N-tert-butylbenzothiazole-2-sulphenamide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP study, comparable to guideline study with acceptable restrictions (purity of test substance not indicated).

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: acceptable well-documented study report

Principles of method if other than guideline:

Pilot teratology study.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- M/F ratio per cage: 1:1

Duration of treatment / exposure:

Day of mating was determined by daily inspection for the copulation plug or by vaginal smear of sperm.

Frequency of treatment:

Daily.

Duration of test:

Gestation day 6 through 15.

No. of animals per sex per dose:

4 females per dose.

Control animals:

yes, concurrent vehicle

Maternal examinations:

Mortality, clinical signs, body weights (GD 0, 6, 9, 12, 16 and 20).

Ovaries and uterine content:

Abodominal and thoracic cavities were examined, number and location of viable and nonviable fetuses, early and late resorptions, total implantations and corpora lutea.

Fetal examinations:

Abodominal and thoracic cavities were examined, number and location of viable and nonviable fetuses, early and late resorptions, total implantations and corpora lutea.

Abnormalities:

not specified

Developmental effects observed:

not specified

There were no changes in appearance or behavior attributable to treatment between contrl rats and rats treated with 10, 50 or 300 mg/kg bw. There were no biologically meaninful differences in the mean number of viable or nonviable fetuses, early or late resorptions, implantations or corpora lutea in rats receiving 10, 50 or 300 mg/kg bw/d. Slight loss in maternal body weight was seen in the 300 mg/kg bw/d dosage group in the first 3 days of treatment and slightly reduced maternal body weight gains for the treatment period were seen when compared to either control groups.

There was an increase in the mean number of early resorptions and a corresponding decrease in the mean number of viable fetuses in the 1000 mg/kg bw/d dosage group.Three of the four rats in the 1000 mg/kg bw/d dosage group had staining of the anogenital region. Maternal body weight losses were observed in this group during the entire treatment period. Three of the four rats in the 3000 mg/kg bw/d dosage group died by gestation day 12. Signs of maternal toxicity were seen in these rats before death and in the surviving rats in this group. A dose level of 1000 mg/kg bw/d is considered excessive for a teratology study.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1981

Report date:

1981

Reference 2

Reference Type:

publication

Title:

Teratology studies on benzothiazolesulfenamides

Author:

Stevens, M., W.

Year:

1982

Bibliographic source:

Toxicologist, 2, 73

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Pregnant Charles River COBS CD rats were used to determine the teratogenic potential of Santocure NS (N-tert-butyl-2-benzothiazolesulfenamide). Dosage levels of 0, 50, 150 or 500 mg/kg/day were administered orally by gavage as a single daily dose on days 6 through 15 of gestation. Cesarean sections were performed on all surviving dams on gestation day 20.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

N-tert-butylbenzothiazole-2-sulphenamide

EC Number:

202-409-1

EC Name:

N-tert-butylbenzothiazole-2-sulphenamide

Cas Number:

95-31-8

Molecular formula:

C11H14N2S2

IUPAC Name:

N-(1,3-benzothiazol-2-ylsulfanyl)-2-methylpropan-2-amine

Details on test material:

Santocure NS

Test animals

Species:

rat

Strain:

other: Charles River COBS CD rats

Details on test animals or test system and environmental conditions:

All animals were individually housed, except during mating, in suspended wire-mesh cages and maintained in a temperature-, humidity-, and light-controlled environment.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- M/F ratio per cage: 1: 1

Duration of treatment / exposure:

Days 6-15 of gestation.

Frequency of treatment:

Daily.

Duration of test:

Days 6 to 20 of gestation.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

150 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

500 mg/kg bw/day

No. of animals per sex per dose:

25 animals per dose

Control animals:

yes

Details on study design:

Dose selection rationale: Doses were selected based on the results of a pilot study (1979).
Within the primer study, animals were exposed to dose levels of 0 / 10 / 50 / 300 / 1000 / 3000 mg/kg bw/d TBBS on gestation days (GD) 6-15 inclusive.

≥ 1000 mg/kg bw/d: increases in early resorptions & reductions in viable fetuses were observed; 3 of 4 maternal animals had anogenital staining, and mean b.w. decreased throughout treatment.

