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Description of key information

Key value for chemical safety assessment

Skin sensitisation

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Endpoint:
skin sensitisation: in chemico
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
GLP compliance:
no
Remarks:
GLP equivalent
Type of study:
direct peptide binding assay
Details on study design:
The Direct peptide reactivity Assay (DPRA) is an in chemico test to determine the reactivity of test a
substance towards peptides.
This assay has been validated for a broad range of low-molecular weight chemicals and it was found
to detect reactive skin sensitizers from a broad range of so called applicability domains, i.e.
chemicals reacting with proteins by different mechanisms. It was validated by ECVAM and proposed
to be used as part of an integrated approach for testing and assessment (IATA).

The test substance was dissolved in acetonitrile and mixed with a Cysteine- and a
Lysine-containing peptide according to the standard operating procedure of the DPRA. One study
with three replicates was conducted. After 24 h incubation time, peptide depletion induced by was determined by HPLC-UV.
Key result
Parameter:
other: Average depletion Cys-and Lys-peptide
Value:
14.6
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
The result of the DPRA assay should be used as part of an integrated approach for testing and
assessment (IATA). A parallel test in the KeratinoSens™ assay may indicate whether congruent
results are obtained by both test methods. According to a detailed analysis on large set of
chemicals, two congruent results in these two tests give a good prediction of the sensitizer hazard
[3-5] particularly when predicting human data, while an additional test in a dendritic cell line
assessing expression of surface markers may be needed in case of discordant results.
GR-86-6599 was reactive with the Cys-peptide (27.8% depletion) and classified into the LOW
reactivity class according to the prediction model. It is therefore considered a sensitizer according to
the prediction model of the DPRA. Additional analysis with LC-MS indicated that it indeed formed a
covalent adduct with the test peptide.
Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 442D (In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method)
GLP compliance:
no
Remarks:
GLP equivalence
Type of study:
activation of keratinocytes
Details on study design:
The KeratinoSensTM assay is a cell-based assay with a reporter cell line to detect potential skin
sensitizers by their ability to induce the Nrf2-response.
This assay has been validated for a broad range of low-molecular weight chemicals and it was found
to respond to skin sensitizers from a broad range of so called applicability domains, i.e. chemicals
reacting with proteins by different mechanisms. It was validated by ECVAM and proposed to be
used as part of an integrated approach for testing and assessment (IATA).

The test substance was dissolved in DMSO and tested according to the standard
operating procedure of the KeratinoSensTM assay at 12 concentrations in three repetitions, each
time in three replicates. After 48 h incubation time, luciferase induction and cellular viability at each
of the concentrations were determined.
Positive control results:
Cinnamic aldehyde was run in all three repetitions. Here the detailed results for this positive control
are reported in Table 8 and Figure 5. Cinnamic aldehyde needs to be positive for a run to be
accepted (i.e. induction > 1.5 fold). This was the case in all three repetitions. The induction at 64 μM
and the EC 1.5 for cinnamic aldehyde were also calculated. The targets are: (i) Average induction in
the three replicates for cinnamic aldehyde at 64 μM should be between 2 and 8, and (ii) the EC 1.5
value should be between 7 μM and 30 μM. At least one of these two numerical criteria must be met
in order to accept a repetition. In the experiments performed here both criteria were fulfilled in all
three repetitions. Thus all three repetitions were valid for the positive control.
Key result
Parameter:
other: Average IMAX (fold induction)
Run / experiment:
1
Value:
1.87
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
The result of the KeratinoSens™ assay should be used as part of an integrated approach for testing
and assessment (IATA)[9]. A parallel test in the DPRA may indicate whether congruent results are
obtained by both test methods. According to a detailed analysis on large set of substances, two
congruent results in these two tests give a good prediction of the sensitizer hazard [5, 7, 18], in
particular when comparing against human data, while an additional test in a dendritic cell line
assessing expression of surface markers may be needed in case of discordant results.
In all three repetitions, induction of the luciferase above the threshold of 1.5 was noted, in two of
them at non-cytotoxic concentrations. According to the prediction model of the KeratinoSens™
assay, the test substance is rated as a sensitizer. This conclusion is also supported by the analysis
of the dose-response curve in Figure 4 with overall dose-dependent induction of the luciferase
reporter gene just below the cytotoxic concentration to be observed
Executive summary:

GR-86-6599-43 is strongly toxic to the KeratinoSens™ cells. In all three repetitions, it did induce the

luciferase gene above a threshold of 1.5 at 8 μM and in two occasions this induction occurred at a

non-toxic dose. It is therefore considered a skin sensitizer according to the prediction model of the

KeratinoSens™ assay.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)

Justification for classification or non-classification

Sensitising based on positive responses in 2 in vitro assays (Keratinosens and Peptide binding assay).