Registration Dossier

Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Read-across from GLP-compliant guideline study performed with similar substance.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2014
Report Date:
2014

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2010
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2008 as amended 2012
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of study:
mouse local lymphnode assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder

In vivo test system

Test animals

Species:
mouse
Strain:
CBA
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Mouse (healthy females only), strain: CBA/Ca with appropriate range of bodyweight at study start.
- Source: Charles River (UK) Ltd.
- Age at treatment start (1st induction): Eight to ten weeks.
- Weight at treatment start (1st induction): Minimum 17.9 g, maximum 21.9 g.
- Housing: Two animals per polycarbonate cage inside a barriered rodent facility.
- Bedding material: Woodflake bedding.
- Cage enrichment: Nestlets and plastic shelter
- Diet (ad libitum): Standard rodent diet (Rat and Mouse No. 1 Maintenance Diet) containing no added antibiotic,
chemotherapeutic or prophylactic agent.
- Water (ad libitum): Tap water
- Acclimation period: At least 6 days before treatment start under laboratory conditions.

Analysis of the batch of diet used and water did not provide evidence of contamination that might have prejudiced the study.

ENVIRONMENTAL CONDITIONS

Air conditioned room kept at positve pressure without re-circulation of the filtered fresh air supplied to the room.
Controlled environmental conditions were set at:
- Air changes per hour in the animal room: controlled periodically
- Temperature (°C): 21 ± 2°C
- Relative Humidity (%): 40 to 70%
- Photoperiod (artificial lighting): 12 hrs day / 12 hrs night
There was no mentioning of any deviations from these ranges, which compromised the integrity or validity of the study.



Study design: in vivo (LLNA)

Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
Main Study:
0, 5, 10, and 25%

WS405777 was unsuitable for dosing at 50% in any of the vehicles stated in the protocol; 25% was the maximum achievable concentration.
No. of animals per dose:
Main Study:
4 female animals per dose
Details on study design:
Compound Solubility:

WS405777 was unsuitable for dosing at 50% in any of the vehicles stated in the protocol; 25% was the maximum achievable concentration forming a white suspension.

Treatment Preparation and Administration:

On three consecutive days, groups of 4 female mice were treated by topical application to the entire dorsal surface of both ears with 25 μL/ear/day at the following concentrations (w/v) of test substance in the vehicle: 0, 5, 10, and 25%, respectively.

The test substance preparations were prepared freshly on each day of administration.

Observations, Measurements and Endpoints (Pooled treatment group approach):

All animals were checked daily for signs of ill health or toxicity. The ears were also examined daily for signs of irritation. In addition, bodyweights were recorded on Days 1 (prior to treatment) and 6 (prior to termination). On Day 6, all animals were injected into the tail vein 3H-methyl thymidine diluted in phosphate buffered saline at a nominal dose of 20 µCi per mouse, in order to measure lymphocyte proliferation by radioactive labelling. Five hours afterwards the draining (auricular) lymph nodes were excised and pooled for each experimental group. Single cell suspensions were prepared for determination of incorporated radioactivity.

Criteria Used to Consider a Positive Response:

The test substance is regarded as a sensitizer if at least one concentration of the test substance produces a stimulation index (SI) ≥ 3.


Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Data were not statistically analysed.

Results and discussion

Positive control results:
A stimulation index (SI) of 8.7 was attained in a contemporaneous positive control assay with the same strain of mice (CBA/Ca) in response to 25% v/v hexyl cinnamic aldehyde in AOO, thus demonstrating the reliability and sensitivity of this test system and assay to detect skin sensitization potential in this laboratory.

In vivo (LLNA)

Resultsopen allclose all
Parameter:
SI
Remarks on result:
other: Stimulation Index (SI) values for the experimental groups treated with 5, 10, and 25 % w/v test substance dilutions were 0.9, 1.2, and 1.2, respectively.
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Overall DPM/lymph node values for the experimental groups treated with 5, 10, and 25% w/v test substance dilutions were 510, 628, and 681 DPM/node, respectively. For the vehicle control group, 546 DPM/node were recorded.

Any other information on results incl. tables

Mortality / clinical signs:

There were no deaths, no signs of ill health or toxicity and no signs of local irritation over the treated area. Greasy fur on the head was noted following each dosing occasion.

Body weight: There was no indication of adverse effects on bodyweight attributable to treatment with the test substance.

As outlined in the „Validity Assessment Report“ for the read-across approach (see IUCLID Section 13) read-across from testing data obtained with the UVCB substance WS405777 is considered appropriate for the safety evaluation as well as classification and labelling of the mono-constituent substance WS406663 based on the close chemical similarity between the two substances.

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Executive summary:

As outlined in the „Validity Assessment Report“ for the read-across approach (see IUCLID Section 13) read-across from testing data obtained with the UVCB substance WS405777 is considered appropriate for the safety evaluation as well as classification and labelling of the mono-constituent substance WS406663 based on the close chemical similarity between the two substances.

WS406663 does not necessitate any classifcation regarding skin sensitisation.