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Description of key information

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented and reported study fully adequate for assessment. The study was conducted according to internationally accepted technical guidelines and in compliance with GLP in a recognized contract research organization.
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2002
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
of 2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)
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: Harlan UK.
- Age at treatment start (1st induction): Approx. eight to twelve weeks.
- Weight at treatment start (1st induction): Minimum 18.1 g, maximum 23.4 g.
- Housing: Individual housing in polycarbonate cages inside a barriered rodent facility.
- Bedding material: Woodflake bedding.
- Cage enrichment: Nestlets and mouse houses
- 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 environment, environmental conditions were set at:
- 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.



Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
Main Study:
Induction on Days 1, 2 and 3 at the following concentrations (v/v):
0% (vehicle control, 4 females), 25% (4 females), 50% (4 females), undiluted test material (4 females).

A range-finding test was not performed.
No. of animals per dose:
Main Study:
4 female animals per dose
Details on study design:
Compound Solubility:

A vehicle trial was conducted and WS400128 at 50% v/v in the vehicle, acetone:olive oil (4:1 v/v), formed a pale brown solution. WS400128 as supplied was slightly thicker than this solution and was considered suitable for use.

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 at the following concentrations (v/v) of test material in the vehicle:

Group 1 (Vehicle Control): 0%,
Group 2 (Low Dose): 25%,
Group 3 (Mid Dose): 50%,
Group 4 (High Dose): undiluted test material

The test substance preparations foreseen for treatment of Groups 2 and 3 were prepared on the day of dosing at the required concentrations.

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 for signs of irritation. In addition, bodyweights were recorded on Days 1 (prior to treatment) and 6 (three days after the third induction administration). On Day 6, all animals were injected into the tail vein 3H-methyl thymidine diluted in sterile 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. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed on Day 7. Radioactivity was expressed as the number of radioactive disintegrations per minute (dpm). The ratio of the proliferation (reflected by the magnitude of measured dpm/node) in treated groups to that in the vehicle control group, termed the stimulation index (SI), was subsequently calculated for each group.

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.
Positive control results:
A stimulation index (SI) of 6.0 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 acetone:olive (4:1 v/v), thus demonstrating the reliability and sensitivity of this test system and assay to detect skin sensitization potential in this laboratory.
Parameter:
SI
Remarks on result:
other: Stimulation Index (SI) values for the experimental groups treated with 25 and 50% v/v test substance dilutions and with undiluted test substance were 1.76, 2.02 and 2.96, respectively.
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: see Remark
Remarks:
Overall DPM/lymph node values for the experimental groups treated with 25 and 50% v/v test substance dilutions and with undiluted test substance were 1015.5, 1166.1 and 1710.6 DPM/node, respectively. For the vehicle control group, 577.8 DPM/node were recorded.

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 was noted for all control and test animals post-dose from Day 1. This finding had resolved

completely by Day 6 in Groups 1 and 2, whereas was still seen on Day 6 in Groups 3 and 4.

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

Interpretation of results:
not sensitising
Remarks:
Migrated information
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:
Migrated from Short description of key information:
In a local lymph node assay in mice, WS400128 was tested at concentrations of 25 and 50% (v/v) and as undiluted test substance. A mixture of acetone/olive oil (4:1 v/v) was used as a vehicle for administration to the low and mid dose groups.

Stimulation indices of 1.76, 2.02 and 2.96 were attained after induction treatment with WS400128 in the vehicle at 25 and 50% (v/v) and as undiluted test substance, respectively. Premature deaths, signs of ill health or toxicity or signs of local irritation over the treated area were not evident. The only finding noted was that of greasy fur, transient in the vehicle control and low dose group, whilst still present by day 6 (day of terminal sacrifice) in the mid and high dose groups.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:
Migrated from Short description of key information:
No data available.

Justification for classification or non-classification

At the 25 and 50% concentrations tested, the attained stimulation indices (S.I.) were well below the threshold value of 3 at and above which a test substance would be regarded to be a potential skin sensitizer. When undiluted WS400128 was tested, the S.I. was marginally lower than 3. Based on these results, WS400128 is considered not to be a skin sensitizer and does not warrant any classification regarding skin sensitisation according to European classification rules [REGULATION (EC) 1272/2008 and DIRECTIVE 67/548/EEC].