Only 20 compound pairs selected from different participants had a Tanimoto distance of 0.3 or lower, based on ECFP4 fingerprints. Not surprisingly, all closest analogs selected by different participants (Figure ) were also close analogs of the crystallized fragments found in the PDB (Figure ), however none of these were ultimately confirmed experimentally. Indeed, in the previously reported fragment screen by crystallography, Nsp13 crystals were soaked in 50 mM fragments solutions , which can lead to the capture of fragments that are too weak to be detected by SPR (maximum concentration of 200 µM). Yet, crystallographically captured fragments were successfully grown into 20-40 µM hits, as detailed below.