Ethanone, 2,2-dichloro-1-(2,3-dihydro-3-methyl-4H-1,4-benzoxazin-4-yl)-

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records

Reference

Endpoint:

two-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 January 1990 to 04 January 1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study compliant with test guidelines of the time. However, current guidelines for two-generation reproduction toxicity studies require additional endpoints. Available as unpublished report, fully adequate for assessment.

Qualifier:

according to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Version / remarks:

1983 (current guideline adopted 2001)

Deviations:

yes

Remarks:

(does not meet current guideline specification)

Qualifier:

according to guideline

Guideline:

EPA OPP 83-4 (Reproduction and Fertility Effects)

Version / remarks:

1982 (current guideline adopted 1998)

Deviations:

yes

Remarks:

(does not meet current guideline specification)

Qualifier:

according to guideline

Guideline:

other: MAFF Japan, Testing Guidelines for Toxicity Studies, No. 4200 (1985)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: Canada Health Protection Branch: Guidelines for Pesticide Toxicology Data Requirements (1981)

Deviations:

not specified

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: Sprague Dawley Crl:CD(SD)BR
- Age at study initiation: P generation approximately 6 weeks old
- Weight at study initiation: P generation males: 174-232 g; females: 143-175 g
- Housing: Individual in solid floor macrolone cages with stainless steel lids except during mating (one male with one female) and during lactation (one female with litter). Autoclaved sawdust bedding.
- Diet: Ssniff R10 powdered diet ad libitum
- Water: Tap water in plastic bottles ad libitum
- Acclimation period: P generation 8 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-25°C
- Humidity: 30-70%
- Air changes (per hour): Not reported
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 18 January 1990 To: 04 January 1991

Route of administration:

oral: feed

Vehicle:

other: diet

Details on exposure:

DIET PREPARATION
- Frequency of preparation of diet: Monthly
- Mixing appropriate amounts with diet: The particle size of the test substance was reduced and standardised prior to use using a centrifugal laboratory mill. It was then admixed to the powdered diet in several steps (e.g. 1000 g and 10 kg pre-mixtures and 50 kg final mixture)
- Storage temperature of food: room temperature control and 50, 500 and 1000 ppm dose levels, -20°C for 10 ppm level

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: Maximum of 21 days
- Proof of pregnancy: vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy
- After 2 weeks of unsuccessful pairing replacement of first male by another male with proven fertility.
- Further matings after two unsuccessful attempts: no
- After successful mating each pregnant female was caged: Individually

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples from each batch of test diet prepared, together with a reference sample of control diet, were analysed for achieved concentration and homogeneity. The stability of dietary preparations had already been confirmed in earlier studies.

After overcoming initial homogeneity problems, the dietary preparations were determined to be homogeneous and close to nominal concentrations and stable for the period of use.

Duration of treatment / exposure:

P animals: For 14 weeks premating, up to 21 days mating, during pregnancy until weaning
F1 animals: For 14 weeks after weaning/premating, up to 21 days mating, during pregnancy until weaning

Frequency of treatment:

Continuous

Details on study schedule:

- Pre-mating period P Generation: 14 weeks
- Selection of F parents from F1 generation at 21 days of age
- F1 parental animals not mated until 14 weeks after weaning

Remarks:

Doses / Concentrations:
0, 10, 50, 500 and 1000 ppm
Basis:
nominal in diet

No. of animals per sex per dose:

25

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: On the basis of results from a dose-ranging reproduction study in the rat (Ciba-Geigy study number 89 1187, HLD project number 380-153).

Positive control:

No

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: Parental animals once weekly during pre-mating and mating periods and prior to terminal kill. Females were additionally weighed on days 0, 7, 14 and 20 post coitum and on days 1, 4, 7, 14 and 21 post partum.

FOOD CONSUMPTION:
- Time schedule for examinations: Parental animals twice per week during pre-mating period. Additionally food consumption for females was determined for days 0-3, 3-7, 7-10, 10-14, 14-20 post coitum and days 1-4, 4-7, 7-10, 10-12, 12-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20 and 20-21 post partum (calculated as mean daily food consumption/measurement period).
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes

OTHER:
- Date of mating
- Date of parturition
- Duration of gestation
- Abnormalities of nesting or nursing behaviour

Oestrous cyclicity (parental animals):

Not examined

Sperm parameters (parental animals):

Not examined

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: Yes to 8 pups/litter (4/sex where possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
- F1 and F2 offspring: number and sex of pups, live births, postnatal mortality, clinical condition, body weight, pinna unfolding, tooth eruption, eye opening, pupillary reflex and auditory response

GROSS EXAMINATION OF DEAD PUPS:
- yes, for external and visceral abnormalities

Postmortem examinations (parental animals):

SACRIFICE
- Males: After the last litter of each generation was weaned.
- Females: After the lactation period or approximately day 26 post-coitum.

