared normal.
Key result
Dose descriptor:
NOAEL
Effect level:
160 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
clinical signs
Key result
Dose descriptor:
LOAEL
Effect level:
> 160 - <= 640 mg/kg bw/day (nominal)
Based on:
test mat.
Basis for effect level:
clinical signs
mortality
body weight and weight gain
food consumption and compound intake
Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
Foetal body weights (combined sexes and male and female) were significantly reduced (p≤0.01) in the 640 mg/kg bw/day dosage group, as compared with the vehicle control group values. The average value for combined male and female foetal body weights in the 640 mg/kg bw/day dosage group was approximately 11% less than the vehicle control group value.
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
no effects observed
External malformations:
no effects observed
Description (incidence and severity):
Foetal gross external alterations were limited to a single occurrence of an absent tail in the 160 mg/kg bw/day dosage group. Skeletal examination of this foetus confirmed the gross absence of the tail, which was evident as the presence of fewer than normal ossified lumbar, sacral and caudal vertebrae (5, 1 and 0, respectively; usually there are 6, 3 and 7 ossified lumbar, sacral and caudal vertebrae, respectively). No other gross external foetal alterations occurred.
Skeletal malformations:
effects observed, treatment-related
Description (incidence and severity):
- Malformations: Skeletal examination of the externally malformed foetus with no tail in the 160 mg/kg bw/day dosage group revealed expected absence of lumbar, sacral and caudal vertebrae, as previously described. No other alterations occurred in this foetus. Duplication of the manubrium and the 1st through 3rd sternal centra occurred in one foetus in the 40 mg/kg bw/day dosage group. No other alterations occurred in this foetus.
- Variations: One or both of the arches in the 6th cervical vertebra had the appearance of an arch in the 7th cervical vertebra in 1, 1, 1 and 4 foetuses from 1, 1,1 and 2 litters in the 0 (Vehicle), 40, 160 and 640 mg/kg bw/day dosage groups, respectively. No other alterations occurred in these foetuses. A bifid centrum in the 11th, 12th or 13th thoracic vertebra occurred in 0, 2, 2 and 3 foetuses from 0, 2, 2 and 3 litters in the four respective dosage groups. No additional alterations occurred in these foetuses. Presence of a cervical rib at the 7th cervical vertebra, a common variation in this strain of rat, was observed in 1, 2 and 2 foetuses from 1, 2 and 2 litters in the 0 (Vehicle), 40 and 160 mg/kg bw/day dosage groups, respectively. One foetus in the vehicle control group also had a short 13th rib. No other alterations occurred in any of these foetuses. A short 13th rib occurred in one control group foetus and in two foetuses from a 640 mg/kg bw/day dosage group litter, respectively. One vehicle control group foetus also had a rib present on the 7th cervical vertebra, as previously described. No other alterations occurred in the foetuses in the 640 mg/kg bw/day dosage group. No other skeletal variations occurred.
The average numbers of ossified caudal vertebrae, forelimb phalanges and hindlimb metatarsals and phalanges were significantly reduced (p≤0.05 or p≤0.01) in the 640 mg/kg bw/day dosage group, as compared with the vehicle control group values. The average value for ossified forelimb phalanges (7.76) was within the historical range of the Testing Facility; however, the litter averages for ossified caudal vertebrae (6.58), hindlimb metatarsals (4.48) and hindlimb phalanges (5.40) were below the historical range for the Testing Facility. In 50 studies conducted at the Testing Facility between June 2004 and June 2006 (1113 control group litters; 8312 foetuses), the litter averages were 7.47 per foetus (range 6.69-8.23 per study) for caudal vertebrae, 4.84 per foetus (range 4.67-5.00 per study) for metatarsals, and 6.23 per foetus (range 5.54-7.75 per study) for hindlimb phalanges. There were no other statistically significant or biologically important differences among the four dosage groups in the average numbers of ossification sites per foetus for the hyoid, vertebrae (cervical, thoracic, lumbar and sacral), ribs, sternum (manubrium, sternal centers and xiphoid), forelimbs (carpals and metacarpals) or hindlimbs (tarsals).
Visceral malformations:
effects observed, treatment-related
Description (incidence and severity):
- Malformations: 2 fetuses from two litters in the 40 mg/kg/day dosage groups, respectively, had malpositioned testes. No other alterations occurred in any of these fetuses. No other soft tissue malformations occurred.
- Variations: One fetus in each of the 40 and 640 mg/kg/day dosage groups had a folded retina in the right eye, a finding that is usually an artifact of fixation and/or sectioning. No other alterations occurred in these fetuses. The umbilical artery descended to the left of the urinary bladder in 3, 1 and 1 fetuses from 3, 1 and 1 litter in the 0 (Vehicle), 40 and 160 mg/kg/day dosage groups, respectively. No other alterations occurred in these fetuses. Slight or moderate dilation of the pelvis of one or both kidneys, a reversible developmental delay, occurred in 1, 2, 0 and 8 fetuses from 1, 2, 0 and 2 litters in the four respective dosage groups. Although the fetal incidence of moderate enlargement of the pelvis of both kidneys was significantly increased (p≤0.01) in the 640 mg/kg/day dosage group, as compared to the vehicle control group value, the litter incidence (one), the more relevant parameter(1), was not. One vehicle control group fetus also had moderate dilation of the renal pelvis in the right kidney. No other alterations occurred in any of these fetuses. In 50 studies conducted at the Testing Facility between June 2004 and June 2006 (1112 control group litters; 7805 fetuses), 10 litters (0.9%) and 11 fetuses (0.14%) had slight dilation of the pelvis of one or both kidneys, with a maximum of 3 (13.6%) litters and 4 fetuses (2.6%) per study, and 3 litters (0.27%) and 3 fetuses (0.04%) had moderate dilation of the pelvis of one or both kidneys, with a maximum of 1 (4.5%) litter and 1 fetus (0.7%) per study.
Other effects:
no effects observed
Key result
Dose descriptor:
NOAEL
Effect level:
160 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no adverse effect observed
Key result
Dose descriptor:
LOAEL
Effect level:
> 160 - <= 640 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
fetal/pup body weight changes
skeletal malformations
visceral malformations
Remarks on result:
other: maternally toxic dosage
Key result
Abnormalities:
effects observed, treatment-related
Description (incidence and severity):
Only occurring at maternally toxic dosage
Key result
Developmental effects observed:
yes
Lowest effective dose / conc.:
640 mg/kg bw/day (nominal)
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
no
Relevant for humans:
no

