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Genetic toxicity in vitro

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Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
of 1997
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
of 2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Metabolic activation system:
liver S9 mix from male Sprague Dawley rats treated with phenobarbital and 5,6-benzoflavone for enzyme induction.
Test concentrations with justification for top dose:
Experiment 1: 0; 5; 15; 50; 150; 500; 1500 and 5000 μg/plate
Experiment 2: 0; 50; 150; 500; 1500 and 5000 μg/plate
Vehicle / solvent:
Dimethyl sulphoxide (DMSO)
Justification for choice of solvent/vehicle:
DMSO was a suitable vehicle for exposure to the test substance up to the maximum guideline recommended test substance concentration of 5000 μg/plate.
Negative solvent / vehicle controls:
yes
Remarks:
without and with S9 mix
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: Sodium azide; 9-aminoacridine; 2-nitrofluorene; 4-nitroquinoline-1-oxide.
Remarks:
Positive control substances for tests without metabolic activation (S9 mix). All of them are well established reference mutagens.
Negative solvent / vehicle controls:
yes
Remarks:
without and with S9 mix
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene; Benzo[a]pyrene
Remarks:
Positive control substances for tests with metabolic activation (S9 mix). All of them are well established reference mutagens.
Details on test system and experimental conditions:
Standard Plate Incorporation Tests were performed in Experiment 1 and pre-incubation tests in Experiment 2. Both experiments were conducted without and with metabolic activation (S9 mix). The proportion of S9 fraction in the S9 mix was 10% v/v.

The following positive controls were used to check mutability of the bacteria and activity of the S9 mix:

Without metabolic activation (S9 mix):

Sodium azide (CAS No. 26628-22-8):
- 2 μg/plate, dissolved in DMSO: - strains: TA 1535, TA 100

9-Aminoacridine (CAS No. 90-45-9):
- 50 μg/plate, dissolved in DMSO: - strain: TA 1537

2-Nitrofluorene (CAS No. 607-57-8):
- 2 μg/plate, dissolved in DMSO: - strain: TA 98

4-Nitroquinoline-1-oxide (CAS No. 56-57-5):
- 2 μg/plate, dissolved in DMSO: - strain: WP2 uvrA

With metabolic activation (S9 mix):

2-Aminoanthracene (CAS No. 613-13-8):
- 5 μg/plate, dissolved in DMSO: - strains: TA 1535, TA 100
- 10 μg/plate, dissolved in DMSO: - strain: WP2 uvrA

Benzo[a]pyrene (CAS No. 50-32-8):
- 5 μg/plate, dissolved in DMSO: - strains: TA 1537, TA 98

Evaluation criteria:
The test substance is considered to exhibit mutagenic activity in this assay if the following criteria are met:
A reproducible increase in revertant colony number, (i.e. at least twice for strains TA 100, TA 98 and WP2 uvrA and at least three times for strains TA 1535 and TA 1537 the concurrent vehicle controls), with some evidence of a positive dose-response relationship. Such positive response in at least one tester strain without or with metabolic activation (S9 mix.) is sufficient for concluding mutagenic activity.

A test substance is considered non-mutagenic in this test if:
Exposure to a test substance does not produce a reproducible increase in revertant colony numbers.
Statistics:
The data were not statistically analysed. The study result was unequivocal.
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
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
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
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
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Positive controls validity:
valid
Additional information on results:
All sterility control plates were colony free. Hence the absence of microbial contamination of the S9 mix, buffer and test substance formulation was confirmed. Viability counts were satisfactory meeting the acceptance criteria.
Conclusions:
Interpretation of results : negative without and with metabolic activation (S9 mix)
Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
Version / remarks:
of 1997
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)
Version / remarks:
of 2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5375 - In vitro Mammalian Chromosome Aberration Test
Version / remarks:
of 1998
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: ICH (1996) Guideline S2A: Guidance on Specific Aspects of Regulatory Genotoxicity Tests for Pharmaceuticals.
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: ICH (1998) Guideline S2B: Genotoxicity: A Standard Battery for Genotoxicity Testing of Pharmaceuticals.
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
in vitro mammalian chromosome aberration test
Species / strain / cell type:
lymphocytes:
Details on mammalian cell type (if applicable):
- Source of lymphocytes: Human blood collected aseptically from two healthy, non-smoking male donors and pooled.
- Suitability check: Mitotic index was calculated for each donor and a background control check was performed to asses the frequency
of aberrant metaphases and acceptability of the generated data.
- Type and identity of media:
RPMI 1640 tissue culture medium supplemented with 10% foetal calf serum, 0.2 IU/mL sodium heparin, 20 IU/mL penicillin / 20 μg/mL streptomycin
and 2.0 mM glutamine.
- Properly maintained: yes






