Targeting the SARS-CoV-2 main protease using FDA-approved Isavuconazonium, a P2–P3 α-ketoamide derivative and Pentagastrin: An in-silico drug discovery approach

The SARS-CoV-2 main protease (M(pro)) is an attractive target towards discovery of drugs to treat COVID-19 because of its key role in virus replication. The atomic structure of M(pro) in complex with an α-ketoamide inhibitor (Lig13b) is available (PDB ID:6Y2G). Using 6Y2G and the prior knowledge that protease inhibitors could eradicate COVID-19, we designed a computational study aimed at identifying FDA-approved drugs that could interact with M(pro). We searched the DrugBank and PubChem for analogs and built a virtual library containing ∼33,000 conformers. Using high-throughput virtual screening and ligand docking, we identified Isavuconazonium, a ketoamide inhibitor (α-KI) and Pentagastrin as the top three molecules (Lig13b as the benchmark) based on docking energy. The ΔG(bind) of Lig13b, Isavuconazonium, α-KI, Pentagastrin was −28.1, −45.7, −44.7, −34.8 kcal/mol, respectively. Molecular dynamics simulation revealed that these ligands are stable within the M(pro) active site. Binding of these ligands is driven by a variety of non-bonded interaction, including polar bonds, H-bonds, van der Waals and salt bridges. The overall conformational dynamics of the complexed-M(pro) was slightly altered relative to apo-M(pro). This study demonstrates that three distinct classes molecules, Isavuconazonium (triazole), α-KI (ketoamide) and Pentagastrin (peptide) could serve as potential drugs to treat patients with COVID-19.