In the second molecular docking exercise, we dock the geometry-optimized cyclic peptide inhibitor to a recently published crystal structure of SARS-CoV-2 M pro (PDB 6YB7). We load the SARS-CoV-2 M pro structure using the "fetch PDB" function in UCSF Chimera, and conduct molecular docking in a similar fashion to the previous exercise (Figure ). After the molecular docking is complete, we get ten docked conformations with energy scores of -8.1, -7.8, -6.8, -6.5, -6.5, -6.4, -6.4, -6.4, -6.2, and -5.6 kcal/mol. Although the lowest energy structure only partially fits into the active site of SARS-CoV-2 M pro , the second lowest energy structure of the inhibitor fits better in the active site. The P2 (Phe), P1 (Gln), P1' (Ser), and P2' (Lys) side chains of the inhibitor occupy the S1, S1', S2, and S2' pockets, while the AEPA residue sits near the S3' pocket (Figure ). This docking result suggests that the cyclic peptide inhibitor that we designed based on SARS-CoV M pro bound to a protein substrate might be repurposed to target SARS-CoV-2 M pro .