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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation, other
Remarks:
conclusion on the in vitro/in chemico/in silico studies
Type of information:
other: expert report
Adequacy of study:
supporting study
Study period:
November 2018
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019
Report date:
2019

Materials and methods

Type of study:
other: summary of available report

Test material

Constituent 1
Chemical structure
Reference substance name:
3-benzoyloxy-2,2,4-trimethylpentyl isobutyrate
EC Number:
245-054-8
EC Name:
3-benzoyloxy-2,2,4-trimethylpentyl isobutyrate
Cas Number:
22527-63-5
Molecular formula:
C19H28O4
IUPAC Name:
[2,2,4-trimethyl-1-(2-methylpropanoyloxy)pentan-3-yl] benzoate
Constituent 2
Chemical structure
Reference substance name:
2,2,4-trimethylpentane-1,3-diyl dibenzoate
EC Number:
268-316-3
EC Name:
2,2,4-trimethylpentane-1,3-diyl dibenzoate
Cas Number:
68052-23-3
Molecular formula:
C22H26O4
IUPAC Name:
(3-benzoyloxy-2,2,4-trimethylpentyl) benzoate
Constituent 3
Chemical structure
Reference substance name:
1-isopropyl-2,2-dimethyltrimethylene diisobutyrate
EC Number:
229-934-9
EC Name:
1-isopropyl-2,2-dimethyltrimethylene diisobutyrate
Cas Number:
6846-50-0
Molecular formula:
C16H30O4
IUPAC Name:
[2,2,4-trimethyl-3-(2-methylpropanoyloxy)pentyl] 2-methylpropanoate
Test material form:
liquid
Details on test material:

- Density: 1.027
- Moisture content: 0.02%
Specific details on test material used for the study:

Chemical name Reaction mass of 2,2,4-trimethylpentane-1,3-diyldibenzoate and 3-benzoloxy-2,2,4-trimethylpentylisobutyrate and 1-isopropyl-2,2-dimethyltrimethylene diisobutyrate
CAS number Not available
Molecular weight Not available – not a single substance
UVCB No

Results and discussion

Any other information on results incl. tables

DEREK NEXUS version 6.0.1 did not yield any alerts for skin sensitization for the test item.

Additionally, the query structure does not contain any unclassified or misclassified features and is consequently predicted to be a non-sensitizer. The test substance is predicted to be not sensitizing to the skin.

 

A valid DPRA test was performed according to OECD TG 442C and GLP principles. For the DPRA, the test substance was dissolved in acetonitrile at 100 mM and formed a clear solution by visual inspection.No co-elution of the test item with SPCC or SPCL was observed.In the cysteine reactivity assay the test item showed 19.1% SPCC depletion, and in the lysine reactivity assay the test item showed 0.1% SPCL depletion. The mean of the SPCC and SPCL depletion was 9.6%. As a result, the test substance was positive in the DPRA and was classified in the “lowreactivityclass” when using the Cysteine 1:10 / Lysine 1:50 prediction model. However, since phase separation was observed after the incubation period for both SPCC and SPCL,one cannot be sure how much test item remained in the solution to react with the peptides. Consequently,the percentages of SPCC and SPCL depletion might be underestimated.

 

A valid KeratinoSensTM assay was performed according to OECD TG 442D and GLP principles. For the KeratinoSensTM assay, the test item was dissolved in DMSO to final concentrations of 40 mg/mL and 5 mg/mL. From both stocks 11 spike solutions in DMSO were prepared. The stock and spike solution were diluted 25-fold with exposure medium. These solutions were diluted 4-fold in the assay resulting in final test concentrations. Two independent tests were performed. In the first experiment the cells were incubated with the test item in a concentration range of 0.2400µg/mL (2-fold dilution series) for 48 hours. Precipitation was observed at the start the incubation period at concentrations of 100 µg/mL and upwards in experiment 1. Due to toxicity, the test concentrations used for the second experiment were in a concentration range of 4.350 µg/mL (1.25-fold dilution steps). The substance showed toxicity (IC30 values of 21µg/mL and 18µg/mL and IC50values of 24µg/mL and 20 µg/mL in experiment 1 and 2, respectively). A biologically relevant, dose-related induction of the luciferase activity (EC1.5 values of 8.7µg/mLand 8.5µg/mLin experiment 1 and 2, respectively) was measured in both experiments. The maximum luciferase activity induction (Imax) was 2.64-fold and 2.06-fold in experiment 1 and 2 respectively. The test substance is classified as positive in the KeratinoSensTM assay since positive results (>1.5-fold induction) were observed at test concentrations < 200µg/mLwith a cell viability of >70% compared to the vehicle control.

Applicant's summary and conclusion

Conclusions:
In conclusion, from the current study data it can be concluded that Reaction Mass of 1-isopropyl-2,2 dimethyltrimethylene diisobutyrate and 3-benzoyloxy-2,2,4-trimethyl pentyl isobutyrate and 2,2,4-trimethylpentane-1,3-diyl dibenzoate has skin sensitizing properties, but information on skin sensitization potency is lacking in these studies. In the absence of a reliable and acceptable in vitro skin sensitization potency test, an in vivo test needs to be performed.
Executive summary:

DEREK NEXUS predicted a negative result, whereas the DPRA and the KeratinoSensTM assay were both positive. Based on the two in vitro assays the test substance is considered to be a skin sensitizer. Due to the negative result in DEREK, no prediction is available on skin sensitizing potency. In addition, current in vitro assays lack to provide reliable information on skin sensitization potency. Therefore, performance of an additional in vitro assay (STEP 2) addressing the activation of dendritic cells would not yield additional information on skin sensitizing potency, irrespective of a negative or positive result. Therefore it is considered justified to omit further in vitro testing and perform an in vivo test to get reliable information on skin sensitizing potency for the substance.