2H-1-Benzopyran, 6-fluoro-3,4-dihydro-2-[(2R)-2-oxiranyl]-, (2S)-

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-08-14 to 2017-08-24

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 guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

July 21, 1997

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Version / remarks:

May 31, 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

(+)-(S,R)-6-fluoro-3,4-dihydro-2-(2-oxiranyl)-2H-1-benzopyran

EC Number:

606-374-7

Cas Number:

197706-51-7

Molecular formula:

C11H11FO2

IUPAC Name:

(+)-(S,R)-6-fluoro-3,4-dihydro-2-(2-oxiranyl)-2H-1-benzopyran

Test material form:

other: wax

Details on test material:

Physical state: wax form
Appearance: clear, viscous, wax

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: I17EB1781
- Expiration date of the lot/batch: 2018-11-17 (retest date)
- Purity test date: 2018-08-30
- Purity 98.8% (Assay GC)

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

OTHER SPECIFICS: During the performance of the study, the test item was handled with a correction factor of 1.00 to correct for the purity/composition. In the course of the study it has been identified that the test item should be corrected for the purity/composition with a factor of 1.15. Therefore, the actual concentrations were 13.04% lower than stated in the report. The conclusion of this report remains unchanged.

Method

Target gene:

Histidine locus (histidine-dependent S. typhimurium strains); Tryptophan locus (tryptophan-dependent E. coli strains)

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Details on mammalian cell type (if applicable):

not applicable

Additional strain / cell type characteristics:

not specified

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Details on mammalian cell type (if applicable):

not applicable

Additional strain / cell type characteristics:

not specified

Cytokinesis block (if used):

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:

5000 µg/plate was selected as the maximum final concentration for the dose range finding test (maximum dose recommended by guideline)
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% S9-mix

The top dose for the mutation experiment was selected based on the results of the dose range finding test.
Mutation experiment: 17, 52, 164, 512, 1600 and and 5000 μg/plate in TA1535, TA1537 and TA98 with and without 5% S9-mix

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- 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.

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

Without S9-mix; 5 μg/plate (TA1535)

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: OCR-191

Remarks:

Without S9-mix; 2.5 μg/plate (TA1537)

Controls 3

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

Without S9-mix; 10 μg/plate (TA98)

Controls 4

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

Without S9-mix; 650 μg/plate (TA100)

Controls 5

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

Without S9-mix; 10 μg/plate (WP2uvrA)

Controls 6

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

2.5 μg/plate (TA1535 and TA1537 with 5% S9-mix), 1μg/plate (TA98 and TA100 with 5% S9-mix), 15 μg/ plate (WP2uvrA with 5 S9-mix)

Details on test system and experimental conditions:

NUMBER OF REPLICATIONS:
- Number of cultures per concentration (single, duplicate, triplicate): triplicate
- Number of independent experiments: 1


METHOD OF APPLICATION
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 or 0.025 ml of a dilution of the test item in DMSO or THF, respectively and
- either 0.5 ml S9-mix (in case of activation assays) or 0.5 ml 0.1 M phosphate buffer (in case of nonactivation 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
- Exposure duration/duration of treatment: 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); tryptophane (tryptophan-dependent E. coli strains)

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.

In addition to the criteria stated above, 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.

Statistics:

No formal hypothesis testing was done.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium, other: TA1537 and TA98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Test results 2

Species / strain:

S. typhimurium, other: TA1535 and TA100

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

valid

Test results 3

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

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:
In the dose range finding test, precipitation of the test item on the plates was observed at the start of the incubation period at the concentration of 5000 µg/plate and was not observed at the end of the incubation period.
In the mutation experiment, precipitation of the test item on the plates was not observed at the start or at the end of the incubation period.

RANGE-FINDING/SCREENING STUDIES: In the dose range finding test, the test item was tested in the tester strains TA100 and WP2uvrA at concentrations of 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 µg/plate in the absence and presence of S9-mix. The dose range finding study is reported as a part of the mutation experiment.

STUDY RESULTS
- Concurrent vehicle negative and positive control data: 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.

Ames test:
- Signs of toxicity:
Cytotoxicity, as evidenced by a decrease in the number of revertants and/or a reduction of the bacterial background lawn, was observed in tester strains TA100, TA1535, TA1537 and TA98 in the absence and presence of S9-mix. In tester strain WP2uvrA, no toxicity was observed at any of the dose levels tested.
- Individual plate counts
- Mean number of revertant colonies per plate and standard deviation

In tester strain TA100, the test item induced up to 11- and 8.3-fold, dose related, increases in the number of revertant colonies compared to the solvent control in the absence and presence of S9-mix, respectively.
In tester strain WP2uvrA, the test item induced up to 5.6- and 5.4-fold, dose related, increases in the number of revertant colonies compared to the solvent control in the absence and presence of S9-mix, respectively.
In tester strain TA1535, the test item induced up to 13- and 4.6-fold, dose related, increases in the number of revertant colonies compared to the vehicle control in the absence and presence of S9-mix, respectively.
All the increases described above were above the laboratory historical control data 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:

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.