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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2017-07-24 - 2017-09-12
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Cross-reference
Reason / purpose:
reference to other study
Remarks:
WoE
Reference
Endpoint:
skin sensitisation, other
Remarks:
SAR-Profiling of structural alerts for skin sensitisation (OECD QSAR Toolbox)
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Study period:
2017-12-11
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
1. SOFTWARE
OECD QSAR Toolbox

2. MODEL (incl. version number)
version 4.1

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS: 49625-94-7

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
Name of profilers:
1) Protein binding alerts for skin sensitization by OASIS v1.5
2) Protein binding alerts for skin sensitization according to GHS v1.0
3) Protein binding alerts by OASIS v1.5
4) Protein binding alerts by OECD v2.3
5) Protein binding potency Cys (DPRA 13%) v01
6) Protein binding potency Lys (DPRA 13%) v01
7) Protein binding potency v2.4
8) Protein binding potency h-CLAT v1.0
9) Keratinocyte gene expression v2.0

5. APPLICABILITY DOMAIN
The aim of these profilers is to investigate the presence of alerts within the target molecules responsible for interaction or covalent bindings with proteins. For detailed information, please refer to the attached reports about the specific profilers.

6. ADEQUACY OF THE RESULT
These profiling results are used in a weight-of-evidence approach to assess the skin sensitising potential of the test item. The selected profilers detect structural alerts, which are associated with the potential to bind to or interact with proteins and to induce keratinocyte gene expression. The binding to skin proteins is the first step of the Adverse Outcome Pathway for skin sensitisation. Binding to skin proteins is essential to induce a specific memory T-cell response associated with skin sensitisation.
Reason / purpose:
reference to other study
Remarks:
WoE
Guideline:
other: REACH Guidance on QSARs R.6
Version / remarks:
Profiling was performed with the QSAR Toolbox Version 4.1
Key result
Parameter:
other:
Remarks on result:
no indication of skin sensitisation
Remarks:
No protein binding potency alert was identified in the substance and in none of the simulated metabolites. The 'keratinocyte gene expression' was not possible to classify by the respective profiler.
Parameter:
other:
Remarks on result:
no indication of skin sensitisation based on QSAR/QSPR prediction
Remarks:
No protein binding potency alert was identified in the substance and in none of the simulated metabolites. The 'keratinocyte gene expression' was not possible to classify by the respective profiler.
Conclusions:
ZPS and its metabolites have been profiled with the OECD QSAR Toolbox, version 4.1. No indication for skin sensitisation of the query substance and its skin metabolites was identified by eight different profilers on protein binding potency. This provides evidence that ZPS is negative in DPRA.
Executive summary:

ZPS and its metabolites have been profiled with the OECD QSAR Toolbox, version 4.1. No indication for skin sensitisation of the query substance and its skin metabolites was identified by eight different profilers on protein binding potency. This provides evidence that ZPS is negative in DPRA.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
other: OECD 442E
Version / remarks:
OECD Guideline for the Testing of Chemicals, Part 442E: In Vitro Skin Sensitisation: human Cell Line Activation Test (h-CLAT) (adopted 29. July 2016)
Deviations:
yes
Remarks:
See "Deviations from the Guideline", Overall remarks, but not affecting the validity of the study or results
Qualifier:
according to
Guideline:
other: OECD. (2012). The Adverse Outcome Pathway for Skin Sensitisation Initiated by Covalent Binding, Part 1: Scientific Evidence. Series on Testing and Assessment No. 168, Paris
Deviations:
no
Qualifier:
according to
Guideline:
other: Bauch, C., Kolle, S. N., & Ramirez, T. (2012). Putting the parts together: combining in vitro methods to test for skin sensitizing potentials. Regulation of Toxicology and Pharmacology, 63, 489–504
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of study:
activation of dendritic cells
Justification for non-LLNA method:
In vitro study should be performed first. An in vivo study shall be conducted only if in vitro/in chemico test methods described under point 8.3.1 of REACH are not applicable.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: sponsor

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: The test item was stored in the test facility at room temperature (20 ± 5°C) protected from light and humidity.

OTHER SPECIFICS:
Molecular weight 311.38 g/mol
Log Kow ≤ - 1.7 at 21.1 °C

In vitro test system

Details on study design:
This in vitro study was performed to assess the sensitising potential of the test item 3-(2-Benzothiazolylthio)-propanesulfonic acid, sodium salt (ZPS) by quantifying changes in the expression level of the two cell surface markers CD86 and CD54, which are associated with the process of activation of monocytes and dendritic cells. For this purpose the human monocytic leukaemia cell line THP-1 was used and treated with the test item for 24 h before evaluation. The measured expression levels were used to distinguish potential skin sensitizers from non-sensitizers.
The h-CLAT addresses the third key event of the skin sensitisation adverse outcome pathway (AOP) that was defined by the OECD in 2012 and is a part of the AOP-based “two out of three” skin sensitisation integrated testing strategy for hazard identification (Bauch et al., 2012).
In order to conclude on the skin sensitisation potential of the test substance, a human Cell Line Activation Test (h-CLAT) comprises a minimum of two independent and valid experiments. A categorization in the subcategories 1 A and 1 B is not possible. However, a positive result with the h-CLAT may be used on its own to classify a chemical into UN GHS category 1. For a confirmation of a negative result another in vitro skin sensitisation test has to be performed.

For further details, see "any other information on materials and methods".

