We used the same MM-GBSA protocol described above to rank the 154 ligands provided for the affinity prediction challenge. The initial binding pose was manually created in Chimera based on a reference structure. The reference was chosen either from the available co-crystal structures or from binding poses we predicted using HYBRID for the 20 ligands in the pose prediction challenge depending on which reference ligand had the highest molecular similarity. More details about the selected reference structures can be found in Table and.