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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:
2018-02-20 - 2017-11-27
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
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
liquid

Method

Species / strainopen allclose all
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
post mitochondrial supernatant (S9 fraction) prepared from the livers of phenobarbital/β-naphthoflavone-induced rats.
Test concentrations with justification for top dose:
Concentrations were selected on the basis of the Preliminary Solubility Test and Preliminary Range Finding Test (Informatory Toxicity Test). In the Initial Mutation Test and Confirmatory Mutation Test, the different concentrations were used.
Preliminary Compatibility Test
The solubility of the test item was examined using Distilled water, N,N-Dimethylformamide (DMF) and Dimethyl sulfoxide (DMSO). Partial dissolution was observed at 100 mg/mL concentration using DMSO and DMF. Test item was soluble at the same concentration using Distilled water after approximately 3 minutes vortex. Therefore, Distilled water was selected as vehicle (solvent) for the study.
Preliminary Concentration Range Finding Test (Informatory Toxicity Test)
Based on the solubility test, a 100 mg/mL stock solution was prepared in Distilled water. Seven test concentrations were prepared by successive dilutions of the stock solution, spaced by factors of 2, 2.5 and approximately √10. The revertant colony numbers and the inhibition of the background lawn of auxotrophic cells of two of the tester strains (Salmonella typhimurium TA98 and TA100) were determined at concentrations of 5000, 2500, 1000, 316, 100, 31.6 and 10 μg/plate of the test item, in the absence and presence of metabolic activation. In the Preliminary Concentration Range Finding Test the plate incorporation method was used.
Test Item Concentrations in the Mutagenicity Tests (Initial Mutation Test and Confirmatory Mutation Test)
Based on the results of the preliminary tests, a 100 mg/mL stock solution was prepared in Distilled water. Maximum seven test concentrations were prepared by successive dilutions of the stock solution, to obtain lower doses. The maximum test concentration
was 5000 μg test item/plate. Examined concentrations in the Initial Mutation Test were 5000, 1581, 500, 158.1, 50 and 15.81 μg/plate. Examined concentrations in the Confirmatory Mutation Test were 5000, 1581, 500, 158.1, 50, 15.81 and 5 μg/plate.
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Distilled water
- Justification for choice of solvent/vehicle: The solubility of the test item was examined using Distilled water, N,N-Dimethylformamide (DMF) and Dimethyl sulfoxide (DMSO). Partial dissolution was observed at 100 mg/mL concentration using DMSO and DMF. Test item was soluble at the same concentration using Distilled water after approximately 3 minutes vortex. Therefore, Distilled water was selected as vehicle (solvent) for the study.
Controls
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
distilled water and DMSO
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
sodium azide
methylmethanesulfonate
other: 4-nitro-1,2-phenylenediamine (NPD), 2-aminoanthracene (2AA)
Details on test system and experimental conditions:
METHOD OF APPLICATION: The study included a Preliminary Compatibility Test, a Preliminary Concentration Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test and a Confirmatory Mutation Test. In the Preliminary Concentration Range Finding Test as well as in the Initial Mutation Test, the plate incorporation method was used. In the Confirmatory Mutation Test, the pre-incubation method was used.
- Cell density at seeding (if applicable): Not applicable
DURATION
- Preincubation period: 20 min at 37ºC
- Exposure duration: 48±1 hours at 37ºC
- Expression time (cells in growth medium): N/A
- Selection time (if incubation with a selection agent): N/A
- Fixation time (start of exposure up to fixation or harvest of cells): N/A
SELECTION AGENT (mutation assays): N/A
SPINDLE INHIBITOR (cytogenetic assays): N/A
STAIN (for cytogenetic assays): N/A
NUMBER OF REPLICATIONS: In the main tests, each sample (including the controls) was tested in triplicate.
METHODS OF SLIDE PREPARATION AND STAINING TECHNIQUE USED: N/A
NUMBER OF CELLS EVALUATED: N/A
CRITERIA FOR MICRONUCLEUS IDENTIFICATION: N/A
DETERMINATION OF CYTOTOXICITY: N/A
OTHER EXAMINATIONS:
- Determination of polyploidy: N/A
- Determination of endoreplication: N/A
- Methods, such as kinetochore antibody binding, to characterize whether micronuclei contain whole or fragmented chromosomes (if applicable): N/A
Evaluation criteria:
The colony numbers on the untreated / negative (solvent) / positive control and test item treated plates were determined by manual counting. Visual examination of the plates was also performed; precipitation or signs of growth inhibition (if any) were recorded and reported. The mean number of revertants per plate, the standard deviation and the mutation factor* values were calculated for each concentration level of the test item and for the controls using Microsoft ExcelTM software.