At 3000 mg/kg bw/d: 3 of 4 maternal animals died by GD12, with preceding clinical signs concomitant with severe toxicity in all 4 animals.

Based on principles applied at the time of study conduct, authors concluded based on the above that a dose level of 1000 mg/kg bw/d is excessive for a teratology study, and as such a high dose between 300 and 1000 was selected (500 mg/kg bw/day).

Examinations

Maternal examinations:

Clinical signs, body weights, Cesarean section observations.

Ovaries and uterine content:

Uterus was excised and weighed prior to removal of the fetuses, the number and location of viable and nonviable fetuses, early and late resoptions and the number of total implantations and corpora lutea were recorded
Abdominal and thoracic cavities and organs of the dams were examined for grossly evident morphological changes
Uteri from females that appeared nongravid were opened and placed in a 10% ammonium-sulfid solution for confirmation of pregnancy status

Fetal examinations:

fetuses weights were recorded
fetuses were individually examined for external malformations and variations, including the palate and eyes
each fetus was externally sexed
Ca. one-half of the fetuses were placed in Bouin's fixative for subsequent visceral examination
Ca. one-half were fixed for subsequent skeletal examination

Historical control data:

Historical control data were available.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

No biologically meaningful differences in appearance or behavior in rats when compared to the control group Matting of the ventral or anogenital haircoat was noted in all four dosage groups with the greatest incidence occuring in rats in the 500 mg/kg bw/d dose group (4, 1, 2 and 10 respectively).A post-dose response of reduced activity was noted in two of these 10 rats of the highest dose group on gestation day 6 and 7. Incidental findings of hair loss and/or red matter on the nasal region were noted on several rats in the treated groups as well as the control group at various times during gestation.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Description (incidence and severity):

50 and 150 mg/kg bw/d: no biologically relevant differences compared to control. 500 mg/kg bw/d: very slight decrease in mean maternal body weight gain (ca. 1 -2 %) during the treatment period. However, no differences were noted in comparing the corrected gestation day 20 body weights (gestation day 20 body weight minus uterus weight) of the treated groups to the control group.

Food consumption and compound intake (if feeding study):

not specified

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 examined

Immunological findings:

not specified

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

50 and 150 mg/kg bw/d: no biologically relevant differences compared to control. 500 mg/kg bw/d: very slight decrease in mean maternal body weight gain (ca. 1 -2 %) during the treatment period. However, no differences were noted in comparing the corrected gestation day 20 body weights (gestation day 20 body weight minus uterus weight) of the treated groups to the control group.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Maternal developmental toxicity

Description (incidence and severity):

Slight decrease were noted in the mean numbers of corpora lutea (4 %, 1%, 4 % at 50, 150 and 500 mg/kg bw/d, respectively) and total implantations in all three treatment groups (7 %, 6% and 8 % at 50, 150 and 500 mg/kg bw/d). These decreases were attributed to random occurence as ovulation and implantation occur prior to treatment. A corresponding decrease in the mean numbers of viable fetuses in these groups was not considered biologically meaningful as the values were comparable to the historical control value.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Fetal body weight changes:

no effects observed

Description (incidence and severity):

There were nobiologically meaninful or statistically significant differences in the mean numbers of postimplantation loss, early resorptions, mean fetal body weight or the fetal sex distribution in the 50, 150 or 500 mg/kg/day dosage groups when compared to the control group.

Reduction in number of live offspring:

no effects observed

Description (incidence and severity):

There were nobiologically meaninful or statistically significant differences in the mean numbers of postimplantation loss, early resorptions, mean fetal body weight or the fetal sex distribution in the 50, 150 or 500 mg/kg/day dosage groups when compared to the control group.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

There were nobiologically meaninful or statistically significant differences in the mean numbers of postimplantation loss, early resorptions, mean fetal body weight or the fetal sex distribution in the 50, 150 or 500 mg/kg/day dosage groups when compared to the control group.

Changes in litter size and weights:

no effects observed

Description (incidence and severity):

There were nobiologically meaninful or statistically significant differences in the mean numbers of postimplantation loss, early resorptions, mean fetal body weight or the fetal sex distribution in the 50, 150 or 500 mg/kg/day dosage groups when compared to the control group.

