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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2007-05-07 to 2007-05-21
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was performed according to the OECD guideline No.429 (April 2002) and in compliance with the GLP. A read-across approach using Ethyl trifluoroacetate as TFA similar structurally compound was considered as reliable to assess the sensitising potential of TFA since the ethyl group was not known to induce sensitisation in the literature.
Justification for type of information:
No studies for determination the sensitisation properties of TFA have been performed and none are proposed based on scientific considerations and for animal welfare reasons. ​In accordance with section 8.3, column 2, Annex VII of Regulation (EC) No. 1907/2006, the skin sensitisation study does not need to be conducted as the substance is a strong acid (pH =0.45; see § 4.20). However, a skin sensitization study with ethyl trifluoroacetate (CAS 383-63-1) according to OECD Guideline 429 and under GLP was identified and used as supporting study for the endpoint sensitization. Ethyl Trifluoroacetate (CAS 383-63-1) was identified as an analogue of TFA based on the similarity of its structure (ethyl group is bounded to the acid function) and considered as relevant to assess the sensitising potential of the salt moiety since the ethyl group is not known to induce sensitisation in the literature.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007
Report Date:
2007

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Trifluoroacétate d'éthyle, Ethyl trifluoroacetate, Ethyl Trifluoroaxetate
- Physical state: clear colorless liquid
- Lot/batch No.: TFAE-0703001
- Expiration date of the lot/batch: no data
- Stability under test conditions: assumed to be stable during the test (sponsor responsibility)
- Storage condition of test material: at room temperature and protected from light and humidity
- Other: no data

In vivo test system

Test animals

Species:
mouse
Strain:
other: CBA/J
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source : Janvier, Le GEnest-Saint-Isle, France
- Age at study initiation: 8 weeks old
- Weight at study initiation: 20.4 g (+/- 1.1 g)
- Housing: in individual crystal polystyrene cages (22.0 cm x 8.5 cm x 8.0 cm). Each cage contained autoclaved sawdust (SICSA, Alfortville, France).
- Diet (e.g. ad libitum): free access to SsniffR/M-H pelleted diet (SSNIFF Spezialdiäten GmbH, Soest, Germany)
- Water (e.g. ad libitum): free access to tap water (filtered using a 0.22 micron filter) contained in bottles.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C (+/- 2°C)
- Humidity (%): 30-70%
- Air changes (per hr): approximately 12 cycles per hour of filtered, non-recycled air
- Photoperiod (hrs dark / hrs light): 12h/12h

IN-LIFE DATES: From: To: no data

Study design: in vivo (LLNA)

Vehicle:
acetone/olive oil (4:1 v/v)
Remarks:
Acetone, batch No. I317112638 (Merck, Chelles, France); Olive oil, batch No. 046K6052 (Sigma, Saint-Quentin-Fallavier, France)
Concentration:
For the preliminary test the concentrations were 10, 25, 50 and 100% of the test item.
For the main test the concentrations were 0, 5, 10, 25, 50 and 100% of the test item.
No. of animals per dose:
For the preliminary test: 2 females/dose (no control): left ear and right ear were treated with different concentration of the test item.
For the main test: 4 females/dose, 4 females for the negative control and 4 females for the positive control (total of 28 animals)
See details on table 7.4.1/1
Details on study design:
RANGE FINDING TESTS:
- Compound solubility: The test item was soluble in the first recommended vehicle, acetone/olive oil (4/1, v/v). A solution was obtained at the maximum tested concentration of 50%.
- Irritation: Measurement of the ear thickness (using a micrometer) was performed each day before treatment and 72 hours after the last application. The test item was non-irritant in the preliminary test, whatever the concentration. The highest concentration retained for the main test was therefore the maximal practicable concentration (100%), according to the criteria specified in the International Guidelines.
- Lymph node proliferation response: no measurement

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Lymph node cell proliferative responses were measured as described by Kimber and Dearman (1991).
- Criteria used to consider a positive response: The results were expressed as disintegration per minute (dpm) per group and per node. Stimulation indices (SI) were calculated according to the following formula: SI = dpm of treated group / dpm of control group. The test item was considered as a skin sensitizer when the SI for a dose group is higher than or equal to 3. Other relevant criteria such as cellularity (amount of cells in treated group compared to the amount in control vehicle group), radioactivity levels and ear thickness were also taken into account for the interpretation of results.
TREATMENT PREPARATION AND ADMINISTRATION:
The test item was prepared in the vehicle at the chosen concentrations. All dosage form preparations were made freshly on the morning of the administration and any unused material was discarded that same day. On days 1, 2 and 3, a dose-volume of 25 μL of the control or dosage form preparations was applied to the dorsal surface of both ears, using an adjustable pipette fitted with a plastic tip. In order to avoid licking and to ensure an optimized application of the test materials, the animals were placed under light isoflurane anesthezia during the administration. No massage was performed but the tip was used to spread the preparation over the application sites. No rinsing was performed between each application.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
no data

Results and discussion

Positive control results:
In the positive control group given HCA at the concentration of 25%, a moderate increase in cellularity and a stimulation index exceeding the threshold value of 3 (SI=5.24) were noted.
The study was therefore considered valid.

In vivo (LLNA)

Resultsopen allclose all
Parameter:
SI
Value:
0.66
Test group / Remarks:
5 (v/v) %
Parameter:
SI
Value:
0.76
Test group / Remarks:
10 (v/v) %
Parameter:
SI
Value:
0.71
Test group / Remarks:
25 (v/v) %
Parameter:
SI
Value:
0.96
Test group / Remarks:
50 (v/v) %
Parameter:
SI
Value:
0.59
Test group / Remarks:
100%

Any other information on results incl. tables

No clinical signs and no mortality were observed during the study. The body weight gain of the treated animals was similar to that of the control animals. No cutaneaous reactions and no increase in ear thickness were observed at any of the test item tested concentrations.

The quantity of cells obtained in each group was satisfactory and the cellularity correlated with incorporation of 3H-TdR. The cell viability was higher than 80% in each group.

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Conclusions:
Under the test conditions, the test item Ethyl Trifluoroacetate does not induce delayed contact hypersensitivity in the murine Local Lymph Node Assay (stimulation index < 1).
Executive summary:

In a dermal sensitisation study performed according to the OECD guideline No.429 (April 2002) and in compliance with the GLP, ethyl trifluoroacetate (purity 99.94%) in acetone/olive oil was administered to CBA/J mice. The Lymph node proliferative responses were measured as described by Kimber and Dearman (1991). Ethyl Trifluoroacetate (CAS 383-63-1) was identified as a structural analogue of TFA and considred as relevant to assess the sensitising potential of TFA. In fact, the acid function substitution by the ethyl group represents the only difference between both substance structures (TFA and ethyl trifluoroacetate), while the ethyl group is not known to induce sensitisation in the literature.

The positive control used was HCA (α-hexylcinnamaldehyde) which presented a Stimulation index of 5.24.Therefore, the positive control gave acceptable positive results and the study can be considered valid.

No clinical signs and no mortality were observed during the study. Furthermore, no irritation of the skin was noted following the application of the test item. The LLNA gave negative results, as the SI is lower than 1 in the animals treated whatever the concentration of the test item.

Under the test conditions, the test item ethyl trifluoroacetate is not a dermal sensitizer in the murine Local Lymph Node Assay.

This study is considered as acceptable as it satisfies the main criteria of OECD guideline No. 429.