1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: gene mutation

Type of information:

experimental study planned

Remarks:

Although applicant disagrees in view of lack of concerns, a study proposal was entered as result to failure of dossier acceptance from lack of in vivo results in combination of the positive Ames study.

Justification for type of information:

TESTING PROPOSAL ON VERTEBRATE ANIMALS

NON-CONFIDENTIAL NAME OF SUBSTANCE:
1,1,3,3-Tetramethylbutyl peroxy-2-ethylhexanoate, CAS 22288-43-3

CONSIDERATIONS THAT THE GENERAL ADAPTATION POSSIBILITIES OF ANNEX XI OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION [please address all points below]:
- Available GLP studies:
All available studies on this substance are included in this dossier. There are no in vivo genotoxicity studies conducted on this substance.
- Available non-GLP studies:
Also no additional non-GLP studies available
- Historical human/control data:
not available
- (Q)SAR:
Not relevant. Generally QSARs will show positive results based on available positive results in Ames test commonly observed for peroxyesters, or even positive results on the bases of being a peroxide.
- In vitro methods:
Are available and show no concerns for genotoxicty/mutagenicty in mammalian cells
- Weight of evidence:
Although there is a marginal positive Ames result, the available data show a lack for genotoxicity in mammalian based cell assays. Peroxyesters are a class of organic peroxides that are relatively unstable under basic or acidic conditions in the presence of water, which catalyzes the cleavage of the peroxyester molecule to form an organic acid and conjugate hydroperoxide. Although the mechanism leading to mutagenicity caused by this chemical class is not clear, acyl peroxides are thought to decompose into free radicals which subsequently react with DNA directly or via formation of reactive oxygen species [Cadet and Wagner]. It is believed that this class of chemicals decompose by homolytic cleavage of the oxygen-oxygen bond and further elimination of carbon dioxide can also occur to generate carboxyl or alkyl free radicals [Walling et al, Gu et al]. Diacyl peroxides give carbon-centered radicals and monoacyl peroxides yield carbon- and oxygen-centered radicals.
However, in vivo the peroxyesters are rapidly converted by peroxidases that catalysts the oxidation of substances and thus prevent radical formation. Peroxidases act on naturally occurring peroxides (such as hydrogen peroxide) forming an acid, alcohol and water. The peroxyesters are expected to be oxidized by naturally occurring peroxidases, resulting in the cleavage of the O-O bond. The expected metabolic products are fatty acid and fatty alcohol. Consequently, although positive results are commonly obtained for peroxyesters in the Ames test, their possible genotoxic potential is in vivo not expressed.

- Grouping and read-across:
Marginal positive results in Ames tests are often observed among the group of monoacyl peroxides (peroxyesters), but in overall evaluation no classification was found to be required. Within the group of peroxyesters several in vivo genotoxicity study data are available evaluating cytogenicity, but only very few address mutagenicity. For a comparable peroxide, tert-butyl peroxy-2-ethylhexanoate (tert-butyl peroctoate, TBPEH), CAS 3006-82-4 a TGR study was located indicating negative results. (ECHA website: https://echa.europa.eu/en/registration-dossier/-/registered-dossier/14582/7/7/3/?documentUUID=23e19cb9-ca75-4056-9054-a393f38dd8c2)

- Substance-tailored exposure driven testing [if applicable]:
Use only involves the industrial use of organic peroxides as polymerization initiators, crosslinking agents or curing agents. Exposures are expected to be minimally to none. After use the peroxide will be completely reacted away.
- Approaches in addition to above [if applicable]:
none
- Other reasons [if applicable]:
Although there is a marginal positive Ames result, the available data show a lack for genotoxicity in mammalian based cell assays. Although applicant is of the opinion that in view of the lack of concerns for genotoxicity no further in vivo studies are indicated, a study proposal was entered as result to failure of dossier acceptance from lack of in vivo results in combination of the positive Ames study.

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:
-Waiving of the in vivo study was not accepted and a study needed to fulfil this REACH requirement

FURTHER INFORMATION ON TESTING PROPOSAL IN ADDITION TO INFORMATION PROVIDED IN THE MATERIALS AND METHODS SECTION:
- Details on study design / methodology proposed:
If ECHA concludes that the study should be performed, it is the intention to perform an in vivo mammalian alkaline comet assay according to OECD 489, in rats, oral route, on the following tissues: liver, glandular stomach and duodenum.

Materials and methods

Test guideline

Guideline:

OECD Guideline 489 (In vivo Mammalian Alkaline Comet Assay)

Version / remarks:

In rats, oral route, on the following tissues: liver, glandular stomach and duodenum.

Test material

Test material information

Constituent 1

Reference substance name:

1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate

EC Number:

244-894-2

EC Name:

1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate

Cas Number:

22288-43-3

Molecular formula:

C16H32O3

IUPAC Name:

2,4,4-trimethylpentan-2-yl 2-ethylhexaneperoxoate

Results and discussion

Any other information on results incl. tables

QSAR PREDICTIONS on the genotoxic potential of CAS 22288-43-3

Summary:

Five QSAR softwares were used to evaluate the potential genotoxicity of 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate (CAS # 22288-43-3).

In general, the predictions for Ames test are consistently negative. The OECD QSAR Toolbox suggests that a mechanistic basis for mutagenicity (mammalian and bacterial) is lacking.

QSAR predictions on carcinogenicity are also provided, as ultimately, this endpoint is of interest. This is a more complex endpoint the weight of the evidence suggest a negative outcome.

 

Kim Doornebosch

Toxicologist, AkzoNobel Specialty Chemicals

March 6, 2018

CAS	22288-43-3
EC name	1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate
Molecular weight	272.4
SMILES	CCCCC(CC)C(=O)OOC(C)(C)CC(C)(C)C
Molecular formula	C16H32O3
Structure
QSAR profile OECD Toolbox
Carcinogenicity (genotox & nongenotox) alerts by ISS	No alert found
DNA alerts by AMES by OASIS v. 1.4	No alert found
DNA alerts by CA and MNT by OASIS v. 1.1	No alert found
In vitro mutagenicity (Ames Test) alerts by ISS	No alert found
In vivo mutagenicity (micronucleus) alerts by ISS	H-acceptor-path3-H-acceptor.A potential Hydrogen bond acceptor.
Protein binding alerts for chromosomal aberration by OASIS v. 1.2	No alert found
QSAR profile ACD/Tox Suite
Ames test	Probability of positive Ames test = 0.040 Reliability: Borderline (Reliability Index= 0.5)
Genotoxicity hazards	No hazardous fragments have been bound
TOPKAT
Weight of Evidence Rodent carcinogenicity	Non-carcinogen
Ames mutagenicity	Non-mutagen
DEREK NEXUS
Mutagenicity in vitro	Bacterium – inactive.Contains misclassified features, slightly lower confidence
Carcinogenicitybacterium	Impossible. Alert: oxidising agent.
Carcinogenicitymammal	Plausible. Alert: oxidising agent.
VEGA
Mutagenicity (Ames test)CONSENSUSmodel (v. 1.0.2) [Based on 4 separate models]	Non-mutagenic
Carcinogenicity model (ISS) (v. 1.0.2)	Carcinogen (low reliability)
Carcinogenicity model (IRFMN/Antares) (v. 1.0.0)	Non-Carcinogen (low reliability)
Carcinogenicity model (IRFMN/ISSCAN-CGX) (v. 1.0.0)	Non-Carcinogen (low reliability)
Carcinogenicity model (CAESAR) (v. 2.1.9)	Non-Carcinogen (low reliability)