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

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 January 2020 to 20 May 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

Qualifier:

according to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

2019

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 (at JRF):
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.

Test animals / tissue source

Species:

human

Strain:

other: Reconstructed human cornea epithelium (RhCE)

Details on test animals or tissues and environmental conditions:

Test System: Reconstructed human cornea epithelium (RhCE).
Model: SkinEthicTM HCE.
Source: EPISKIN– 4 Rue Alexander Fleming, 69366 Lyon Cedex 07 – France.
Lot No.: 20-HCE-012.

Test system

Vehicle:

other: Dubelcco’s Phosphate Buffer Saline (DPBS)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amounts applied: 30 μL DPBS + 30 mg 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole.

NEGATIVE CONTROL:
Name: Dubelcco’s Phosphate Buffer Saline (DPBS).
- Amounts applied: 30 μL DPBS.
Batch Nº: 1918956.
Expiry Date: September 30, 2020.
Manufactured by: Gibco.

POSITIVE CONTROL:
Reference Substance Name: Methyl acetate.
- Amounts applied: 10 μL DPBS + 30 μL methyl acetate (undiluted).
CAS No: 79-20-9.
Analysed Purity: 99.5% .
Batch No: STBG5814V.
Supplied by: Sigma.
Manufactured by: Sigma.
Date of Receipt: May 08, 2017.
Date of Expiry : May 07, 2022.
Physical Appearance: Colourless liquid.
Storage Condition (at JRF): Room temperature.

Duration of treatment / exposure:

Tissues were exposed to test item, negative and positive control for 4 h.

Duration of post- treatment incubation (in vitro):

For post incubation, the MTT test was performed. Tissues were placed in MTT (1.0 mg/mL) solution and incubated for 180 minutes at 37 ± 2°C in 5 ± 1% CO2 and saturated with humidity.

Number of animals or in vitro replicates:

Two replicates in each group (test item, positive control, negative control).

Details on study design:

NEGATIVE CONTROL USED: Yes.
- Name: Dubelcco’s Phosphate Buffer Saline.
- Batch Nº: 1918956.

POSITIVE CONTROL USED: Yes.
- Reference Substance Name: Methyl acetate.
- Analysed Purity: 99.5%.
- Batch No: STBG5814V.

NUMBER OF REPLICATES , APPLICATION DOSE AND EXPOSURE TIME
- Test material: 30 mg 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole + 30 μL DPBS.
- Positive control: 10 μL DPBS + 30 μL methyl acetate (undiluted).
- Negative control: 30 μL DPBS.
- two replicates in each group (test item, positive/negative control).

Results and discussion

In vitro

Results

Irritation parameter:

other: optical density

Run / experiment:

Mean Percent Viability

Value:

32.33

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

not determinable

Remarks:

According OECD 492 "No prediction can be made".

Other effects / acceptance of results:

Validity of the Test:
- Negative control OD values were found to be within the range of > 1.0 to ≤ 2.5.
- Mean tissue viability values for positive control was found < 20%.
- Variation within the replicates was acceptable (< 20%).
Therefore, the experiment is considered valid.

Any other information on results incl. tables

Pre-Tests

Direct MTT Reduction Test

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

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

Colour Interference Test

Any difference in the absorbance, due to colour interference, was not observed visibly for the test item. Results of direct MTT reduction test are summarised in the table mentioned below:

Treatment	Interaction
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1HPyrazole	No

Negative Control

The individual optical density, corrected optical density, mean of corrected optical density, viability, and mean percent viability, are summarised in the following table.

The OD values (corrected mean ODs) of the negative control was 1.678 and 1.751. Therefore, results of the negative control met the acceptance range of the OECD test guideline 492 for the prediction model SkinEthicTM HCE. Test guideline requirement of optical density is > 1.0 and ≤ 2.5 (the acceptance criteria for SkinEthicTM HCE model, as per the OECD TG 492). Variation between the two negative controls tissues was < 20%, which met the acceptance range of the OECD test guideline 492 for the prediction model SkinEthicTM HCE. As per the certificate of analysis for the batch of tissues used in the study (Batch# 20-HCE-012), average optical density observed was 2.0 in QC testing at SkinEthic Laboratories. Therefore, the observed results were within the acceptable range of the SkinEthic Laboratories/OECD TG acceptance criteria.

