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

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

For this endpoint a one-to-one read across was performed to a chemical similar compound (CAS 1818916-02-7) of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD Guideline 429.
Skin sensitisation was studied with the structural analogue substance using GLP in vitro studies performed according to OECD TG 442C-E, however, with conflicting results (for more details please refer to the ECHA dossier of the structural analogue substance CAS 1818916-02-7). The conflicting in vitro data are insufficient to conclude on the endpoint of skin sensitisation. Therefore, an additional in vivo study was performed.

Cross-reference

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Dec 18, 2019 - Apr 02, 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Skin sensitisation was studied using GLP in vitro studies performed according to OECD TG 442C-E, however with conflicting results . The conflicting in vitro data are insufficient to conclude on the endpoint of skin sensitisation. Therefore, an additional in vivo study was performed.

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA:J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Inbred, SPF-Quality
- Age at study initiation: 10 weeks
- Weight at study initiation: Pre-test and Main test: 19.9 to 25.9 g
- Housing: grouped per dose
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 °C
- Humidity (%): 42 - 50 %
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: day 1 To: day 6

Vehicle:

methyl ethyl ketone

Concentration:

5, 10, and 35% (w/w)

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
Two test item concentrations were tested; a 25% and 35% concentration.

- Compound solubility: 35 % in MEK
- Irritation:yes (At a 35% test item concentration No signs of systemic toxicity were noted and only very slight irritation of the ears was observed in animals treated with 35% test item concentration.)
- Lymph node proliferation response: -


MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: OECD 429
- Criteria used to consider a positive response: Stimulation index > 3

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Standard statistical methods have been applied for data processing.

Positive control results:

Conc. SI
0%: 1.0
5% 1.3
10% 1.4
25% 5.2

Key result

Parameter:

SI

Value:

1.5

Test group / Remarks:

Test Group: 5% in MEK

Key result

Parameter:

SI

Value:

1.3

Test group / Remarks:

Test Group: 10% in MEK

Key result

Parameter:

SI

Value:

0.4

Test group / Remarks:

Test Group: 35% in MEK

Calculation of Stimulation Indices per Dose Group

Test item concentration	Group Calculation
	Mean DPM per animal (2 lymph nodes)	SD	S.I.
MEK (Vehicle Control)	744	145	1.0
5 % Test Item in MEK	1084	158	1.5
10 % Test Item in MEK	974	219	1.3
35 % Test Item in MEK	321	103	0.4

Interpretation of results:

GHS criteria not met

Conclusions:

The test item would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines. The test item does not have to be classified and has no obligatory labelling requirement for sensitization by skin contact according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2017) (including all amendments) and the Regulation (EC) No 1272/2008 on classification, labelling and packaging of items and mixtures (including all amendments).

Executive summary:

Objective

The objective of this study was to evaluate whether the test material induces skin sensitization in mice after three epidermal exposures of the animals under the conditions described in this report.

Study Design

The study was carried out based on the guidelines described in:

• OECD, Section 4, Health Effects, No.429 (2010).

• EC No 640/2012, Part B: "Skin Sensitization: Local Lymph Node Assay".

• EPA, OPPTS 870.2600 (2003) “Skin Sensitization”.

Test item concentrations selected for the main study were based on the results of a pre-screen test. Based on the results, the highest concentration required according to the guidelines was selected.

In the main study, three experimental groups of five female CBA/J mice were treated with test item concentrations of 5, 10 or 35% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with the vehicle alone (Methylethylketone). Three days after the last exposure, all animals were injected with 3Hmethyl thymidine and after five hours the draining (auricular) lymph nodes were excised and pooled for each animal. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of disintegrations per minute (DPM) and a stimulation index (SI) was subsequently calculated for each group.

Results

All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. Mean DPM/animal values for the experimental groups treated with test item concentrations 5, 10 and 35% were 1084, 974 and 321 DPM, respectively. The mean DPM/animal value for the vehicle control group was 744 DPM. The SI values calculated for the test item concentrations 5, 10 and 35% were 1.5, 1.3 and 0.4, respectively. Since there was no indication that the test item elicits a SI = 3 when tested up to 35%, the test material was considered not to be a skin sensitizer. It was established that the EC3 value (the estimated test item concentration that will give a SI =3) (if any) exceeds 35%.

Conclusion

Based on these results, the test material would not be regarded as a skin sensitizer according to the recommendations made in the test guidelines. The test item does not have to be classified and has no obligatory labelling requirement for sensitization by skin contact according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2017) (including all amendments) and the Regulation (EC) No 1272/2008 on classification, labelling and packaging of items and mixtures (including all amendments).

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

5-ethoxy-6,10-difluoro-11-(hexyloxy)-8-thiatricyclo[7.4.0.0²,⁷]trideca-1(9),2(7),3,5,10,12-hexaene

EC Number:

950-069-4

Molecular formula:

C20H22F2O2S

IUPAC Name:

5-ethoxy-6,10-difluoro-11-(hexyloxy)-8-thiatricyclo[7.4.0.0²,⁷]trideca-1(9),2(7),3,5,10,12-hexaene

Test material form:

solid

Results and discussion

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

1.5

Test group / Remarks:

Test Group: 5% in MEK

Results 2

Key result

Parameter:

SI

Value:

1.3

Test group / Remarks:

Test Group: 10% in MEK

Results 3

Key result

Parameter:

SI

Value:

0.4

Test group / Remarks:

Test Group: 35% in MEK

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 429. In this study of the read across source compound, no potential for skin sensitisation was found. The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Based on available data, the test item does not require classification for skin sensitisation according to Regulation (EC) No 1272/2008 (CLP), as amended for the twelfth time in Regulation (EU) 2019/521.