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EC number: 952-948-8 | CAS number: -
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Administrative data
Description of key information
1. Skin sensitisation according to OECD 442D and according to EC Method B60:
In the KeratinoSens assay “In Vitro Skin Sensitisation: Keratinocyte-Based ARE-Nrf2 Luciferase Reporter Gene Test 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole Using KeratinoSensTM (HaCat) Cell line” 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole met all the evaluation criteria to be concluded as a sensitiser. Negative and positive controls met the acceptance criteria for the controls and were correctly identified as non-sensitiser and sensitiser, respectively. All criteria for a valid study were met.
2. Skin sensitisation according to OECD 442C:
From the results of the study “In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA) of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole using Synthetic Heptapeptides”, under the specified experimental conditions 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was identified as a non-sensitiser in the DPRA assay.
3. Skin sensitisation according to OECD 442E:
From the results of the study “In Vitro Skin Sensitisation: "Human Cell Line Activation Test (h-CLAT) of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole”, under the specified experimental conditions 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was identified as a sensitiser in the h-CLAT assay.
From the results of these studies under the specified experimental conditions 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is predicted to be a sensitiser to skin.
Key value for chemical safety assessment
Skin sensitisation
Link to relevant study records
- Endpoint:
- skin sensitisation: in chemico
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 10 December 2019 to 08 June 2020
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
- Version / remarks:
- 2019
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of study:
- direct peptide reactivity assay (DPRA)
- Justification for non-LLNA method:
- This assay assesses the covalent binding potential of the test item to proteins. The DPRA is proposed to address the molecular initiating event of the skin sensitisation AOP, namely protein reactivity, by quantifying the reactivity of test chemicals towards model synthetic peptides containing either Cysteine or Lysine. Cysteine and Lysine percent peptide depletion values are then used to categorise a substance in one of four classes of reactivity for supporting the discrimination between skin sensitisers and non-sensitisers.
- Specific details on test material used for the study:
- Storage Conditions:
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. - Details on the study design:
- - Synthetic heptapeptides containing either Lysine (Ac-RFAAKAA-COOH) or Cysteine (Ac-RFAACAA-COOH) are used as the test system for the direct peptide reactivity assay.
- Synthetic heptapeptides used in this study were obtained from RS Synthesis, Louisville, KY 40270, USA. - Batch number of Cysteine and Lysine peptide was P181203-LC180433 and P170906-LC107617, respectively, used in the study.
INSTRUMENTS AND EQUIPMENT
Micropipettes: Brand, Eppendorf AG.
Refrigerator: LG Electronics Inc.
Digital Balance: Ohaus (Capable of measuring 10 mg to 210 g).
Microbalance: Rodwag (Capable of measuring 1 mg to 5 g).
pH meter: Thermo Scientific.
Cyclomixer: Remi Electrotechnik.
Millipore Water.
System :Millipore.
High Performance Liquid.
Chromatography (HPLC): Shimadzu.
Ultralow Temperature Freezer: SANYO.
SOLVENTS AND CHEMICALS
Acetonitrile: Finar (HPLC #292761121FS).
Trifluoro acetic acid: SDFCL (HPLC #F17A/0517/0905/53).
Sodium phosphate, monobasic dihydrate: Merk (# DL6D663605).
Sodium phosphate, dibasic heptahydrate: Sigma (BioReagent #SLBL6644V).
Ammonium acetate: SDFCL (HPLC #2400161214).
Ammonium hydroxide: Sigma-VETEC (AR #MMBB4397V).
SOLVENT CONTROL: Yes.
Acetonitrile
CAS Number: 75-05-8
Molecular Weight: 41.05 g/mol
Manufactured by: Finar
Lot N°: 292761121FS
Date of receipt: September 24, 2019
Date of Expiry: May 2024
Appearance: Colourless Liquid
Purity: 99.1%
Storage : Room Temperature
POSITIVE CONTROL USED: Yes.
Cinnamaldehyde was used as positive control (PC) at a concentration of 100 mM in acetonitrile.
Name: Cinnamaldehyde
CAS Number: 104-55-2
Density: 1.049 g/mL
Manufactured by: Sigma-Aldrich
Lot N°: MKBT8955V
Date of receipt: February 12, 2016
Date of Expiry: February 2020
Appearance: Yellow Liquid
Purity: 99.1%
Storage: Room Temperature
Note: 38.10 µL of cinnamaldehyde was dissolved in 2961.90 µL of acetonitrile for the preparation of 100 mM solution (3 mL) for both Cysteine and Lysine peptides.
VEHICLE
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was found to be soluble in acetonitrile. Precipitation was not observed in acetonitrile. Hence, acetonitrile was selected as the vehicle for the study. - Positive control results:
- Cinnamaldehyde was used as positive control in each assay with Cysteine and Lysine peptides. Value of the mean percent peptide depletion value of the positive control, viz., cinnamaldehyde was 76% for Cysteine peptide and 64% for Lysine peptide (TABLE 5). The relative Coefficient of Variability (RCV) for the positive control replicate was 6.18% for percent Cysteine depletion and 1.94% for percent Lysine depletion.
