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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 16 June 2020 to 04 November 2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The study was being performed with vertebrate animals because the chemical nature of the test item was not compatible with the available in vitro alternative tests. The in vitro testing was considered not to be technically feasible.
Indeed, with Commission Regulation (EU) 2016/1688 adopted on the 20th September 2016, the testing strategy for the assessment of the skin sensitisation potential of a new substance now includes mandatory in vitro testing before any in vivo testing can be carried out, if the in vitro tests are technically feasible. This applies to all substances to be tested for EU REACH and CLP, but not for other regulatory purposes.
Before the start of this in vivo study, the Sponsor confirmed that existing data was not sufficient for the labelling or for the specific regulatory purpose for skin sensitisation.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2020
Report date:
2020

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
22 July 2010
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)

Test material

1
Reference substance name:
Nickel Cobalt Manganese Hydroxide
Cas Number:
189139-63-7
Molecular formula:
Molecular formula: Ni1-x-yMnxCoy(OH)2, Stoechiometry of (Me = Ni + Co + Mn) equals 1, ranges of the elements approx. as: Ni/Me = 0.25 – 0.95 Mn/Me = 0.02 – 0.40 Co/Me = 0.02 – 0.40 OH = 2.00
IUPAC Name:
Nickel Cobalt Manganese Hydroxide
Constituent 1
Chemical structure
Reference substance name:
Manganese dihydroxide
Cas Number:
18933-05-6
Molecular formula:
Mn(OH)2
IUPAC Name:
Manganese dihydroxide
Constituent 2
Chemical structure
Reference substance name:
Cobalt dihydroxide
EC Number:
244-166-4
EC Name:
Cobalt dihydroxide
Cas Number:
21041-93-0
Molecular formula:
CoH2O2
IUPAC Name:
cobalt(2+) dihydroxide
Constituent 3
Chemical structure
Reference substance name:
Nickel dihydroxide
EC Number:
235-008-5
EC Name:
Nickel dihydroxide
Cas Number:
12054-48-7
Molecular formula:
H2NiO2
IUPAC Name:
nickel(2+) dihydroxide
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
Batch/Lot number: PVX-089 PVX 14
Description: Dark Grey Powder
Purity: 100% (6.31% Co ; 5.96% Mn ; 50.87% Ni)
Manufacturer: Umicore
Expiry date: 30 April 2021
Storage conditions: Controlled room temperature (15-25 °C, ≤70% relative humidity). Protected from light and humidity (store in a tightly closed container).
The Certificate of Analysis is attached in Appendix 1 of the study report.

In vivo test system

Test animals

Species:
mouse
Strain:
CBA/Ca
Remarks:
CBA/CaOlaHsd mice On the basis of OECD Guideline, mice of CBA/Ca or CBA/J strains can be used. Females were used because the existing database is predominantly based on females.
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Envigo
RMS B.V. Postbus 553 5800 AN Venray Netherland
- Females (if applicable) nulliparous and non-pregnant: yes
- Microbiological status of animals, when known: SPF at arrival; standard housing conditions during the study. The health status of the animals assigned to study were verified by the clinical Veterinarian.
- Age at study initiation:Young adults, 10 weeks old (age-matched, within one week)
- Weight at study initiation: 19.8 – 21.9 grams (the weight variation in animals in the study did not exceed ± 20 % of the mean weight)
- Housing: Group caging (which is the standard procedure for small rodent studies, following AAALAC recommendations, to allow social interaction) during the observation period and individual caging in the radioactive proliferation test phase in the main experiment.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period:During the acclimation period of at least 13 days, the animals were kept under the same controlled environment conditions as during the experimental period.
- Indication of any skin lesions: no. The health status of the animals assigned to study were verified by the clinical Veterinarian.
Note: In the Preliminary Experiment mice of 7 weeks of age (18.0-19.6 g) were used.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.1-28.1°C
- Humidity (%): 30-78%
- Air changes (per hr): 15-20 air exchange/hour
- Photoperiod (hrs dark / hrs light):12 hours daily, from 6.00 a.m. to 6.00 p.m.
- IN-LIFE DATES: From: 17 June 2020 To: 28 July 2020
Environmental parameters (temperature and relative humidity) were continuously monitored and the minimum and maximum values were recorded twice a day during the study.
Due to technical reasons, relative humidity values (maximum of 78%) and temperature values (maximum of 28.1°C) outside the expected range of 30-70% and 19-25°C were recorded occasionally during the study, however this deviation is considered to have no impact on the outcome of the study and interpretation of the results.
Due to technical reason, environmental parameters (humidity and temperature) were recorded three times on 13 June 2020 (during acclimation). This additional measurement has no effect on the study.

