Dilutetium oxide silicate

Endpoint summary

Description of key information

Skin sensitisation - in vitro

An in vitro or in chemico skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study (initiated before October 11th 2016) is available.

Skin sensitisation - in vivo

A reliable skin sensitisation study is available for lutetium oxide silicate (Tarcai, 2017, GPMT study performed according to OECD guideline 406, scored Klimisch 1). In this study, no signs of contact sensitisation were detected after the challenge exposure in guinea pigs previously exposed to the test item during the experiment. In the control and treated animals, the mean of the scores was 0.00 according to the 24- and 48-hour results. Under the conditions of the present assay, lutetium oxide silicate was shown to have no skin sensitisation potential, and is classified as a non-sensitiser, according to current EU-regulations.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-10-11 to 2017-06-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The GPMT method (OECD 406) was preferred above LLNA (OECD 429) since previous experience with various rare earth compounds learned that there is an increased risk for false positive results when performing the LLNA. Additionally, insoluble inorganic substances, such as lutetium oxide silicate, are often not able to penetrate the skin.

Specific details on test material used for the study:

Correction factor for purity of the test item: 1.05.
Concentrations were calculated to anhydrous form.

Species:

guinea pig

Strain:

other: CRL:HA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, D- 97633 Sulzfeld , Germany
- Females, nulliparous and non-pregnant: yes
- Age at first dosing (Day 1): young adult, ~ 9 weeks old
- Weight at randomisation (Day -1): 363 - 435 g
- Housing: Macrolon cages size IV, with up to 5 animals/cage to allow socialisation. Lignocel® 3/4-S Hygienic Animal Bedding produced by J. Rettenmaier & Söhne GmbH+CO.KG (D-73494 Rosenberg, Holzmühle 1, Germany) was available to the animals during the study.
- Diet (e.g. ad libitum): Ad libitum, Cunigra Diet for Rabbits (produced by Bonafarm-Bábolna Takarmány Ltd., Hungary). This diet is classified as being suitable for guinea pigs as the vitamin D level is high enough to meet the needs of this species. This is the diet used by the breeder/supplier and animals are fully adapted to this diet on arrival.
- Water (e.g. ad libitum): Ad libitum, tap water from municipal supply as for human consumption, containing at least 50 mg/100 mL ascorbic acid. The drinking water is routinely analysed and is considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.
- Acclimation period: At least 5 days before start of treatment under laboratory conditions. Animals were examined on arrival and only healthy animals were used for the test. The health status was certified by the veterinarian.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16.5–21.6°C
- Humidity (%): < 20–60 %
- Air changes (per hr): 15-20 air exchange/hour
- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light

Route:

other: intradermal (main study part I)

Vehicle:

other: 1% methylcellulose

Concentration / amount:

1% test item in vehicle

Day(s)/duration:

day 1 of treatment

Route:

other: dermal (main study part II)

Vehicle:

other: 1% methylcellulose

Concentration / amount:

100% test item in vehicle

Day(s)/duration:

day 8 of treatment; 48 hours of exposure

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: 1% methylcellulose

Concentration / amount:

100% test item in vehicle; vehicle in right side

Day(s)/duration:

day 22 of treatment; 24 hours of exposure

No. of animals per dose:

preliminary test: 8 female animals
main test: 10 in the test group, 5 in the control group

Details on study design:

RANGE FINDING TESTS
- The dose levels for the main study were selected based on the results of the preliminary test.
- A day prior to the test, the hair was removed from the right and left sides of the animals (approximately 5x5cm). The hair removal was performed carefully to ensure animals are closely shaven.
- A series of test item concentrations was tested to identify the primary irritation following intradermal injection and dermal application: 1, 2.5 and 5% (w/v) concentrations (5% with FCA as well) were used for intradermal injection and 25, 50, 75 and 100% (w/v) for dermal application.
- For the intradermal application, 0.1 mL per concentration was injected intradermally into the hair free skin of the animals. Two concentrations were injected on the right side and another two concentrations on the left side of the animals. The highest concentration (5%) for intradermal treatment was also used in a 1:1 mixture (v/v) of Freund's complete Adjuvant and 1% mehylcellulose solution. Each concentration was injected in duplicate. Two animals were used per concentration.
- For the dermal application, the volume of the concentrations was 0.5 mL. A closed patch exposure was performed by means of an occlusive bandage using similar treatment procedures as for the main study. The time of exposure for the dermal application was 48 hours. In the preliminary study one concentration was used on the right side and another concentration on the left side of the animals. Two animals per concentrations were used in the preliminary study.
- Local effects were examined and scored 1, 24, 48 and 72 hours after the treatment or after patch removal.
- Skin effects were scored for erythema and oedema; any other observations of changes to the skin were recorded.

