Disodium wolframate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Experiment start date (Animal arrival): 11 June 2015 - Completion date of experimental phase (Foetal pathology) - 08 July 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:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Principles of method if other than guideline:

ICH Harmonised Tripartite Guideline: Detection of Toxicity to Reproduction for Medicinal Products & Toxicity to Male Fertility S5 (R2): finalised (Step 4) November 2005.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Disodium wolframate

EC Number:

236-743-4

EC Name:

Disodium wolframate

Cas Number:

13472-45-2

Molecular formula:

Na2WO4

IUPAC Name:

disodium dioxotungstenbis(olate)

Test material form:

solid: crystalline

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 1504246000
- Expiration date of the lot/batch: 05 May 2018
- Purity: 93.2%
- Storage condition of test material: The test item was stored at room temperature (15 °C to 25 °C), protected from light.

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Covance Research Products Inc, 310 Swampbridge Road, Denver, PA 17517, USA
- Age at study initiation: The animals were approximately five months of age on arrival
- Weight at study initiation: On the first day of dosing the females weighed 2.72 kg to 3.93 kg
- Housing: The animals were housed individually in perforated-floor cages suspended over paper-lined trays.
- Diet (e.g. ad libitum): A pelleted diet, STANRAB (P) SQC supplied by Special Diet Services (SDS) freely available.
- Water (e.g. ad libitum): Tap water were freely available.
- Acclimation period: After five days acclimatisation they were re-examined and confirmed to be suitable for use.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The target range for temperature was 16 °C to 20 °C and recorded values were within these limits.
- Humidity (%): Humidity was not controlled but recorded
- Air changes (per hr): Room was air-conditioned.
- Photoperiod (hrs dark / hrs light): The study room was illuminated by fluorescent light set to give a cycle of 12 hours light and 12 hours dark and was air-conditioned

IN-LIFE DATES: From: 07 August 2015 To: 04 November 2015

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

purified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Formulations for use on the first and last day of dosing were analysed to determine their achieved concentrations. Vehicle (for Controls) from the first preparation and that for use on the last day of dosing were analysed to confirm the absence of the test item. Analysis were conducted at Kymos Pharma Services using method code C003-MP0023

Details on mating procedure:

The females were obtained from the supplier timed-mated. For mating, each female will have been paired with a sexually mature male of the same strain. The day on which mating is detected is designated Day 0 of gestation. The uterus of any apparently non-pregnant female was stained with ammonium sulphide to confirm pregnancy status.

Duration of treatment / exposure:

Animals will be dosed once daily, from Day 6 of gestation to Day 18 of gestation inclusive. Control animals will receive the vehicle only, following the same regimen as the other groups

Frequency of treatment:

Animals will be dosed once daily

Duration of test:

From Day 6 of gestation to Day 18 of gestation inclusive.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

10 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

30 mg/kg bw/day (actual dose received)

Doses / concentrations 4

Dose / conc.:

100 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Twenty-two females per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels were selected on the basis of results from a preliminary dose range-finding study performed at Sequani (Sequani Study Number: OHS0002. In that study, a dose level of 150 mg/kg/day sodium tungstate resulted in body weight losses, however, at 100 mg/kg/day there was only reduced body weight gain. A dose level of 100 mg/kg/day therefore, was considered to be a suitable high dose level for the current study

- Rationale for animal assignment (if not random): Allocation to groups was performed using a stratified randomisation procedure based on individual body weights recorded on Day 0 of gestation at the suppliers.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes
- Animals were examined twice daily for mortality and morbidity and were given a detailed clinical examination daily.

BODY WEIGHT: Yes
- Body weights were recorded on Day 0 of gestation by the supplier. At Sequani, body weights were recorded daily from Day 4 to 19 of gestation inclusive, and then on Days 22, 25 and 28 of gestation.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
The amount of food consumed by each animal was recorded daily over Days 5 to 6 of gestation and every two days thereafter during gestation

POST-MORTEM EXAMINATIONS: Yes
The females were killed on Day 28 of gestation. The animals were weighed, the thoracic and abdominal cavities were opened by a ventral mid-line incision and the major organs were examined. Gravid uterus and placenta weights were recorded and organs or tissues showing any macroscopic abnormalities were removed and retained in fixative.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
For pregnant females the following observations were made:
1. Number of corpora lutea
2. Number and distribution of implantations in uterine horns, classified as early intrauterine deaths, late intrauterine deaths, dead foetuses or live foetuses
3. Gravid uterus weight (Day 28 of gestation only)
4. Placental weight (Day 28 of gestation only)
The implantations are numbered separately for the right and left horns. Numbering is sequential, commencing at the ovarian end through to the cervix.

