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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:
weight of evidence
Study period:
2018-06-25 to 2018-06-28
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 guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
Qualifier:
according to guideline
Guideline:
other: Direct Peptide Reactivity Assay (DPRA) for Skin Sensitization Testing, DB-ALM Protocol n°154, January 12, 2013
GLP compliance:
yes (incl. QA statement)
Remarks:
Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany
Type of study:
direct peptide reactivity assay (DPRA)

Test material

Constituent 1
Chemical structure
Reference substance name:
-
EC Number:
425-880-7
EC Name:
-
Cas Number:
182311-45-1
Molecular formula:
C31H40O5
IUPAC Name:
4-(6-acryloyloxyhexyloxy)benzoic acid (4-(trans-4-propylcyclohexyl)phenyl ester)
Test material form:
solid: bulk

In chemico test system

Details on the study design:
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.

Results and discussion

Positive control results:
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 65.38%.

In vitro / in chemico

Resultsopen allclose all
Key result
Run / experiment:
other: cysteine run
Parameter:
other: mean peptide depletion [%]
Value:
0.52
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Run / experiment:
other: lysine run
Parameter:
other: mean peptide depletion [%]
Value:
0
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Other effects / acceptance of results:
Acceptance Criteria

The run meets the acceptance criteria if:
- the standard calibration curve has a r² > 0.99,
- the mean percent peptide depletion (PPD) value of the three replicates for the positive control is between 60.8% and 100% for the cysteine peptide and the maximum standard deviation (SD) for the positive control replicates is < 14.9%,
- the mean percent peptide depletion (PPD) value of the three replicates for the positive control is between 40.2% and 69.0% for the lysine peptide and the maximum SD for the positive control replicates is < 11.6%,
- the mean peptide concentration of the three reference controls A replicates is 0.50 ± 0.05 mM,
- the coefficient of variation (CV) of peptide peak areas for the six reference control B replicates and three reference control C replicates in acetonitrile is < 15.0%.

The results of the test item meet the acceptance criteria if:
- the maximum standard deviation (SD) for the test chemical replicates is < 14.9% for the cysteine percent depletion (PPD),
- the maximum standard deviation (SD) for the test chemical replicates is < 11.6% for the lysine percent depletion (PPD),
- the mean peptide concentration of the three reference controls C replicates in the appropriate solvent is 0.50 ± 0.05 mM.

Both peptide runs and the test item results met the acceptance criteria of the test.

Any other information on results incl. tables

Cysteine and Lysine Values of the Calibration Curve

Sample

Cysteine Peptide

Lysine Peptide

Peak Area
at 220 nm

Peptide Concentration [mM]

Peak Area
at 220 nm

Peptide Concentration [mM]

STD1

15.0360

0.5340

14.1920

0.5340

STD2

7.5920

0.2670

7.1540

0.2670

STD3

3.7630

0.1335

3.5770

0.1335

STD4

1.8500

0.0667

1.7790

0.0667

STD5

0.8890

0.0334

0.8770

0.0334

STD6

0.4300

0.0167

0.4310

0.0167

STD7

0.0000

0.0000

0.0000

0.0000

Depletion of the Cysteine Peptide

Cysteine Peptide

Sample

Peak Area
at 220 nm

Peptide Conc. [mM]

Peptide Depletion [%]

Mean Peptide Depletion [%]

SD of Peptide Depletion [%]

CV of Peptide Depletion [%]

Positive Control

4.1310

0.1469

70.73

71.32

0.53

0.74

4.0270

0.1433

71.47

3.9870

0.1418

71.75

Test Item

14.4290

0.5114

0.00

0.52

0.89

172.02

14.1140

0.5002

0.01

13.8970

0.4925

1.54

 

Depletion of the Lysine Peptide

Lysine Peptide

Sample

Peak Area
at 220 nm

Peptide Conc. [mM]

Peptide Depletion [%]

Mean Peptide Depletion [%]

SD of Peptide Depletion [%]

CV of Peptide Depletion [%]

Positive Control

5.3010

0.1990

60.30

59.44

0.84

1.41

5.4220

0.2036

59.39

5.5240

0.2074

58.63

Test Item

13.4640

0.5057

0.00

0.00

0.00

-

13.3870

0.5028

0.00

13.4230

0.5042

0.00

Prediction Model 1

Cysteine 1:10/ Lysine 1:50 Prediction Model 1

Mean Cysteine andLysine PPD

Reactivity Class

DPRA Prediction²

0.00% PPD 6.38%

 No or Minimal Reactivity

Negative

6.38% < PPD 22.62%

Low Reactivity

Positive

22.62% < PPD 42.47%

Moderate Reactivity

42.47% < PPD 100%

High Reactivity

1 The numbers refer to statistically generated threshold values and are not related to the precision of the measurement.

2 DPRA predictions should be considered in the framework of an IATA.

Prediction Model 2

Cysteine 1:10 Prediction Model

Cysteine PPD

ReactivityClass

DPRA Predictio

0.00% PPD 13.89%

No or Minimal Reactivity

Negative

13.89% < PPD 23.09%

Low Reactivity

Positive

23.09% < PPD 98.24%

Moderate Reactivity

98.24% < PPD 100%

High Reactivity

Categorization of the Test Item

Prediction Model

Prediction Model 1
(Cysteine Peptide and Lysine Peptide / Ratio: 1:10 and 1:50)

Prediction Model 2
(Cysteine Peptide / Test Item Ratio: 1:10)

Test Substance

Mean Peptide Depletion [%]

Reactivity Category

Prediction

Mean Peptide Depletion [%]

Reactivity Category

Prediction

Test Item

0.26

Minimal Reactivity

-

0.52

Minimal Reactivity

-

Positive Control

65.38

High Reactivity

sensitiser

71.32

Moderate Reactivity

sensitiser

Applicant's summary and conclusion

Interpretation of results:
other: The result should be considered in the context of IATA.
Conclusions:
In this study under the given conditions the test item showed minimal reactivity towards both peptides. Due to the observed precipitation the prediction model does not apply and a prediction cannot be made.
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:

In the present study the test material was dissolved in acetonitrile, based on the results of the pre-experiments.

Based on a molecular weight of 492 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.

Forthe 100 mM stock solution of the test item turbidity 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. Precipitation was observed for the samples of the test item (including the co-elution control). Samples were centrifuged prior to the HPLC analysis.

For the 100 mM stock solution of the test item turbidity 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. Phase separation was observed for the samples of the positive control (including the co-elution control). Precipitation was observed for the samples of the test item (including the co-elution control). Test item samples were 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.

The stock solution of the test item showed minimal reactivity towards the synthetic peptides. The mean depletion of both peptides was  6.38% (0.26%).Since precipitation wasobserved, a test item concentration of 100 mM as well as the full contact of peptide and test item is not guaranteed. According to the evaluation criteria in the guideline,no firm conclusion on the lack of reactivity should be drawn from a negative result, if a test chemical is tested in concentration < 100 mM.Therefore, no prediction can be made.

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 65.38%.