- Key result
- Run / experiment:
- other: Actual % Depletion (Cysteine)
- Parameter:
- other: DPRA Prediction
- Value:
- 2
- Positive controls validity:
- valid
- Remarks on result:
- no indication of skin sensitisation
- Remarks:
- DPRA Prediction: Non-Sensitizer (Negative).
- Key result
- Run / experiment:
- other: Actual % Depletion (Lysine)
- Parameter:
- other: DPRA Prediction
- Value:
- 1
- Positive controls validity:
- valid
- Remarks on result:
- no indication of skin sensitisation
- Remarks:
- DPRA Prediction: Non-Sensitizer (Negative).
- Key result
- Run / experiment:
- other: % Mean Depletion (Cysteine and Lysine)
- Parameter:
- other: DPRA Prediction
- Value:
- 1.2
- Positive controls validity:
- valid
- Remarks on result:
- no indication of skin sensitisation
- Remarks:
- DPRA Prediction: Non-Sensitizer (Negative).
- Other effects / acceptance of results:
- - Acceptance criteria met for positive control:: Yes.
- Interpretation of results:
- GHS criteria not met
- Conclusions:
- From the results of this study, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was predicted to be a Non-Skin Sensitiser in the DPRA assay.
- Executive summary:
This study was conducted to evaluate the skin sensitisation potential of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole, using the synthetic heptapeptides. The method followed was as per OECD Test Guideline No. 442C.
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was found to be soluble in acetonitrile at 100 mM.
Therefore, acetonitrile was selected as the vehicle for this study.
Synthetic heptapeptides containing either Lysine (Ac-RFAAKAA-COOH) or Cysteine (Ac-RFAACAACOOH), were used as the test system in this assay. Cysteine and lysine containing peptides were incubated with a positive control and the test item for ≈27 hours at 22.5-30 ºC (in the dark), separately. Relative peptide concentration was measured by the high-performance liquid chromatography (HPLC) with gradient elution and UV detection at 220 nm. Cysteine and lysine peptide percent depletion values were calculated and used in a prediction model which allows assigning the test item to one of four reactivity classes used to support the discrimination between sensitisers and non-sensitisers (OECD, 2015).
HPLC system suitability was determined by the standard calibration curve and the value of r2 obtained was 1.00000 for cysteine and 0.99999 for lysine peptides, against set standard of r2 > 0.99 as per the guideline.
The mean peptide concentration of Reference Control A and B is as mentioned in the table below:
The mean peptide concentration of Reference Control A and B were mentioned below:
Peptide
Mean Reference Control A (mM)
Mean Reference Control B (mM)
Expected Concentration
(mM)
Cysteine
0.52
0.50
0.45-0.55
Lysine
0.50
0.50
0.45-0.55
The Relative Coefficient of Variability (RCV) for the Reference Control B was 0.16 for cysteine peptide and 1.49 for lysine peptide.
The percent peptide depletion obtained for Cysteine and Lysine is as tabulated below:
Sample Name and Date
Percent Peptide Depletion (Cysteine)
Percent Peptide Depletion (Lysine)
%
Depletion
SD
RCV
Expected
Depletion
%
Depletion
SD
RCV
Expected
Depletion
Cinnamaldehyde
(Positive control)
76
24455.42
6.18
60.8-100
64
10974.35
1.94
40.2-69
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole
2
4137.29
0.25
-
1
4401.97
0.28
-
Percentage peptide depletion values of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole for Cysteine and Lysine were 2% and 1%, respectively. The mean percent depletion for 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was 1.5%.
The relative coefficient of variability (RCV) for the stability of Cysteine peptide in acetonitrile was 2.39% against the set standard of <15% as per the guideline, indicating that Cysteine is stable in acetonitrile. In the case of Lysine peptide, the area obtained in the Co-elution chromatograph was 2389, i.e., only 0.15% of the mean peptide peak area of Reference Control B, which was <10%. Hence it was not considered as Co-elution interference (EURL ECVAM, 2013).
From the results of this study, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was predicted to be a Non-Skin Sensitiser.
- Endpoint:
- skin sensitisation: in vitro
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 30 January 2020 to 08 June 2020
- Reliability:
- 1 (reliable without restriction)
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 442D (In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method)
- Version / remarks:
- 2018
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- other: EC No. 440/2008, L 112, method B60: In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method.
- Version / remarks:
- 2017
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of study:
- activation of keratinocytes
- Justification for non-LLNA method:
- The test system used for the in vitro KeratinoSens assay was KeratinoSens (HaCaT) cell line, an immortalised adherent human keratinocyte cell line. The cell line contains the luciferase gene under the transcriptional control of a constitutive promoter fused with an ARE element from a gene that is known to be up-regulated by contact sensitisers. The KeratinoSens test method has been validated by EURL ECVAM and considered scientifically valid to support the discrimination of skin sensitisers and non-sensitisers for the purpose of hazard identification.
- 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 - Details on the study design:
- DETAILS OF TEST SYSTEM
- The genetically modified HaCaT cell line (KeratinoSensTM) obtained from Givaudan Schweiz AG.
- The KeratinoSensTM cell line contains a stable insertion of the luciferase gene under the transcriptional control of a constitutive SV40 promoter fused with an antioxidant response element (ARE) of the human AKR1C2 gene.