None

Conclusions:
Maternal & developmental NOAEL = 160 mg/kg bw/d. The test material is not selectively toxic to embryo-foetal developmental and did not result in teratogenicity, even at maternally toxic dosage.
Executive summary:

A pre-natal / developmental toxicity study was conducted according to the US FDA guideline ICH S5A and in compliance with GLP. The test material or the vehicle, corn oil, was administered orally (via gavage) once daily on days 7 through 20 of presumed gestation (GD 7 through 20) at dosage of 0, 40, 160 and 640 mg/kg bw/d to Crl:CD(SD) rats (25/group). GD 0 was the day when sperm were observed in a smear of the vaginal contents or a plug was observed in situ. The dosage volume (10 mL/kg) was adjusted daily on the basis of the individual body weights recorded before intubation.

All rats were examined for clinical observations of effects of the test article, abortions, premature deliveries and deaths before dosage, between one and two hours after dosage and once daily during the post-dosage period. Body weights were recorded on GD 0 and daily during the dosage and post-dosage periods. Feed consumption values were recorded on GDs 0, 7, 10, 12, 15, 18, 20 and 21. All surviving rats were sacrificed on GD 21, Caesarean-sectioned and a gross necropsy of the thoracic, abdominal and pelvic viscera performed. All foetuses were weighed and examined for sex and gross external alterations. Approximately ½ of the foetuses in each litter were evaluated for soft tissue or skeletal alterations.

One rat in the 640 mg/kg bw/day dosage group had severe adverse clinical observations attributable to the test material and was sacrificed on GD 20. All other rats in this study survived to scheduled sacrifice.

