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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental start date 04 August 2016 Experimental completion date 06 September 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 442C (In Chemico Skin Sensitisation: Direct Peptide Reactivity Assay (DPRA))
Deviations:
yes
Remarks:
Cysteine prediction model only used due to ion pairing on column interfearing with Lysine results.
GLP compliance:
yes (incl. certificate)
Type of study:
direct peptide binding assay
Justification for non-LLNA method:
The reactivity and sensitization potential of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015).

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Specific details on test material used for the study:
Sponsor’s identification Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine
Alternative name Witconate P-1460
Product name ACAR 16015
Batch No. 2629-89-10
CAS No. 1093628-27-3
Purity 98.6%
Molecular weight 416.5
Appearance Amber paste
Expiry/retest date 03 April 2019
Storage conditions Room temperature in the dark

In vitro test system

Details on study design:
Peptide and Positive Control
Synthetic peptide containing Cysteine
Alternative name: Ac-RFAACAA-OH
Batch number: 1556171
Stated purity: 95% (by HPLC)
Molecular Weight: 751.5 g/mol
Supplier: AnaSpec
Storage conditions: Frozen, -20°C
Expiry/retest date: 5 years.

Synthetic peptide containing Lysine
Alternative name: Ac-RFAAKAA-OH
Batch number: 1556172
Stated purity: 90-95%
Molecular Weight: 776 g/mol
Supplier: AnaSpec
Storage conditions: Frozen, -20°C
Expiry/retest date: 5 years.
Cinnamic Aldehyde (Positive control)
Batch number: MKBR2427V
Stated purity: >95%
Molecular Weight: 132.16 g/mol
Supplier: SAFC
Storage conditions: Room temperature
Expiry/retest date: February 2019

Apparatus
High performance liquid chromatograph (HPLC): Waters Alliance 2695 separation module and 2487 dual wavelength detector
Balances fitted with printers: Capability of weighing to 5 decimal places
General laboratory apparatus and glassware.

Analytical Procedure
Reagents
Acetonitrile (ACN): HPLC gradient grade
Methanol (MeOH): HPLC grade
Trifluoroacetic acid (TFA): 99% Pure
Water: Deionised reverse osmosis
Ammonium Acetate: Analytical reagent
Sodium Phosphate, monobasic: Analytical reagent
Sodium Phosphate, dibasic: Analytical reagent
Ammonium Hydroxide: Analytical reagent
100 mM Phosphate buffer, pH 7.5: In house preparation
100 mM Ammonium Acetate buffer, pH 10.2: In house preparation
HPLC Mobile Phase A: 0.1% v/v TFA in Water, in house preparation
HPLC Mobile Phase B: 0.085% v/v TFA in ACN, in house preparation

Assessment of Test Item Solubility
The solubility of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) in acetonitrile and methanol was assessed at a concentration of 100 mM.

Preparation of Peptide Stock Solutions
Stock solutions of each peptide at concentrations of 0.667 mM were prepared by dissolution of pre-weighed aliquots of the appropriate peptide in ca 20 mL aliquots of the appropriate buffer solution (Cysteine in 100 mM phosphate buffer pH 7.5, Lysine in 100 mM Ammonium acetate buffer pH 10.2).

Preparation of Peptide Calibration Standards
Calibration standards of both peptides were prepared by diluting the requisite stock solution in the appropriate buffer and acetonitrile and contained each peptide at concentrations of 0.0167 mM, 0.0334 mM, 0.0667 mM, 0.133 mM, 0.267 mM and 0.534 mM. A buffer blank was prepared as well.

Preparation of Stability Controls and Precision Controls
Stability controls and precision controls of both peptides were prepared at a concentration of 0.5 mM.

Preparation of Positive Control Solution
The positive control chemical (Cinnamic aldehyde) was prepared at a concentration of 100 mM in both acetonitrile and methanol.

Preparation of Positive Control and Cysteine Peptide Depletion Samples and Co-elution Controls
Methanol solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) and the positive control were diluted with the Cysteine peptide to prepare solutions containing 0.5 mM Cysteine and 5 mM of either Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) or the positive control.

For the co-elution control, buffer solution was used in place of the Cysteine stock solution.

Preparation of Positive Control and Lysine Peptide Depletion Samples and Co elution Controls
Methanol solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) and the positive control were diluted with the Lysine peptide to prepare solutions containing 0.5 mM Lysine and 25 mM of either Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) or the positive control. For the co-elution control, buffer solution was used in place of the Lysine stock solution.

