Favipiravir, an anti-influenza drug against life-threatening RNA virus infections

The impact of high-resolution structural data on stemming the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has had a catastrophic impact on human health and the world economy. The response of the scientific community was unparalleled, and a combined global effort has resulted in the creation of vaccines in a shorter time frame than previously unimaginable. Reflecting this concerted effort, the structural analysis of the etiological agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has progressed with an unprecedented pace. Since the onset of the pandemic, over 1000 high-resolution structures of a broad range of SARS-CoV-2 proteins have been solved and made publicly available. These structures have aided in the identification of numerous potential druggable targets and have contributed to the design of different vaccine candidates. This opinion article will discuss the impact of high-resolution structures in understanding SARS-CoV-2 biology and explore their role in the development of vaccines and antivirals.

Antiviral Drug Delivery System for Enhanced Bioactivity, Better Metabolism and Pharmacokinetic Characteristics

Antiviral drugs (AvDs) are the primary resource in the global battle against viruses, including the recent fight against corona virus disease 2019 (COVID-19). Most AvDs require multiple medications, and their use frequently leads to drug resistance, since they have poor oral bioavailability and low efficacy due to their low solubility/low permeability. Characterizing the in vivo metabolism and pharmacokinetic characteristics of AvDs may help to solve the problems associated with AvDs and enhance their efficacy. In this review of AvDs, we systematically investigated their structure-based metabolic reactions and related enzymes, their cellular pharmacology, and the effects of metabolism on AvD pharmacodynamics and pharmacokinetics. We further assessed how delivery systems achieve better metabolism and pharmacology of AvDs. This review suggests that suitable nanosystems may help to achieve better pharmacological activity and pharmacokinetic behavior of AvDs by altering drug metabolism through the utilization of advanced nanotechnology and appropriate administration routes. Notably, such AvDs as ribavirin, remdesivir, favipiravir, chloroquine, lopinavir and ritonavir have been confirmed to bind to the severe acute respiratory syndrome-like coronavirus (SARS-CoV-2) receptor and thus may represent anti-COVID-19 treatments. Elucidating the metabolic and pharmacokinetic characteristics of AvDs may help pharmacologists to identify new formulations with high bioavailability and efficacy and help physicians to better treat virus-related diseases, including COVID-19.

Plain 1 H nuclear magnetic resonance analysis streamlines the quality control of antiviral favipiravir and congeneric World Health Organization essential medicines

Favipiravir is an established antiviral that is currently being assessed as an investigational drug for the treatment of COVID-19. Favipiravir is strikingly similar to two molecules that the World Health Organization (WHO) lists as essential medicines, which also consist of a six-membered aromatic N-heterocycle bearing a carboxamide function: the anti-tuberculosis agent, pyrazinamide, and nicotinamide, also known as vitamin B₃ . We demonstrate the utility of ¹ H nuclear magnetic resonance (NMR) profiling, an emerging pharmacopoeial tool, for the highly specific identification, selective differentiation of congeners, and subsequent detection of drug falsification or adulteration of these medicines. The straightforward comparison of basic 1-D ¹ H NMR spectra, obtained with benchtop or advanced NMR instruments alike, offers a rapid identity assay and works independently of physical reference materials. This approach accelerates and advances pharmaceutical quality control measures under situations of increased drug demand and altered economy, such as during a pandemic.

Influenza virus and SARS-CoV-2: pathogenesis and host responses in the respiratory tract

Influenza viruses cause annual epidemics and occasional pandemics of respiratory tract infections that produce a wide spectrum of clinical disease severity in humans. The novel betacoronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 and has since caused a pandemic. Both viral and host factors determine the extent and severity of virus-induced lung damage. The host's response to viral infection is necessary for viral clearance but may be deleterious and contribute to severe disease phenotypes. Similarly, tissue repair mechanisms are required for recovery from infection across the spectrum of disease severity; however, dysregulated repair responses may lead to chronic lung dysfunction. Understanding of the mechanisms of immunopathology and tissue repair following viral lower respiratory tract infection may broaden treatment options. In this Review, we discuss the pathogenesis, the contribution of the host response to severe clinical phenotypes and highlight early and late epithelial repair mechanisms following influenza virus infection, each of which has been well characterized. Although we are still learning about SARS-CoV-2 and its disease manifestations in humans, throughout the Review we discuss what is known about SARS-CoV-2 in the context of this broad knowledge of influenza virus, highlighting the similarities and differences between the respiratory viruses.

Potent toxic effects of Taroxaz-104 on the replication of SARS-CoV-2 particles

Polyphenolics and 1,3,4-oxadiazoles are two of the most potent bioactive classes of compounds in medicinal chemistry, since both are known for their diverse pharmacological activities in humans. One of their prominent activities is the antimicrobial/antiviral activities, which are much apparent when the key functional structural moieties of both of them meet into the same compounds. The current COVID-19 pandemic motivated us to computationally screen and evaluate our library of previously-synthesized 2-(3,4,5-trihydroxyphenyl)-1,3,4-oxadiazoles against the major SARS-CoV-2 protein targets. Interestingly, few ligands showed promising low binding free energies (potent inhibitory interactions/affinities) with the active sites of some coronaviral-2 enzymes, specially the RNA-dependent RNA polymerase (nCoV-RdRp). One of them was 5,5'-{5,5'-[(1R,2R)-1,2-dihydroxyethane-1,2-diyl]bis(1,3,4-oxadiazole-5,2-diyl)}dibenzene-1,2,3-triol (Taroxaz-104), which showed significantly low binding energies (-10.60 and -9.10 kcal/mol) with nCoV-RdRp-RNA and nCoV-RdRp alone, respectively. These binding energies are even considerably lower than those of remdesivir potent active metabolite GS-443902 (which showed -9.20 and -7.90 kcal/mol with the same targets, respectively). Further computational molecular investigation revealed that Taroxaz-104 molecule strongly inhibits one of the potential active sites of nCoV-RdRp (the one with which GS-443902 molecule mainly interacts), since it interacts with at least seven major active amino acid residues of its predicted pocket. The successful repurposing of Taroxaz-104 has been achieved after the promising results of the anti-COVID-19 biological assay were obtained, as the data showed that Taroxaz-104 exhibited very significant anti-COVID-19 activities (anti-SARS-CoV-2 EC₅₀ = 0.42 μM) with interesting effectiveness against the new strains/variants of SARS-CoV-2. Further investigations for the development of Taroxaz-104 and its coming polyphenolic 2,5-disubstituted-1,3,4-oxadiazole derivatives as anti-COVID-19 drugs, through in vivo bioevaluations and clinical trials research, are urgently needed.

Investigation of the disease process and drug combinations in patients with suspected/confirmed COVID-19 using favipiravir

AIMS

It is aimed to investigate the disease processes and drug combinations in patients who received favipiravir treatment.

METHODS

This cross-sectional, analytical and retrospective study included all patients aged ≥18 years (n = 502) who were hospitalised in Samsun, Turkey, for COVID-19 and were given favipiravir from the date between 25 March 2020 and 3 June 2020.

RESULTS

In total, 58.6% (n = 294) of the patients were male and 24.5% (n = 123) were between the ages of 71 and 80 years. During the first case process, the mortality rate was 19.9%, whereas the rate of those who were discharged as is/followed up at home for 14 days was 37.3%. During the second case process, the mortality rate was 6.2%, and the rate of those who was discharged as is/followed up at home for 14 days was 65.6%. The mean length of hospital stay was 10.61 ± 8.17 days for the first and 7.97 ± 4.16 days for the second hospitalisation; this difference was significant. Mortality risk of those who used Tocilizumab or vitamin C beside Favipiravir was higher than those who did not. The length of hospital stay was higher in patients using tocilizumab than in those who did not (P < .001).

CONCLUSION

Administration of favipiravir later in the course of the disease makes it difficult to achieve the true efficacy expected from the drug and also makes it difficult for other combination drugs to contribute to survival. Favipiravir may also be effective in case of recurrence.