Additional strain / cell type characteristics:
not applicable
Metabolic activation:
with and without
Metabolic activation system:
liver S9 mix from male Sprague Dawley derived rats treated with phenobarbital and 5,6-benzoflavone for enzyme induction.
Test concentrations with justification for top dose:
The test substance exhibited cytotoxicity determining the highest concentrations applied.
Vehicle / solvent:
Dimethyl sulphoxide (DMSO)

Justification for choice of solvent/vehicle and maximum test concentration:
DMSO was chosen as a vehicle to maximise exposure of cultures in the test system to WS400123. WS400123 was shown to be miscible in DMSO at 250 mg/mL. This concentration produced a test substance concentration in culture medium of 5000 µg/mL when administering this DMSO test substance solution to the culture medium at 2% v/v. On dosing DMSO test substance solution at 2% v/v into aqueous tissue culture medium, precipitate was not visible by eye at 5000 µg/mL of test substance in final medium, but approximately 5 minutes afterwards the media turned cloudy. At 5000 µg/mL, fluctuation in osmolality and in pH between test substance treated media and vehicle controls were within accepptable limits leading to the choice of 5000 µg/mL as the maximum concentration tested in the present study.


Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
mitomycin C
Details on test system and experimental conditions:
CELL DIVISION STIMULANT:
Phytohaemagglutinin

METHOD OF APPLICATION:
in cell culture medium;

DURATION
- Exposure duration:
3 hours in Experiment 1 (without and with metabolic activation) and in Experiment 2 (with metabolic activation).
21 hours in Experiment 2 (without metabolic activation)
[After the 3 h treatment the cells were cultivated with fresh media for 18 h].
- Concentration of S9 fraction in final medium:
Experiment 1: 2 % v/v
Experiment 2: 5 % v/v
- Fixation time (start of exposure up to fixation or harvest of cells):
21 hours in each of both experiments.

SPINDLE INHIBITOR (cytogenetic assays):
Colcemid® was added to the cultures (0.1 µg/mL culture medium) 19 hours after treatment start.
2 h later, the cells were treated with hypotonic solution (0.075 M KCl) for 10 min at 37 °C. After incubation in the hypotonic solution, the cells were fixed with 3 + 1 methanol + glacial acetic acid.

STAIN (for cytogenetic assays):
After fixation the cells were stained with 10% Giemsa.

NUMBER OF REPLICATIONS:
Duplicate cultures were treated at each concentration.

NUMBER OF CELLS EVALUATED:
100 metaphases per culture, amounting to a total of 200 metaphases per dose concentration, were scored for structural chromosomal aberrations.
This number of 100 metaphases per culture was reduced in cultures showing a high level of aberrant cells, where 10 cells in 100 metaphases with structural aberrations (excluding gaps) were observed.

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index (% cells in mitosis) determined by counting the number of mitotic cells in 1000 cells;

Microscopic examination of the metaphases included the recording of the following parameters:
- Aberrant cells (including and excluding gaps),
- Number of gaps,
- Types of aberrations
Chromatid break, Chromosome break, Chromatid gap, Chromatid exchange, Chromosome exchange, Chromosome gap,
Others: Cells with greater than eight aberrations, pulverised cells and pulverised chromosomes

Determination of polyploidy:
- Polyploid and endoreduplicated cells were noted when seen.
Evaluation criteria:
An assay is considered to be acceptable if the vehicle and positive control values lie within the current historical control range.

The test substance is considered to cause a positive response if the following conditions are met:
-Significant increases (P<0.01) in the frequency of metaphases with aberrant chromosomes (excluding gaps) at one or more test concentration.
-The increases exceed the vehicle control range of this laboratory, taken at the 99% confidence limit.
-The increases are reproducible between replicate cultures.
-The increases are not associated with large changes in pH, osmolality of the treatment medium or extreme toxicity.
-Evidence of a concentration-related response is considered to support the conclusion.

A negative response is claimed if no statistically significant increases in the number of aberrant cells above concurrent control frequencies are observed, at any concentration.
Statistics:
One-tailed Fisher exact test (Fisher 1973) for comparison of the number of aberrant metaphase cells in each test substance concentration group and each positive control group with the vehicle control value.

