4'-Butyl-4-ethoxy-2,3-difluoro-1,1'-biphenyl

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Sep 30, 2019 - Apr 20, 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The study was conducted for a registration in a non-EU country.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2010

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

EC No 640/2012

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Version / remarks:

2003

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

4'-butyl-4-ethoxy-2,3-difluoro-1,1'-biphenyl

EC Number:

695-755-1

Cas Number:

1229661-51-1

Molecular formula:

C18H2F2O

IUPAC Name:

4'-butyl-4-ethoxy-2,3-difluoro-1,1'-biphenyl

Test material form:

solid: particulate/powder

In vivo test system

Test animals

Species:

mouse

Strain:

CBA:J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Inbred, SPF-Quality, Janvier, Le Genest-Saint-Isle, France
- Age at study initiation: 10 weeks
- Weight at study initiation: Pre-test and Main test: 19.4 to 25.1 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 - 63 %
- Photoperiod (hrs dark / hrs light): 12/12

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

Study design: in vivo (LLNA)

Vehicle:

dimethylformamide

Concentration:

25, 50, and 80% (w/w)

No. of animals per dose:

5

Details on study design:

RANGE FINDING TESTS:
Two test item concentrations were tested; a 50% and 80% concentration. The highest concentration was the highest concentration that could be prepared homogeneously.

At a 50 and 80% test item concentration, no signs of systemic toxicity were noted and no or only very slight irritation was observed. Therefore, an 80% concentration was selected as highest concentration for the main study.

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.

Results and discussion

Positive control results:

Conc. SI
0%: 1.0
5% 1.3
10% 3.4
25% 5.5

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

2.5

Variability:

+/- 0.8

Test group / Remarks:

Test Group: 25% in DMF

Results 2

Key result

Parameter:

SI

Value:

6.7

Variability:

+/- 0.3

Test group / Remarks:

Test Group: 50% in DMF

Results 3

Key result

Parameter:

SI

Value:

3.3

Variability:

+/- 0.1

Test group / Remarks:

Test Group: 80% in DMF

Any other information on results incl. tables

Calculation of Stimulation Indices per Dose Group

Test item concentration	Group Calculation
	Mean DPM per animal (2 lymph nodes)	SD	S.I.
DMF (Vehicle Control)	202	18	1.0
25 % Test Item in DMF	512	156	2.5
50 % Test Item in DMF	1357	64	6.7
80 % Test Item in DMF	674	30	3.3

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

The test item is considered to be a skin sensitizer.

Executive summary:

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.

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 25, 50 or 80% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with the vehicle alone (N,N-dimethylformamide (DMF)). Three days after the last exposure, all animals were injected with 3H-methyl 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.

Mean DPM/animal values for the experimental groups treated with test item concentrations 25, 50 and 80% were 512, 1357 and 674 DPM, respectively. The mean DPM/animal value forthe vehicle control group was 202 DPM. The SI values calculated for the test item concentrations 25, 50 and 80% were 2.5, 6.7 and 3.3, respectively.

These results indicate that the test item could elicit a SI ≥ 3. An EC3 value (the estimated test item concentration that will give a SI =3) of 28% was calculated.

The response of the 80% group did not follow the expected dose-response relationship which more often seen in these kind of studies. The response might be less due to differences in skin penetration (less vehicle present) or viscosity.

Based on these results the test item is considered to be a skin sensitizer.