Hydrogen [2,4-dihydro-4-[(2-hydroxy-4-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)][2,4-dihydro-4-[(2-hydroxy-5-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)]chromate(1-)

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

other: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

From June 27 to August 8, 1994

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The complete read across justification is detailed in section 13. Source study has reliability 1.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

(room T varied between 21-25 °C. Due to positive reactions in the control group, a 2nd epidermal pretest was performed. After 9 d, second challenge was performed with 10 additional untreated control animals and 2 test substance concentrations)

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Deviations:

yes

Remarks:

(room T varied between 21-25 °C. Due to positive reactions in the control group, a 2nd epidermal pretest was performed. After 9 d, second challenge was performed with 10 additional untreated control animals and 2 test substance concentrations)

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

Maximisation test was available.

Test material

Test material information

Constituent 1

Reference substance name:

Similar Substance 03

IUPAC Name:

Similar Substance 03

Test material form:

solid: particulate/powder

In vivo test system

Test animals

Species:

guinea pig

Strain:

Himalayan

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: BRL, Biological Research Laboratories Ltd. Wolferstrasse 4, CH-4414 Fullinsdorf/Switzerland.
- Number of animals for main study / pretest: 40 females/10 females, nulliparous and non-pregnant
- Age: 5-7 weeks
- Weight: 226-353 g (Control Group I and Test Group), 274-362 g (Intradermal pretest and epidermal pretest I), 261 - 266 g (Epidermal pretest II)
- Housing: individually in Makrolon type-3 cages with autoclaved standard softwood bedding ("Lignocel", Schill AG, CH-4132 Muttenz)
- Diet: pelleted standard Kliba 342, batch nos. 63/94 (at delivery of the animals to 03-August-94) and 64/94 (from 04 August 1994 to termination of test) guinea pig breeding/ maintenance diet ("Kliba", Klingentalmuhle AG, CH-4303 Kaiseraugst) (ad libitum)
- Water: community tap water (ad libitum); once weekly additional supply of ascorbic acid (1 g/L) via the drinking water
- Acclimation period: one week for the control group I and test group under test conditions after health examination. 10 d for the control group II. No acclimatization for the animals of the intradermal pretest and epidermal pretest I. 1 d for the epidermal pretest II. Only animals without any visual signs of illness were used for the study.
-Identification: by unique cage number and corresponding ear tags.
-Randomization: randomly selected at time of delivery

ENVIRONMENTAL CONDITIONS
- Temperature: 21 to 25 °C
- Humidity: 52-70 %
- Air changes: 10-15 air changes/h
- Photoperiod: 12 h/12 h (music during the light period)

IN-LIFE DATES: June 27 to August 8, 1994

Study design: in vivo (non-LLNA)

Induction

Route:

intradermal and epicutaneous

Vehicle:

other: ethanol and FCA/physiological saline (1/1) were used for the intradermal applications and vaselinum album for the epidermal applications

Concentration / amount:

concentration for intradermal injection: 5 % *
concentration for epicutaneous application: 50 % *
*concentration selected based on pretest I

Challenge

Challenge 1

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: ethanol and FCA/physiological saline (1/1) were used for the intradermal applications and vaselinum album for the epidermal applications

Concentration / amount:

1st challenge:
concentration for epicutaneous application: 50 % *
*concentration selected based on pretest I

Challenge 2

No.:

#2

Route:

epicutaneous, occlusive

Vehicle:

other: ethanol and FCA/physiological saline (1/1) were used for the intradermal applications and vaselinum album for the epidermal applications

Concentration / amount:

2nd challenge:
concentration for epicutaneous application: 50 and 25 %**
**concentration selected based on pretest II

No. of animals per dose:

Preliminary study
Intradermal injections group: 2 animals
Epicutaneous applications group: 4 animals

Main study
Control group: 10 animals
Test group: 20 treated animals

Details on study design:

PRETEST
INTRADERMAL INJECTIONS:
Intradermal injections (0.1 ml/site) were made into the clipped flank of two guinea-pigs at concentrations of 5, 3 and 1 % of the test substance in ethanol. The resulting dermal reactions were assessed 24 h later. For intradermal induction application a 5 % test substance dilution was selected.

