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Tetko, I.V. ; Sushko, I. ; Pandey, A.K. ; Zhu, H. ; Tropsha, A.* ; Papa, E.* ; Öberg, T.* ; Todeschini, R.* ; Fourches, D.* ; Varnek, A.*

Critical assessment of QSAR models of environmental toxicity against Tetrahymena pyriformis: Focusing on applicability domain and overfitting by variable selection.

J. Chem. Inf. Model. 48, 1733-1746 (2008)
DOI
Open Access Green as soon as Postprint is submitted to ZB.
The estimation of the accuracy of predictions is a critical problem in QSAR modeling. The "distance to model" can be defined as a metric that defines the similarity between the training set molecules and the test set compound for the given property in the context of a specific model. It could be expressed in many different ways, e.g., using Tanimoto coefficient, leverage, correlation in space of models, etc. In this paper we have used mixtures of Gaussian distributions as well as statistical tests to evaluate six types of distances to models with respect to their ability to discriminate compounds with small and large prediction errors. The analysis was performed for twelve QSAR models of aqueous toxicity against T. pyriformis obtained with different machine-learning methods and various types of descriptors. The distances to model based oil standard deviation of predicted toxicity calculated from the ensemble of models afforded the best results. This distance also successfully discriminated molecules with low and large prediction errors for a mechanism-based model developed using log P and the Maximum Acceptor Superdelocalizability descriptors. Thus, the distance to model metric could also be used to augment mechanistic QSAR models by estimating their prediction errors. Moreover, the accuracy of prediction is mainly determined by the training set data distribution in the chemistry and activity spaces but not by QSAR approaches used to develop the models. We have shown that incorrect validation of a model may result in the wrong estimation of its performance and suggested how this problem could be circumvented. The toxicity of 3182 and 48774 molecules from the EPA High Production Volume (HPV) Challenge Program and EINECS (European chemical Substances Information System), respectively, was predicted, and the accuracy of prediction was estimated. The developed models are available online at http://www.qspr.org site
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
Keywords neural-networks; QSPR models; error estimation; validation; prediction; solubility; confidence; regression; molecules; accuracy
ISSN (print) / ISBN 0021-9576
e-ISSN 1520-5142
Journal Journal of Chemical Information and Modeling
Quellenangaben Volume: 48, Issue: 9, Pages: 1733-1746 Article Number: , Supplement: ,
Publisher American Chemical Society (ACS)
Non-patent literature Publications
Reviewing status Peer reviewed
Institute(s) Institute of Bioinformatics and Systems Biology (IBIS)