Incubation
The appearance of the Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) and positive control samples in the HPLC vials was documented after preparation and then the vials placed into the autosampler of the HPLC set at 25°C for a minimum of 22 hours incubation prior to initiation of the analysis run. Prior to initiation of the run the appearance of the samples in the vials was assessed and documented again.

Analysis
The concentration of the peptides containing Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) and the associated positive control was quantified by HPLC using UV detection as detailed in the chromatographic section.

Instrumentation Parameters
High performance liquid chromatograph (HPLC): Waters Alliance 2695 separation module and 2487 dual wavelength detector
Column: Agilent Zorbax SB C18, 3.5µm, 100 x 2.1 mm
Guard column: Phenomenex AJO4286
Column temperature: 30°C
Sample temperature: 25°C
Mobile Phase (MP) A: 0.1% TFA in Water
Mobile Phase (MP) B: 0.085% TFA in ACN

Gradient: Time (minutes) MPA(%) MPB (%)

0 90 10
20 75 25
21 10 90
23 10 90
23.5 90 10
30 90 10
Flow rate: 0.35 mL/minute
Stroke volume 25 µL
Detector wavelength: UV, 220 nm
Injection volume: 2 µL (slow draw rate)
Run time: 30 minutes
Approximate retention time (Cysteine) 11 minutes
Approximate retention time (Lysine) 7 minutes

Calculations
The peak area response for the peptide in each calibration chromatogram was measured. Calibration curves were constructed by linear regression of standard response versus standard concentration. The area responses of the peptide peak observed at the characteristic retention time of each peptide in each sample chromatogram was measured. Peptide depletion was determined using the following equation:

% Peptide depletion = 100 - ((Peptide peak area in replicate depletion samples (x 100)) / Mean Peptide peak area of reference control samples B or C)
For clarification, control samples B were used for calculation of positive controls and control samples C were used for calculation of depletion samples.

Major Computerized Systems
Chromatography data handling: Waters Empower
Sample registry system: Envigo
Test substance management: Pristima, Xybion Medical Systems Corporation
Version numbers of the systems are maintained by Envigo.

Results and discussion

Positive control results:
Not applicable

In vitro / in chemico

Results
Key result
Parameter:
other: peptide binding to synthetic peptides
Run / experiment:
Results based on Cysteine assessment model as Lysine peptide results are not due to ion pairing interaction on the HPLC column
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
not applicable
Remarks on result:
no indication of skin sensitisation

Any other information on results incl. tables

Solubility Assessment

The solubility of the Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) in acetonitrile at a nominal concentration of 100 mM was not confirmed, solubility was confirmed in methanol at a nominal concentration of 100 mM.

Reactivity Assessment

The DPRA prediction and the reactivity of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) based on the Cysteine peptide depletion and the individual depletion values in the Cysteine peptide and the Lysine peptide is presented inTable 1. The Lysine peptide result was confirmed to be a false positive due to ion-pairing interactions, with an extra late running peak seen eluting in the chromatogram that when summed with the Lysine peptide peak areathe total peak area matched that of the positive control. As the result generated when using the Lysine containing synthetic peptides was affected by these ion-pairing interactions, the Lysine result has been excluded and only the Cysteine result is used for classification.

All analytical acceptance criteria for each peptide run were met:

 

 

Peptide

Linearity

Positive control depletion (%)

Reference controls

Test item

Acceptance criteria

Cysteine

>0.99

60.8-100
(CV <14.9%)

0.45-0.55 mM
(CV <15%)

CV <14.9%

Lysine

>0.99

40.2-69.0
(CV <11.6%)

0.45-0.55 mM
(CV <15%)

CV<11.6%

Achieved results

Cysteine

>0.999

73.1
(CV, 0.01%, n=3)

B: 0.511 mM (CV 0.61%, n=6)

C: 0.507 mM (CV 0.67%, n=3)

CV 0.27%

Lysine

>0.999

58.0
(CV, 4.31%, n=3)

B: 0.511 mM (CV 1.33%, n=6)

C: 0.509 mM (CV 0.84%, n=3)

CV 3.32%

CV         Coefficient of Variation

The depletion of peptide in the presence of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) was:

 

Mean peak area of reference controls(µV.sec)

Mean peak area of test item(µV.sec)

Mean Depletion (%)

Cysteine

Control B (ACN): 867260 (n=6)

Control C (MeOH): 861110 (n=6)

856140 (n=3)

0.577

Lysine

Control B (ACN): 745970 (n=6)

Control C (MeOH): 743560 (n=6)

112430 (n=3)

84.91

1       The mean Lysine result has been excluded from calculation due to the false positive result due to ion-pair interactions with the HPLC column.

