for training and testing, respectively; therefore, its predictivity may pose a potential risk of over 30% error in human intestinal absorption at the clinical stage (Table ). Next, we counted the number of compounds that were underestimated less than -15% and -30% (this means worse predictivity than 15%) and overestimated more than 15% and 30% (this means worse predictivity than 15%). The plot in GUTFW indicates the tendency of this predictivity to be oriented toward underprediction. The number of compounds that were underestimated less than -15% and -30% were 20 and 24, respectively, and the number of compounds that were overestimated more than 15% and 30 % were 10 and 6, respectively (Figure ). The difficulty of predicting Fa using only chemical structures was highlighted by Sugano et al. . In particular, using the GUTFW model without experimental data led to predictive errors associated with the in silico values, which were the solubility and membrane permeability values predicted by AP in this study. This indicates that the predictive ability of the GUTFW model can be improved by introducing a more accurate calculator for these parameters.