Clinical Efficacy of Remdesivir and Favipiravir in the Treatment of Covid-19 Patients: Scenario So Far

: The novel SARS-CoV-2 is a new disease that has caused severe destruction to human lives across the globe, including infection, mortality and financial crises, for which, scientific researchers have been directed towards the development of treatment and controlling measures against coronavirus. Currently, there has been no approved drug for the treatment of the disease, but several antiviral drugs have shown therapeutic effects from which, remdesivir and favipiravir are two such drugs. These drugs have shown some therapeutic potential in the treatment of COVID-19 by inhibiting viral enzyme RNA-dependent RNA polymerase. The purpose of this systematic review is to provide an overview of the effectiveness of these two drugs based on the clinical trials reported in current published data.

Drug Repurposing Approach, Potential Drugs, and Novel Drug Targets for COVID-19 Treatment

Novel coronavirus first appeared in Wuhan, China, in December 2019, and it speedily expanded globally. Some medications which are used to treat other diseases seem to be effective in treating COVID-19 even without explicit support. The existing drugs that are summarized in this review primarily focused on therapeutic agents that possessed activity against other RNA viruses such as MERS-CoV and SARS-CoV. Drug repurposing or repositioning is a promising field in drug discovery that identifies new therapeutic opportunities for existing drugs such as corticosteroids, RNA-dependent RNA polymerase inhibitors, interferons, protease inhibitors, ivermectin, melatonin, teicoplanin, and some others. A search for new drug/drug targets is underway. Thus, blocking coronavirus structural protein, targeting viral enzyme, dipeptidyl peptidase 4, and membrane fusion blocker (angiotensin-converting enzyme 2 and CD147 inhibitor) are major sites based on molecular targets for the management of COVID-19 infection. The possible impact of biologics for the management of COVID19 is promising and includes a wide variety of options such as cytokines, nucleic acid-based therapies targeting virus gene expression, bioengineered and vectored antibodies, and various types of vaccines. This review demonstrates that the available data are not sufficient to suggest any treatment for the eradication of COVID-19 to be used at the clinical level. This article aims to review the roles of existing drugs and drug targets for COVID-19 treatment.

Potential Candidates against COVID-19 Targeting RNA-Dependent RNA Polymerase: A Comprehensive Review

: Due to the extremely contagious nature of SARS-COV-2, it presents a significant threat to humans worldwide. A plethora of studies are going on all over the world to discover the drug to fight SARS-COV-2. One of the most promising targets is RNA-dependent RNA polymerase (RdRp), responsible for viral RNA replication in host cells. Since RdRp is a viral enzyme with no host cell homologs, it allows the development of selective SARS-COV-2 RdRp inhibitors. A variety of studies used in silico approaches for virtual screening, molecular docking, and repurposing of already existing drugs and phytochemicals against SARS-COV-2 RdRp. This review focuses on collating compounds possessing the potential to inhibit SARS-COV-2 RdRp based on in silico studies to give medicinal chemists food for thought so that the existing drugs can be repurposed for the control and treatment of ongoing COVID-19 pandemic after performing in vitro and in vivo experiments.

Coronavirus-Replikation: Mechanismus und Inhibition durch Remdesivir

Coronaviruses use an RNA-dependent RNA polymerase to replicate and transcribe their RNA genome. The structure of the SARS-CoV-2 polymerase was determined by cryo-electron microscopy within a short time in spring 2020. The structure explains how the viral enzyme synthesizes RNA and how it replicates the exceptionally large genome in a processive manner. The most recent structure-function studies further reveal the mechanism of polymerase inhibition by remdesivir, an approved drug for the treatment of COVID-19.

Identification of SARS-CoV-2 3CL Protease Inhibitors by a Quantitative High-throughput Screening

The outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emphasized the urgency to develop effective therapeutics. Drug repurposing screening is regarded as one of the most practical and rapid approaches for the discovery of such therapeutics. The 3C like protease (3CLpro), or main protease (Mpro) of SARS-CoV-2 is a valid drug target as it is a specific viral enzyme and plays an essential role in viral replication. We performed a quantitative high throughput screening (qHTS) of 10,755 compounds consisting of approved and investigational drugs, and bioactive compounds using a SARS-CoV-2 3CLpro assay. Twenty-three small molecule inhibitors of SARS-CoV-2 3CLpro have been identified with IC50s ranging from 0.26 to 28.85 μM. Walrycin B (IC50 = 0.26 µM), Hydroxocobalamin (IC50 = 3.29 µM), Suramin sodium (IC50 = 6.5 µM), Z-DEVD-FMK (IC50 = 6.81 µM), LLL-12 (IC50 = 9.84 µM), and Z-FA-FMK (IC50 = 11.39 µM) are the most potent 3CLpro inhibitors. The activities of anti-SARS-CoV-2 viral infection was confirmed in 7 of 23 compounds using a SARS-CoV-2 cytopathic effect assay. The results demonstrated a set of SARS-CoV-2 3CLpro inhibitors that may have potential for further clinical evaluation as part of drug combination therapies to treating COVID-19 patients, and as starting points for chemistry optimization for new drug development.

