Registration Dossier

Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2018-02-06 - 2018-03-09 (experimental phase)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 442D (In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method)
Version / remarks:
OECD Guidelines for Testing of Chemicals Method 442D (In Vitro Skin Sensitization: ARE-Nrf2 Luciferase Test Method; adopted February 2015)
Deviations:
no
GLP compliance:
yes
Type of study:
activation of keratinocytes
Justification for non-LLNA method:
The study was conducted to investigate the potential of the test item to induce genes that are regulated by the antioxidant response element (ARE). The data may be used as part of an integrated approach to testing and assessment (IATA) to support the discrimination between skin sensitisers and non-sensitisers for the purpose of hazard classification and labelling.
In vitro methods have to be considered under REACH prior to conducting in vivo methods.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
white powder
Details on test material:
Storage Conditions : 15 to 30°C, protected from light

In vitro test system

Details on study design:
TEST SYSTEM
Specifications:
KeratinoSens™ cell line supplied by Givaudan Schweiz, Zurich, Switzerland as specified in OECD Test Guideline 442D (batch number 55, passage 11 for Experiment 1, batch number 57, passage 12 for Experiment 2 and batch number 59, passage 11 for Experiment 3).
Identification:
The test system was appropriately labelled with the study number, assay type, experiment number and test/positive/negative/untreated control.
Preparation of Cultures:
A fresh vial of cells was used for each experimental occasion and cultured using Dulbecco’s modified Eagle medium (DMEM) containing 9% foetal bovine serum and 1% Geneticin.

Results and discussion

Positive control results:
valid; see tables below

In vitro / in chemico

Resultsopen allclose all
Parameter:
other: overall maximal fold increase (Imax)
Run / experiment:
1
Value:
3.24
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: overall maximal fold increase (Imax)
Run / experiment:
2
Value:
2.42
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: overall maximal fold increase (Imax)
Run / experiment:
3
Value:
1.22
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: overall maximal fold increase (Imax)
Run / experiment:
mean
Value:
> 1.5
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: EC1.5 value, µM
Run / experiment:
1
Value:
412.26
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: EC1.5 value, µM
Run / experiment:
2
Value:
311.58
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: EC1.5 value, µM
Run / experiment:
mean
Value:
< 1 000
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: cell viability, %
Run / experiment:
mean
Value:
> 70
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: IC50 value, µM
Run / experiment:
1
Value:
1 445.82
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: IC50 value, µM
Run / experiment:
2
Value:
668.23
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Parameter:
other: IC50 value, µM
Run / experiment:
3
Value:
1 966.93
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Key result
Parameter:
other: dose-response
Run / experiment:
all experiments
Remarks on result:
other: dose-response was given
Other effects / acceptance of results:
OTHER EFFECTS:
- Visible damage on test system: none stated

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

Applicant's summary and conclusion

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
The study was performed according to OECD TG 442D under GLP on the registered substance itself. Positive and negative control were valid. The study was conducted to investigate the potential of (S)-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)benzenecarbothioate to induce genes that are regulated by the antioxidant response element (ARE). The data may be used as part of an integrated approach to testing and assessment (IATA) to support the discrimination between skin sensitisers and non-sensitisers for the purpose of hazard classification and labelling. In case of a positive response however, it may serve as standalone test. All four conditions for a positive prediction (Imax > 1.5-fold, cell viability > 70%, EC1.5 value < 1000 µM, dose response) were met in Experiment 1, however only three of the conditions were met in Experiment 2. Cell viability in Experiment 2 at the lowest concentration with induction of luciferase activity above 1.5-fold did not exceed 70% as specified in the protocol. However, all other results indicate that the test article is predicted as positive in this assay.
The test article, (S)-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)benzenecarbothioate, was thus considered to be positive in the ARE-Nrf2 Luciferase Test.
Executive summary:

The study was conducted according to OECD 442D under GLP to investigate the potential of(S)-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)benzenecarbothioateto induce genes that are regulated by the antioxidant response element (ARE). The data may be used as part of an integrated approach to testing and assessment (IATA) to support the discrimination between skin sensitisers and non-sensitisers for the purpose of hazard classification and labelling.

The test article was dissolved in dimethylformamide (DMF) to the final stock concentration (200 mM). Serial dilutions were then made using DMF to obtain 12 master concentrations of the test article (0.098, 0.196, 0.391, 0.781, 1.563, 3.125, 6.25, 12.5, 25, 50, 100 and 200 mM).

The master concentrations were then further diluted 25-fold into culture medium containing serum and finally used for treatment with a further 4-fold dilution factor so that the final concentrations ranged from 0.98 to 2000 µM.

Aliquots of 50 µL of each of the final concentrations were transferred to each of three luciferase plates and a single viability plate. Each plate was sealed using a plate sealer and then incubated at 37±1C, 5% (v/v) CO2 in air, in a humidified environment for 48±1 hours.

After the 48-hour exposure period, the medium in the viability plate was replaced with fresh medium containing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT).The plate was sealed and incubated for 4 hours at 37±1°C, 5% (v/v) CO2. The MTT medium was then removed and SDS (at 10% w/v) added per well. The plate was sealed and placed into an incubator at 37±1°C, 5% (v/v) CO2 in air and left overnight. After the overnight incubation, the plate was shaken to ensure homogeneity of the solution in the wells and then absorption read at 600 nm using a SpectraMax M2e.

After the 48-hour exposure period, the cells in the luciferase plates were washed with phosphate buffered saline and lysis buffer for luminescence readings was added to each well. The plates were then incubated for 20 minutes at 25±2°C, loaded into the luminescence plate reader and read.

 

The results are summarised as follows:

Criteria

Experiment 1

Experiment 2

Experiment 3

Imax

3.24

2.42

1.22

Cell Viability

84.92%

59.45%

Not calculated

EC1.5

412.26

311.58

Not calculated

Dose Response

Yes

Yes

 

 

All assay acceptance criteria were met, with the exception that the average induction for the positive control at 64 μM in Experiment 1 was 13.40. The assay was considered valid as there was a clear dose response with the positive control.

The Imax in Experiment 3 was less than 1.5 therefore this experiment gave a negative prediction.

All four conditions for a positive prediction (Imax > 1.5-fold, cell viability > 70%, EC1.5 value < 1000 µM, dose response) were met in Experiment 1, however, only three of the conditions were met in Experiment 2. Cell viability in Experiment 2 at the lowest concentration with induction of luciferase activity above 1.5-fold did not exceed 70% as specified in the protocol. However, all other results indicate that the test article is predicted as positive in this assay.

The test article,(S)-(4,5-dihydro-5-thioxo-1,3,4-thiadiazol-2-yl)benzenecarbothioate, was thus considered to be positive in the ARE-Nrf2 Luciferase Test.