Results and discussion

Positive control results:
positive, see tables below

In vitro / in chemico

Resultsopen allclose all
Key result
Parameter:
other: EC200 (for CD54)
Remarks:
µg/ml
Run / experiment:
Experiment III
Value:
884.59
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: EC150 (for CD86)
Remarks:
µg/ml
Run / experiment:
Experiment III
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
not determinable
Remarks:
A calculation of the EC150 (for CD86) was not possible since none of the RFI values was above 150.
Key result
Parameter:
other: EC200 (for CD54)
Remarks:
µg/mL
Run / experiment:
Experiment IV
Value:
833.3
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: EC150 (for CD86)
Remarks:
µg/ml
Run / experiment:
Experiment IV
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
not determinable
Remarks:
A calculation of the EC150 (for CD86) was not possible since none of the RFI values was above 150.
Other effects / acceptance of results:
DEMONSTRATION OF TECHNICAL PROFICIENCY: Yes

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes
- Range of historical values if different from the ones specified in the test guideline: no

Applicant's summary and conclusion

Interpretation of results:
other: potential skin sensitizer
Conclusions:
The study was performed according to OECD TG 442E under GLP on the registered substance itself. Positive and negative control were valid.
The h-CLAT addresses the third key event of the skin sensitisation adverse outcome pathway (AOP) that was defined by the OECD in 2012 and is a part of the AOP-based “two out of three” skin sensitisation integrated testing strategy for hazard identification (Bauch et al., 2012). The sensitising potential of the test item was assessed by quantifying changes in the expression level of the two cell surface markers CD86 and CD54, which are associated with the process of activation of monocytes and dendritic cells, after incubation with the test item. The measured expression levels were used to distinguish potential skin sensitizers from non-sensitizers.
In experiment III and IV the RFI of CD86 was not ≥ 150 % at any tested concentration with cell viability ≥ 50 %.
In experiment III the RFI of CD54 was > 200 % at the highest test item concentration (1000 µg/mL). At the next lower test item concentration (833.3 µg/mL) the RFI was only slightly below the threshold: 192. In experiment IV the RFI of CD54 was slightly below 200 at the highest test item concentration (196) but 200 at the next lower test item concentration (833.3 µg/mL) Therefore, the result in both experiments is “positive”.
In conclusion, it can be stated that under the experimental conditions of this study, the test item, 3-(2-Benzothiazolylthio)-propanesulfonic acid, sodium salt (ZPS), was positive in the h-CLAT and is therefore considered to have the potential to activate dendritic cells and is a potential skin sensitizer.
A categorization in the subcategories 1 A and 1 B is not possible. However, a positive result with the h-CLAT may be used on its own to classify a chemical into UN GHS category 1.
According to OECD Toolbox profiling, no protein binding potency alert was identified in the substance and in none of the simulated metabolites. The 'keratinocyte gene expression' was not possible to classify by the respective profiler.
Taking into account the magnitude of the results, the substance is not considered to be a strong sensitizer. On the contrary, the substance should be maximally regarded as weak sensitizer. The positive control DNBC resulted with 4 µg/ml (historical control data) in mean RFI values of 875 (CD86) resp. 370 (CD54). According to the guideline 442E, Appendix 2, proficiency substances, the reference ranges are EC150 = 0.5 – 10 µg/ml (CD86) and EC200 = 0.5 – 15 µg/ml (CD54), resulting both in positive results, which matches. The reference ranges as cited in the guideline for the weak solid sensitizer Imidazolidinyl urea are EC150 = 20 – 90 µg/ml (CD86) and EC200 = 20 – 75 µg/ml (CD54), resulting in a positive result, both values for the solid non-sensitizer 4-Aminobenzoic acid are >1000 µg/ml and revealed negative results.
In consequence, the obtained RFI values, although meeting the criteria for classification as positive, are way more in the range of the ones of the non-sensitizer than the ones of the weak sensitizer. In combination with the fact that no protein binding potency alert was identified, it cannot be excluded that the test item is not skin sensitizer at all in vivo. However, the substance is predicted to be skin sensitising by the QSAR tools CASE Ultra and Leadscope, which are implemented in the 'Danish QSAR database'. Taking further into account the fact that ZPS might be as well positive in the DPRA, the substance should be classified precautionarily as skin sens. Cat. 1, considering the AOP-based “two out of three” skin sensitisation integrated testing strategy.
Executive summary:

This in vitro study was performed according to OECD 442E under GLP to assess the sensitising potential of the test item 3-(2-Benzothiazolylthio)-propanesulfonic acid, sodium salt (ZPS) by quantifying changes in the expression level of the two cell surface markers CD86 and CD54, which are associated with the process of activation of monocytes and dendritic cells.

In total one pre-test and four experiments (experiment I - IV) with a treatment period of 24 hours were performed whereby experiment I and II were invalid and had to be repeated. Therefore, in total two valid experiments (experiment III and IV) were performed. The results and data of the invalid experiments are not included in this final report but will be archived with the raw data.

For the experiments, the highest nominal applied concentration (1000 µg/mL) was chosen based on the results obtained in the pre-test and the solubility of the test item. A geometric series (factor 1.2) of 7 dilutions thereof was prepared.

As solvent control for the test item, RPMI 1640 was used in a final concentration of 1 % in culture medium.

As positive control, 2,4-dinitrochlorobenzene (DNCB, CAS n. 97-00-7, ≥ 99% purity) was used.

In experiment III and IV the RFI of CD86 was not ≥ 150 % at any tested concentration with cell viability ≥ 50 %.

In experiment III and IV the RFI of CD54 was > 200 % at one non-cytotoxic test item concentration, respectively in both experiments.

The result of both experiments is “positive”.

Under the experimental conditions of this study, the test item, 3-(2-Benzothiazolylthio)-propanesulfonic acid, sodium salt (ZPS), was positive in the h-CLAT and is therefore considered to have the potential to activate dendritic cells and therefore to be a potential skin sensitizer.