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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2021
Report date:
2021

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Version / remarks:
17.07.92
Deviations:
no
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The LLNA gave questionable results. Thus, a GPMT was performed to clarify the LLNA results. This GPMT together with the additionally performed cLLNA confirm that the LLNA is not a suitable testsystem for this chemical.

Test material

Constituent 1
Chemical structure
Reference substance name:
Constituent C25H31N | Nonyl (branched) substituted - N-Phenyl-1-naphthylamine
Molecular formula:
C25H31N
IUPAC Name:
Constituent C25H31N | Nonyl (branched) substituted - N-Phenyl-1-naphthylamine
Constituent 2
Chemical structure
Reference substance name:
Constituents C34H49N | Di-nonyl (branched)- substituted N-Phenyl-1-naphthylamine
Molecular formula:
C34H49N
IUPAC Name:
Constituents C34H49N | Di-nonyl (branched)- substituted N-Phenyl-1-naphthylamine
Test material form:
liquid
Details on test material:
Name of test item: XPDL 958
Test item No.: 20/0205-1
Batch identification: 0021851006
CAS No.: 63451-49-0
Purity: 100% UVCB *; additionally, an analytical characterization was conducted (No. 20L00034).
Homogeneity: The test item was homogeneous by visual inspection.
Storage stability: The stability of the test item under storage conditions over the study period was guaranteed by the sponsor, and the sponsor holds this responsibility.
Expiry date: November 18, 2021
Storage conditions: Room temperature
Physical state / color: Liquid, viscous/ brown to red

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
not specified
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Envigo RMS GmbH
- Weight at study initiation: 300-340 g
- Housing: 2 to 3 animals per page
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20+-3 °C
- Humidity (%): 30-70 %
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (non-LLNA)

Induction
Route:
intradermal and epicutaneous
Vehicle:
other: liquid paraffin
Concentration / amount:
intradermally: 5 %
dermal: 100 %
Day(s)/duration:
intradermally: once; dermally: day 7 to day 9
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Challengeopen allclose all
No.:
#1
Route:
epicutaneous, semiocclusive
Vehicle:
unchanged (no vehicle)
Concentration / amount:
100 % 1st test
Day(s)/duration:
day 21 to day 22
Adequacy of challenge:
other: not adequte as 80 % of control animals showed irritation
No.:
#2
Route:
epicutaneous, semiocclusive
Vehicle:
other: liquid paraffin
Concentration / amount:
75 % 1st test (re-challenge)
Day(s)/duration:
day 28 to day 29
Adequacy of challenge:
other: irritation in 20 % of the animals
No.:
#3
Route:
epicutaneous, semiocclusive
Vehicle:
other: liquid paraffin
Concentration / amount:
75 % 2nd test
Day(s)/duration:
day 22 to day 23
Adequacy of challenge:
highest non-irritant concentration
No. of animals per dose:
10
Details on study design:
Intradermal pre-test

The intradermal pre-test was accomplished with one test concentration in 2 guinea pigs as subsequently described. Generally, the intradermal pre-test served for concentration deter-mination of the test item to be applied in the main test. Therefore, a concentration for intradermal induction had to be determined without causing skin necrosis 24 and 48 hours post applicationem.

Day -1 – shave
Shave of two animals in the scapular region (approx. 4 x 6 cm) within an electric hair trimmer and razor
Day 0 – application
Intradermal injection of 0.1 mL each in pairs and three rows in the scapular region (approx. 2 x 4 cm) of two animals each according to the scheme in Table 3
Arrangement of injection pairs during the intradermal pre-test.
Position Injection pair Composition of injection solution
cranial 1 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %
central 2 Test item in the vehicle in the selected concentration
caudal 3 Test item in the selected concentration in a 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %

Day 1 and 2 – observation of injection sites
Observation of intradermal injection sites 24 and 48 hours post applicationem; assessment of results according to chapter 9.3.4. (Table 5)

Dermal pre-test

The dermal pre-test was accomplished with 3 guinea pigs as subsequently described. Generally, the 3 animals were treated with adjuvant (FCA) 3 to 4 weeks before conduction of the dermal pre-test. Therefore, animals were shaved in the scapular region and pairwise injected in two rows of 4 intradermal injections of 0.1 mL of adjuvant. The dermal pre-test served for concentration determination of the test item to be applied in the main test. For that, the minimal irritating concentration for dermal induction and the maximal non-irritating concentration for challenge have to be determined.

