Benchmark of four popular virtual screening programs: construction of the active/decoy dataset remains a major determinant of measured performance.
BACKGROUND
In a structure-based virtual screening, the choice of the docking program is essential for the success of a hit identification. Benchmarks are meant to help in guiding this choice, especially when undertaken on a large variety of protein targets. Here, the performance of four popular virtual screening programs, Gold, Glide, Surflex and FlexX, is compared using the Directory of Useful Decoys-Enhanced database (DUD-E), which includes 102 targets with an average of 224 ligands per target and 50 decoys per ligand, generated to avoid biases in the benchmarking. Then, a relationship between these program performances and the properties of the targets or the small molecules was investigated.


RESULTS
The comparison was based on two metrics, with three different parameters each. The BEDROC scores with α = 80.5, indicated that, on the overall database, Glide succeeded (score > 0.5) for 30 targets, Gold for 27, FlexX for 14 and Surflex for 11. The performance did not depend on the hydrophobicity nor the openness of the protein cavities, neither on the families to which the proteins belong. However, despite the care in the construction of the DUD-E database, the small differences that remain between the actives and the decoys likely explain the successes of Gold, Surflex and FlexX. Moreover, the similarity between the actives of a target and its crystal structure ligand seems to be at the basis of the good performance of Glide. When all targets with significant biases are removed from the benchmarking, a subset of 47 targets remains, for which Glide succeeded for only 5 targets, Gold for 4 and FlexX and Surflex for 2.


CONCLUSIONS
The performance dramatic drop of all four programs when the biases are removed shows that we should beware of virtual screening benchmarks, because good performances may be due to wrong reasons. Therefore, benchmarking would hardly provide guidelines for virtual screening experiments, despite the tendency that is maintained, i.e., Glide and Gold display better performance than FlexX and Surflex. We recommend to always use several programs and combine their results. Graphical AbstractSummary of the results obtained by virtual screening with the four programs, Glide, Gold, Surflex and FlexX, on the 102 targets of the DUD-E database. The percentage of targets with successful results, i.e., with BDEROC(α = 80.5) > 0.5, when the entire database is considered are in Blue, and when targets with biased chemical libraries are removed are in Red.
Institut Curie - PSL Research University, Chemistry, Modelling and Imaging for Biology (CMIB), Centre de Recherche, Centre Universitaire, Orsay, Bâtiment 112, 91405 Orsay Cedex, France ; Paris-Sud University, Orsay Cedex, France ; Inserm, U1196, Orsay Cedex, France ; CNRS, UMR 9187, Orsay Cedex, France.
Ludovic
L
Chaput
Institut Curie - PSL Research University, Chemistry, Modelling and Imaging for Biology (CMIB), Centre de Recherche, Centre Universitaire, Orsay, Bâtiment 112, 91405 Orsay Cedex, France ; Paris-Sud University, Orsay Cedex, France ; Inserm, U1196, Orsay Cedex, France ; CNRS, UMR 9187, Orsay Cedex, France.
Juan
J
Martinez-Sanz
Institut Curie - PSL Research University, Chemistry, Modelling and Imaging for Biology (CMIB), Centre de Recherche, Centre Universitaire, Orsay, Bâtiment 112, 91405 Orsay Cedex, France ; Inserm, U1196, Orsay Cedex, France ; CNRS, UMR 9187, Orsay Cedex, France ; School of Pharmacy, University of Caen, Normandy, Boulevard Becquerel, 14032 Caen, France.
Nicolas
N
Saettel
Institut Curie - PSL Research University, Chemistry, Modelling and Imaging for Biology (CMIB), Centre de Recherche, Centre Universitaire, Orsay, Bâtiment 112, 91405 Orsay Cedex, France ; Paris-Sud University, Orsay Cedex, France ; Inserm, U1196, Orsay Cedex, France ; CNRS, UMR 9187, Orsay Cedex, France.
Liliane
L
Mouawad
BEDROC; Benchmark; DUD-E; Docking; FlexX; Glide; Gold; Structure-based virtual screening; Surflex