Criteria for Validity:
The study was considered valid if:
- the number of revertant colonies of the negative (vehicle/solvent) and positive controls were in the historical control range in all strains of the main tests;
- at least five analyzable concentrations were presented in all strains of the main tests.

Criteria for a Positive Response:
A test item was considered mutagenic if:
- a dose–related increase in the number of revertants occurred and/or;
- a reproducible biologically relevant positive response for at least one of the dose groups occurred in at least one strain with or without metabolic activation.

An increase was considered biologically relevant if:
- the number of reversions is more than two times higher than the reversion rate of the negative (so lvent) control in Salmonella typhimurium TA98, TA100 and Escherichia coli WP2 uvrA bacterial strains;
- the number of reversions is more than three times higher than the reversion rate of the negative (solvent) control in Salmonella typhimurium TA1535 and TA1537 bacterial strains.

Criteria for a Negative Response: The test item was considered to have shown no mutagenic activity in this study if it produces neither
a dose-related increase in the number of revertants nor a reproducible biologically relevant positive response at any of the dose groups, with or without metabolic activation.
Statistics:
No statistics performed.

Results and discussion

Test resultsopen allclose all
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
E. coli WP2
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid

Any other information on results incl. tables

PRELIMINARY RANGE FINDING TEST (INFORMATORY TOXICITY TEST)

In the Preliminary Range Finding Test, the plate incorporation method was used. The preliminary test was performed using Salmonella typhimurium TA98 and Salmonella typhimurium TA100 tester strains in the presence and absence of metabolic activation system (±S9 Mix) with appropriate untreated, negative (solvent) and positive controls.

Each sample (including the controls) was tested in triplicate.

Following concentrations were examined: 5000, 2500, 1000, 316, 100, 31.6 and 10 μg/plate.

In the preliminary experiment, the numbers of revertant colonies were mostly in the normal range (minor differences were detected in some sporadic cases, but they were without biological significance and considered as biological variability of the test system).

No precipitate was detected on the plates in the preliminary experiment.

Inhibitory or toxic effects of the test item were not detected in the preliminary experiment.

Based on the results of the Range Finding Test and the solubility findings, the maximum final concentration to be tested in the main experiments was 5000 μg/plate.

INITIAL AND CONFIRMATORY MUTATION TESTS

In the Initial Mutation Test, the plate incorporation method was used. In the Confirmatory Mutation Test, the pre-incubation method was used. The Initial Mutation Test and Confirmatory Mutation Test were carried out using four Salmonella typhimurium strains (TA98, TA100, TA1535 and TA1537) and the Escherichia coli WP2 uvrA strain. The Initial Mutation Test and Confirmatory Mutation Test were

performed in the presence and absence of a metabolic activation system. Each test was performed with appropriate untreated, negative (solvent) and positive controls. In the main tests each sample (including the controls) was tested in triplicate.

Based on the results of the preliminary experiment, the examined test concentrations in the Initial Mutation Test were 5000, 1581, 500, 158.1, 50 and 15.81 μg/plate and in the Confirmatory Mutation Test were 5000, 1581, 500, 158.1, 50, 15.81 and 5 μg/plate.

No precipitate was detected on the plates in the main tests in the examined bacterial strains with and without metabolic activation.

No inhibitory, cytotoxic effect of the test item was detected in the main tests in all examined bacterial strains with and without metabolic activation.

In the Initial Mutation Test and Confirmatory Mutation Test, the number of revertant colonies did not show any biologically relevant increase compared to the solvent controls. There were no reproducible dose-related trends and there was no indication of any treatment-related effect.

In the Initial Mutation Test (plate incorporation method), the highest revertant rate was observed in Salmonella typhimurium TA1535 bacterial strain at 158.1 μg/plate concentration without metabolic activation (the observed mutation factor value was: MF: 1.52). However, there was no dose-response relationship, the observed mutation factor values were below the biologically relevant threshold limit and the number of revertant colonies was within the historical control range.