In addition, a Cochran-Armitage test for trend (Armitage, 1955) was applied to the control and all test substance groups. If this is significant at the 1% level, the test is reiterated excluding the highest concentration group - this process continues until the trend test is no longer significant.

ARMITAGE, P. (1955) Tests for linear trends in proportions and frequencies. Biometrics, 11, 375-386. (Cochran-Armitage test).
FISHER, R.A. (1973) The Exact Treatment of 2 x 2 Table in: Statistical Methods for Research Workers. Hafner Publishing Company, New York.
Key result
Species / strain:
lymphocytes:
Metabolic activation:
without
Genotoxicity:
negative
Remarks:
In both experiments, following 3 h or 21 h continuous treatment
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
In both experiments, following 3 h or 21 h continuous treatment
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
True negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
lymphocytes:
Metabolic activation:
with
Genotoxicity:
negative
Remarks:
In both experiments following 3 h treatment
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
In both experiments following 3 h treatment
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
The only limiting factor regarding the selection of test concentrations was cytotoxicity. PH and osmolality fluctuation were within acceptable limits at the guideline recommended maximum concentration of 5000 µg/mL and precipitate was not visible by eye.

ADDITIONAL OBSERVATIONS DURING METAPHASE ANALYSIS
Statistically significant increases in polyploid metaphases or notable increases in endoreduplicated metaphases were not evident.
Remarks on result:
other: no mutagenic potential
Conclusions:
Interpretation of results : negative Without and with metabolic activation (-/+S9)
Endpoint:
in vitro gene mutation study in mammalian cells
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Version / remarks:
of 1997
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5300 - In vitro Mammalian Cell Gene Mutation Test
Version / remarks:
of 1998
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)
Version / remarks:
of 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
in vitro mammalian cell gene mutation tests using the thymidine kinase gene
Target gene:
TK
Species / strain / cell type:
mouse lymphoma L5178Y cells
Details on mammalian cell type (if applicable):
- Type and identity of media, in general used for cell culture:
R10p, i.e. medium R0 supplemented with 0.1% v/v Synperonic F68, 1.0 mM sodium pyruvate and HiDHS at 10% v/v,
whereby medium R0 is RPMI 1640 buffered with 2 mg/mL sodium bicarbonate, supplemented with 2.0 mM L-glutamine and 50 μg/mL gentamicin.

- Type and identity of media, used for cloning efficiency plating:
R20p prepared by mixing equal volumes of R10p and R30p,
whereby R30p is medium R0 supplemented with 0.02% v/v Synperonic F68, 1.0 mM sodium pyruvate and HiDHS at 30% v/v.

HiDHS = heat-inactivated donor horse serum

- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically "cleansed" against high spontaneous background: yes
Metabolic activation:
with and without
Metabolic activation system:
liver S9 mix from male Sprague Dawley derived rats treated with phenobarbital and 5,6-benzoflavone for enzyme induction.
Test concentrations with justification for top dose:
PRELIMINARY TOXICITY TESTING (suspension growth relative to that of vehicle controls)
Test concentrations at 3 h exposure with (+S9) and without (–S9) metabolic activation and at 24 h exposure without metabolic activation (–S9):
2.44, 4.88, 9.77, 19.53, 39.06, 78.13, 156.25, 312.5, 625 and 1250 µg/mL

MUTATION TESTS
Experiment 1, 3 h exposure (–S9):
Exposure concentrations: 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650 μg/mL
Mutant phenotype determination at: 150, 200, 250, 300 μg/mL

Experiment 1, 3 h exposure (+S9):
Exposure concentrations: 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650 μg/mL
Mutant phenotype determination at: 150, 200, 300, 350, 400 μg/mL

Experiment 2, 24 h exposure (–S9):
Exposure concentrations: 25, 50, 100, 150, 200, 250, 300 μg/mL
Mutant phenotype determination at: 100, 150, 200, 250, 300 μg/mL

CRITERIA FOR SELECTING APPROPRIATE TEST CONCENTRATIONS FOR MUTANT PHENOTYPE DETERMINATION:
The highest concentration tested was one that allowed the maximum exposure up to 5000 µg/mL or 10 mM for freely soluble compounds, or the limit of toxicity (i.e. relative total growth reduced to approximately 10 to 20% of the concurrent vehicle control) or the limit of solubility. For a toxic substance, at least 4 analysable concentrations should have been achieved which ideally spanned the toxicity range of 100 to 10% relative total growth (RTG).
Vehicle / solvent:
Dimethyl sulphoxide (DMSO)

