1-Ethoxy-2,3-difluoro-4-(trans-4-pentylcyclohexyl)-benzene

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

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

Adequacy of study:

key study

Study period:

May 03 - Jul 24, 2007

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: For this endpoint information from a structural similar compound is available. This study for this similar compound was performed according to GLP and the methods applied are fully compliant with OECD TG 429.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS- Source: Harlan Netherlands B.V. Postbus 6174 NL - 5960 AD Horst - Age at study initiation: 7 - 8 weeks - Weight at study initiation: 18,5 +/- 1,0- Housing: single- Diet (e.g. ad libitum): ad libitum - Water (e.g. ad libitum): ad libitum - Acclimation period: 7 daysENVIRONMENTAL CONDITIONS- Temperature (°C): 22 + 3°C- Humidity (%): 30-88%- Photoperiod (hrs dark / hrs light): 12/12IN-LIFE DATES: From: day 1 To: day 5

Vehicle:

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

Concentration:

pre test for signs of irritation: 2.5, 5, 10 and 25 % (v/v)main test: 5, 10 and 25 % (v/v)

No. of animals per dose:

pre test: 2main test: 5 (f) per group (3 test groups, 1 control group) total 20 (f)

Details on study design:

RANGE FINDING TESTS:- Compound solubility: solubility in vehicle was demonstrated- Irritation: pre test performed- Lymph node proliferation response: no dataMAIN STUDYANIMAL ASSIGNMENT AND TREATMENT- Name of test method: OECD TG 429- Criteria used to consider a positive response: 3-fold greater response at one concentration in SI than control animals TREATMENT PREPARATION AND ADMINISTRATION:a) Topical application of 25 µL test item preparation (test group) or vehicle (control group)b) five days after topical application: iv application of 3H-methyl thymidin c) prior each treatment (a and b) ear thickness measurementd) five hours after treatment (b) necropsy and analysis of the 3H thymidin incorporation in draining lymph nodese) method: pooled per animal

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

Dunnets Test

Positive control results:

Conc. SI5%: 2.4310% 4.0725% 4.88

Parameter:

SI

Remarks on result:

other: Control: Hexylcinnamaldehyde2.5%: 2.435%: 4.0710% 4.88

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: DPM S.I.Control: 508.3 15%: : 930.0 1.8310%: 858.1 1.6925% 530.0 1.04

Interpretation of results:

GHS criteria not met

Remarks:

Migrated information

Conclusions:

From the data it can be concluded that the test item is not a skin sensitiser under the conditions of this assay.

Executive summary:

Study Design

In the study the test item was dissolved in acetone:olive oil (4+1) was assessed for its possible contact allergenic potential.
For this purpose a local lymph node assay was performed using test item concentrations of 5, 10, and 25%. The GLP study was performed according to OECD TG 429.

Results

The animals did not show any clinical signs during the course of the study and no cases of mortality were observed.
A relevant increase in ear thickness gain could not be observed after treatment with the test item.
In this study Stimulation Indices (S.I.) of 1.83, 1.69, and 1.04 were determined with the test item at concentrations of 5, 10, and 25% in acetone:olive oil (4+1), respectively. Since the S.I. was not increased above 3 at any test group.

Conclusion

From the data it can be concluded that the test item is not a skin sensitiser under the conditions of this assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Justification for read across

Endpoint:Skin Sensitisation

Type of read across:one-to-one

Test Compound (with data):CAS: 174350-05-1

Dossier Compound (without data):CAS: 124729-02-6

The read across is based on the following similarity measures:

(1) Chemical similarity:
The test compound (CAS: 174350-05-1) provides all main chemical features present in the dossier compound (CAS: 124729-02-6). Both substances share typical structural features for liquid crystals, i.e. one phenyl ring coupled via single bond to a cyclohexyl ring.

Comparing dossier and test compound yields the same substitution pattern at the phenyl ring, i.e. a Fluor substitution (dossier compound: n=2, test compound: n=2) and a para ethoxy substituent.

The cylohexyl ring of both compounds shows a para alkyl substitution of different chain length (dossier cpd.: n=5; test cpd.: n=3). Thus, the only difference in terms of chemical structure is the length of the alkyl chain connected to the core structure. Overall, this almost perfect match results in a high chemical similarity score of 1.00 (Tanimoto).

(2) Physicochemical similarity
The high chemical similarity yields almost identical physicochemical key parameters relevant for bioavailability as listed in the table below.

(3) Predictions for Skin Sensitisation using QSAR
The skin sensitisation potential of both compounds has been predicted using Derek Nexus version 2.0. EU JRC registered the QMRF with the registration number Q13-34-36-315. The detailed description is available online (http://qsardb.jrc.ec.europa.eu/qmrf/search_catalogs.jsp). Both predictions were negative supporting the assessment for this endpoint.

The table below lists the similarity measures applied for this read across.

Assay	Test Compound CAS: 174350-05-1	Dossier Compound CAS: 124729-02-6
Cyclohexyl phenyl core	yes	yes
Terminal alkyl chain at the cyclohexyl ring	yes (n=3)	yes (n=5)
Terminal alkoxy chain at the phenyl ring	yes (n=2)	yes (n=2)
Liquid crystalline properties	yes	yes
Fluor Substitution at the phenyl ring	yes (n=2)	yes (n=2)
Water solubility	130 µg/L (EU A.6)	30 µg/L (EU A.6)
logP	> 5.7 (OECD 117, EU A.8)	> 6.5 (OECD 117, EU A.8)
Derek QSAR Skin Sensitisation	negative	negative
Skin Sensitisation Assay	negative (OECD 429)	negative (Read Across)

Conclusion
The Dossier Compound shows a data gap for Skin Sensitisation; however, a chemical analogue provides data for this endpoint. Both the Dossier Compound and the Test Compound show a very high chemical similarity and almost identical physicochemical parameters leading to similar bioavailability. A prediction using the Derek Nexus Knowledge Base for Skin Sensitisation with a JRC certified QMRF yields negative predictions for both compounds.

Based on these finding it is justified to use the data from the chemical analogue (Skin sensitisation in vivo: negative (GLP, OECD TG 429)) to fill the data gap for the dossier compound.

Migrated from Short description of key information:
For this endpoint information from a structural similar compound is available. This study for this similar compound was performed according to GLP and the methods applied are fully compliant with OECD TG 429. This assay was negative and the data are read across to the target chemical.

Justification for selection of skin sensitisation endpoint:
This study was performed according to GLP and the methods applied are fully compliant with OECD TG 429.

Justification for classification or non-classification

According to the results of the sensitisation test, a classification and labelling is not required for this substance.