Day -29 or -22 – shave
Shave of three animals in the scapular region (approx. 4 x 6 cm) with an electric hair trimmer as well as razor
Day -28 or -21 – intradermal injection of FCA
Intradermal injections of 0.1 mL each of 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 % in pairs and two rows in the scapular region (approx. 2 x 2 cm) of three animals
Day -1 – shave
Shave of three animals on both sides (left and right) in the flank regions (cranial and caudal) with an electric hair trimmer and razor
Day 0 – topical application in the flank region
Loading (approx. 0.5 g or 0.5 mL per patch) of four patches (made of multi-layered gauze, 2 x 2 cm) with the test item in the selected concentration and application of these patches on the flanks of animals in a sequence which begins with the highest concentration on the cranial flank of the left side and ends with the lowest concentration on the caudal flank of the right side
Occlusive covering of the patches with impermeable adhesive tape (Blenderm®)
Fixation of patches with Micropor® or Gothaplast® adhesive tape (width 5 cm) by wrapping the trunk of animals
24-hour exposure time
Day 1 – removal of patch and skin cleansing
Removal of the bandage and patches after 24-hour exposure time; cleansing of skin lonely with water and mild soap (e.g. Baktolin®; company Bode Chemie) was not possible due to partial stickiness and viscosity of TI preparation; but residues of glue from the tape and test item could be removed carefully with 1:1-mixture of PEG (polyethylene glycol) and water
Day 2 and 3 – observation of injection sites
Observation of dermal application sites 24 and 48 hours post applicationem; assess¬ment of the results according to chapter 9.3.4. (Table 5)

Main test with induction and challenge as well as re-challenge

Day -1 – shave
Shave of the scapular region (approx. 4 x 6 cm) with an electric hair trimmer and razor
Day 0 – intradermal induction
Group-specific setting of three pairs of intradermal injections (dose volume 0.1 mL) in the prepared test field of the scapular region (Table 4)

Group-specific arrangement of the injection pairs during the intradermal induction phase.
TEST GROUP
Position Injection pair Composition of injection solution
cranial 1 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %
central 2 Test item in the vehicle in the selected concentration
caudal 3 Test item in the selected concentration in a 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %
CONTROL GROUP
Position Injection pair Composition of injection solution
cranial 1 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %
central 2 Vehicle
caudal 3 50 % (w/v) preparation of the vehicle in a 1:1-mixture (v/v) of FCA and aqua ad inj. or NaCl 0.9 %