GROSS NECROPSY: Yes
- The uteri of apparently non-pregnant females were immersed in 10% ammonium sulphide to reveal evidence of implantations.
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

ORGAN WEIGHTS: Yes (all parental animals)
- organs weighed: epididymides, kidneys, liver, testes

HISTOPATHOLOGY: Yes
- Tissues examined (control and high dose animals only): Bile duct, cervix, coagulating gland, epididymides, kidneys, liver, ovaries, pituitary, prostate, seminal vesicles, stomach, testes, uterus, vagina, any macroscopically abnormal tissue

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring not selected as parental animals and all F2 offspring were sacrificed at 21 days of age.

GROSS NECROPSY
- External and internal examinations including the cervical, thoracic, and abdominal viscera.

HISTOPATHOLOGY / ORGAN WEIGTHS: No

Statistics:

Statistical analyses used the SAS software package release 6.03.
Analysis of variance with one factor treatment followed by the Student-Newman-Keuls test for multiple group comparisons: body weight, body weight gain, litter weight, organ weights, food consumption.
Analysis of variance with one factor treatment based on taking the ranks of the variables and followed by the Student-Newman-Keuls test for multiple group comparisons: mating performance, duration of gestation, mean pup weight, pup number, live birth index, viability indices, weaning index, pinna unfolding, hair growth, incisor eruption, eye opening.

Reproductive indices:

For both generations the parental reproductive performance was assessed and the following calculated: mating performance, insemination index, fecundity index, fertility index, gestation index

Offspring viability indices:

Live birth index, pup viability index, weaning index and sex ratio.

Clinical signs:

no effects observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Tables 1 & 2

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Tables 1 & 2

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Test substance intake: Table 3

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

BODY WEIGHT (PARENTAL ANIMALS):
P generation: Body weights of males and females reduced in a dose dependent manner at dose levels of 500 ppm and 1000 ppm during the premating phase. Body weights of females during gestation and lactation was generally similar in all groups.
F1 generation: Decreased weaning weights on day 21 post-partum resulted in lower initial F1 parental body weights at 500 and 1000 ppm. Thereafter during the premating, gestation and lactation periods body weights at 500 and 1000 ppm were dose-dependently decreased.

FOOD CONSUMPTION (PARENTAL ANIMALS):
P generation: There was a marginal reduction in food consumption for males at 1000 ppm during the premating phase. For females in all groups, food consumption was similar during the premating, gestation and lactation periods.
F1 generation: Food consumption was slightly reduced at 1000 ppm for males and females during the premating phase and for females during gestation and lactation.

TEST SUBSTANCE INTAKE (PARENTAL ANIMALS):
Dietary concentrations of 10, 50, 500 and 1000 ppm are calculated to be equivalent to 0.8, 4, 40 and 80 mg/kg bw/day respectively based on food intake and body weight during the pre-mating periods.

Dose descriptor:

NOAEL

Remarks:

fertility and reproductive performance

Effect level:

1 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested equivalent to 80 mg/kg bw/day

Dose descriptor:

NOAEL

Remarks:

toxicity

Effect level:

50 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: equivalent to 4 mg/kg bw/day. Reduced parental body weight and food consumption, reduced pup weight at weaning, at higher doses.

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Table 4

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

BODY WEIGHT (OFFSPRING):
F1a: Mean pup weights at 1000 ppm were significantly reduced on day 14 and mean pup weights at 500 and 1000 ppm were reduced on day 21.
F2a: Mean pup weights at 1000 ppm were significantly reduced on day 21.

PHYSICAL & FUNCTIONAL DEVELOPMENT (OFFSPRING):
There were no treatment-related effects on the physical development (incisor eruption, pinna unfolding, eye opening) of the F1a of F2a pups or on the outcome of the functional tests (pupillary reflex, auditory response) on either generation.

Dose descriptor:

NOAEL

Remarks:

fertility and reproductive performance

Generation:

F1

Effect level:

1 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested equivalent to 80 mg/kg bw/day

Dose descriptor:

NOAEL

Remarks:

toxicity

Generation:

F1

Effect level:

50 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: equivalent to 4 mg/kg bw/day. Reduced parental body weight and food consumption, reduced pup weight at weaning, at higher doses.

