Total and Local Quadratic Indices of the “Molecular Pseudograph’s Atom Adjacency Matrix”. Application to Prediction of Caco-2 Permeability of Drugs

The high interest in the prediction of the intestinal absorption for New Chemical Entities (NCEs) is generated by the increasing rate in the synthesis of compounds by combinatorial chemistry and the extensive cost of the traditional evaluation methods. Quantitative Structure–Permeability Relationships (QSPerR) of the intestinal permeability across the Caco-2 cells monolayer (PCaco-2) could be obtained by the application of new molecular descriptors. In this sense, quadratic indices of the “molecular pseudograph’s atom adjacency matrix” and multiple linear regression analysis were used to obtain good quantitative models to determine the PCaco-2. QSPerR models found are significant from a statistical point of view. The total and local quadratic indices were calculated with the TOMO-COMD software. A leave-one-out cross-validation procedure (internal validation) and the evaluation of external test set of 20 drugs (external validation) revealed that regression models had a good predictive power. A comparison with results derived from other theoretical studies shown a quite satisfactory behavior of the present method. The descriptors included in the prediction models permitted the interpretation in structural terms of the permeability process, evidencing the main role of H-bonding and size properties. The Int. J. Mol. Sci. 2003, 4 513 models found were used in virtual screening of drug intestinal permeability and a relationship between PCaco-2 calculated and percentage of human intestinal absorption for the 72 compounds was established. These results suggest that the proposed method is able to predict PCaco-2, being a good tool for screening of PCaco-2 for large sets of NCEs synthesized via combinatorial chemistry approach.