2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate

Endpoint summary

Description of key information

Skin sensitisation (QSAR target substance, GPMT source substance): not sensitising

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 Mar - 24 Apr 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

epicutaneous induction and challenge performed under semi-occlusive conditions

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Deviations:

yes

Remarks:

epicutaneous induction and challenge performed under semi-occlusive conditions

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

A non-LLNA test is available that was performed prior to the current data requirements, stipulated in Regulation (EC) No 1907/2006. In accordance with the same Regulation, the data was included to avoid unnecessary testing.

Species:

guinea pig

Strain:

Himalayan

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: BRL Ltd., Basel, Switzerland
- Age at study initiation: approximately 6 weeks
- Weight at study initiation: 416 ± 23 g (mean ± SD, control group); 434 ± 24 g (mean ± SD, treatment group)
- Housing: animals were housed in groups of 5 in labelled metal cages with wire-mesh floors (ITL, Bergen, the Netherlands)
- Diet: standard guinea pig diet (LC 23-B, pellet diameter 4mm, including ascorbic acid (1600 mg/kg); Hope farms, Woerden, the Netherlands), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21
- Humidity (%): 50
- Air changes (per hr): approximately 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 24 March 1998 To: 24 April 1998

Route:

other: intradermal and epicutaneous, semi-occlusive

Vehicle:

corn oil

Concentration / amount:

Induction: undiluted (intradermal and epicutaneous)
Challenge: undiluted

Route:

epicutaneous, semiocclusive

Vehicle:

corn oil

Concentration / amount:

Induction: undiluted (intradermal and epicutaneous)
Challenge: undiluted

No. of animals per dose:

10 (treatment group)
5 (control group)

Details on study design:

RANGE FINDING TESTS:
Prior to the start of the main study, the intradermal and epidermal irritancy of the test substance was investigated to select suitable concentrations for the induction and challenge phase of the main study. The selection was based on the absence of toxicity and on the following criteria for each route and/or study phase:
Induction (intradermal and epidermal): The highest possible concentration that produced moderate irritation (the intradermal reactions may include slight necrosis (< 3 mm in diameter)).
Challenge: The maximum non-irritant concentration.

A series of test substance concentrations were tested. The first and subsequent concentrations were selected from the series: 100% (undiluted), 50%, 20%, 10%, 5%, 2%, 1% and if needed, further lower concentrations using the same steps. The test system and procedures were identical to those used during the main study, unless otherwise specified. The four animals were 5-9 weeks old. The body weights were determined prior to treatment (results not shown).

Intradermal Injections:
A series of four test substance concentrations was used; the highest concentration was the maximum concentration that could technically be
injected (undiluted). One animal received 50 and 100% (undiluted), and the second animal received 10 and 20%, respectively, in duplicate (0.1 mL/site) in the clipped scapular region. The injection sites were assessed for irritation 24 and 48 hours after treatment. Slight erythema was observed at the injection site of the undiluted test substance 48 h after exposure. The udiluted test substance was selected for the induction phase in the main study.

Epidermal application:
A series of four test substance concentrations (10, 20, 50 and 100%) was used. All concentrations could technically be applied. Two different concentrations were applied (0.5 mL each) per animal to the clipped flank, using Metalline patches (2x3 cm) mounted on Medical tape, which were held in place with Micropore tape and subsequently Coban elastic bandage (semi-occlusive covering). The animals receiving intradermal injections were treated with the lowest concentrations (10 and 20%) and two further animals with the highest concentrations (50 and 100%). After 24 hours, the dressing was removed and the skin cleaned of residual test substance. The treated skin areas were assessed for irritation 24 and 48 hours after exposure. No skin irritation was observed at any of the treated sites at any of the reading time points. As the epidermal induction using the test substance did not cause any skin irritation, the test site of all animals was treated with 10% SDS approximately 24 hours before the epidermal induction in the main study, to provoke a mild inflammatory reaction. The udiluted test substance was selected for the challenge phase in the main study.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2, intradermal and epicutaneous
- Exposure period: single injection (epidermal) and 48 h (epicutaneous)
- Test groups:
Intradermal, Day 1 (3 pairs of injections, 0.1 mL/site):
Injection 1: a 1:1 mixture (w/w) Freunds Complete Adjuvant (FCA)/water for injection
Injection 2: undiluted test substance
Injection 3: undiluted test substance in a 1:1 mixture (w/w) with FCA (final concentration is 50% test substance)
48 h after intradermal injection (Day 3), the degree of erythema and edema was evaluated.