Study design: in vivo (LLNA)

Vehicle:
propylene glycol
Remarks:
The following standard OECD No. 429 vehicles were assessed: Acetone: Olive oil 4:1 (v/v) mixture, N,N-dimethylformamide, Methyl ethyl ketone (MEK), Propylene glycol; Dimethyl sulfoxide (DMSO) and 1% aqueous Pluronic® PE9200.
Concentration:
50%, 25%, 10% in PG

The Preliminary Irritation/Toxicity Test was started according to the Study Plan on CBA/CaOlaHsd mice using two doses (2 animals/dose) at test item concentrations of 50% and 25% (w/v) in PG. The preliminary experiment was conducted in a similar experimental manner to the main study, but it was terminated on Day 6 and the radioactive proliferation assay was not performed.
In the Preliminary Irritation / Toxicity Test, all mice were observed daily for any clinical signs of systemic toxicity or local irritation at the application site. Both ears of each mouse were observed for erythema and scored.. Ear thickness was also measured using a thickness gauge on Day 1 (pre-dose), Day 3 (approximately 48 hours after the first dose) and Day 6. Additional quantification of the ear thickness was performed by ear punch weight determination after the euthanasia of the experimental animals.
During the Preliminary Irritation / Toxicity Test no mortality or clinical signs were observed. Minimal amount of test item residue was observed on the ears of all animals of the 50% (w/v) and 25% (w/v) dose groups from Day 1 to Day 6.
No marked body weight loss (>5% decrease in body weight) was observed in average body weight in any dose group in the preliminary test.
Ear thickness of the animals was measured using a thickness gauge on Days 1, 3and 6, and by ear punch weight determination after euthanasia of the experimental animals on Day 6.
No increased ear thickness value (>25%) was detected. Ear punch weights of the animals were within the historical control range.
The draining auricular lymph nodes of the animals were visually examined: they were normal in both dose groups (subjective judgement by analogy with observations of former experiments).
The 50% (w/v) dose group was considered acceptable and was therefore selected as highest dose for the main test.
No
No. of animals per dose:
4 animals / treatment group
Details on study design:

PRE-SCREEN TESTS:
- Compound solubility:
The following standard OECD No. 429 vehicles were assessed: Acetone: Olive oil 4:1 (v/v) mixture, N,N-dimethylformamide, Methyl ethyl ketone (MEK), Propylene glycol, Dimethyl sulfoxide (DMSO) and 1% aqueous Pluronic® PE9200.
The test item did not dissolve in any vehicle at concentration of 100% (w/v), the formulations were quickly settling dispersions. At concentration of 50% (w/v) the formulations with Acetone Olive oil 4:1 (v/v) mixture, N,N-dimethylformamide, Methyl ethyl ketone (MEK) were quickly settling dispersions. At concentration of 50% (w/v) Propylene glycol (PG) was slowly settling dark brown homogenous formulation which was considered appropriate with continuous mixing by visual inspection. Taking into account the test item characteristics and the study requirements, PG was selected as the vehicle for this study.