Electron Density Analysis of SARS-CoV-2 RNA-Dependent RNA Polymerase Complexes

The work is devoted to the study of the complementarity of the electronic structures of the ligands and SARS-CoV-2 RNA-dependent RNA polymerase. The research methodology was based on determining of 3D maps of electron densities of complexes using an original quantum free-orbital AlteQ approach. We observed a positive relationship between the parameters of the electronic structure of the enzyme and ligands. A complementarity factor of the enzyme-ligand complexes has been proposed. The console applications of the AlteQ complementarity assessment for Windows and Linux (alteq_map_enzyme_ligand_4_win.exe and alteq_map_enzyme_ligand_4_linux) are available for free at the ChemoSophia webpage.

Comprehensive Profiling of Mutations to Influenza Virus PB2 That Confer Resistance to the Cap-Binding Inhibitor Pimodivir

Antivirals are used not only in the current treatment of influenza but are also stockpiled as a first line of defense against novel influenza strains for which vaccines have yet to be developed. Identifying drug resistance mutations can guide the clinical deployment of the antiviral and can additionally define the mechanisms of drug action and drug resistance. Pimodivir is a first-in-class inhibitor of the polymerase basic protein 2 (PB2) subunit of the influenza A virus polymerase complex. A number of resistance mutations have previously been identified in treated patients or cell culture. Here, we generate a complete map of the effect of all single-amino-acid mutations to an avian PB2 on resistance to pimodivir. We identified both known and novel resistance mutations not only in the previously implicated cap-binding and mid-link domains, but also in the N-terminal domain. Our complete map of pimodivir resistance thus enables the evaluation of whether new viral strains contain mutations that will confer pimodivir resistance.

Antiviral Efficacy of Ribavirin and Favipiravir against Hantaan Virus

Ecological changes, population movements and increasing urbanization promote the expansion of hantaviruses, placing humans at high risk of virus transmission and consequent diseases. The currently limited therapeutic options make the development of antiviral strategies an urgent need. Ribavirin is the only antiviral used currently to treat hemorrhagic fever with renal syndrome (HFRS) caused by Hantaan virus (HTNV), even though severe side effects are associated with this drug. We therefore investigated the antiviral activity of favipiravir, a new antiviral agent against RNA viruses. Both ribavirin and favipiravir demonstrated similar potent antiviral activity on HTNV infection. When combined, the efficacy of ribavirin is enhanced through the addition of low dose favipiravir, highlighting the possibility to provide better treatment than is currently available.

Drug Repurposing: A Strategy for Discovering Inhibitors against Emerging Viral Infections

BACKGROUND

Viral diseases are responsible for several deaths around the world. Over the past few years, the world has seen several outbreaks caused by viral diseases that, for a long time, seemed to possess no risk. These are diseases that have been forgotten for a long time and, until nowadays, there are no approved drugs or vaccines, leading the pharmaceutical industry and several research groups to run out of time in the search for new pharmacological treatments or prevention methods. In this context, drug repurposing proves to be a fast and economically viable technique, considering the fact that it uses drugs that have a well-established safety profile. Thus, in this review, we present the main advances in drug repurposing and their benefit for searching new treatments against emerging viral diseases.

METHODS

We conducted a search in the bibliographic databases (Science Direct, Bentham Science, PubMed, Springer, ACS Publisher, Wiley, and NIH's COVID-19 Portfolio) using the keywords "drug repurposing", "emerging viral infections" and each of the diseases reported here (CoV; ZIKV; DENV; CHIKV; EBOV and MARV) as an inclusion/exclusion criterion. A subjective analysis was performed regarding the quality of the works for inclusion in this manuscript. Thus, the selected works were those that presented drugs repositioned against the emerging viral diseases presented here by means of computational, high-throughput screening or phenotype-based strategies, with no time limit and of relevant scientific value.

RESULTS

291 papers were selected, 24 of which were CHIKV; 52 for ZIKV; 43 for DENV; 35 for EBOV; 10 for MARV; and 56 for CoV and the rest (72 papers) related to the drugs repurposing and emerging viral diseases. Among CoV-related articles, most were published in 2020 (31 papers), updating the current topic. Besides, between the years 2003 - 2005, 10 articles were created, and from 2011 - 2015, there were 7 articles, portraying the outbreaks that occurred at that time. For ZIKV, similar to CoV, most publications were during the period of outbreaks between the years 2016 - 2017 (23 articles). Similarly, most CHIKV (13 papers) and DENV (14 papers) publications occur at the same time interval. For EBOV (13 papers) and MARV (4 papers), they were between the years 2015 - 2016. Through this review, several drugs were highlighted that can be evolved in vivo and clinical trials as possible used against these pathogens showed that remdesivir represent potential treatments against CoV. Furthermore, ribavirin may also be a potential treatment against CHIKV; sofosbuvir against ZIKV; celgosivir against DENV, and favipiravir against EBOV and MARV, representing new hopes against these pathogens.

CONCLUSION

The conclusions of this review manuscript show the potential of the drug repurposing strategy in the discovery of new pharmaceutical products, as from this approach, drugs could be used against emerging viral diseases. Thus, this strategy deserves more attention among research groups and is a promising approach to the discovery of new drugs against emerging viral diseases and also other diseases.

Virological and genomic analysis of SARS-CoV-2 from a favipiravir clinical trial cohort

INTRODUCTION

Several clinical studies have reported the efficacy of favipiravir in reducing viral load and shortening the duration of symptoms. However, the viability of SARS-CoV-2 in the context of favipiravir therapy and the potential for resistance development is unclear.

METHODS

We sequenced SARS-CoV-2 in nasopharyngeal specimens collected from patients who participated in a randomized clinical trial of favipiravir at hospitals across Japan between March and May 2020. Paired genomes were sequenced from those who remained RT-PCR-positive 5-8 days into favipiravir therapy. Daily nasopharyngeal specimens from 69 patients who were RT-PCR-positive at randomization were examined for a cytopathic effect (CPE).

RESULTS

Some strains early in the trial belonged to clade 19 B, whereas the majority belonged to clade 20 B. The median time from the disease onset to negative CPE was 9 days. CPE was strongly correlated with the time from disease onset, viral load, age, and male sex. Among 23 patients for whom paired genomes were available, all except one had identical genomes. Two mutations were observed in one patient who received favipiravir, neither in the RdRp gene.

CONCLUSIONS

The SARS-CoV-2 genome distribution in this clinical trial conducted in Japan reflected the early influx of strains from China followed by replacement by strains from Europe. CPE was significantly associated with age, male sex, and viral loads but not with favipiravir therapy. There was no evidence of resistance development during favipiravir therapy.

Favipiravir: insight into the crystal structure, Hirshfeld surface analysis and computational study

In this work we report structural and computational studies of favipiravir, which is now used as a drug for COVID-19 treatment. The molecule is completely flat and stabilized by an intramolecular O–H···O hydrogen bond, yielding a six-membered pseudo-aromatic ring. The aromaticity index of this pseudo-aromatic ring was found to be 0.748, while the same indix for the pyrazine ring in favipiravir was found to be 0.954. The crystal packing of favipiravir is mainly constructed through intermolecular N–H···O, N–H···N and C–H···O hydrogen bonds, yielding a 3D supramolecular framework with a zst topology defined by the point symbol of (6⁵·8). The crystal structure of favipiravir is further stabilized by weak C–F···F–C intermolecular type II dihalogen interactions, yielding a 1D supramolecular polymeric chain. More than 80% of the total Hirshfeld surface area for favipiravir is occupied by H···H/C/N/O/F and C···N/O contacts. Energy frameworks have been calculated to additionally analyze the overall crystal packing. It was established that the structure of favipiravir is mainly characterized by the dispersion energy framework followed by the less significant electrostatic energy framework contribution. Finally, by using density functional theory (DFT) calculations and the quantum theory of atoms in molecules, we have assigned the interaction energy of each hydrogen bond, which can be helpful to develop scoring functions to be used in force fields/docking calculations.