Day 1 and 6 – observation of injection sites
Examination of intradermal injection sites for signs of skin irritations; assess¬ment of the results according to chapter 9.3.4. (Table 5)
Day 6 – treatment with sodium dodecyl sulphate
Elicitation of a mild irritation by using sodium lauryl sulphate in case that the test item is not skin irritant
Shave of the injection sites with an electric hair trimmer
Massage of about 0.5 g sodium lauryl sulphate (10 % in Vaseline) in the skin
Day 7 – dermal induction in scapular region
Shave of scapular region, in case that this was not done already on day 6
Test group:
complete loading (approx. 0.5 g or 0.5 mL) of patch (made of filter paper, 2 x 4 cm) with the test item in the minimal irritant concentration
Control group:
complete loading (0.5 mL) of a patch (made of filter paper, 2 x 4 cm) with the vehicle
Application of this patch on the shaved skin
Occlusive covering of the patch with impermeable adhesive tape (Blenderm®)
Fixation of the patch with Micropor® or Gothaplast® adhesive tape (width 5 cm) by wrapping the trunks of the animals
48-hour exposure time
Day 9 – removal of the patch and observation of the application site
Removal of the bandage and patch after the 48-hour exposure time
Examination of the application sites with regard to signs of skin irritation; assess¬ment of the results according to chapter 9.3.4. (Table 5)
Day 20 – shave
Shave of the posterior flanks on both sides (approx. 4 x 4 cm) with an electric hair trimmer and razor
Day 21 – topical challenge application in the flank region
Loading (approx. 0.5 g or 0.5 mL) of a patch (made of multi-layered gauze, 2 x 2 cm) with the test item in the maximal non-irritant concentration and application of this patch on the posterior right flank of the animals of the test and control group
Loading (0.5 mL) of a patch (made of multi-layered gauze, 2 x 2 cm) with the vehicle and application of this patch on the posterior left flank of the animals of the test and control group;
Application of the vehicle can be omitted, if the vehicle is water
Occlusive covering of both patches with impermeable adhesive tape (Blenderm®)
Fixation of both patches with Micorpor® or Gothaplast® adhesive tape (width 5 cm) by wrapping the trunk of the animals
24-hour exposure time
Day 22 – removal of patch and skin cleansing
Removal of the bandage and patch after the 24-hour exposure time and cleansing of the skin with water under addition of mild soap (e.g. Baktolin®, company Bode Chemie); possible residues of glue from the tape can be removed from the skin with a 1:1-mixture of PEG and water
Day 23 – preparing of the treated areas
Shave of the posterior flank regions with an electric hair trimmer at least 3 hours before the reading of skin reactions
Cleansing of skin areas, if necessary, in order to facilitate the assessment
Day 23 and 24 – observation of skin reactions
Examination of each skin area 24 and 48 hours after the termination of the challenge application and assessment of skin reactions according to chapter 9.3.4. (Table 5)
Day 27 – shave
Shave of the anterior flanks on both sides (approx. 4 x 4 cm) with an electric hair trimmer and razor
Day 28 – topical re-challenge application in the flank region
Loading (approx. 0.5 g or 0.5 mL) of a patch (made of multi-layered gauze, 2 x 2 cm) with the test item in the chosen concentration and application of this patch on the anterior left flank of the animals of the test and control group
Loading (0.5 mL) of a patch (made of multi-layered gauze, 2 x 2 cm) with the vehicle and application of this patch on the anterior right flank of the animals of the test and control group;
Application of the vehicle can be omitted, if the vehicle is water
Occlusive covering of both patches with impermeable adhesive tape (Blenderm®)
Fixation of both patches with Micorpor® or Gothaplast® adhesive tape (width 5 cm) by wrapping the trunk of the animals
24-hour exposure time
Day 29 – removal of patch and skin cleansing
Removal of the bandage and patch after the 24-hour exposure time and cleansing of the skin with water under addition of mild soap (e.g. Baktolin®, company Bode Chemie); possible residues of glue from the tape can be removed from the skin with a 1:1-mixture of PEG and water
Day 30 – preparing of the treated areas
Shave of the anterior flank regions with an electric hair trimmer at least 3 hours before the reading of skin reactions
Cleansing of skin areas, if necessary, in order to facilitate the assessment
Day 30 and 31 – observation of skin reactions
Examination of each skin area 24 and 48 hours after the termination of the re-challenge application and assessment of skin reactions according to chapter 9.3.4. (Table 5)

Assessment of skin reactions
Skin reactions were assessed according to the grading scale by Magnusson/Kligman (Table 5). In case of difficult or uncertain results, assessment was conducted with a manual inspec-tion lamp having white light and twofold magnification.
 

