2H-1-Benzopyran, 6-fluoro-3,4-dihydro-2-[(2S)-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:

2016-12-06 to 2016-12-14

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:

Official Journal of the European Union No. L142, 31 May 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:

(2S)-6-fluoro-2-[(2S)-oxiran-2-yl]chromane [S-(R*,R*)]

EC Number:

603-314-1

Cas Number:

129050-23-3

Molecular formula:

C11H11FO2

IUPAC Name:

(2S)-6-fluoro-2-[(2S)-oxiran-2-yl]chromane [S-(R*,R*)]

Test material form:

liquid: viscous

Details on test material:

- Physical state: liquid (viscous)
- Appearance: clear viscous liquid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: I16DB1991
- Expiration date of the lot/batch: 2018-06-07 (retest date)
- Date of manufacture: 2016-04-26
- Purity: 98.0 %

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 (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 / strain

Species / strain 1

Species / strain / cell type:

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

Additional strain / cell type characteristics:

not applicable

Species / strain 2

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: Without S9-mix: 17, 52, 164, 512, 1000 and 1600 μg/plate; With S9-mix: 17, 52, 164, 512, 1000, 1600 and 5000 μg/plate.

Since the test item was soluble at 50 mg/ml (= 5000 μg/plate), this dose level was selected as the maximum final concentration for the dose range finding test.
Based on the toxicity of the test item in the dose range finding test, 1600 and 5000 µg/plate were selected as the highest dose levels in the absence and presence of S9-mix, respectively.

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 and ethanol, the test item was soluble at 50 mg/ml (= 5000 μg/plate). Since DMSO is the preferred vehicle, DMSO was selected as vehicle and 5000 μg/plate was selected as the maximum final concentration for the dose range finding test.

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

Without S9; 5 μg/plate (TA1535)

Controls 2

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; 2.5 μg/plate (TA1537)

Controls 3

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

Without S9; 10 μg/plate (TA98)

Controls 4

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

Without S9; 650 μg/plate (TA100)

Controls 5

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; 10 μg/plate (WP2uvrA)

Controls 6

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

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium; 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 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: 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

Rationale for test conditions:

Recommended test system in international guidelines (e.g. OECD and EC).
Solubility limitations: Since the test item was fully soluble in DMSO, the highest tested concentration for the Mutation assay was 5000 μg/plate.

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 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.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

S. typhimurium, other: TA98, TA100, TA1535, TA1537 bacteria

Metabolic activation:

with and without

Genotoxicity:

positive

Remarks:

Without S9-mix: increases up to 18-fold in TA1535 and up to 7.0-fold in TA100. With S9-mix: increases up to 5.0-fold in TA1535 and up to 7.1-fold in TA100

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

in all strains in the presence and absence of S9-mix

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

positive

Remarks:

increase in the number of revertant colonies up to 4.5-fold (absence of S9-mix) and up to 3.8-fold (presence of S9-mix).

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

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:
Dose range finding test: at the start and at the end of the incubation period at the concentration of 5000 μg/plate, except in tester strain TA100 in the absence of S9-mix, where no precipitation was observed at the end of the incubation period.
Mutation experiment: at the start of the incubation period at the concentration of 5000 μg/plate and at the end of the incubation period at 1600 and 5000 μg/plate in the tester strains TA1535 and TA1537 in the presence of S9-mix, and at 512 μg/plate and above in tester strain TA1535 in the absence of S9-mix.

RANGE-FINDING/SCREENING STUDIES:
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 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%)
- Positive historical control data: The 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.
- Negative (solvent/vehicle) historical control data: The vehicle control values were within the laboratory historical control data ranges, except the response for TA100 in the absence of S9-mix. Since the mean number of revertant colonies showed a slightly higher number of revertant colonies (161 revertant colonies) when compared against relevant historical control data (156 revertant colonies), the validity of the test was not considered to be affected.

ADDITIONAL INFORMATION ON CYTOTOXICITY:
- Other observations when applicable: Cytotoxicity, as evidenced by a decrease in the number of revertants, reduction of the bacterial background lawn and/or the presence of microcolonies, 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.

Any other information on results incl. tables

Mutagenicity

In the absence of S9-mix, the test item induced dose related increases in the number of revertant colonies in various tester strains. The increase observed in tester strain TA1535 was above the laboratory historical control data range, and was up to 18-fold the concurrent control. The increase observed in tester strain TA100 was above the laboratory historical control data range and was up to 7.0-fold the concurrent control. The increase observed in tester strain WP2uvrA was above the laboratory historical control data range and was up to 3.8-fold the concurrent control.

In the presence of S9-mix, the test item induced dose related increases in the number of revertant colonies in various tester strains. The increase observed in tester strain TA1535 was above the laboratory historical control data range, and was up to 5.0-fold the concurrent control. The increase observed in tester strain TA100 was above the laboratory historical control data range and was up to 7.1-fold the concurrent control. The increase observed in tester strain WP2uvrA was above the laboratory historical control data range and was up to 4.5-fold the concurrent control.

Applicant's summary and conclusion

Conclusions:

Interpretation of the results: positive with and without metabolic activation in strains TA100, TA1535 and WP2uvrA
The test item did not induce a significant dose-related increase in the number of revertant colonies in tester strains TA1537 and TA98.
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.