1-Hexyl 4,5-diamino pyrazole hemisulfate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Feb. 07, 2012 to May. 29, 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study well documented, followed guideline, GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Remarks:

according to United States Code of Federal Regulations, Japan and OECD principles of GLP

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-hexylpyrazole-3,4-diamine;sulfuric acid

EC Number:

696-231-5

Cas Number:

1361000-03-4

Molecular formula:

C9H18N4 x 0.5 H2SO4

IUPAC Name:

2-hexylpyrazole-3,4-diamine;sulfuric acid

Constituent 2

Reference substance name:

C6-Pyrazole hemisulfate

IUPAC Name:

C6-Pyrazole hemisulfate

Constituent 3

Reference substance name:

1-hexyl-1H-pyrazole-4,5-diamine hemisulfate

IUPAC Name:

1-hexyl-1H-pyrazole-4,5-diamine hemisulfate

Test material form:

solid: crystalline

Details on test material:

- Name of test material: C6-Pyrazole hemisulfate; 4,5-Diamino-1-hexyl-1H-pyrazole, hemisulfate- TSIN: WR804146- Substance type: Pure active substance- Physical state: White crystalline solid- Storage conditions: At room temperature (20°C to 24°C), protected from light, and purged with nitrogen

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)

Details on test animals or test system and environmental conditions:

TEST ANIMALS- Source: Charles River Laboratories, Inc., Portage, MI.- Age at study initiation: 66 days of age at arrival- Weight at study initiation: 207-244 g- Fasting period before study: Not reported- Housing: Individually housed in stainless steel, wire-bottomed cages, except duringthe cohabitation period - Bedding: Nesting material (bed-o’cobs®)- Diet: Certified Rodent Diet #5002; ad libitum- Water: Chlorine added reverse osmosis water, processed from a local source; ad libitum- Acclimation period: 5 daysENVIRONMENTAL CONDITIONS- Temperature: 20.7 – 23.7 °C- Relative humidity: 35.4 - 65.3% - Air changes: 10 changes per hour of 100% fresh air that had been passed through 99.97% HEPA filters- Photoperiod: 12-hours light: 12-hours dark fluorescent light cycleIN-LIFE STARTING DATE: Not reportedIN-LIFE ENDING DATE: Mar. 09, 2012

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: 10% propylene glycol and ascorbic acid (0.1% w/w) in reverse osmosis water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The dose formulations were prepared daily and maintained under ambient conditions, protected from light, and purged with nitrogen. The dose formulations were stirred for at least 30 minutes before and continuously during dose administration.VEHICLE- Concentration in vehicle: 0, 0.5, 1.0, 1.6 and 4 mg/mL at the dose levels of 0, 2.5, 5, 8 and 20 mg/kg bw/day. Doses were adjusted based on the most recently recorded body weight.- Amount of vehicle: 5 mL/kg bw Analytical verification of doses or concentrations yes Details on analytical verification of doses or concentrationsDose formulations were tested for stability and concentration.- Method: High Performance Liquid Chromatography (HPLC)- Sampling: Duplicate sets of samples (2.5 mL) from the first, intermediate, and last preparations were taken from Groups 1 through 5.- Storage: Duplicate samples were purged with nitrogen and transferred under ambient conditions, protected from light, to the analytical laboratory at the Testing Facility for concentration analysis. The remaining samples were retained at the Testing Facility as backup samples and were discarded prior to issue of the Final Report.Further details were provided in the study report.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Results of Test substance analysis: All results obtained from analysis of dose formulation samples met acceptance criteria, with the exception of the low dose (0.5 mg/mL) concentration from the intermediate preparation (2.8% to 3.8% excursion from acceptance criteria). Formulation stability was established for the 0.5-mg/mL and 1.6-mg/mL concentrations for 21 days and for the 4.0-mg/mL concentration for 27 days when purged with nitrogen and stored frozen (< -80°C) and protected from light.

Details on mating procedure:

- Impregnation procedure: co-habitation- M/F ratio per cage: 1:1- Length of cohabitation: 5 days - Proof of pregnancy: Female rats with spermatozoa observed in a smear of the vaginal contents and/or a copulatory plug observed in situ were considered to be at gestation Day 0 and assigned to individual housing.

