1H-1,2,4-Triazole-1-carboxamide, 4-amino-N-(1,1-dimethylethyl)-4,5-dihydro-3-(1-methylethyl)-5-oxo-

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 February 19957 - 14 March 1997

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Only a single test material dose group used, not applicable with current guidance

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

(1983)

Deviations:

yes

Remarks:

, only a single test material dose group used, not applicable with current guidance

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

(1992)

Deviations:

yes

Remarks:

, only a single test material dose group used, not applicable with current guidance

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5395 (In Vivo Mammalian Cytogenetics Tests: Erythrocyte Micronucleus Assay)

Version / remarks:

(1996)

Deviations:

yes

Remarks:

, only a single test material dose group used, not applicable with current guidance

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

4-amino-N-tert-butyl-5-oxo-3-(propan-2-yl)-4,5-dihydro-1H-1,2,4-triazole-1-carboxamide

EC Number:

603-373-3

Cas Number:

129909-90-6

Molecular formula:

C10H19N5O2

IUPAC Name:

4-amino-N-tert-butyl-5-oxo-3-(propan-2-yl)-4,5-dihydro-1H-1,2,4-triazole-1-carboxamide

Details on test material:

- Name of test material (as cited in study report): MKH 3586
- Physical state: powder
- Analytical purity: 98.1%
- Impurities (identity and concentrations):
- Purity test date: 4 Dec 1996
- Lot/batch No.: 05362/0005 (mixed batch)
- Expiration date of the lot/batch:2 Jun 1997

Test animals

Species:

mouse

Strain:

other: Hsd/Win: NMRI

Sex:

male/female

Administration / exposure

Route of administration:

intraperitoneal

Duration of treatment / exposure:

Single administration

Frequency of treatment:

Single administration

Post exposure period:

16, 24 and 48 hrs

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 100 mg/kg
Basis:
nominal conc.

No. of animals per sex per dose:

5 animals/sex/dose

Control animals:

yes, concurrent vehicle

Examinations

Tissues and cell types examined:

Micronuclei within polychromatic erthyrocytes (PCE) analysed for endpoint assessment and PCE and normochromatic erthyrocyte cells analysed for toxicity assessment

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

RANGE-FINDING TEST:

Four males were dosed at 160, 200, 1000 and 5000 mg/kg. Animals were sacrificed at 3 days post the end of dosing. The following deaths were observed 0/4, 1/4, 4/4 and 4/4 respectively. The MTD was determined to be 160 mg/kg, however, in spite of the death observed a maximum dose of 200 mg/kg was selected for the micronucleus assay.

 

MICRONUCLEUS ASSAY

Clinical observations:

No mortalities were observed in the main experiment. Clinical signs reported were similar to those already noted in the RF.

 

PCE ratio:

No evidence of cytotoxicity was observed.

 

Micronucleated polychromatic erythrocytes (MN PCE):

Analysis of the mean MN PCE group data individually and combined indicated that there was no statistically significant increases in MN PCE frequency compared to concurrent control values for either sex (or combined). Individual animal and group mean MN PCE frequencies were consistent with both the concurrent vehicle control values and the historical control. Data from the 16hr time point has been discarded and not reported as the sampling time is too short for an affect to be observed in the proliferating bone marrow, as recognised by current guidance. Positive control treatment induced the appropriate response.

 

Table 7.6.2 -1: Summary of micronucleus results in male and female mice (24 and 48hr sample)

Dose (mg/kg)	Sex	Harvest	No. of PCE	Mean %MN PCE / 1000 PCE	Mean %PCE
Vehicle	Male	24	5000	2.6	45.7
	Female	24	5000	1.8	36.5
		Mean	10000	2.2 ±1.4	41.1
MKH 3586 (100)	Male	24	5000	2.0	40.2
	Female	24	5000	2.2	41.72
		Mean	10000	2.1 ± 1.2	41.0
MKH 3586 (100)	Male	48	5000	2.2	40.1
	Female	48	5000	1.2	37.4
		Mean	10000	1.7 ± 1.2	38.8
CPA (20)	Male	24	5000	21.4	49.0
	Female	24	5000	13.6	52.4
		Mean	10000	17.5 ± 6.5 *	50.7

* p<0.05

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Based on the results from this study MKH 3586 did not exhibitin vivomammalian genotoxicity in male or female mouse bone marrow cells when tested up to a dose of 100 mg/kg (considered to exceed the MTD), despite the deficiencies in the study design (i.e. only a single test material dose group, rather than the required 3 dose levels).

Executive summary:

In a bone marrow micronucleus assay using Hsd/Win: NMRI mice, a single administeredipdose of MKH 3586 tech was administered to groups of male and female animals, employing a dose volume of 10 mL/kg. Doses were selected from a pilot toxicity study where the MTD was deemed to be 100 mg/kg.

 

Mice were treated MKH 3586 at a single dose of 100 mg/kg and sampled at 24 and 48 hours. A negative control group was treated with vehicle only (0.5% Cremophor), and positive control group was treated with cyclophosphamide (CPA, 20 mg/kg) and sampled at 24 hours. A further sample time of 16 hours was also utilised, however as this sample time is considered too early, data from this sample time point has not been reported. Slides of bone marrow cells were prepared from five animals/sex/time point for each group and scored for the occurrence of micronucleated polychromatic erythrocytes (MN PCE) and PCE/total erythrocyte ratios.

 

Whilst no mortality was observed, clinical signs of toxicity reported in the micronucleus test were similar to those observed in the dose range finding experiment (splayed hind legs, rough coat etc).

 

Analysis of the mean MN PCE group data from the first experiment indicated that there was no statistically significant increases MN PCE frequency compared to concurrent control values for either sex. Individual animal and group mean MN PCE frequencies were consistent with both the concurrent vehicle control values and the historical control. Positive control treatment induced the appropriate response

 

Based on the results from this study MKH 3586 did not exhibitin vivomammalian genotoxicity in male or female mouse bone marrow cells when tested up to a dose of 100 mg/kg (considered to exceed the MTD), despite the deficiencies in the study design (i.e. only a single test material dose group, rather than the required 3 dose levels).