Fetal examinations:

- External examinations: Yes
- Soft tissue examinations: Yes
- Skeletal examinations: Yes
- Head examinations: Yes

The following observations were made for live foetuses killed on Day 28 of gestation: 1. Foetal weights 2. Foetal sexes (internal) 3. Foetal abnormalities (to include external, fresh visceral, fixed heads and/or skeletal examinations). Approximately 50 % of the foetuses in each litter were decapitated and the heads fixed in Bouins' fluid for subsequent serial sectioning to permit examination of the eyes, brain, nasal passages and tongue.

The head along the frontal parietal suture and the brain was examined. The carcasses were subsequently cleared in potassium hydroxide, stained with Alizarin
red S to visualise the ossified skeleton and examined for skeletal variants and abnormalities. Structural congenital abnormalities that impair or potentially impair the survival, development or function of the foetus are classified as major abnormalities. Other defects were classified as minor abnormalities. Commonly observed variations are recorded as variants.

Statistics:

Comparisons Group 1 against Groups 2, 3 and 4.
Statistical tests and parameters: Data was processed to give group mean values and standard deviations, where appropriate. Where the data allow, the following methods were used for statistical analysis. Depending on the nature of the data set to be analysed, appropriate tests were applied. Where parametric tests may be appropriate they were preceded by a check for homogeneity of variance using the Levene test and, where available, the Shapiro-Wilks test for normality. If either of these two assumptions fails a log transformation was applied before retesting. If the transformation fails, appropriate non-parametric tests were applied.

Indices:

- Pre-implantation loss (%) = [(no. of corpora lutea – no. of implantation sites)/no. of corpora lutea] x 100
- Post-implantation loss (%) = [(no. of implantation sites – no. of live foetuses)/no. of implantation sites ]x 100

Mean foetal body weights were calculated separately by sex for each litter; group mean body weights were calculated (separately by sex) from the litter means. Mean pre- and post-implantation losses were calculated on a proportional litter basis. The percentage of foetuses in each litter exhibiting each classification of abnormality was calculated; group mean percentages were calculated from the litter percentages. The percentage of male foetuses, out of the total number of foetuses, was calculated for each litter.

Historical control data:

Background data on the rate of spontaneous malformations have been accumulated.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Description (incidence and severity):

There were no clinical signs associated with sodium tungstate.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

There were three early decedent females, all given 10 mg/kg/day Sodium Tungstate. Female 428 died on Day 16 of gestation; necropsy findings were consistent with a dosing trauma. Female 434 showed signs of abortion on Day 26 of gestation and Female 423 aborted on Day 28 of gestation; as there were no abortions at higher doses of Sodium Tungstate these two events were considered not to be related to test item administration. There were no clinical signs associated with sodium tungstate.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In the group given 100 mg/kg/day, body weight gain was significantly lower than Controls during the dosing period (p<0.01) but thereafter, weight gain was similar to Controls. Body weights and body weight gains were similar to Controls for animals given 10 or 30 mg/kg/day Sodium Tungstate. See Tables 1a, 1b and 2 on "Any other information on results incl. tables" section below.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

There was no adverse effect of sodium tungstate on food intake; group mean intake was similar in all groups throughout the study.

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no maternal macroscopic abnormalities at necropsy that were considered to be related to sodium tungstate administration.

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Maternal developmental toxicity

Number of abortions:

effects observed, non-treatment-related

Description (incidence and severity):

Female 434 showed signs of abortion on Day 26 of gestation and Female 423 aborted on Day 28 of gestation; as there were no abortions at higher doses of sodium tungstate these two events were considered not to be related to test item administration. See Table 3 on "Any other information on results incl. tables" section below.

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

There were no effects of sodium tungstate on the mean numbers of implantations, the incidences of pre- and post-implantation loss or on the mean number of live foetuses. See Table 4b on "Any other information on results incl. tables" section below.

Total litter losses by resorption:

effects observed, non-treatment-related

Description (incidence and severity):

One pregnant rabbit with total resorption at the 30 mg/kg/day group. See Table 3 on "Any other information on results incl. tables" section below.

Early or late resorptions:

effects observed, non-treatment-related

Description (incidence and severity):

See Table 4a and 5a on "Any other information on results incl. tables" section below.

