Dibutyl itaconate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian cell study: DNA damage and/or repair

Type of information:

experimental study planned

Study period:

Within two years after ECHA approval.

Justification for type of information:

TESTING PROPOSAL ON VERTEBRATE ANIMALS
NON-CONFIDENTIAL NAME OF SUBSTANCE:
- Name of the substance on which testing is proposed to be carried out: Dibutyl itaconate
CONSIDERATIONS THAT THE GENERAL ADAPTATION POSSIBILITIES OF ANNEX XI OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
- Available GLP studies: In an AMES test, performed according to OECD/EC guidelines and GLP principles, Dibutyl itaconate was found not to be mutagenic with or without metabolic activation. There are no other GLP studies available for genotoxicity.
- Available non-GLP studies: There are no non-GLP studies available for the endpoint genetic toxicity.
- Historical human data: There are no historical human data that can be considered for this endpoint.
- (Q)SAR: An OECD toolbox assessment resulted in alerts for genotoxic properties via DNA and protein binding (see attached supplementary information).
- In vitro methods: Itaconates have been shown to exhibit cytotoxicity (Cordes et al, THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 291, NO. 27; Lampropoulou et al, Cell Metab. 2016 July 12; 24(1)). The misleading effect of cytotoxicity on the outcome of an in vitro genotoxicity study with mammalian cells has been described by several authors (among which Armstrong et al, Mutation research 265 (1992), Kirkland et al, Mutation Research 628 (2007); Fowler et al., Mutation Research 742 (2012); Honda et al. Genes and Environment (2018)). It is therefore concluded that it is scientifically not justified to perform in vitro testing, as a positive outcome is expected related to cytotoxicity and not related to intrinsic genotoxic properties of the test item (“false positive” result).
- Weight of evidence: As no reliable outcome is expected from the required in vitro tests with mammalian cells due to cytotoxicity, it is proposed to address the potential genotoxic properties of DBI in an in vivo COMET assay. This is strengthened by the fact that structural analogues of DBI with shared chemical subgroups were found to give (false) positive results when tested in in vitro tests with mammalian cells. Performance of an in vivo study is considered to be the only strategy possible to address this endpoint.
- Grouping and read-across: Read across to structurally related itaconates (with shared sub-structures) has been considered. However based on the observed behaviour of the substance in aqueous solution, read-across was not considered scientifically justified.
- Substance-tailored exposure driven testing: Not applicable for genetic toxicity endpoint
- Approaches in addition to above: Not applicable
- Other reasons: Not applicable
CONSIDERATIONS THAT THE SPECIFIC ADAPTATION POSSIBILITIES OF ANNEXES VI TO X (AND COLUMN 2 THEREOF) OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
The specific rules for adaptation from column 1 as given in column 2 are not applicable for in vivo genotoxicity testing.
FURTHER INFORMATION ON TESTING PROPOSAL IN ADDITION TO INFORMATION PROVIDED IN THE MATERIALS AND METHODS SECTION:
- Details on study design: As no reliable outcome is expected from the required in vitro tests with mammalian cells, it is proposed to address the potential genotoxic properties of DBI in an in vivo COMET assay. As this assay addresses all potential mode-of-actions (the COMET assay recognises primary DNA damage that would lead to gene mutations and/or chromosome aberrations, but will also detect DNA damage that may be effectively repaired or lead to cell death), performance of this in vivo study is considered to be sufficient to conclude on this endpoint. The oral route is considered to be the most appropriate route, as no sex-specific toxicity is expected, the test is performed in a single species. As no tissue-specific toxicity is expected, blood and liver samples will be tested.

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 489 (In vivo Mammalian Alkaline Comet Assay)

Version / remarks:

most recent version

Deviations:

no

GLP compliance:

yes

Type of assay:

mammalian comet assay

Test material

Test material information

Constituent 1

Reference substance name:

Dibutyl itaconate

EC Number:

218-451-9

EC Name:

Dibutyl itaconate

Cas Number:

2155-60-4

Molecular formula:

C13H22O4

IUPAC Name:

1,4-dibutyl 2-methylidenebutanedioate

Test material form:

liquid

Test animals

Species:

rat

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage