SARS-CoV-2 RNA-dependent RNA polymerase as a therapeutic target for COVID-19

Abstract

Introduction: The current SARS-CoV-2 pandemic urgently demands for both prevention and treatment strategies. RNA-dependent RNA-polymerase (RdRp), which has no counterpart in human cells, is an excellent target for drug development. Given the time-consuming process of drug development, repurposing drugs approved for other indications or at least successfully tested in terms of safety and tolerability, is an attractive strategy to rapidly provide an effective medication for severe COVID-19 cases.Areas covered: The currently available data and upcominSg studies on RdRp which can be repurposed to halt SARS-CoV-2 replication, are reviewed.Expert opinion: Drug repurposing and design of novel compounds are proceeding in parallel to provide a quick response and new specific drugs, respectively. Notably, the proofreading SARS-CoV-2 exonuclease activity could limit the potential for drugs designed as immediate chain terminators and favor the development of compounds acting through delayed termination. While vaccination is awaited to curb the SARS-CoV-2 epidemic, even partially effective drugs from repurposing strategies can be of help to treat severe cases of disease. Considering the high conservation of RdRp among coronaviruses, an improved knowledge of its activity in vitro can provide useful information for drug development or drug repurposing to combat SARS-CoV-2 as well as future pandemics.

Keywords: COVID-19; drug repurposing; nucleoside inhibitors; rna polymerase; sars-CoV-2.

Figure 1.

Color-coded scheme and structure of the SARS-CoV nsp12 RdRp bound to nsp7 and nsp8 co-factors. (a) Diagram of the SARS-CoV nsp7, nsp8, and nsp12 proteins indicating domains and conserved motifs. (b) SARS-CoV nsp12 contains a large N-terminal extension composed of the NiRAN domain (dark red) and an interface domain (purple) adjacent to the polymerase domain (orange). nsp12 binds to a heterodimer of nsp7 (blue) and nsp8 (green) as well as to a second subunit of nsp8. Adapted (http://creativecommons.org/licenses/by/4.0/) from Kirchdoerfer et al. [12]. Color figure.

Figure 2.

Chemical structure of potential SARS-CoV-2 RdRp inhibitors under clinical investigation. (A) Remdesivir; (B) Molnupiravir; (C) Galidesivir; (D) Ribavirin; (E) Sofosbuvir; (F) Tenofovir; (G) Favipiravir