Dead fetuses:

no effects observed

Description (incidence and severity):

Female 450 given 30 mg/kg/day had total early intrauterine deaths and Females 469 and 486 given 100 mg/kg/day were not pregnant. There were no effects of sodium tungstate on the mean number of live foetuses. See Table 4b and 5b on "Any other information on results incl. tables" section below.

Changes in pregnancy duration:

not specified

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

See Table 3 on "Any other information on results incl. tables" section below.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOEL

Effect level:

30 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

2

Key result

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Description (incidence and severity):

There was no adverse effect of sodium tungstate on the mean foetal or placental weights. See Table 6 on "Any other information on results incl. tables" section below.

Reduction in number of live offspring:

no effects observed

Description (incidence and severity):

There were 22, 19, 21 and 20 females with live foetuses on Day 28 of gestation in the groups given 0, 10, 30 or 100 mg/kg/day, respectively. See Tables 4b and 5b on "Any other information on results incl. tables" section below.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

There was no adverse effect of sodium tungstate on the mean sex ratio. See Table 6 on "Any other information on results incl. tables" section below.

Changes in litter size and weights:

no effects observed

Description (incidence and severity):

See Table 6 on "Any other information on results incl. tables" section below.

Changes in postnatal survival:

not specified

External malformations:

no effects observed

Description (incidence and severity):

Major foetal abnormalities were noted in three, seven, four and four foetuses from three, five, three and two litters given 0, 10, 30 or 100 mg/kg/day, respectively. The nature, incidence and intergroup distribution of these abnormalities do not indicate an adverse effect of the test item. The incidences of minor and variant foetal abnormalities were similar in all groups.

Skeletal malformations:

no effects observed

Description (incidence and severity):

Major foetal abnormalities were noted in three, seven, four and four foetuses from three, five, three and two litters given 0, 10, 30 or 100 mg/kg/day, respectively. The nature, incidence and intergroup distribution of these abnormalities do not indicate an adverse effect of the test item. The incidences of minor and variant foetal abnormalities were similar in all groups.

Visceral malformations:

no effects observed

Description (incidence and severity):

Major foetal abnormalities were noted in three, seven, four and four foetuses from three, five, three and two litters given 0, 10, 30 or 100 mg/kg/day, respectively. The nature, incidence and intergroup distribution of these abnormalities do not indicate an adverse effect of the test item. The incidences of minor and variant foetal abnormalities were similar in all groups.

Effect levels (fetuses)

Key result

Dose descriptor:

NOEL

Effect level:

> 100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

external malformations

skeletal malformations

visceral malformations

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

Table 1a. Body weight gains (kg) - group mean values.

Sex: Female		Body Weight Gain (Day of Gestation)
Group		0 to 6#	6 to 7#	7 to 8#	8 to 9#	9 to 12#
Group: 1 Control 0 mg/kg/day	Mean	-0.033 R1	0.030 I2	0.004 R1	0.011 R1	0.066 I2
	SD	0.303	0.061	0.046	0.036	0.040
	N	22	22	22	22	22
Group: 2 Sodium Tungstate 10 mg/kg/day	Mean	0.007	0.005	0.007	0.005	0.073
	SD	0.100	0.052	0.046	0.036	0.052
	N	20	20	20	20	20
Group: 3 Sodium Tungstate 30 mg/kg/day	Mean	-0.035	0.005	0.004	0.007	0.072
	SD	0.141	0.039	0.068	0.062	0.060
	N	21	21	21	21	21
Group: 4 Sodium Tungstate 100 mg/kg/day	Mean	0.033	-0.012 W3	0.003	0.008	0.062
	SD	0.075	0.049	0.045	0.030	0.054
	N	20	20	20	20	20

# [Statistically Analysed]

1 [R - Automatic Transformation: Rank]

2 [I - Automatic Transformation: No Transformation]
3 [W - Test: Williams 2 Sided p < 0.05]

 

Table 1b. Body weight gains (kg) – group mean values (Continued)

Sex: Female		Body Weight Gain (Day of Gestation)
Group		12 to 15#	15 to 19#	6 to 19#	19 to 28#
Group: 1 Control 0 mg/kg/day	Mean	0.092 I1	0.072 R2	0.275 R2	0.149 R2
	SD	0.055	0.049	0.108	0.075
	N	22	22	22	22
Group: 2 Sodium Tungstate 10 mg/kg/day	Mean	0.078	0.065	0.233	0.138
	SD	0.054	0.066	0.104	0.157
	N	20	20	20	20
Group: 3 Sodium Tungstate 30 mg/kg/day	Mean	0.107	0.076	0.271	0.191
	SD	0.041	0.062	0.152	0.066
	N	21	21	21	21
Group: 4 Sodium Tungstate 100 mg/kg/day	Mean	0.096	0.024 S3	0.180 SS4	0.191
	SD	0.044	0.077	0.105	0.072
	N	20	20	20	20

# [Statistically Analysed]

1 [I - Automatic Transformation: No Transformation]

2 [R - Automatic Transformation: Rank]

3 [S - Test: Shirley 2 Sided p < 0.05]

4 [SS - Test: Shirley 2 Sided p < 0.01]

 

 Table 2. Terminal body weight (kg) adjusted for gravid uterus weight (g) - group mean values.