RNA-Dependent RNA Polymerase as a Target for COVID-19 Drug Discovery

COVID-19 respiratory disease caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has rapidly become a global health issue since it emerged in December 2019. While great global efforts are underway to develop vaccines and to discover or repurpose therapeutic agents for this disease, as of this writing only the nucleoside drug remdesivir has been approved under Emergency Use Authorization to treat COVID-19. The RNA-dependent RNA polymerase (RdRP), a viral enzyme for viral RNA replication in host cells, is one of the most intriguing and promising drug targets for SARS-CoV-2 drug development. Because RdRP is a viral enzyme with no host cell homologs, selective SARS-CoV-2 RdRP inhibitors can be developed that have improved potency and fewer off-target effects against human host proteins and thus are safer and more effective therapeutics for treating COVID-19. This review focuses on biochemical enzyme and cell-based assays for RdRPs that could be used in high-throughput screening to discover new and repurposed drugs against SARS-CoV-2.

In Silico Screening of Phytochemicals of Ocimum Sanctum Against Main Protease of SARS-CoV-2

<div>COVID19 has compelled the scientific community to search for an effective drug that can cure; a vaccine or an immunity booster that can prevent the disease. As of now, it is tough to discover a new drug and vaccine discovery is even tougher. Drug repurposing is a shortcut to drug discovery for COVID19. Even this has been proved unsatisfactory. Symptomatic treatment and immunity boosters are only alternatives left. Holy Tulsi (Ocimum sanctum) has been known as an ancient remedy for cure of common cold and respiratory ailment in India vis-a-vis also has been prescribed as one of the recommended ingredients in the immunity booster preparations. The ethanolic extract of aerial parts of Tulsi is reported to contain flavonoids and polyphenolic acids, which are also reported earlier to have anti-viral properties experimentally. Therefore, we undertake the in silico analysis of the phytochemicals as inhibitors of main protease of SARS-CoV-2 virus. The result suggests that the flavonoids and polyphenolic compounds of Tulsi, especially luteolin-7-O-glucuronide and chlorogenic acid may covalently bind to the active residue Cys145 of main protease and irreversibly inhibit the viral enzyme. Further experimental validations are required to establish the theoretical findings. <br></div>

In Silico Screening of Phytochemicals of Ocimum Sanctum Against Main Protease of SARS-CoV-2

<div>COVID19 has compelled the scientific community to search for an effective drug that can cure; a vaccine or an immunity booster that can prevent the disease. As of now, it is tough to discover a new drug and vaccine discovery is even tougher. Drug repurposing is a shortcut to drug discovery for COVID19. Even this has been proved unsatisfactory. Symptomatic treatment and immunity boosters are only alternatives left. Holy Tulsi (Ocimum sanctum) has been known as an ancient remedy for cure of common cold and respiratory ailment in India vis-a-vis also has been prescribed as one of the recommended ingredients in the immunity booster preparations. The ethanolic extract of aerial parts of Tulsi is reported to contain flavonoids and polyphenolic acids, which are also reported earlier to have anti-viral properties experimentally. Therefore, we undertake the in silico analysis of the phytochemicals as inhibitors of main protease of SARS-CoV-2 virus. The result suggests that the flavonoids and polyphenolic compounds of Tulsi, especially luteolin-7-O-glucuronide and chlorogenic acid may covalently bind to the active residue Cys145 of main protease and irreversibly inhibit the viral enzyme. Further experimental validations are required to establish the theoretical findings. <br></div>

HIV-1 Mutant Assembly, Processing and Infectivity Expresses Pol Independent of Gag

The pol retrovirus gene encodes required enzymes for virus replication and maturation. Unlike HIV-1 Pol (expressed as a Gag–Pol fusion protein), foamy virus (described as an ancient retrovirus) expresses Pol without forming Gag–Pol polyproteins. We placed a “self-cleaving” 2A peptide between HIV-1 Gag and Pol. This construct, designated G2AP, is capable of producing virions with the same density as a wild-type (wt) HIV-1 particle. The 2A peptide allows for Pol to be packaged into virions independently from Gag following co-translationally cleaved from Gag. We found that G2AP exhibited only one-third the virus infectivity of the wt, likely due, at least in part, to defects in Pol packaging. Attenuated protease (PR) activity, or a reduction in Pol expression due to the placement of 2A-mediated Pol in a normal Gag–Pol frameshift context, resulted in significant increases in virus yields and/or titers. This suggests that reduced G2AP virus yields were largely due to increased PR activity associated with overexpressed Pol. Our data suggest that HIV-1 adopts a gag/pol ribosomal frameshifting mechanism to support virus assembly via the efficient modulation of Gag–Pol/Gag expression, as well as to promote viral enzyme packaging. Our results help clarify the molecular basis of HIV-1 gene expression and assembly.

Zika Virus Targeting by Screening Inhibitors against NS2B/NS3 Protease

Zika flavivirus is suspected to cause Guillain-Barre syndrome in adults and microcephaly, along with other congenital abnormalities in infants. Presently, no vaccines or therapeutics are available. Here, we report novel compounds identified by high-throughput virtual screening of Maybridge chemical database and molecular docking studies. We selected viral enzyme NS2B/NS3 serine protease as the therapeutic target because of its important role in viral replication. We selected seven potential compounds as antiviral drug candidates because of their high GOLD fitness score, high AutoDock Vina score, or X-Score binding energy and analyzed the strength of molecular interactions between the active site amino acids and selected compounds. Our study also provides a foundation for similar studies for the search of novel therapeutics against Zika virus.