In drug discovery, biological activity vs. one or multiple endpoints is one of the primary properties to be predicted and thus, SAR analysis is a cornerstone in medicinal chemistry . Moreover, predicting properties of pharmaceutical relevance such as those related to ADMETox are also crucial, as commented in section 3.2.1. Recently it has been emphasized the need to explore systematically structure-inactivity relationships -SIR -as part of the generation of predictive models .