were located within FDA-approved drugs. Although most of compounds of project A and C were located at the marginal region of FDA-approved drugs, some of the compounds in these projects were located overlapping the space of FDA-approved drugs, and clearly close to the space of FDA-approved drugs rather than ChEMBL compounds. This suggests that some of the original structures of the compounds examined in this study are similar to those of FDA-approved drugs, which provides practical guidance for selecting compounds in the drug discovery stage.