ABSTRACT
Coronavirus disease 2019 (COVID-19) pandemic, a global health threat, was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 papain-like cysteine protease (PLpro) was recognized as a promising drug target because of multiple functions in virus maturation and antiviral immune responses. Inhibitor GRL0617 occupied the interferon-stimulated gene 15 (ISG15) C-terminus-binding pocket and showed an effective antiviral inhibition. Here, we described a novel peptide-drug conjugate (PDC), in which GRL0617 was linked to a sulfonium-tethered peptide derived from PLpro-specific substrate LRGG. The EM-C and EC-M PDCs showed a promising in vitro IC50 of 7.40 ± 0.37 and 8.63 ± 0.55 µM, respectively. EC-M could covalently label PLpro active site C111 and display anti-ISGylation activities in cellular assays. The results represent the first attempt to design PDCs composed of stabilized peptide inhibitors and GRL0617 to inhibit PLpro. These novel PDCs provide promising opportunities for antiviral drug design.
Subject(s)
Aniline Compounds/chemistry , Antiviral Agents/metabolism , Benzamides/chemistry , Coronavirus Papain-Like Proteases/metabolism , Drug Design , Naphthalenes/chemistry , Peptides/chemistry , SARS-CoV-2/enzymology , Aniline Compounds/metabolism , Aniline Compounds/pharmacology , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Antiviral Agents/therapeutic use , Benzamides/metabolism , Benzamides/pharmacology , COVID-19/pathology , COVID-19/virology , Cell Line , Cell Survival/drug effects , Coronavirus Papain-Like Proteases/chemistry , Cytokines/chemistry , Drug Evaluation, Preclinical , Humans , Inhibitory Concentration 50 , Naphthalenes/metabolism , Naphthalenes/pharmacology , SARS-CoV-2/isolation & purification , Ubiquitins/chemistry , COVID-19 Drug TreatmentABSTRACT
COVID-19 is a disease caused by SARS-CoV-2, which has led to more than 4 million deaths worldwide. As a result, there is a worldwide effort to develop specific drugs for targeting COVID-19. Papain-like protease (PLpro) is an attractive drug target because it has multiple essential functions involved in processing viral proteins, including viral genome replication and removal of post-translational ubiquitination modifications. Here, we established two assays for screening PLpro inhibitors according to protease and anti-ISGylation activities, respectively. Application of the two screening techniques to the library of clinically approved drugs led to the discovery of tanshinone IIA sulfonate sodium and chloroxine with their IC50 values of lower than 10 µM. These two compounds were found to directly interact with PLpro and their molecular mechanisms of binding were illustrated by docking and molecular dynamics simulations. The results highlight the usefulness of the two developed screening techniques for locating PLpro inhibitors.