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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-12-19 to 2017-01-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
July 21, 1997
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
Official Journal of the European Union No. L142, 31 May 2008.
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid: viscous
Details on test material:
- Physical state: Viscous liquid
- Appearance: Yellow to orange, clear liquid
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: I16HB3197
- Expiration date of the lot/batch: 2017-05-08 (retest date)
- Purity: 98.2%
- Date of manufacture: 2016-08-11

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: Not indicated
- Solubility and stability of the test substance in the solvent/vehicle: Not indicated

During the performance of the study, the test item was handled with a correction factor of 1.00 (as initially communicated by the sponsor). After the end of the study performance, it has been identified that the test item should be corrected for the purity/composition with a factor of 1.23. Therefore, the actual concentrations were 18.6% lower than stated in the report.

Method

Target gene:
Histidine locus (histidine-dependent S. typhimurium strains); Tryptophan locus (tryptophan-dependent E. coli strains)
Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
not applicable
Species / strain / cell type:
E. coli WP2 uvr A
Additional strain / cell type characteristics:
not applicable
Metabolic activation:
with and without
Metabolic activation system:
S9-mix (Aroclor 1254 induced rat liver metabolic activation system)
Test concentrations with justification for top dose:
Dose-range finding test: 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 μg/plate in TA100 and WP2uvrA with and without 5% (v/v) S9-mix (top dose selected based on the solubility findings)
Mutation experiment: 1.7, 5.4, 17, 52, 164 and 512 µg/plate in TA1535, TA1537 and TA98 with and without 10% (v/v) S9-mix (top dose selected based on the toxicity observed in the dose-range finding test)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO (dimethyl sulfoxide)
- Justification for choice of solvent/vehicle: The test item was observed to be insoluble in water at 50 mg/ml. In DMSO, the test item was soluble at 50 mg/ml (= 5000 μg/plate). Based on these solubility findings, DMSO was selected as vehicle and 5000 μg/plate was selected as the maximum final concentration for the dose range finding test.
Controlsopen allclose all
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
Without S9-mix; 5 μg/plate (TA1535)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: ICR-191
Remarks:
Without S9-mix; 2.5 μg/plate (TA1537)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
Without S9-mix; 10 μg/plate (TA98)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
Without S9-mix; 650 μg/plate (TA100)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
4-nitroquinoline-N-oxide
Remarks:
Without S9-mix; 10 μg/plate (WP2uvrA)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene
Remarks:
With S9-mix; 2.5μg/plate (TA1535 with 5 and 10% S9-mix, TA1537 with 5% S9-mix), 5μg/plate (TA1537 with 10% S9-mix), 1μg/plate (TA98 with 5 and 10% S9-mix, TA100 with 5% S9-mix), 2μg/plate (TA100 with 10% S9-mix), 15μg/plate (WP2uvrA with 5 and 10% S9-mix)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation):
Top agar in top agar tubes was melted by heating to 45 ± 2°C.
The following solutions were successively added to 3 ml molten top agar:
- 0.1 ml of a fresh bacterial culture (10^9 cells/ml) of one of the tester strains
- 0.1 ml of a dilution of the test item in DMSO and
- either 0.5 ml S9-mix (in case of activation assays) or 0.5 ml 0.1 M phosphate buffer (in case of non activation assays).
The ingredients were mixed on a Vortex and the content of the top agar tube was poured onto a selective agar plate. After solidification of the top agar, the plates were inverted and incubated in the dark at 37.0 ± 1.0 °C for 48 ± 4 h. After this period revertant colonies were counted.

DURATION
- Preincubation period: 48 ± 4 h
- Selection time (if incubation with a selection agent): 48h (simultaneous with exposure)


SELECTION AGENT (mutation assays): Histidine (S. typhimurium histidine-dependent strains); Tryptophan (E. coli tryptophan-dependent strains)

NUMBER OF REPLICATIONS: all concentrations for all experiments were tested in triplicate

DETERMINATION OF CYTOTOXICITY
- Method: Reduction in bacterial background lawn; increase in size of the microcolonies; reduction of revertant colonies
Evaluation criteria:
A test item is considered negative (not mutagenic) in the test if:
a) The total number of revertants in the tester strain TA100 or WP2uvrA is not greater than two (2) times the concurrent vehicle control, and the total number of revertants in tester strains TA1535, TA1537 or TA98 is not greater than three (3) times the concurrent vehicle control.
b) The negative response should be reproducible in at least one follow-up experiment.

A test item is considered positive (mutagenic) in the test if:
a) The total number of revertants in tester strain TA100 or WP2uvrA is greater than two (2) times the concurrent vehicle control, or the total number of revertants in tester strain TA1535, TA1537 or TA98 is greater than three (3) times the concurrent vehicle control.
b) A concentration related effect is observed.
c) In case a follow up experiment is performed when a positive response is observed in one of the tester strains, the positive response should be reproducible in at least one follow up experiment.
Statistics:
No formal hypothesis testing was done.
In addition to the criteria stated below, any increase in the total number of revertants was evaluated for its biological relevance including a comparison of the results with the historical control data range.

Results and discussion

Test resultsopen allclose all
Species / strain:
other: TA100, TA1535
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
other: TA98, TA1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Water solubility: The test item was observed to be insoluble in water at 50 mg/ml.
- Precipitation: Precipitation of the test item on the plates was observed at the start of the incubation period at the concentration of 5000 μg/plate. No precipitation was observed at the end of the incubation period.

RANGE-FINDING/SCREENING STUDIES: In the dose-range finding test, the test item was tested at a concentration range of 1.7 to 5000 μg/plate in the absence and presence of 5% (v/v) S9-mix in the tester strains TA100 and WP2uvrA. The dose range finding study with the two tester strains TA100 and
WP2uvrA, is reported as a part of the mutation experiment. In compliance with the OECD guideline No. 471, there is no requirement for verification of a clear positive response. Since the test results of the mutation experiment showed clear positive responses, the follow-up experiment was not performed.

HISTORICAL CONTROL DATA (with ranges, means and standard deviation and confidence interval (e.g. 95%)
The vehicle and strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
- Measurement of cytotoxicity used: the reduction of the bacterial background lawn, the increase in the size of the microcolonies and the reduction of the revertant colonies were examined.
Cytotoxicity was observed in all five tester strains in the absence and presence of S9-mix.

Any other information on results incl. tables

Mutagenicity

In the absence of S9-mix, the test item induced up to 30-fold increases in the number of revertant colonies compared to the concurrent vehicle control in tester strain TA1535, up to 3.3-fold increases in tester strain TA100 and up to 5.5-fold increases in tester strain WP2uvrA.

In the presence of S9-mix, the test item induced up to 37-fold increases in the number of revertant colonies compared to the concurrent vehicle control in tester strain TA1535, up to 4.0-fold increases in tester strain TA100 and up to 6.3-fold increases in tester strain WP2uvrA.

All the increases observed were above the laboratory historical control range.

The test item did not induce a significant dose-related increase in the number of revertant colonies in tester strains TA1537 and TA98.

Applicant's summary and conclusion

Conclusions:
Interpretation of the results:
positive with and without metabolic activation

Based on the results of this study it is concluded that the test item is mutagenic in the Salmonella typhimurium reverse mutation assay and in the Escherichia coli reverse mutation assay.