1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

Endpoint summary

Description of key information

Guideline-compliant studies of skin sensitisation in the Guinea pig (Buehler and Maximisation designs) are available and both show a lack of skin sensitisation for pencycuron.  The Maximisation study is considered key as this method is generally considered to be more sensitive than the Buehler method (supporting), although both designs are scientifically valid.  These two in vivo studies were performed prior to the validation and adoption of alternative methods.

Test Species/Type	Results	Assessment	Reference
OECD 406 - Maximisation study	Pencycuron was not a skin sensitiser.	Key study	Heimann (1984)
OECD 406 - Buehler study	Pencycuron was not a skin sensitiser.	Supporting study	Sheets (1989)

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:

1984-06-29

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

The most important deviations from the guideline were: no results of a reliability check were provided; no results of the induction application were provided; the dose-selection is unclear

GLP compliance:

no

Remarks:

Older study, predates mandatory GLP

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The study was performed before the adoption of the OECD test guideline (OECD 429) for the LLNA, in 2010

Species:

guinea pig

Strain:

Dunkin-Hartley

Remarks:

DHPW

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 280 - 375 g.
- Housing: The animals were kept, five to a Makrolon cage type IV.
- Diet: Altromin 3022 Diet for guinea pigs, ad libitum
- Water: drinking water from bottles, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature: 22-24° C
- Humidity: 30-50 %
- Photoperiod: light/dark rhythm 12 hours.

Route:

intradermal

Vehicle:

other: Cremophor EL/physiological saline

Concentration / amount:

1%

Day(s)/duration:

Day 1

Route:

intradermal and epicutaneous

Vehicle:

other: Cremophor EL/physiological saline

Concentration / amount:

25%

Day(s)/duration:

Topical induction was performed for 48 hours, one week after intradermal injection

Adequacy of induction:

other: Although the highest topical induction concentration of 25% w/v did not result in a skin reaction, this concentration is considered to be sufficient, as it is near the maximum concentration for powders to obtain a well-mixed suspension (ca. 30%).

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: Cremophor EL/physiological saline

Concentration / amount:

25%

Day(s)/duration:

24 hours

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

Three animal groups (one test compound and two control groups) each consisting of 20 male animals (test compound group) and ten males (control groups)

Details on study design:

RANGE FINDING TESTS:
The doses in the main study were based on the results of a range-finding study using 0, 1, 2.5, and 5% w/v (intradermal induction) and 3, 6, 12.5, and 25% w/v (topical induction). Although the effects induced by intradermal injection of the test concentrations were not indicated, the intradermal induction dose was determined to be 1% w/v.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (intradermal (3 sites) and topical)
- Exposure period: 48 hours for the topical induction
- Test groups: 1 test group of 20 males.
- Control group: 2 control groups of 10 males each.
- Site:
For the intradermal induction: Starting at the back of the neck, three intradermal injections were given parallel to each flank. The intervals between the injection sites were approx. 1- 2 cm.
For the topical induction: placed between or on the injection sites
- Concentrations: 1% Pencycuron in the intradermal induction, and 25% Pencycuron for the topical induction.

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 1 but observed up to 48 hours after exposure.
- Exposure period: 24 hours
- Test groups: 1 test group of 20 males.
- Control group: 1 control group of 10 males each.
- Site: on the left flank of the animals
- Concentrations: 25% Pencycuron.
- Evaluation (hr after challenge): 24 and 48

Challenge controls:

A hypoallergenic dressing soaked in the formulation vehicle was placed on the left flank of the animals in the first control group, and fastened to the skin with occlusive tape for 24 hours.
For comparison a similar control dressing was fastened to the right flank, and this had only been soaked with the formulation vehicle.

Positive control substance(s):

no

Positive control results:

Not reported

Reading:

1st reading

Hours after challenge:

24

Group:

other: vehicle control

Dose level:

0%

No. with + reactions:

1

Total no. in group:

20

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

other: vehicle control

Dose level:

0%

No. with + reactions:

1

Total no. in group:

20

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

25%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

25%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

25%

No. with + reactions:

2

Total no. in group:

20

Remarks on result:

no indication of skin sensitisation

Remarks:

The incidence of animals with positive dermal reactions (10%) is marginally higher than the incidence of reactions to the vehicle (5%) and is not indicative of skin sensitisation.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

25%

No. with + reactions:

1

Total no. in group:

20

Remarks on result:

no indication of skin sensitisation

Remarks:

The incidence of animals with positive dermal reactions (10%) is marginally higher than the incidence of reactions to the vehicle (5%) and is not indicative of skin sensitisation.

Reading:

other: No details reported

Group:

positive control

Remarks on result:

not measured/tested

Interpretation of results:

GHS criteria not met

Conclusions:

Pencycuron is not sensitising to the skin of guinea pigs in this Maximisation test.

Executive summary:

Pencycuron was investigated for possible skin-allergising potential with a sensitisation test on male guinea pigs (MAGNUSSON and KLIGMAN's maximisation test). Pilot tests to establish the dose indicated that the following concentrations of the test compound should be used in the study:

intradermal induction: 1 %
topical induction: 25 %
challenge: 25 %

After the challenge one animal in the test compound group reacted positively according to the evaluation criteria, while the animals in the control group did not exhibit any alterations. The degree of intensity of the response in this animal was only slight. The reaction observed in the skin of one animal is not significant, as experience has shown that individual animals can react spontaneously in this way.