Reproductive effects observed:

not specified

Table 1: Intergroup comparison of mean body weight change (g) prior to and during mating

	Dietary concentration of CGA154281 (ppm)
	Males					Females
	0	10	50	500	1000	0	10	50	500	1000
P generation
Days 1-99	307.9	292.5	298.3	277.7*	268.0**	115.2	109.5	108.6	104.2*	94.7**
F1 generation
Days 1-99	401.6	404.2	399.8	369.5	352.9**	193.6	190.1	182.5	179.5	168.8**
* Statistically significant difference from control group mean, p<0.05 ** Statistically significant difference from control group mean, p<0.01

 

Table 2: Intergroup comparison of female body weight change (g) during pregnancy and lactation

 

Body Weight Change	Dietary concentration of CGA154281 (ppm)
P Generation	0	10	50	500	1000
Gestation days 0-20	106.20	111.47	104.51	108.29	108.88
Lactation days 1-21	24.69	30.59	19.70	25.77	40.07*
F1 Generation
Gestation days 0-20	117.01	114.10	110.48	105.10*	99.63**
Lactation days 1-21	28.41	42.93**	30.73	37.00	40.88*

P<0.05 * difference from control statistically significant

Table 3: Overall mean dose received (mg/kg/day)

Generation	Sex	Dietary concentration of CGA154281 (ppm)
		10	50	500	1000
P Parents	Males	0.66	3.44	33.7	66.6
	Females	0.79	3.99	39.9	79.7
	Mean	0.73	3.72	36.8	73.2
F1 Parents	Males	0.80	4.07	44.0	86.4
	Females	0.89	4.42	47.6	90.5
	Mean	0.85	4.25	45.8	88.5
P + F1 Parents	Mean	0.79	3.99	41.3	80.1

 

Table 4: Pup body weights (g)

 

Pup body weight (g)	Dietary concentration of CGA154281 (ppm)
F1a	0	10	50	500	1000
day 1 post partum	6.3	6.2	6.2	6.1	6.0
day 4 post partum	8.2	7.9	8.2	7.7	7.5
day 7 post partum	11.9	11.3	11.7	10.7	10.7
day 14 post partum	24.4	23.5	23.3	22.3	21.8*
day 21 post partum	40.9	39.6	38.4	36.3*	35.8*
F2a
day 1 post partum	6.2	5.8	6.0	5.8	5.8
day 4 post partum	7.9	7.6	8.3	7.3	7.6
day 7 post partum	11.8	11.7	12.5	11.1	11.6
day 14 post partum	25.2	24.7	25.5	23.4	23.0
day 21 post partum	42.4	41.2	41.8	40.1	37.4*

P<0.05 * difference from control statistically significant by analysis of variance followed by Student-Newman-Keuls test

Conclusions:

Dietary administration of 500 or 1000 ppm CGA154281 over two generations resulted in lower body weights of the adult animals during the pre-mating period and lower body weights of the pups at weaning. There was no effect of CGA1545281 on fertility or reproductive performance in either generation and no effect on the number and viability of the pups born.
The NOAEL for toxicity was 50 ppm, corresponding to a mean daily intake of 4 mg/kg bw/day. The NOAEL for fertility and general reproductive performance was 1000 ppm corresponding to a mean daily intake of 80 mg/kg bw/day.

Executive summary:

Groups of 25 male and 25 female Sprague-Dawley rats were given CGA154281 in the diet at nominal concentrations of 0, 10, 50, 500, and 1000 ppm continuously over two generations from the start of treatment until necropsy. After a pre-mating period, the P parental animals were mated and allowed to litter and to rear the F1a pups to weaning. After a 14 week post weaning maturation period the selected F1 parental animals were mated, allowed to litter and to rear the F2a pups to weaning. At 500 and 1000 ppm, effects in the P and Fl parental animals included reduced body weight and food consumption. For pups, mean body weight was significantly reduced on day 21 for both F1a and F2a pups at 1000 ppm and for F1a pups at 500 ppm. There were no adverse effects of 10 or 50 ppm CGA154281. There was no effect on fertility or general reproductive performance in either of the two generations at any dietary concentration of CGA154281 in this study.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

80 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

One reliable, GLP- and guideline-conform multi-generation study available demonstrating no effect on fertility or on general reproductive performance.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

The reproductive toxicity of benoxacor has been evaluated in a two-generation (one litter per generation) study in the rat in a key guideline study (OECD 416, 1983) conducted to GLP. This study was preceded by a dose range-finding study although no details are available.