- Source: Mutagenicity section, Jai Research Foundation, India.
- Cell line Lot No.: JRF/HaCaT/2016/01.
VEHICLE
- Dimethyl sulfoxide (DMSO)
- 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was found to be soluble in dimethyl sulfoxide, at the concentration of 200 mM. Hence, dimethyl sulfoxide was selected as the vehicle for this study.
NEGATIVE (SOLVENT) CONTROL: Yes.
DMSO was used as the concurrent negative control for each set of experiments.
Name: DMSO.
CAS Number: 67-68-5
Manufactured by: Qualigens.
Lot N°: 3491020519.
Retest Date: May 2024.
Appearance (Colour): Colourless.
Assay: 99.95%.
Storage: Room temperature.
POSITIVE CONTROL USED: Yes.
Trans-cinnamaldehyde was used as a positive control for which stock concentrations from 0.4 to 6.4 mM were prepared in DMSO, which were further diluted to achieve final concentration of positive control ranging from 4 to 64 µM.
CAS Number: 14371-10-9
Molecular Weight: 132.16.
Manufactured by: Sigma Aldrich..
Batch N°: STBF4119V.
Date of Receipt: 06 October 2015.
Date of Expiry: 05 October 2020.
Appearance (Colour): Light yellow liquid.
Purity: 99.4%.
Storage: 2–8 °C.
Density: 1.05 g/mL.
NUMBER OF REPLICATES, APPLICATION DOSE AND EXPOSURE TIME
- KeratinosensTM (HaCaT) cells were exposed 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole to final test concentrations from 0.98 µM to 2000 µM.
- KeratinosensTM (HaCaT) cells were exposed to Positive control (Trans-cinnamaldehyde) at concentrations: 4 to 64 µM.
- KeratinosensTM (HaCaT) cells were exposed to Negative control (DMSO).
- Cells were incubated for 48 ± 2 hours in 5 ± 1% CO2 at 37 ± 1 °C. After incubation, cells were analysed for luciferase activity.
- Cell viability of the concurrently treated cells was also evaluated using the MTT test with a separate set of plates.
- For each test item and positive control, one experiment consisting of at least two independent repetitions, each containing three replicates of each concentration.
- Each independent repetition was performed on a different day with fresh stock solutions of chemicals and independently harvested cells. - Positive control results:
- Luciferase activity induction obtained with the positive control, trans-cinnamaldehyde, was found to be >1.5 (the threshold value) at concentrations of 16, 32, and 64 µM in experiment 2 and at concentrations of 32 and 64 µM in experiment 4.
The induction for positive control at concentrations of 16, 32, and 64 µM was found to be 1.75, 2.31 and 5.72 µM in experiment 2 and 1.74 and 2.26 µM in experiment 4 at concentrations of 32 and 64 µM.
The EC1.5 for the positive control was 13.12 in experiment 2 and 21.21 in experiment 4.
The average gene induction for the positive control at 64 µM was found to be 5.72 and 2.26 for experiment 2 and 4, respectively (which was within the guideline acceptable limit of 2 and 8).
A clear dose response, with increasing gene induction at increasing dose, was observed for trans-cinnamaldehyde in experiment 2 and experiment 4. - Key result
- Run / experiment:
- other: Imax
- Parameter:
- other: Luciferase gene induction
- Remarks:
- Imax: maximal fold gene-induction (Imax) value observed at any concentration of the test item and positive control.
- Value:
- 1.9
- Vehicle controls validity:
- not examined
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Key result
- Run / experiment:
- other: EC1.5
- Parameter:
- other: Luciferase gene induction
- Remarks:
- EC1.5: value representing the concentration for which a gene induction above the 1.5-fold threshold.
- Value:
- 225.88
- Vehicle controls validity:
- not examined
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Key result
- Run / experiment:
- other: IC50
- Parameter:
- other: Cellular viability
- Remarks:
- IC50: concentration value for 50% reduction of cellular viability.
- Value:
- 2 000
- Vehicle controls validity:
- not examined
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Key result
- Run / experiment:
- other: IC30
- Parameter:
- other: : Cellular viability
- Remarks:
- IC30: concentration value for 30% reduction of cellular viability.
- Value:
- 1 925.82
- Vehicle controls validity:
- not examined
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Other effects / 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. - Interpretation of results:
- other: KeratinoSensTM Prediction: Sensitiser
- Conclusions:
- From the results of this KeratinoSens assay, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is predicted to be a sensitiser to skin.
- Executive summary:
This study was conducted to evaluate the skin sensitisation potential of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole by assessing keratinocyte activation, using a Keratinocyte-Based ARE-Nrf2 Luciferase Reporter Gene method, as recommended by the OECD Test guideline 442D.
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was found to be soluble at 200 mM in dimethyl sulfoxide (DMSO). Therefore, DMSO was selected as a vehicle. The test item was tested in two independent experiments. KeratinosensTM(HaCaT) cells were exposed to 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole at test concentrations of 0.98 µM to 2000 µM, to the positive control (trans-cinnamaldehyde) at concentrations of 4 to 64 µM or to the negative control (DMSO). Cells were incubated for 48 ± 2 hours in 5 ± 1% CO2at 37 ± 1 °C. After incubation, cells were analysed for luciferase activity. Cell viability of the concurrently treated cells was also evaluated using the MTT test with a separate set of plates. The Imaxand EC1.5value was calculated based on luciferase activity, i.e., luminescence measured (reading of three plates) while IC50and IC30were calculated based on the results of cytotoxicity (OD values, reading of one plate).
