Because the new variable space is normalized with zero mean, the most active compounds, which are farther from the origin, have values significantly different from the mean and can be considered outliers. Moreover, we found that the scattering positions of the true BACE-1 inhibitors are located on the right side of the PC1 axis indicating that PC1 plays a significant discriminating role among active and inactive compounds. As for the PC2 axis, all of the data were scattered in a narrow area from -3 to 3, and the discriminating power among active and inactive compounds was weaker. 