For the two-generation study, groups of 25 male and 25 female rats were fed benoxacor continuously in the diet at nominal concentrations of 0, 10, 50, 500 or 1000 ppm. After a pre-mating period, the P parental animals were mated and allowed to litter and to rear the F1a pups to weaning. After a 14 week post weaning maturation period the selected F1 parental animals were mated and allowed to litter and to rear the F2a pups to weaning.

At 500 and 1000 ppm, effects in the P and Fl parental animals included reduced body weight and food consumption. For pups, mean body weight was significantly reduced on day 21 for both F1a and F2a pups at 1000 ppm and for F1a pups at 500 ppm. There were no adverse effects of 10 or 50 ppm benoxacor. There was no effect on fertility or general reproductive performance in either of the two generations at any dietary concentration of benoxacor. The NOAEL for toxicity was 50 ppm, corresponding to a mean daily intake of 4 mg/kg bw/day. The NOAEL for fertility and general reproductive performance was 1000 ppm corresponding to a mean daily intake of 80 mg/kg bw/day.

The study was not conducted to current guidelines which require evaluation of oestrous cyclicity and sperm together with extended histopathology and organ weight information for both parents and offspring. It is however, considered to be a robust evaluation with no indication of adverse effects on reproduction hence no further testing is warranted.

Short description of key information:
The effects of benoxacor to fertility and general reproductive performance of rats have been evaluated in a two-generation study (OECD 416, 1983) conducted to GLP. No effect of benoxacor on reproduction was detected at the highest dose level tested, 1000 ppm, equivalent to 80 mg/kg bw/day. At this dose level and at the lower dose level of 500 ppm, parental toxicity was observed and mean pup weight at weaning was reduced. The overall NOAEL for toxicity was 50 ppm, corresponding to a mean daily intake of 4 mg/kg bw/day. Although the study was not conducted to current guidelines, it is considered to be robust and no further testing is warranted.

Justification for selection of Effect on fertility via oral route:
One reliable, GLP- and guideline-conform multi-generation study available.

Effects on developmental toxicity

Description of key information

The developmental toxicity of benoxacor has been evaluated in the rat and rabbit, in two key guideline studies (OECD 414, 1981) conducted to GLP. The substance was found not to be teratogenic in either species. In the rat no teratogenicity was seen in the presence of marked maternal effects or in the presence of reduced foetal weight and a delay in the rate of ossification of the foetal skeleton.
The NOAEL for maternal toxicity is 1 mg/kg bw/day in the rat and 12.5 mg/kg bw/day in the rabbit. The NOAEL for developmental toxicity is 100 mg/kg bw/day in the rat and 62.5 mg/kg bw/day in the rabbit. Although the studies were not conducted to current guidelines, they are considered to be robust and no further testing is warranted.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 February 1986 to 28 March 1986

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP study compliant with test guidelines of the time. However, current guidelines for prenatal developmental toxicity require an extended dosing period - from implantation to termination. Available as unpublished report, adequate for assessment although only minimal maternal toxicity seen at highest dose tested.

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

1981 (current guideline adopted 2001)

Deviations:

yes

Remarks:

does not meet current guideline specification

Qualifier:

according to guideline

Guideline:

EPA OPP 83-3 (Prenatal Developmental Toxicity Study)

Version / remarks:

1982 (current guideline adopted 1998)

Deviations:

yes

Remarks:

does not meet current guideline specification

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Approximately 17 weeks
- Weight at gestation day 0: 3.21-3.98 kg
- Housing: Individually in elevated stainless steel cages
- Diet: Purina Certified Rabbit Chow ® #5322 ad libitum
- Water: Tap water ad libitum
- Acclimation period: 3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 70-76°F
- Humidity: 18-55%
- Air changes (per hr): Not reported
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 24 February 1986 To: 28 March 1986

Route of administration:

oral: gavage

Vehicle:

other: distilled water containing 0.5% carboxymethylcellulose and 0.1% Tween 80

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Fresh preparations were made weekly and stored under refrigeration. The dose volume was 1 mL/kg body weight on day 7 of gestation.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Prior to initiation, samples were taken to determine homogeneity. Day 0 and day 7 stability analyses were performed on the vehicle, low and high dose dosing solutions. Freshly prepared samples of all dose levels from the first and last mixed batches were analysed for achieved concentration.