A Multidisciplinary Approach to Coronavirus Disease (COVID-19)

Since December 2019, humanity has faced an important global threat. Many studies have been published on the origin, structure, and mechanism of action of the SARS-CoV-2 virus and the treatment of its disease. The priority of scientists all over the world has been to direct their time to research this subject. In this review, we highlight chemical studies and therapeutic approaches to overcome COVID-19 with seven different sections. These sections are the structure and mechanism of action of SARS-CoV-2, immunotherapy and vaccine, computer-aided drug design, repurposing therapeutics for COVID-19, synthesis of new molecular structures against COVID-19, food safety/security and functional food components, and potential natural products against COVID-19. In this work, we aimed to screen all the newly synthesized compounds, repurposing chemicals covering antiviral, anti-inflammatory, antibacterial, antiparasitic, anticancer, antipsychotic, and antihistamine compounds against COVID-19. We also highlight computer-aided approaches to develop an anti-COVID-19 molecule. We explain that some phytochemicals and dietary supplements have been identified as antiviral bioproducts, which have almost been successfully tested against COVID-19. In addition, we present immunotherapy types, targets, immunotherapy and inflammation/mutations of the virus, immune response, and vaccine issues.

The supramolecularly complexes of calix[4]arene derivatives toward favipiravir antiviral drug (used to treatment of COVID-19): a DFT study on the geometry optimization, electronic structure and infrared spectroscopy of adsorption and sensing

While the world is in search of a vaccine that can cure COVID-19 disease, favipiravir is the most commonly used antiviral drug in the treatment of patients during the pandemic process. In this study, we investigated the host-guest interaction between the popular supramolecule calix[4]arene derivatives and the favipiravir drug by using the DFT (Density Functional Theory) method. The B3LYP hybrid method and 6-31G (d,p) basis set were utilized to determine the optimized structures of the host and guest molecules and their complexes. The negative adsorption energy (∆E) and adsorption enthalpy (∆H) calculated for the complexes formed between calix[4]arene compounds and favipiravir drug molecule mentioned that adsorption of favipiravir molecule was an exothermic process on calix[4]arene structures. On the other hand, among the calixarene derivatives in the study, Gibbs free energy change (∆G) value for the adsorption was only negative on calix[4]arene4 molecule. The infrared spectroscopy (IR) calculations were performed by examining the C=O, O-H and NH2 vibrational frequencies to see the adsorption behavior in the favipiravir-calix[4]arene complex. After adsorption of the favipiravir molecule, HOMO-LUMO gap values decreased significantly for the structures and therefore electrical conductivity increased proportionally. In addition, sensor response factors, Fermi energy levels and workfunction changes of calix[4]arene derivatives were calculated and examined. Charge transfer between the four calix[4]arene compounds and the favipiravir molecule has occurred after adsorption. This attributes that calix[4]arene derivatives can be used as a well-suited favipiravir sensor (electronic and workfunction) and adsorbent at room temperature. Based on the calculations made to see the solvent effect on the adsorption of favipiravir it was determined that it did not affect the interaction between the drug molecule and the calix[4]arene compound too much and the adsorption energy turned into a slightly less negative value.

Remdesivir in Coronavirus Disease 2019 (COVID-19) treatment: a review of evidence

COVID-19 is an infectious disease caused by a novel β-coronavirus, belonging to the same subgenus as the Severe Acute Respiratory Syndrome (SARS) virus. Remdesivir, an investigational broad-spectrum antiviral agent has previously demonstrated in vitro activity against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and in vivo efficacy against other related coronaviruses in animal models. Its safety profile has been tested in a compassionate use setting for patients with COVID-19. The current therapeutic studies demonstrate clinical effectiveness of remdesivir in COVID-19 patients by shortening time to clinical recovery, and hospital stay. In this review, we critically analyze the current evidence of remdesivir against COVID-19 and dissect the aspects over its safety and efficacy. Based on existing data, remdesivir can be regarded as a potential therapeutic agent against COVID-19. Further large-scale, randomized placebo-controlled clinical trials are, however, awaited to validate these findings.

Cyanorona-20: The first potent anti-SARS-CoV-2 agent

Explicit hindrance and blockade of the viral RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 is considered one of the most promising and efficient approaches for developing highly potent remedies for COVID-19. However, almost all of the reported viral RdRp inhibitors (either repurposed or new antiviral drugs) lack specific selectivity against the novel coronaviral RdRp and still at a beginning phase of advancement. Herein, I discovered and introduce a new pyrazine derivative, (E)-N-(4-cyanobenzylidene)-6-fluoro-3-hydroxypyrazine-2-carboxamide (cyanorona-20), as the first potent SARS-CoV-2 RdRp inhibitor with very high selectivity (209- and 45-fold more potent than favipiravir and remdesivir, respectively). This promising selective specific anti-COVID-19 compound is also deemed to be the first distinctive derivative of favipiravir. Cyanorona-20, the unprecedented nucleoside/nucleotide analog, was designed, synthesized, characterized, computationally studied, and biologically evaluated for its anti-COVID-19 actions (through a precise in vitro anti-COVID-19 assay). The results of the biological assay displayed that cyanorona-20 surprisingly exhibited very high and largely significant anti-COVID-19 activities (anti-SARS-CoV-2 EC₅₀ = 0.45 μM), and, in addition, it could be also a very promising guide and lead compound for the design and synthesis of new anti-SARS-CoV-2 and anti-COVID-19 agents through structural modifications and further computational studies. Further appraisal for the improvement of cyanorona-20 medication is a prerequisite requirement in the coming days. In a word, the ascent of the second member (cyanorona-20 “Corona Antidote”) of the novel and promising class of anti-COVID-19 pyrazine derivatives would drastically make a medical uprising in the pharmacotherapeutic treatment regimens and protocols of the recently-emerged SARS-CoV-2 infection and its accompanying COVID-19.

Targeting COVID-19 in Parkinson's Patients: Drugs Repurposed

The last couple of months have witnessed the world in a state of virtual standstill. The SARS-CoV-2 virus has overtaken the globe to economic and social lockdown. Many patients with COVID-19 have compromised immunity, especially in an aged population suffering from Parkinson 's disease (PD). Alteration in dopaminergic neurons and deficiency of dopamine in PD patients are the most common symptoms affecting 1% population above the age of 60 years. The compromised immune system and inflammatory manifestation in PD patients make them an easy target. The most common drugs under trial for COVID-19 are remdesivir, favipiravir, chloroquine and hydroxychloroquine, azithromycin along with adjunct drugs like amantadine with some monoclonal antibodies. Presently, clinically US FDA approved drugs in PD include Levodopa, catechol-O-methyl transferase (COMT) inhibitors, (Entacapone and Tolcapone), dopamine agonists (Bromocriptine, Ropinirole, Pramipexole, and Rotigotine), monoamine oxidase B (MAO-B) inhibitors (Selegiline and Rasagiline), amantadine and antimuscarinic drugs. The drugs have established mechanisms of action on PD patients with known pharmacodynamics and pharmacokinetic properties along with dose and adverse effects. Conclusion and relevance of this review focus on the drugs that can be tried on PD patients with SAR CoV-2 infection, in particular, amantadine that has been approved by all the developed countries as a common drug possessing both antiviral properties by downregulation of CTSL, lysosomal pathway disturbance and change in pH necessary to uncoat the viral proteins and anti- Parkinson properties. To deal with the significant prognostic adverse effect of SARS-CoV-2 on PD, the present-day treatment options, clinical presentation and various mechanisms are the need of the hour.

Favipiravir for the treatment of patients with COVID-19: a systematic review and meta-analysis

BACKGROUND

Favipiravir possesses high utility for treating patients with COVID-19. However, research examining the efficacy and safety of favipiravir for patients with COVID-19 is limited.

