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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in chemico
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental study based upon guideline 442c

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019
Report Date:
2019

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
Version / remarks:
february 4th, 2015
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of study:
direct peptide binding assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Benzylidenchlorid
No more data available

In chemico test system

Details on study design:
19.57 mg cysteine peptide with an amino acid sequence of Ac-RFAACAA were pre-weighed in a vial and dissolved in a defined volume (37.23 mL) of a phosphate buffer with pH 7.5 to reach a concentration of 0.667 mM.
19.04 mg lysine peptide with an amino acid sequence of Ac-RFAAKAA were pre-weighed in a vial and dissolved in a defined volume of ammonium acetate buffer with pH 10.2 (35.26 mL) to reach a concentration of 0.667 mM.
All peptides used for this study were stored at -80 °C and protected from light. Peptides were thawed only immediately prior to use.

Results and discussion

In vitro / in chemico

Results
Key result
Parameter:
other: Mean % depletion of peptides
Run / experiment:
Peptides run
Value:
ca. 64.95
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Other effects / acceptance of results:
The data generated with this test should be considered in the context of integrated approached such as IATA, combining the result with other complementary information, e.g. derived from in vitro assays addressing other key events of the skin sensitisation AOP.

Any other information on results incl. tables

The in chemico direct peptide reactivity assay (DPRA) enables detection of the sensitising potential of a test item by addressing the molecular initiating event of the adverse outcome pathway (AOP), namely protein reactivity, by quantifying the reactivity of test chemicals towards synthetic peptides containing either lysine or cysteine. The percentage depletion value of the cysteine and lysine peptide is used to categorize a substance in one of four reactivity classes to support discrimination between skin sensitisers and non-sensitisers.

In the present study Benzal chloride was dissolved in acetonitrile, based on the results of the pre-experiments. Based on a molecular weight of 161.03 g/mol a 100 mM stock solution was prepared. The test item solutions were tested by incubating the samples with the peptides containing either cysteine or lysine for 24 ± 2 h at 25 ± 2.5 °C. Subsequently samples were analysed by HPLC.

All test item solutions were freshly prepared immediately prior to use.

For the 100 mM stock solution of the test item precipitation was observed when diluted with the cysteine peptide solution. After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples were inspected for precipitation, turbidity or phase separation. No precipitation, turbidity or phase separation was observed for any of the samples.

For the 100 mM stock solution of the test item phase separation was observed when diluted with the lysine peptide solution. After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples were inspected for precipitation, turbidity or phase separation. Slight phase separation was observed for the samples of the test item and phase separation was observed for the samples of the positive control (including the co-elution controls). Samples were not centrifuged prior to the HPLC analysis.

Since the acceptance criteria for the depletion range of the positive control were fulfilled, the observed phase separation was regarded as not relevant.

Co-elution of the test item with the cysteine peptide peak and a slight phase separation with the lysine peptide peak was observed. Therefore, evaluation of the peptide depletion was not possible and the result must be considered as inconclusive.

The 100 mM stock solution of the positive control (cinnamic aldehyde) showed high reactivity towards the synthetic peptides. The mean depletion of both peptides was 64.95%.

The controls confirmed the validity of the study for both, the cysteine and lysine run

Applicant's summary and conclusion

Interpretation of results:
study cannot be used for classification
Conclusions:
In this study under the given conditions the test item could not be classified due to co-elution of the test item with the cysteine peptide peak. The result of the study must be considered as inconclusive.
The data generated with this test should be considered in the context of integrated approached such as IATA, combining the result with other complementary information, e.g. derived from in vitro assays addressing other key events of the skin sensitisation AOP.
Executive summary:

The in chemico direct peptide reactivity assay (DPRA) enables detection of the sensitising potential of a test item by quantifying the reactivity of test chemicals towards synthetic peptides containing either lysine or cysteine.

In the present study Benzal chloride was dissolved in acetonitrile, based on the results of the pre-experiments. Based on a molecular weight of 161.03 g/mol a 100 mM stock solution was prepared. The test item solutions were tested by incubating the samples with the peptides containing either cysteine or lysine for 24 ± 2 h at 25 ± 2.5 °C. Subsequently samples were analysed by HPLC.

All test item solutions were freshly prepared immediately prior to use.

For the 100 mM stock solution of the test item precipitation was observed when diluted with the cysteine peptide solution. After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples were inspected for precipitation, turbidity or phase separation. No precipitation, turbidity or phase separation was observed for any of the samples.

For the 100 mM stock solution of the test item phase separation was observed when diluted with the lysine peptide solution. After the 24 h ± 2 h incubation period but prior to the HPLC analysis samples were inspected for precipitation, turbidity or phase separation. Slight phase separation was observed for the samples of the test item and phase separation was observed for the samples of the positive control (including the co-elution controls). Samples were not centrifuged prior to the HPLC analysis.

Since the acceptance criteria for the depletion range of the positive control were fulfilled, the observed phase separation was regarded as not relevant.

Co-elution of the test item with the cysteine peptide peak and a slight phase separation with the lysine peptide peak was observed. Therefore, evaluation of the peptide depletion was not possible and the result must be considered as inconclusive.

The 100 mM stock solution of the positive control (cinnamic aldehyde) showed high reactivity towards the synthetic peptides. The mean depletion of both peptides was 64.95%.