Ethanone, 2,2-dichloro-1-(2,3-dihydro-3-methyl-4H-1,4-benzoxazin-4-yl)-

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:

03 March 1986 to 22 September 1986

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant, guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Two part main experiment: In the first part a single dose of 5000 mg/kg was administered to 3 groups of 8 male and 8 female Chinese hamsters. The groups were killed after 16, 24, and 48 hours. Three same sized negative control groups were treated with the vehicle and also killed after 16, 24, or 48 hours. The sensitivity of the test system was checked by treating one further group with 64 mg/kg of the known mutagen Cyclophosphamide (CPA). The animals of this group were killed 24 hours after treatment. Analytical purity: 93.9%

In the second part three groups of 8 male and 8 female hamsters were treated with a single dose of 1250, 2500, or 5000 mg/kg of CGA 154281 and killed after 24 hours. Negative and positive control groups were used. After sacrifice the bone marrow from the shafts of both femurs was removed and smears were prepared on slides. Routinely the slides of five animals/sex/dose were stained with May-Grunwald solution and scored for micronuclei. As an exception, the slides from 3 males and 7 females which were killed after 16 hours (part 1) were scored, since only three males in each group furnished well differentiated cells. From each animal the ratio of polychromatic to normochromatic erythrocytes was determined as an indicator for toxic effects on the erythropoiesis and 1000 polychromatic erythrocytes were scored for micronuclei.

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

2,2-dichloro-1-[(3R)-3-methyl-3,4-dihydro-2H-1,4-benzoxazin-4-yl]ethan-1-one; 2,2-dichloro-1-[(3S)-3-methyl-3,4-dihydro-2H-1,4-benzoxazin-4-yl]ethan-1-one

EC Number:

619-372-6

Cas Number:

98730-04-2

Molecular formula:

C11H11Cl2NO2

IUPAC Name:

2,2-dichloro-1-[(3R)-3-methyl-3,4-dihydro-2H-1,4-benzoxazin-4-yl]ethan-1-one; 2,2-dichloro-1-[(3S)-3-methyl-3,4-dihydro-2H-1,4-benzoxazin-4-yl]ethan-1-one

Test animals

Species:

hamster, Chinese

Strain:

other: Random outbred strain

Sex:

male/female

Details on test animals or test system and environmental conditions:

3 groups each consisting of 8 male and 8 female Chinese hamsters.
TEST ANIMALS
- Age at study initiation: females 6-10 weeks, males 4-9 weeks
- Weight at study initiation: females 22-32 g, males 20-35 g
- Diet: NAFAG No.924
- Water: Tap water ad libitum
- Acclimation period: 4-5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22-23°C
- Humidity: 52-59%
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 03 March 1986 To: 22 September 1986

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

0.5% aqueous carboxymethylcellulose (CMC).

Details on exposure:

Part 1: The different groups of animals were killed after 16, 24, and 48 hours.
Part 2: The different groups of animals were killed after 24 hours.

Duration of treatment / exposure:

16 to 48 hours

Frequency of treatment:

Single dose

Post exposure period:

None.

Doses / concentrations

Remarks:

Doses / Concentrations:
1250, 2500 or 5000 mg/kg
Basis:
nominal conc.

No. of animals per sex per dose:

8

Control animals:

yes, concurrent vehicle

Positive control(s):

Cyclophosphamide (CPA)
- Route of administration: oral gavage
- Doses / concentrations: 64 mg/kg

Examinations

Tissues and cell types examined:

After sacrifice the bone marrow from the shafts of both femurs was removed and smears were prepared on slides.

Details of tissue and slide preparation:

Routinely the slides of five animals/sex/dose were stained with May-Grunwald solution and scored for micronuclei. As an exception, the slides from 3 males and 7 females which were killed after 16 hours (part 1) were scored, since only three males in each group furnished well differentiated cells.

Evaluation criteria:

From each animal the ratio of polychromatic to normochromatic erythrocytes was determined as an indicator for toxic effects on the erythropoiesis and 1000 polychromatic erythrocytes were scored for micronuclei.

Statistics:

Chi-Square test used

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

In both parts of the main experiment all hamsters survived. At all sampling times (16, 24, and 48 hours) and at all dose levels (5000, 2500, and 1250 mg/kg) no statistically significant increase of micronucleated polychromatic erythrocytes (PCEs) was observed when compared to the negative control. In the positive control groups the percentage of micronucleated PCEs was statistically significant increased, thus demonstrating the sensitivity of the test system.

Any other information on results incl. tables

Chinese hamster micronucleus test
Part 1: Percentage of micronucleated PCEs at different preparation times
Test article and concentration	Sex	16 hours	24 hours	48 hours
CGA154281 (5000 mg/kg)	males females mean	0.07 0.06 0.06	0.00 0.08 0.04	0.06 0.06 0.06
Negative control – vehicle (0.5% CMC)	males females mean	0.07 0.04 0.05	0.04 0.04 0.04	0.10 0.04 0.07
Positive control – cyclophoshamide (64 mg/kg)	males females mean		3.68 5.46 4.57*
* p>0.05 (Chi-Square test)

Chinese hamster micronucleus test
Part 2: Percentage of micronucleated PCEs at different dose levels sacrificed after 24 hours
Sex	CGA154281 1250 mg/kg	CGA154281 2500 mg/kg	CGA154281 5000 mg/kg	Negative control 0.5% CMC	Positive control 64 mg/kg CPA
Males Females Mean	0.02 0.00 0.01	0.04 0.02 0.03	0.04 0.06 0.05	0.08 0.02 0.05	2.00 1.58 1.79*
* p > 0.05 (Chi-Square Test)

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Under the given experimental conditions no evidence for a clastogenic or aneugenic activity of CGA154281 was observed in vivo.

Executive summary:

CGA154281 technical, Benoxacor, was administered by gavage to Chinese hamsters to evaluate any mutagenic activity on polychromatic erythrocytes in bone marrow cells, in vivo. In the first experiment the highest dose of 5000 mg/kg was administered and animals sacrificed 16, 24 or 48 hours later. In the second assay, doses of 1250, 2500 and 5000 mg/kg were administered and animals sacrificed after 24 hours exposure.

In the first assay, bone marrow smears showed no significant increase in micronucleated polychromatic erythrocytes.

In the second assay, bone marrow smears showed no significant increase in micronucleated polychromatic erythrocytes.

No evidence of mutagenic effects were found in the Chinese hamster after oral administration of Benoxacor.