Pitfalls in QSAR

There are no formal guidelines for the development of quantitative structure-activity relationships (QSARs). However, there are a number of practices that should be avoided. This paper describes the pitfalls in QSAR, and problems that can arise if they occur. The emphasis of this paper is particularly for the development of QSARs for toxicity for environmental endpoints and drugs, but is equally applicable to pharmacological endpoints. Problems may arise from all three areas of the QSAR, namely the biological activity, physico-chemical and/or structural descriptors, and the use of a statistical technique. Biological data for use in a QSAR should be of a known (and preferably high) quality. Physico-chemical descriptors and statistical processes should be appropriate for the endpoint being modelled. They should allow for the development of a clear, transparent and mechanistically interpretable QSAR. To have any practical utility, QSARs should be validated by means of an external testing set. (C) 2002 Elsevier Science B.V. All rights reserved.