On Day 7, the scapular area between the injection sites was clipped and subsequently rubbed with 10% sodium dodecyl sulfate in vaseline using a spatula. This concentration of SDS provoked a mild inflammatory reaction.

Epicutaneous, Day 8:
0.5 mL undiluted test substance was applied to the SDS-treated skin area. The semi-occlusive dressing was kept in place for 48 h. The degree of erythema and edema was evaluated directly after cleaning the skin area with water (Day 10).

- Control group:
Intradermal, day 1 (3 pairs of injections, 0.1 mL/site):
Injection 1: a 1:1 mixture (w/w) FCA/water
Injection 2: corn oil
Injection 3: corn oil (w/v) in a 1:1 mixture (w/w) FCA (final concentration is 50% corn oil)

On Day 7, the scapular area between the injection sites was clipped and subsequently rubbed with 10% sodium dodecyl sulfate (SDS, Boom, Meppel, the Netherlands) in vaseline using a spatula. This concentration of SDS provoked a mild inflammatory reaction.

Epicutaneous, Day 8: 0.5 mL corn oil

- Site: the shoulder region
- Frequency of applications: once (intradermal on Day 1 and epicutaneous on Day 8)
- Duration: Day 1 (intradermal), Day 8-10 (epicutaneous)
- Concentrations: undiluted (intradermal and epicutaneous)

B. CHALLENGE EXPOSURE
- No. of exposures: 1 (challenge)
- Day(s) of challenge: 21
- Exposure period: 24 hours
- Test groups: 0.5 mL test substance
- Control group: 0.5 mL test substance
- Site: approximately 20 mm x 30 mm, on one flank of the animals
- Concentration: undiluted
- Evaluation (hr after challenge): 24 and 48 hours after the challenge ended

Positive control substance(s):

yes

Remarks:

alpha-hexylcinnamicaldehyde, tech. 85%

Positive control results:

A reliability check is carried out at regular intervals with alpha-hexylcinnamic aldehyde to check the sensitivity of the test system and the reliability of the experimental methods used by the test laboratory. In an independent study performed in 1998 (report No. 217812), alpha-hexylcinnamic aldehyde induced sensitisation in 80% (8/10) of the Himalayan guinea pigs challenged with a 10% solution, and in 70% (7/10) of the guinea pigs challenged with a 5% solution. A 5% solution was used for intradermal induction and undiluted test substance was used for topical induction.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: undiluted. No with. + reactions: 0.0. Total no. in groups: 5.0.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: undiluted. No with. + reactions: 0.0. Total no. in groups: 10.0.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

5%

No. with + reactions:

7

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

10%

No. with + reactions:

8

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: undiluted. No with. + reactions: 0.0. Total no. in groups: 5.0.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: undiluted. No with. + reactions: 0.0. Total no. in groups: 10.0.

48 hours after intradermal induction, slight to severe erythema was noted at all of the sites injected with FCA/water and FCA/test substance in 10/10 treated and 5/5 control animals. 4/5 control animals also exhibited necrosis at the FCA/test substance injection site. In 3/10 treated animals slight to well-defined erythema was observed at the injection site of the test substance. Following the topical induction, severe erythema and scabs were observed at the test site in 3/10 treated animals. A further 4/10 (in total 7/10) treated and 4/5 control animals exhibited only scabs. No edema was observed (see Table 1).

48 and 72 hours after the challenge, no sensitisation was observed in the treated animals.

There was no mortality, no signs of toxicity and no treatment-related effects on body weight.

