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Description of key information

A DEREK assessment, DPRA assay and KeratinoSensTMassay were performed in accordance withSection 8.3 of Annex VII of Regulation (EC) No 1907/2006 as amended in Commission Regulation (EU) 2016/1688 of 20 September 2016 andthe strategy presented in ECHA Guidance on information requirements and chemical safety assessment Chapter R.7a. The studies were performed with substance analogue Delta octalactone, the rationale to read across the data are attached in Section 13.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation, other
Remarks:
In silico assessment
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The rationale to read across the data is attached in Section 13.
Reason / purpose:
read-across source
Key result
Parameter:
other: Prediction on skin sensitization
Run / experiment:
Delta Octalactone
Remarks on result:
no indication of skin sensitisation
Other effects / acceptance of results:
Delta Octalactone does not contain any unclassified or misclassified features and is consequently predicted to be a non-sensitizer.
Interpretation of results:
study cannot be used for classification
Remarks:
(study is part of a weight of evidence approach and is not used for classification on its own)
Conclusions:
DEREK NEXUS version 6.0.1 did not yield any alerts for skin sensitization for the test item. Additionally, Delta Octalactone does not contain any unclassified or misclassified features and is consequently predicted to be a non-sensitizer. As Delta nonalactone has shared chemical structures, the result applies to Delta nonalactone as well.
Endpoint:
skin sensitisation: in chemico
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The rationale to read across the data is attached in Section 13.
Reason / purpose:
read-across source
Key result
Parameter:
other: Mean SPCC depletion(%)
Run / experiment:
Cysteine Reactivity Assay
Value:
1.2
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Remarks:
CV between reference controls: 0.8%
Positive controls validity:
valid
Remarks:
Mean percentage SPCC: 74.0% ± 0.2%.
Remarks on result:
other: SD: 0.3%
Key result
Parameter:
other: Mean percentage SPCC:
Run / experiment:
Lysine Reactivity Assay
Value:
2.5
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Remarks:
CV between reference controls: 1.3%
Positive controls validity:
valid
Remarks:
Mean percentage SPCL: 53.2% ± 1.8%.
Remarks on result:
other: SD: 0.7%
Other effects / acceptance of results:
All acceptability criteria were met and therefore the DPRA was considered to be valid.
See Table 2 & 3 "any other information on results incl. tables" for acceptibility criteria.

Table 2: Acceptability of the Direct Peptide Reactivity Assay (DPRA)

 

Cysteine reactivity assay 

Lysine reactivity assay

Acceptability criteria

Results for

SPCC

Acceptability criteria

Results for

SPCL

Correlation coefficient (r2) standard calibration curve 

>0.99

0.996

>0.99

0.997

Mean peptide concentration RC-A samples (mM)

0.50 ± 0.05 

0.508 ± 0.006

0.50 ± 0.05

0.498 ± 0.007

Mean peptide concentration RC-C samples (mM)

0.50 ± 0.05

0.505 ± 0.005

0.50 ± 0.05

0.498 ± 0.004

CV (%) for RC samples B and C

<15.0

0.8

<15.0

1.3

Mean peptide depletion cinnamic aldehyde (%)

60.8-100

74.0

40.2-69.0

53.2

SD of peptide depletion cinnamic aldehyde (%)

<14.9

0.2

<11.6

1.8

SD of peptide depletion for the test item (%)

<14.9

0.3

<11.6

0.7

RC = Reference Control; CV = Coefficient of Variation; SD = Standard Deviation.

Table 3: SPCC and SPCL Depletion, DPRA Prediction and Reactivity Classification for the Test Item

Test item 

SPCC depletion 

SPCL depletion

Mean of

SPCC and

SPCL

depletion

DPRA prediction and reactivity classification

Mean

± SD

Mean

± SD

Cysteine 1:10 / Lysine 1:50 prediction model

Tetrahydro6propyl-2Hpyran-2-one

(delta octalactone)

1.2%

±0.3%

2.5%

±0.7%

1.9%

Negative: No or minimal reactivity

SD = Standard Deviation.

Interpretation of results:
other: Study cannot be used for classification independently, but in a WoE for the end point Skin Sensitisation
Conclusions:
Delta octalactone was negative in the DPRA and was classified in the “no or minimal reactivity class” when using the Cysteine 1:10 / Lysine 1:50 prediction model. This result is read across to Delta nonalactone.
Endpoint:
skin sensitisation: in vitro
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The rationale to read across the data is attached in Section 13.
Reason / purpose:
read-across source
Positive control results:
The EC1.5 of the positive control was between 26 and 125 μM (59 μM and 46 μM in experiment 1 and 2, respectively). A dose related response was observed and the induction at 250 μM was higher than 2-fold (3.98-fold and 4.59-fold in experiment 1 and 2, respectively).
Key result
Parameter:
other: Imax
Run / experiment:
1
Value:
1.17
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Parameter:
other: Imax
Run / experiment:
2
Value:
1.12
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Other effects / acceptance of results:
- In both experiments, no precipitation was observed at the start and end of the incubation period in the 96-well plates.
- In both experiments, the test item showed no toxicity. The viability of the cells was higher than 70% at all test concentrations and therefore no IC30 and IC50 values could be calculated.
- No luminescence activity induction compared to the vehicle control was observed at any of the test concentrations after treatment with the test item in both experiments. The Imax were 1.17 and 1.12 in experiment 1 and experiment 2, respectively. From these Imax values, no EC1.5 could be calculated.


