Pyrasulfotole

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 Sep 2003 to 01 Jan 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Reference 2

Reference Type:

other: Regulatory Toxicology Position Paper

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

adopted 22 Jan 2001

Deviations:

yes

Remarks:

animals were housed with a16-hour light period

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

adopted 25 Jun 2018

Deviations:

yes

Remarks:

see "principles of method if other than guideline"

Principles of method if other than guideline:

Deviations to OECD guideline 414 (2018): Diet not analysed (phytoestrogens); no investigations on thyroid weight and histopathology; reproductive tract of fetuses or cryptorchidism not examined; no comparison between external vs. internal (gonadal) sex morphology; animals were housed with a16-hour light period.

GLP compliance:

yes (incl. QA statement)

Remarks:

Groupe Interministeriel des Produits Chimiques, Paris, France

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-[2-methanesulfonyl-4-(trifluoromethyl)benzoyl]-1,3-dimethyl-1H-pyrazol-5-ol

EC Number:

609-256-3

Cas Number:

365400-11-9

Molecular formula:

C14H13F3N2O4S

IUPAC Name:

4-[2-methanesulfonyl-4-(trifluoromethyl)benzoyl]-1,3-dimethyl-1H-pyrazol-5-ol

Test animals

Species:

rabbit

Strain:

New Zealand White

Remarks:

KBL (NZW) IOPS/SPF

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Elevage Scientifique des Dombes (ESD), Chatillon sur Chalaronne, France
- Age at study initiation: approximately 18 weeks
- Fasting period before study: no
- Housing: individually in polycarbonate cages on a perforated cage floor
- Diet: laboratory animal pellets 110C-10 from S.A.F.E. (Scientific Animal Food and Engineering, Augy, France), ad libitum
- Water: municipal tap water, ad libitum
- Acclimation period: 4 - 5 days prior to first treatment

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17 - 21
- Humidity (%): 40 - 70
- Air changes (per hr): 10 - 15
- Photoperiod (hrs dark / hrs light): 8/16

IN-LIFE DATES: From: 02 Sep 2003 To: 22 Oct 2003

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: 0.5% aqueous solution of methylcellulose 400 (Fluka, Mulhouse, France)

Details on exposure:

PREPARATION OF DOSE FORMULATIONS:
Formulations were prepared six times during the study and stored at approximately 5°C (± 3°C).
The suspensions were mixed continuously before and during treatment with an electromagnetic stirrer.

VEHICLE
- Amount of vehicle: 4 mL/kg bw

Details on analytical verification of doses or concentrations:

Analysis of dose formulations was performed using High Performance Liquid Chromatography (HPLC) with UV detection.
Homogeneity of the suspensions was checked during the first formulation for the lowest and highest concentrations. All concentrations were checked for all formulations. Stability of the compound in suspension in the vehicle was determined before the start of the study at 0.1 and 250 g/L in 0.5% aqueous methylcellulose in a previous range-finding study, where the test substance was found to be stable over a 29-day period under the conditions of study utilization.

Homogeneity and concentration of dosing suspensions of the test substance were between 91 and 106% of nominal values and within the in-house target range of 90 to 110% of nominal concentration.

Details on mating procedure:

- Impregnation procedure: purchased timed pregnant
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: observed copulation referred to as day 0 of pregnancy

Duration of treatment / exposure:

Gestation day (GD) 6 to 28

Frequency of treatment:

once daily, 7 days a week

Duration of test:

23 days of treatment

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

10 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

75 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

250 mg/kg bw/day

No. of animals per sex per dose:

25 females

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The range of dosages was selected in agreement with the Sponsor Representative and based on the results obtained in a previous range finding study in pregnant rabbits (Wason, 2002), where animals received doses of 0, 75, 250, 500, 750 and 1000 mg/kg bw/day from GD 6 to GD 28.
- Rationale for animal assignment: On each day of mating, the females were allocated to control and treated groups using a computerized randomization procedure. Body weight means were checked to ensure similar means among all groups.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were examined from GD 0 through GD 21. All cages were checked for dead or moribund animals twice daily, once in the morning and again in the afternoon (except at weekends and public holidays when checking was carried out once daily). Clinical signs were recorded once daily.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: GD 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 and 29.