Test Item Name
Luciferase gene induction
Cellular viability
KeratinoSensTM
Prediction
Imax
EC1.5
IC50
IC30
3-Bromo-1-(3-Chloro-
2-Pyridyl)-5-Methyl-
1H-Pyrazole
1.90
225.88µM
>2000µM
1925.82 µM
Sensitiser
Positive Control
(Trans-Cinnamaldehyde)
3.99
16.68 μM
-
-
Sensitiser
The maximal average fold induction of luciferase activity (Imax), following the treatment with 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole, was 1.60 at a concentration of 250 µM in experiment 2; 2.21, 2.11 and 1.53 at concentrations of 500, 1000 and 2000 µM, respectively, in experiment 4, which are greater than the 1.5-fold increase required for a positive result. The cellular viability was 90.26% at a concentration of 250 µM in experiment 2; 116.96, 94.44 and 74.80% at concentrations of 500, 1000 and 2000 µM, respectively, in experiment 4, with induction of luciferase activity above 1.5 fold.
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole met all the evaluation criteria to be concluded as a sensitizer in the KeratinoSens assay. Negative and positive controls met the acceptance criteria for the controls and were correctly identified as non-sensitizer and sensitizer, respectively. All criteria for a valid study were met, as described in the study plan.
From the results of this KeratinoSens assay, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is predicted to be a sensitiser to skin.
- Endpoint:
- skin sensitisation: in vitro
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 30 January 2020
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- other: OECD 442E, In Vitro Skin Sensitisation: Human Cell Line Activation test (h-CLAT Test Method)
- Version / remarks:
- June 2018
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- other: EU Method B7:In Vitro Skin Sensitisation: Human Cell Line Activation test (h-CLAT Test Method).
- Version / remarks:
- July 2019
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of study:
- activation of dendritic cells
- Justification for non-LLNA method:
- The test system used for the in vitro human cell line activation test (hCLAT assay) was the THP 1 cell line which is used as a surrogate of dendritic cells (DC). Upon contact with sensitizers, upregulation of cell surface markers (i.e., CD86 and CD54) on these cells can be measured, which may mimic DC activation. This cell line is the recommended test system by OECD 442E for the assay.
- Specific details on test material used for the study:
- 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 - Details on the study design:
- DETAILS OF TEST SYSTEM
- Test system: THP-1, a human monocytic leukemia cell line, procured from American Type Culture Collection (ATCC), maintained at the Mutagenicity section, Jai Research Foundation as specified in OECD 442E.
- The doubling time of THP-1 cells was found to be approximately 24 h.
- Cells of passage number 23 (DRF experiments-1 and 2), 07 (Reactivity check), 15 [Expression study (experiment -1)] and 16 [Expression study (experiment -2)] were used for the study. Batch number of the cell line used was 63176297 for the study.
- Batch number of the cell line used was 63176297 for the study.
CULTURE MEDIUM
The medium used for culturing cells as well as during the assay consisted of RPMI-1640 with
2 mM L-glutamine and 25 mM HEPES supplemented with 10% v/v Fetal Bovine Serum (FBS), 0.05 mM 2-Mercaptoethanol and appropriate antibiotics (100 U/mL penicillin and 100 µg/mL streptomycin).
CONTROLS
Concurrent positive and negative control were included in each set of experiment.
POSITIVE CONTROL
2,4-Dinitrochlorobenzene was used as a positive control during CD86/CD54 expression measurement, tested at a single concentration of 4.0 µg/mL in DMSO.
Name: 2, 4-Dinitrochlorobenzene
CAS Number: 97-00-7
Molecular Weight: 202.55 g/mol
Manufactured by: Sigma Aldrich
Batch N°: STBD7009V
Date of receipt: September 21, 2015
Date of expiry: September 20, 2020
Appearance (color): Brown Crystalline chunk(s)
Purity: 99.9%
Storage: Room temperature
NEGATIVE CONTROL
Concurrent negative controls, consisting of solvent and complete medium alone, without test item was included in each assay.
Medium Control: Complete medium.
DMSO Control: DMSO diluted to 0.4% in complete medium, which was tested at a final concentration of 0.2% in the plate.
