2-heptadecyl-1H-imidazole

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 May 2018 to 05 July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

2010

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Version / remarks:

2008

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Version / remarks:

2003

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP-Landesleitstelle Bayern, Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Schwabach, Germany

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

1

Reference substance name:

2-heptadecyl-1H-imidazole

EC Number:

245-589-7

EC Name:

2-heptadecyl-1H-imidazole

Cas Number:

23328-87-2

Molecular formula:

C20H38N2

IUPAC Name:

2-heptadecyl-1H-imidazole

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/CaOlaHsd

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Envigo (formed partially from Harlan in September 2015), 5800 AN Venray, The Netherlands
- Females nulliparous and non-pregnant: yes
- Microbiological status of animals, when known: SPF
- Age at study initiation: 8-9 weeks
- Housing: the animals were kept in groups of 5 animals in IVC cages, type II L, polysulphone cages on Altromin saw fibre bedding
- Diet: Altromin 1324 maintenance diet, ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least five days
- Indication of any skin lesions: none

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%):55 ± 10
- Air changes (per hr): at least 10
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (LLNA)

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

3%, 6.25% and 12.5% (w/v)

No. of animals per dose:

5

Details on study design:

PRE-SCREEN TESTS: two animals per dose were treated by topical application with the test item on three consecutive days at concentrations of 6.25 and 12.5 % in acetone/olive oil 4:1 (AOO) to the entire dorsal surface of each ear. One further animal was treated with 100 % AOO and served as negative control.
- Compound solubility: the vehicle was chosen as it was suitable at the highest concentration.
- Irritation: the mice were observed daily for local skin irritation to the application site.
- Systemic toxicity: the mice were observed daily for any clinical signs of systemic toxicity, and body weights were recorded pre-test and prior to termination.
- Ear thickness measurements: performed on day 1 (pre-dose), day 3 (approximately 48 hours after the first dose) and day 6.
- Erythema scores: No erythema (0), very slight erythema (1), well-defined erythema (2), moderate to severe erythema (3), severe erythema to eschar formation preventing grading of erythema (4).

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: 3H-methyl thymidine (3HTdR) incorporation determined by β-scintillation counting
- Criteria used to consider a positive response: A substance is regarded as a “sensitizer” in the LLNA if at least one concentration of the test item results in a 3-fold or greater increase in 3HTdR incorporation into lymph node cells of the test group animals, relative to that recorded for the lymph nodes of control group animals. Any test item failing to produce a 3-fold or greater increase in 3HTdR incorporation is classified as a "non-sensitizer".
If the results allowed the EC3 value could also be calculated. The EC3 value is the concentration of test item expected to cause a 3-fold increase in 3HTdR incorporation. The equation used for the calculation of EC3 is:
EC3 = c + [[(3-d)/(b-d)] x (a-c)]
a = lowest concentration giving stimulation index >3
b = actual stimulation index caused by 'a'
c = highest concentration failing to produce a stimulation index of 3
d = actual stimulation index caused by 'c'

- Other: The animals were observed for signs of toxicity prior to the application and once daily after treatment. The body weight was recorded prior to the application and at the end of the test period (prior to the treatment with 3HTdR).

TREATMENT PREPARATION AND ADMINISTRATION: 25 μL of the test compound in concentrations of 3%, 6.25% and 12.5% (w/v) in AOO and negative control (AOO) was applied to the dorsal surface of each ear of each mouse on Day 1, 2 and 3. On Day 6 an injection of 250 μL phosphate buffered saline (PBS) containing 20 μCi of 3H-methyl thymidine (3H-TdR) was made into the tail vein of each experimental mouse. Five hours later, the draining auricular lymph node of each ear was excised into PBS. A single cell suspension of pooled lymph node cells was prepared per experimental group by gentle mechanical disaggregation through a 200-mesh stainless steel gauze and rinsed with PBS. The precipitates were incubated for approximately 18 h at approximately 4 °C, centrifuged, resuspended in 1 mL 5% TCA (trichloroacetic acid) and transferred to 7 mL scintillation fluid before β-scintillation counting.

Positive control substance(s):

other: Phenylene- diamine

Results and discussion

Positive control results:

A positive control was performed concomitantly using 5 animals, the result showed the positive-control substance exceeded the stimulation index of 3 confirming the reliability of the test system.

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

SI

Value:

ca. 1

Test group / Remarks:

3%

Results 2

Key result

Parameter:

SI

Value:

ca. 1.2

Test group / Remarks:

6.25 %

Results 3

Key result

Parameter:

SI

Value:

ca. 1.4

Test group / Remarks:

12.5 %

Cellular proliferation data / Observations:

DETAILS ON STIMULATION INDEX CALCULATION
The SI of the 3, 6.25 and 12.5 % treatment group was 1.0, 1.2 and 1.4, respectively.

EC3 CALCULATION
The EC3 value could not be calculated as the stimulation indices of all concentrations were below 3.

