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Nouwen LV, Breeuwsma M, Zaal EA, van de Lest CHA, Buitendijk I, Zwaagstra M, Balić P, Filippov DV, Berkers CR, van Kuppeveld FJM. Modulation of nucleotide metabolism by picornaviruses. PLoS Pathog 2024; 20:e1012036. [PMID: 38457376 PMCID: PMC10923435 DOI: 10.1371/journal.ppat.1012036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 02/08/2024] [Indexed: 03/10/2024] Open
Abstract
Viruses actively reprogram the metabolism of the host to ensure the availability of sufficient building blocks for virus replication and spreading. However, relatively little is known about how picornaviruses-a large family of small, non-enveloped positive-strand RNA viruses-modulate cellular metabolism for their own benefit. Here, we studied the modulation of host metabolism by coxsackievirus B3 (CVB3), a member of the enterovirus genus, and encephalomyocarditis virus (EMCV), a member of the cardiovirus genus, using steady-state as well as 13C-glucose tracing metabolomics. We demonstrate that both CVB3 and EMCV increase the levels of pyrimidine and purine metabolites and provide evidence that this increase is mediated through degradation of nucleic acids and nucleotide recycling, rather than upregulation of de novo synthesis. Finally, by integrating our metabolomics data with a previously acquired phosphoproteomics dataset of CVB3-infected cells, we identify alterations in phosphorylation status of key enzymes involved in nucleotide metabolism, providing insight into the regulation of nucleotide metabolism during infection.
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Affiliation(s)
- Lonneke V. Nouwen
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Martijn Breeuwsma
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Esther A. Zaal
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Chris H. A. van de Lest
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Inge Buitendijk
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Marleen Zwaagstra
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Pascal Balić
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Universiteit Leiden, Leiden, The Netherlands
| | - Dmitri V. Filippov
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Universiteit Leiden, Leiden, The Netherlands
| | - Celia R. Berkers
- Division Cell Biology, Metabolism & Cancer, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Frank J. M. van Kuppeveld
- Section of Virology, Division of Infectious Diseases & Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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2
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He Y, Zhou J, Gao H, Liu C, Zhan P, Liu X. Broad-spectrum antiviral strategy: Host-targeting antivirals against emerging and re-emerging viruses. Eur J Med Chem 2024; 265:116069. [PMID: 38160620 DOI: 10.1016/j.ejmech.2023.116069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/06/2023] [Accepted: 12/16/2023] [Indexed: 01/03/2024]
Abstract
Viral infections are amongst the most prevalent diseases that pose a significant threat to human health. Targeting viral proteins or host factors represents two primary strategies for the development of antiviral drugs. In contrast to virus-targeting antivirals (VTAs), host-targeting antivirals (HTAs) offer advantages in terms of overcoming drug resistance and effectively combating a wide range of viruses, including newly emerging ones. Therefore, targeting host factors emerges as an extremely promising strategy with the potential to address critical challenges faced by VTAs. In recent years, extensive research has been conducted on the discovery and development of HTAs, leading to the approval of maraviroc, a chemokine receptor type 5 (CCR5) antagonist used for the treatment of HIV-1 infected individuals, with several other potential treatments in various stages of development for different viral infections. This review systematically summarizes advancements made in medicinal chemistry regarding various host targets and classifies them into four distinct catagories based on their involvement in the viral life cycle: virus attachment and entry, biosynthesis, nuclear import and export, and viral release.
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Affiliation(s)
- Yong He
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China
| | - Jiahui Zhou
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China
| | - Huizhan Gao
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China
| | - Chuanfeng Liu
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China
| | - Peng Zhan
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China.
| | - Xinyong Liu
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Ji'nan, 250012, Shandong Province, PR China.
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3
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Fraser-Pitt D, Mercer DK, Francis ML, Toledo-Aparicio D, Smith DW, O'Neil DA. Cysteamine-mediated blockade of the glycine cleavage system modulates epithelial cell inflammatory and innate immune responses to viral infection. Biochem Biophys Res Commun 2023; 677:168-181. [PMID: 37597441 DOI: 10.1016/j.bbrc.2023.08.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/07/2023] [Accepted: 08/09/2023] [Indexed: 08/21/2023]
Abstract
Transient blockade of glycine decarboxylase (GLDC) can restrict de novo pyrimidine synthesis, which is a well-described strategy for enhancing the host interferon response to viral infection and a target pathway for some licenced anti-inflammatory therapies. The aminothiol, cysteamine, is produced endogenously during the metabolism of coenzyme A, and is currently being investigated in a clinical trial as an intervention in community acquired pneumonia resulting from viral (influenza and SARS-CoV-2) and bacterial respiratory infection. Cysteamine is known to inhibit both bacterial and the eukaryotic host glycine cleavage systems via competitive inhibition of GLDC at concentrations, lower than those required for direct antimicrobial or antiviral activity. Here, we demonstrate for the first time that therapeutically achievable concentrations of cysteamine can inhibit glycine utilisation by epithelial cells and improve cell-mediated responses to infection with respiratory viruses, including human coronavirus 229E and Influenza A. Cysteamine reduces interleukin-6 (IL-6) and increases the interferon-λ (IFN-λ) response to viral challenge and in response to liposomal polyinosinic:polycytidylic acid (poly I:C) simulant of RNA viral infection.