SOLVENTS AND CHEMICALS
RPMI-1640 (1X): Gibco (Lot # 2120429)
Fetal Bovine Serum: Gibco (Lot # 1841109)
Penicillin Streptomycin: Gibco (Lot # 214554)
2-Mercaptoethanol: Gibco (Lot # 1929845)
DPBS (1X): Gibco (Lot # 2085310)
Dimethyl Sulfoxide: Sigma (Lot # SHBG5286V)
Globulin Cohn Fraction II, III
Human, lyophilized powder: Sigma (Lot# 017K7650V)
Bovine Serum Albumin: HiMedia (Lot #0000345510)
Phosphate buffered Saline
Tablets: Sigma (Lot #SLBW3999)
FITC mouse anti-human CD86
Antibody (Clone: Fun-1): BD Pharmingen (Lot #7348597)
Monoclonal mouse anti-human
CD54, ICAM-1 antibody/FITC
(Clone 6.5 B5): Dako (Lot #20051521)
Isotype reagent mouse IgG1/
FITC antibody: Dako (Lot #20058363)
Propidium iodide: Sigma (Lot #MKCC9922)
Tryphan blue solution: Sigma (Lot #RNBF6596)
FACSFlow Sheath fluid: BD (Lot #1903002839)
FACS Clean: BD (Lot #1908002830)
FACSuite CS&T Research
Beads: BD (Lot #91487)
Dettol (Disinfectant Solution): Reckitt Benckiser (Lot #GL991)
CULTURE VESSELS
- Disposable tissue cultures flasks of 75 cm2 culture area with canted neck (Nunc) was used for culturing cells and treatment was performed in 96-well flat-bottom transparent plates (for Dose Range Finding assay) and 24-well culture plates (for CD86/CD54 Expression Measurement).
VEHICLE
- DMSO was selected as a vehicle for the study and the highest stock concentration selected was 500 mg/mL. - Positive control results:
- The acceptance criteria for the positive control were met:
The RFI values of CD86 and CD54 were greater than 150% and ≥200%, respectively, and the cell viability was greater than 50%, in both experiments. - Key result
- Run / experiment:
- other: h-CLAT assay: Observed EC200 for CD54 (µg/mL)
- Parameter:
- other: Calculated Effective Concentration (EC) value.
- Value:
- 248
- Vehicle controls validity:
- valid
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Key result
- Run / experiment:
- other: h-CLAT assay: Observed EC150 for CD86 (µg/mL)
- Parameter:
- other: Calculated Effective Concentration (EC) value.
- Value:
- 474
- Vehicle controls validity:
- valid
- Negative controls validity:
- valid
- Positive controls validity:
- valid
- Remarks on result:
- positive indication of skin sensitisation
- Other effects / acceptance of results:
- ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: Yes.
- Acceptance criteria met for positive control: Yes. - Interpretation of results:
- Category 1 (skin sensitising) based on GHS criteria
- Conclusions:
- From results of this h-CLAT assay, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was concluded as “positive” in an in vitro skin sensitisation assay and may be predicted to be a skin sensitiser skin according to EC regulation 1272/2008 (CLP).
- Executive summary:
This study was conducted to evaluate the skin sensitization potential of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole based on the human cell line activation test (h-CLAT) method, as recommended by the OECD 442E.
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole found to be soluble in dimethyl sulfoxide (DMSO) at the final concentration of 500 mg/mL. Hence, DMSO was selected as a vehicle for this study.
Two Dose Range Finding (DRF) assays were performed to determine CV75 value of the test item. For DRF assays, THP-1 cells were exposed to the test item at ten concentrations between 1.95 µg/mL and 1000 µg/mL and incubated for 24 ± 0.5 h at 37 ± 1 °C under 5 ± 1% CO2. After incubation, cells were washed, stained with propidium iodide, and analyzed on flow cytometer, to determine cell viability (for the calculation of CV75 value). On the basis of CV75 value of the test item, i.e., >1000 µg/mL, concentrations were selected for CD86/CD54 expression measurement.
CD86/CD54 expression measurement (expression study), was performed to determine the expression of CD86 and CD54 cell surface markers at the sub-cytotoxic concentrations of the test item. For the assay, THP-1 cells were exposed to the test item at eight concentrations between 279 µg/mL and 1000 µg/mL and incubated for 24 h at 37 ± 1 °C under 5 ± 1% CO2. After incubation, cells were washed, blocked, stained with specific antibodies and propidium iodide, and analyzed on the flow cytometer. Based on results of Expression study, RFI values of the test item were calculated and used in a prediction model to support the discrimination between the sensitizer and non-sensitizer.
The test item produced a positive response for CD86 marker (i.e., RFI CD86 ≥150%, with cell viability ≥50%) in 5/8 and 6/8 tested concentrations in experiments-1 and 2, respectively. The test item also produced a positive response for CD54 marker (i.e., RFI CD54 ≥200%, with cell viability ≥50%) in 8/8 and 8/8 tested concentrations in experiments-1 and 2, respectively. The cell viability of the test item was found to be >50% at all tested concentrations in both experiments, which met the assay acceptance criteria. Based on results of experiments-1 and 2, the predictions obtained for the test item were P12 and P12, respectively. Based on the calculated RFI CD86 and CD54 values, the EC150 and EC200 values were calculated as below:
Observed CV75
(µg/mL)
Observed EC150 for CD86
(µg/mL)*
Observed EC200 for CD54
(µg/mL)*
Expt. 1 Prediction
Expt. 2 Prediction
Final Prediction
>1000
474
248
Positive (P12)
Positive (P12)
Positive
Key: * = Higher EC150 and EC200 value of test item
The RFI values of positive control, i.e., 2, 4-Dinitrochlorobenzene were greater than 150% for CD86 marker, and greater than 200% for CD54 marker in both experiments-1 and 2, and met the assay acceptance criteria. (RFI CD86 ≥150%, RFI CD54 ≥200%). The cell viability of the positive control was >50% in both experiments. All observed values of the negative (solvent) control were within the acceptable ranges of the test guideline. All criteria for a valid study were met, as described in the study plan.