 

Sex: Female  (Group)		Dead Body Weight (g)#	Gravid Uterus  Wt#	BWt Adjusted for GUWt#	Adjusted BWt Gain 6 to 28#
Group: 1 Control 0 mg/kg/day	Mean	3.55 R1	443.2 I2	3.11 I2	-0.05 R1
	SD	0.30	73.5	0.25	0.11
	N	22	22	22	22
Group: 2 Sodium Tungstate 10 mg/kg/day	Mean	3.60	421.5	3.24	-0.02
	SD	0.34	92.7	0.19	0.13
	N	20	19	19	19
Group: 3 Sodium Tungstate 30 mg/kg/day	Mean	3.65	447.9	3.20	-0.01
	SD	0.22	75.5	0.20	0.16
	N	21	21	21	21
Group: 4 Sodium Tungstate 100 mg/kg/day	Mean	3.56	412.2	3.14	-0.06
	SD	0.21	71.9	0.22	0.10
	N	20	20	20	20

# [Statistically Analysed]

1 [R - Automatic Transformation: Rank]                 

2 [I - Automatic Transformation: No Transformation]

 

Table 3. Pregnancy data – summary

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Group Size		22	22	22	22
Not Pregnant		0	0	0	2
Not Pregnant %		0.0	0.0	0.0	9.1
Not Pregnant Died/Killed	Sum	0	0	0	0
Not Pregnant Schedule Kill	Sum	0	0	0	2
Pregnant		22	22	22	20
Pregnant %		100.0	100.0	100.0	90.9
Pregnant Died/Killed/Aborted	Sum	0	3	0	0
Pregnant with Total Resorption	Sum	0	0	1	0
Number with Live Foetuses	Sum	22	19	21	20

 

Table 4a. Uterine and implantation data - group mean values - by implant

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Number with Implantations		22	20	22	20
Number of Corpora Lutea#	Sum	217R1	198	221	200
	Mean	9.9R1	9.9	10.0	10.0
	SD	1.1	1.2	2.1	1.5
Number of Implantations#	Sum	205R1	174	203	181
	Mean	9.3R1	8.7	9.2	9.1
	SD	1.5	2.3	2.0	1.5
% Pre-implantation Loss #	Mean	5.4R1	12.3	8.1	9.2
Number of Early Deaths#	Sum	7 R1	3	7	12
	Mean	0.3R1	0.2	0.3	0.6
	SD	0.6	0.4	0.8	1.3
Number of Late Deaths#	Sum	1 R1	0	0	0
	Mean	0.0R1	0.0	0.0	0.0
	SD	0.2	0.0	0.0	0.0

# [Statistically Analysed]

1 [R - Automatic Transformation: Rank]

 

Table 4b. Uterine and implantation data - group mean values - by implant (Continued)

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Number of Dead Foetuses	Sum	0	0	0	0
	Mean	0.0	0.0	0.0	0.0
	SD	0.0	0.0	0.0	0.0
Number of Live Foetuses#	Sum	197 R1	162	196	169
	Mean	9.0 R1	8.1	8.9	8.5
	SD	1.6	2.9	2.5	1.7
% Post-implantation Loss #	Mean	3.8 R1	6.5	6.6	6.5
Mean % of Implantations	Mean	96.2	93.5	93.4	93.5

# [Statistically Analysed]

1 [R - Automatic Transformation: Rank]

 

Table 5a. Uterine and implantation data - group mean values - by foetus

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Number with Foetuses		22	20	21	20
Number of Corpora Lutea#	Sum	217 L1	198	215	200
	Mean	9.9 L1	9.9	10.2	10.0
	SD	1.1	1.2	2.0	1.5
Number of Implantations#	Sum	205 I2	174	200	181
	Mean	9.3 I2	8.7	9.5	9.1
	SD	1.5	2.3	1.4	1.5
% Pre-implantation Loss #	Mean	5.4 R3	12.3	6.1	9.2
Number of Early Deaths#	Sum	7R3	3	4	12
	Mean	0.3 R3	0.2	0.2	0.6
	SD	0.6	0.4	0.5	1.3
Number of Late Deaths#	Sum	1 R3	0	0	0
	Mean	0.0 R3	0.0	0.0	0.0
	SD	0.2	0.0	0.0	0.0

