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Toxicological information

Skin sensitisation

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Administrative data

skin sensitisation, other
Type of information:
Adequacy of study:
supporting study
Study period:
Not stated
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Data source

Reference Type:
A quantitative structure-toxicity relationships model for the dermal sensitization guinea pig maximisation assay
Enslien, K., Gombar,V.K., Blake, B.W., Maibach, H.I., Hostynek,J.J., Sigman, C.G. and Bagheri, D.
Bibliographic source:
Food and Chemcal Toxicology 35 (1997) 1091-1098

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
The authors developed quantitative structure-toxicity relationship (QSTR) models for assessing dermal sensitization using guinea pig maximization test (GPMT) results. The models are derived from 315 carefully evaluated chemicals. There are two models, one for aromatics (excluding one-benzene-ring compounds), and the other for aliphatics and one-benzene-ring compounds. For sensitizers, the models can resolve whether they are weak/moderate or severe sensitizers. The statistical methodology, based on linear discriminant analysis, incorporates an optimum prediction space (OPS) algorithm. This algorithm ensures that the QSTR model will be used only to make predictions on query structures which fall within its domain. Calculation of the similarities between a query structure and the database compounds from which the applicable model was developed are used to validate each skin sensitization assessment, the cross-validated specificity of the equations ranges between 81 and 91%, and the sensitivity between 85 and 95%. For an independent test set, specificity is 79%, and sensitivity 82%.
GLP compliance:
not specified

Test material

Details on test material:
315 chemicals were assessed for sensitising potential - divided into two groups - aliphatics and single benzene ring compounds and aromatics excluding single benzene ring structures. One of te test materials used to assess the predictivity ofthe QSAR model compared with maximisation results from a guinea pig Magnuson & Kligman design study was, 2-ethylhexyl palmitate. No further test material details are available

In vivo test system

Test animals

other: QSAR modelling
not specified
not specified
Details on test animals and environmental conditions:
The QSAR results are compared with data from guinea pig studies entered into TOPKAT - no further details available

Results and discussion

Positive control results:
Not applicable

In vivo (non-LLNA)

other: QSAR evaluation
other: QSAR
Remarks on result:
other: Reading: other: QSAR evaluation. Group: other: QSAR.

Any other information on results incl. tables

Ethylhexyl palmitate was identified as a non-sensitiser.

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Migrated information
Ethylhexyl palmitate was identified as a non-sensitiser in literature and this evaluation was confirmed by the QSAR model described in this paper
Executive summary:

The salient differences of this QSTR model for skin sensitization based on the GPMT assay compared with prior publications include: (1) a considerably larger training set, and thus broader application domain encompassing wider chemical diversity.

(2) that the model resolves the strength of sensitization into weak/moderate and strong categories

(3) that the use of OPS ensures that only query compounds that fit within the model's domain will be assessed, thus avoiding the production and distribution of invalid results--this capability does not, and cannot, exist in expert systems such as DEREK.

The limitations of this QSTR model are basically:

(I) that the GPMT, due to its very nature, tends to overpredict sensitization compared with assays in humans,

(2) that the training set, extensive though it may be, does not encompass as many compounds and as much chemical diversity as one might wish --the release of proprietary data by manufacturers would greatly remediate this problem; and

(3) no account has been taken of previously identified modes of a c t i o n - - b e t t e r models would probably result if submodels were limited to compounds with a single mode of action

Despite these relative pros and cons, the QSAR model did predict the nonsensitising nature of Ethylhexyl palmitate, as indicated in prior literature.