Cyclohexyl isocyanate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 442C (In Chemico Skin Sensitisation Assays addressing the Adverse Outcome Pathway key event on covalent binding to proteins)

Version / remarks:

Adopted: 30 June 2022

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: - DB-ALM Protocol No.154: Direct Peptide Reactivity Assay (DPRA) for Skin Sensitisation Testing, 31 January 2019

GLP compliance:

yes (incl. QA statement)

Type of study:

direct peptide reactivity assay (DPRA)

Test material

Test material information

1

Reference substance name:

Cyclohexyl isocyanate

EC Number:

221-639-3

EC Name:

Cyclohexyl isocyanate

Cas Number:

3173-53-3

Molecular formula:

C7H11NO

IUPAC Name:

isocyanatocyclohexane

Test material form:

liquid

In chemico test system

Details of test system:

cysteine peptide, (Ac-RFAACAA-COOH)

lysine peptide (Ac-RFAAKAACOOH)

Details on the study design:

Synthetic heptapeptides containing either cysteine or lysine are incubated with the test item at 25 °C for 24 hours. Depletion of the peptide in the reaction mixture is measured by high pressure liquid chromatography (HPLC) using UV detection. Average peptide depletion data for cysteine and lysine are then calculated.

Vehicle / solvent:

acetonitrile

Positive control:

cinnamic aldehyde

Results and discussion

In vitro / in chemico

Results

Results 1

Key result

Group:

test chemical

Run / experiment:

mean

Parameter:

lysine depletion

Value:

23.5 %

Negative controls validity:

valid

Positive controls validity:

valid

Results 2

Key result

Group:

test chemical

Run / experiment:

mean

Parameter:

cysteine depletion

Value:

94.5 %

Negative controls validity:

valid

Positive controls validity:

valid

Outcome of the prediction model:

high reactivity [in chemico]

Other effects / acceptance of results:

The criteria of quality are in accordance with the OECD TG 442C, In chemico skin sensitization assays addressing the Adverse Outcome Pathway Key Event on Covalent Binding to Proteins, Adopted: 30 June 2022, Appendix I: In Chemico Skin Sensitisation: The Direct Peptide Reactivity Assay (DPRA)

Applicant's summary and conclusion

Conclusions:

The test item, Cyclohexyl isocyanate, has been found positive in the DPRA prediction; it was assigned to reactivity class “high reactivity”.
The data generated with this test should be considered in the context of integrated approached such as IATA, combining the result with other complementary information, e.g. derived from in vitro assays addressing other key events of the skin sensitisation AOP.

Executive summary:

The purpose of the test is to contribute to the evaluation of the skin sensitisation potential of Cyclohexyl isocyanate. This study is a part of this test item health hazard evaluation for registration of industrial chemicals.

In the study, Cyclohexyl isocyanate was dissolved in acetonitrile, based on the results of the pre-experiments. The stock solution at concentration 100 mM was prepared based on a molecular weight of 125.17 g/mol.

The test item solutions were tested by incubating the samples with synthetic heptapeptides containing either cysteine or lysine at 25 °C for 24 ± 2 hours. Depletion of the peptide in the reaction mixture was measured by HPLC with UV detection. Average peptide depletion data for cysteine and lysine were calculated. Cinnamaldehyde (100 mM) was used as a positive control and 1-butanol (100 mM) was used as a negative control. Each test chemical was prepared and analysed in triplicate for both peptides.

All study acceptance criteria (see page 16) have been successfully met.

The mean of Cysteine and Lysine percent depletion values is 59.0 %. Based on the obtained results, the prediction model the Cysteine 1:10/Lysine 1:50 was used for evaluation. The test item, Cyclohexyl isocyanate, has been found positive in the DPRA prediction; it was assigned to reactivity class “high reactivity” for both peptides.

The data generated with this test should be considered in the context of integrated approached such as IATA, combining the result with other complementary information, e.g. derived from in vitro assays addressing other key events of the skin sensitisation AOP.