METHODS

We conducted a systematic review of published studies reporting the efficacy of favipiravir against COVID-19. Two investigators independently searched PubMed, the Cochrane Database of Systematic Reviews, MedRxiv, and ClinicalTrials.gov (inception to September 2020) to identify eligible studies. A meta-analysis was performed to measure viral clearance and clinical improvement as the primary outcomes.

RESULTS

Among 11 eligible studies, 5 included a comparator group. Comparing to the comparator group, the favipiravir group exhibited significantly better viral clearance on day 7 after the initiation of treatment (odds ratio [OR] = 2.49, 95% confidence interval [CI] = 1.19-5.22), whereas no difference was noted on day 14 (OR = 2.19, 95% CI = 0.69-6.95). Although clinical improvement was significantly better in the favipiravir group on both days 7 and 14, the improvement was better on day 14 (OR = 3.03, 95% CI = 1.17-7.80) than on day 7 (OR = 1.60, 95% CI = 1.03-2.49). The estimated proportions of patients with viral clearance in the favipiravir arm on days 7 and 14 were 65.42 and 88.9%, respectively, versus 43.42 and 78.79%, respectively, in the comparator group. The estimated proportions of patients with clinical improvement on days 7 and 14 in the favipiravir group were 54.33 and 84.63%, respectively, compared with 34.40 and 65.77%, respectively, in the comparator group.

CONCLUSIONS

Favipiravir induces viral clearance by 7 days and contributes to clinical improvement within 14 days. The results indicated that favipiravir has strong possibility for treating COVID-19, especially in patients with mild-to-moderate illness. Additional well-designed studies, including examinations of the dose and duration of treatment, are crucial for reaching definitive conclusions.

Benefits of treatment with favipiravir in hospitalized patients for COVID-19: a retrospective observational case-control study

BACKGROUND

Although more than a year past since COVID-19 was defined, there is no specific treatment yet. Since COVID-19 management differs over time, it is hard to determine which therapy is more efficacious. In this study, we aimed to evaluate the efficacy of the regimen with Favipiravir (FPV) and determine if the timing of FPV addition offers any improvement.

METHODS

A retrospective observational case-controlled cohort study was performed between March and September 2020, including adults with COVID-19 in a single-center in Turkey. We categorized patients into age-sex matched three groups, group 1 (n = 48) and group 2 (n = 48) included patients treated with the combination of FPV plus Hydroxychloroquine (HQ) early and late, respectively. Group 3 (n = 48) consisted of patients on HQ monotherapy. In Group 2, if the respiratory or clinic condition had not improved sufficiently, FPV was added on or after day 3.

RESULTS

We found that starting FPV early had an impact on PCR negativity and the progression of the disease. 'No progression' was defined as the absence of a new finding in the control radiological examination and the absence of accompanying clinical deterioration. Also, the decrease in C-reactive protein (CRP) was greater in Group 1 than Group 3 (p < 0.001). However, we found that early initiation of FPV treatment did not have a positive effect on the estimated survival time.

CONCLUSIONS

According to this retrospective study results, we believe that for better clinical outcomes, FPV treatment should be started promptly to enhance antiviral effects and improve clinical outcomes.

Existing Drugs Considered as Promising in COVID-19 Therapy

COVID-19 is a respiratory disease caused by newly discovered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease at first was identified in the city of Wuhan, China in December 2019. Being a human infectious disease, it causes high fever, cough, breathing problems. In some cases it can be fatal, especially in people with comorbidities like heart or kidney problems and diabetes. The current COVID-19 treatment is based on symptomatic therapy, so finding an appropriate drug against COVID-19 remains an immediate and crucial target for the global scientific community. Two main processes are thought to be responsible for the COVID-19 pathogenesis. In the early stages of infection, disease is determined mainly by virus replication. In the later stages of infection, by an excessive immune/inflammatory response, leading to tissue damage. Therefore, the main treatment options are antiviral and immunomodulatory/anti-inflammatory agents. Many clinical trials have been conducted concerning the use of various drugs in COVID-19 therapy, and many are still ongoing. The majority of trials examine drug reposition (repurposing), which seems to be a good and effective option. Many drugs have been repurposed in COVID-19 therapy including remdesivir, favipiravir, tocilizumab and baricitinib. The aim of this review is to highlight (based on existing and accessible clinical evidence on ongoing trials) the current and available promising drugs for COVID-19 and outline their characteristics.

Marine algal antagonists targeting 3CL protease and spike glycoprotein of SARS-CoV-2: a computational approach for anti-COVID-19 drug discovery

The COVID-19 pandemic has severely destructed human life worldwide, with no suitable treatment until now. SARS-CoV-2 virus is unprecedented, resistance against number of therapeutics and spreading rapidly with high mortality, which warrants the need to discover new effective drugs to combat this situation. This current study is undertaken to explore the antiviral potential of marine algal compounds to inhibit the viral entry and its multiplication using computational analysis. Among the proven drug discovery targets of SARS-CoV-2, spike glycoprotein and 3-chymotrypsin-like protease are responsible for the virus attachment and viral genome replication in the host cell. In this study, the above-mentioned drug targets were docked with marine algal compounds (sulfated polysaccharides, polysaccharide derivatives and polyphenols) using molecular docking tools (AutoDockTools). The obtained results indicate that κ-carrageenan, laminarin, eckol, trifucol and β-D-galactose are the top-ranking compounds showing better docking scores with SARS-CoV-2 targets, than the current experimental COVID-19 antiviral drugs like dexamethasone, remdesivir, favipiravir and MIV-150. Further, molecular dynamic simulation, ADMET and density functional theory calculations were evaluated to substantiate the findings. To the best of our knowledge, this is the first report on in silico analysis of aforesaid algal metabolites against SARS-CoV-2 targets. This study concludes that these metabolites can be curative for COVID-19 in the hour of need after further validations in in vitro and in vivo testings.Communicated by Ramaswamy H. Sarma.

Discovery of (E)-N-(4-cyanobenzylidene)- 6-fluoro- 3-hydroxypyrazine-2 -carboxamide (cyanorona-20): the first potent and specific anti-COVID-19 drug

Abstract

Specific inhibition of the viral RNA-dependent RNA polymerase (RdRp) of the newly-emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a very promising strategy for developing highly potent medicines for coronavirus disease 2019 (COVID-19). However, almost all of the reported viral RdRp inhibitors (either repurposed drugs or new antiviral agents) lack selectivity against the SARS-CoV-2 RdRp. Herein, I discovered a new favipiravir derivative, (E)-N-(4-cyanobenzylidene)-6-fluoro-3-hydroxypyrazine-2-carboxamide (cyanorona-20), as the first potent SARS-CoV-2 inhibitor with very high selectivity (209- and 45-fold more potent than favipiravir and remdesivir, respectively). Based on the significant reduction in the in vitro SARS-CoV-2 replication/copies, strong computational cyanorona-20 ligand-RdRp protein interactions, and anti-RdRp activity of the parent favipiravir drug, SARS-CoV-2 inhibition is thought to be mediated through the coronaviral-2 RdRp inhibition. This promising selective anti-COVID-19 compound is also, to the best of our knowledge, the first bioactive derivative of favipiravir, the known antiinfluenza and antiviral drug. This new nucleoside analog was designed, synthesized, characterized, computationally studied (through pharmacokinetic calculations along with computational molecular modeling and prediction), and biologically evaluated for its anti-COVID-19 activities (through a validated in vitro anti-COVID-19 assay). The results of the biological assay showed that cyanorona-20 surprisingly exhibited very significant anti-COVID-19 activity (anti-SARS-CoV-2 EC₅₀ = 0.45 μM), and, in addition, it could be also a very promising lead compound for the design of new anti-COVID-19 agents. Cyanorona-20 is a new favipiravir derivative with promise for the treatment of SARS-CoV-2 infection.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-021-01640-9.