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Affiliation(s)
- Douglas Fraser-Pitt
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom.
| | - Derry K Mercer
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom; Bioaster, LYON (headquarters) 40, Avenue Tony Garnier, 69007, Lyon, France
| | - Marie-Louise Francis
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom
| | - David Toledo-Aparicio
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom
| | - Daniel W Smith
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom
| | - Deborah A O'Neil
- NovaBiotics Ltd, Silverburn Crescent, Bridge of Don, Aberdeen, AB23 8EW, United Kingdom
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4
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Paulis A, Tramontano E. Unlocking STING as a Therapeutic Antiviral Strategy. Int J Mol Sci 2023; 24:ijms24087448. [PMID: 37108610 PMCID: PMC10138487 DOI: 10.3390/ijms24087448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 04/06/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
Invading pathogens have developed weapons that subvert physiological conditions to weaken the host and permit the spread of infection. Cells, on their side, have thus developed countermeasures to maintain cellular physiology and counteract pathogenesis. The cyclic GMP-AMP (cGAMP) synthase (cGAS) is a pattern recognition receptor that recognizes viral DNA present in the cytosol, activating the stimulator of interferon genes (STING) protein and leading to the production of type I interferons (IFN-I). Given its role in innate immunity activation, STING is considered an interesting and innovative target for the development of broad-spectrum antivirals. In this review, we discuss the function of STING; its modulation by the cellular stimuli; the molecular mechanisms developed by viruses, through which they escape this defense system; and the therapeutical strategies that have been developed to date to inhibit viral replication restoring STING functionality.
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Affiliation(s)
- Annalaura Paulis
- Department of Life and Environmental Sciences, Università Degli Studi di Cagliari, 09124 Cagliari, Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, Università Degli Studi di Cagliari, 09124 Cagliari, Italy
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5
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de Mariz E Miranda LS. The synergy between nucleotide biosynthesis inhibitors and antiviral nucleosides: New opportunities against viral infections? Arch Pharm (Weinheim) 2023; 356:e2200217. [PMID: 36122181 DOI: 10.1002/ardp.202200217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/18/2022] [Accepted: 08/26/2022] [Indexed: 01/04/2023]
Abstract
5'-Phosphorylated nucleoside derivatives are molecules that can be found in all living organisms and viruses. Over the last century, the development of structural analogs that could disrupt the transcription and translation of genetic information culminated in the development of clinically relevant anticancer and antiviral drugs. However, clinically effective broad-spectrum antiviral compounds or treatments are lacking. This viewpoint proposes that molecules that inhibit nucleotide biosynthesis may sensitize virus-infected cells toward direct-acting antiviral nucleosides. Such potentially synergistic combinations might allow the repurposing of drugs, leading to the development of new combination therapies.
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Affiliation(s)
- Leandro S de Mariz E Miranda
- Department of Organic Chemistry, Chemistry Institute, Biocatalysis and Organic Synthesis Group, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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6
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Mashayekh S, Stunkard LM, Kienle M, Mathews II, Khosla C. Structure-Based Prototyping of Allosteric Inhibitors of Human Uridine/Cytidine Kinase 2 (UCK2). Biochemistry 2022; 61:2261-2266. [PMID: 36190114 DOI: 10.1021/acs.biochem.2c00451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pyrimidine nucleotide biosynthesis in humans is a promising chemotherapeutic target for infectious diseases caused by RNA viruses. Because mammalian cells derive pyrimidine ribonucleotides through a combination of de novo biosynthesis and salvage, combined inhibition of dihydroorotate dehydrogenase (DHODH; the first committed step in de novo pyrimidine nucleotide biosynthesis) and uridine/cytidine kinase 2 (UCK2; the first step in salvage of exogenous nucleosides) strongly attenuates viral replication in infected cells. However, while several pharmacologically promising inhibitors of human DHODH are known, to date there are no reports of medicinally viable leads against UCK2. Here, we use structure-based drug prototyping to identify two classes of promising leads that noncompetitively inhibit UCK2 activity. In the process, we have identified a hitherto unknown allosteric site at the intersubunit interface of this homotetrameric enzyme. By reducing the kcat of human UCK2 without altering its KM, these new inhibitors have the potential to enable systematic dialing of the fractional inhibition of pyrimidine salvage to achieve the desired antiviral effect with minimal host toxicity.