Grading scale according to Magnusson/Kligman.
Skin reaction Grade
no visible change 0
discrete or patchy erythema 1
moderate and confluent erythema 2
intense erythema and swelling 3






Positive control substance(s):
not required
Remarks:
The last positive control study (Lab. No. 04289) with the reference material α-Hexylcinnam-aldehyde (purity: 85 %) was conducted from March to June 2021. In the test group, 80 % of the guine pigs responded with positive skin reactions to the treatment.

Results and discussion

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
100 % 1st main test
No. with + reactions:
4
Total no. in group:
5
Remarks on result:
not determinable
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
100 % 1st main test
No. with + reactions:
2
Total no. in group:
5
Remarks on result:
not determinable
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
100 % 1st main test
No. with + reactions:
9
Total no. in group:
10
Remarks on result:
not determinable
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
100 % 1st main test
No. with + reactions:
3
Total no. in group:
10
Remarks on result:
not determinable
Reading:
rechallenge
Hours after challenge:
24
Group:
negative control
Dose level:
75 % 1st main test
No. with + reactions:
1
Total no. in group:
5
Remarks on result:
not determinable
Reading:
rechallenge
Hours after challenge:
48
Group:
negative control
Dose level:
75 % 1st main test
No. with + reactions:
1
Total no. in group:
5
Remarks on result:
not determinable
Reading:
rechallenge
Hours after challenge:
24
Group:
test chemical
Dose level:
75 % 1st main test
No. with + reactions:
5
Total no. in group:
10
Remarks on result:
not determinable
Reading:
rechallenge
Hours after challenge:
48
Group:
test chemical
Dose level:
75 % 1st main test
No. with + reactions:
2
Total no. in group:
10
Remarks on result:
not determinable
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
75 % 2nd main test
No. with + reactions:
0
Total no. in group:
5
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
75 % 2nd main test
No. with + reactions:
0
Total no. in group:
5
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
75 % 2nd main test
No. with + reactions:
2
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
75 % 2nd main test
No. with + reactions:
2
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation

Any other information on results incl. tables

Main tests

Intradermal and dermal induction

On day 0, intradermal induction was conducted according to chapter9.3.3. In the scapular region of the animals, 3 pairwise arranged intradermal injections were applied containing the following preparations:

Control group

Injection (1) -  1:1-mixture (v/v) of FCA and NaCl 0.9 %

Injection (2) -  vehicle liquid paraffin

Injection (3) -  50 % (w/v) preparation of the vehicle liquid paraffin in a 1:1-mixture (v/v) of FCA and NaCl 0.9 %

Test group

Injection (1) -  1:1-mixture (v/v) of FCA and NaCl 0.9 %

Injection (2) -  5 % (w/w) test item in the vehicle liquid paraffin

Injection (3) -  5 % (w/w) test item in a 1:1-mixture (v/v) of FCA and NaCl 0.9 %

On day 7, dermal induction was conducted according to chapter9.3.3. In the scapular region of the animals, a patch was applied loaded with the following preparation for 48 hours:

Control group:       patch with 0.5 mL of the vehicle liquid paraffin

Test group:            patch with 0.5 mL of the 100 % test item

In all animals of the two test groups and two control groups, intradermal injections of the 1:1-mixture of FCA and NaCl 0.9 % (v/v) evoked skin reactions grade 2 at least on day 1post applicationem. The injection sites were necrotic and open/bloody on days 6 and 9.

Skin areas which were treated intradermally with the test item prepared in the vehicle dis­played a discrete or patchy erythema (grade 1) in majority of animals of the two test groups on day 1 post applicationem. A discrete or patchy erythema (grade 1) was also still observed in half of the animals on day 6post applicationem, whereas the other half of animals was already free of reactions (grade 0) on this day. No skin reactions (grade 0) were observed on day 9 post applicationem or assessment of erythema formation was prevented by rusty-red coloration of the TI-treated skin and adjacent hair. Most of the skin areas of the control groups in which the vehicle was inject­ed intra­der­mally displayed a discrete or patchy erythema (grade 1) on day 1 post applicationem.A dis­crete or patchy erythema (grade 1) was also observed on day 6post applica­tionemin 50 % of the control group animals, whereas the majority of control group ani­mals was free of any reactions (grade 0) on day 9 post applicationem.

