3-bromo-1-(3-chloropyrid-2-yl)-5-methyl-1H-pyrazole

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17. February 2020 to 08 June 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Version / remarks:

2019

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EU method B40 bis, “In Vitro Skin Corrosion:Human Skin Model Test”

Version / remarks:

2018

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

3-bromo-1-(3-chloropyrid-2-yl)-5-methyl-1H-pyrazole

Molecular formula:

C9H7BrClN3

IUPAC Name:

3-bromo-1-(3-chloropyrid-2-yl)-5-methyl-1H-pyrazole

Test material form:

solid: particulate/powder

Details on test material:

Batch/Lot Number: 628-044-00
Analysed Concentration: 974.9 ± 3.3 g/kg
Physical State: Beige Solid
Date of Manufacture: 15 October 2019
Date of Expiry: 15 October 2021

Specific details on test material used for the study:

Storage Condition:
Storage Temperature: Room temperature (15 to 30 °C).
Storage Condition: Cool and dry conditions.
Storage Container: In original container as supplied by the Sponsor.
Storage Location: Test Item Control Office, JRF.

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

foreskin from multiple donors

Source strain:

other: human epidermis (RHE/S/17)

Justification for test system used:

This study addresses the human health endpoint skin corrosion. It makes use of reconstructed human epidermis (RhE) (human derived non-transformed epidermal keratinocytes) which closely mimics the histological, morphological, biochemical and physiological properties of the upper parts of the human skin, i.e., the epidermis. The use of reconstructed human epidermis (RHE) is recommended by the OECD and other regulatory authorities. The SkinEthicTM RHE model has been validated and is part of OECD validated reference methods (VRMs) and is a recommended model for conducting in vitro skin corrosion studies. The results of the study are believed to be predictive for the potential of inducing skin corrosivity in humans.

Vehicle:

water

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: SkinEthicTM RHE model.
- Tissue batch number: Lot N° 20-RHE-011.
- Production date: 27 January 2020.

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: at 37 ± 1 °C, in 5±1% CO2 in a 95% humidified atmosphere for 60 minute exposure.
- Positive control tissues: 40 µL/0.5 cm2 of 8N KOH was applied for an exposure period of 60 minutes at 37 ± 1 °C in 5 ± 1% CO2 in a humidified incubator.
- Negative control tissues: 40 µL/0.5 cm2 of sterile distilled water was applied for 3 minutes at room temperature and 60 minutes at 37±1 °C in 5±1% CO2 in a 95% humidified atmosphere.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

TEST MATERIAL
- Amount applied: 20 mg ± 3 mg of test item/0.5 cm2.

VEHICLE
- Concentration: 20 µL sterile distilled water

NEGATIVE CONTROL
- Concentration: 40 µL/0.5 cm2 of sterile distilled water

POSITIVE CONTROL
- Concentration: 40 µL/0.5 cm2 of 8N KOH

Duration of treatment / exposure:

3 minutes at room temperature and 60 minutes at 37 ± 1 °C

Number of replicates:

three replicates/time point

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Mean percent viability (3 minutes exposure)

Value:

97.67

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

no indication of corrosion

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Mean percent viability (60 minutes exposure)

Value:

94.69

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

no indication of corrosion

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: No visible damage.
- Direct-MTT reduction: No interaction.
- Colour interference with MTT: No interaction.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control:
OD values (corrected ODs) of the negative controls in all tissues were between 1.537 and 1.918 i.e., within the test guideline optical density requirement of ≥ 0.8 and ≤ 3.0 (the acceptance criteria for SkinEthicTM RHE model). Results of the negative control met the OECD 431 guideline acceptance range for the prediction model SkinEthicTM RHE.
- Acceptance criteria met for positive control:
The mean percent viability of the positive control was 0.34%, which met OECD 431 acceptance criteria, i.e., <15% viability.
- the observed results were within the acceptance/historical range of SkinEthic Laboratories/OECD TG acceptance criteria.

Any other information on results incl. tables

Pre-Tests

 

Colour Interference Test:

No significant difference in the absorbance was observed between the negative control (distilled water) and the test item. Therefore results of the colour interference test shows that interference was not observed due to test item. The results of the colour interference test are provided in the below-mentioned table:

Treatment	Optical Density (nm)	Interaction
Negative Control (distilled water)	0.041	No
	0.041
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole	0.045	No
	0.044

Direct MTT Reduction Test:

The test item did not produce any direct MTT reduction (in the absence of tissues) when compared with that of the concurrent negative control (distilled water). Results of the direct MTT reduction test are summarised below:

Treatment	Interaction
Negative Control (distilled water)	No
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole	No

Main Study:

The mean percent viability of tissues treated with 3-Bromo-1-(3-Chloro-2-Pyridinyl)-1H-Pyrazole-5-Carboxylic acid, negative control and positive control are summarised below:

Treatment	Viability
	3 Minutes Exposure	60 Minutes Exposure
Negative control (Sterile distilled water)	100%	100%
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole	97.67%	94.69%
Positive control(8N KOH)	-	0.34%

Based on the results of this study, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is classified as non-corrosive, as per the “United Nations Globally Harmonized System of Classification and Labelling of Chemicals”.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

From the results of this study, under the specified experimental conditions, it is concluded that 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is predicted to be non-corrosive to the skin as indicated in OECD 431, using reconstructed human epidermis (RhE) tissues. The substance is not classified as skin corrosive according to EC regulation 1272/2008 (CLP).

Executive summary:

This study was performed to evaluate the corrosive potential of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole, using reconstructed human epidermis (RhE) tissue, in accordance with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS).

Tissues were exposed to 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole or sterile distilled water (negative control) for 3 minutes at room temperature and 60 minutes at 37 ± 1 °C in 5 ± 1% CO₂using three replicates/time point. Positive control tissues were exposed for 60 minutes at 37 ± 1 °C in 5 ± 1% CO₂. Killed tissues were also exposed for 60 minutes at 37 ± 1 °C in 5 ± 1% CO₂.

The mean percent relative viability in tissues treated with the test item was 97.67% after 3-minute exposure and 94.69% after 60-minute exposure. No significant reduction in the percent cell viability was observed after 3-minute and 60-minute exposure in treated tissues when compared with that of the concurrent negative control.

The difference between the viability of the treated tissues was less than 3%, i.e., % CV.

Treatment	Viability
	3 Minutes Exposure	60 Minutes Exposure
Negative control (Sterile distilled water)	100%	100%
to 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole	97.67%	94.69%
Positive control(8N KOH)	-	0.34%

All Optical Density (OD) values (corrected OD) for the negative control replicates were between 1.537 and 1.918, against a guideline requirement of ≥ 0.8 and ≤ 3.0 (the acceptance criteria for SkinEthicTM RHE model).

The positive control showed 0.34% cell viability, against a guideline requirement of <15%, when compared with that of the concurrent negative control, demonstrating the efficiency of the SkinEthicTM RHE model.

All criteria for a valid study were met. From the results of this study, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was concluded to be non-corrosive in the in vitro skin corrosion test, using reconstructed human epidermis (RhE) tissues.

 

The substance is not classified as skin corrosive according to EC regulation 1272/2008 (CLP).