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EC number: 255-207-0 | CAS number: 41078-70-0
In silico, in chemico and in vitro data are used in a weight-of-evidence approach. In addition, the Local Lymph Node Assay (LLNA) is added as key study.
- In silico: A Derek Nexus assessment yielded an alert for skin sensitisation based on the presence of an Alkyl halide group (Alert 413) and predicted an EC3 of 0.075% (Van Gompel, 2017).
- In chemico (OECD 442C): The test item was considered to be positive in the DPRA and classified in the “moderate reactivity class” when using the Cysteine 1:10 prediction model (Rijk, 2018).
- In vitro (OECD 442D): The KeratinoSensTM assay yielded a positive result (Westerink, 2018).
Taking into account the positive in silico, in chemico and in vitro results and as it is not possible to determine the potency (Cat. 1A or 1B) based on non-animal testing approaches, as required in Annex VII, section 8.3, additional in vivo testing (Local Lymph Node Assay in mice according to OECD 429) was performed to assess the potency of the test item (van Sas, 2018).
- In vivo (OECD 429): Based on the results of a local Lymph Node Assay in female CBI/J mice the test item was regarded as a skin sensitizer category 1B
At a concentration of 100 mM, the test item was not soluble (precipitation) in ACN and MQ, but was soluble in MQ/ACN (1:1, v/v). Therefore this solvent was used to dissolve the test item in this DPRA study.
Results cysteine reactivity assay for the test item:
Preparation of a 100 mM test item stock solution in MQ/ACN (1:1, v/v) showed that the test item was dissolved completely.
Upon preparation and after incubation, both the co-elution control (CC) as well as the test item samples were visually inspected. No precipitate was observed in any of the samples.
In the CC sample no peak was observed at the retention time of SPCC. This demonstrated that there was no co-elution of the test item with SPCC. For the test item samples, the mean SPCC A220/A258 area ratio was 19.04 which was within the 15.77 -19.27 range (mean A220/A258 ratio ± 10% range of Reference controls A, B and C). This again indicated that there was no co-elution of the test item in SPCC.
Results lysine reactivity assay for the test item:
Preparation of a 100 mM test item stock solution in MQ/ACN (1:1, v/v) showed that the test item dissolved completely. Upon preparation and after incubation, both the CC as well as the test item samples were visually inspected. Upon preparation as well as after incubation a precipitate was observed in the CC and the test item samples. In this case one cannot be sure how much test item remained in the solution to react with the peptide. Consequently, the peptide depletion might be underestimated.
In the CC sample a peak/interference was observed at the retention time of SPCL. For the test item samples, the mean SPCL A220/A258 area ratio was 8.28. Since this was outside the 12.22 -14.93 range (mean A220/A258 ratio ± 10% range of Reference controls A, B and C), this
again indicated that there was co-elution of the test item with SPCL and therefore no SPCL Depletion value could be calculated.
SPCC and SPCL depletion, DPRA prediction and reactivity classification of the test item:
SD = Standard Deviation; NA = not applicable
Historical control data for DPRA studies
SD = Standard Deviation, n = Number of observations
The above mentioned historical control data were collected over the period of January 2017 to August 2017.
Test item results
- No precipitation was observed at the start and end of the incubation period in the 96-well plates.
- The test item showed toxicity. The calculated IC30 was 730 μM and the calculated IC50 was 902 µM.
- A dose related luminescence activity induction was observed after treatment with the test item. The Imax was 37 and the EC1.5 279 μM.
-The test item showed toxicity. The calculated IC30 was 992 μM and the calculated IC50 was 1388 µM.
- A dose related luminescence activity induction was observed after treatment with the test item. The Imax was 21 and the EC1.5 405 μM.
Historical Control Data for the KeratinoSensTM Studies:
SD = Standard Deviation; n = Number of observations
The above mentioned historical control data range of the controls were obtained by collecting all data over the period of May 2016 to December 2017.