From the results of this h-CLAT assay, under the specified experimental conditions, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was concluded as “positive” in an in vitro skin sensitization assay and may be predicted to be a skin sensitizer.
Referenceopen allclose all
Reference Controls
The relative coefficient of variability (RCV) of peptide peak areas for the Reference Control B in acetonitrile was 0.16% for Cysteine peptide and 1.49% for Lysine peptide
Mean Reference Control Concentrations:
Peptide |
Mean Reference Control A (mM) |
Mean Reference Control B (mM) |
Expected Concentration (mM) |
Cysteine |
0.52 |
0.50 |
0.45-0.55 |
Lysine |
0.52 |
0.50 |
0.45-0.55 |
Cysteine Peptide Stability in Acetonitrile
The stability of Cysteine peptide in acetonitrile was checked at 0, 24, and 48 h. The relative coefficient of variability (RCV) for the stability of Cysteine peptide in acetonitrile was 2.39% against set standard of <15%. This showed that Cysteine peptide was stable in acetonitrile.
Data of Precipitation for Cysteine and Lysine Peptide:
Test Item Name |
Precipitation/Phase Separation (Yes/No) |
|
Cysteine |
Lysine |
|
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole-Replicate 1 |
No |
No |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole-Replicate 2 |
No |
No |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole-Replicate 3 |
No |
No |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole- Co-elution control |
No |
No |
Standard Curve
A standard calibration curve was generated on each day of the HPLC analysis and the value of r2 obtained was 1.00000 for Cysteine and 0.99999 for Lysine containing peptides. This showed that system was suitable for assay.
Percent Peptide Depletion
% Mean Depletion of Peptides with Test Item:
Test Item Name |
Actual % Depletion (Cysteine) |
Actual % Depletion (Lysine) |
% Mean Depletion (Cysteine and Lysine) |
Maximum Standard Deviation (Cysteine) |
Maximum Standard Deviation(Lysine) |
DPRA Prediction |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole |
2 |
1 |
1.2 |
0.25 |
0.28 |
Non-Sensitizer (Negative) |
Negative Control
The coefficient of variation observed for the negative control, during experiment 2 and 4 for 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was 17.57% and 13.43%, respectively, which was below 20%. Since variation amongst the replicates was less than 20%, results of this run were considered as valid.
Luciferase Activity
The maximal average fold induction of luciferase activity (Imax) following treatment with 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was 1.60 at a concentration of 250 μM in experiment 2; 2.21, 2.11 and 1.53 at concentrations of 500, 1000 and 2000 μM, respectively, in experiment 4, which are greater than the 1.5-fold increase, required for a positive result. The EC1.5 mean values, representing the concentration where induction of luciferase activity is above the 1.5 fold threshold (i.e 50% enhanced luciferase activity), for 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole was 263.09 μM.
In Vitro Skin Sensitisation: Keratinocyte-Based ARE-Nrf2 Luciferase Reporter Gene Test of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole.
Mean Summary of Luciferase Activity Induction and Cellular Viability Values:
Imax(Maximal average fold induction of luciferase activity):
Test Item |
Rep2 |
Rep4 |
Average |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole |
1.60 |
2.21 |
1.90 |
trans-Cinnamaldehyde |
5.72 |
2.26 |
3.99 |
EC1.5(Concentration for which induction of luciferase activity is above the 1.5-fold threshold:
Test Item |
Rep2 |
Rep4 |
GeoMean |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole |
193.93µM |
263.09µM |
225.88µM |
trans-Cinnamaldehyde |
13.12 µM |
21.21 µM |
16.68 µM |
IC50(Concentration value for 50% reduction of cellular viability):
Test Item |
Rep2 |
Rep4 |
GeoMean |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole |
>2000µM |
>2000µM |
>2000µM |
IC30(Concentration value for 30% reduction of cellular viability):
Test Item |
Rep2 |
Rep4 |
GeoMean |
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole |
1925.82µM |
>2000µM |
1925.82µM |
Key: Rep = Repetition/Experiment – each comprising 3 plates.
Note: Values shown for each repetition are the mean values of 3 replicates.
IC50 and IC30 cannot be determined for positive control.
In Vitro Skin Sensitisation: Keratinocyte-Based ARE-Nrf2 Luciferase Reporter Gene Test of 3-Bromo-1-(3-Chloro-2-Pyridinyl)-1H-Pyrazole-5-Carboxylic acid using KeratinoSensTM (HaCat) Cell line
Summary of Mean Luciferase Activity Induction Values (Mean of Two Repetitions /Experiments):
3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole (µM) |
Fold Luciferase Activity Induction |
|
Mean |
SD |
|
0.98 |
1.09 |
0.09 |
1.95 |
1.12 |
0.06 |
3.91 |
1.15 |
0.17 |
7.81 |
1.17 |
0.13 |
15.63 |
1.15 |
0.12 |
31.25 |
1.17 |
0.14 |
62.5 |
1.12 |
0.09 |
125 |
1.40 |
0.04 |
250 |
1.53 |
0.10 |
500 |
1.70 |
0.71 |
1000 |
1.66 |
0.64 |
2000 |
1.42 |
0.15 |
Cytotoxicity Assessment
The cellular viability was 90.26% at a concentration of 250 μM in experiment 2; 116.96, 94.44, and 74.80% at concentrations of 500, 1000, and 2000 μM, respectively, in experiment 4, with induction of luciferase activity above 1.5 fold.