Table 1: skin irritation effects of intradermal and epidermal induction

 

Group/ animal No.	Intradermal induction (Day 3), undiluted test substance			Epidermal induction (Day 10), undiluted test substance
Control	A	B	C	Erythema	Edema
16	E2	NA	E3	0p	0
17	E2	NA	N2	0a	0
18	E3	NA	N3	0a	0
19	E3	NA	N3	0	0
20	E2	NA	N3	0a	0
Experimental
21	E4	NA	E2	0a	0
22	E1	NA	E1	0	0
23	E2	E2	E2	0a	0
24	E2	NA	E1	0a	0
25	E1	NA	E1	4k	0
26	E1	NA	E1	0	0
27	E3	E1	E2	0a	0
28	E2	E1	E2	4s	0
29	E2	NA	E2	4k	0
30	E3	NA	E2	0	0

A. 1:1 mixture of FCA and water for injection

B. undiluted test substance (experimental group) or vehicle (control group)

C. 1:1 mixture of FCA and undiluted test substance (experimental group) or vehicle (control group)

a. small scabs

k. scabs

p. scaliness

s. eschar formation

 

Skin effect intradermal injections:

NA. No abnormalities

E. erythema

N. signs of necrosis (mm in diameter)

Interpretation of results:

other: CLP/EU GHS criteria not met, no classification required according to Regulation (EC) No 1272/2008.

Conclusions:

CLP: not classified

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Justification for read-across

There are no data on the skin sensitisation potential of 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8). The assessment was therefore performed based on QSAR modelling and a read across to an analogue (source) substance as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. For each specific endpoint the source substance(s) structurally closest to the target substance is/are chosen for read-across, with due regard to the requirements of adequacy and reliability of the available data. Structural similarities and similarities in properties and/or activities of the source and target substance are the basis of read-across. A detailed justification for the analogue read-across approach is provided in the technical dossier (see IUCLID Section 13).

Skin sensitisation

QSAR predictions

CAS 97338-28-8

The potential for 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate to show skin sensitising properties, was predicted in the QSAR OECD Toolbox (supporting, 2017). There was no alert for skin sensitisation potential, estimated based on protein binding potential, in the database OASIS v1.4.

 

Animal data

CAS 93803-87-3

A Guinea pig maximisation test was performed with 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) under GLP conditions and using a protocol similar to OECD Guideline 406 (key, 1998). 10 test and 5 control Himalayan guinea pigs were induced intradermally with undiluted test substance on both sides of the spine with and without Freud's complete adjuvant. On Day 7, the animals were treated with 10% sodium dodecyl sulfate to induce mild skin irritation.On Day 8, a 48-h epicutaneous induction treatment with the undiluted test substance was performed under semi-occlusive conditions. On Day 22, the challenge treatment was performed by topical application of the test substance at 100% (right flank) and a blank patch (left flank) to all animals for 24 h, under semi-occlusive conditions. Skin reactions were evaluated 24 and 48 h after the challenge application. During the study, no test substance-related clinical signs and no effects on body weight gain were observed. 8 h after intradermal induction, slight to severe erythema was noted at all of the sites injected with FCA/water and FCA/test substance in 10/10 treated and 5/5 control animals. 4/5 control animals also exhibited necrosis at the FCA/test substance injection site. In 3/10 treated animals slight to well-defined erythema was observed at the injection site of the test substance. Following the topical induction, severe erythema and scabs were observed at the test site in 3/10 treated animals. A further 4/10 (in total 7/10) treated and 4/5 control animals exhibited only scabs. No skin reactions were observed after the challenge treatment in any of the animals of the test and control groups. The results of the reliability check carried out at regular intervals were positive, confirming the reliability of the assay. Based on the results, the test substance had no sensitising effect in guinea pigs under the experimental conditions.

 

Overall conclusion for skin sensitisation

The OECD QSAR Toolbox (OASIS v1.4 database) did not predict skin sensitising properties of the target substance, based on protein binding potential. A GPMT study performed with the source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was negative. Taking into account the available information, 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate is not expected to be skin sensitising.

Justification for classification or non-classification

According to Article 13 of Regulation (EC) No. 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X” states that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint". Since the analogue concept is applied to 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8), data will be generated from data for reference source substance(s) to avoid unnecessary animal testing. Additionally, once the analogue read-across concept is applied, substances will be classified and labelled on this basis.

Therefore, based on the analogue read-across approach, the available data on skin sensitisation do not meet the classification criteria according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification.