4,4'-thiodiethylene hydrogen -2-octadecenylsuccinate

Endpoint summary

Description of key information

Based physical chemical characteristics of the Substance there is high uncertainty regarding the applicability to the current in vitro studies, therefore the predictions are unlikely to be meaningful and/or represent the true hazard of the Substance. In conclusion it was considered appropriate to conduct an in vivo study approach to minimise the uncertainty for this Substance.

The Substance is considered to be amphiphilic and therefore would likely have surfactant characteristics, which is known to be falsely positive in the LLNA. Therefore a Guinea Pig Study, OECD 406, was conducted.

Based on the results of the OECD 406 study, the Substance s considered to be a contact sensitizer in guinea pigs as >15% of the test animals responded at challenge.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

The current in vitro studies were considered against the properties of the Substance. Extracts of the applicability and limitation from the respective OECD guidelines for each study have been highlight below.

OECD 442E (h-CLAT) – The guidelines state, “Test chemicals with a Log Kow greater than 3.5 tend to produce false negative results. Therefore negative results with test chemicals with a Log Kow greater than 3.5 should not be considered.”

OECD 442D (ARE-Nrf2 Luciferase Test Method) – The guidelines state, Test substances with a LogP of up to 5 have been successfully tested whereas extremely hydrophobic substances with a LogP above 7 are outside the known applicability of the test method.”

OECD 442C – The guidelines state, “The current prediction model cannot be used for complex mixture of unknown composition or for substances of unknown or variable composition, complex reaction products or biological materials (i.e. UVCB substances) due to the defined molar ration of test chemical and peptide.”

The Substance is considered to be extremely hydrophobic and has a Log Kow of >6.5 (Estimated 17-18.3) and additionally it is considered to be a UVCB. Data generated from the in vitro approaches are normally considered in the context of integrated approaches and individual studies are to be used as a weight of evidence. Based physical chemical characteristics of the Substance there is high uncertainty regarding the applicability to the current in vitro studies, therefore the predictions are unlikely to be meaningful and/or represent the true hazard of the Substance. In conclusion it was considered appropriate to conduct an in vivo study approach to minimise the uncertainty for this Substance.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12th Ocotober 2015 - 15th March 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

The LLNA is the study of choice for skin sensitisation. As detailed in the OECD 429 guideline, despite the advantages of the LLNA, it should be recognised that there are certain limitations that may necessitate the use of TG 406. Chemical groups such as metal salts, organometal, unsaturated compounds and surfactants have been known to be linked to false positive. The Substance is considered to be amphiphilic in nature and therefore would likely have surfactant characteristics, which are known to be falsely positive in the LLNA. Therefore a Guinea Pig Study, OECD 406, was selected to decrease the uncertainty of possible falsely positive effects.

Specific details on test material used for the study:

Batch (Lot) No.: E00268-011-113/E00350-276
Receipt Date: 28 Sep 2015
Retest Date: 26 Mar 2017
Physical Description: Brown waxy solid
Purity: 100%; dose calculations were not corrected for purity
Storage Conditions: Kept in a controlled room temperature area

Species:

guinea pig

Strain:

Hartley

Remarks:

Hartley-derived albino guinea pig

Sex:

male/female

Details on test animals and environmental conditions:

Justification for Test System and Number of Animals: The Hartley-derived guinea pig was chosen as the animal model for this study as it is an accepted rodent species for preclinical toxicity testing by regulatory agencies. The total number of animals used in this study was considered to be the minimum required to properly characterize the effects of the test substance. This study was designed such that it did not require an unnecessary number of animals to accomplish its objectives. At this time, studies in laboratory animals provide the best available basis for extrapolation to humans and are required to support regulatory submissions. Acceptable models which do not use live animals currently do not exist.

Animal Identification: Each animal was identified by a cage card and plastic ear tag.

Environmental Acclimation: The animals were acclimated to their designated housing for at least 15 days before the first day of dosing.

Selection, Assignment, and Disposition of Animals: The animals chosen for study were arbitrarily selected from healthy animals. All animals received a detailed pretest observation prior to dosing. Only healthy animals were chosen for
study use. The male range-finding animals were approximately 6 weeks of age on the day prior to dosing with body weights of 358 grams and 370 grams. The female range-finding animals were approximately 7 weeks of age on the day prior to dosing with body weights of 360 grams and 362 grams.

The male main phase animals were approximately 7 weeks of age on the day prior to Induction 1 dosing with body weights ranging from 429 grams to 563 grams. The female main phase animals were approximately 8 weeks of age on the day prior to Induction 1 dosing with body
weights ranging from 402 grams to 515 grams.

The male second range-finding animals were approximately 10 weeks of age on the day prior to dosing with body weights of 596 grams and 644 grams. The female second range-finding animals were approximately 11 weeks of age on the day prior to dosing with body weights of 496 grams and 549 grams.

The disposition of all animals was documented in the Study Records.

Housing
The animals were pair housed (2 animals of the same sex and same dosing group together) throughout the study in polycarbonate cages containing direct bedding material. As an alternative, guinea pigs were individually housed in solid bottom cages containing a hiding
device and direct bedding material. Housing and care were as specified in the USDA Animal Welfare Act (9 CFR, Parts 1, 2, and 3) and as described in the Guide for the Care and Use of Laboratory Animals from the National Research Council.

Environmental Conditions
Temperatures of 68°F to 72°F (20°C to 22°C) with a relative humidity of 45% to 55% were maintained. A 12-hour light/12-hour dark cycle was maintained, except when interrupted for designated procedures. Ten or greater air changes per hour with 100% fresh air (no air
recirculation) were maintained in the animal rooms.

Food
PMI Nutrition International Certified Guinea Pig Chow No. 5026 was provided ad libitum throughout the study, except during designated procedures. The feed was analyzed by the supplier for nutritional components and environmental contaminants. Results of the dietary
analyses were provided by the supplier for each lot of diet and are on file at the Testing Facility. It is considered that there are no known contaminants in the feed that would interfere with the objectives of the study.

Water
Municipal tap water after treatment by reverse osmosis and ultraviolet irradiation was freely available to each animal via an automatic watering system, except during designated procedures. Water bottles were offered when required. The water is analyzed semi-annually for microbial contamination and for total dissolved solids, hardness, and various environmental contaminants. Results of these analyses are maintained on file at the Testing Facility. It is considered that there are no known contaminants in the water that could interfere with the outcome of the study.

Animal Enrichment
Beginning at receipt, guinea pigs were pair housed in solid bottom cages containing direct bedding material. As an alternative, guinea pigs were individually housed in solid bottom cages containing direct bedding material. When individually housed, a hiding comfort device (PVC
pipe) was provided. In addition, a Timothy Hay Cube was provided to each animal at least weekly.

Veterinary Care
Veterinary care was available throughout the course of the study; however, no examinations or treatments were required.

Route:

epicutaneous, occlusive

Vehicle:

polyethylene glycol

Concentration / amount:

100% / 0.3 mL

Day(s)/duration:

Day1, 7 & 14/ ~ 6 hours

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

corn oil

Concentration / amount:

75%, 0.3 mL

Day(s)/duration:

Day 29/ 6 hour

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

10 animals per sex for main study test group
5 animals per sex for main study control group

Details on study design:

The dermal sensitization potential of the Substance was evaluated in Hartley-derived albino guinea pigs. Ten male and 10 female guinea pigs were topically treated with the Substance, as received, once per week, for 3 consecutive weeks. Following a 2-week rest period, a challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated with 75% the Substance in PEG 400.

Challenge controls:

On the day prior to challenge dose administration, the test, HCA test, challenge control, and HCA challenge control animals were weighed and the hair was removed from the right side of the animals. On the day following clipping (Day 28), Hilltop chambers were applied.

Positive control substance(s):

yes

Remarks:

a-Hexylcinnamaldehyde (HCA)

Positive control results:

The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

75%

No. with + reactions:

20

Total no. in group:

20

Clinical observations:

No Susbstance related clinical signs were noted during the study.

Remarks on result:

positive indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

75%

No. with + reactions:

12

Total no. in group:

20

Clinical observations:

No Substance related clinical signs were noted during the study.

Remarks on result:

positive indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

75%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No Substace related clinical signs were noted during the study.

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

75%

No. with + reactions:

3

Total no. in group:

10

Clinical observations:

No Substace related clinical signs were noted during the study.

Remarks on result:

other:

Remarks:

3 animals were observed with skin scores of 1

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

2.5%

No. with + reactions:

10

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

2.5%

No. with + reactions:

10

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

1%

No. with + reactions:

9

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

1%

No. with + reactions:

9

Total no. in group:

10

Remarks on result:

positive indication of skin sensitisation

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Conclusions:

Based on the results of this study, Substance is considered to be a contact sensitizer in guinea pigs, as > 15% of the test animals responded at challenge.

Executive summary:

The dermal sensitization potential of Substance was evaluated in Hartley-derived albino guinea pigs. Ten male and 10 female guinea pigs were topically treated with Substance, as received, once per week, for 3 consecutive weeks. Following a 2-week rest period, a challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated with 75% Substance in PEG 400.

 

An a-Hexylcinnamaldehyde (HCA) positive control group consisting of 10 HCA test and 10 HCA control guinea pigs was included in this study. The animals were treated as above with the HCA test animals receiving 5% w/v HCA in ethanol for induction and 2.5% and 1.0% w/v HCA in acetone for challenge.

 

Following challenge with 75% Substance in PEG 400, dermal scores of 1 or 2 were noted in 20/20 test animals at the 24-hour scoring interval. At the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test and 3/10 challenge control animals. Dermal reactions in the remaining challenge control animals were scores of 0 or ±. Group mean dermal scores were higher in the test animals (1.4 to 1.6) as compared to challenge control animals (0.0 to 0.6).

 

Based on the results of this study, Substance is considered to be a contact sensitizer in guinea pigs, as > 15% of the test animals responded at challenge. The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Skin sensitisation (in vitro)

Based physical chemical characteristics of the Substance there is high uncertainty regarding the applicability to the current in vitro studies, therefore the predictions are unlikely to be meaningful and/or represent the true hazard of the Substance. In conclusion it was considered appropriate to conduct an in vivo study approach to minimise the uncertainty for this Substance.

Skin sensitisation (in vivo)

The Substance is considered to be amphiphilic and therefore would likely have surfactant characteristics, which is known to be falsely positive in the LLNA. Therefore a Guinea Pig Study, OECD 406, was conducted.

The dermal sensitization potential of Substance was evaluated in Hartley-derived albino guinea pigs. Ten male and 10 female guinea pigs were topically treated with Substance, as received, once per week, for 3 consecutive weeks. Following a 2-week rest period, a challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated with 75% Substance in PEG 400.

 

An a-Hexylcinnamaldehyde (HCA) positive control group consisting of 10 HCA test and 10 HCA control guinea pigs was included in this study. The animals were treated as above with the HCA test animals receiving 5% w/v HCA in ethanol for induction and 2.5% and 1.0% w/v HCA in acetone for challenge.

 

Following challenge with 75% Substance in PEG 400, dermal scores of 1 or 2 were noted in 20/20 test animals at the 24-hour scoring interval. At the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test and 3/10 challenge control animals. Dermal reactions in the remaining challenge control animals were scores of 0 or ±. Group mean dermal scores were higher in the test animals (1.4 to 1.6) as compared to challenge control animals (0.0 to 0.6).

 

Based on the results of this study, Substance is considered to be a contact sensitizer in guinea pigs, as > 15% of the test animals responded at challenge. The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.

Justification for classification or non-classification

The skin sensitisation study was conducted on the registered substance according to OECD Testing Guideline 406. Following a challenge exposure with the Substance, dermal scores of 1 or 2 were noted in 20/20 test animals at the 24 -hour observation, and in 20/20 test animals at 48 -hour observation. Score of 1 were also noted in 3/10 control animals at the 48 hour observation. Based on the result as >15% of the test animals responded at challenge, the test item was classified as sensitising according to Regulation (EC) No.1272/2008 on the Classification, Labelling and Packaging of Substances and Mixtures. The Substance will be classified as a skin sensitiser category 1 with the hazard statement H317: May cause an allergic skin reaction.There is insufficient data to classify into sub-categories.