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

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 29
- Organs examined: visceral organs, the number of ribs recorded and the kidney and urinary bladder examined for the presence of gritty material

OTHER:
- Liver weights were recorded and the liver was preserved in 10% neutral buffered formalin, but no histopathological examination was conducted

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: Uterine horn(s) without visible implantations were immersed in a 20% solution of ammonium sulfide according to the SALEWSKI method in order to visualize any sites which were not apparent

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: all per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: half per litter

Statistics:

Bartlett test was performed to compare the homogeneity of group variances. If the Bartlett test was not significant, means were compared using the analysis of variance (ANOVA). If the ANOVA was not significant, the group means were considered homogeneous and no further analysis was performed. If the ANOVA was significant, a Dunnett test (2-sided) was performed. If the Bartlett test was significant for body weight change and corrected body weight change, a Kruskal-Wallis test was performed. If the Kruskal-Wallis test was not significant, group means were considered homogeneous and no further analysis was performed. If the Kruskal-Wallis test was significant, means of exposed groups were compared to the mean of the control group using the Dunn test (2-sided).
If the Bartlett test was significant for food consumption or for liver weight, a log transformation of the data was performed.
-If the Bartlett test on log transformed data was not significant, means were compared using the ANOVA on log transformed data. If the ANOVA was not significant, the group means were considered homogeneous and no further analysis was performed. If the ANOVA was significant, a Dunnett test (2-sided) on log transformed data was performed.
- If the Bartlett test on log transformed data was significant even after transformation, group means were compared using the non-parametric Kruskal-Wallis test. If the Kruskal-Wallis test was not significant, the group means were considered homogeneous and no further analysis was performed. If the Kruskal-Wallis test was significant, means of exposed groups were compared to the mean of the control group using the Dunn test (2-sided).
For fetal sex and fetal death status, groups were compared using the Chi-square test for fetal sex parameter, using the Fisher Exact test (2-sided) for fetal death status parameter.

Indices:

- Pre-implantation loss
- Post-implantation loss
- Number of live fetuses
- Number of dead fetuses
- Percentage of dead fetuses per litter
- Percentage of male fetuses per litter
- Mean fetal body weight per litter
- Mean fetal body weight per group
- Mean fetal body weight per sex
- Percentage of fetuses affected per litter
- Mean percentage of fetuses affected per group

Historical control data:

Historical control data on fetal morphology data for six studies conducted in the laboratory in New Zealand White rabbits are available and presented in the report (see Attachment 7). Additional historical control data on fetal body weights from seven studies were provided in a separate document (M-284605-01-1, see Attachment 8).

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

All 25 females at 250 mg/kg bw/day were observed with intense yellow sediment in the urine on one or more occasion. In addition, at this dosage five females had few faeces on a number of occasions, even through this finding is very common in this strain, the incidence at the high dose is slightly higher than would be expected by chance. At 75 mg/kg bw/day, one female had intense yellow sediment in the urine on two occasions and one female beige sediment in the urine on four occasions.
No treatment-related signs were noted at 10 mg/kg bw/day.

See Attachment 1 for a summary of clinical findings (attached background material).

Dermal irritation (if dermal study):

not examined

Description (incidence and severity):

Not applicable.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

At 250 mg/kg bw/day, overall body weight change was reduced by 31% between GD 6 to 29. The effect was most pronounced between GD 8 to 10 when body weight remained static compared with a 0.03 kg body weight gain in the controls, the difference was statistically significant (p ≤ 0.01). Body weight change was unaffected by treatment at 75 or 10 mg/kg bw/day.
Corrected maternal body weight change (maternal body weight change independent of the uterine weight) was more pronounced at 250 mg/kg bw/day (-0.21 kg) compared with the controls (-0.11 kg), though not statistically significant. Corrected maternal body weight change at 75 or 10 mg/kg bw/day was comparable with the control group.

See Attachment 2 for a summary of body weight and body weight gain data (attached background material).

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

At 250 mg/kg bw/day, food consumption was reduced between each interval phase from GD 6 to 29 by between 9 and 24%, the effect being statistically significant (p ≤ 0.01) on several occasions, when compared with the controls. Food consumption was unaffected by treatment at 75 or 10 mg/kg bw/day.

See Attachment 3 for a summary of food consumption data (attached background material).

Food efficiency:

not examined

Description (incidence and severity):

Not applicable.