Duration of treatment / exposure:

From Day 6 to 20 of gestation

Frequency of treatment:

Once daily

Duration of test:

21 days

No. of animals per sex per dose:

25 pregnant females/dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Rationale for animal assignment: Healthy, mated females were assigned to groups using a computer-based randomization procedure on the basis of gestation Day 0 body weights.- Justification for the doses selected: Dose levels were selected by the Sponsor on the basis of a dose range-finding developmental toxicity study of C6 pyrazole hemisulfate in rats. It was presumed that maternal toxicity would be apparent in the histopathological findings and was anticipated at least at the high dose level.- Justification for Test System: Rat was selected because: 1) it is a standard species accepted for use in embryo-fetal development studies; 2) this species and strain has been demonstrated to be sensitive to developmental toxicants; and 3) historical data and experience exist at the Testing Facility.- Justification for route of administration: The oral (gavage) route was selected for use because, in comparison with the dietary route, the exact dose can be accurately administered.

Examinations

Maternal examinations:

MORTALITY: Yes- Time schedule: Twice dailyCAGE SIDE OBSERVATIONS: Yes- Time schedule: Daily - The rats were observed for general appearance twice during the acclimation period, on Day 0, daily before each dose was administered, and once daily during the post- dose period. Post-dose observations were conducted between 1 and 2 hours after dose administration, and at the end of the normal working day.BODY WEIGHT: Yes- Time schedule for examinations: Body weights were recorded twice during the acclimation period, on gestation Day 0, and daily during the dose and post-dose periods.FOOD CONSUMPTION: Yes- Time schedule for examinations: Food consumption values were recorded on gestation Days 0, 6, 9, 12, 15, 18, and 21.WATER CONSUMPTION AND COMPOUND INTAKE: NoMATING PERFORMANCE: Yes, mating performance was evaluated daily during the cohabitation period.HEMATOLOGY: Yes- Time schedule for collection of blood: On gestation Day 21, prior to scheduled euthanasia. - Anaesthesia used: Yes, isofluorane/oxygen anaesthesia was used- Site of blood collection: 1 mL of blood was collected from the inferior vena cava. - Animals fasted: Not reported- Parameters checked: Red blood cell count, Hemoglobin concentration, Hematocrit, Mean corpuscular volume, Mean corpuscular hemoglobin concentration, Mean corpuscular hemoglobin, Reticulocyte count (absolute), Mean platelet volume, Platelet count, White blood cell count, Neutrophil count, Lymphocyte count, Monocyte count, Eosinophil count, Basophil count, Large unstained cells and Other cells (as appropriate).POST-MORTEM EXAMINATIONS: Yes- Sacrifice on gestation Day #21: All mated females were euthanized by an intravenous injection of sodium pentobarbital and examined for gross lesions. A gross necropsy of the thoracic, abdominal, and pelvic viscera was performed for each rat. Gross lesions were collected and preserved in neutral buffered 10% formalin. Live fetuses were euthanized by an intraperitoneal injection of sodium pentobarbital.- Tissues examined at necropsy: Bone marrow, femur, Cervix, Esophagus, Gross lesions/masses, Heart, Kidney, Liver, Lung, Ovaries, Spleen, Stomach, Trachea and Uterus were examined.ORGAN WEIGHTS: The gravid uterus, liver, and spleen were weighed for all rats at scheduled euthanasia.HISTOPATHOLOGY: The liver, spleen, and bone marrow from each rat assigned to study were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin and histopathological evaluation was performed.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: YesExaminations included:- Gravid uterus weight: Yes- Number and distribution of corpora lutea: Yes- Number of implantations: Yes- Placentae (size, color or shape): Yes- Number of early resorptions: Yes- Number of late resorptions: Yes- Number of live and dead fetuses: Yes- Other: Uteri of apparently non-pregnant rats were examined while being pressed between glass plates to confirm the absence of implantation sites.