The dosing preparations were found to be stable (95-101% of target on day 7), homogeneous (91.9-103% of target) and the achieved concentrations ranged from 94.6-108% of target.

Details on mating procedure:

Artificial insemination

Duration of treatment / exposure:

13 days, gestation days 7-19 inclusive

Frequency of treatment:

Once daily

Duration of test:

29 days, gestation days 0-29

No. of animals per sex per dose:

15 mated females

Control animals:

yes, concurrent vehicle

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: days 0, 7, 9, 11, 15, 20, 24 and 29

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 7, 9, 11, 15, 20, 24 and 29

FOOD CONSUMPTION: Yes
Time schedule for examinations: days 0, 7, 9, 11, 15, 20, 24 and 29

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 29
- Macroscopic examination: main organs of the thoracic, pelvic and abdominal cavities

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

Fetal examinations:

- Body weight and sex: Yes: all per litter
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: all per litter
- Classification of foetal observations: Yes

Statistics:

Levene's test of homogeneity of variances initially. Homogeneous data were then analysed using one-way ANOVA; heterogeneous data were transformed where possible. When ANOVA was significant Dunnett's t-test was used to compare each group with the control. The Terpstra-Jonckheere nonparametric test for trend was performed on homogeneous and heterogeneous data. The Cochran-Armitage test for linear trend followed by the Fischer-Irwin 'exact' test was used for the percent of total foetuses and litters with a particular skeletal variant.

Indices:

Mean implantation efficiency

Historical control data:

Yes

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
No treatment-related effects on maternal body weight.
62.5 mg/kg bw/day: food consumption significantly decreased between days 11 to 15 of gestation.
No treatment-related macroscopic changes observed at necropsy.

Dose descriptor:

NOAEL

Effect level:

12.5 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

62.5 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
62.5 mg/kg bw/day: lower mean foetal body weight (not significant when litter size used as the covariate in the analysis). The incidence of foetal external, soft tissue or skeletal variations was not treatment-related nor was the incidence of foetal external or soft tissue malformations. Eight foetuses with skeletal malformations at the highest dose were not clearly treatment-related due to the findings being consistent with those found in historical control data.

Dose descriptor:

NOAEL

Effect level:

62.5 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Abnormalities:

not specified

Developmental effects observed:

not specified

Table 1 Group Mean Maternal Body Weight Change (g) During Gestation

Days	Dose level (mg/kg bw/day)
	0	0.5	2.5	12.5	62.5
0-7	0.14	0.14	0.09	0.13	0.16
7-20	0.16	0.08	0.16	0.17	0.06
20-29	0.11	0.13	0.05	0.08	0.17
0-29	0.41	0.36	0.31	0.38	0.43
7-29	0.27	0.21	0.22	0.25	0.27

No statistically significant differences

Table 2 Group Mean Food Consumption (g) During Gestation

Days	Dose level (mg/kg bw/day)
	0	0.5	2.5	12.5	62.5
0-7	1192	1220	1112	1274	1187
7-9	360	359	329	365	297
9-11	315	324	308	325	267
11-15	561	506	556	585	373*
15-20	777	673	758	731	604
20-24	608	551	543	539	591
24-29	515	482	431	453	634

P< 0.05 * statistically significant difference from control

 

Table 3 Group Mean Litter data

	Dose level (mg/kg bw/day)
	0	0.5	2.5	12.5	62.5
No. pregnant females	14	13	14	14	13
No. corpora lutea	11.1	11.2	10.7	11.6	13.2
No. implantations	7.4	7.6	6.1	7.9	8.8
% mean implantation efficiency	66.6	66.6	59.2	67.4	67.8
No. live foetuses	6.7	6.6	5.9	7.1	8.3
% males	41.5	56.0	42.4	44.8	55.1
Foetal weight (g) - covariate adjusted	46.2	46.8	45.8	46.7	46.1

No statistically significant differences

Table 4 Group Mean Foetal Observations

	Dose level (mg/kg bw/day)
	0	0.5	2.5	12.5	62.5
No. litters examined	14	13	14	14	13
No. foetuses examined	95	86	82	99	108
No. foetuses with external variations	0	1	0	0	0
No. foetuses with external malformations	0	0	0	0	1
No. foetuses with soft tissue variations	7	7	5	6	5
No. foetuses with soft tissue malformations	2	1	0	0	0
No. foetuses with skeletal variations	69	65	49	73	68
No. foetuses with skeletal malformations (% foetuses)	2 (2.1)	3 (3.5)	3 (3.7)	4 (4.0)	8 (7.4)

