Background: Spread of COVID-19 attains a crucial transition in reveling its pandemic across
the boundaries. In combating the infection caused by SARS-CoV-2, there is a spectrum of ideal strategies
that have been adopted globally, of which repurposing of approved drugs considerably having high
clinical relevance. 3-chymotrypsin-like protease (3CL pro) is considered to be the potential target for the
researchers as it is highly essential for cleavage of polyprotein to get 16 nonstructural proteins (called
nsp1-nsp16). These proteins are highly essential for viral replication and hence become a primary target
for enzyme inhibitors. 3CL pro, having a structural projectile helical chain with biologically active site
involved in processing viral polyproteins that are evolved from RNA genome translation.
Objective: The major objective of the present investigation is to evaluate the enzyme inhibition potential
of FDA approved therapeutic leads in targeting 3CLpro that medicates the viral replication.
Methods: Docking calculations were carried out for an array of FDA approved molecules which leads to
a notable few molecules such as Emtricitabine, Oseltamivir, Ganciclovir, Chloroquine, Baricitinib,
Favipiravir, Lopinavir, Ritonavir, Remdesivir, Ribavirin, Tenofovir, Umifenovir, Carbapenam, Ertapenem
and Imipenam which have both specificity and selectivity in terms of binding efficiency against
Results: A combinatorial evaluation employing in-silico screening shows a major lead for remdesivir
which possesses a substantial affinity to 3CL pro binding on core amino acid residues, such as Leu 27,
His 41, Gly 143, Cys 145, His 164, Met 165, Glu 166, Pro 168 and His 172 which share the biological
significance in mediating enzymatic action. Results of docking simulation by Autodock over a host of
FDA approved molecules show high degree of selectivity and specificity in the increasing order of binding
capacity; Remdesivir> Ertapenem> Imipenam> Tenofovir> Umifenovir> Chloroquine> Lopinavir>
Ritonavir> Emtricitabine> Ganciclovir> Baricitinib> Ribavirin>Oseltamivir>Favipiravir> Carbapenam.
Conclusion: Till date, there is no known cure attained for treating COVID-19 infection. In conclusion,
lead molecules from already approved sources provoke promising potential which grabs the attention of
the clinicians in availing potential therapeutic candidate as a drug of choice in the clinical management
of COVID-19 time-dependently.