EPIDERMAL PRETEST I:
Both flanks of each of 4 guinea pigs were clipped and shaved just prior to the application. Thereafter 4 patches of filter paper ( 2 × 2 cm) were saturated with the test substance at 50 % (this concentration used was found to be the most qualified to assure an optimum technical application procedure), 25 %, 15 % and 10 % of the test substance in vaselinum album and applied to the clipped and shaved flanks. The patches were covered by a strip of aluminum foil and firmly secured by elastic plaster wrapped around the trunk and covered with impervious adhesive tape. This procedure ensured the intensive contact of the test substance. The dressings were removed after an exposure period of 24 h. 21 h after removing of the dressing the application site was depilated with an approved depilatory cream to clean the application site from staining produced by the test substance, so that possible erythema reactions were clearly visible at that time. The depilatory was placed on the patch sites and surrounding areas, and left on for 3-5 minutes. It was then thoroughly washed off with a stream of warm, running water. The animals were then dried with a disposable towel, and returned to their cages. The reaction sites were assessed 24 and 48 h after removal of the bandage for erythema and oedema on a numerical basis according to Draize score. The allocation of the different test dilutions to the sites on the animals was alternated in order to minimize site to site variation in responsiveness. For the epidermal induction and first challenge procedure the test substance at 50 % was selected.

INDUCTION

Intradermal injections performed on test day 1: An area of dorsal skin from the scapular region (approximately 6 × 8 cm) was clipped free of hair. Three pairs of intradermal injections (0.1 ml/site) were made at the border of a 4 × 6 cm area in the clipped region as follows:
Test Group:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
2) test substance, diluted to 5 % with ethanol.
3)* test substance diluted to 5 % by emulsion in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
Control Group:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
2) ethanol.
3)* 1:1 (w/w) mixture of ethanol in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.

*deviation of EU Method in which the vehicle is mixed with FCA only in the control group and liposoluble or insoluble substances are mixed with FCA only in the test group. A mixture of FCA:physiological saline was chosen instead of FCA only in order to decrease the site effects of FCA when applied alone.

Epidermal applications performed on test day 8: on 7 d and 23.5 h prior to the epidermal application the scapular area (approx. 6 × 8 cm) was clipped, shaved free of hair and the test area was pretreated with 10 % Sodium-Lauryl-Sulfate (SLS) in paraffinum perliquidum as no primary irritation had been observed in the pretest. The SLS was massaged into the skin with a glass rod without bandaging. This 10 % concentration of SLS enhances sensitization by provoking a mild inflammatory reaction.
On 8 d, a 2 × 4 cm patch of filter paper was saturated with the test substance (50 % in vaselinum album) and placed over the injection sites of the test animals. The patch was covered with aluminum foil and firmly secured by an elastic plaster wrapped around the trunk of the animal and secured with impervious adhesive tape. The dressings were left in place for 48 h. The epidermal application procedure described ensured intensive contact of the test substance. The guinea pigs of the control group I were treated as described above with vaselinum album only. Reaction sites were assessed for erythema and oedema 24 and 48 h after removal of the dressing, using the numerical grading system according to Draize.


FIRST CHALLENGE performed on test day 22: test group and control group I were challenged two weeks after the epidermal induction application. The test and control guinea-pigs were treated in the same way. Hair was clipped and shaved from a 5 × 5 cm area on the left and right flank of each guinea-pig just prior to the application. Two patches ( 2 × 2 cm) of filter paper were saturated with the highest non-irritating concentration of 50 % (left flank) and the vehicle only (vaselinum album, applied to the right flank) using the same method as for the epidermal application. The dressing were left in place for 24 h. 21 h after removing of the dressing the test sites were depilated with an approved depilatory cream (VEET Cream, Reckitt & Colman AG, CH-4123 Allschwil). The cream was placed on the patch sites for 3-5 minutes and then washed off with a stream of warm running water. When the application sites were clean and any stains from the test substance removed the animals were dried with a disposable paper towel and returned to their cages. 25 and 48.5 h after the removal of the dressing the application sites were assessed for erythema and oedema using the numerical scoring system according to Draize.

