To prevent singletons in the training set, a minimum number of compounds for a viable cluster was specified. The study explored clusters with minimums of 5, 25, 50, and 75 compounds, and the centroids of these clusters were selected for training sets B, C, D, and E, respectively (Table ). Ligand-based pharmacophore models A, B, C, D, and E were built using the five active groups A, B, C, D, E, respectively. These models were then compared to select the most effective model for virtual screening.