Fetal examinations:

Fetuses were euthanized via an intraperitoneal injection of sodium pentobarbitaland examined for sex and external abnormalities. Abnormalities were classified as malformations, variations or skeletal ossification parameters.- External examinations: Yes, also late resorptions were examined for external abnormalities and sex to the extent possible.- Soft tissue examinations: Yes, approximately one-half of the fetuses in each litter were examined for visceral abnormalities by using a modification of the microdissection technique of Staples. Each fetus was fixed in Bouin's solution, and the heads were subsequently examined by free-hand sectioning; head sections were stored in alcohol. - Skeletal examinations: Yes, approximately one-half of the fetuses in each litter) were examined for skeletal abnormalities after staining with alizarin red S.- Body weight: The body weight of each fetus was recorded. Fetuses were individually identified with the study number, litter number, and uterine distribution.

Statistics:

- Clinical observations and other proportional data were analyzed using the Variance Test for Homogeneity of the Binomial Distribution.- Continuous data (e.g., maternal body weights, body weight changes, food consumption values and litter averages for percent male fetuses, percent resorbed conceptuses, fetal body weights and fetal anomaly data) were analyzed using Bartlett’s Test of Homogeneity of Variances and the Analysis of Variance, when appropriate [i.e., Bartlett’s Test was not significant (p>0.001)].- If the Analysis of Variance was significant (p≤0.05), Dunnett’s Test was used to identify the statistical significance of the individual groups. If the Analysis of Variance was not appropriate [i.e., Bartlett’s Test was significant (p≤0.001)], the Kruskal-Wallis Test was used (≤75% ties).- In cases where the Kruskal-Wallis Test was statistically significant (p≤0.05), Dunn’s Method of Multiple Comparisons was used to identify the statistical significance of the individual groups.- If there were greater than 75% ties, Fisher’s Exact Test was used to analyze the data. Count data were evaluated using the procedures described above for the Kruskal-Wallis Test.Statistical analyses were performed for hematology.If both assumptions were fulfilled, a single-factor ANOVA was applied, with animal grouping as the factor, utilizing a p ≤ 0.05 level of significance. If the parametric ANOVA was significant at p ≤ 0.05, Dunnett's test was used to identify statistically significant differences between the control group and each test article-treated group at the 0.05 level of significance.If either of the parametric assumptions were not satisfied, then the Kruskal-Wallis nonparametric ANOVA procedure was used to evaluate intergroup differences (p ≤ 0.05). If the non-parametric Kruskal-Wallis ANOVA was significant at p < 0.05, Dunn's test was used to identify statistically significant differences between the control group and each test article-treated group.

Indices:

Not reported

Historical control data:

