A quantitative structure-activity relationship (QSAR) model of the fetal-maternal blood concentration ratio (F/M ratio) of chemicals was developed to predict the placental transfer in humans. Data on F/M ratio of 55 compounds found in the literature were separated into training (75%, 41 compounds) and testing sets (25%, 14 compounds). The training sets were then subjected to multiple linear regression analysis using the descriptors of molecular weight (MW), topological polar surface area (TopoPSA), and maximum E-state of hydrogen atom (Hmax). Multiple linear regression analysis and a cross-validation showed a relatively high adjusted coefficient of determination (R a 2 ) (0.73) and cross-validated coefficient of determination (Q 2 ) (0.71), after removing three outliers. In the external validation, R 2 for external validation (R 2 pred ) was calculated to be 0.51. These results suggested that the QSAR model developed in this study can be considered reliable in terms of its robustness and predictive performance. Since it is difficult to examine the F/M ratio in humans experimentally, this QSAR model for prediction of the placental transfer of chemicals in humans could be useful in risk assessment of chemicals in humans.Key words placental transfer; human; quantitative structure-activity relationship; fetal-maternal blood concentration ratioThe placental transfer of chemicals is crucial for toxicity assessment of fetus, because chemicals that do not penetrate the placenta are considered safe for fetus.1) Therefore, investigations of many drugs that are transferred from mother to fetus through the placenta have been performed.Since it is difficult to measure the placental transfer of chemicals in humans ethically, in vitro and ex vivo methods have been developed and used for the evaluation of human placental transfer.2) In in vitro methods, cell lines from human placenta, such as BeWo, JAr, and JEG cells, have been commonly used as models of the placental barrier.3) In ex vivo methods, the human placenta is perfused to investigate the transfer of chemicals from maternal to fetal compartment. Although this system has been validated in many studies, and therefore this system is considered reliable, there are difficulties in conducting this evaluation method.
2,4)Quantitative structure-activity relationship (QSAR) models are useful tools for predicting the biological activity of chemicals. Descriptors of chemicals such as molecular weight and log P, are needed to develop QSAR prediction, and those are determined by experiments, calculation, or predicted using software. In the field of pharmacokinetics, QSAR models have been developed and reported in areas such as oral bioavailability, Caco-2 permeability, and metabolism.
5-7)QSAR models for predicting the placental transfer of chemicals using ex vivo data have already been reported. 8,9) However, to our knowledge, this is the first report that indicates prediction of the fetal-maternal blood concentration ratio (F/M ratio) of chemicals using in vivo data. To predict t...