Therapeutic Development in COVID-19

Since the outbreak of coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2, the disease has spread rapidly worldwide and developed into a global pandemic, causing a significant impact on the global health system and economic development. Scientists have been racing to find effective drugs and vaccines for the treatment and prevention of COVID-19. However, due to the diversity of clinical manifestations caused by COVID-19, no standard antiviral regimen beyond supportive therapy has been established. Ongoing clinical trials are underway to evaluate the efficacy of drugs that primarily act on the viral replication cycle or enhanced immunity of patients. This chapter will summarize the currently used antiviral and adjuvant therapies in clinical practice and provide a theoretical basis for the future treatment of COVID-19.

Methods of Synthesis and Antiviral Activity of New 4-Alkyl-3-Nitro-1,4-Dihydroazolo[5,1-c][1,2,4]Triazin-4-ols

An azo coupling reaction of α-nitro ketones with 5-diazoazoles was used to obtain 4-alkyl-3-nitro-1,4-dihydroazolo[5,1-с][1,2,4]triazines, which were characterized with respect to their antiviral activity against influenza and Coxsackie B3 viruses.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10593-021-02926-2.

Favipiravir: the hidden threat of mutagenic action

 

The antiviral drug favipiravir (FVP), which is a structural analogue of guanosine, undergoes chemical transformation in infected cells by cellular enzymes into a nucleotide form — favipiravir ribose triphosphate (FVPRTP). FVP-RTP is able to bind to viral RNA-dependent RNA polymerase and integrate into the viral RNA chain, causing a significant mutagenic effect through G→A and С→U transitions in the viral RNA genome. Besides the virus inhibiting effect, the increased synthesis of mutant virions under the action of FPV possess a threat of the emergence of novel threatening viral strains with high pathogenicity for humans and animals and acquired resistance to chemotherapeutic compound. There are three ways to minimize this mutagenic effect of FP. (1) Synthesis of new FPV modifications lacking the ability to integrate into the synthesized viral RNA molecule. (2) The combined use of FPV with antiviral chemotherapeutic drugs of a different mechanism of action directed at various viral and/or host cell targets. (3) Permanent application of high therapeutic doses of FPV under the strict medical control to enhance the lethal mutagenic effect on an infectious virus in the recipient organism to prevent the multiplication of its mutant forms.

Drug repurposing approach to combating coronavirus: Potential drugs and drug targets

In the past two decades, three highly pathogenic human coronaviruses severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus, and, recently, SARS-CoV-2, have caused pandemics of severe acute respiratory diseases with alarming morbidity and mortality. Due to the lack of specific anti-CoV therapies, the ongoing pandemic of coronavirus disease 2019 (COVID-19) poses a great challenge to clinical management and highlights an urgent need for effective interventions. Drug repurposing is a rapid and feasible strategy to identify effective drugs for combating this deadly infection. In this review, we summarize the therapeutic CoV targets, focus on the existing small molecule drugs that have the potential to be repurposed for existing and emerging CoV infections of the future, and discuss the clinical progress of developing small molecule drugs for COVID-19.

Favipiravir biotransformation in liver cytosol: Species and sex differences in humans, monkeys, rats, and mice

Favipiravir is an antiviral agent effective against several RNA viruses that is converted into an inactive oxidative metabolite (M1), mainly by aldehyde oxidase, in humans. In the present study, the biotransformation of favipiravir into M1 in male and female humans, monkeys, rats, and mice was examined in an in vitro system using liver cytosolic fractions. The kinetics for M1 formation followed the Michaelis-Menten model in all species. The Km , Vmax , and CLint values in humans were 602 µM, 466 pmol/min/mg protein, and 776 nl/min/mg protein in males, respectively, and 713 µM, 404 pmol/min/mg protein, and 567 nl/min/mg protein in females, respectively. Species differences in CLint values were monkeys > humans > mice > rats in both males and females, and the variations for males and females were 120- and 96-fold, respectively. Sex differences in CLint values were males > females in humans and mice, females > males in monkeys and rats, and marked variation (4.3-fold) was noted in mice. This suggests that the roles of aldehyde oxidase in the hepatic metabolism of favipiravir differ extensively depending on the species and sex, and this study will aid in the assessment of the antiviral activities of favipiravir against novel and/or variant viruses.

Disease-drug and drug-drug interaction in COVID-19: Risk and assessment

COVID-19 is announced as a global pandemic in 2020. Its mortality and morbidity rate are rapidly increasing, with limited medications. The emergent outbreak of COVID-19 prompted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) keeps spreading. In this infection, a patient's immune response plays pivotal role in the pathogenesis. This inflammatory factor was shown by its mediators that, in severe cases, reach the cytokine at peaks. Hyperinflammatory state may sparks significant imbalances in transporters and drug metabolic machinery, and subsequent alteration of drug pharmacokinetics may result in unexpected therapeutic response. The present scenario has accounted for the requirement for therapeutic opportunities to relive and overcome this pandemic. Despite the diminishing developments of COVID-19, there is no drug still approved to have significant effects with no side effect on the treatment for COVID-19 patients. Based on the evidence, many antiviral and anti-inflammatory drugs have been authorized by the Food and Drug Administration (FDA) to treat the COVID-19 patients even though not knowing the possible drug-drug interactions (DDI). Remdesivir, favipiravir, and molnupiravir are deemed the most hopeful antiviral agents by improving infected patient’s health. Dexamethasone is the first known steroid medicine that saved the lives of seriously ill patients. Some oligopeptides and proteins have also been using. The current review summarizes medication updates to treat COVID-19 patients in an inflammatory state and their interaction with drug transporters and drug-metabolizing enzymes. It gives an opinion on the potential DDI that may permit the individualization of these drugs, thereby enhancing the safety and efficacy.

Targeting Ebola virus replication through pharmaceutical intervention

Introduction. The consistent emergence/reemergence of filoviruses into a world that previously lacked an approved pharmaceutical intervention parallels an experience repeatedly played-out for most other emerging pathogenic zoonotic viruses. Investment to preemptively develop effective and low-cost prophylactic and therapeutic interventions against viruses that have high potential for emergence and societal impact should be a priority.Areas covered. Candidate drugs can be characterized into those that interfere with cellular processes required for Ebola virus (EBOV) replication (host-directed), and those that directly target virally encoded functions (direct-acting). We discuss strategies to identify pharmaceutical interventions for EBOV infections. PubMed/Web of Science databases were searched to establish a detailed catalog of these interventions.Expert opinion. Many drug candidates show promising in vitro inhibitory activity, but experience with EBOV shows the general lack of translation to in vivo efficacy for host-directed repurposed drugs. Better translation is seen for direct-acting antivirals, in particular monoclonal antibodies. The FDA-approved monoclonal antibody treatment, Inmazeb™ is a success story that could be improved in terms of impact on EBOV-associated disease and mortality, possibly by combination with other direct-acting agents targeting distinct aspects of the viral replication cycle. Costs need to be addressed given EBOV emergence primarily in under-resourced countries.

Early favipiravir treatment was associated with early defervescence in non-severe COVID-19 patients

Introduction

The antiviral drug favipiravir has been shown to have in vitro antiviral activity against severe-acute-respiratory-syndrome-coronavirus-2 (SARS-CoV-2). In this study, we investigated the clinical benefits and initiation of favipiravir treatment in patients with non-severe coronavirus-disease-2019 (COVID-19).

Methods

This study was a single-center retrospective cohort study. Receiver operating characteristic curves were drawn to calculate the area under the curve, and the optimal cut-off values for the time to initiate favipiravir treatment were calculated to predict defervescence within seven days. Univariate and multivariate Cox regression analyses were performed to identify potential influencing factors of defervescence. This was defined as a body temperature of less than 37 °C for at least 2 days.

