1-hydroxyoctan-2-one

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in chemico

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

May 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This is a Klimisch 1 OECD 442C guideline study conducted on the registered substance 1-hydroxyoctan-2-one in accordance GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))

GLP compliance:

yes (incl. QA statement)

Type of study:

direct peptide reactivity assay (DPRA)

Justification for non-LLNA method:

OECD TG 442C cites the DPRA model as a validated method for skin sensitisation testing in the context of an integrated approach to testing and assessment.

The DPRA has been evaluated in a European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM)-led validation study and subsequent independent peer review by the EURL ECVAM Scientific Advisory Committee (ESAC) and was considered scientifically valid to be used as part of an Integrated Approach to Testing and Assessment (IATA) to support the discrimination between skin sensitisers and non-sensitisers for the purpose of hazard classification and labelling.

Test material

Test material information

Constituent 1

Reference substance name:

1-hydroxyoctan-2-one

Cas Number:

7019-19-4

Molecular formula:

C8H16O2

IUPAC Name:

1-hydroxyoctan-2-one

Test material form:

liquid

Details on test material:

Batch 1203/16/100

Specific details on test material used for the study:

Batch 1081-67E

In chemico test system

Details on the study design:

The DPRA is proposed to address the molecular initiating event of the skin sensitisation Adverse Outcome Pathway (AOP), namely protein reactivity, by quantifying the reactivity of test and reference items towards model synthetic peptides containing either Lysine or Cysteine. 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.

Test items were incubated for 24hrs (±2hrs) at 25 ±2.5˚C in solution at 100mM in combination with either Cysteine or Lysine containing peptides and then run on an HPLC system (20-minute run-time) using gradient elution and UV detection at 220nm to measure peptide concentration. Test items were compared to reference controls containing the test item solvent in combination with either Cysteine or Lysine peptide in order to determine the relative percent peptide depletion. Relative percent peptide depletion values were used in a prediction model that assigns test items to one of four reactivity classes.

Results and discussion

Positive control results:

Acceptance Criteria

Acceptance criteria for all controls and the test item were met in both runs with the exception of the Standard Curve r2 value and the RefA and RefC mean peptide concentrations for the Cysteine run (highlighted in orange below). However, the Standard Curve (r2=0.975) only narrowly missed the r2 value acceptance criterion and therefore was considered suitable for use. The marginally decreased RefA (0.393mM) and RefC (0.413mM) concentrations were not deemed to have affected the result of the testing as the test item was prepared using the same peptide and solvent and therefore is comparable to the RefC control. In addition, the test item caused little/no Cysteine peptide depletion. These controls were considered acceptable for the purposes of the study based upon the overall result and the performance of all other controls.

Data exclusion

Cysteine peptide RefB4 and RefC2 were excluded in line with guidance in XCellR8 SOP L0096 regarding data exclusion. They were excluded as they were clear outliers that had pushed the Peak Area %CV beyond the acceptance range. After removal of outliers, acceptance criteria for Peak Area %CV were met for both RefB and RefC (11.850 and 6.149 respectively).

In vitro / in chemico

Results

Results 1

Key result

Run / experiment:

other: 1

Parameter:

other: mean % peptide depletion (Cys+Lys)

Value:

8.989

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

other: Sensitiser with Low Reactivity

Results 2

Run / experiment:

other: 1

Parameter:

other: %cysteine peptide depletion

Value:

1.449

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Results 3

Run / experiment:

other: 1

Parameter:

other: % lysine depletion

Value:

16.529

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Any other information on results incl. tables

Name	Test Item ID	% Cysteine Peptide Depletion	% Lysine Peptide Depletion	Mean % Peptide Depletion (Cys + Lys)	DPRA Prediction	DPRA Reactivity Class
EXPINN PC17032	TA1	1.449	16.529	8.989	Sensitiser	Low Reactivity

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

1 -hydroxyoctan-2 -one was classified as a Sensitiser with Low Reactivity as per the prediction model.

Executive summary:

In this study, the skin sensitisation potential of 1 -hydroxyoctan-2 -one was assessed using theIn Chemico Direct Peptide Reactivity Assay (DPRA) method according to OECD Test Guideline 442C. After a 24h incubation with both Cysteine and Lysine containing peptides, the percent peptide depletion was measured by High Performance Liquid Chromatography (HPLC).

 

The test item produced 8.989% mean Cysteine and Lysine peptide depletion, therefore, using the Cysteine 1:10 / Lysine 1:50 prediction model, the test item was classified as a Sensitiser with Low Reactivity. A single HPLC analysis for both the Cysteine and the Lysine peptide was considered sufficient for the test item as the result was unequivocal for each of the peptides individually.Even though the result fell in the region of 3-10% depletion for the Cysteine 1:10 / Lysine 1:50 prediction model when results for both peptides were combined, i.e. close to the threshold (6.38%) use to discriminate between sensitisers and non-sensitisers, it was not considered necessary to repeat the runs due to the nature of the reactivity with each peptide individually. The reasons for this and the results are summarised below:

The result with the Cysteine peptide indicated little to no reactivity of the test item with the peptide across all replicates

The result with the Lysine peptide showed consistent reactivity with the peptide across all replicates with very little variation in the data as evidenced by the standard deviation and %CV values

The final mean % peptide depletion observed using this model was 8.989%. Therefore, 1 -hydroxyoctan-2 -one was classified as a Sensitiser with Low Reactivity as per the prediction model.