EPIDERMAL PRETEST II performed on test day 26: very slight to well-defined erythematous reactions were observed in the control group I after the first challenge when treated with the test substance at 50 % in vaselinum album. Therefore, a second epidermal pretest was performed prior to the second challenge to confirm the highest non-irritating concentration of 50 % in vaselinum album determined in the pretest I. The second epidermal pretest was performed in the same way and in the same concentrations as the first pretest. Four additional animals were used. The test substance at 50% in vaselinum album was considered to be the highest nonirritating concentration used for the second challenge procedure. In addition, the test substance at 25 % in vaselinum album was applied in the second challenge.

SECOND CHALLENGE performed on test day 31: a second challenge was performed nine days after the first challenge. The treatment procedure used for the animals in the test group was the same as that described for the first challenge except the applications were made to the opposite flanks of the guinea pigs. Ten additional untreated control animals were used and treated in the same conditions as the test group. The test substance at 50 % and 25 % in vaselinum album was applied on the right cranial and right caudal flank.

Challenge controls:

First challenge: test substance 50 % (left flank) and Vaseline album (right flank)
Second challenge: test substance 50 % (right cranial flank), 25 % (right caudal flank). Ten additional untreated control animals were used.

Positive control substance(s):

yes

Remarks:

2-mercaptobenzothiazol and 4-aminobenzoic acid ethyl ester tested in another study)

Results and discussion

Positive control results:

Positive response was observed in 60 % of treated animals after the epidermal challenge application.

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50 % epidermal application (left flank)

No. with + reactions:

1

Total no. in group:

20

Clinical observations:

very slight erythematous reaction

Results 2

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50 % epidermal application (left flank)

No. with + reactions:

11

Total no. in group:

20

Clinical observations:

very slight or well defined erythematous reactions

Results 3

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

50 % epidermal application (right cranial flank)

No. with + reactions:

1

Total no. in group:

20

Clinical observations:

very slight erythematous reaction

Results 4

Reading:

rechallenge

Hours after challenge:

24

Group:

test chemical

Dose level:

25 % epidermal application (right caudal flank)

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

no positive reactions were observed

Results 5

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

50 % epidermal application (right cranial flank)

No. with + reactions:

3

Total no. in group:

20

Clinical observations:

very slight erythematous reaction

Results 6

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

25 % epidermal application (right caudal flank)

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

no positive reactions were observed

Any other information on results incl. tables

Main Study

Skin effects after intradermal induction performed on test day 1

CONTROL GROUP I

Injection site 1: the area around the injection site was oedematous and erythematous from test day 2 to 5, and became necrotic from test day 6 to 10, followed by encrustation and exfoliation of encrustation up to the termination of test.

Injection site 2: the reactions observed were identical to those obtained at injection site 1 with the mixture of FCA and physiological saline

Injection site 3: the reactions observed were identical to those obtained at injection site 1 with the mixture of FCA and physiological saline.

As the animals were bandaged with the semi-occlusive dressing no observations of the skin were possible on test day 9.

TEST GROUP

Injection site 1: the reactions observed were identical to those obtained in the control group with the mixture of FCA and physiological saline, at injection site 1.

Injection site 2: the area around the injection site was oedematous and red discolored from test day 2 to 5 and 2 to 6 respectively, necrotic from test day 6 to 10, followed by encrustation and exfoliation of encrustation up to the termination of test.

Injection site 3: the reactions observed were identical to those obtained at injection site 2 with the 5 % solution of test substance in ethanol.

As the animals were bandaged with the semi-occlusive dressing no observations of the skin were possible on test day 9.