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Affiliation(s)
- Siavash Mashayekh
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Lee M Stunkard
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Maryline Kienle
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Chaitan Khosla
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.,Sarafan ChEM-H, Stanford University, Stanford, California 94305, United States
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7
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Demarest JF, Kienle M, Boytz R, Ayres M, Kim EJ, Patten JJ, Chung D, Gandhi V, Davey R, Sykes DB, Shohdy N, Pottage JC, Kumar VS. Brequinar and dipyridamole in combination exhibits synergistic antiviral activity against SARS-CoV-2 in vitro: Rationale for a host-acting antiviral treatment strategy for COVID-19. Antiviral Res 2022; 206:105403. [PMID: 36041646 PMCID: PMC9420051 DOI: 10.1016/j.antiviral.2022.105403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/28/2022] [Accepted: 08/23/2022] [Indexed: 11/25/2022]
Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19) and the associated global pandemic resulting in >400 million infections worldwide and several million deaths. The continued evolution of SARS-CoV-2 to potentially evade vaccines and monoclonal antibody (mAb)-based therapies and the limited number of authorized small-molecule antivirals necessitates the need for development of new drug treatments. There remains an unmet medical need for effective and convenient treatment options for SARS-CoV-2 infection. SARS-CoV-2 is an RNA virus that depends on host intracellular ribonucleotide pools for its replication. Dihydroorotate dehydrogenase (DHODH) is a ubiquitous host enzyme that is required for de novo pyrimidine synthesis. The inhibition of DHODH leads to a depletion of intracellular pyrimidines, thereby impacting viral replication in vitro. Brequinar (BRQ) is an orally available, selective, and potent low nanomolar inhibitor of human DHODH that has been shown to exhibit broad spectrum inhibition of RNA virus replication. However, host cell nucleotide salvage pathways can maintain intracellular pyrimidine levels and compensate for BRQ-mediated DHODH inhibition. In this report, we show that the combination of BRQ and the salvage pathway inhibitor dipyridamole (DPY) exhibits strong synergistic antiviral activity in vitro against SARS-CoV-2 by enhanced depletion of the cellular pyrimidine nucleotide pool. The combination of BRQ and DPY showed antiviral activity against the prototype SARS-CoV-2 as well as the Beta (B.1.351) and Delta (B.1.617.2) variants. These data support the continued evaluation of the combination of BRQ and DPY as a broad-spectrum, host-acting antiviral strategy to treat SARS-CoV-2 and potentially other RNA virus infections.
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Affiliation(s)
| | | | | | - Mary Ayres
- Department of Experimental Therapeutics, MD Anderson Cancer Center, Houston, TX, USA
| | | | | | | | - Varsha Gandhi
- Department of Experimental Therapeutics, MD Anderson Cancer Center, Houston, TX, USA
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8
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Matchett EC, Ambrose EC, Kornbluth J. Characterization of uridine-cytidine kinase like-1 nucleoside kinase activity and its role in tumor growth. Biochem J 2022; 479:1149-1164. [PMID: 35583288 PMCID: PMC9246348 DOI: 10.1042/bcj20210770] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 04/26/2022] [Accepted: 05/18/2022] [Indexed: 11/27/2022]
Abstract
Uridine-cytidine kinase like-1 (UCKL-1) is a largely uncharacterized protein with high sequence similarity to other uridine-cytidine kinases (UCKs). UCKs play an important role in the pyrimidine salvage pathway, catalyzing the phosphorylation of uridine and cytidine to UMP and CMP, respectively. Only two human UCKs have been identified, UCK1 and UCK2. Previous studies have shown both enzymes phosphorylate uridine and cytidine using ATP as the phosphate donor. No studies have evaluated the kinase potential of UCKL-1. We cloned and purified UCKL-1 and found that it successfully phosphorylated uridine and cytidine using ATP as the phosphate donor. The catalytic efficiency (calculated as kcat/KM) was 1.2 × 104 s-1, M-1 for uridine and 0.7 × 104 s-1, M-1 for cytidine. Our lab has previously shown that UCKL-1 is up-regulated in tumor cells, providing protection against natural killer (NK) cell killing activity. We utilized small interfering RNA (siRNA) to down-regulate UCKL-1 in vitro and in vivo to determine the effect of UCKL-1 on tumor growth and metastasis. The down-regulation of UCKL-1 in YAC-1 lymphoma cells in vitro resulted in decreased cell counts and increased apoptotic activity. Down-regulation of UCKL-1 in K562 leukemia cells in vivo led to decreased primary tumor growth and less tumor cell dissemination and metastasis. These results identify UCKL-1 as a bona fide pyrimidine kinase with the therapeutic potential to be a target for tumor growth inhibition and for diminishing or preventing metastasis.
