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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in chemico
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2018-04-13 to 2019-05-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

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

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
GLP compliance:
yes (incl. QA statement)
Type of study:
direct peptide reactivity assay (DPRA)

Test material

Constituent 1
Chemical structure
Reference substance name:
sodium 2-chloroprop-2-enoate
EC Number:
608-818-5
Cas Number:
32997-86-7
Molecular formula:
C3H2ClO2.Na
IUPAC Name:
sodium 2-chloroprop-2-enoate
Test material form:
liquid

In chemico test system

Details on the study design:
The reactivity of a test chemical and synthetic cysteine or lysine containing peptides was evaluated by combining the test chemical with a solution of the peptide (reaction samples) and monitoring the remaining concentration of the peptide following 24 ± 2 hours of interaction time at room temperature (25 ± 2.5 °C). The peptide is a custom material containing phenylalanine to aid in detection and either cysteine or lysine as the reactive centre. Relative concentrations of the peptide following the 24 hour reaction time were determined by HPLC with gradient elution and UV detection at 220 nm. Samples were prepared and analysed in triplicates in batches to keep the total HPLC analysis time less than 30 hours.

Results and discussion

Positive control results:
Peptide depletion resulted from the positive control cinnamaldehyde was 70.60 % with cysteine peptide and 53.00 % with the lysine peptide while the standard deviation (SD) of the percent peptide depletions were 1.0 % and 0.5 % for the cysteine and lysine peptides, respectively, in the valid runs. The back-calculated values of all reference control replicates were within the expected molarity concentration range for the cysteine (0.50 – 0.49 mM) and lysine peptides (0.50 – 0.49 mM) and the CV % for the nine reference controls B and C in acetonitrile were 2.6 % and 0.3 % percentages for the cysteine and lysine peptides. Thus in these runs for each peptide all validity criteria were met, confirming the validity of the assay.

In vitro / in chemico

Resultsopen allclose all
Key result
Run / experiment:
other: 1
Parameter:
other: % peptide depletion cysteine
Value:
15.29
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid
Key result
Run / experiment:
other: 1
Parameter:
other: % peptide depletion lysine
Value:
6.62
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid
Key result
Run / experiment:
other: 1
Parameter:
other: % mean peptide depletion
Value:
10.96
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid
Other effects / acceptance of results:
OTHER EFFECTS:
- Visible damage on test system:

DEMONSTRATION OF TECHNICAL PROFICIENCY:
Prior to routine use of the method, the laboratory demonstrated technical proficiency in a separate study (Study number.: 392-442-2996) by correctly obtaining the expected DPRA prediction for 10 proficiency substances as recommended in the OECD TG 442C guideline.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative (vehicle) control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes

Applicant's summary and conclusion

Interpretation of results:
other: positive
Conclusions:
Based on these results and the cysteine 1:10 / lysine 1:50 prediction model, the test item was concluded to be positive and have low reactivity towards the synthetic peptides thus is a potential skin sensitizer under the experimental conditions of the in chemico Direct Peptide Reactivity Assay (DPRA) method.
Executive summary:

In the course of this study the skin sensitization potential of the test item was studied using the Direct Peptide Reactivity Assay (DPRA). For the test chemical and positive control substance, in order to derive a prediction five independent tests were conducted, since the first run with cysteine peptide and the first two runs with lysine peptide did not meet the acceptance criteria and those results were rejected. All in all, the results of the two valid runs were used for the classification of the test item.

Peptide depletion resulted from the positive control cinnamaldehyde was 70.60 % with cysteine peptide and 53.00 % with the lysine peptide while the standard deviation (SD) of the percent peptide depletions were 1.0 % and 0.5 % for the cysteine and lysine peptides, respectively, in the valid runs. The back-calculated values of all reference control replicates were within the expected molarity concentration range for the cysteine (0.50 – 0.49 mM) and lysine peptides (0.50 – 0.49 mM) and the CV % for the nine reference controls B and C in acetonitrile were 2.6 % and 0.3 % percentages for the cysteine and lysine peptides. Thus in these runs for each peptide all validity criteria were met, confirming the validity of the assay. The percent cysteine peptide depletion value of the test item was 15.29 % while the percent lysine peptide depletion was 6.62 %. The mean depletion value of the peptides being 10.96 % was used to categorize the test chemical in one of the four classes of reactivity. No co-elution was observed with either cysteine or lysine peptides; therefore the cysteine 1:10 / lysine 1:50 prediction model was used for the discrimination between sensitizers and non-sensitizers. The mean peptide depletion of the test item was 10.96 %, exceeding the 6.38 % threshold of the applicable prediction model for being positive. Thus, the test item was found to be positive for skin sensitising potential under the conditions of this study.

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