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

not examined

Description (incidence and severity):

Not applicable.

Ophthalmological findings:

not examined

Description (incidence and severity):

Not applicable.

Haematological findings:

not examined

Description (incidence and severity):

Not applicable.

Clinical biochemistry findings:

not examined

Description (incidence and severity):

Not applicable.

Endocrine findings:

not examined

Description (incidence and severity):

Not applicable.

Urinalysis findings:

not examined

Description (incidence and severity):

Not applicable.

Behaviour (functional findings):

not examined

Description (incidence and severity):

Not applicable.

Immunological findings:

not examined

Description (incidence and severity):

Not applicable.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Liver weight was increased by 22% (125.3 g, p<0.01) at 250 mg/kg bw/day, in comparison with the control group (102.6 g).
There was no effect on liver weight at 75 or 10 mg/kg bw/day.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Prominent lobulation of the liver was recorded in 2/25 females at 250 mg/kg bw/day.
There was an isolated incidence of prominent lobulation in the liver at both 75 and 10 mg/kg bw/day. However, in isolation, with no corresponding liver weight effect or dose relationship, this finding is considered to be fortuitous at these two dose levels. Accordingly, no treatment-related macroscopic findings were noted at 75 or 10 mg/kg bw/day.

Neuropathological findings:

not examined

Description (incidence and severity):

Not applicable.

Histopathological findings: non-neoplastic:

not examined

Description (incidence and severity):

Not applicable.

Histopathological findings: neoplastic:

not examined

Description (incidence and severity):

Not applicable.

Other effects:

not examined

Description (incidence and severity):

Not applicable.

Maternal developmental toxicity

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:

not examined

Changes in number of pregnant:

no effects observed

Other effects:

not examined

Description (incidence and severity):

Not applicable.

Details on maternal toxic effects:

Adverse maternal effects were limited to few faeces, reduced food consumption, reduced body weight gain and increased liver weights at 250 mg/kg bw/day.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEL

Effect level:

75 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: no adverse effects noted at 75 mg/kg bw/day

2

Key result

Dose descriptor:

LOAEL

Effect level:

250 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

body weight and weight gain

clinical signs

food consumption and compound intake

organ weights and organ / body weight ratios

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Description (incidence and severity):

No organ changes were noted.

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

At 250 mg/kg bw/day male fetal weights were reduced by 14%, female fetal weights by 16% and body weight for the combined sexes by 15%. In each case the effect was statistically significant (p ≤ 0.01).

Slightly reduced fetal weights noted at 75 and 10 mg/kg bw/day were considered to be chance findings in the light of the slight effect, lack of dose response and the fact that values were within the in-house historical control range. In additional position papers (M-284605-01-1 and M-301557 01-1) on this topic it is further mentioned that control fetal weight in this study is slightly above the historical control studies in terms of mean body weights and percentile ranges, and thus the slight difference between this control group and the 10 and 75 mg/kg bw/day groups are not due to an effect of treatment on fetal body weights. Instead, they are due to concurrent control values which are slightly higher than normal.

See Attachment 4 for a summary of fetal body weights (attached background material).

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

Anogenital distance of all rodent fetuses:

not examined

Description (incidence and severity):

Not applicable.

Changes in postnatal survival:

not examined

Description (incidence and severity):

Not applicable.

External malformations:

effects observed, treatment-related

Description (incidence and severity):

The number of runt fetuses (bw < 28.0 g) was clearly increased at 250 mg/kg bw/day, where the mean percentage of fetuses classified as runts was 20.1% compared with 5.2% in the control group. At 75 mg/kg bw/day, the mean percentage of runt fetuses was very similar to the control value, whereas at 10 mg/kg bw/day the mean percentage was higher. However, in the absence of a dose-related response, the apparent effect at 10 mg/kg bw/day is considered to be incidental.

The following anomalities were considered incidental due to their isolated occurrence and/or coverage by historical control data: one incidence of umbilical hernia at 250 mg/kg bw/day, two incidences of fetuses (from one litter) with malrotated forepaws at 250 mg/kg bw/day.

See attachment 5 for a summary of external fetal observations (attached background material).

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

A small number of malformations were recorded and were confined to the 10 mg/kg bw/day dose level and the control group. In the absence of findings at the two higher dose levels, these malformations are regarded as incidental.