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Affiliation(s)
- Emily C. Matchett
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO, U.S.A
| | - Elise C. Ambrose
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO, U.S.A
| | - Jacki Kornbluth
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO, U.S.A
- VA St. Louis Health Care System, St. Louis, MO, U.S.A
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9
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Stegmann KM, Dickmanns A, Heinen N, Blaurock C, Karrasch T, Breithaupt A, Klopfleisch R, Uhlig N, Eberlein V, Issmail L, Herrmann ST, Schreieck A, Peelen E, Kohlhof H, Sadeghi B, Riek A, Speakman JR, Groß U, Görlich D, Vitt D, Müller T, Grunwald T, Pfaender S, Balkema-Buschmann A, Dobbelstein M. Inhibitors of dihydroorotate dehydrogenase cooperate with Molnupiravir and N4-hydroxycytidine to suppress SARS-CoV-2 replication. iScience 2022; 25:104293. [PMID: 35492218 PMCID: PMC9035612 DOI: 10.1016/j.isci.2022.104293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/29/2022] [Accepted: 04/20/2022] [Indexed: 12/15/2022] Open
Abstract
The nucleoside analog N4-hydroxycytidine (NHC) is the active metabolite of the prodrug molnupiravir, which has been approved for the treatment of COVID-19. SARS-CoV-2 incorporates NHC into its RNA, resulting in defective virus genomes. Likewise, inhibitors of dihydroorotate dehydrogenase (DHODH) reduce virus yield upon infection, by suppressing the cellular synthesis of pyrimidines. Here, we show that NHC and DHODH inhibitors strongly synergize in the inhibition of SARS-CoV-2 replication in vitro. We propose that the lack of available pyrimidine nucleotides upon DHODH inhibition increases the incorporation of NHC into nascent viral RNA. This concept is supported by the rescue of virus replication upon addition of pyrimidine nucleosides to the media. DHODH inhibitors increased the antiviral efficiency of molnupiravir not only in organoids of human lung, but also in Syrian Gold hamsters and in K18-hACE2 mice. Combining molnupiravir with DHODH inhibitors may thus improve available therapy options for COVID-19. Molnupiravir and DHODH inhibitors are approved drugs, facilitating clinical testing The combination may allow lower drug doses to decrease possible toxic effects Inhibitors of nucleotide biosynthesis may boost antiviral nucleoside analogs
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Affiliation(s)
- Kim M Stegmann
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
| | - Antje Dickmanns
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
| | - Natalie Heinen
- Department of Molecular and Medical Virology, Ruhr University Bochum, Germany
| | - Claudia Blaurock
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald - Insel Riems, Germany
| | - Tim Karrasch
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
| | - Angele Breithaupt
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald - Insel Riems, Germany
| | | | - Nadja Uhlig
- Fraunhofer Institute for Cell Therapy and Immunology IZI, Leipzig, Germany
| | - Valentina Eberlein
- Fraunhofer Institute for Cell Therapy and Immunology IZI, Leipzig, Germany
| | - Leila Issmail
- Fraunhofer Institute for Cell Therapy and Immunology IZI, Leipzig, Germany
| | - Simon T Herrmann
- Department of Molecular Biochemistry, Ruhr University Bochum, Germany
| | | | | | | | - Balal Sadeghi
- Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Greifswald - Insel Riems, Germany
| | - Alexander Riek
- Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Celle, Germany
| | - John R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, UK
| | - Uwe Groß
- Institute of Medical Microbiology and Virology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Germany
| | - Dirk Görlich
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | - Thorsten Müller
- Department of Molecular Biochemistry, Ruhr University Bochum, Germany.,Institute of Psychiatric Phenomics and Genomics (IPPG), Organoid laboratory, University Hospital, LMU Munich, Germany
| | - Thomas Grunwald
- Fraunhofer Institute for Cell Therapy and Immunology IZI, Leipzig, Germany
| | - Stephanie Pfaender
- Department of Molecular and Medical Virology, Ruhr University Bochum, Germany
| | - Anne Balkema-Buschmann
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald - Insel Riems, Germany
| | - Matthias Dobbelstein
- Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Justus von Liebig Weg 11, 37077 Göttingen, Germany
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10
