Registration Dossier

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Report Date:
2015

Materials and methods

Principles of method if other than guideline:
Chromosome aberrations in vivo composite predictions were generated employing Leadscope Model Applier, ACD/Percepta, Toxtree.
GLP compliance:
no
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
other: rodent

Results and discussion

Test results
Genotoxicity:
negative
Toxicity:
not specified

Any other information on results incl. tables

 Leadscope  ACD/Percepta  Toxtree  Consensus prediction
 NEGATIVE Little reliable  -  POSITIVE Not reliable  NEGATIVE Little reliable
 Leadscope  LeadscopePositivePredictionprobability  ModelFeaturesCount  30% Sim.TrainingNeighborsCount
NEGATIVE (Little reliable) 0.04 18  1

         

Model Features Count. Parameter used to verify that the target compound, i.e.2-phenyl-2-piperidin-2-ylacetamide, contains a significant number of features that are present in the prediction model. The structural features used to make the prediction provide information on the reliability of the prediction: a prediction provided by a low number of features means that the model is not able to fully describe the test compound, while a prediction supported by a high number of features reveals that the test compound is well described by the model. Since 18 features were found, it was concluded that 2-phenyl-2-piperidin-2-ylacetamide is well represented by the model.

30% Similarity Training Neighbours Count. Number of compounds structurally similar to the target, in the model's training set of compounds. Another way to assess the reliability of the prediction is looking at the analogues, i.e. the compounds structurally similar to the target in the model's training set of compounds. While this information does not take part to the prediction, it provides the user a complementary means to see how similar compounds were predicted and what the experimental values of similar compounds are. Look at analogues is also an initial, less-sophisticated easy way to understand estimate of toxicity. Only one compound, illustrated in the Table, was identified in the training set as analogue to 2-phenyl-2-piperidin-2-ylacetamide being characterized bylittle similarity with respect to the target. Therefore, the prediction was considered of little reliability.

     

Phenacemide Result: negative Similarity: 0.31

ACD/Percepta did not provide any prediction for the target 2-phenyl-2-piperidin-2-ylacetamide since it resulted to be out of the model applicability domain.

Toxtree predicts the positive or negative micronucleus activity according to decision rules based on the identification of Structural Alerts (SA) for based on the rules, published in the document “Development of structural alerts for thein vivomicronucleus assay in rodents”, by Romualdo Benigni, Cecilia Bossa, Olga Tcheremenskaia and Andrew Worth, European Commission report EUR 23844 EN. As one or more SAs embedded in a molecular structure are recognised, the system flags the potential micronucleus activity of the chemical. Toxtree identified in the target 2-phenyl-2-piperidin-2-ylacetamide the H-acceptor-path3-H-acceptor structural alert.TheH-acceptor-path3-H-acceptoralert explores the possibility that a chemical interacts with DNA and/or proteins via non-covalent binding, such as DNA intercalation or groove-binding[1]. Among the descriptors potentially accounting for non-covalent interactions, the molecular framework representing two bonded atoms connecting two H bond acceptors (calculated with software Leadscope Enteprise 2.4.15-6) resulted in an increased sensitivity/specificity for what concerns the Micronucleus training set.

It has to be noted that this alert is one of Toxtree alert with the lowest percentage of true positive (34%). Since the identified alert is characterized by a very low percentage of true positive, it was concluded that the alert is not sufficient to provide a reliable positive prediction of micronucleus activity for the target 2-phenyl-2-piperidin-2-ylacetamide.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative with little reliability
Micronucleus in vivo on rodent of the target was estimated by using three predictors: Leadscope Model Applier, ACD/Percepta and Toxtree decision rule system. The three predictors were employed in order to apply a consensus approach to enhance the reliability of the prediction. In the consensus assessment only reliable predictions are to be taken into account. In the case of the target, the consensus assessment was based only on Leadscope prediction concluding that the target 2-phenyl-2-piperidin-2-ylacetamide is NEGATIVE, although the prediction is of little reliability.