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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2021
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2021
Report date:
2021

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
GLP compliance:
yes (incl. QA statement)
Type of assay:
in vitro mammalian chromosome aberration test

Test material

Constituent 1
Chemical structure
Reference substance name:
Dimethyl 2-[[1-[[(2,3-dihydro-2-oxo-1H-benzimidazol-5-yl)amino]carbonyl]-2-oxopropyl]azo]terephthalate
EC Number:
252-650-1
EC Name:
Dimethyl 2-[[1-[[(2,3-dihydro-2-oxo-1H-benzimidazol-5-yl)amino]carbonyl]-2-oxopropyl]azo]terephthalate
Cas Number:
35636-63-6
Molecular formula:
C21H19N5O7
IUPAC Name:
dimethyl 2-({2-oxo-1-[(2-oxo-2,3-dihydro-1H-benzimidazol-5-yl)carbamoyl]propyl}diazenyl)terephthalate
Test material form:
solid: nanoform

Method

Species / strain
Species / strain / cell type:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Metabolic activation system:
Arocalor
Test concentrations with justification for top dose:
Based on these observations and preliminary cytotoxicity test results, it was decided to test up to a maximum of 250 µg/mL in the presence and absence of metabolic activation with the 3-hour exposure and in the absence of metabolic activation with the 21-hours exposure period in the chromosomal aberration assay.
Vehicle / solvent:
Sterile water
Controls
Untreated negative controls:
yes
Positive controls:
yes
Positive control substance:
cyclophosphamide
ethylmethanesulphonate
Details on test system and experimental conditions:
Chinese Hamster (Cricetulus griseus) ovary cell line CHO-K1, (ATCC CCL-61, Lot 63830396) with a doubling time approximately 12 -14 hours and modal chromosome number of 20 was used as the test system.

The cell line was tested for mycoplasma in the testing facility. The karyotype analysis of this cell line was periodically performed and documented.
Cells were grown in T- 25 cm2 and T-75 cm2 flasks at 37 ± 1 °C in a carbon dioxide incubator (5 ± 0.2 % CO2 in air)
Evaluation criteria:
Metaphases of all concentrations of the test item, the positive and vehicle control cultures were scored.
Statistics:
Statistical analysis of the experimental data was carried out using validated SYSTAT Statistical package ver.12.0. Data were analyzed for proportions of aberrant metaphases in each sample excluding gaps as aberrations. Pooled data from each test concentration and the positive control were compared with the vehicle control using Fischer exact test. All analysis and comparisons were evaluated at 5 % (p < 0.05) level.

Results and discussion

Test results
Key result
Species / strain:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity, but tested up to precipitating concentrations
Vehicle controls validity:
valid
Positive controls validity:
valid

Applicant's summary and conclusion

Conclusions:
The test item, C.I. Pigment Yellow 175 was not clastogenic in CHO-K1 cells at the tested concentration and under the conditions of testing employed.
Executive summary:

The clastogenic potential of the test item, C.I. Pigment Yellow 175 to induce chromosomal aberrations in mammalian cells was evaluated using cultured Chinese Hamster Ovary (CHO-K1) cells in the presence and absence of an exogenous metabolic activation system (S9 fraction prepared from Aroclor 1254 induced rat liver).


 


The study consisted of a preliminary cytotoxicity test and a chromosome aberration assay. Chromosome aberration assay consisted of three independent experiments: Experiments 1 and 2 in the presence and absence of metabolic activation system with 3-hour exposure, respectively, and Experiment 3 in the absence of metabolic activation system with 21-hour exposure.


 


The test item formed a free flowing suspension in sterile water at 200 mg/mL and a pasty suspension in DMSO at 200 mg/mL. Hence, sterile water was selected as the vehicle of choice for the chromosomal aberration test.


 


In a preliminary cytotoxicity test for the selection of test concentrations for the chromosomal aberration assay, the test item did not exhibit the required level of cytotoxicity (reduction in the cell growth by 55± 5 % of the concurrent vehicle control)up to the highest tested concentration of 250µg/mL,both, in the presence and absence of metabolic activation (short term treatment) and in the absence of metabolic activation (long term treatment).


 


Based on these observations and preliminary cytotoxicity test results, it was decided to test up to a maximum of 250 µg/mL in thepresence and absence of metabolic activation with the 3-hour exposure and in the absence of metabolic activation with the 21-hours exposure period in the chromosomal aberration assay.


 


In the chromosomal aberration assay, CHO-K1 cells were exposed to the test item in duplicate at the concentrations of 15.63, 62.5 and 250mg/mL in Experiments 1, 2 and 3 of the chromosomal aberration assay. Concurrent vehicle (SW) and positive controls (cyclophosphamide monohydrate in the presence of metabolic activation and ethyl methanesulfonate in the absence of metabolic activation at 21 hour exposure) were also tested in duplicate. In each case, the cells in C-metaphase were harvested at approximately 21 hours after the start of the treatment and slides were prepared for chromosomal analysis.


 


At the highest concentrations tested, the reduction in cell growth as RICC was 47, 43 and 53 % in experiments 1, 2 and 3, respectively, compared to the vehicle control.


 


A total of 300 metaphases each from the SW control, each treatment level and the positive controls were evaluated for chromosomal aberrations.


 


There was no evidence of statistically significant induction of chromosomal aberrations, excluding gaps, either in the presence or in the absence of metabolic activation. In each of these experiments, under identical conditions, the respective positive control substances produced a large and statistically significant increase in aberrant metaphases.


The study indicated that the test item, C.I. Pigment Yellow 175 was not clastogenic at the concentrations tested and under the conditions of testing