Results

Data from 41 patients were used for the efficacy assessment. The days from the onset of fever to defervescence showed a positive correlation with the duration from the onset of fever to initiation of favipiravir treatment (r = 0.548, P < 0.001). The optimal cut-off value was the administration of favipiravir on day 4. Patients were assigned to two groups based on the optimal cut-off value from onset to initiation of favipiravir treatment: early treatment group (within 4-days) and late treatment group (more than 4-days). In the multivariate analysis, when adjusted for age, sex, and days from onset to initiation of favipiravir treatment, the significant factors were male sex and days of initiation of the favipiravir treatment.

Conclusions

We recommend that if favipiravir is to be used for treatment, it should be initiated as early as possible.

Multicentre randomised double-blinded placebo-controlled trial of favipiravir in adults with mild COVID-19

INTRODUCTION

A novel coronavirus, designated SARS-CoV-2, caused an international outbreak of a respiratory illness, termed COVID-19 in December 2019. There is a lack of specific therapeutic agents based on evidence for this novel coronavirus infection; however, several medications have been evaluated as a potential therapy. Therapy is required to treat symptomatic patients and decrease the virus carriage duration to limit the communitytransmission.

METHODS AND ANALYSIS

We hypothesise that patients with mild COVID-19 treated with favipiravir will have a shorter duration of time to virus clearance than the control group. The primary outcome is to evaluate the effect of favipiravir on the timing of the PCR test conversion from positive to negative within 15 days after starting the medicine.Adults (>18 years, men or nonpregnant women, diagnosed with mild COVID-19 within 5 days of disease onset) are being recruited by physicians participating from the Ministry of National Guard Health Affairs and the Ministry of Health ethics committee approved primary healthcare centres. This double-blind, randomised trial comprises three significant parts: screening, treatment and a follow-up period. The treating physician and patients are blinded. Eligible participants are randomised in a 1:1 ratio to either the therapy group (favipiravir) or a control group (placebo) with 1800 mg by mouth two times per day for the first day, followed by 800 mg two times per day for 4-7 days. Serial nasopharyngeal/oropharyngeal swab samples are obtained on day 1 (5 days before therapy). On day5±1 day, 10±1 day, 15±2 days, extra nasopharyngeal/oropharyngeal PCR COVID-19 samples are requested.The primary analysis population for evaluating both the efficacy and safety outcomes will be a modified intention to treat population. Anticipating a 10% dropout rate, we expect to recruit 288 subjects per arm. The results assume that the hazard ratio is constant throughout the study and that the Cox proportional hazard regression is used to analyse the data.

ETHICS AND DISSEMINATION

The study was approved by the King Abdullah International Medical Research Centre Institutional Review Board (28 April 2020) and the Ministry of Health Institutional Review Board (1 July 2020). Protocol details and any amendments will be reported to https://clinicaltrials.gov/ct2/show/NCT04464408. The results will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

National Clinical Trial Registry (NCT04464408).

Lassa Virus Treatment Options

Lassa fever causes an approximate 5000 to 10,000 deaths annually in West Africa and cases have been imported into Europe and the Americas, challenging public health. Although Lassa virus was first described over 5 decades ago in 1969, no treatments or vaccines have been approved to treat or prevent infection. In this review, we discuss current therapeutics in the development pipeline for the treatment of Lassa fever, focusing on those that have been evaluated in humans or animal models. Several treatments, including the antiviral favipiravir and a human monoclonal antibody cocktail, have shown efficacy in preclinical rodent and non-human primate animal models and have potential for use in clinical settings. Movement of the promising preclinical treatment options for Lassa fever into clinical trials is critical to continue addressing this neglected tropical disease.

iPSC screening for drug repurposing identifies anti-RNA virus agents modulating host cell susceptibility

Human pathogenic RNA viruses are threats to public health because they are prone to escaping the human immune system through mutations of genomic RNA, thereby causing local outbreaks and global pandemics of emerging or re-emerging viral diseases. While specific therapeutics and vaccines are being developed, a broad-spectrum therapeutic agent for RNA viruses would be beneficial for targeting newly emerging and mutated RNA viruses. In this study, we conducted a screen of repurposed drugs using Sendai virus (an RNA virus of the family Paramyxoviridae), with human-induced pluripotent stem cells (iPSCs) to explore existing drugs that may present anti-RNA viral activity. Selected hit compounds were evaluated for their efficacy against two important human pathogens: Ebola virus (EBOV) using Huh7 cells and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using Vero E6 cells. Selective estrogen receptor modulators (SERMs), including raloxifene, exhibited antiviral activities against EBOV and SARS-CoV-2. Pioglitazone, a PPARγ agonist, also exhibited antiviral activities against SARS-CoV-2, and both raloxifene and pioglitazone presented a synergistic antiviral effect. Finally, we demonstrated that SERMs blocked entry steps of SARS-CoV-2 into host cells. These findings suggest that the identified FDA-approved drugs can modulate host cell susceptibility against RNA viruses.

Potential COVID-19 Therapeutic Agents and Vaccines: An Evidence-Based Review

Since the early days of 2020, the severe acute respiratory syndrome coronavirus 2 pandemic has become a global health concern. Currently, some therapies and vaccines have received US Food and Drug Administration approval or emergency use authorization for the management of coronavirus disease 2019. According to the pathophysiology of the disease, several medications have been evaluated in different clinical conditions of the disease. Evidence-based reviewing and categorizing these medications can guide the clinicians to select the proper medications according to each patient's condition. Therefore, we performed this review to categorize the coronavirus disease 2019 potential therapeutics and vaccines.

COVID-19: Antiviral agents and enzyme inhibitors/receptor blockers in development

Novel 2019 coronavirus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) and coronavirus disease 2019 (COVID-19), the respiratory syndrome it causes, have shaken the world to its core by infecting and claiming the lives of many people since originating in December 2019 in Wuhan, China. World Health Organization and several states have declared a pandemic situation and state of emergency, respectively. As there is no treatment for COVID-19, several research institutes and pharmaceutical companies are racing to find a cure. Advances in computational approaches have allowed the screening of massive antiviral compound libraries to identify those that may potentially work against SARS-CoV-2. Antiviral agents developed in the past to combat other viruses are being repurposed. At the same time, new vaccine candidates are being developed and tested in preclinical/clinical settings. This review provides a detailed overview of select repurposed drugs, their mechanism of action, associated toxicities, and major clinical trials involving these agents.

Tackling COVID-19 Using Remdesivir and Favipiravir as Therapeutic Options

The human world is currently influenced largely by the outbreak of pandemic COVID-19. At this moment, most researchers focus on developing treatment strategies and measures to work against COVID-19. Treatment strategies specific for COVID-19 are lacking. This article provides an overview of the life cycle and routes of transmission of SARS-CoV-2. The therapeutic effects of two drugs [i. e., remdesivir (RDV) and favipiravir (FPV)] which can potentially tackle COVID-19 are discussed based on current published data. This review can serve as a reference for future studies.

COVID-19 preparedness: capacity to manufacture vaccines, therapeutics and diagnostics in sub-Saharan Africa

OBJECTIVE

The COVID-19 pandemic is a biosecurity threat, and many resource-rich countries are stockpiling and/or making plans to secure supplies of vaccine, therapeutics, and diagnostics for their citizens. We review the products that are being investigated for the prevention, diagnosis, and treatment of COVID-19; discuss the challenges that countries in sub-Saharan Africa may face with access to COVID-19 vaccine, therapeutics, and diagnostics due to the limited capacity to manufacture them in Africa; and make recommendations on actions to mitigate these challenges and ensure health security in sub-Saharan Africa during this unprecedented pandemic and future public-health crises.

