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Title: An ensemble model of QSAR tools for regulatory risk assessment

Abstract

Quantitative structure activity relationships (QSARs) are theoretical models that relate a quantitative measure of chemical structure to a physical property or a biological effect. QSAR predictions can be used for chemical risk assessment for protection of human and environmental health, which makes them interesting to regulators, especially in the absence of experimental data. For compatibility with regulatory use, QSAR models should be transparent, reproducible and optimized to minimize the number of false negatives. In silico QSAR tools are gaining wide acceptance as a faster alternative to otherwise time-consuming clinical and animal testing methods. However, different QSAR tools often make conflicting predictions for a given chemical and may also vary in their predictive performance across different chemical datasets. In a regulatory context, conflicting predictions raise interpretation, validation and adequacy concerns. To address these concerns, ensemble learning techniques in the machine learning paradigm can be used to integrate predictions from multiple tools. By leveraging various underlying QSAR algorithms and training datasets, the resulting consensus prediction should yield better overall predictive ability. We present a novel ensemble QSAR model using Bayesian classification. The model allows for varying a cut-off parameter that allows for a selection in the desirable trade-off between model sensitivity andmore » specificity. The predictive performance of the ensemble model is compared with four in silico tools (Toxtree, Lazar, OECD Toolbox, and Danish QSAR) to predict carcinogenicity for a dataset of air toxins (332 chemicals) and a subset of the gold carcinogenic potency database (480 chemicals). Leave-one-out cross validation results show that the ensemble model achieves the best trade-off between sensitivity and specificity (accuracy: 83.8 % and 80.4 %, and balanced accuracy: 80.6 % and 80.8 %) and highest inter-rater agreement [kappa (κ): 0.63 and 0.62] for both the datasets. The ROC curves demonstrate the utility of the cut-off feature in the predictive ability of the ensemble model. In conclusion, this feature provides an additional control to the regulators in grading a chemical based on the severity of the toxic endpoint under study.« less

Authors:
ORCiD logo [1];  [2];  [3];  [2]
  1. National Center for Computational Toxicology (ORISE Fellow), Research Triangle Park, NC (United States)
  2. Marquette Univ., Milwaukee, WI (United States)
  3. Georgetown Univ. Medical Center, Washington, D.C. (United States)
Publication Date:
Research Org.:
Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1375955
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Cheminformatics
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 1758-2946
Publisher:
Chemistry Central Ltd.
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 97 MATHEMATICS AND COMPUTING; Computational toxicology; In silico QSAR tools; Hybrid QSAR models; Ensemble models; Risk assessment

Citation Formats

Pradeep, Prachi, Povinelli, Richard J., White, Shannon, and Merrill, Stephen J. An ensemble model of QSAR tools for regulatory risk assessment. United States: N. p., 2016. Web. doi:10.1186/s13321-016-0164-0.
Pradeep, Prachi, Povinelli, Richard J., White, Shannon, & Merrill, Stephen J. An ensemble model of QSAR tools for regulatory risk assessment. United States. https://doi.org/10.1186/s13321-016-0164-0
Pradeep, Prachi, Povinelli, Richard J., White, Shannon, and Merrill, Stephen J. Thu . "An ensemble model of QSAR tools for regulatory risk assessment". United States. https://doi.org/10.1186/s13321-016-0164-0. https://www.osti.gov/servlets/purl/1375955.
@article{osti_1375955,
title = {An ensemble model of QSAR tools for regulatory risk assessment},
author = {Pradeep, Prachi and Povinelli, Richard J. and White, Shannon and Merrill, Stephen J.},
abstractNote = {Quantitative structure activity relationships (QSARs) are theoretical models that relate a quantitative measure of chemical structure to a physical property or a biological effect. QSAR predictions can be used for chemical risk assessment for protection of human and environmental health, which makes them interesting to regulators, especially in the absence of experimental data. For compatibility with regulatory use, QSAR models should be transparent, reproducible and optimized to minimize the number of false negatives. In silico QSAR tools are gaining wide acceptance as a faster alternative to otherwise time-consuming clinical and animal testing methods. However, different QSAR tools often make conflicting predictions for a given chemical and may also vary in their predictive performance across different chemical datasets. In a regulatory context, conflicting predictions raise interpretation, validation and adequacy concerns. To address these concerns, ensemble learning techniques in the machine learning paradigm can be used to integrate predictions from multiple tools. By leveraging various underlying QSAR algorithms and training datasets, the resulting consensus prediction should yield better overall predictive ability. We present a novel ensemble QSAR model using Bayesian classification. The model allows for varying a cut-off parameter that allows for a selection in the desirable trade-off between model sensitivity and specificity. The predictive performance of the ensemble model is compared with four in silico tools (Toxtree, Lazar, OECD Toolbox, and Danish QSAR) to predict carcinogenicity for a dataset of air toxins (332 chemicals) and a subset of the gold carcinogenic potency database (480 chemicals). Leave-one-out cross validation results show that the ensemble model achieves the best trade-off between sensitivity and specificity (accuracy: 83.8 % and 80.4 %, and balanced accuracy: 80.6 % and 80.8 %) and highest inter-rater agreement [kappa (κ): 0.63 and 0.62] for both the datasets. The ROC curves demonstrate the utility of the cut-off feature in the predictive ability of the ensemble model. In conclusion, this feature provides an additional control to the regulators in grading a chemical based on the severity of the toxic endpoint under study.},
doi = {10.1186/s13321-016-0164-0},
journal = {Journal of Cheminformatics},
number = 1,
volume = 8,
place = {United States},
year = {Thu Sep 22 00:00:00 EDT 2016},
month = {Thu Sep 22 00:00:00 EDT 2016}
}