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Panigrahi D. Molecular Docking Analysis of the Phytochemicals from Tinospora Cordifolia as Potential Inhibitor Against Multi Targeted SARS-CoV-2 & Cytokine Storm. JOURNAL OF COMPUTATIONAL BIOPHYSICS AND CHEMISTRY 2021. [DOI: 10.1142/s2737416521500277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Severe acute respiratory syndrome coronavirus (SARS-CoV)-2, a novel coronavirus, is a member of the Coronoviridae family that has spread worldwide. Developing efficacious therapeutics for the treatment of SARS-CoV-2 is of high priority. Therefore, in this study, the chemical constituents obtained from Tinospora cordifolia are investigated for their in-silico interaction with protein targets crucial for SARSCoV-2 infection and cytokine storm. The five important targets chosen for SARSCoV-2 were the main protease (Mpro), Spike receptor binding domain (Spike-RBD), RNA-dependent RNA polymerase (RdRp or Nsp12), nonstructural protein 15 (Nsp15) of SARS-CoV-2 and the host angiotensin converting enzyme-2 (ACE-2) spike-RBD binding domain and cytokine receptors TNF-[Formula: see text] (Tumor Necrosis Factor-[Formula: see text]) and IL-6 (Interleukine-6). This was accomplished using Maestro 12.4 (Schrodinger Suite) to obtain docking scores. Also, the absorption, distribution, metabolism, elimination, and toxicity parameters (ADMET) were determined using Maestro QikProp modules. The results of computational study revealed that four constituents Cordifolioside-A, Palmatoside-E, Tinocordioside and Tinosporaside significantly antagonize the five targets of SARS-CoV-2 by binding in the binding pocket with docking score ranging from −9.664 to −6.488 kcal/mol and shows drug-like property and also effectively inhibit cytokine storm by antagonizing the TNF-[Formula: see text] and IL-6 receptors. Promising drug-like properties, excellent docking scores, and binding pose against each target makes the screened compounds as possible lead candidate which can be further evaluated in future studies to assess their in vitro and in vivo efficacy against SARS-CoV-2. The structure of these compounds can be used further for optimization and design of drugs against COVID-19.
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Affiliation(s)
- Debadash Panigrahi
- Drug Research Laboratory, Nodal Research Centre, College of Pharmaceutical Sciences, Puri, Baliguali, Puri-Konark Marine Drive Road, Puri, Odisha 752002, India
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11
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Insights on Dengue and Zika NS5 RNA-dependent RNA polymerase (RdRp) inhibitors. Eur J Med Chem 2021; 224:113698. [PMID: 34274831 DOI: 10.1016/j.ejmech.2021.113698] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/09/2021] [Accepted: 07/10/2021] [Indexed: 11/20/2022]
Abstract
Over recent years, many outbreaks caused by (re)emerging RNA viruses have been reported worldwide, including life-threatening Flaviviruses, such as Dengue (DENV) and Zika (ZIKV). Currently, there is only one licensed vaccine against Dengue, Dengvaxia®. However, its administration is not recommended for children under nine years. Still, there are no specific inhibitors available to treat these infectious diseases. Among the flaviviral proteins, NS5 RNA-dependent RNA polymerase (RdRp) is a metalloenzyme essential for viral replication, suggesting that it is a promising macromolecular target since it has no human homolog. Nowadays, several NS5 RdRp inhibitors have been reported, while none inhibitors are currently in clinical development. In this context, this review constitutes a comprehensive work focused on RdRp inhibitors from natural, synthetic, and even repurposing sources. Furthermore, their main aspects associated with the structure-activity relationship (SAR), proposed mechanisms of action, computational studies, and other topics will be discussed in detail.
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12
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Mazzarino RC. Targeting Future Pandemics, a Case for De Novo Purine Synthesis and Basic Research. Front Immunol 2021; 12:694300. [PMID: 34177959 PMCID: PMC8226072 DOI: 10.3389/fimmu.2021.694300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 05/21/2021] [Indexed: 12/25/2022] Open
Abstract
We are currently experiencing a deadly novel viral pandemic with no efficacious, readily available anti-viral therapies to SARS-CoV-2. Viruses will hijack host cellular machinery, including metabolic processes. Here, I provide theory and evidence for targeting the host de novo purine synthetic pathway for broad spectrum anti-viral drug development as well as the pursuit of basic science to mitigate the risks of future novel viral outbreaks.