The Preliminary Irritation/Toxicity Test was started according to the Study Plan on CBA/CaOlaHsd mice using two doses (2 animals/dose) at test item concentrations of 50% and 25% (w/v) in PG. The preliminary experiment was conducted in a similar experimental manner to the main study, but it was terminated on Day 6 and the radioactive proliferation assay was not performed.
In the Preliminary Irritation / Toxicity Test, all mice were observed daily for any clinical signs of systemic toxicity or local irritation at the application site. Both ears of each mouse were observed for erythema and scored. Ear thickness was also measured using a thickness gauge on Day 1 (pre-dose), Day 3 (approximately 48 hours after the first dose) and Day 6. Additional quantification of the ear thickness was performed by ear punch weight determination after the euthanasia of the experimental animals.
- Irritation: yes
- Systemic toxicity:
yes
- Ear thickness measurements:
yes
- Erythema scores:
yes
During the Preliminary Irritation / Toxicity Test no mortality or clinical signs were observed. Minimal amount of test item residue was observed on the ears of all animals of the 50% (w/v) and 25% (w/v) dose groups from Day 1 to Day 6.
No marked body weight loss (>5% decrease in body weight) was observed in average body weight in any dose group in the preliminary test (Table 7 of Appendix 3).
Ear thickness of the animals was measured using a thickness gauge on Days 1, 3 and 6, and by ear punch weight determination after euthanasia of the experimental animals on Day 6. The ear thickness values and ear punch weights (2 per animal) are summarized in Table 8 of Appendix 3.
No increased ear thickness value (>25%) was detected. Ear punch weights of the animals were within the historical control range.
The draining auricular lymph nodes of the animals were visually examined: they were normal in both dose groups (subjective judgement by analogy with observations of former experiments).
The 50% (w/v) dose group was considered acceptable and was therefore selected as highest dose for the main test.
No ear thickness measurements or ear punch weight determination was required in the main test.

MAIN STUDY

Mortality
Animals were inspected for signs of morbidity and mortality at least once daily.
The principles and criteria summarized in the OECD Humane Endpoints Guidance Document No. 19 were taken into consideration.
Clinical observations
During the study (Day 1 to Day 6) each animal was observed daily for any clinical signs, including local irritation and systemic toxicity. Clinical observations were performed twice a day (before and after treatments) on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Individual records were maintained.
Body weights
Individual body weights were recorded on Day 1 (beginning of the test) and on Day 6 (prior to 3HTdR injection) with a precision of ± 0.1 g.
Proliferation assay
3HTdR

EVALUATION OF RESULTS
DPM was measured for each pooled group of nodes. The measured DPM values were corrected with the background DPM value ("DPM"). The average of the two measured DPM values of
5 % (w/v) TCA solutions was used as background DPM value.
The results were expressed as "DPN" (DPM divided by the number of lymph nodes) following the industry standard for data presentation.
Stimulation index (SI = DPN value of a treated group divided by the DPN value of the negative control group) for each treatment group was also calculated. A stimulation index of 3 or greater is an indication of a positive result.
Interpretation results:
The test item is regarded as a sensitizer if both of the following criteria are fulfilled:
-That exposure to at least one concentration of the test item resulted in an incorporation of 3HTdR at least 3-fold or greater than recorded in control mice, as indicated by the stimulation index.
-The data are compatible with a conventional dose response, although allowance must be made (especially at high topical concentrations) for either local toxicity or immunological suppression.
Acceptability of te test:
The Local Lymph Node Assay is considered valid if it meets the following criteria:
-the DPN value of the negative (vehicle) control group falls within the range of historical laboratory control data,
-the positive control substance produces a significant lymphoproliferative response (SI>3),
-the positive control is chosen such that it does not cause excessive skin irritation or systemic toxicity and the induction is reproducible but not excessive (i.e. SI>20),
-each treated and control group includes at least 4 animals,
-the test item does not cause serious systemic or local toxicity.

ANIMAL ASSIGNMENT AND TREATMENT
The animals were assigned to their respective dose groups by randomisation based on body weights. It was checked that all animals were within 20% of the overall mean at the start of the study. Animals were randomly allocated to the control and dose groups based on the most recent actual body weight; computer software (PROVANTIS v.9.3) was used in order to verify homogeneity/variation among/within groups.
- Criteria used to consider a positive response:
The test item is regarded as a sensitizer if both of the following criteria are fulfilled:
-That exposure to at least one concentration of the test item resulted in an incorporation of 3HTdR at least 3-fold or greater than recorded in control mice, as indicated by the stimulation index.
-The data are compatible with a conventional dose response, although allowance must be made (especially at high topical concentrations) for either local toxicity or immunological suppression.


TREATMENT PREPARATION AND ADMINISTRATION:
Test item was be freshly dissolved in applicable solvent to obtain appropriate concentrations shortly before application to mice and was considered to be stable for this short period. The applicable doses were based on the results of the Preliminary Irritation/Toxicity Test. The test item was weighed, and formulations prepared daily on a weight: volume basis as % (w/v) by the Pharmacy of Charles River Laboratories Hungary Kft.
As agreed with the Sponsor, no correction for purity of the test item was applied during formulation.
Analytical determination of the test item concentration, stability and homogeneity was not be performed because of the character and the short period of study.
The formulations were checked for visible homogeneity and physical stability before the start of the preliminary experiment. They were made shortly before application to mice and were considered to be stable for this short period.
During the study, animals were topically dosed with 25 µL of the appropriate formulation using a pipette on the dorsal surface of each ear. Each animal was dosed once a day for three consecutive days (Days 1, 2 and 3). There was no treatment on Days 4, 5 and 6.


PROLIFERATION ASSAY
On Day 6, animals were taken to the radioactive suite and each mouse was intravenously injected via the tail vein with 250 μL of sterile PBS (phosphate buffered saline) containing approximately 20 μCi of 3HTdR using a gauge 25G x 1" hypodermic needle with 1 mL sterile syringe. Once injected, the mice were left for 5 hours (±30 minutes).
Five hours (±30 minutes) after intravenous injection the mice were euthanized by asphyxiation with ascending doses of carbon dioxide (deep anaesthesia was confirmed before making incision, death was confirmed before discarding carcasses).
The draining auricular lymph nodes were excised by making a small incision on the skin between the jaw and sternum, pulling the skin gently back towards the ears and exposing the lymph nodes. The nodes were then removed using forceps. The carcasses were discarded after cutting through major cervical blood vessels.
Once removed, the nodes of mice from each test group was pooled and collected in separate Petri dishes containing a small amount (1-2 mL) of PBS to keep the nodes wet before processing.
A single cell suspension (SCS) of pooled lymph node cells (LNCs) was prepared and collected in disposable tubes by gentle mechanical disaggregating of the lymph nodes through a cell strainer using the plunger of a disposable syringe. The cell strainer was washed with PBS (up to 10 mL). Pooled LNCs were pelleted with a relative centrifugal force (RCF) of 190 x g (approximately) for 10 minutes at 4 °C. After centrifugation supernatants were discarded.Pellets were gently resuspended, and 10 mL of PBS was added to the tubes. The washing step was repeated twice. This procedure was repeated for each group of pooled lymph nodes.
After the final washing step, supernatants were removed. Pellets were gently agitated resuspended and 3 mL of 5% (w/v) TCA solution was added to the tubes for precipitation of macromolecules.
After (approximately 18 hours) incubation at 2-8°C, residues were centrifuged (approximately 190 x g for 10 minutes at 4°C), and supernatants were removed. Pellets were resuspended in 1 mL of 5% (w/v) TCA solution and dispersed by using an ultrasonic bath. Samples were transferred into a suitable sized scintillation vial filled with 10 mL of scintillation liquid and thoroughly mixed. The vials were loaded into a β-scintillation counter and 3HTdR incorporation was measured (10-minute measurement).
The β-counter expresses the 3HTdR incorporation as the number of radioactive disintegrations per minute (DPM). Background level was also measured in duplicates by adding 1 mL of 5% (w/v) TCA solution into a scintillation vial filled with 10 mL of scintillation liquid.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
none

Results and discussion

Positive control results:
The positive control substance was examined at a concentration of 25% (w/v) in the relevant vehicle (PG) using CBA/CaOlaHsd mice.
No mortality, cutaneous reactions or signs of toxicity were observed for the positive control substance in the study. A lymphoproliferative response in line with historical positive control data (stimulation index value of 10.6) was noted for HCA in the main experiment. This value was considered to confirm the appropriate performance of the assay.
Furthermore, the DPN values observed for the vehicle and positive control substance in this experiment were within the historical control range. Each test item treated, and control group included 4 animals.