Journal Article:
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Cited by: 29 works
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Figures / Tables:

Fig. 1 Fig. 1: Bayesian classifier ensemble for predicting carcinogenicity. The posterior probability, Pk, as determined from Table 1 is compared with a variable cut-off between 0 and 1.

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The Challenges Involved in Modeling Toxicity Data In Silico: A Review
journal, March 2012


Evaluation of model predictive ability by external validation techniques
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  • Journal of Chemometrics, Vol. 24, Issue 3-4
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Ensemble QSAR: A QSAR method based on conformational ensembles and metric descriptors
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  • Journal of Computational Chemistry, Vol. 32, Issue 10
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Animal testing and alternative approaches for the human health risk assessment under the proposed new European chemicals regulation
journal, May 2004

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  • Archives of Toxicology, Vol. 78, Issue 10
  • DOI: 10.1007/s00204-004-0577-9

A weighted voting framework for classifiers ensembles
journal, December 2012

  • Kuncheva, Ludmila I.; Rodríguez, Juan J.
  • Knowledge and Information Systems, Vol. 38, Issue 2
  • DOI: 10.1007/s10115-012-0586-6

Methods for detecting carcinogens and mutagens with the salmonella/mammalian-microsome mutagenicity test
journal, December 1975

  • Ames, Bruce N.; McCann, Joyce; Yamasaki, Edith
  • Mutation Research/Environmental Mutagenesis and Related Subjects, Vol. 31, Issue 6
  • DOI: 10.1016/0165-1161(75)90046-1

A new hybrid system of QSAR models for predicting bioconcentration factors (BCF)
journal, December 2008


Computational toxicology in drug development
journal, April 2008


Classifier ensembles: Select real-world applications
journal, January 2008


Integration of QSAR models for bioconcentration suitable for REACH
journal, July 2013


Toxicokinetics as a key to the integrated toxicity risk assessment based primarily on non-animal approaches
journal, August 2013


Comparison of MC4PC and MDL-QSAR rodent carcinogenicity predictions and the enhancement of predictive performance by combining QSAR models
journal, December 2007

  • Contrera, Joseph F.; Kruhlak, Naomi L.; Matthews, Edwin J.
  • Regulatory Toxicology and Pharmacology, Vol. 49, Issue 3
  • DOI: 10.1016/j.yrtph.2007.07.001

Boosting:  An Ensemble Learning Tool for Compound Classification and QSAR Modeling
journal, May 2005

  • Svetnik, Vladimir; Wang, Ting; Tong, Christopher
  • Journal of Chemical Information and Modeling, Vol. 45, Issue 3
  • DOI: 10.1021/ci0500379

Interpretable, Probability-Based Confidence Metric for Continuous Quantitative Structure–Activity Relationship Models
journal, February 2013

  • Keefer, Christopher E.; Kauffman, Gregory W.; Gupta, Rishi Raj
  • Journal of Chemical Information and Modeling, Vol. 53, Issue 2
  • DOI: 10.1021/ci300554t

Comparative Evaluation of in Silico Systems for Ames Test Mutagenicity Prediction: Scope and Limitations
journal, June 2011

  • Hillebrecht, Alexander; Muster, Wolfgang; Brigo, Alessandro
  • Chemical Research in Toxicology, Vol. 24, Issue 6
  • DOI: 10.1021/tx2000398

The application of discovery toxicology and pathology towards the design of safer pharmaceutical lead candidates
journal, August 2007

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  • Nature Reviews Drug Discovery, Vol. 6, Issue 8
  • DOI: 10.1038/nrd2378

U.S. EPA Regulatory Perspectives on the Use of QSAR for New and Existing Chemical Evaluations
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  • SAR and QSAR in Environmental Research, Vol. 3, Issue 3
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journal, January 2011


Summary of a workshop on regulatory acceptance of (Q)SARs for human health and environmental endpoints.
journal, August 2003

  • Jaworska, Joanna S.; Comber, M.; Auer, C.
  • Environmental Health Perspectives, Vol. 111, Issue 10
  • DOI: 10.1289/ehp.5757

Use of QSARs in international decision-making frameworks to predict health effects of chemical substances.
journal, August 2003

  • Cronin, Mark T. D.; Jaworska, Joanna S.; Walker, John D.
  • Environmental Health Perspectives, Vol. 111, Issue 10
  • DOI: 10.1289/ehp.5760

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.