A few treatment-related altered ossification patterns and increased incidence of minor skeletal variants were noted at 75 and 250 mg/kg bw/day:

At 250 mg/kg bw/day, the following anomaly; 13th thoracic rib (unilateral/bilateral) with the presence of 27 pre-sacral vertebrae, was increased compared with the control group. At this dosage, the incidence of the following variants was higher than in the controls: atlas centrum unossified, extra ossification site between the atlas and axis, 13th thoracic rib (unilateral/bilateral) or 13th thoracic rib (bilateral, short unilaterally), 1st metacarpal incomplete ossification or unossified, insertion point(s) of pelvic girdle on 2nd sacral vertebra, and bilateral incomplete ossification of the pubis.

At 75 mg/kg bw/day, the following anomaly was slightly increased; 13th thoracic rib (unilateral/bilateral) with the presence of 27 pre-sacral vertebrae. In addition, a number of variants were increased including; extra ossification site between the atlas and axis, 13th thoracic rib (unilateral/bilateral) or 13th thoracic rib (bilateral, short unilaterally), and insertion point(s) of pelvic girdle on 2nd sacral vertebra.

At 10 mg/kg bw/day, there was slight increase in the variant finding 13th thoracic rib (unilateral/bilateral) or 13th thoracic rib (bilateral, short unilaterally), which was marginally outside the in-house historical control range. However, the percentage of dams having 13/13 ribs or 12/13 ribs was 79%, 83%, 96% and 77% at 0, 10, 75 and 250 mg/kg bw/day, respectively, confirming that this finding is a common variant at both the maternal and fetal level.

No other variants or anomalies are considered to be related to treatment as they occurred at a similar frequency in the control group, did not occur in a dose-related manner or were within in-house historical control ranges.

See attachment 6 for a summary of fetal skeletal observations (attached background material).

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

The few malformations noted were distributed across the groups including the control group, and in the absence of a dose-related increase, none of the malformations observed are considered to be treatment-related. A small number of variants and anomalies appeared across the groups, including controls, none of the findings occurred in a dose-related manner.

Other effects:

not examined

Description (incidence and severity):

Not applicable.

Details on embryotoxic / teratogenic effects:

No treatment related findings indicative of teratogenicity were seen in th study. Adverse fetal effects included reduced fetal weight and increased incidence of runt fetuses at 250 mg/kg bw/day, as well as treatment-related altered ossification patterns and increased incidence of minor skeletal variants at 75 and 250 mg/kg bw/day.

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOAEL

Effect level:

10 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no adverse effects were noted at 10 mg/kg bw/day

2

Key result

Dose descriptor:

LOAEL

Effect level:

75 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

skeletal malformations

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Description (incidence and severity):

No treatment-related fetal malformations were noted.

Overall developmental toxicity

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

250 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

Applicant's summary and conclusion

Conclusions:

The study was performed under GLP conditions and according to OECD TG 414 (adopted 2001). Clinical signs were limited to yellow or beige sediments in the urine of several animals at 75 and 250 mg/kg bw/day. Maternal body weight change was decreased at 250 mg/kg bw/day, as well as a decrease in corrected maternal body weight change at this dose. Food consumption was reduced at 250 mg/kg bw/day throughout the study. Maternal liver weight was increased at 250 mg/kg bw/day. Per group, the percentage of dams with more than 24 ribs ranged from 77% to 96%, indicating that the majority of healthy, successfully reproducing adults commonly have either 25 or 26 ribs instead of the 24 ribs which are commonly accepted as the "correct" number of ribs. Fetal body weight was decreased at 250 mg/kg bw/day, and the incidence of runt fetuses was increased at 250 mg/kg bw/day. The only treatment-related findings in the pups which were increased by administration of the test substance were decreases or delays in ossification and increased incidence of 13th thoracic ribs. These findings were considered to be related - as was demonstrated in the rat - to increased maternal plasma tyrosine concentration after administration of an HPPDase inhibitor. Based on decreased maternal body weight and food consumption, the maternal LOAEL was 250 mg/kg bw/day. The maternal NOAEL in the rabbit was 75 mg/kg bw/day. Due to decreased ossification and other minor skeletal findings, the fetal LOAEL was 75 mg/kg bw/day, while the NOAEL was 10 mg/kg bw/day