The residues in the M pro that most frequently take part in interactions with the ligands are E166 (12 hydrophobic contacts and 6 H-bonds), M165 (13 hydrophobic contacts), and Q189 (12 hydrophobic contacts and one H-bond). Moreover, some other residues have moderate potential to interact with the ligands, including the active site residue, C145 (8 hydrophobic contacts and one H-bond), N142 (5 hydrophobic contacts and 3 H-bond), M49 (7 hydrophobic contacts), P168 (6 hydrophobic contacts), F140 (5 hydrophobic contacts), L167 (4 hydrophobic contacts and one H-bond), and Q192 (3 hydrophobic contacts and two H-bonds) (see Table ).