Changes in postnatal survival:

not specified

External malformations:

no effects observed

Description (incidence and severity):

There were no biologically meaningful differences in the total numbers of fetuses or litters with malformations in the 50, 150, or 500 mg/kg/day dosage groups when compared with the control group.

Skeletal malformations:

no effects observed

Description (incidence and severity):

There were no biologically meaningful differences in the total numbers of fetuses or litters with malformations in the 50, 150, or 500 mg/kg/day dosage groups when compared with the control group.

Visceral malformations:

no effects observed

Description (incidence and severity):

There were no biologically meaningful differences in the total numbers of fetuses or litters with malformations in the 50, 150, or 500 mg/kg/day dosage groups when compared with the control group.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

Materal observations:

Clinical signs and mortality:

No mortality occured in any of the treated animals 50 and 150 mg/kg bw/d: no biologically meaningful differences in appearance or behavior in rats when compared to the control group Matting of the ventral or anogenital haircoat was noted in all four dosage groups with the greatest incidence occuring in rats in the 500 mg/kg bw/d dose group (4, 1, 2 and 10 respectively).A post-dose response of reduced activity was noted in two of these 10 rats of the highest dose group on gestation day 6 and 7. Incidental findings of hair loss and/or red matter on the nasal region were noted on several rats in the treated groups as well as the control group at various times during gestation.

Necropsy observations at Cesarean section:

Control: 1/25 hydrometra

Clinical 50 mg/kg bw/d: 1/25 ovarian cyst 500 mg/kg bw/d: 1/25 fibrinous pleuritis and congested lungs, 1/25 hydrometra, 1/25 ovarian cyst.

Body weights:

50 and 150 mg/kg bw/d: no biologically relevant differences compared to control. 500 mg/kg bw/d: very slight decrease in mean maternal body weight gain (ca. 1 -2 %) during the treatment period. However, no differences were noted in comparing the corrected gestation day 20 body weights (gestation day 20 body weight minus uterus weight) of the treated groups to the control group.

Cesarean section observations:

50, 150, 500 mg/kg bw/d: no biologically meaningful or statistically significant differences in the mean numbers of postimplantation loss, early resorptions, mean fetal body weight or fetal sex distribution compared to control

Slight decrease were noted in the mean numbers of corpora lutea (4 %, 1%, 4 % at 50, 150 and 500 mg/kg bw/d, respectively) and total implantations in all three treatment groups (7 %, 6% amd 8 % at 50, 150 and 500 mg/kg bw/d). These decreases were attributed to random occurence as ovulation and implantation occur prior to treatment. A corresponding decrease in the mean numbers of viable fetuses in these groups was not considered biologically meaningful as the values were comparable to the historical control value.

Fetal morphological observations:

50, 150 and 500 mg/kg bw/d: no biologically meaningful differences in the total numbers of fetuses or litters with malformations compared to control.

A slight increase in the number of litters and fetuses with undeveloped renal papillae and/or distended ureters was noted in the three treated groups but was not considered biologically meaninful since this increase was within the range estabished in the historical control data. Renal papillae not developed and/or distended ureters: control: fetuses: 3(1.7%), litters: 2( 8.3 %).

50 mg/kg bw/d: fetuses: 7(4.6 %), litters: 5( 22.7 %)

150 mg/kg bw/d: fetuses: 8(5.1 %), litters: 5( 21.7 %)

500 mg/kg bw/d: fetuses: 7(4.8 %), litters: 6( 27.3 %)

Applicant's summary and conclusion

Conclusions:

Treatment with Santocure NS (N-tert-butyl-2-benzothiazolesulfenamide) did not produce a teratogenic response when administered orally to pregnant Charles River COBS CD rats at a dosage level of 500 mg/kg/day (highest applied dose) or less.

Executive summary:

Pregnant Charles River COBS CD rats were used to determine the teratogenic potential of Santocure NS (N-tert-butyl-2-benzothiazolesulfenamide). Dosage levels of 0, 50, 150 or 500 mg/kg/day were administered orally by gavage as a single daily dose on days 6 through 15 of gestation. Cesarean sections were performed on all surviving dams on gestation day 20.

Treatment with Santocure NS (N-tert-butyl-2-benzothiazolesulfenamide) did not produce a teratogenic response when administered orally to pregnant Charles River COBS CD rats at a dosage level of 500 mg/kg/day (highest applied dose) or less.