MAIN STUDY
A. INDUCTION EXPOSURE
A1 INTRADERMAL INDUCTION EXPOSURE (day 1)
- No. of exposures: 3 pairs of intradermal injections (0.1 mL/site)
- Test groups (the first listed nearest the head): 2 injections of Freund's Complete Adjuvant and 1% MC in a 1:1 (v/v) mixture, 2 injections of 1% test item in 1% MC, 2 injections of 1% test item, formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and 1% MC .
- Control group (the first listed nearest the head): 2 injections of Freund's Complete Adjuvant and 1% MC in a 1:1 (v/v) mixture, 2 injections of 1% MC, 2 injections of vehicle (1% MC), formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and 1% MC.
- Site: Scapular region. On the day before treatment, an area approximately 5x5cm on the scapular region of the animals was clipped free of hair and was carefully shaved.
- Frequency of applications: one application
- Skin reactions were observed and recorded as follows: 1, 24, 48 and 72 hours after the patch removal

A2 DERMAL INDUCTION EXPOSURE (day 8)
- Since 100% concentration of the test item was not skin irritant in the dermal dose range finding study, the test area was painted with 10% sodium dodecyl sulphate approximately 24 hours prior to dermal induction exposure.
- Site: The same scapular region which received the intradermal injections, were used for dermal induction exposure.
- Test groups: Seven days after the intradermal injections, the same hair-free scapular area was treated. A 2.5x2.5cm sterile gauze patch (approximately 4 layers of porous gauze pads) was saturated with approximately 0.5 mL of the test item at 100% concentration and placed over the injections ites (scapular region). The gauze patches were kept in contact with the skin by a patch with a surrounding adhesive hypoallergenic plaster. The treated areas were covered for 48 hours with a fully occlusive foil (Closed Patch Test). After the patch removal, any remaining test item was removed with a wet gauze swab. Following the dermal induction treatment, the animals were left untreated for 14 days prior to challenge applications.
- Control group: The control group was treated with 0.5 mL vehicle (1% MC) using the same method.
- Frequency of application: one application
- Skin reactions were observed and recorded as follows: 24 hours after treatment

B. CHALLENGE EXPOSURE (day 22)
- Day(s) of challenge: day 22
- Exposure period: 24 hours
- Site: Left and right sides, approximately 24 hours before the treatment, the hair was removed from an area of approximately 5x5cm on the left and right sides of each animal.
- Test groups: A 2.5x2.5 cm patch of sterile gauze was saturated with approximately 0.5 mL of test item at 100% concentration (highest achievable and non-irritant dose) and applied to the left side of all animals (both the test and the control). After patch removal, any remaining test item was removed with a wet gauze swab.
- Control group: The right shaved side area of all animals was treated with the vehicle (1% MC).
- Skin reactions were observed and recorded as follows: 24 and 48 hours after the patch removal

OTHER
BODY WEIGHT
Body weight was recorded with a precision of 1 g at randomisation (Day -1), then at least weekly, including Day 25 prior to euthanasia. The mean values and the standard deviations were calculated and reported.

OBSERVATIONS
- Mortatlity/Clinical signs: Daily during the test.
- Detailed clinical observations were made on all animals outside the home cage in a standard arena before the first treatment (on the day of randomisation) and at least weekly thereafter. The dermal irritation scores (in cases of dermal induction exposures) were evaluated according to the scoring system by Draize (1959)

TERMINAL PROCEDURE
Terminally animals were sacrificed under pentobarbital anaesthesia.

Challenge controls:

A 2.5x2.5 cm patch of sterile gauze was saturated with approximately 0.5 mL of test item at 100% concentration (highest achievable and non-irritant dose) and applied to the left side of all animals. The right shaved side area of all animals was treated with the vehicle (1% MC)

Positive control substance(s):

yes

Remarks:

2-mercaptobenzothiazole

Positive control results:

Challenge with the test item 2-mercaptobenzothiazole elicited discrete erythema (score 1) on the skin surface of previously sensitised guinea pigs. The mean of the scores was 0.80 (80% of animals) at 24 hours observation and 0.70 (70% of animals) at 48 hours observation. In the control group, the mean of the scores was 0.00. On the basis of the results of the present study, the test item 2-mercaptobenzothiazole was classified as a skin sensitiser. This demonstrates that the Magnusson and Kligman method (OECD 406) in this laboratory is considered to be reliable.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

100%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No signs of systemic or local toxicity were observed. No mortality was observed.

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

100%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No signs of systemic or local toxicity were observed. No mortality was observed.

