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Reversible and irreversible inhibitors of coronavirus Nsp15 endoribonuclease
Jerry Chen1, Rabih Abou Farraj2, Daniel Limonta3
1Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada.
Abstract:
The emergence of severe acute respiratory syndrome coronavirus 2, the causative agent of coronavirus disease 2019, has resulted in the largest pandemic in recent history. Current therapeutic strategies to mitigate this disease have focused on the development of vaccines and on drugs that inhibit the viral 3CL protease or RNA-dependent RNA polymerase enzymes. A less-explored and potentially complementary drug target is Nsp15, a uracil-specific RNA endonuclease that shields coronaviruses and other nidoviruses from mammalian innate immune defenses. Here, we perform a high-throughput screen of over 100,000 small molecules to identify Nsp15 inhibitors. We characterize the potency, mechanism, selectivity, and predicted binding mode of five lead compounds. We show that one of these, IPA-3, is an irreversible inhibitor that might act via covalent modification of Cys residues within Nsp15. Moreover, we demonstrate that three of these inhibitors (hexachlorophene, IPA-3, and CID5675221) block severe acute respiratory syndrome coronavirus 2 replication in cells at subtoxic doses. This study provides a pipeline for the identification of Nsp15 inhibitors and pinpoints lead compounds for further development against coronavirus disease 2019 and related coronavirus infections.
Insights
Researchers screened over 100,000 molecules to find inhibitors for the Nsp15 enzyme, a key target for combating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and related viruses.
Area of Science:
- Virology
- Drug Discovery
- Biochemistry
Background:
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a global pandemic.
- Current treatments target viral enzymes like 3CL protease and RNA-dependent RNA polymerase.
- Nsp15, a uracil-specific RNA endonuclease, is a potential therapeutic target that aids viral immune evasion.
Purpose of the Study:
- To identify small molecule inhibitors of the SARS-CoV-2 Nsp15 enzyme.
- To characterize the identified inhibitors for potency, mechanism, and selectivity.
- To evaluate the efficacy of Nsp15 inhibitors in blocking viral replication.
Main Methods:
- High-throughput screening of over 100,000 small molecules.
- Biochemical characterization of lead compounds, including potency and mechanism of action.
- Cell-based assays to assess inhibition of SARS-CoV-2 replication.
Main Results:
- Five lead compounds were identified as Nsp15 inhibitors.
- IPA-3 was characterized as an irreversible inhibitor, potentially targeting Cys residues.
- Hexachlorophene, IPA-3, and CID5675221 demonstrated efficacy in blocking SARS-CoV-2 replication at subtoxic doses.
Conclusions:
- Nsp15 is a viable drug target for antiviral therapies against SARS-CoV-2.
- The study established a pipeline for discovering Nsp15 inhibitors.
- Identified lead compounds offer potential for developing new treatments for coronavirus infections.
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