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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2019
Reliability:
1 (reliable without restriction)
Justification for type of information:
A skin sensitization can be considered as allergic response in animals or humans caused by sensitizer agent.
The aim of the study was to estimate the skin sensitization (human health toxicity testing) of target substance.
Estimation of the biological activity (skin sensitization)
The computational simulation was performed based on the read-across approach. The readacross is one of the so-called alternative test methods recommended by REACH, where the predictions are based on the experimental data available for the most similar compounds. The predictions were performed according to the Read-Across Assessment Framework (RAAF), which assumes six different risk assessment scenarios of chemical compounds.

Data source

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

Materials and methods

Principles of method if other than guideline:
The computational simulation was performed based on the read-across approach. The readacross is one of the so-called alternative test methods recommended by REACH, where the predictions are based on the experimental data available for the most similar compounds. The predictions were performed according to the Read-Across Assessment Framework (RAAF), which assumes six different risk assessment scenarios of chemical compounds.
Applied tool:
The OECD QSAR Toolbox, version 4.3
Procedure of analysis:
I. Profiling of the target substance in order to retrieve relevant information related to mechanism of action and observed or simulated metabolites
II. Analogue (source compound) search based on selected criteria:
- analogues have the same protein binding alert responsible for the toxic effect based on the Protein Binding by OECD profiler
- analogues are classified as ‘Lactones’ according to Protein Binding Potency h-CLAT
- analogues are structurally similar to the target compound (similarity >50%)
III. Data collection for the analogues (OECD Toolbox database/ECHA CHEM).
IV. Toxicity prediction for the target substance
V. Category consistency check in order to assess the quality of the prediction
Applied scenario:
Scenario 2
Toxicity prediction for the target substance:
This read-across is based on the fact that the organism is not exposed to common compounds but rather, as a result of similarity, to chemicals which have similar (eco)toxicological and fate properties.
The target substance is an organometallic compound containing vanadium (IV) centres, ascorbate (Asc) ligands. The metallic centres of the substance are linked by oxygen
coordination bonds of the Asc ligands.
The target and source chemicals are classified as “Lactones” according to Protein binding by h-CLAT Categories and have the similar protein binding alert responsible for the toxic effect based on the Protein binding by OECD profiler. Moreover, analogues are structurally similar to the target compound in more than 50%. One compound that met these requirements was found (sodium L-ascorbate, CAS 134-03-2).
The skin sensitization for the source compound was performed according to:
Test guideline: OECD 429
Endpoint: skin sensitization
Test organism: mouse LLNA
The read-across prediction of the skin sensitisation for the target substance was performed based on the “one to one” approach.

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

In vivo (LLNA)

Results
Key result
Remarks on result:
no indication of skin sensitisation based on QSAR/QSPR prediction

Any other information on results incl. tables

In order to meet regulatory needs, reliability of the predicted results should be assessed. In case of classic quantitative structure-activity relationships (QSAR) modelling, this idea can be realised by analysing, whether the predicted value is located within so-called applicability domain. The applicability domain is a theoretical region, defined by the range of toxicity values and structural descriptors for the training compounds, where the predictions may be considered as realistic ones. In a specific case of read-across, the assessment is performed based on the assessment of degree of similarity between the source and target compounds (in %). Moreover, the internal consistency of the group of source compounds (called „category” in OECD Toolbox nomenclature, independently which approach: analogue approach or category approach is used). The category consistency check could be based on the parameters describing the structural similarity and/or properties as well as mechanistic similarity of the tested compounds.

For example, all members of the category (analogues as well as target substance) need to have the same functional groups and endpoint specific alerts.

In the case of read-across-based prediction of the skin sensitization of the vanadyl (IV) diascorbate dihydrate, the read-across hypothesis considers that source and target compounds are classified as “Lactones” according to Protein binding by h-CLAT Categories and have the similar protein binding alert responsible for the toxic effect based on the Protein binding by OECD profiler. Moreover, based on the Dice measure analogue is structurally similar to the target compound in more than 50%.

Besides, the category consistency, the boundaries of the applicability domain are verified by the critical value of log KOW. In case of vanadyl (IV) diascorbate dihydrate, log KOW value in unavailable thus information that “domain is not defined” is not critical in this situation.

The structural similarity between the source (sodium L-ascorbate) and the target compound (vanadyl (IV) diascorbate dihydrate) equals to 53.7 %

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The skin sensitization for the target substance is negative - not sensitizing.
Executive summary:

The source and target compounds are classified as “Lactones” according to Protein binding by h-CLAT Categories and have the similar protein binding alert responsible for the toxic effect based on the Protein binding by OECD profiler. Moreover, analogues are structurally similar to the target compound in more than 50%. The toxicity prediction was performed based on the experimental data included in the OECD QSAR Toolbox. One chemical would meet the requirements related to their profile and structure as well as the experimental data related to their skin sensitization were available. The prediction is based on sodium L-ascorbate.