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Skin sensitisation

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Administrative data

skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
See Principles of method if other than Guideline. Based on laboratory historical data, these fluctuations were considered not to have affected the study integrity.
Principles of method if other than guideline:
1. Temporary deviations from the minimum level of relative humidity occurred. Evaluation: Laboratory historical data do not indicate an effect of the deviations.
2. For animal nos. 21-25, the concurrent vehicle control group from project 439425 was used instead from project 439414. Evaluation: Project 439414 did not contain a vehicle control group. The control animals of Notox Project 439425 were treated within the same time frame as this study, using the same procedures and the same batch of vehicle, animals and 3H-methyl thymidine.
GLP compliance:
Type of study:
mouse local lymph node assay (LLNA)

Test material

Test material form:

In vivo test system

Test animals

inbred, SPF-Quality
Details on test animals and environmental conditions:
Source: Charles River France, L'Arbresle Cedex, France

25 femals (five groups of five females each group) (nulliparous and non-pregnant).
Young adult animals (approx. 11 weeks old) were selected. Body weight variation was within +/- 20% of the sex mean.

Identification: Tail mark with marker pen.

Animals were housed in a controlled environment, in which optimal conditions were considered to be approximately 15 air changes per hour, a temperature of 21.0 +/- 3.0 oC (actual range: 18.6-22.7 oC), a relative humidity of 30-70% (actual range 23-83%) and 12 hours artificial fluorescent light and 12 hours darkness per day. Cleaning procedures in the room might have caused the temporary fluctuations above the optimal maximum level of 70% for relative humidity. Based on laboratory historical data, these fluctuations were considered not to have affected the study integrity.

Individual housing in labeled Macrolon cages (MI type: height 12.5 cm) containing sterilized sawdust as bedding material (Woody-Clean type 3/4: Tecnilab-BMIBV, Someren, The Netherlands).

Acclimatization period:
The acclimatization period was at least 5 days before the start of treatment under laboratory conditions. Accomodation was as described above except that the animlas were group housed in Macrolon cages (MIII type: height 15 cm). Paper (Enviro-dri, BMI, Helmond, The Netherlands) was supplied as cage-enrichment.

Free access to standard pelletized laboratory animal diet (code VRF 1, Altromin, Lage, Germany).

Free access to tap water.

Study design: in vivo (LLNA)

acetone/olive oil (4:1 v/v)
The vehicle was selected based on trial formulations performed at Notox and on test substance data supplied by the sponsor.
10, 50 and 100 %
No. of animals per dose:
Five groups of five females each group
Details on study design:
Preliminary irritation study:
A preliminary irritation study was conducted in order to select the highest test substance concentration to be used in the main study. In principle, this concentration should be well tolerated systemically by the animals and may give moderate irritation (grade 2) at the highest.

Main study:
Initially, three groups of five animals were treated with one test substance concentration each group (10 %, 50 % and 100 % test substance, respectively). One group of five animals was treated with vehicle. Based on the results, one additional group was treated with the undiluted test substasnce.

Induction - Days 1, 2 and 3:
Experimental animals:
The dorsal surface of both ears was epidermally treated (25 ml/ear) with the test substance concentration, at approximately the same time each day.

Vehicle control animals:
The control animals were treated the same as the experimental animals, except that, instead of the test substance, the vehicle alone was administered.

Treatment - Day 6:
All animals:
Each animal was injected via the tail vein with 0.25 ml of sterile phosphate buffered saline (PBS) (Merck, Darmstadt, Germany) containing 20 uCi of 3H-methyl thymidine (Amersham Biosciences, Buckinghamshire, UK).

After approximately five hours, all animals were killed by intra peritoneal injection wtih pentobarbital (0.2 ml/animal Euthesate; Sanofi Sante B.V., Maassluis, The Netherlands). The draining (auricular) lymph node of each ear was excised. The relative size of the nodes (as compared to normal) was estimated by visual examination and abnormalities of the nodes and surrounding area were recorded. The nodes were pooled for each animal in approximately 3 ml PBS.

Tissue processing for radioactivity - Day 6:
A single cell suspension of lymph node cells (LNC) was prepared in PBS by gentle separation through stainless steel gauze (diameter 125 um). LNC were washed twice with an excess of PBS by centrifugation at 200g for 10 minutes at 4o C. The DNA was precipitated with 3 ml 5% trichloroacetic acid (TCA) (Merck, Darmstadt, Germany) at 4 oC. Precipitates were recovered by centrifugation, resuspended in 1 ml TCA and transferred to 10 ml of Ulitma Gold cocktail (Packard Bioscience B.V., Groningen, The Netherlands) as the scintillation fluid.

Radioactivity measurements - Day 7:
All radioactive measurements were performed using a Packard scintillation counter (1900TR). Counting time was to a statistical precision of +/- 0.2% or a maximum of 5 minutes whichever comes first. The Packard 1900TR was programmed to automatically subtract background and convert Counts Per Minute (CPM) to Disintegrations Per Minute (DPM).

Results and discussion

In vivo (LLNA)

Key result
1.3 @ 10 %, 2.4 @ 50 % and 2.7 @ 100 %
Remarks on result:
no indication of skin sensitisation based on QSAR/QSPR prediction
DEREK insilico SAR results

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Based on these results, it was concluded that there was no indication that the test substance could elicit an SI >= 3 when tested up to 100 %. This result was corroborated by the outcome of the unvalidated DEREK insilico SAR results, that showed the absence of structural alerts indicative for skin sensitisation.

Based on these results, pentamethyl-trioxepane would not be regarded as skin sensitizer, does not have to be classified for sensitisation by skin contact and has no obligatory labeling requirement for sensitisation by skin contact.
Executive summary:

Based on these results, pentamethyl-trioxepane would not be regarded as skin sensitizer, does not have to be classified for sensitisation by skin contact and has no obligatory labeling requirement for sensitisation by skin contact.