And applying the following Cysteine 1:10 depletion model (below), reactivity as minimal and the DPRA prediction is negative and Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) is therefore a non skin sensitizer. 

Cysteine (Cys) % depletion

Reactivity Class

DPRA Prediction

0%≤ Cys% depletion ≤13.89%

No or minimal reactivity

Negative

13.89%< Cys % depletion ≤23.09%

Low reactivity

Positive

23.09%< Cys % depletion ≤98.24%

Moderate reactivity

98.24%< Cys % depletion ≤100%

High reactivity

 

No co-elution occurred in either assay.  

Overall Achieved Depletion Values

Test item

Cysteine peptide depletion (%)

Lysine peptide depletion (%)

Cysteine peptide depletion (%)

Reactivity class

DPRA prediction

Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015)

0.577

84.91

0.577

No or minimal

Negative

1             The mean Lysine result has been excluded from calculation due to the false positive result due to ion-pair interactions with the HPLC column.

 

 Individual Achieved Depletion Values

 Cysteine Peptide Depletion

Sample

Peak area (µV.sec)

Peptide concentration1(µg/mL)

Peptide Depletion (%)

Mean Depletion (%)

CV (%)

Positive control

233643

103.67

73.12

73.1

0.01

233670

103.68

73.12

233683

103.69

73.12

Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015)

857223

379.43

0.4513

0.577

0.27

853515

377.79

0.8823

857671

379.63

0.3393

CV      Coefficient of variation

1                Samples prepared at a concentration of 376 µg/mL (0.5 mM)

2                Calculated against a mean control peak area of 867260 µV.sec(Control B, n=6)

3          Calculated against a mean control peak area of 861110 µV.sec(Control C, n=3)

 Lysine Peptide Depletion

Sample

Peak area (µV.sec)

Peptide concentration1(µg/mL)

Peptide Depletion(%)

Mean Depletion (%)

CV (%)

Positive control

300390

159.62

59.72

58.0

4.31

327364

173.97

56.12

312596

166.11

58.12

Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015)

109938

58.330

85.23

84.9

3.32

110630

58.698

85.13

116726

61.940

84.33

CV      Coefficient of variation

1                Samples prepared at a concentration of 388 µg/mL (0.5 mM)

2          Calculated against a mean control peak area of 745970 µV.sec(Control B, n=6)

3          Calculated against a mean control peak area of 743560 µV.sec(Control C, n=3)

 

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
Solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) were successfully analyzed by the validated DPRA analytical method (Envigo analytical method FIA/M101/15) in Cysteine containing synthetic peptides. Solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) analyzed by the validated method in Lysine containing synthetic peptides appeared to show the test item to be a strong skin sensitizer. This was investigated further and was confirmed to be a false positive due to ion-pairing effects between the test item and the HPLC column, as a result the Lysine result has been excluded and only the Cysteine result is reported
The Cysteine result places Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) in the reactivity class of “no or minimal reactivity” and therefore it is predicted to be a non skin sensitizer.
Executive summary:

This purpose of this study (based on the OECD guideline for the testing of chemicals,In chemicoSkin Sensitisation: Direct Peptide Reactivity Assay (DPRA), OECD/OCDE document TG 442C) was to assess the reactivity and sensitizing potential of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015). 

Solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) were successfully analyzed by the validated DPRA analytical method (Envigo analytical method FIA/M101/15) in Cysteine containing synthetic peptides.

Solutions of Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) analyzed by the validated method in Lysine containing synthetic peptides appeared to show the test item to be a strong skin sensitizer. This was considered to be a false positive due to the presence of an extra peak in the chromatogram eluting at approximately 13 minutes, when the peak areas of the Lysine peptide peak and this extra peak were summed, the total peak area matched that of the positive controls in the Lysine assay. It was considered that this could be the result of ion-pairing interactions with the HPLC column used in the validated method. An investigation confirmed the false positive result was due to ion-pairing effects between the test item and the HPLC column used in the validated method. As the result generated when using the Lysine containing synthetic peptides was affected by these ion-pairing interactions, the Lysine result has been excluded and only the Cysteine result is used for classification.

The Cysteine result places Benzenesulfonic acid, mono-C10-13-alkyl derivs., compds. with N1,N1-dimethyl-1,3-propanediamine (ACAR 16015) in the reactivity class of “no or minimal reactivity” and therefore it is predicted to be a non skin sensitizer.