Both experiments passed the acceptance criteria:
- The luciferase activity induction obtained with the positive control, Ethylene dimethacrylate glycol, was above the threshold of 1.5-fold in at least one concentration.
- The EC1.5 of the positive control was between 5 and 125 μM (26 μM and 46 μM in experiment 1 and 2, respectively). A dose related response was observed and the induction at 250 μM was higher than 2-fold (3.98-fold and 4.59-fold in experiment 1 and 2, respectively).
- Finally, the average coefficient of variation of the luminescence reading for the negative (solvent) control DMSO was below 20% (12% and 10% in experiment 1 and 2, respectively).

Table 1 Overview Luminescence Induction and Cell Viability of the test item in Experiment 1 and 2

Concentration (µM)

0.98

2.0

3.9

7.8

16

31

63

125

250

500

1000

2000

Exp 1 luminescence

1.13

1.00

1.06

1.14

1.17

1.14

1.12

1.15

1.09

0.95

0.90

0.80

Exp 1 viability (%)

98.9

106.6

99.5

96.6

98.2

91.1

93.2

89.3

95.2

101.8

103.7

95.7

Exp 2 luminescence

1.09

0.83

1.00

1.08

1.10

1.12

1.12

1.11

1.02

1.03

1.06

0.88

Exp 2 viability (%)

115.4

122.4

99.8

102.3

100.6

97.8

95.8

95.1

96.7

98.3

97.9

102.5

Table 2 Overview Luminescence Induction and Cell Viability Positive Control EDMG in Experiment 1 and 2

Concentration (µM)

7.8

16

31

63

125

250

Exp 1 luminescence

1.22

1.28

1.60***

1.86***

2.67***

3.98***

Exp 1 viability (%)

98.7

94.7

107.5

110.8

110.9

106.5

Exp 2 luminescence

1.03

1.13

1.31

1.72***

2.32***

4.59***

Exp 2 viability (%)

105.6

109.2

106.2

107.2

107.1

69.7

***p<0.001 Student’s t test

Table 3 Overview EC1.5, Imax, IC30 and IC50 Values

 

EC1.5(µM)

Imax

IC30(µM)

IC50(µM)

Test item Experiment 1

NA

1.17

NA

NA

Test item Experiment 2

NA

1.12

NA

NA

Pos Control Experiment 1

26

3.98

NA

NA

Pos Control Experiment 2

46

4.59

NA

NA

NA = Not applicable

Interpretation of results:
study cannot be used for classification
Remarks:
This study is part of a weight of evidence approach on which the classification is based.
Conclusions:
The test item showed no toxicity (no IC30 and IC50 value) and no biologically relevant induction of the luciferase activity (no EC1.5 value) was measured at any of the test concentrations two independent experiments. The maximum luciferase activity induction (Imax) was 1.17-fold and 1.12-fold in experiment 1 and 2 respectively. The test item is classified as negative in the KeratinoSens(TM) assay since negative results (<1.5-fold induction) were observed at test concentrations up to 2000 μM.
Based on the outcome of this KeratinoSens™ assay performed according to OECD guideline and GLP principles, Tetrahydro-6propyl-2H-pyran-2-one (delta octalactone) is classified as negative (no activation of the antioxidant/electrophile responsive element (ARE)-dependent pathway in keratinocytes) under the experimental conditions described in this report. This result is read across to Delta nonalactone.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

For skin sensitization, substance analogue Delta octalactone was tested. The conclusion on this endpoint was drawn following a weight-of-evidence approach:

1.    DEREK NEXUS version 6.0.1 did not yield any alerts for skin sensitization for Delta octalactone. It is of note that the substance does not contain any unclassified or misclassified features and is consequently predicted to be a non-sensitizer.

2.    Delta octalactone was negative in the DPRA and was classified in the “no or minimal reactivity class” when using the Cysteine 1:10 / Lysine 1:50 prediction model.  

3.    Delta octalactone was classified as negative in a KeratinoSens™ assay (no activation of the antioxidant/electrophile responsive element (ARE)-dependent pathway in keratinocytes).

Based on this data-set it is concluded that there are no indications that Delta octalactone has skin sensitizing properties. This result is read across to Delta nonalactone.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

The available data are considered sufficient to conclude that Delta nonalactone does not have to be classified for skin sensitizing properties according to Regulation 1272/2008 and amendments.