The results therefore indicate that the test compound does not have a skin-sensitising effect on guinea pigs.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1988-10-05 to 1989-07-25

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

See Principles of method if other than guideline.

Principles of method if other than guideline:

The study was not performed in accordance with OECD 406, because of the following deviations from the guideline:
too few test and control animals were used, the choice for the vehicle is unclear, because it caused effects on the skin, the dose-selection is unclear, the challenge exposure (24 hours) was too long, control animals did not receive the induction application.

The doses in the main study were based on the results of a range-finding study using 0.5, 1.0, 5.0, 10, 25, 50, and 100% (i.e. moistened with water) w/v topical applications. The vehicle and all test concentrations except the 100% concentration caused slight irritation of the skin. It was unclear if good skin contact was achieved at the 100% concentration.

GLP compliance:

no

Type of study:

Buehler test

Justification for non-LLNA method:

The study was performed before the adoption of the OECD test guideline (OECD 429) in 2010

Species:

guinea pig

Strain:

Hartley

Sex:

male

Route:

epicutaneous, occlusive

Vehicle:

other: ethanol and deionized water

Concentration / amount:

50% suspension in 80% ethanol and deionized water (0.4 ml)

Day(s)/duration:

0, 7, 14

Adequacy of induction:

not specified

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: ethanol and deionized water

Concentration / amount:

50% suspension in 80% ethanol and deionized water (0.4 ml)

Day(s)/duration:

Day 27

Adequacy of challenge:

not specified

No. of animals per dose:

A total of 30 adult male Hartley albino guinea pigs were assigned to one of four groups: pencycuron test group (15 animals), pencycuron negative-induction control group (five animals), l-chloro-2, 4-dinitrobenzene (DNCB - positive control) test group (five animals) and DNCB negative-induction control group (five animals).

Details on study design:

The pencycuron was administered as a 50% suspension in 80% ethanol and deionized water (0.4 ml). Animals in the test groups received three topical induction applications of the appropriate formulation on study days 0, 7 and 14, followed by a 13-day "rest" period and a challenge application on day 27. Animals in the two negative-induction control groups (pencycuron and DNCB) received only the challenge dose on day 27. All induction and challenge sites were scored for erythema at approximately 24 and 48 hours after removal of the test substance. Two calculations were used to estimate the response following the challenge dose. The first, incidence, was defined as the number of animals showing responses of one or greater at either 24 or 48 hours divided by the number of animals tested. The second, severity, was defined as the mean of the test grades at 24 and 48 hours.

Positive control substance(s):

yes

Remarks:

1-chloro-2, 4-dinitrobenzene (DNCB - positive control)

Positive control results:

Positive for sensitisation.

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

15

Remarks on result:

no indication of skin sensitisation

No erythema was observed at the dose site of any of the pencycuron test or control group animals after the challenge dose. The DNCB test animals had an incidence score of 1.0 and a severity score of 1.0 following the challenge dose. The DNCB produced no evidence of irritation at the dose site of the negative-induction control animals.

Interpretation of results:

study cannot be used for classification

Conclusions:

Acceptability
The study is considered unacceptable, because of the deviations from the guideline. It should be noted that for a correct classification and labelling in accordance with EC regulations, a maximisation test is preferred with regard to the assessment of dermal sensitisation potential.
Conclusions
The study is considered unacceptable.

Executive summary:

The potential for pencycuron to produce a dermal sensitization response was tested in guinea pigs using the Buehler Topical Closed-Patch Technique. A total of 30 adult male Hartley albino guinea pigs were assigned to one of four groups: pencycuron test group (15 animals), pencycuron negative-induction control group (five animals), l-chloro-2, 4-dinitrobenzene (DNCB - positive control) test group (five animals) and DNCB negative-induction control group (five animals). The pencycuron was administered as a 50% suspension in 80% ethanol and deionized water (0.4 ml). Animals in the test groups received three topical induction applications of the appropriate formulation on study days 0, 7 and 14, followed by a 13-day "rest" period and a challenge application on day 27. Animals in the two negative-induction control groups (pencycuron and DNCB) received only the challenge dose on day 27. All induction and challenge sites were scored for erythema at approximately 24 and 48 hours after removal of the test substance. Two calculations were used to estimate the response following the challenge dose. The first, incidence, was defined as the number of animals showing responses of one or greater at either 24 or 48 hours divided by the number of animals tested. The second, severity, was defined as the mean of the test grades at 24 and 48 hours.
No erythema was observed at the dose site of any of the pencycuron test or control group animals after the challenge dose. The DNCB test animals had an incidence score of 1.0 and a severity score of 1.0 following the challenge dose. The DNCB produced no evidence of irritation at the dose site of the negative-induction control animals.
This negative response to a challenge dose indicates that pencycuron does not cause dermal sensitization. However the study is considered unacceptable, because of the deviations from the guideline. It should be noted that for a correct classification and labelling in accordance with EC regulations, a maximisation test is preferred with regard to the assessment of dermal sensitisation potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The Maximisation study is considered key as this method is generally considered to be more sensitive than the Buehler method (supporting), although both designs are scientifically valid.  These two in vivo studies were performed prior to the validation and adoption of alternative methods.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Guideline-compliant studies of skin sensitisation in the Guinea pig (Buehler and Maximisation designs) both show a lack of skin sensitisation for pencycuron.  Pencycuron does not have a harmonised classification for skin sensitisation.  The negative results in both studies show that pencycuron does not require classification for skin sensitisation in any CLP category.

No data are available for respiratory sensitisation.