Skin sensitisation in mammal is PLAUSIBLE
Alert matched: 413 Alkyl halide
Potential mechanism: Hapten acting as an SN2 - reactive electrophile [Aptula and Roberts]
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A collection of guinea pig sensitization test results grouped by chemical class., Drug and Chemical Toxicology, 4, 331-351
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Structure activity relationships in skin sensitization using the murine local lymph node assay., Toxicology, 103 , 177-194
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Xenobiotics as skin sensitisers: metabolic activation and detoxication, and protein-binding mechanisms., Allergic Contact Dermatitis: Chemical and Metabolic Mechanisms, , 119-205
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The value of the local lymph node assay in the development of QSARs for skin sensitization potential., Trends in QSAR and Molecular Modelling 92: 9th European Symposium on Structure-Activity Relationships: QSAR and Molecular Modelling: Papers and Summaries, , 580-583
- European Chemical Agency (ECHA). (2009)
Skin sensitisation study for 1-bromopentane (CAS No. 110-53-2)., European Chemicals Agency Registration Dossier,
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Skin sensitisation study for 1,6-dibromohexane (CAS No. 629-03-8)., European Chemicals Agency Registration Dossier
- Siegel PD, Fedorowicz A, Butterworth L, Law B, Anderson SE, Snyder J and Beezhold D. (2009)
Physical-chemical and solvent considerations in evaluating the influence of carbon chain length on the skin sensitization activity of 1-bromoalkanes., Toxicological Sciences, 107 , 78-84
- Natsch A, Ryan CA, Foertsch L, Emter R, Jaworska J, Gerberick F and Kern P. (2013)
A dataset on 145 chemicals tested in alternative assays for skin sensitization undergoing prevalidation., Journal of Applied Toxicology, 33 , 1337-1352
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A prospective study of cutaneous intolerance to topical mechlorethamine therapy in patients with cutaneous T-cell lymphomas., Archives of Dermatology, 135 , 1349-1353
- Aptula AO and Roberts DW. (2006)
Mechanistic applicability domains for nonanimal-based prediction of toxicological end points: general principles and application to reactive toxicity., Chemical Research in Toxicology, 19 , 1097-1105
· Baeck M, Chemelle JA, Terreux R, Drieghe J and Goossens A. (2009)
Delayed hypersensitivity to corticosteroids in a series of 315 patients: clinical data and patch test results., Contact Dermatitis, 61 , 163-175
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Mechanistic relationship among mutagenicity, skin sensitization, and skin carcinogenicity., Environmental Health Perspectives, 101 , 62-67
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Failure to induce immune tolerance to nitrogen mustard. Intravenous administration preceding topical use in patients with proriasis., Journal of Investigative Dermatology, 58 , 1-4
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Skin sensitisation: guinea pig maximisation test, local lymph node assay
The alert has demonstrated the following predictive performance:
1) Cronin and Basketter: 0 compounds activate this alert.
2) Gerberick: 19 compounds activate this alert of which 15 are reported positive. (Positive predictivity: 79%.)
3) Contact Dermatitis: 11 compounds activate this alert of which 5 are reported positive. (Positive predictivity: 45%.)
1) A collection of guinea pig maximisation test data for 216 compounds from the following reference: Cronin MTD and Basketter DA. Multivariate QSAR analysis of a skin sensitization database. SAR and QSAR in Environmental Research, 1994, 2, 159-179, available at "http://dx.doi.org/10.1080/10629369408029901".
2) A collection of local lymph node assay data for 318 compounds derived from the following references: (i) Gerberick GF, Ryan CA, Kern PS, Schlatter H, Dearman RJ, Kimber I, Patlewicz GY and Basketter DA. Compilation of historical local lymph node data for evaluation of skin sensitization alternative methods. Dermatitis, 2005, 16, 157-202. Downloaded from "http://www.inchemicotox.org/results/" (3 September 2010); (ii) Kern PS, Gerberick GF, Ryan CA,
Kimber I, Aptula A and Basketter DA. Local lymph node data for the evaluation of skin sensitization alternatives: a second compilation. Dermatitis, 2010, 21, 8-32, available at “http://dx.doi.org/10.2310/6620.2009.09038”.
3) A collection of local lymph node assay data for 137 compounds published in Contact Dermatitis which have been extracted from Vitic Nexus (13 September 2012).
EC3 Result for Derek EC3 Model - 1.0.5:
Predicted LLNA EC3: 0.075% (extreme sensitiser)
Experimental Match: No exact match found
Compounds used in calculation: 10/36
In silico, in chemico and in vitro data are used in a weight-of-evidence approach. The studies are discussed in detail in the Weight-of-Evidence justification attached to this endpoint summary.
In addition, the Local Lymph Node Assay (LLNA) is added as key study.
In the main study, three experimental groups of five female CBA/J mice were treated with test item concentrations of 2, 10 or 25% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with vehicle alone (Propylene glycol).
Three days after the last exposure, all animals were injected with 3H-methyl thymidine and after five hours the draining (auricular) lymph nodes were excised and
pooled for each animal. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of Disintegrations Per Minute (DPM) and a stimulation index (SI) was subsequently calculated for each group. No irritation of the ears was observed in any of the animals examined. White test item remnants were present on the dorsal surface of the ears of all animals treated at 10% and 25% between Days 1 and 3, which did not hamper scoring of the skin reactions.
No irritation of the ears was observed in any of the animals examined. White test item remnants were present on the dorsal surface of the ears of all
animals treated at 10% and 25% between Days 1 and 3, which did not hamper scoring of the skin reactions. No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period.
All auricular lymph nodes of the animals of the experimental and control groups were considered normal in size. No macroscopic abnormalities of the surrounding area were noted for any of the animals.
Mean DPM/animal values for the experimental groups treated with test item concentrations 2, 10 and 25% were 937, 1026 and 2205 DPM, respectively. The
mean DPM/animal value for the vehicle control group was 610 DPM. The SI values calculated for the item concentrations 2, 10 and 25% were 1.5, 1.7 and 3.6,
These results indicate that the test item could elicit a SI ≥ 3. The data showed a dose-response and an EC3 value (the estimated test item concentration that will give a SI =3) of 20.3% was calculated.
Taking into account the positive in silico, in chemico and in vitro results and as it is not possible to determine the potency (Cat. 1A or 1B) based on non-animal testing approaches, as required in Annex VII, section 8.3, additional in vivo testing (Local Lymph Node Assay in mice according to OECD 429) was performed to assess the potency of the test item.
Based on the results of a local Lymph Node Assay in female CBI/J mice the test item was regarded as a skin sensitizer category 1B.
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