Reaction mass of 2,4-bis(2-chlorophenyl)-1-[2-(2-chlorophenyl)-4,5-diphenylimidazol-1-yl]-5-(3,4-dimethoxyphenyl)imidazole and 1-[2,4-bis(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)imidazol-1-yl]-2,4-bis(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)imidazole and 2-(2-chlorophenyl)-1-[2-(2-chlorophenyl)-4,5-diphenylimidazol-1-yl]-4,5-diphenylimidazole

Endpoint summary

Description of key information

Based on the results of this study, an indication of the classification for the substance is as follows:

Not Classified as a Skin Sensitiser

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

September 18, 2018 -October 09, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

OECD 429

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA:J

Sex:

female

Vehicle:

dimethylformamide

Concentration:

1%, 10% and 25% (w/v) test item in dimethylformamide

No. of animals per dose:

5 mice/group

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Positive control results:

The SI of 5.49 obtained for the positive control, α-Hexylcinnamaldehyde, showed greater than a three-fold increase over the control value indicating a positive response in agreement with the historical control for this known weak sensitiser. This confirmed the reliability of this test procedure.

Key result

Parameter:

SI

Value:

1

Test group / Remarks:

G1Vehicle [DMF]

Key result

Parameter:

SI

Value:

1.18

Test group / Remarks:

G2 1% (w/v) test item in DMF

Key result

Parameter:

SI

Value:

2.03

Test group / Remarks:

G3 10% (w/v) test item in DMF

Key result

Parameter:

SI

Value:

2.38

Test group / Remarks:

G4 25% (w/v) test item in DMF

Key result

Parameter:

SI

Value:

5.49

Test group / Remarks:

G5 25% (v/v) HCA in DMF

Interpretation of results:

GHS criteria not met

Conclusions:

Based on the results of this study, an indication of the classification for the substance is as follows:
Globally Harmonized System of Classification and Labelling of Chemicals (GHS 2017): Not Classified as a Skin Sensitiser

Executive summary:

The Local Lymph Node Assay was conducted to evaluate the skin sensitisation potential of the reaction mass in CBA/J strain mice in compliance with the OECD 429 test guideline.

A preliminary assay was conducted to identify the appropriate test concentrations for the Local Lymph Node Assay for main study.

In the main assay, five groups of mice comprising 5 females per group were selected. Based on the results of the preliminary assay, three groups were treated at dose concentrations of 1%, 10% and 25% (w/v) test item in dimethylformamide for three consecutive days (days 0, 1 and 2) on the dorsum of both ears (25mL per ear). In addition, one group served as the vehicle control and was treated with dimethylformamide and another group served as the positive control and was treated at a concentration of 25% (v/v) HCA (a-hexylcinnamaldehyde) in dimethylformamide.

Animals were observed for clinical reactions. Animals were weighed at the beginning and at the end of treatment. On day 5, the uptake of intravenously injected³H-methyl thymidine into the auricular (local) lymph nodes draining at the site of chemical application was measured (5 hours post-administration) to assess the lymph node proliferative response.

There were no indications of local irritation or systemic toxicity in the test item treated animals. In all mice treated with 25% (v/v) HCA, a local reaction consisting of very slight erythema (score of 1) was observed from days 1 to 4. Group mean body weight of treated animals and positive control group animals were comparable with the mean body weight of the vehicle control group.

Stimulation indices (SI) for the1%, 10% and 25% (w/v)CZ-HABIindimethylformamidetreated groups were 1.18, 2.03 and 2.38, respectively (i.e., less than three-fold increase over mean vehicle control group). Therefore, the test item did not demonstrate dermal sensitisation potential in the local lymph node assay. All criteria for a valid study were met as described in the study plan. The vehicle control and positive control in the definitive LLNA were within the acceptable ranges and fulfilled the requirements for a valid assay.

A positive response for HCA (SI = 5.49) confirmed the reliability of the test procedure.

Based on the results of this study, an indication of the classification for the reaction mass is as follows:

Globally Harmonized System of Classification and Labeling of Chemicals (GHS 2017):        

Not Classified as a Skin Sensitiser

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Justification for classification or non-classification

The Local Lymph Node Assaywas conducted to evaluate the skin sensitisation potential of the reaction mass in CBA/J strain mice in compliance with theOECD 429test guideline.

A preliminary assay was conducted to identify the appropriate test concentrations for the Local Lymph Node Assay for main study.

In the main assay, five groups of mice comprising 5 females per group were selected. Based on the results of the preliminary assay, three groups were treated at dose concentrations of 1%, 10% and 25% (w/v) test itemindimethylformamide for three consecutive days (days 0, 1 and 2) on the dorsum of both ears (25mL per ear). In addition, one group served as the vehicle control and was treated with dimethylformamide and another group served as the positive control and was treated at a concentration of 25% (v/v) HCA (a-hexylcinnamaldehyde) in dimethylformamide.

Animals were observed for clinical reactions. Animals were weighed at the beginning and at the end of treatment. On day 5, the uptake of intravenously injected³H-methyl thymidine into the auricular (local) lymph nodes draining at the site of chemical application was measured (5 hours post-administration) to assess the lymph node proliferative response.

There were no indications of local irritation or systemic toxicity in the test item treated animals. In all mice treated with 25% (v/v) HCA, a local reaction consisting of very slight erythema (score of 1) was observed from days 1 to 4. Group mean body weight of treated animals and positive control group animals were comparable with the mean body weight of the vehicle control group.

Stimulation indices (SI) for the1%, 10% and 25% (w/v)CZ-HABIindimethylformamidetreated groups were 1.18, 2.03 and 2.38, respectively (i.e., less than three-fold increase over mean vehicle control group). Therefore, the test item did not demonstrate dermal sensitisation potential in the local lymph node assay. All criteria for a valid study were met as described in the study plan. The vehicle control and positive control in the definitive LLNA were within the acceptable ranges and fulfilled the requirements for a valid assay.

A positive response for HCA (SI = 5.49) confirmed the reliability of the test procedure.

Based on the results of this study, an indication of the classification for the reaction massisas follows:

 

Not Classified as a Skin Sensitiser