 

# [Statistically Analysed]

1 [L - Automatic Transformation: Log]                                                       

2 [I - Automatic Transformation: No Transformation]

3 [R - Automatic Transformation: Rank]

 

Table 5b. Uterine and implantation data - group mean values - by foetus (Continued)

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Number of Dead Foetuses	Sum	0	0	0	0
	Mean	0.0	0.0	0.0	0.0
	SD	0.0	0.0	0.0	0.0
Number of Live Foetuses#	Sum	197 R1	162	196	169
	Mean	9.0 R1	8.1	9.3	8.5
	SD	1.6	2.9	1.6	1.7
% Post-implantation Loss #	Mean	3.8 R1	6.5	2.2	6.5
Mean % of Implantations	Mean	96.2	93.5	97.8	93.5

# [Statistically Analysed]

1 [R - Automatic Transformation: Rank]

 

Table 6. Litter weights (g) / foetal data - group mean values

Sex: Female		Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4       Sodium Tungstate 100 mg/kg/day
Number with Live Foetuses		22	19	21	20
No of Live Foetuses		197	162	196	169
No of Male Foetuses		97	80	86	78
No of Female Foetuses		100	82	110	91
% of Male Foetuses#	Mean	48.7 I1	49.7	43.7	45.9
Litter Weight (g)#	Mean	298.56 R2	272.37	304.30	281.52
Foetal Weight (M+F) (g)#	Mean	33.57 I1	34.35	32.73	33.65
Foetal Weight (M) (g)	Mean	34.27	34.32	33.41	34.16
Foetal Weight (F) (g)	Mean	32.98	34.20	32.19	33.63
Placental Weight (g)#	Mean	3.45 I1	3.55	3.33	3.38

# [Statistically Analysed]

1 [I - Automatic Transformation: No Transformation]                                         

2 [R - Automatic Transformation: Rank]

 

Table 7. Examination of foetuses - summary of group mean values

Combined examination (external/visceral/skeletal)	Group: 1 Control 0 mg/kg/day	Group: 2 Sodium Tungstate 10 mg/kg/day	Group: 3 Sodium Tungstate 30 mg/kg/day	Group: 4 Sodium Tungstate 100 mg/kg/day
Total number of litters examined	22	19	21	20
Total number of foetuses examined	197	162	196	169
Number with major abnormalities	3	7	4	4
Mean % of foetuses examined	1.5	5.3	2.2	3.7
Number of litters affected#	3	5	3	2
Number with minor abnormalities	76	64	74	73
Mean % of foetuses examined	38.9	41.0	36.9	41.9
Number of litters affected#	22	18	20	18
Number with variations	197	162	196	169
Mean % of foetuses examine	100	100	100	100
Number of litters affected#	22	19	21	20

# = statistically analysed

Applicant's summary and conclusion

Conclusions:

Administration of sodium tungstate once daily by oral gavage from Day 6 of gestation until Day 18 of gestation to New Zealand White rabbits at dose levels of 10, 30 or 100 mg/kg/day was well tolerated with reductions in body weight gain at 100 mg/kg/day only. There was no effect on the pregnancy data and no foetal abnormalities considered to be related to administration of sodium tungstate. Based on the above findings the No Observed Effect Level (NOEL) for maternal toxicity was considered to be 30 mg/kg/day and the No Observed Adverse Effect Level (NOAEL) was considered to be 100 mg/kg/day. The NOEL and the NOAEL for embryo-foetal development were considered to be 100 mg/kg/day. There were no deaths or clinical signs considered to be related to sodium tungstate administration.   In the group given 100 mg/kg/day, mean body weight gain was significantly lower than that of the Controls during the dosing period.  Body weights and body weight gains were similar to Controls for animals given 10 or 30 mg/kg/day sodium tungstate.  Group mean food intake was similar in all groups throughout the study. There were 22, 19, 21 and 20 females with live foetuses on Day 28 of gestation in the groups given 0, 10, 30 or 100 mg/kg/day, respectively.  There was no effect of sodium tungstate on the uterine/implantation or foetal data. There were no test item-related major foetal abnormalities and the incidences of minor and variant foetal abnormalities were similar in all groups.