5-amino-2-nitrobenzoic acid

Endpoint summary

Description of key information

-   DEREK NEXUS version 6.0.1 did yield a skin sensitization alert for 5-amino-2-nitrobenzoic acid (CAS 13280-60-9) based on the presence of an aromatic primary amine and predicted 5-amino-2-nitrobenzoic acid to be sensitizing to the skin (plausible). The potential mechanism behind the alert is that the primary amine can oxidize and/or metabolize into species capable of reacting with a skin protein nucleophilic group.

DEREK NEXUS predicted an EC3 of 11% (weak sensitizer) for 5-amino-2-nitrobenzoic acid based on LLNA data from ten structurally related analogues (structural similarity of 28 - 59%). The query compound contains a primary amine with a para-substituted nitro group and a meta substituted carboxylic acid group. This substitution pattern with regard to the amine is not found within its closest structurally related analogues. As the substitution pattern of a benzene ring is important in its reactivity, this mismatch in substitution pattern makes the accuracy of the EC3 prediction uncertain.

 

- A valid DPRA assay was performed according to OECD 442C and GLP principles. The test item was dissolved 1:1 mixture of acetonitrile:ultrapure water at 100 mM and incubated with the cysteine- and lysine-containing synthetic peptides. No precipitate was observed in any of the samples. The mean percent cysteine-peptide depletion for the test item was 42.87 % ± 9.08 % and the mean percent lysine-peptide depletion was 0.92 % ± 0.34 %. The mean peptide depletion of the test item was 21.90 %, which exceeded the 6.38 % threshold of the applicable prediction model and fell into the low reactivity class. Therefore, the test item is considered to be positive and to show low reactivity towards the synthetic peptides and is thus a potential skin sensitizer when using the Cysteine 1:10/Lysine 1:50 prediction model.

 

- A valid KeratinosensTM assay was performed according to OECD 442D and GLP principles. The test item was suspended in DMSO at a final concentration of 200mM. Based on the test item stock solutions made of DMSO, 2-fold serial dilutions were made using the solvent to obtain twelve 100 × master concentrations of the test item, 5 100 × master concentrations of the positive control and six 100 × master concentrations of the negative (solvent) control. The master concentrations were diluted 25-fold with exposure medium. These solutions were diluted 4-fold in the assay resulting in test concentrations of 0.98 – 2000 µM. No precipitate was observed at any dose level tested. Two independent experiments were performed.

The test item showed no cytotoxicity. No biologically relevant induction of the luciferase activity (no EC1.5 value) was measured at any of the test concentrations in both experiments. The maximum luciferase activity induction (Imax) was 1.13-fold and 1.09-fold in experiment 1 and 2, respectively. The test item is classified as negative in the KeratinoSensTM assay since negative results (<1.5-fold induction) were observed at any test concentrations up to 2000 µM. 5-Amino-2-Nitrobenzoic Acid (CAS 13280-60-9) is classified as negative (no activation of the antioxidant/electrophile responsive element (ARE)-dependent pathway in keratinocytes) under the experimental conditions described in this report.

 

- A valid h-CLAT assay was performed according to OECD 442E. The test item was dissolved in DMSO at a final concentration of 500 mg/mL and no precipitation was observed. The test item solution was mixed with the suspended THP-1 cells in a 1:1 ratio as a single replicate and incubated 24 +/- 0.5h. After exposure to the test item, potential upregulation of the CD86 and CD54 cell surface markers were quantified by FITC-staining of the surface markers and analysis by Flow Cytometry.

The increase in CD86 marker expression (RFI) was lower than 150 % at all tested doses and the increase in CD54 marker expression (RFI) was lower than 200 % at all tested doses with > 50 % of cell viability compared to the respective negative controls in all valid runs. Based on the valid negative results, both CD86 and CD54 marker expressions were concluded to be negative and effective concentration for CD86 and CD54 expressions (EC150 and EC200, respectively) were not determined.

Since the CD86 and CD54 markers gave negative results in both independent runs, the overall h-CLAT prediction for 5-Amino-2-Nitrobenzoic Acid (CAS 13280-60-9) was concluded to be negative.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Justification for classification or non-classification

The QSAR DEREK assay predicted 5-amino-2-nitrobenzoic acid (CAS 13280-60-9) to be sensitizing to the skin due to a skin sensitization alert for the test item based on the presence of an aromatic primary amine (plausible). The DPRA demonstrated that 5-Amino-2-Nitrobenzoic Acid binds to cysteine residues and the assay predicted the test item to be a weak sensitizer using the lysisne/cysteine prediction model. However, both the KeratinoSensTM assay as well as the h-CLAT assay gave clear negative results.  Based on the “two out of three” approach for the identification of sensitizing chemicals and because clear negative results were obtained for two of the 3 first key events of the Adverse Outcome Pathway, the test substance 5-Amino-2-Nitrobenzoic Acid (CAS 13280-60-9) can be concluded to be negative for skin sensitization. Therefore, the substance does not have to be classified for skin sensitization according to Regulation EC No 1272/2008 and amendments.