The 160 and 640 mg/kg bw/day dosages were associated with dosage-dependent, statistically significant increases in the incidences of excess salivation (total) and slight excess salivation, as compared with the vehicle control group values. The 640 mg/kg bw/day dosage also resulted in statistically significant increases in the incidences of moderate excess salivation, red perioral substance and sparse hair coat on the limbs and increased incidences of extreme excess salivation, ungroomed coat, sparse hair coat and localized alopecia of the limbs and/or neck. Excess salivation was observed after dosing, approximately one to two hours following intubation. Additional clinical signs observed only in the 640 mg/kg bw/day dosage group rat that was sacrificed on GD 20 included extreme excess salivation, scant feces, decreased motor activity, ptosis, coldness to touch and apparent dehydration. This rat also had the only necropsy observations associated with treatment with the test material, distension of the stomach with gas and yellow fluid and a litter of 17 dead foetuses (the dead foetuses were otherwise normal for their developmental ages).

Maternal body weights were significantly reduced in the 640 mg/kg bw/day dosage group on GDs 9 through 21, with the exception of GD 11, as compared with the vehicle control group values. These reductions in maternal body weight reflected significantly reduced body weight gains for the entire treatment period (calculated as GDs 7 to 21), significant weight losses on GDs 7 to 8 and 8 to 9, after the first two dosages were administered, and significantly reduced body weight gains on GDs 15 to 18 and 18 to 21, as compared with the vehicle control group values.

The 640 mg/kg bw/day dosage group also had significantly reduced absolute and relative feed consumption values for the entire dosage period (calculated as GDs 7 to 21) and at all calculated intervals within this dosage period, as compared with the vehicle control group values.

Pregnancy occurred in 24 to 25 rats in each dosage group. Foetal body weights were significantly reduced at the 640 mg/kg bw/day dosage group, as compared with the vehicle control group values. The average value for combined male and female fetal body weights in the 640 mg/kg bw/day dosage group was approximately 11% less than the vehicle control group value.

No other Caesarean-sectioning or litter parameters were affected by dosages of test material as high as 640 mg/kg bw/day. The litter averages for corpora lutea, implantations, litter sizes, live foetuses, early and late resorptions, the percentage of resorbed conceptuses and the percentage of live male foetuses were comparable among the four dosage groups and did not significantly differ. No dam had a litter consisting of only resorbed conceptuses, and there were no dead foetuses. All placentae appeared normal.

The 640 mg/kg bw/day dosage was associated with transient delays in fetal development including statistically significant increases in the foetal (but not the litter) incidences of moderate enlargement of the renal pelvis of one or both kidneys and reversible delays in ossification of the caudal vertebrae, fore- and hind-limb phalanges and hind-limb metarsals. The delays in foetal development were considered to be associated with the significant reductions in foetal body weight that also occurred at the 640 mg/kg bw/day dosage level and are frequent observations at dosages that produced reductions in maternal body weight gain and feed consumption, as occurred in this study.

On the basis of these data, the maternal NOAEL is 160 mg/kg bw/d. The only observation associated with treatment with the test material at this dose-level was moderate excess salivation occurring once in each of two rats. This finding is a common response to a strong tasting substance and was therefore not considered as adverse. The 640 mg/kg bw/d dose-level was associated with body weight losses, reduced body weight gains and feed consumption values. One female in this dose group was sacrificed due to severe adverse clinical observation. It is unclear whether this death, occurring in a single animal, should be considered as an adverse effect of the test substance.

The developmental NOAEL is also 160 mg/kg bw/d. Transient retardations in foetal development associated with 640 mg/kg bw/d dosage included a significant reduction in foetal body weight and associated significant increases in moderate dilation of the renal pelvis and delayed ossification of the caudal vertebrae, fore- and hind-limb phalanges and hind-limb metatarsals.

Based on the results of this study, 4 -tert-butylcyclohexyl acetate is not selectively toxic to embryo-foetal developmental and did not result in teratogenicity, even at maternally toxic dosage.

This study is considered as acceptable and satisfies the requirement for developmental toxicity / teratogenicity endpoint.

Data source

Materials and methods

Results and discussion

Overall reproductive toxicity

Reproductive effects observed:
not specified

Applicant's summary and conclusion