Not reported

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes. Remark: at 20 mg/kg bw/dayDetails on maternal toxic effects:MORTALITY AND CLINICAL SIGNS: No mortality or adverse clinical signs occurred on study as a result of treatment with test substance.BODYWEIGHT Mean absolute body weights and body weight changes, mean gravid uterine weights, and maternal body weights and body weight changes corrected for gravid uterine weights were unaffected by treatment with the test substance at dose levels as high as 8.0 mg/kg/day. Transient effects on body weight gain were observed early in the dose period (gestation Days 6 to 9) at 20 mg/kg/day. A slight reduction (89% of the control group value) in mean body weight gain occurred in the 20 mg/kg/day dose group during the entire dose period, following correction for gravid uterine weights. None of these values were significantly different from the respective control group values.FOOD CONSUMPTIONMean absolute (g/day) and relative (g/kg/day) food consumption values were unaffected by administration of test substance at dose levels as high as 20 mg/kg/day. Food consumption values were generally comparable among the 5 dose groups and did not significantly differ.CLINICAL PATHOLOGYA significant increase (p≤ 0.05) in mean reticulocyte count occurred in the 20 mg/kg/day dose group, in comparison with the control group value. This increase occurred in the highest dose group tested on study; however, there was no apparent dose-dependent pattern of effect in the lower dose groups, there were no microscopic correlates in the bone marrow (femur), liver, or spleen, and all of the values were within the range of historical control data.Mean platelet volume was increased or significantly increased (p≤ 0.05) in each of the groups administered the test substance, in comparison with the respective control group values. These increases occurred in a dose-dependent manner. Although these increases appeared to be related to administration of the test substance, there were no microscopic correlates in the bone marrow (femur), liver, or spleen, and all of the values were within the range of historical control data with the exception of the 20 mg/kg/day dose group.NECROPSYAdministration of the test substance at dose levels as high as 20 mg/kg/day did not result in gross lesions in the bone marrow (femur), liver, or spleen.ORGAN WEIGHTSNo significant test substance-related organ weight changes were noted. There were isolated organ weight values that differed from their respective controls; however, there were no patterns, trends, or correlating data to suggest these values were toxicologically relevant. Thus, the organ weight differences observed were considered incidental and unrelated to administration of test substance. Non-statistically significant increases (107% and 109% of the control group value) in absolute and relative spleen weights occurred in the 20 mg/kg/day dose group; however, there were no microscopic correlates. HISTOPATHOLOGYMicroscopic examination of the bone marrow (femur), liver, and spleen from all female rats on study revealed no microscopic changes that could be attributed to administration of test substance at dose levels as high as 20 mg/kg/day.OVARIAN AND UTERINE EXAMINATIONSDue to premature deliveries in the 0 (Control), 2.5, and 8.0 mg/kg/day dose groups, ovarian/uterine examination observations on gestation Day 21 were based on 24, 24, 25, 22, and 25 pregnant rats in the 0 (Control), 2.5, 5.0, 8.0, and 20 mg/kg/day dose groups, respectively.The litter averages for corpora lutea, implantations, percentage of pre-implantation loss, litter sizes, live fetuses, early and late resorptions, percentage of post-implantation loss, and percentage of resorbed conceptuses per litter were comparable among the 5 dose groups and did not significantly differ. No dam had a litter consisting of only resorbed conceptuses, and there were no dead fetuses. All placentae appeared normal.

Effect levels (maternal animals)

1

Key result

Dose descriptor:

NOAEL

Effect level:

8 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

other: Slight reduction of mean body weight gain (non-significant) and changes in haematology (significant, non-dose dependent increase in mean reticulocyte count and significant dose-dependent increase in mean platelet volume) at 20 mg/kg bw/day

2

Key result

Dose descriptor:

NOAEL

Effect level:

8 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Remarks on result:

other: Reduced fetal body weights at 20 mg/kg bw/day

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: fetal weight was decreased at 20 mg/kg bw/dayDetails on embryotoxic / teratogenic effects:EXTERNAL, SKELETAL AND VISCERAL EXAMINATIONSNo fetal gross external, soft tissue, or skeletal alterations (malformations or variations) were caused by administration of test substance at dose levels as high as 20 mg/kg/dayWEIGHT OF FETUSESMean fetal body weights (female and total) in the 20 mg/kg/day dose group were significantly lower (p≤ 0.05 [both were 96% of the control group value]), in comparison with the respective control group values. Although these values were within the range of historical control data for the Testing Facility, a dose-dependent pattern of effect was apparent across the dose groups but only achieved statistical significance at the 20 mg/kg/day dose level. Therefore, lower fetal body weight averages at 20 mg/kg/day were attributed to administration of the test substance.SEX OF THE FETUSESThe mean percentage of live male fetuses per litter was significantly lower (p≤ 0.01) in the 5.0 mg/kg/day dose group, in comparison with the control group value. This significant difference in fetal sex ratio was not attributed to administration of the test substance because:1) A dose-dependent pattern of effect was not apparent; and 2) the value was within the range of historical control data for the Testing Facility.OSSIFICATION SITESThe average number of ossification sites per litter was also comparable among the 5 dose groups and did not significantly differ.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 8 mg/kg bw/day (nominal)

Basis for effect level:

other: developmental toxicity

Remarks on result:

other: Reduced fetal body weights at 20 mg/kg bw/day

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Administration of C6-Pyrazole hemisulfate to female Crl:CD(SD) rats by oral gavage during gestation Days 6 to 20 at dose levels of 0, 2.5, 5, 8 and 20 mg/kg bw/day resulted in a NOAEL of 8 mg/kg bw/day for both maternal toxicity and developmental toxicity.

