Didocosyl sebacate

Endpoint summary

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

Study period:

12 Jul - 24 Jul 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the appropriate OECD test guideline and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2010)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2008)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/Ca (CBA/CaOlaHsd)

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK, Ltd., Oxon, UK
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 15 – 23 g
- Housing: Animals were individually housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes.
- Diet: 2014C Teklad Global Rodent diet (Harlan Laboratories UK, Ltd., Oxon, UK), ad libitum
- Water: (tap/filtered) water, ad libitum
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 25
- Humidity (%): 30 - 70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Vehicle:

propylene glycol

Concentration:

- preliminary test: 10% (w/w)
- main test: 2.5, 5 and 10% (w/w)

No. of animals per dose:

4

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: highest concentration that was suitable for dosing: 10%
- Irritation: No signs of systemic toxicity, visual local skin irritation or irritation indicated by an equal to or greater than 25% increase in mean ear thickness were noted.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: 3H-methyl thymidine incorporation
- Criteria used to consider a positive response: The test item will be regarded as a sensitizer if at least one concentration of the test item results in a threefold or greater increase in 3HTdR incorporation compared to control values. Any test item failing to produce a threefold or greater increase in 3HTdR incorporation will be classified as a “non-sensitizer”.

TREATMENT PREPARATION AND ADMINISTRATION:
25 μL of the test item was applied to the dorsal surface of each ear of each mouse for three consecutive days; A further group of four mice received the vehicle alone in the same manner. Local irritation reactions were assessed. On day 6 an injection of 250 μL phosphate buffered saline (PBS) containing 20 μCi of 3H-methyl thymidine (3HTdR) was made into the tail vein of each experimental mouse. Five hours later, the draining auricular lymph node of each ear was excised and pooled for each experimental group. For each group 1 mL PBS was added to the pooled lymph nodes. A single cell suspension of pooled lymph node cells was prepared by gentle mechanical disaggregation through a 200-mesh stainless steel gauze. The lymph node cells were rinsed through the gauze with 4 mL of PBS into a petri dish labelled with the project number and dose concentration. The pooled lymph node cells were pelleted at 1400 rpm for ten minutes. The pellet was resuspended in 10 mL PBS. Radioactive material was precipitated with 3 mL of 5% trichloroacetic acid at 4 °C for 18 hours. 3HTdR incorporation was measured by β-scintillation counting.

Positive control substance(s):

other: phenylacetaldehyde (>90%)

Statistics:

Not applicable

Positive control results:

A group of five animals was treated with 50 μL of the positive control substance (>90%) as a solution in propylene glycol at a concentration of 2.5% (v/v). A further control group of five animals was treated with propylene glycol alone. The stimulation index expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group is 6.48. Therefore, phenylacetaldehyde (>90%) was considered to be a sensitizer under the conditions of the test.

Parameter:

SI

Remarks on result:

other: see Remark

Remarks:

A concentration of 2.5% of the test substance shows a stimulation index (SI) of 1.59. 5% of the test substance shows a SI of 1.45 and the highest concentration of 10% test substance shows a SI of 1.92. Based on this result, the test substance can be considered as a non-sensitizer.

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: see Remark

Remarks:

The number of disintegrations per minute (dpm) for the vehicle was 7715.90, resulting in a dpm/node of 964.49. A concentration of 2.5% of the test substance shows a dpm of 12276.85, and a dpm/node of 1534.61. 5% of the test substance shows a dpm of 11175.42, and a dpm/node of 1396.93. The highest concentration of 10% test substance shows a dpm of 14846.49 and a dpm/node of 1855.81.

Table 1: Disintegrations per minute, disintegrations per minute/node and stimulation index

Concentration (% in w/w) in propylene glycol	dpm	dpm/node	Stimulation index	Result
Vehicle	7715.90	964.49	NA	NA
2.5	12276.85	1534.61	1.59	Negative
5	11175.42	1396.93	1.45	Negative
10	14846.49	1855.81	1.92	Negative
Positive control	NA	NA	6.48	Positive

NA: not applicable

dpm: disintegrations per minute

CLINICAL OBSERVATIONS AND MORTALITY DATA

There were no deaths observed during the study period. No signs of systemic toxicity were noted in the test or control animals during the test.

BODYWEIGHT

Body weight change of the test animals between day 1 and day 6 was comparable to that observed in the corresponding control group animals over the same period.

Interpretation of results:

not sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

CLP: not classified

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin sensitization

The skin sensitizing properties of Didocosyl sebacate (CAS 42233-75-0) were tested in a study according to OECD TG 429 and in compliance with GLP using the local lymph node assay (LLNA) (Sanders, A., 2012e). In this study groups of four female CBA/CaOlaHsd mice were treated with the test item at concentrations of 2.5, 5 and 10% (w/w) (highest achievable concentration tested in a preliminary study) in propylene glycol. Topical application of 25 µL of the appropriate test substance concentrations was performed daily at the dorsal surface of each ear for three consecutive days. Five days following the first topical application of the test item or vehicle all mice were injected via the tail vain with 250 µL PBS containing ³H-methylthymidine (20 µCi per mouse). Five hours after injection single cell suspension of pooled lymph nodes was prepared of each group, followed by determination of ³HTdR incorporation. Positive and negative controls were included in the study and gave the expected results. The calculated stimulation indices (SI) of the test substance are 1.59, 1.45 and 1.92 at concentrations of 2.5, 5 and 10% (w/w), respectively and therefore < 3. Thus, under the conditions of the test, the test substance revealed no skin sensitizing properties.

Migrated from Short description of key information:
Skin sensitisation (LLNA, OECD 429): not sensitizing

Justification for selection of skin sensitisation endpoint:
The reliable GLP compliant OECD Guideline study was choosen.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The available data on the skin sensitization of the registered substance do not meet the criteria for classification according to Regulation (EC) No 1272/2008, and are therefore conclusive but not sufficient for classification.