Ethanol, 2-(ethenylthio)-

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2016-02-01 to 2016-07-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))

Version / remarks:

2015

Deviations:

no

Principles of method if other than guideline:

For data evaluation a borderline range was included as an amendment to the evaluation given in the OECD guideline.

GLP compliance:

yes (incl. QA statement)

Type of study:

direct peptide reactivity assay (DPRA)

Test material

Test material information

Constituent 1

Reference substance name:

Ethanol, 2-(ethenylthio)-

EC Number:

608-554-0

Cas Number:

3090-56-0

Molecular formula:

C4H8OS

IUPAC Name:

Ethanol, 2-(ethenylthio)-

Test material form:

liquid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Lot/batch No.of test material: 230-2015

In chemico test system

Details on the study design:

Skin sensitisation (In chemico test system)
Synthetic peptides used:
- Cysteine- (C-) containing peptide: Ac-RFAACAA-COOH (MW=751.9 g/mol)
- Lysine- (K-) containing peptide: Ac-RFAAKAA-COOH (MW=776.2 g/mol)
The peptides are custom material (Supplier: GenScript, Piscataway, NJ, USA and RS Synthesis, Louisville KY, USA) containing phenylalanine to aid in detection and either cysteine or lysine as the reactive center.

Controls used:
- Negative (vehicle) control: acetonitrile
- Positive control: Ethylene glycol dimethacrylate (EGDMA) 50 mM in acetonitrile
- Co-elution control: Sample prepared of the respective peptide buffer and the test
substance but without peptide.

Test substance preparation:
The test substance was prepared as a 100 mM preparation in acetonitrile. After short stirring the test substance was soluble in the vehicle.

Peptide stock solution preparation:
Peptide stock solutions in a concentration of 0.667 mM were prepared in pH 7.5 phosphate buffer (C-containing peptide) or pH 10.2 ammonium acetate buffer (K-containing peptide).

Experimental procedure:
Three samples of the test substance in acetonitrile were incubated with each peptide for 24h at room temperature. The incubation tubes were sealed. Additionally triplicates of the concurrent vehicle control (= NC) were incubated with the peptides. The remaining non-depleted peptide concentration was determined thereafter by HPLC with gradient elution and UV-detection at 220 nm. In addition calibration samples of known peptide concentration, prepared from the respective peptide stock solution used for test-substance incubation, were measured in parallel with the same analytical method.

Sample preparation:
The C-containing peptide was incubated with the test substance in a ratio of 1:10 (0.5 mM peptide, 5 mM test substance) and the K-containing peptide in a ratio of 1:50 (0.5 mM peptide, 25 mM test substance).

Vehicle control preparation:
Several vehicle controls were prepared in triplicates in the same way as the test-substance samples but with vehicle instead of the test substance: One set (set A) was analyzed together with the calibration samples without incubation and serves as a performance control. Another three sets (two sets B and set C) were prepared and incubated with the samples. Sets B were placed at the very start and ending of the sample list and serve as stability control of the peptide over the analysis time. Set C was analyzed with the samples and serves for calculation of the peptide depletion of any chemical formulated in vehicle.

Co-elution control preparation:
The co-elution control was prepared in the same way as the test substance samples but without the peptide. Instead the respective peptide buffer was used.

HPLC conditions:
- Prior to HPLC analysis the samples were visually investigated for any precipitate that may have formed during the exposure period. If the samples were visually turbid or displayed precipitates they were centrifuged or filtered prior to injection into the HPLC in order to remove any unsolved particles. The HLPC analysis of the batch of samples started about 24 hours after sample preparation and the analysis time itself did not exceed 30 hours.
- Device: Liquid chromatograph Thermo Scientific, Dionex Ultimate 3000
- Column: ZORBAX SB-C18 2.1 x 100 mm, 3.5 μm with guard column SecurityGuard Ultra Cartridges, UHPLC C18 for 4.6 mm ID (Phenomenex)
- Mobile phase A: de-ionized water/ acetonitrile/ triflouracetic acid 950/50/1 V/V/V
- Mobile phase B: acetonitrile/ de-ionized water/ triflouracetic acid 950/50/0.85 V/V/V
- Flow rate: 0.5 mL/min
- Wavelength: 220 and 258 nm
- Injection volume: 2 µL

Calculation and data evaluation:
The mean peptide depletion for each of the two peptides is calculated as the mean value of the three samples conducted for each peptide and test substance (C-containing and K- containing peptide depletion).
When samples were additionally analyzed by measuring UV absorbance at 258 nm, the area ratio 220 nm / 258 nm was calculated and served as a measure of peak purity. The ratio of a pure peptide peak should be consistent over all samples (100% ± 10% of the mean of the vehicle controls). However, due to small peak areas calculation of the area ratio may not be possible for all samples.

Acceptance criteria:
- The standard calibration curve should have an r² >0.99.
- The negative control (vehicle control) samples of sets A and C should be 0.50 mM +/- 0.05 mM.
- The CV of the nine vehicle controls B and C should be < 15%.
- Since the mean peptide depletion for each peptide is determined from the mean of three single samples, the variability between these samples should be acceptably low (SD <14.9% for % cysteine depletion and <11.6% for % lysine depletion).
- In addition the positive control should cause depletion of both peptides comparable to historic data.

Evaluation of results:
Chemical reactivity was determined by mean peptide depletion [%] and was rated as high, moderate, low, or minimal.
A mean peptide depletion of > 42.47 % is regarded as high reactivity and positive for peptide depletion (indication for sensitization potential). A moderately reactive test substance (22.62 % < mean peptide depletion ≤ 42.47 %) and a test substance of low reactivity (8.11% < mean peptide depletion ≤ 22.62 %) are regarded as positive for peptide depletion (indication for sensitization potential). A mean peptide depletion of > 4.65 % ≤ 8.11 % is considered no to low reactivity and borderline for sensitization, while ≤ 4.65 % is a minimal to no reactivity and negative for peptide depletion (no indication for sensitization potential).

Results and discussion

Positive control results:

The positive control caused depletion of both peptides comparable to historic data.

In vitro / in chemico

Results

Results 1

Key result

Run / experiment:

mean

Parameter:

other: combined peptide depletion [%]

Value:

0.37

Vehicle controls validity:

valid

Remarks:

0.00 %

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks:

29.84 %

Remarks on result:

no indication of skin sensitisation

Results 2

Run / experiment:

mean

Parameter:

other: cysteine peptide depletion [%]

Value:

0.74

Vehicle controls validity:

valid

Remarks:

0.00 %

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks:

47.61 %

Remarks on result:

no indication of skin sensitisation

Results 3

Run / experiment:

mean

Parameter:

other: lysine peptide depletion [%]

Value:

-0.03

Vehicle controls validity:

valid

Remarks:

0.00 %

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks:

12.06 %

Remarks on result:

no indication of skin sensitisation

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: The test substance was dissolved in acetonitrile. The samples of the test substance with the peptides were solutions. Visual observation after the 24-hour incubation time did not reveal precipitates in any samples of the test substance with the peptides. No co-elution of the test substance and peptides occurred.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative 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:

GHS criteria not met