3-Butoxy-7-ethoxy-4,6-difluoro-dibenzothiophene

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-01-07 to 2019-02-14

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

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Test guideline 2

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

Test material information

Constituent 1

Reference substance name:

3-Butoxy-7-ethoxy-4,6-difluoro-dibenzothiophene

EC Number:

946-002-3

Cas Number:

1818916-02-7

Molecular formula:

C18H18F2O2S

IUPAC Name:

3-Butoxy-7-ethoxy-4,6-difluoro-dibenzothiophene

Test material form:

solid

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 64.95%.

In vitro / in chemico

Results

Results 1

Key result

Run / experiment:

other: cysteine run

Parameter:

other: mean peptide depletion [%]

Value:

1.13

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Results 2

Key result

Run / experiment:

other: lysine run

Parameter:

other: mean peptide depletion [%]

Value:

0.15

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]	PeakArea at 220 nm	Peptide Concentration [mM]
STD1	17.4940	0.5340	15.0310	0.5340
STD2	8.7090	0.2670	7.5160	0.2670
STD3	4.3730	0.1335	3.7790	0.1335
STD4	2.1750	0.0667	1.8940	0.0667
STD5	1.0820	0.0334	0.9520	0.0334
STD6	0.5670	0.0167	0.4950	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 Concentration [mM]	Peptide Depletion [%]	Mean Peptide Depletion [%]	SD of Peptide Depletion [%]	CV of Peptide Depletion [%]
Positive Control	4.8780	0.1491	70.09	69.94	0.43	0.62
	4.8480	0.1482	70.27
	4.9820	0.1523	69.45
Test Item	16.2480	0.4964	0.53	1.13	0.52	45.89
	16.1020	0.4919	1.42
	16.1010	0.4919	1.43

Depletion of the Lysine Peptide

Lysine Peptide
Sample	Peak Area at 220 nm	Peptide Concentration [mM]	Peptide Depletion [%]	Mean Peptide Depletion [%]	SD of Peptide Depletion [%]	CV of Peptide Depletion [%]
Positive Control	5.5200	0.1958	61.01	59.97	2.04	3.41
	5.4810	0.1944	61.28
	6.0000	0.2128	57.61
Test Item	14.2380	0.5058	0.00	0.15	0.26	173.21
	14.1410	0.5024	0.45
	14.2880	0.5076	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 Prediction²
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 / Item 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	0.64	Minimal Reactivity	(negative)	1.13	Minimal Reactivity	(negative)
Positive Control	64.95	High Reactivity	positive	69.94	Moderate Reactivity	positive

Applicant's summary and conclusion

Interpretation of results:

other: Data should be considered in the context of integrated approached such as 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 DMF, based on the results of the pre-experiments, but DMF did not pass the validity criteria for the Reference Control C and was therefore excluded from the evaluation.

The solubility experiment was carried on and ethanol was found as solvent, too. Based on a molecular weight of 336 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.

For the 100 mM stock solution of the test item no turbidity or 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. Precipitation was observed for the samples of the test item, including the co-elution control. Samples of the test item (including the co-elution control) were centrifuged prior to the HPLC analysis.

For the 100 mM stock solution of the test item turbidity and precipitation 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. Precipitation was observed for the samples of the test item, including the co-elution control. Samples of the test item (including the co-elution control) were centrifuged prior to the HPLC analysis. Phase separation (small droplets) was observed for the samples of the positive control (including the co-elution control). 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.

The stock solution of the test item showed minimal reactivity towards the synthetic peptides. The mean depletion of both peptides was ≤ 6.38% (0.64%). Since a precipitation was observed, 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, therefore, no prediction can be made.