Title : Structure-activity relationship studies of novel SARS-CoV-2 papain-like protease inhibitors with evaluation of their anti-SARS-CoV-2 and anti-Mpox activities
Abstract:
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has not yet been eradicated. SARS-CoV-2 has two types of proteases, a main protease (Mpro) and a papain-like protease (PLpro). Papain-like protease (PLpro) is a viral protease essential for SARS-CoV-2 replication in concurrence with a main protease. The active site of PLpro from SARS-CoV, the causative virus of the Severe Acute Respiratory Syndrome (SARS) outbreak in 2002, exhibits 100% homology to that of SARS-CoV-2 PLpro. Dr. Mitsuya and colleagues found that a SARS-CoV PLpro inhibitor, GRL-0048, showed inhibitory potency against SARS-CoV-2. Therefore, we started structure-activity relationship (SAR) studies using GRL-0048 as a lead compound to develop more potent SARS-CoV-2 PLpro inhibitors. We previously developed several potent SARS-CoV-2 Mpro inhibitors, including TKB245 and TKB248, by introducing fluorine atoms into lead compounds to induce an effective fluorine-associated interaction with Mpro and enhance cell-membrane permeability. In this study, we designed and synthesized novel compounds using GRL-0048 as a lead compound. A docking simulation of GRL-0048 with SARS-CoV-2 PLpro identified suitable sites for fluorine substitutions at suitable sites in the inhibitor molecules where there is space for the interaction with SARS-CoV-2 PLpro. Structure-activity relationship studies led to the development of several inhibitors exhibiting superior potency compared to GRL-0048.
In addition, we focused on a I7L protease (I7Lpro) that is a main protease of the zoonotic monkeypox virus (MPXV; Mpox virus). The I7Lpro active site is composed of Cys328, His241 and Asp248 residues. Protein structure prediction indicated similarities between the active sites of I7Lpro and SARS-CoV-2 PLpro, which is composed of Cys111, His271 and Asp286 residues. Consequently, we assessed the antiviral activity of the synthesized PLpro inhibitors against MPXV. As a result, we identified several compounds with antiviral activity against MPXV but not against SARS-CoV-2. The present study will be discussed in details of the design, synthesis, and SAR studies of these compounds against both viruses.