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

100%

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

No signs of systemic or local toxicity were observed. No mortality was observed.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

100%

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

No signs of systemic or local toxicity were observed. No mortality was observed.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

Discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

7

Total no. in group:

10

Clinical observations:

Discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Preliminary study

- The concentration of 2.5%, 5% and 5% with FCA caused a maximum of well-defined erythema (score 2), whereas the concentration of 1% caused very slight erythema (score 1). The formulation of 5% with FCA could not be administered as a whole (the skin resisted to the injection), thus two additional animals were used after the end of the first preliminary study to check the maximum concentration (with saline or 1% methylcellulose) that is administrable as a whole injection (0.1 mL). Concentrations of 5%, 2.5% and 1% with FCA:saline, and 5% and 2.5% FCA:1% methylcellulose were not appropriate for intradermal treatment (not possible to inject or not possible to inject as a whole). The highest applicable concentration was 1% in FCA:1% methylcellulose, therefore this concentration and vehicle were considered to be appropriate for the main study intradermal treatment.

- Adverse effects were not observed during the dermal treatment of the preliminary study in each concentration (25%, 50%, 75% and 100%).

- On the basis of results of the preliminary dose range finding study, the following treatments were chosen for the main study:

*Intradermal induction: 1% test item formulated in 1% MC in the test group and 1% MC in the control group.

*Dermal induction: 100% test item formulated in 1% MC in the test group and 1% MC in control group. Since the 100% test item was not skin irritant in the dermal dose range finding study, 0.5 mL of 10% sodium dodecyl sulphate in vaseline was applied 24 hours prior to the topical induction application, in order to create local irritation. Therefore, six days after the intradermal injections, the same scapular area (approximately 5x5 cm) was clipped free of hair (if necessary) prior to the application.

*Challenge phase: 100% test item in 1% MC on the left side and 1% MC on the right side for all animals (treatment and control group) as a challenge exposure. This concentration was the highest which caused no irritation.

Main study

- Test group: After the challenge with the test item at a concentration of 100% formulated in 1% MC, no positive response was observed in the treated animals on the left flank. The mean of scores was 0.00 according to the 24 and 48-hour results. The right shaved side of test animals was treated with 1% MC and no reaction was noted.

- Control group: After the challenge with the test item at a concentration of 100% formulated in 1% MC, no visible changes were found at the 24 and 48-hours examinations on the left flank. The right shaved side of control animals was treated with 1% MC and no reaction was noted.

- Clinical observations: No signs of systemic or local toxicity were observed. No mortality was observed during the study.

- Body weight: There were no notable differences between the test animal group and the control group.

Interpretation of results:

GHS criteria not met

Conclusions:

Challenge with test item (lutetium oxide silicate) evoked no positive responses in the test animals previously sensitised with the test item or in the control group. The net response value represented an incidence rate of 0% and the net score value of 0.00.
In conclusion, under the conditions of the present assay the test item lutetium oxide silicate was shown to have no skin sensitisation potential and does not need to be classified as a skin sensitiser, according to current GHS criteria and EU-regulations.

Reference 2

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin sensitisation - in vitro

An in vitro or in chemico skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study (initiated before October 11th 2016) is available.

Skin sensitisation - in vivo

A skin sensitisation study was performed in the guinea pig according to the Magnusson and Kligman method, using a maximisation method, with Freund's Complete Adjuvant to evaluate the sensitisation potential of the test item. The study was performed according to OECD guideline 406 and in compliance with GLP guidelines (Tarcai, 2017, scored Klimisch 1). This skin sensitisation potential test method (OECD 406) was preferred above the LLNA (OECD 429) since previous experience with various rare earth compounds learned that there is an increased risk for false positive results when performing the LLNA. Additionally, insoluble inorganic substances, such as lutetium oxide silicate, are often not able to penetrate the skin.

Based on the results of a preliminary test, 10 test animals were subjected to sensitisation procedures in a two-stage process incorporating an induction phase using an intradermal treatment followed by a 48-hour topical application (dermal treatment under an occlusive dressing). The test item was used at a concentration of 1% (w/v) in 1% methylcellulose for intradermal injections, and at a concentration of 100% (w/v) in 1% methylcellulose for topical sensitisation treatment. Since the 100% formulation was not skin irritant in the dermal dose range-finding study, the test area was painted with 0.5 mL of 10% SDS in vaseline 24 hours prior to the topical induction application, in order to create local irritation. Five control guinea pigs were simultaneously exposed to 1% methylcellulose during the sensitisation phase (intradermal and dermal treatment). Two weeks after the last induction exposure, a challenge dose at a concentration of 100% (w/v) in 1% methylcellulose was dermally administered on the left side of all animals for 24 hours. The right side of the animals was treated with 1% methylcellulose only. Skin reactions were measured 24 and 48 hours after patch removal. No test item-related signs of systemic toxicity were observed in any animal. No signs of contact sensitisation were detected after the challenge exposure in guinea pigs previously exposed to the test item during the experiment. In the control and treated animals, the mean of the scores was 0.00 according to the 24- and 48-hour results. Under the conditions of the present assay, the test item was shown to have no sensitisation potential, and is classified as a non-sensitiser, according to current EU-regulations.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Skin sensitisation

The test item is considered to be non-sensitising, based on the results of a GPMT study (OECD guideline 406).

Respiratory sensitisation

No reliable study is available.