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Table 1: Summarized results of the concentration selection cytotoxicity assays A and B
without S9-mix Relative survival (%)
with S9-mixRelative survival (%)
2% v/v DMSO
*Time of Treatment/Sampling: 3h/20h with and without activation
**Time of Treatment/Sampling: 20h/28h without activation, 3h/28h with activation
Table 2: Summary table of Chromosome Aberration Assay 1
Time of Treatment / Sampling
Mean aberrant cells###
WS400104 without metabolic activation (-S9)
WS400104 with metabolic activation (+S9)
Vehicle (solvent) control: 1% (v/v) DMSO without (Assay –S9), 2% (v/v) DMSO (Assay +S9)
Positive control (-S9): Ethyl methanesulfonate, 1μL/mL; Positive control (+S9): Cyclophosphamide, 6μg/mL
NE: not evaluated
#: compared to the vehicle (solvent control)
##: in the final treatment medium at the end of the treatment
###: excluding gaps
**: p<0.01 comparing numbers of aberrant cells excluding gaps with corresponding negative control
***: p<0.001 comparing numbers of aberrant cells excluding gaps with corresponding negative control
Table 3: Summary table of Chromosome Aberration Assay 2
20h / 28h
Vehicle (solvent) control: 1% (v/v) DMSO
Positive control (-S9): Ethyl methanesulfonate, 0.4μL/mL; positive control (+S9): Cyclophosphamide, 6 μg/mL
#: compared to the negative (solvent control)
In Assays 1 and 2, none of the treatment doses caused a significant increase in the number of cells with structural chromosome aberrations in either assay with or without metabolic activation except for 625 μg/mL concentration in Assay 1 with metabolic activation, in one replicate. This was not repeatable in Assay 2 (although elevated aberration frequency was observed at the same concentration), nor did the higher concentration assessed in Assay 1 with metabolic activation give a positive response. There was no evidence of any dose response in either assay.
Because of the equivocal results observed in Assay 1 with metabolic activation, an additional experiment with metabolic activation (Assay 3) was performed - with a more closely spaced concentration range, but otherwise using the same treatment and harvesting time as in Assay 1.
Table 4: Summary table of Chromosome Aberration Assay 3 with metabolic activation
Mean % aberrant cells###
Positive control (+S9): Cyclophosphamide, 6μg/mL
It was concluded that the single result at 625 μg/mL with metabolic activation seen in a single replicate (not in the other replicate) was not reproducible in a repeat assay and did not show a dose response relationship. Hence this single result was not considered to represent an adverse effect of the test item.
The occurrence of polyploid and endoreduplicated metaphases was recorded in the main tests. Polyploid (1-11) and endoreduplicated (1-4) metaphases were found in some cases in the vehicle (solvent) control, positive control or test item treated samples in the performed experiments.
Precipitate / slight precipitate was observed in Experiment 2 in all tested bacterial strains (S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2) at 5000 µg/plate concentration with and without metabolic activation.
Based on the negative results attained in all in vitro genotoxicity studies, WS400104 is considered not to be genotoxic and does not warrant any classification regarding mutagenicity according to European classification rules [REGULATION (EC) 1272/2008].
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