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Affiliation(s)
- Randall C. Mazzarino
- Schepens Eye Research Institute of Mass Eye and Ear Infirmary and the Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
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Berber B, Doluca O. A comprehensive drug repurposing study for COVID19 treatment: novel putative dihydroorotate dehydrogenase inhibitors show association to serotonin-dopamine receptors. Brief Bioinform 2021; 22:1023-1037. [PMID: 33406218 PMCID: PMC7929379 DOI: 10.1093/bib/bbaa379] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/26/2020] [Accepted: 11/26/2020] [Indexed: 12/18/2022] Open
Abstract
Dihydroorotate dehydrogenase (DHODH) is a key enzyme required for de novo pyrimidine synthesis and it is suggested as a target for COVID19 treatment due to high pyrimidine demand by the virus replication in the infected host cells as well as its proven effect of blocking of cytokine release by the immune cells to prevent inflammation leading to acute respiratory distress. There are a number of clinical trials underway for COVID19 treatment using DHODH inhibitors; however, there are only a small number of known DHODH antagonists available for testing. Here, we have applied a methodology to identify DHODH antagonist candidates, and compared them using in silico target prediction tools. A large set of 7900 FDA-approved and clinical stage drugs obtained from DrugBank were docked against 20 different structures DHODH available in PDB. Drugs were eliminated according to their predicted affinities by Autodock Vina. About 28 FDA-approved and 79 clinical trial ongoing drugs remained. The mode of interaction of these molecules was analyzed by repeating docking using Autodock 4 and DS Visualiser. Finally, the target region predictions of 28 FDA-approved drugs were determined through PASS and SwissTargetPrediction tools. Interestingly, the analysis of in silico target predictions revealed that serotonin-dopamine receptor antagonists could also be potential DHODH inhibitors. Our candidates shared a common attribute, a possible interaction with serotonin-dopamine receptors as well as other oxidoreductases, like DHODH. Moreover, the Bruton Tyrosine Kinase-inhibitor acalabrutunib and serotonin-dopamine receptor inhibitor drugs on our list have been found in the literature that have shown to be effective against Sars-CoV-2, while the path of activity is yet to be identified. Identifying an effective drug that can suppress both inflammation and virus proliferation will play a crucial role in the treatment of COVID. Therefore, we suggest experimental investigation of the 28 FDA-approved drugs on DHODH activity and Sars-CoV-2 virus proliferation. Those who are found experimentally effective can play an important role in COVID19 treatment. Moreover, we suggest investigating COVID19 case conditions in patients using schizophrenia and depression drugs.
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Affiliation(s)
- Burak Berber
- Eskisehir Technical University, Department of Biology
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Effective deploying of a novel DHODH inhibitor against herpes simplex type 1 and type 2 replication. Antiviral Res 2021; 189:105057. [PMID: 33716051 DOI: 10.1016/j.antiviral.2021.105057] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/28/2021] [Accepted: 03/03/2021] [Indexed: 12/18/2022]
Abstract
Emergence of drug resistance and adverse effects often affect the efficacy of nucleoside analogues in the therapy of Herpes simplex type 1 (HSV-1) and type 2 (HSV-2) infections. Host-targeting antivirals could therefore be considered as an alternative or complementary strategy in the management of HSV infections. To contribute to this advancement, here we report on the ability of a new generation inhibitor of a key cellular enzyme of de novo pyrimidine biosynthesis, the dihydroorotate dehydrogenase (DHODH), to inhibit HSV-1 and HSV-2 in vitro replication, with a potency comparable to that of the reference drug acyclovir. Analysis of the HSV replication cycle in MEDS433-treated cells revealed that it prevented the accumulation of viral genomes and reduced late gene expression, thus suggesting an impairment at a stage prior to viral DNA replication consistent with the ability of MEDS433 to inhibit DHODH activity. In fact, the anti-HSV activity of MEDS433 was abrogated by the addition of exogenous uridine or of the product of DHODH, the orotate, thus confirming DHODH as the MEDS433 specific target in HSV-infected cells. A combination of MEDS433 with dipyridamole (DPY), an inhibitor of the pyrimidine salvage pathway, was then observed to be effective in inhibiting HSV replication even in the presence of exogenous uridine, thus mimicking in vivo conditions. Finally, when combined with acyclovir and DPY in checkerboard experiments, MEDS433 exhibited highly synergistic antiviral activity. Taken together, these findings suggest that MEDS433 is a promising candidate as either single agent or in combination regimens with existing direct-acting anti-HSV drugs to develop new strategies for treatment of HSV infections.
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Zhan SC, Fang RJ, Yang RY, Zhao RF, Wang Y, Sun J, Yan CG. DDQ dehydrogenative Diels–Alder reaction for the synthesis of functionalized spiro[carbazole-1,3′-indolines] and spiro[carbazole-1,5′-pyrimidines]. NEW J CHEM 2021. [DOI: 10.1039/d1nj02836g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Reactive 3-vinylindoles were generated by in situ DDQ oxidative dehydrogenation of 3-(indol-3-yl)-1,3-diphenylpropan-1-ones, and underwent sequential Diels–Alder reaction to give novel heterocyclic spirocarbazoles.