Skin effects after epidermal induction performed on test day 8

CONTROL GROUP I: no erythematous or oedematous reaction was observed in the animals treated with vaselinum album only.

TEST GROUP: as the test substance stained the skin red, it was not possible to determine whether erythema was present. However, no oedema was observed. Red discoloration was noted from test day 10 to 24. All animals of the control and test group were pretreated with a 10 % SLS in paraffinum per liquidum.

Skin effects after the first and second challenge performed on test day 22 and 31 respectively

CONTROL GROUP I

First challenge: no positive reactions were observed in the animals treated with vaselinum album alone. Red discoloration was noted from test day 23 (after removal of the dressing) to 24 (prior to the depilation). One animal was observed with a very slight erythematous reaction at the 24 h reading when treated with the test substance at 50 % in vaselinum album. At the 48 h reading, 6 animals (out of 10) were observed with very slight or well defined erythematous reactions.

CONTROL GROUP II

Second challenge: no positive reactions were observed in the animals either when treated with vaselinum album alone or when treated with the test substance at 50 % and 25 % in vaselinum album. Red discoloration was noted from test day 32 (after removal of the dressing) and 33 (prior to the depilation).

TEST GROUP

First challenge: no positive reactions were observed in the animals treated with vaselinum album alone. One animal was observed with a very slight erythematous reaction at the 24 h reading when treated with the test substance at 50 % in vaselinum album. At the 48 h reading, 11 animals (out of 20) were observed with very slight or well defined erythematous reactions. Red discoloration was noted from test day 23 (after removal of the dressing) to 24 (prior to the depilation).

Second challenge: no positive reactions were observed in the animals either when treated with vaselinum album alone or when treated with the test substance at 25 % in vaselinum album. One animal was observed with a very slight erythematous reaction at the 24 h reading when treated with the test substance at 50 % in vaselinum album. At the 48 h reading 3 animals (out of 20) were observed with the same reactions. Red discoloration was noted from test day 32 (after removal of the dressing) to 33 (prior to the depilation).

Viability / mortality / macroscopic findings

One animal of the intradermal pretest was found dead on test day 27. At necropsy many dark red foci (D = 10 mm) were observed in the lungs.

Clinical signs, systemic

No symptoms of systemic toxicity were observed in the animals.

Body weights

One animal of the control group lost weight during the acclimatization period. The loss of weight should be considered to be of incidental nature

Applicant's summary and conclusion

Interpretation of results:

other: not sensitising according to the CLP Regulation (EC 1272/2008)

Conclusions:

Under the conditions of the study, test substance was not considered to induce delayed contact hypersensitivity in treated animals when tested at the concentration of 25 %.

Executive summary:

Method

Guinea pig maximization study was conducted to evaluate the skin sensitisation potential of the test substance (of 80 % purity) according to OECD guideline 406 and EU method B.6 with few deviations. A preliminary study was carried out to select application doses. Main study consisted of an induction phase, both intradermal and epidermal, and two challenges; 10 females were used as control group, while 20 females were used as test group.

Upon results of the first challenge, a second challenge was performed with 10 additional control animals. Prior to the second challenge, a second epidermal pretest was performed to confirm the first epidermal pretest in which the test article at 50 % was determined as the highest non-irritating concentration.

Results

Based on the results of a preliminary study, 5 and 50 % were selected as intradermal and topical induction doses respectively. The highest non-irritating test substance concentration used for challenge application was 50 % in vaselinum album. 

After the first challenge, positive skin reactions were observed in the control group. Test substance at 50 % in vaselinum album was determined twice as the highest non-irritating concentration. However, by comparison, the second challenge did not confirm the first challenge with the test article at 50 % and the interpretation is therefore very ambiguous. Further, an additional test substance concentration of 25 % was applied in the second challenge procedure. No skin reactions were observed in the control and test group at test substance concentration of 25 %.

Under the conditions of the study, the test substance was not considered to induce delayed contact hypersensitivity in treated animals when tested at the concentration of 25 %.

No toxic symptoms were evident in the guinea pigs of the control or test group.