MAIN BODY

Sub-Saharan Africa will not be self-reliant for COVID-19 vaccines when they are developed. It can, however, take advantage of existing initiatives aimed at supporting COVID-19 vaccine access to resource-limited settings such as partnership with AstraZeneca, the Coalition for Epidemic Preparedness and Innovation, the Global Alliance for Vaccine and Immunisation, the Serum Institute of India, and the World Health Organization's COVID-19 Technology Access Pool. Accessing effective COVID-19 therapeutics will also be a major challenge for countries in sub-Saharan Africa, as production of therapeutics is frequently geared towards profitable Western markets and is ill-adapted to sub-Saharan Africa realities. The region can benefit from pooled procurement of COVID-19 therapy by the Africa Centres for Disease Control and Prevention in partnership with the African Union. If the use of convalescent plasma for the treatment of patients who are severely ill is found to be effective, access to the product will be minimally challenging since the region has a pool of recovered patients and human resources that can man supportive laboratories. The region also needs to drive the local development of rapid-test kits and other diagnostics for COVID-19.

CONCLUSION

Access to vaccines, therapeutics, and diagnostics for COVID-19 will be a challenge for sub-Saharan Africans. This challenge should be confronted by collaborating with vaccine developers; pooled procurement of COVID-19 therapeutics; and local development of testing and diagnostic materials. The COVID-19 pandemic should be a wake-up call for sub-Saharan Africa to build vaccines, therapeutics, and diagnostics manufacturing capacity as one of the resources needed to address public-health crises.

Favipiravir and COVID-19: A Simplified Summary

A recent outbreak of coronavirus disease 2019 (COVID-19) caused by the novel coronavirus designated as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) started in Wuhan, China, at the end of 2019 and then spread rapidly all over the world. However, there are no specific antiviral therapies for COVID-19, using the agents which approved or in development for other viral infections is one of the potentially quickest ways to find treatment for this new viral infection. Favipiravir is an effective agent that acts as a nucleotide analog that selectively inhibits the viral RNA dependent RNA polymerase or causes lethal mutagenesis upon incorporation into the virus RNA. In view of recent studies and discussion on favipiravir, in this mini review we aimed to summarize the clinical trials studying the efficacy and safety of favipiravir in patients with COVID-19.

Revised Korean Society of Infectious Diseases/National Evidence-based Healthcarea Collaborating Agency Guidelines on the Treatment of Patients with COVID-19

Despite the global effort to mitigate the spread, coronavirus disease 2019 (COVID-19) has become a pandemic that took more than 2 million lives. There are numerous ongoing clinical studies aiming to find treatment options and many are being published daily. Some effective treatment options, albeit of variable efficacy, have been discovered. Therefore, it is necessary to develop an evidence-based methodology, to continuously check for new evidence, and to update recommendations accordingly. Here we provide guidelines on pharmaceutical treatment for COVID-19 based on the latest evidence.

Virtual Screening and Molecular Design of Potential SARS-COV-2 Inhibitors

According to recent studies, the main M^pro protease of the SARS-CoV-2 virus, which is the most important target in the development of promising drugs for the treatment of COVID-19, is evolutionarily conservative and has not undergone significant changes compared with the main M^pro protease of the SARS-CoV virus. Many researchers note the similarity between the binding sites of the main M^pro protease of SARS-CoV and SARS-CoV-2 viruses; thus, with the spreading epidemic, further studies on inhibitors of the main M^pro protease of the SARS-CoV virus to fight COVID-19 seems logical. In the course of the study, satisfactory QSAR models are built using simplex, fractal, and HYBOT descriptors; the Partial Least Squares (PLS), Random Forest (RF), Support Vectors, Gradient Boosting (GBM) methods; and the OCHEM Internet platform (https://ochem.eu), in which different types of molecular descriptors and machine learning methods are implemented. The structural interpretation, which allowed us to identify molecular fragments that increase and decrease the activity of SARS-CoV inhibitors, is performed for the obtained models. The results of the structural interpretation are used for the rational molecular design of potential SARS-CoV-2 inhibitors. The resulting QSAR models are used for the virtual screening of 2087 FDA-approved drugs.

The find of COVID-19 vaccine: Challenges and opportunities

Severe acute respiratory syndrome coronavirus (SARS-CoV-2), a novel corona virus, causing COVID-19 with Flu-like symptoms is the first alarming pandemic of the third millennium. SARS-CoV-2 belongs to beta coronavirus as Middle East respiratory syndrome coronavirus (MERS-CoV). Pandemic COVID-19 owes devastating mortality and destructively exceptional consequences on Socio-Economics life around the world. Therefore, the current review is redirected to the scientific community to owe comprehensive visualization about SARS-CoV-2 to tackle the current pandemic. As systematically shown through the current review, it indexes unmet medical problem of COVID-19 in view of public health and vaccination discovery for the infectious SARS-CoV-2; it is currently under-investigational therapeutic protocols, and next possible vaccines. Furthermore, the review extensively reports the precautionary measures to achieve" COVID-19/Flatten the curve". It is concluded that vaccines formulation within exceptional no time in this pandemic is highly recommended, via following the same protocols of previous pandemics; MERS-CoV and SARS-CoV, and excluding some initial steps of vaccination development process.

Respiratory delivery of favipiravir-tocilizumab combination through mucoadhesive protein-lipidic nanovesicles: prospective therapeutics against COVID-19

Coronavirus disease 19 (COVID-19) is the prime global health concern of the year 2020. Infecting more than 112 million individuals so far, this pandemic has already reported more than 2.4 million deaths around the world. With such high infectivity and mortality, effective treatment intervention is the need of the hour. The integration of medical science with nanotechnology may solve the current problem by exploring collective benefits. In this manuscript, we theoretically proposed the duo-combination of an approved antiviral i.e. favipiravir along with an immunomodulator i.e. tocilizumab loaded in protein-lipid nanovesicles as an effective anti-COVID-19 therapeutic. This proposed nanomedicine delivered through the respiratory mode may enhance the effectiveness of the antiviral and help in restricting the virus and associated complications, utilizing both anti-viral activity and immunomodulation in COVID-19 patients. This proposed nanomedicine could be an effective treatment modality for the severe acute respiratory syndrome- coronavirus-2 (SARS-CoV-2) infected patients.

COVID-19 first anniversary review of cases, hospitalization, and mortality in the UK

Introduction: The first confirmed COVID-19 case in UK dates to 11 January 2020, exhibiting its first peak during April 2020. The country has since been hit by another wave in the winter 2020, almost at the first anniversary of the pandemic.Areas covered: An in-depth analysis of the COVID-19 positive cases in the UK throughout the year, hospitalizations, patients in critical care, and COVID-19 associated deaths.Expert opinion: The COVID-19 associated hospital admission accounts to 15% of total COVID-19 positive cases in November 2020. The percentage of total COVID-19 positive patients in the country died from the disease was under 4% in November 2020. Total deaths in England (all-cause) from June to October 2020 were similar to the historic averages. Age was the single most determinator of COVID-19 associated mortality, 50 years or older accounted for 98% of total COVID deaths. Age distribution of COVID-19 associated deaths in 2020 was similar to all-cause mortality age distribution in 2019. There was no significant improvement in the survival rate of COVID-19 patients receiving critical care. This prompts an urgent need to invest in novel antiviral therapeutics to save the most vulnerable in the society.