In vivo (LLNA)

Resultsopen allclose all
Key result
Parameter:
SI
Value:
1.4
Test group / Remarks:
10% (W/V)
Key result
Parameter:
SI
Value:
1.1
Test group / Remarks:
25% (W/V)
Key result
Parameter:
SI
Value:
1.2
Test group / Remarks:
50% (W/V)
Cellular proliferation data / Observations:
CELLULAR PROLIFERATION DATA
The appearance of the lymph nodes was normal in the 50%, 25% and 10% (w/v) test and negative control groups and larger than normal in the positive control groups.
The SI values were 1.2, 1.1, 1.4 at concentrations of 50%, 25% and 10% (w/v), respectively.

DETAILS ON STIMULATION INDEX CALCULATION
DPM was measured for each pooled group of nodes. The measured DPM values were corrected with the background DPM value ("DPM"). The average of the two measured DPM values of 5 % (w/v) TCA solutions was used as background DPM value.
The results were expressed as "DPN" (DPM divided by the number of lymph nodes) following the industry standard for data presentation.
Stimulation index (SI = DPN value of a treated group divided by the DPN value of the negative control group) for each treatment group was also calculated. A stimulation index of 3 or greater is an indication of a positive result.


CLINICAL OBSERVATIONS:
There was no mortality or clinical signs observed during the main assay. Minimal amount of test item residue was observed on the ears of all animals in the 50% and 25% (w/v) dose groups from Day 1 to Day 6 and in the 10% (w/v) dose group from Day 1 to Day 3.

BODY WEIGHTS
Marked decrease (>5%) of the body weight was observed in one animal of the 10% (w/v) dose group and in one animal of the positive control group. However, the average body weight range was within the acceptable range of all groups. Therefore, these values were considered as individual variability.

SIGNS OF TOXICITY (including dermal irritation at the site of administration, if any, e.g. increased ear thickness).
there were no confounding effects of irritation or systemic toxicity at the applied concentrations

Any other information on results incl. tables

Proliferation Assay

The appearance of the lymph nodes was normal in the 50%, 25% and 10% (w/v) test and negative control groups and larger than normal in the positive control groups.

 

DPM, DPN and Stimulation Index Values for all Groups

Test Group
Name

Measured
DPM/group

DPM

No. Of
Nodes

DPN

Stimulation
Index Values

Background
(5 (w/v) % TCA)

33.5*

-

-

-

-

Negative control (PG)

2980

2946.5

8

368.3

1.0

50% (w/v)

3480

3446.5

8

430.8

1.2

25% (w/v)

3249

3215.5

8

401.9

1.1

10% (w/v)

4160

4126.5

8

515.8

1.4

Positive control (25% HCA)

31258

35328.0

8

3903.1

10.6

Note: Total DPM = Measured DPM – Background DPM

DPN = (Measured DPM – Background DPM value of TCA) / Number of nodes

*: The background values were 33 and 34.

 

The SI values were 1.2, 1.1, 1.4 at concentrations of 50, 25 and 10% (w/v), respectively.

 

INTERPRETATION OF THE OBSERVATIONS

The test item was powder, which was formulated in PG. Since there were no confounding effects of irritation or systemic toxicity at the applied concentrations, the proliferation values obtained are considered to reflect the real potential of the test item not to cause lymphoproliferation in the Local Lymph Node Assay. The resulting stimulation indices observed under these exaggerated test conditions were considered to be good evidence that Nickel Cobalt Manganese Hydroxide (8:1:1) is a non-sensitizer. The size of lymph nodes was in good correlation with this conclusion.

 

CLINICAL OBSERVATIONS

There was no mortality or clinical signs observed during the main assay.

Minimal amount of test item residue was observed on the ears of all animals in the 50% and 25% (w/v) dose groups from Day 1 to Day 6 and in the 10% (w/v) dose group from Day 1 to Day 3.

