Screening of FDA approved drugs for finding potential inhibitors against Granzyme B as a potent drug-repurposing target.

Granzyme B is one of the best-characterized and extensively studied member of cytotoxic lymphocytes (CL) proteases. Initially, it is thought to be involved in eliminating virally infected or cancerous cells by using a specialized mechanism through which they are internalized into target cells. In the last decade, however this dimension has changed as there are several reports show that not only CL but also other immune cells can also synthesize Granzyme B. This leads to the possibility of the presence of these proteases in extracellular environment. Being active protease, it then raises the possibility of damaging host tissues as evident from the available reported literature. In many instances, Granzyme B is directly involved in pathogenicity, however in others, it contributes to the disease severity as their over expression makes the clinical situation quite worse which ultimately leads to the chronic state of the disease. Serine protease inhibitor-9 is a natural known intracellular inhibitor of Granzyme B, however there is less data available about the potential inhibitors that can regulate its activity in an extracellular environment. Current study is an effort to identify potential novel inhibitors of Granzyme B. For this aim, drug repurposing study was performed. Around 7900 FDA approved drugs were screened using both ligand- and target-driven approaches. Initially, all molecules were docked using induced fit docking (IFD) approach and selected 318 high-docking scored molecules were used in short (1-ns) molecular dynamics (MD) simulations. Based on MM/GBSA binding free energy calculations, 6 compounds were selected and used in long (100-ns) MD simulations. These compounds were then used in binary QSAR analysis. Therapeutic activity potentials of studied compounds were investigated by Clarivate Analytics's MetaCore/MetaDrug platform which uses binary QSAR models. It is developed based on manually curated database of molecular interactions, molecular pathways, gene-disease associations, chemical metabolism and toxicity information. Results of selected compounds were compared with a positive control molecule. Current drug repurposing study is a step ahead in finding potential lead compounds by screening database of FDA approved molecules. We have identified novel inhibitors (Tannic acid, Mupirocin, Phytonadiol sodium diphosphate, Cefpiramide, Xenazoic acid) that have potential to decrease the activity of Granzyme B.