Justification for choice of solvent/vehicle:
DMSO was chosen as a vehicle to maximise exposure of cultures in the test system to WS400123. WS400123 was shown to be soluble in DMSO at 250 mg/mL. This concentration produced a test substance concentration in culture medium of 5000 µg/mL when administering this DMSO test substance solution to the culture medium at 2% v/v. At 2500 and 5000 µg/mL fluctuation in osmolality was > 50 mOsm/kg compared with the vehicle control. At 1250 µg/mL fluctuation in osmolality and in pH were within accepptable limits leading to the choice of 1250 µg/mL as the maximum concentration tested in the preliminary toxicity test.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
DMSO (2% v/v final concentration in the medium)
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
Remarks:
DMSO (2% v/v final concentration in the medium)
True negative controls:
no
Positive controls:
yes
Positive control substance:
benzo(a)pyrene
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: Experiment 1: 3 h exposure with (+S9) and without (–S9) metabolic activation
Experiment 2: 24 h exposure without metabolic activation (–S9)

- Selection time: At 48 h after the end of exposure addition of the selection agent trifluorothymidine (TFT)
then allowing 10-14 days for cells to grow with TFT.

SELECTION AGENT: Trifluorothymidine (TFT)

NUMBER OF REPLICATIONS: 2 cultures at each concentration,
[from each culture two vials for assessment of growth in suspension, two 96-well plates for assessment of cloning efficiency
and two 96-well plates for assessment of mutant potential; vehicle controls in quadruplicate].

NUMBER OF CELLS EVALUATED: 2000 cells/well x 192 wells = 384000 cells per culture

DETERMINATION OF CYTOTOXICITY: Relative total growth; (in preliminary toxicity test Relative suspension growth)
Evaluation criteria:
The mutation test result was regarded as negative if:
The mean mutant frequency of all test concentrations was less than the sum of the mean concurrent vehicle control mutant frequency and the Global Evaluation Factor (GEF = 126 x 10^–6, Moore et al. 2006, detailed reference see below).

If the mutant frequency of any test concentrations exceeded the sum of the mean concurrent solvent control mutant frequency and the GEF, a linear trend test was applied: If the linear trend test was negative, the result was regarded as negative. If the linear trend test was positive, this indicated a positive, biologically relevant response.

Reference for GEF:
Moore, M.M., Honma, M., Clements, J., Bolcsfoldi, G., Burlinson, B. Cifone, M., Clarke, J., Delongchamp, R., Durward, R., Fellows, M., Gollapudi, B., Hou, S., Jenkinson, P., Lloyd, M., Majeska, J., Myhr, B., O’Donovan, M, Omori, T, Riach, C., San, R., Stankowski. JR. L.F., Thakur, A.K., Van Goethem, F., Wakuri, S. and Yoshimura, I. (2006). Mouse lymphoma thymidine kinase gene mutation assay: Follow-up meeting of the international workshop on Genotoxicity testing – Aberdeen, Scotland, 2003 – Assay acceptance criteria, positive controls, and data evaluation. Environmental and Molecular Mutagenesis. 47, 1-5.
Statistics:
The data were analysed using Fluctuation application SAFEStat (SAS statistical applications for end users) version 1.1, which follows the methods described by Robinson et al. 1989 using a one-sided F-test, where p<0.001.
Robinson, W.D., Green, M.H.L., Cole, J., Healy, M.J.R., Garner, R.C., and Gatehouse, D. (1989). Statistical evaluation of bacterial/mammalian fluctuation tests. In: Kirkland, D. J. (Ed). UKEMS Sub-committee on Guidelines for Mutagenicity Testing. Report. Part 111. Statistical Evaluation of Mutagenicity Test Data, p.102-140. Cambridge University Press, Cambridge.
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
not determined
Remarks:
Preliminary Toxicity Testing: 3 h exposure (–/+S9) and 24 h exposure (–S9)
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Detailed in Table 1
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
not applicable
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Remarks:
Experiment 1, 3 h exposure (–/+S9)
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Detailed in Table 2
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
without
Genotoxicity:
negative
Remarks:
Experiment 2, 24 h exposure (–S9)
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
Detailed in Table 2
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
At 2500 and 5000 µg/mL fluctuation in osmolality was unacceptably high (i.e. > 50 mOsm/kg compared with the vehicle control) leading to the choice of 1250 µg/mL as the maximum concentration tested in the preliminary toxicity test. The concentrations chosen for mutagenicity testing In both main mutation experiments (Experiments 1 and 2) were considerably lower than 1250 µg/mL because of cytotoxicity (detailed in Table 2).