No statistically significant differences

Conclusions:

Administration of 62.5 mg/kg bw/day CGA154281 to pregnant rabbits during the period of organogenesis resulted in minimal maternal toxicity (a small, transient reduction in food consumption). The NOAEL for maternal toxicity was therefore 12.5 mg/kg bw/day. The NOAEL for developmental toxicity and teratogenicity was 62.5 mg/kg bw/day

Executive summary:

The study was designed to evaluate the developmental toxicity and teratogenic potential of benoxacor (CGA154281 technical) in rabbits. The test material was administered orally at 0.5, 2.5, 12.5 or 62.5 mg/kg bw/day during the period of organogenesis (days 7-19 of gestation). On gestation day 29, the dams were terminated and caesarean sections performed. Live foetuses were weighed and examined for external, soft tissue and skeletal malformations and variations.

The only effect of treatment at the highest dose of 62.5 mg/kg bw/day, was a small reduction in maternal food consumption during the dosing period. There was no clear evidence of developmental toxicity at this dose level and no evidence of teratogenicity.

 

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

62.5 mg/kg bw/day

Study duration:

subacute

Species:

rabbit

Quality of whole database:

Two GLP-conform studies are available, which are not fully compliant with most recent guidelines (but were conducted in accordance with guidance documents available at the time of conduct). Studies demonstrate developmental toxicity at elevated doses causing clearly maternal toxicity.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

The developmental toxicity of benoxacor has been evaluated in the rat and rabbit, in two key guideline studies (OECD 414, 1981) conducted to GLP.

Groups of 23 time-mated female rats were administered benoxacor by oral gavage on days 6 -15 of pregnancy at dose levels of 0, 1, 100 or 400 mg/kg bw/day. Foetuses were obtained by caesarean section on day 21 of pregnancy and examined for external, visceral and skeletal malformations and anomalies. 

The dose level of 400 mg/kg bw/day was toxic to the pregnant female rat resulting in changes in clinical condition including hunched appearance, urine staining, rough hair coat and alopecia, body weight loss and decreased body weight gain and reduced food consumption. Lower mean foetal weight was seen in the presence of this maternal toxicity with consequential delays in ossification of the fetal skeleton and possibly renal development. An increased incidence of early intra-uterine death was also observed. The NOAEL for maternal toxicity was 1 mg/kg bw/day and the NOAEL for developmental toxicity was 100 mg/kg bw/day. There was no evidence of teratogenicity at any dose level of benoxacor.

Groups of 15 mated female rabbits were administered benoxacor by oral gavage on days 7 -19 of pregnancy at dose levels of 0, 0.5, 2.5, 12.5 or 62.5 mg/kg bw/day. Foetuses were obtained by caesarean section on day 29 of pregnancy and examined for external, visceral and skeletal malformations and anomalies. 

The highest dose level of 62.5 mg/kg bw/day elicited only minimal toxicity in the pregnant female manifest as a small reduction in food consumption between gestation days 11 and 15. There was no effect of this dose level on mean foetal weight and there was no increase in incidence of external, visceral or skeletal malformations or anomalies. There was no evidence of teratogenicity at any dose level of benoxacor.

On the basis of these studies, it is concluded that benoxacor is not teratogenic to either rats or rabbits; in rat in particular, no teratogenicity was seen in the presence of marked maternal effects or in the presence of reduced foetal weight and a delay in the rate of ossification of the foetal skeleton.

The NOAEL for maternal toxicity is 1 mg/kg bw/day in the rat and 12.5 mg/kg bw/day in the rabbit. The NOAEL for developmental toxicity is 100 mg/kg bw/day in the rat and 62.5 mg/kg bw/day in the rabbit.

The studies were not conducted to current guidelines which require an extended dosing period to cover the period from implantation through to the day before termination. However, the studies are considered to be sufficiently robust and no further testing is warranted.

 

Justification for selection of Effect on developmental toxicity: via oral route:
Two GLP-conform studies are available, the one giving the lower NOAEL for developmental toxicity/teratogenicity was chosen.

Justification for classification or non-classification

The available studies are considered adequate and reliable for the purposes of classification and labelling.

The results do not lead to classification according to Directive 67/548/EEC or according to Regulation (EC) No. 1272/2008, as amended by Regulation (EC) No. 286/2011.