In the Confirmatory Mutation Test (pre-incubation method), the highest revertant rate was observed in Escherichia coli WP2 uvrA bacterial strain at 15.81 μg/plate concentration without metabolic activation (the observed mutation factor value was: MF: 1.25). However, there was no dose-response relationship, the number of revertant colonies did not show any biologically relevant increase compared to the solvent controls and the number of revertant colonies was within the historical control range.

Higher numbers of revertant colonies compared to the vehicle (solvent) control were detected in the main tests in some other sporadic cases. However, no dose-dependence was observed in those cases and they were below the biologically relevant threshold value. The numbers of revertant colonies were within the historical control range in each case, so they were considered as reflecting the biological variability of the test.

Sporadically, lower revertant counts compared to the vehicle (solvent) control were observed in the main tests at some non-cytotoxic concentrations. However, no background inhibition was recorded and the mean numbers of revertant colonies were in the historical control range in all cases, thus they were considered as biological variability of the test system.

Applicant's summary and conclusion

Conclusions:
The test item was tested for potential mutagenic activity using the Bacterial Reverse Mutation Assay. The experiments were carried out using histidine-requiring auxotroph strains of Salmonella typhimurium (Salmonella typhimurium TA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotroph strain of Escherichia coli (Escherichia coli WP2 uvrA) in the presence and absence of a metabolic activation system, which was a cofactor-supplemented post-mitochondrial S9 fraction prepared from the livers of phenobarbital/β-naphthoflavone-induced rats.
The study included a Preliminary Compatibility Test, a Preliminary Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test and a Confirmatory Mutation Test. In the Preliminary Concentration Range Finding Test as well as in the Initial Mutation Test the plate incorporation method was used. In the Confirmatory Mutation Test, the pre-incubation method was used.
The reported data of this mutagenicity assay show that under the experimental conditions applied the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.
In conclusion, the test item Sopromine 1686 has no mutagenic activity in the bacterial strains under the test conditions used in this study.
Executive summary:

The test item, Sopromine 1686, was tested for potential mutagenic activity using the Bacterial Reverse Mutation Assay.

The experiments were carried out using histidine-requiring auxotroph strains of Salmonella typhimurium (Salmonella typhimurium TA98, TA100, TA1535 and TA1537) and the tryptophan-requiring auxotroph strain of Escherichia coli (Escherichia coli WP2 uvrA) in the presence and absence of a post mitochondrial supernatant (S9 fraction) prepared from the livers of phenobarbital/β-naphthoflavoneinduced rats.

The study included a Preliminary Compatibility Test, a Preliminary Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test (Plate Incorporation Method) and a Confirmatory Mutation Test (Pre-Incubation Method). Batch 3900075 of Sopromine 1686 was a creamy white liquid with a purity of 25.1%. All concentrations and dose-levels were expressed as active ingredient content of the test item (a correction factor of 3.98 was used).

Distilled water at a concentration of 100 mg/mL. Concentrations of 5000; 2500; 1000; 316; 100; 31.6 and 10 μg/plate were examined in the Range Finding Test in tester strains Salmonella typhimurium TA100 and TA98 in the absence and presence of metabolic activation. Based on the results of the Range Finding Test, the test item concentrations in the Initial Mutation Test were 5000, 1581, 500, 158.1, 50 and

15.81 μg/plate, in the Confirmatory Mutation Test were 5000, 1581, 500, 158.1, 50, 15.81 and 5 μg/plate.

No precipitate was detected on the plates in the Preliminary Concentration Range Finding Tests and in the main tests in all examined bacterial strains with and without metabolic activation. No inhibitory, cytotoxic effect of the test item was detected in the Preliminary Range Finding Test or in the main tests. The mean values of revertant colonies of the negative (vehicle/solvent) control plates were within the historical control range, the reference mutagens showed the expected increase in the number of revertant colonies, the viability of the bacterial cells was checked by a plating experiment in each test. At least five analyzable concentrations were presented in all strains of the main tests, the examined concentration range was considered to be adequate. The study was considered to be valid.

The reported data of this mutagenicity assay show that under the experimental conditions applied the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used .

In conclusion, the test item Sopromine 1686 (Batch Number: 3900075) has no mutagenic activity in the bacterial strains under the test conditions used in this

study.