JUSTIFICATION FOR NOT CONFIRMING THE NEGATIVE RESULT ATTAINED WITH METABOLIC ACTIVATION (+S9)
In the presence of S9, there were no increases in mean mutant frequencies of any of the test concentrations assessed that exceeded the sum of the mean concurrent vehicle control mutant frequency and the Global Evaluation Factor (GEF), within acceptable levels of toxicity. All mean mutant frequencies of the test concentrations were within the acceptable solvent control values (i.e. within 50 to 170 x10^-6, Moore et al. 2006) and there were no increases in mean mutant frequencies of any test concentration assessed that were associated with a linear trend (P>0.05). Therefore, it was considered unnecessary to perform a direct repeat of the assay in the presence of S9. In the absence of S9, the negative mutagenicity results attained after 24 h of exposure (Experiment 2) confirmed those attained after 3 hours of exposure (Experiment 1).

 

Table 1:

Cytotoxicity Expressed as Relative Suspension Growth (RSG) in the Preliminary Toxicity Test

3 h exposure (–S9)

3 h exposure (+S9)

24 h exposure (–S9)

Treatment / Concentration
(µg/mL)

RSG

(%)

Treatment / Concentration
(µg/mL)

RSG

(%)

Treatment / Concentration
(µg/mL)

RSG

(%)

Vehicle Control (DMSO)

100

Vehicle Control (DMSO)

100

Vehicle Control (DMSO)

100

WS400123
(2.44)

 96

WS400123
(2.44)

 88

WS400123
(2.44)

 92

WS400123
(4.88)

 99

WS400123
(4.88)

113

WS400123
(4.88)

 86

WS400123
(9.77)

 65

WS400123
(9.77)

114

WS400123
(9.77)

 89

WS400123
(19.53)

 84

WS400123
(19.53)

119

WS400123
(19.53)

 87

WS400123
(39.06)

 97

WS400123
(39.06)

 96

WS400123
(39.06)

 96

WS400123
(78.13)

 87

WS400123
(78.13)

115

WS400123
(78.13)

 77

WS400123
(156.25)

 99

WS400123
(156.25)

118

WS400123
(156.25)

 50

WS400123
(312.5)

 40

WS400123
(312.5)

 74

WS400123
(312.5)

  4

WS400123
(625)

  1

WS400123
(625)

  1

WS400123
(625)

  0

WS400123
(1250)

  0

WS400123
(1250)

  0

WS400123
(1250)

  0

 

In the Preliminary Toxicity Test, precipitation was not seen at any exposure concentration at the end of treatment.

  

Table 2:

Cytotoxicity Expressed as Mean Relative Total Growth (RTG) in Both Main Mutation Experiments

Experiment 1,
3 h exposure (–S9)

Experiment 1,
3 h exposure (+S9)

Experiment 2,
24 h exposure (–S9)

Treatment / Concentration
(µg/mL)

RTG

(%)

Treatment / Concentration
(µg/mL)

RTG

(%)

Treatment / Concentration
(µg/mL)

RTG

(%)

Vehicle Control (DMSO)

100

Vehicle Control (DMSO)

100

Vehicle Control (DMSO)

100

 

 

 

 

WS400123
(100)

123

WS400123
(150)

114

WS400123
(150)

 86

WS400123
(150)

102

WS400123
(200)

103

WS400123
(200)

 88

WS400123
(200)

 65

WS400123
(250)

 85

 

 

WS400123
(250)

 39

WS400123
(300)

 22

WS400123
(300)

 67

WS400123
(300)

 13

 

 

WS400123
(350)

 33

 

 

 

 

WS400123
(400)

 12

 

 

  

In Main Experiments 1 and 2, precipitation was not seen at the end of treatment at any exposure concentration selected for metaphase analysis.

Conclusions:
Interpretation of results : negative without and with metabolic activation (-/+S9)
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Justification for classification or non-classification

Based on the negative results attained in all in vitro genotoxicity studies WS400123 is considered not to be genotoxic and does not warrant any classification regarding mutagenicity according to European classification rules [REGULATION (EC) 1272/2008].