Interpretation
For 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole, four experiments were conducted and out of these, two valid experiments (experiment 2 and 4) were considered for the final evaluation. The reason for conducting the repeat experiments was due to the variation between each replicate of the test item and due to the failure of the negative control to meet the acceptance criteria in experiment 1 and experiment 3, respectively).
The mean results are summarised below:
Test Item Name |
Luciferase gene induction |
Cellular viability |
KeratinoSensTM Prediction |
||
Imax |
EC1.5 |
IC50 |
IC30 |
||
3-Bromo-1-(3-Chloro- 2-Pyridyl)-5-Methyl- 1H-Pyrazole |
1.90 |
225.88µM |
>2000µM |
1925.82 µM |
Sensitiser |
Positive Control (Trans-Cinnamaldehyde) |
3.99 |
16.68 μM |
- |
- |
Sensitiser |
Results of this KeratinoSensTM assay indicate that 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1HPyrazole met all the evaluation criteria to predict that it is a sensitizer in this test. The negative and positive controls met the acceptance criteria and were correctly identified as the non-sensitiser and sensitiser, respectively. This showed the suitability of the test system and procedures used.
Dose
Dose Range Finding (DRF) assay
Two independent experiments of Dose Range Finding (DRF) assay were performed (with concentrations ranging from 1.95 µg/mL to 1000 µg/mL) to determine the CV75 value of the test item (the concentration showing 75% of THP-1 cell survival, i.e., 25% cytotoxicity).
In DRF experiment-1 and 2, significant cell death (i.e., <75% viability) was not observed at any concentration up to 1000 µg/mL.
CD86/CD54 Expression Measurement (Expression Study)
Two independent experiments were performed to determine the upregulation of CD86/CD54 markers at sub-cytotoxic concentrations of the test item (with concentrations ranging from 279 µg/mL to 1000 µg/mL). The results of two valid experiments (i.e, experiments-1 and 2), which met the acceptance criteria are presented here. Based on the geometric MFI values, the RFI of CD86 and CD54 was calculated.
Negative (Solvent) Control
Medium Control
The MFI ratio of the medium control for CD86 to isotype control and for CD54 to isotype control was found to be 268.02% and 108.90% respectively, in experiment-1, and 193.22% and 114.43% respectively, in experiment-2.
The MFI ratio of the medium control for CD86 and CD54 to isotype control was found to be >105% in both experiments.
The cell viability of the medium control was found to be 98.7% and 99.4% in experiments-1 and 2, respectively. The cell viability of the medium control was >90% in both experiments.
DMSO Control
RFI values and the MFI ratio of CD86 and CD54 markers to isotype control for experiment-1 and experiment-2:
Parameters |
Expt.1 |
Expt.2 |
Acceptance Value |
RFI CD86 |
85.39% |
107.54% |
<150% |
RFI CD54 |
112.66% |
70.43% |
<200% |
MFI ratio CD86 to isotype control |
243.79% |
199.75% |
>105% |
MFI ratio CD54 to isotype control |
110.05% |
110.11% |
>105% |
Cell viability |
98.6% |
99.2% |
>90% |
The acceptance criteria were met for DMSO control:
· the RFI values of CD86 and CD54 were less than 150% and 200%, respectively, in both experiments;
· the MFI ratio for CD86 and CD54 markers to isotype control was greater than 105% in both experiments;
· the cell viability was greater than 90% in both experiments.
Positive Control
RFI values of CD86 and CD54 markers and cell viability:
Parameters |
Expt.1 |
Expt.2 |
Acceptance Value |
RFI CD86 |
395.13% |
464.46% |
≥150% |
RFI CD54 |
719.01% |
1038.27% |
≥200% |
Cell viability |
91.1% |
97.0% |
≥50% |
The acceptance criteria for the positive control were met:
The RFI values of CD86 and CD54 were greater than 150% and ≥200%, respectively, and the cell viability was greater than 50%, in both experiments.
The test item produced a positive response for CD86 marker (i.e., RFI CD86 ≥150%, with cell viability ≥50%) in 5/8 and 6/8 tested concentrations in experiments-1 and 2, respectively. The test item also produced a positive response for CD54 marker (i.e., RFI CD54 ≥200%, with cell viability ≥50%) in 8/8 and 8/8 tested concentrations in experiments-1 and 2, respectively. The cell viability of the test item was found to be >50% at all tested concentrations in both experiments, which met the assay acceptance criteria.
The individual values of the cell viability, MFI, and RFI of the test item obtained in the individual experiments of CD86/CD54 Expression Measurement are provided in the following table.