CLINICAL OBSERVATIONS:
All animals survived throughout the test period without showing any clinical signs.

BODY WEIGHTS
All animals showed the expected weight development, which includes a weight loss of up to 2 g throughout the study.

Any other information on results incl. tables

Table 1: Radioactive Determination of the Test Substance Groups – Main Study

POS	CPM	Test Item	Conc. [%]	Animal Number	DPM	DPM-mean background	DPM / Node	Stimulation Index
51	8.0	Background Scinti and TCA			14.0
52	6.0				11.0
53	6.0				12.0
54	6.0				12.0
55	9.0				17.0
MV	7.0			MV	13.2	0.0	0.0	0.0
SD	1.3			SD	2.1
26	1429.0	C17Z in AOO	3	1	2866.0	2852.8	1426.4	0.9
27	1424.0			2	2857.0	2843.8	1421.9	0.9
28	1771.0			3	3556.0	3542.8	1771.4	1.1
29	1693.0			4	3405.0	3391.8	1695.9	1.1
30	1087.0			5	2178.0	2164.8	1082.4	0.7
MV	1480.0			MV	2972.4	2959.2	1479.6	1.0
SD	240.9			SD	486.5	486.5	243.3	0.2
31	1868.0	C17Z in AOO	6.25	6	3747.0	3733.8	1866.9	1.2
32	1638.0*			7	3297.0*	n.d.	n.d.	n.d.
33	1769.0			8	3553.0	3539.8	1769.9	1.1
34	1909.0			9"	3842.0	3828.8	1914.4	1.2
35	1876.0			10	3784.0	3770.8	1885.4	1.2
MV	1855.5			MV	3731.5	3718.3	1859.2	1.2
SD	52.3			SD	108.5	108.5	54.2	0.0
36	1878.0	C17Z in AOO	12.5	11	3817.0	3803.8	1901.9	1.2
37	1955.0			12	3926.0	3912.8	1956.4	1.3
38	2677.0			13	5395.0	5381.8	2690.9	1.7
39	1494.0			14	3010.0	2996.8	1498.4	1.0
40	2539.0			15	5121.0	5107.8	2553.9	1.6
MV	2108.6			MV	4253.8	4240.6	2120.3	1.4
SD	438.8			SD	883.1	883.1	441.6	0.3
41	1335.0	Negative Control AOO	100	101	2676.0	2662.8	1331.4
42	1339.0			102	2690.0	2676.8	1338.4
43	1632.0			103	3274.0	3260.8	1630.4
44	1811.0			104	3657.0	3643.8	1821.9
45	1657.0			105	3328.0	3314.8	1657.4
MV	1554.8			MV	3125.0	3111.8	1555.9	1.0
SD	188.1			SD	384.0	384.0	192.0

POS = position in counter; CPM = counts per minute; Conc. = concentration; DPM = disintegrations per minute; * = outlier, failed Nalimov; n.d. = not determined; MV = mean value; SD = standard deviation; Szinti = scintillation fluid; TCA = trichloroacetic acid

If not noted individually, the results include both lymph nodes of an animal.

Applicant's summary and conclusion

Interpretation of results:

other: CLP/EU GHS criteria not met, no classification required according to Regulation (EC) No 1272/2008.

Conclusions:

Consequently, according to OECD 429 the test item C17Z as described in this report is expected to have no sensitising properties and therefore should not be regarded as a dermal sensitiser.
According to Commission Regulation (EU) No 286/2011 as well as GHS (Globally Harmonized Classification System) the test item C17Z has no obligatory labelling requirement for skin sensitisation and is unclassified.

Executive summary:

The test item C17Z was tested in a Local Lymph Node Assay (LLNA) in mice according to OECD guideline 429 and EU method B.42.

Three groups each of five female mice were treated with 3, 6.25 or 12.5% (w/v) test item concentration by topical application at the dorsum of each ear on three consecutive days. One negative control group was treated with the respective vehicle only (4:1 (v/v) acetone / olive oil).

The animals did not show any signs of systemic toxicity during the course of the study and no cases of mortality were observed.

Signs of local irritation (e.g. reddening of the ear skin, ear swelling) were also not observed during the study period.

A statistically significant increase in body weights was not observed in any of the groups treated with different concentrations of the test item in comparison to the vehicle control group.

Here, Stimulation Indices (S.I.) were determined with the test item at concentrations of 3, 6.25 and 12.5% (w/v) in AOO (4:1 (v/v) acetone/oliveoil), respectively.

A statistically significant difference in DPM/animal was not observed in any of the groups treated with different concentrations of the test item in comparison to the vehicle control group.

The EC3 value could not be calculated, since none of the tested concentrations induced an S.I. greater than 3.The S.I. of the positive control group was 4.0.

The test item C17Z did not show skin sensitizing potential in this assay under the conditions of this study.