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Affiliation(s)
- Shao-Cong Zhan
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Ren-Jie Fang
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Ren-Yin Yang
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Ru-Fang Zhao
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Yang Wang
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Jing Sun
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
| | - Chao-Guo Yan
- College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, China
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Aliter KF, Al-Horani RA. Potential Therapeutic Benefits of Dipyridamole in COVID-19 Patients. Curr Pharm Des 2021; 27:866-875. [PMID: 33001004 PMCID: PMC7990686 DOI: 10.2174/1381612826666201001125604] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/31/2020] [Indexed: 12/15/2022]
Abstract
BACKGROUND COVID-19 pandemic is caused by coronavirus also known as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The viral infection continues to impact the globe with no vaccine to prevent the infection or highly effective therapeutics to treat the millions of infected people around the world. The disease starts as a respiratory infection, yet it may also be associated with a hypercoagulable state, severe inflammation owing to excessive cytokines production, and a potentially significant oxidative stress. The disease may progress to multiorgan failure and eventually death. OBJECTIVE In this article, we summarize the potential of dipyridamole as an adjunct therapy for COVID-19. METHODS We reviewed the literature describing the biological activities of dipyridamole in various settings of testing. Data were retrieved from PubMed, SciFinder-CAS, and Web of Science. The review concisely covered relevant studies starting from 1977. RESULTS Dipyridamole is an approved antiplatelet drug, that has been used to prevent stroke, among other indications. Besides its antithrombotic activity, the literature indicates that dipyridamole also promotes a host of other biological activities including antiviral, anti-inflammatory, and antioxidant ones. CONCLUSION Dipyridamole may substantially help improve the clinical outcomes of COVID-19 treatment. The pharmacokinetics profile of the drug is well established which makes it easier to design an appropriate therapeutic course. The drug is also generally safe, affordable, and available worldwide. Initial clinical trials have shown a substantial promise for dipyridamole in treating critically ill COVID-19 patients, yet larger randomized and controlled trials are needed to confirm this promise.
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Affiliation(s)
- Kholoud F. Aliter
- Department of Chemistry, School of STEM, Dillard University, New Orleans LA70122, USA
| | - Rami A. Al-Horani
- Division of Basic Pharmaceutical Sciences, College of Pharmacy, Xavier University of Louisiana, New Orleans LA70125, USA
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17
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Shafer RW. A SARS-CoV-2 antiviral therapy score card. Glob Health Med 2020; 2:346-349. [PMID: 33409413 PMCID: PMC7780285 DOI: 10.35772/ghm.2020.01082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/07/2020] [Accepted: 09/13/2020] [Indexed: 06/12/2023]
Abstract
The COVID-19 pandemic has unleashed an unprecedented effort to identify efficacious treatments for persons infected with SARS-CoV-2. As of September 2020, more than 750 completed, ongoing, or planned clinical trials of drugs intended to inhibit SARS-CoV-2 replication have been registered on the ClinicalTrials.gov or WHO International Clinical Trials Platform websites. Most of the treatments studied in these trials are repurposed licensed or investigational drugs targeting viral proteins or cellular pathways required for virus replication. The use of repurposed compounds is understandable because with the exception of monoclonal antibodies, it will be several months before novel SARS-CoV-2-specific drugs will be available for human testing. This editorial describes those compounds that I believe should be prioritized for clinical testing: i) viral RNA polymerase inhibitors including GS-441524, its prodrug remdesivir, and EIDD-2801; ii) entry inhibitors including monoclonal antibodies, ACE2 molecular decoys, and peptide fusion inhibitors; iii) parenteral and inhalational preparations of interferon β and λ; and iv) inhibitors of host transmembrane protease serine 2 (TMPRSS2), endosomal trafficking, and pyrimidine synthesis. As SARS-CoV-2 is pandemic and as its most severe consequences result from a dysregulated immunological response to infection, the ideal therapies should be inexpensive and should be able to be administered to non-hospitalized persons at the time of their initial diagnosis.