CD86/CD54 Expression Measurements: Cell Viability, MFI and RFI Values of 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole:
Conc. (µg/mL) |
Expt.1 |
||||||||
IgG1 |
% Cell Viability |
MFI |
% RFI |
||||||
Total Count |
THP-1 cells | Count (Number of Gated cells) |
THP-1 cells/ Propidium Iodide-A- | Count (Number of Live cells) |
IgG1 |
CD86 |
CD54 |
CD86 |
CD54 |
||
1000 |
11287 |
9140 |
8849 |
96.8 % |
130 |
341 |
157 |
165.62 |
303.37 |
833 |
11239 |
9206 |
8950 |
97.2 % |
120 |
336 |
150 |
169.54 |
337.08 |
694 |
11270 |
9253 |
9039 |
97.7 % |
112 |
315 |
138 |
159.34 |
292.13 |
579 |
11191 |
9332 |
9129 |
97.8 % |
116 |
319 |
143 |
159.34 |
303.37 |
482 |
11130 |
9292 |
9096 |
97.9 % |
108 |
301 |
135 |
151.49 |
303.37 |
402 |
11182 |
9236 |
8987 |
97.3 % |
116 |
291 |
140 |
137.36 |
269.66 |
335 |
11052 |
9284 |
9067 |
97.7 % |
116 |
268 |
142 |
119.31 |
292.13 |
279 |
11070 |
9375 |
9197 |
98.1 % |
110 |
233 |
131 |
96.55 |
235.96 |
Conc. (µg/mL) |
Expt.2 |
||||||||
IgG1 |
% Cell Viability |
MFI |
% RFI |
||||||
Total Count |
THP-1 cells | Count (Number of Gated cells) |
THP-1 cells/ Propidium Iodide-A- | Count (Number of Live cells) |
IgG1 |
CD86 |
CD54 |
CD86 |
CD54 |
||
1000 |
12121 |
8644 |
8453 |
97.8 % |
117 |
266 |
143 |
186.48 |
320.99 |
833 |
11667 |
8963 |
8840 |
98.6 % |
107 |
258 |
135 |
188.99 |
345.68 |
694 |
12024 |
8765 |
8600 |
98.1 % |
106 |
256 |
132 |
187.73 |
320.99 |
579 |
11544 |
9082 |
8991 |
99.0 % |
102 |
237 |
128 |
168.96 |
320.99 |
482 |
11838 |
8885 |
8752 |
98.5 % |
112 |
251 |
141 |
173.97 |
358.02 |
402 |
11721 |
8923 |
8780 |
98.4 % |
109 |
228 |
135 |
148.94 |
320.99 |
335 |
11606 |
8952 |
8832 |
98.7 % |
105 |
238 |
140 |
166.46 |
432.10 |
279 |
11284 |
9255 |
9155 |
98.9 % |
103 |
208 |
128 |
131.41 |
308.64 |
Shaded values indicate %RFI ≥150% (CD86) or ≥200% (CD54) with cell viability ≥50%
Based on results of experiments-1 and 2, the prediction obtained for the test item was P12 and P12, respectively, and the Effective Concentrations (EC) values were calculated. The mean values and assay predictions for the test item is summarised below:
Observed CV75 (µg/mL) |
Observed EC150 for CD86 (µg/mL)^ |
Observed EC200 for CD54 (µg/mL)* |
Expt. 1 Prediction |
Expt. 2 Prediction |
Final Prediction |
>1000 |
474 |
248 |
Positive (P12) |
Positive (P12) |
Positive |
Key: * = Higher EC150 and EC200 value of test item
Individual results of CV75, EC150, and EC200, in different experiments, are provided in the following table.
Individual CV75, EC150 and EC200 values of all experiments:
Sr. No |
Parameters |
Expt.1 |
Expt.2 |
Average values (in µg/mL) |
1 |
CV75 (in µg/mL) |
>1000* |
>1000* |
>1000 |
2 |
EC150 (in µg/mL) |
474 |
309 |
474# |
3 |
EC200 (in µg/mL) |
248 |
238 |
248# |
Key: * = CV75 values are from DRF Experiments 1 and 2, respectively, # = Higher EC150 and EC200 value out of the two experiments.
Interpretation
In both the experiments-1 and 2, a positive response was obtained for CD86 and CD54 (P12). The final prediction for the test item was “positive”.
The final EC150 and EC200 value were determined as the median value of the ECs calculated from the two acceptable independent runs. The EC150 and EC200 values reported were the higher EC value from the two valid experiments that met the criteria for positivity.
Results of the present study indicate that, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole met all the evaluation criteria to conclude as the “positive” in h-CLAT assay. The negative and the positive controls met the specified acceptance criteria for controls. This showed the suitability of the test system and procedures used in this test facility.
Endpoint conclusion
- Endpoint conclusion:
- adverse effect observed (sensitising)
Respiratory sensitisation
Endpoint conclusion
- Endpoint conclusion:
- no study available
Justification for classification or non-classification
Based on two in vitro skin sensitisation tests according to OECD 442D and OECD 442E, 3-Bromo-1-(3-Chloro-2-Pyridyl)-5-Methyl-1H-Pyrazole is determined to be a sensitising substance to skin.
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