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Description of key information

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Version / remarks:
Reconstructed Human Epidermis Test Method of 2013
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: L’Oreal. In Vitro Skin Irritation Test: Human Epidermis Model EPISKIN, EPISKIN Skin Irritation Test 15min - 42 hours, Standard Operating Procedure: February 2009 Version 1.8.
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Vehicle:
unchanged (no vehicle)
Amount / concentration applied:
Types of Treatment in the Main Test
- Negative control: Dulbecco's Phosphate Buffered Saline (DPBS), dose volume 10 µl/tissue sample
- Test Substance: WS405777, dose 10 mg/tissue sample after wetting with 5 µl purified water
- Positive control: 5% Sodium Dodecyl Sulphate (SDS) in purified water, dose volume 10 µl/tissue sample
Duration of treatment / exposure:
15 ± 0.5 minutes with the test substance, negative or positive control at room temperature, followed by thorough rinsing of each epidermis unit with Dulbecco's phosphate buffered saline
Details on study design:
Test System
EPISKIN human epidermis skin constructs consisting of normal, human-derived epidermal keratinocytes and forming a multilayered, highly differentiated model of the human epidermis with a functional multilayered stratum corneum (matrix: collagen type 1 coated with type IV collagen).

Principle of the Test – Main Test
Irritant substances are sufficiently cytotoxic to cause cell deaths in the cell layers. Therefore, cell viability of the multilayers was determined by measurement of mitochondrial dehydrogenase activity assessed by reduction of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) to a soluble, coloured, formazan salt. The degree of formazan salt formation (positively correlated with the degree of cell viability) was measured photometrically (i.e. determination of the optical density of formazan extracts from tissue at 540 nm).

Depending on the percentage of tissue viability attained (compared to negative control viability) a test substance is classified as skin irritating or not skin irritating.

Pre-Tests – Checking for Interference of the Test Substance with the Assay
It was demonstrated, that the test material WS405777 itself did not interact with MTT. Also the test substance WS405777 did not show any potential for colouring water.

Main Test
Each treatment group (test substance, negative/positive controls) comprised 3 live (viable) tissue samples placed into wells of 12 well plates.

Incubation of these tissues before treatment in maintenance medium: ≥ 24 h at 37°C, 5% CO2 in air, in humidified atmosphere , in wells
each containing 2 mL fresh pre-warmed maintenance medium.
Test material administration: Spreading of thin even layer over the epidermal surface.
Termination of 15 ± 0.5 minute exposure period: Removal of residual test material or positive control substance by thorough
rinsing of each epidermis unit with Dulbecco's PBS;
removal of remaining PBS by blotting on absorbent paper.
Posttreatment incubation (all tissue samples) : 42 ± 1 h at 37°C , 5% CO2 in humidified atmosphere, in wells each containing
2 mL fresh pre-warmed maintenance medium
Then MTT incubation: 3 hours (± 5 minutes) at 37°C , 5% CO2 in humidified atmosphere, in wells each containing 2 mL of 0.3 mg/mL MTT.
Formazan extraction (all tissue samples) : Further processing of tissue samples & formazan extraction by vortexing in
acidic isopropanol, 500 µL/sample. The vortexed samples were stored at 2-8°C
protected from light for 48 - 70 hours.
Qantitative determination of optical density: At 540 nm with acidified isopropanol (0.04 N HCl final concentration,
6 x 200 µL) as blanks.
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
replicate a
Value:
107.2
Negative controls validity:
valid
Positive controls validity:
valid
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
replicate b
Value:
95.7
Negative controls validity:
valid
Positive controls validity:
valid
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
replicate c
Value:
93.9
Negative controls validity:
valid
Positive controls validity:
valid

 

 

Interpretation of results:
other: not irritating
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 437 of July 2013: Bovine Corneal Opacity and Permeability test method for identifying i) chemicals inducing serious eye damage and ii) chemicals not requiring classification for eye irritation or serious eye damage.
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Species:
other: in vitro test
Strain:
other: bovine eyes
Vehicle:
physiological saline
Amount / concentration applied:
750 µl of test substance, 20% in physiol. saline, positive control solution (20% w/w imidazole in physiol. saline) or negative control solution (physiol. saline) was introduced into the anterior part of each cornea holder. Following application, turning of the holder into horizontal position and its slight rotation ensured uniform distribution of the test substance over the surface of the cornea.
Duration of treatment / exposure:
4 hours (± 5 min.).
Each cornea holder was incubated in a horizontal position at 32°C ± 1°C in a waterbath. Following incubation, the test substance, positive and negative controls were removed and the epithelial surface of the cornea washed, at least three times or until the wash medium (EMEM* with phenol red) was clear and there was no discolouration.

* EMEM, Eagles Minimal Essential Medium
Details on study design:
Each treatment group (test substance, negative/positive controls) comprised 3 corneas from bovine eyes. Each cornea surrounded by ca. 2 to 3 mm of sclera was mounted to a holder. Eyes were maintained and transported to the laboratory and isolated corneas stored in sufficient HBSS* containing 1% penicilin/streptomycin solution until being used. The eyes were used within 4 hours of slaughter. Adequate exposure of the epithelial surface of the cornea to the test substance was provided. Opacity of the cornea was determined by measurement of light transmission through the centre of each mounted cornea using a calibrated opacitometer. Permeability of the cornea was determined by spectophotometric measurement at 490 nm (OD490) of medium from the posterior compartment of the cornea holder after addition of 1 ml of sodium fluorescein solution (4 mg/ml) to the anterior compartment, thus determining the degree of penetration of sodium fluorescein through all corneal cell layers. Prior to the spectophotometric measurement, incubation with fluorescein solution had happened in horizontal position of the cornea holder at 32°C ± 1°C for 90 ± 5 minutes in a waterbath. Then the medium in the posterior compartment was mixed by drawing approximately 2.5 ml gently up and down a 5 ml syringe, with a needle attached, three times. Any solution giving an OD490 value above 1.8 was diluted 1 in 5 with cMEM.

Effects to the cornea (corresponding to possible eye damage) were measured as opacity and permeability, which when combined gave an In Vitro Irritancy Score (IVIS) for each treatment group. A substance that induces an IVIS greater than 55 is defined as a corrosive or severe irritant.

*HBSS Hanks Balanced Salt Solution containing Ca++ and Mg++ without phenol red
Irritation parameter:
cornea opacity score
Run / experiment:
replicate 1
Value:
0.333
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
cornea opacity score
Run / experiment:
replicate 2
Value:
1.333
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
cornea opacity score
Run / experiment:
replicate 3
Value:
1.333
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
in vitro irritation score
Run / experiment:
replicate 1
Value:
0.483
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
in vitro irritation score
Run / experiment:
replicate 2
Value:
1.063
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
in vitro irritation score
Run / experiment:
replicate 3
Value:
1.078
Negative controls validity:
valid
Positive controls validity:
valid
Interpretation of results:
other: not irritating
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Justification for classification or non-classification

In the in vitro skin and eye irritation studies no effects were observed in the presence of the test substance. Therefore, classification of WS405966 for skin or eye irritation is not required [REGULATION (EC) 1272/2008].