 

 

BODY WEIGHT

Marked decrease (>5%) of the body weight was observed in one animal of the 10% (w/v) dose group and in one animal of the positive control group. However, the average body weight range was within the acceptable range of all groups. Therefore, these values were considered as individual variability.

 

Individual Body Weights for all Animals with Group Means

 

Animal Number

Identity Number

Test Group Name

Initial Body weight (g)

Terminal Body Weight* (g)

Change#(%)

 
 

9933

1

Negative (vehicle) control
PG

20.6

20.5

-0.5

 

9928

2

20.1

19.9

-1.0

 

9930

3

19.9

19.5

-2.0

 

9924

4

20.3

20.7

2.0

 

 

 

Mean

20.2

20.2

-0.4

 

9927

5

Nickel Cobalt Manganese hydroxide (8:1:1) 50% (w/v) in PG

20.7

21.5

3.9

 

9926

6

20.0

20.3

1.5

 

9943

7

19.8

19.2

-3.0

 

9942

8

20.3

20.0

-1.5

 

 

 

Mean

20.2

20.3

0.2

 

9938

9

Nickel Cobalt Manganese hydroxide (8:1:1) 25% (w/v) in PG

20.5

20.9

2.0

 

9936

10

20.1

19.9

-1.0

 

9935

11

20.7

20.7

0.0

 

9934

12

19.9

19.5

-2.0

 

 

 

Mean

20.3

20.3

-0.3

 

 

Animal Number

Identity Number

Test Group Name

Initial Body weight (g)

Terminal Body Weight* (g)

Change#(%)

 
 

9939

13

Nickel Cobalt Manganese hydroxide (8:1:1) 10% (w/v) in
PG

19.9

19.5

-2.0

 

9941

14

20.4

20.5

0.5

 

9937

15

21.9

20.5

-6.4

 

9925

16

20.0

20.4

2.0

 
   

Mean

20.6

20.2

-1.5

 

9940

17

Positive control
25 (w/v) % HCA in PG

19.8

19.6

-1.0

 

9932

18

20.5

19.3

-5.9

 

9929

19

20.2

20.5

1.5

 

9931

20

21.0

20.9

-0.5

 
   

Mean

20.4

20.1

-1.5

 

 Notes:

*: Terminal body weights were measured on Day 6.

#: = (Terminal Body Weight – Initial Body Weight) / Initial Body Weight x 100

 

RESULTS OF THE PRELIMINARY IRRITATION / TOXICIYT TEST

Individual Body Weights for all Animals with Group Means (Preliminary Irritation/Toxicity Test)

Animal

Number

Identity

Number

Test Group

Name

Initial Body

Weight (g)

Terminal Body

Weight* (g)

Change#

(%)

9866

1

50% (w/v)

18.0

18.3

1.7

9864

2

50% (w/v)

19.3

20.2

4.1

 

 

Mean

18.7

19.3

2.9

9865

3

25% (w/v)

18.8

19.4

3.2

9863

4

25% (w/v)

19.6

20.0

2.0

 

 

Mean

19.2

19.7

2.6

Notes:

1.     #: = (Terminal Body Weight – Initial Body Weight) / Initial Body Weight x 100

2.     *: Terminal body weights were measured on Day 6.

 

Individual Ear Thickness for all Animals(Preliminary Irritation/Toxicity Test)

Animal

Number

Identity

Number

Test Group

Name

Ear Thickness

on Day 1 (mm)

Ear Thickness

on Day 3 (mm)*

Ear Thickness

on Day 6 (mm)*

Biopsy weight**

on Day 6
(mg)

Right

Left

Right

Left

Right

Left

9866

1

50% (w/v)

0.23

0.23

0.23

0.23

0.22

0.22

13.9

9864

2

50% (w/v)

0.22

0.22

0.23

0.22

0.23

0.23

14.7

9865

3

25% (w/v)

0.22

0.22

0.23

0.24

0.23

0.23

15.3

9863

4

25% (w/v)

0.21

0.22

0.24

0.24

0.22

0.23

14.9

Notes:

1.      *:In case of ear thickness values, irritant response is considered when result is ≥25% above the Day 1 value.