Executive summary:

The developmental toxicity study of C6-Pyrazole hemisulfate was conducted following the OECD Guideline 414 (Prenatal Developmental Toxicity Study).

Female (207-244 g) rats of Crl:CD(SD) strain (Source: Charles River Laboratories, Inc., Portage, MI) were used in this study. After receipt, animals were acclimatised for 5 days and maintained under standard laboratory conditions (temperature: 20.7–23.7°C, relative humidity: 35.4-65.3%, air changes: 10 times/hour, photoperiod: 12 hrs dark / 12 hrs light). The animals were individually housed except during the cohabitation period. The animals were fed on Certified Rodent diet and reverse osmosis water, ad libitum.

After acclimatization, male and female rats were co-habited at a mating ratio of 1:1 for a period of 5 days. The presence of spermatozoa in a vaginal smear or a copulatory plug observed in situ was considered as Day 0 of gestation.

The test substance dissolved in 10% propylene glycol and ascorbic acid (0.1% w/w) in reverse osmosis water was administered by oral gavage daily from Day 6 to Day 20 of gestation at the dose levels of 0 (vehicle), 2.5, 5, 8 and 20 mg/kg bw/day (volume of 5 mL/kg bw).

The animals were assessed for viability at least twice daily and also for clinical signs. Body weights were recorded twice during the acclimation period, on Day 0, and daily during the dose and post-dose periods. Food consumption values were recorded on Days 0, 6, 9, 12, 15, 18, and 21.

 

On gestation Day 21, prior to scheduled euthanasia, blood samples were collected and analysed for various parameters. On Day 21, the dams were caesarean-sectioned, and examined for gross lesions. The ovaries and uterus were examined for number and distribution of corpora lutea, gravid uterus weight, implantation sites, placentae (size, color or shape), live and dead fetuses, and early and late resorptions. The liver, spleen, and bone marrow from each rat assigned to study were examined by histopathological evaluation.

 

Fetuses were euthanized and examined for sex and external abnormalities. The body weight of each fetus was recorded. One-half of the fetuses in each litter were examined for visceral abnormalities and the other half of the fetuses in each litter were examined for skeletal abnormalities.

 

No mortality or adverse clinical signs occurred on study as a result of treatment with test substance. There were no effects on food consumption attributed to administration of the test substance. Transient effects on body weight gain were observed early in the dose period (Days 6 to 9) at 20 mg/kg/day. A slight reduction (89% of the control group value) in mean body weight gain occurred in the 20 mg/kg/day dose group during the entire dose period, following correction for gravid uterine weights. None of these values were significantly different from the respective control group values.

 

Significant increases in mean reticulocyte count (non-dose dependent increase) and mean platelet volume (dose-dependent increase) and non-statistically significant increases (107% and 109% of the control group value) in absolute and relative spleen weights occurred in the 20 mg/kg/day dose group; however, there were no microscopic correlates in the bone marrow (femur), liver, or spleen.

 

Administration of the test substance at dose levels as high as 20 mg/kg/day did not result in gross or microscopic lesions in the bone marrow (femur), liver, or spleen.

 

Fetal body weight averages were slightly reduced (96% of the control group value) in the 20 mg/kg/day dose group, the highest dose tested on study. No other ovarian/uterine examination or litter parameters were affected by treatment with test substance. No fetal gross external, soft tissue, or skeletal alterations (malformations or variations) were caused by administration of test substance at dose levels as high as 20 mg/kg/day. The average number of ossification sites per litter was also comparable among the 5 dose groups and did not significantly differ.

 

In conclusion, administration of C6-Pyrazole hemisulfate to female Crl:CD(SD) rats by oral gavage during gestation Days 6 to 20 at dose levels of 0, 2.5, 5, 8 and 20 mg/kg bw/day resulted in a NOAEL of 8 mg/kg bw/day for both maternal toxicity and developmental toxicity.

This developmental toxicity study is classified as acceptable and satisfies the OECD Guideline 414 requirement.