The intradermal injections with the test item in the adjuvant mixture caused mostly skin reactions of grade 2 (moderate and confluent erythema) in the test group animals on day 1post applicationemas well as bloody/open necrosis on days 6 and 9 post applicationem. Also, the majority of the control group animals displayed a moderate and confluent erythema (grade 2) on day 1post applicationemand necrosis on day 6 post applicationem. Moreover, eschar formation was observed in the control group animals on day 9 post applicationembeside the necrosis.

Challenge

 

On day 21, challenge treatment was performed according to chapter9.3.3., whereby one patch with the test item preparation was applied on the caudal right flank and one patch with the vehicle liquid paraffin was applied on the caudal left flank of all animals of the test groups and the control groups for 24 hours.

The difference between the challenge treatments in the 1stand 2ndmain tests was the TI concentration which was applied. Whereas the undiluted test item was used for the 1stmain test, the TI preparation for the 2ndmain test had a reduced concentration of 75 %w/w.

This alteration was also the reason for differing findings which were observed in 1stand 2ndmain test as responses to the challenge treatments with different concentrations of the test item.

During the 1stmain test, skin reactions ranging between grades 1 and 2 were observed in 80 % (4/5) of the control group animals and in 90 % (9/10) of the test group animals 24 hours after the challenge treatment with the 100 %w/w test item. The incidence of skin reactions decreased to 40 % (2/5) in the control group and to 30 % (3/10) in the test group after 48 hours and also intensity of erythema decreased over time as presented inTable9.

These findings corroborated the suspicion of a mechanical irritation effect concluded from the difficulties to remove the patch and TI residues at the end of the exposure time, because these were stuck intensely to the skin. In spite of soaking the dressing with PEG/water-mixture, the TI-treated skin was reddened and displayed partially micro-in­juries at the end of the challenge treatment.

During the 2ndmain test, 2 of 10 (20 %) test group animals displayed a discrete or patchy ery­thema of grade 1 and scales after the challenge treatment with the 75 %w/w test item, whereas the control group was free of any skin reaction as presented inTable10.

The patch removal at the end of the exposure time was difficult again and required intense and time-consuming soaking of the dressing with soap-water and PEG/water-mixture.

Re-challenge

 

The ambiguous challenge results of the 1stmain test under involvement of a mechanical irritation effect caused by the problematic stickiness of the test item required the conduction of a re-challenge one week later with reduced TI concentration and the same animals of the control group 1 and the test group 1.

On day 28, re-challenge treatment was performed during the 1stmain test according to chapter9.3.3., whereby one patch with the 75 %w/w test item was applied on the cranial left flank and one patch with the vehicle liquid paraffin was applied on the cranial right flank of all animals of the test group 1 and the control group 1 for 24 hours.

Adhesive property of TI preparation complicated again the patch removal at the end of exposure time, but intense soaking of dressings with soap-water and PEG/water mixture allowed finally detachment without obvious micro lesions.

A discrete or patchy erythema (grade 1) was observed in 20 % (1/5) of the control group animals and in 30 % (3/10) of the test group animals after the re-challenge treatment with the 75 %w/w test item. Moreover, 2 of 10 (20 %) test group animals displayed a moderate and confluent erythema of grade 2 after 24 hours which only may be considered as positive skin reaction. A summary of findings is presented inTable11.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
Based on the results of the Guinea Pig Maximization Test (GPMT) described in this Final Report, the test item XPDL 958 shows no skin sensi¬tizing potential under the test conditions chosen.