Positive Control

The individual optical density, corrected optical density, mean of corrected optical density, viability, and mean percent viability, are summarised in the following table.

The mean % viability of the positive control was 18.51%, which met the acceptance criteria of the OECD test guideline 492, i.e., <20% viability.

 

Main Study

The individual optical density, corrected optical density, mean of corrected optical density, viability and mean per cent viability for test item are summarised in the following table.

The mean per cent viability of the 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole treated tissues, and the control tissues, is tabulated below:

Treatment	Mean Percent Viability
Negative control (DPBS)	100.00
Positive control (methyl acetate)	18.51
3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole	32.33

The mean per cent cell viability in tissues treated with 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole was found to be 32.33% in the concurrent negative control (100%) which is below the established tissue viability cut-off value of 50%.

 

Therefore, based on these results, 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole is according OECD 492 assessed as “No prediction can be made”.

 

Applicant's summary and conclusion

Interpretation of results:

Category 1 (irreversible effects on the eye) based on GHS criteria

Conclusions:

Based on the mean viability score of 32.33%, determined under the specified experimental conditions using SkinEthicTM HCE RhCE, the classification for 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1Hpyrazole is “No prediction can be made” (UN GHS) and that further testing may be required in order to classify and/or determine if the test item is an ocular irritant. In accordance with the provisions of regulation 1272/2008 a prediction of classification can not be made.

Executive summary:

Study type: Reconstructed Human Cornea-like Epithelium (RhCE) Test, OECD 492.

Study title: In Vitro Eye Irritation Test of 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole Using Reconstructed Human Cornea-Like Epithelium.

This study was performed to evaluate the ocular irritation potential of 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole, as measured by the potential to induce cytotoxicity in a reconstructed human cornea-like epithelium (RhCE) tissue construct which closely mimics the properties of the human corneal epithelium. The RhCE test can identify test items not requiring classification, according to the UN GHS (No category).

RhCE tissues (two tissues per set) were treated with 30 μL of either Dulbecco’s Phosphate Buffered Saline (DPBS) (Set 1 - control), 30 μL of undiluted methyl acetate (Set 2 - positive control), and 30 μL of Dulbecco’s Phosphate Buffered Saline (DPBS) along with 30 mg 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole (Set 3 – test group). The tissues were incubated for 4 h ± 6 minutes. At the end of the exposure period, residue was removed, and the tissue were kept for 30 minutes in the maintenance medium at room temperature, followed by an incubation period of 18 h ± 30 minutes.

Tissue viability was measured, following the treatment and a post-treatment incubation period, by enzymatic conversion of the vital dye MTT into a blue MTT formazan salt, measured after extraction from tissues. The optical density (OD) of the extracted formazan was determined using a microplate reader at 570 nm. The viability of the RhCE tissue was determined in comparison to tissues treated with the negative control substance (% viability) and was then used to predict the ocular hazard potential of the test chemical.

The mean per cent cell viability in tissues is shown below. The mean per cent cell viability in tissues treated with 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole was found to be 32.33% of the concurrent negative control (100%) which is below the established tissue viability cut-off value of 50%.

Treatment	Mean Percent Viability
Negative control (Dulbecco’s Phosphate Buffered Saline)	100.00
Positive control (methyl acetate)	18.51
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole	32.33

The negative and positive controls met the acceptance criteria, as described in the study plan, and confirmed the reliability of the test procedure.

Based on the mean viability score of 32.33%, determined under the specified experimental conditions using reconstructed human cornea-like epithelium (RhCE) from EPISKIN, the classification for 3-bromo-1-(3-chloro-2-pyridyl)-5-methyl-1H-pyrazole is “No prediction can be made” (UN GHS) and that further testing may be required in order to classify the test item.