2.      **:Historical control range: 12.50-21.30 mg. Positive response is over 26.63 mg (≥25%).

 

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Remarks:
Under the conditions of the present assay, Nickel Cobalt Manganese Hydroxide (8:1:1), tested in a suitable vehicle (PG), was shown to have no sensitisation potential (non-sensitizer) in the Local Lymph Node Assay.
Conclusions:
In conclusion, under the conditions of the present assay, pNMC hydroxide (8:1:1), tested in a suitable vehicle (PG), was shown to have no sensitisation potential (non-sensitizer) in the Local Lymph Node Assay.
The study result triggers the following classification/labelling:
Regulation (EC) No 1272/2008 (CLP): Not classified
GHS (rev. 8) 2019: Not classified
Executive summary:

The object of this study was to determine the skin sensitisation potential of pNMC hydroxide (8:1:1) following dermal exposure in mice. The study was being performed with vertebrate animals because the chemical nature of the test item was not compatible with the available in vitro alternative tests. The in vitro testing was considered not to be technically feasible. Indeed, with Commission Regulation (EU) 2016/1688 adopted on the 20th September 2016, the testing strategy for the assessment of the skin sensitisation potential of a new substance now includes mandatory in vitro testing before any in vivo testing can be carried out, if the in vitro tests are technically feasible. This applies to all substances to be tested for EU REACH and CLP, but not for other regulatory purposes.

Before the start of this in vivo study, the Sponsor confirmed that existing data was not sufficient for the labelling or for the specific regulatory purpose for skin sensitisation.

The solubility of the test item was examined in a short Preliminary Compatibility Test. The best vehicle taking into account the test item characteristics and the requirements of the relevant OECD guideline was considered to be propylene glycol (PG). The 50% (w/v) formulation was the highest concentration which was suitable for the preliminary test.

A Preliminary Irritation/Toxicity Test was performed in CBA/CaOlaHsd mice using two doses (2 animals/dose): 50% and 25% (w/v) in PG and based on the results, 50% (w/v) dose was selected as top dose for the main test.

In the main assay, twenty female CBA/CaOlaHsd mice were allocated to five groups, each group comprised four animals:

  • -  three groups of animals received the test item at 50%, 25% and 10% (w/v, formulated in PG) concentrations,

  • -  a negative control group received the vehicle (PG) only,

  • -  a positive control group received 25% (w/v) α-Hexylcinnamaldehyde (HCA), formulated in PG. The formulations were applied to the dorsal surface of the ears of the experimental animals (25 μL/ear) for three consecutive days (Days 1, 2 and 3) and then animals were maintained on study for an additional 3 days. Cell proliferation in the (local) lymph nodes was assessed by measuring disintegrations per minutes after the incorporation of tritiated methyl thymidine (3HTdR) into the lymph nodes and the values obtained were used to calculate stimulation indices (SI) in comparison with the control group. There was no mortality or clinical signs observed during the main assay. Minimal amount of test item residue was observed on the ears of all animals in the 50% and 25% (w/v) dose groups from Day 1 to Day 6 and in the 10% (w/v) dose group from Day 1 to Day 3. The average body weight range was within the acceptable range of all groups.
    The SI values were 1.2, 1.1 and 1.4 at concentrations of 50%, 25% and 10% (w/v), respectively. The DPN values of the negative control group was in line with historical control data. The SI value for the positive control substance 25% (w/v) α-Hexylcinnamaldehyde (HCA), formulated in the same vehicle as the test item (SI=10.6) demonstrated the appropriate performance of the assay, therefore confirmed the validity of the assay. In conclusion, under the conditions of the present assay, Nickel Cobalt Manganese Hydroxide (8:1:1), tested in a suitable vehicle (PG), was shown to have no sensitisation potential (non-sensitizer) in the Local Lymph Node Assay.

The study result triggers the following classification/labelling:

- Regulation (EC) No 1272/2008 (CLP): Not classified
- GHS (rev. 8) 2019: Not classified