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Affiliation(s)
- Robert W. Shafer
- Address correspondence to:Robert W. Shafer, Division of Infectious Diseases, Department of Medicine, Stanford University, Stanford, 1000 Welch Rd Ste 202, Palo Alto, CA 94304, USA. E-mail:
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Yang S, Wu S, Yu Z, Huang J, Zhong X, Liu X, Zhu H, Xiao L, Deng Q, Sun W. Transcriptomic analysis reveals novel mechanisms of SARS-CoV-2 infection in human lung cells. IMMUNITY INFLAMMATION AND DISEASE 2020; 8:753-762. [PMID: 33124193 PMCID: PMC7654422 DOI: 10.1002/iid3.366] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 12/24/2022]
Abstract
Background Severe acute respiratory syndrome coronavirus clade 2 (SARS‐CoV‐2) is a single‐stranded RNA virus responsible for the global pandemic of the coronavirus disease‐2019 (COVID‐19). To date, there are still no effective approaches for the prevention and treatment of COVID‐19. Objective The present study aims to explore the possible mechanisms of SARS‐CoV‐2 infection in human lung cells. Methods Data interpretation was conducted by recruiting bioinformatics analysis, including Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways analysis using downloaded data from the NCBI Gene Expression Omnibus database. Results The present study demonstrated that SARS‐CoV‐2 infection induces the upregulation of 14 interferon‐stimulated genes, indicative of immune, and interferon responses to the virus. Notably, genes for pyrimidine metabolism and steroid hormone biosynthesis are selectively enriched in human lung cells after SARS‐CoV‐2 infection, suggesting that altered pyrimidine metabolism and steroid biosynthesis are remarkable, and perhaps druggable features after SARS‐CoV‐2 infection. Besides, there is a strong positive correlation between viral ORF1ab, ORF6, and angiotensin‐converting enzyme 2 (ACE2) expression in human lung cells, implying that ACE2 facilitates SARS‐CoV‐2 infection and replication in host cells probably through the induction of ORF1ab and ORF6.
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Affiliation(s)
- Shaomin Yang
- Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China.,Jinan University, Guangzhou, China
| | - Songbin Wu
- Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Zhijian Yu
- Department of Infectious Diseases and Shenzhen Municipal Key Laboratory for Endogenous Infection, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Jiabin Huang
- Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | | | - Xiaodong Liu
- Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong
| | - Hua Zhu
- Jinan University, Guangzhou, China.,Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Lizu Xiao
- Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Qiwen Deng
- Department of Infectious Diseases and Shenzhen Municipal Key Laboratory for Endogenous Infection, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Wuping Sun
- Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, Shenzhen Nanshan People's Hospital, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
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Tzou PL, Tao K, Nouhin J, Rhee SY, Hu BD, Pai S, Parkin N, Shafer RW. Coronavirus Antiviral Research Database (CoV-RDB): An Online Database Designed to Facilitate Comparisons between Candidate Anti-Coronavirus Compounds. Viruses 2020; 12:E1006. [PMID: 32916958 PMCID: PMC7551675 DOI: 10.3390/v12091006] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/29/2020] [Accepted: 09/04/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND To prioritize the development of antiviral compounds, it is necessary to compare their relative preclinical activity and clinical efficacy. METHODS We reviewed in vitro, animal model, and clinical studies of candidate anti-coronavirus compounds and placed extracted data in an online relational database. RESULTS As of August 2020, the Coronavirus Antiviral Research Database (CoV-RDB; covdb.stanford.edu) contained over 2800 cell culture, entry assay, and biochemical experiments, 259 animal model studies, and 73 clinical studies from over 400 published papers. SARS-CoV-2, SARS-CoV, and MERS-CoV account for 85% of the data. Approximately 75% of experiments involved compounds with known or likely mechanisms of action, including monoclonal antibodies and receptor binding inhibitors (21%), viral protease inhibitors (17%), miscellaneous host-acting inhibitors (10%), polymerase inhibitors (9%), interferons (7%), fusion inhibitors (5%), and host protease inhibitors (5%). Of 975 compounds with known or likely mechanism, 135 (14%) are licensed in the U.S. for other indications, 197 (20%) are licensed outside the U.S. or are in human trials, and 595 (61%) are pre-clinical investigational compounds. CONCLUSION CoV-RDB facilitates comparisons between different candidate antiviral compounds, thereby helping scientists, clinical investigators, public health officials, and funding agencies prioritize the most promising compounds and repurposed drugs for further development.
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Affiliation(s)
- Philip L. Tzou
- Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA 94305, USA; (K.T.); (J.N.); (S.-Y.R.)
| | - Kaiming Tao
- Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA 94305, USA; (K.T.); (J.N.); (S.-Y.R.)
| | - Janin Nouhin
- Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA 94305, USA; (K.T.); (J.N.); (S.-Y.R.)
| | - Soo-Yon Rhee
- Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA 94305, USA; (K.T.); (J.N.); (S.-Y.R.)
| | - Benjamin D. Hu
- Undergraduate School of Humanities and Sciences, Stanford University, Stanford, CA 94305, USA;
| | - Shruti Pai
- Undergraduate Studies, University of California, Berkeley, CA 94720, USA;
| | - Neil Parkin
- Data First Consulting Inc., Sebastopol, CA 95472, USA;
| | - Robert W. Shafer
- Division of Infectious Diseases, Stanford University School of Medicine, Stanford, CA 94305, USA; (K.T.); (J.N.); (S.-Y.R.)
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