A Scoping Insight on Potential Prophylactics, Vaccines and Therapeutic Weaponry for the Ongoing Novel Coronavirus (COVID-19) Pandemic- A Comprehensive Review

The emergence of highly virulent CoVs (SARS-CoV-2), the etiologic agent of novel ongoing "COVID-19" pandemics has been marked as an alarming case of pneumonia posing a large global healthcare crisis of unprecedented magnitude. Currently, the COVID-19 outbreak has fueled an international demand in the biomedical field for the mitigation of the fast-spreading illness, all through the urgent deployment of safe, effective, and rational therapeutic strategies along with epidemiological control. Confronted with such contagious respiratory distress, the global population has taken significant steps towards a more robust strategy of containment and quarantine to halt the total number of positive cases but such a strategy can only delay the spread. A substantial number of potential vaccine candidates are undergoing multiple clinical trials to combat COVID-19 disease, includes live-attenuated, inactivated, viral-vectored based, sub-unit vaccines, DNA, mRNA, peptide, adjuvant, plant, and nanoparticle-based vaccines. However, there are no licensed anti-COVID-19 drugs/therapies or vaccines that have proven to work as more effective therapeutic candidates in open-label clinical trial studies. To counteract the infection (SARS-CoV-2), many people are under prolonged treatment of many chemical drugs that inhibit the PLpro activity (Ribavirin), viral proteases (Lopinavir/Ritonavir), RdRp activity (Favipiravir, Remdesivir), viral membrane fusion (Umifenovir, Chloroquine phosphate (CQ), Hydroxychloroquine phosphate (HCQ), IL-6 overexpression (Tocilizumab, Siltuximab, Sarilumab). Mesenchymal Stem Cell therapy and Convalescent Plasma Therapy have emerged as a promising therapeutic strategy against SARS-CoV-2 virion. On the other hand, repurposing previously designed antiviral agents with tolerable safety profile and efficacy could be the only promising approach and fast response to the novel virion. In addition, research institutions and corporations have commenced the redesign of the available therapeutic strategy to manage the global crisis. Herein, we present succinct information on selected anti-COVID-19 therapeutic medications repurposed to combat SARS-CoV-2 infection. Finally, this review will provide exhaustive detail on recent prophylactic strategies and ongoing clinical trials to curb this deadly pandemic, outlining the major therapeutic areas for researchers to step in.

Role of the SphK-S1P-S1PRs pathway in invasion of the nervous system by SARS-CoV-2 infection

Global spread of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is still ongoing. Before an effective vaccine is available, the development of potential treatments for resultant coronavirus disease 2019 (COVID‐19) is crucial. One of the disease hallmarks is hyper‐inflammatory responses, which usually leads to a severe lung disease. Patients with COVID‐19 also frequently suffer from neurological symptoms such as acute diffuse encephalomyelitis, brain injury and psychiatric complications. The metabolic pathway of sphingosine‐1‐phosphate (S1P) is a dynamic regulator of various cell types and disease processes, including the nervous system. It has been demonstrated that S1P and its metabolic enzymes, regulating neuroinflammation and neurogenesis, exhibit important functions during viral infection. S1P receptor 1 (S1PR1) analogues including AAL‐R and RP‐002 inhibit pathophysiological responses at the early stage of H1N1 virus infection and then play a protective role. Fingolimod (FTY720) is an S1P receptor modulator and is being tested for treating COVID‐19. Our review provides an overview of SARS‐CoV‐2 infection and critical role of the SphK‐S1P‐SIPR pathway in invasion of SARS‐CoV‐2 infection, particularly in the central nervous system (CNS). This may help design therapeutic strategies based on the S1P‐mediated signal transduction, and the adjuvant therapeutic effects of S1P analogues to limit or prevent the interaction between the host and SARS‐CoV‐2, block the spread of the SARS‐CoV‐2, and consequently treat related complications in the CNS.

A novel, rapid and simple UPLC-MS/MS method for quantification of favipiravir in human plasma: Application to a bioequivalence study

A novel, simple and rapid UPLC-MS/MS method was developed and validated for determination of favipiravir (FAV) in human plasma. Lamivudine was used as an internal standard (IS). The Xevo TQD LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. Precipitation with acetonitrile was used in sample preparation as it gives relatively cleaner plasma samples. The prepared samples were chromatographed using an Acquity UPLC^® HSS C₁₈ (100 × 2.1 mm, 1.8 μm) column. The mobile phase was composed of ammonium formate and methanol in a gradient mode that was pumped at a flow rate of 0.35 ml/min. The developed method was validated as per the FDA guidelines and linearity was in the range of 0.25-16 μg/ml for FAV. The intra- and inter-day precision and accuracy results were within the acceptable limits. A run time of 4.5 min and a low quantification limit of FAV allowed the application of the developed method for the determination of FAV in a bioequivalence study in healthy human volunteers.

Tocilizumab, Remdesivir, Favipiravir, and Dexamethasone Repurposed for COVID-19: a Comprehensive Clinical and Pharmacovigilant Reassessment

In this manuscript, we discuss the expectations versus the real-world results of four repurposed COVID-19 drugs: tocilizumab, remdesivir, favipiravir, and dexamethasone from a clinical and pharmacovigilant point of view. We suggest that though the results of two-phase III double-blind clinical trials have been less than expected, tocilizumab has a real remaining potential to treat selected critical cases of COVID-19 beyond clinical trials until more data are revealed. On the contrary, remdesivir, though its FDA approval, and favipiravir are least likely to benefit COVID-19 patients. Moreover, we recommend that the RECOVERY dexamethasone should only be considered for critical hospitalized COVID-19 patients and we urge physicians in developing countries to avoid using it in mild-moderate COVID-19 cases. Finally, we recommend considering a personalized risk-benefit ratio before a decision is made using any of these drugs.

Indoor versus outdoor transmission of SARS-COV-2: environmental factors in virus spread and underestimated sources of risk

The first case of Coronavirus Disease 2019 (COVID-19), which is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), in Europe was officially confirmed in February 2020. On 11 March 2020, after thousands of deaths from this disease had been reported worldwide, the WHO changed their classification of COVID-19 from a public health emergency of international concern to a pandemic. The SARS-CoV-2 virus has been shown to be much more resistant to environmental degradation than other coated viruses. Several studies have shown that environmental conditions can influence its viability and infectivity. This review summarizes current knowledge on the transmission pathways of the novel coronavirus, and directs attention towards potentially underestimated factors that affect its propagation, notably indoor spread and outdoor risk sources. The contributions of significant indoor factors such as ventilation systems to the spread of this virus need to be carefully ascertained. Outdoor risk sources such as aerosolized particles emitted during wastewater treatment and particulate matter (PM), both of which may act as virus carriers, should be examined as well. This study shows the influence of certain underestimated factors on the environmental behavior and survival of the SARS-CoV-2 virus. These aspects of coronavirus propagation need to be accounted for when devising actions to limit not only the current pandemic but also future outbreaks.

Development of a highly sensitive bioanalytical assay for the quantification of favipiravir

Favipiravir (FAV; T-705) has been approved for use as an anti-influenza therapeutic and has reports against a wide range of viruses (e.g., Ebola virus, rabies and norovirus). Most recently FAV has been reported to demonstrate activity against SARS-CoV-2. Repurposing opportunities have been intensively studied with only limited success to date. If successful, repurposing will allow interventions to become more rapidly available than development of new chemical entities. Pre-clinical and clinical investigations of FAV require robust, reproducible and sensitive bioanalytical assay. Here, a liquid chromatography tandem mass spectrometry assay is presented which was linear from 0.78-200 ng/mL Accuracy and precision ranged between 89% and 110%, 101% and 106%, respectively. The presented assay here has applications in both pre-clinical and clinical research and may be used to facilitate further investigations into the application of FAV against SARS-CoV-2.

Development and Effects of Influenza Antiviral Drugs

Influenza virus is a highly contagious zoonotic respiratory disease that causes seasonal outbreaks each year and unpredictable pandemics occasionally with high morbidity and mortality rates, posing a great threat to public health worldwide. Besides the limited effect of vaccines, the problem is exacerbated by the lack of drugs with strong antiviral activity against all flu strains. Currently, there are two classes of antiviral drugs available that are chemosynthetic and approved against influenza A virus for prophylactic and therapeutic treatment, but the appearance of drug-resistant virus strains is a serious issue that strikes at the core of influenza control. There is therefore an urgent need to develop new antiviral drugs. Many reports have shown that the development of novel bioactive plant extracts and microbial extracts has significant advantages in influenza treatment. This paper comprehensively reviews the development and effects of chemosynthetic drugs, plant extracts, and microbial extracts with influenza antiviral activity, hoping to provide some references for novel antiviral drug design and promising alternative candidates for further anti-influenza drug development.