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

Revealing the structural and molecular interaction landscape of the favipiravir-RTP and SARS-CoV-2 RdRp complex through integrative bioinformatics: Insights for developing potent drugs targeting SARS-CoV-2 and other viruses

BACKGROUND

The global research community has made considerable progress in therapeutic and vaccine research during the COVID-19 pandemic. Several therapeutics have been repurposed for the treatment of COVID-19. One such compound is, favipiravir, which was approved for the treatment of influenza viruses, including drug-resistant influenza. Despite the limited information on its molecular activity, clinical trials have attempted to determine the effectiveness of favipiravir in patients with mild to moderate COVID-19. Here, we report the structural and molecular interaction landscape of the macromolecular complex of favipiravir-RTP and SARS-CoV-2 RdRp with the RNA chain.

METHODS

Integrative bioinformatics was used to reveal the structural and molecular interaction landscapes of two macromolecular complexes retrieved from RCSB PDB.

RESULTS

We analyzed the interactive residues, H-bonds, and interaction interfaces to evaluate the structural and molecular interaction landscapes of the two macromolecular complexes. We found seven and six H-bonds in the first and second interaction landscapes, respectively. The maximum bond length is 3.79 Å. In the hydrophobic interactions, five residues (Asp618, Asp760, Thr687, Asp623, and Val557) were associated with the first complex and two residues (Lys73 and Tyr217) were associated with the second complex. The mobilities, collective motion, and B-factor of the two macromolecular complexes were analyzed. Finally, we developed different models, including trees, clusters, and heat maps of antiviral molecules, to evaluate the therapeutic status of favipiravir as an antiviral drug.

CONCLUSIONS

The results revealed the structural and molecular interaction landscape of the binding mode of favipiravir with the nsp7-nsp8-nsp12-RNA SARS-CoV-2 RdRp complex. Our findings can help future researchers in understanding the mechanism underlying viral action and guide the design of nucleotide analogs that mimic favipiravir and exhibit greater potency as antiviral drugs against SARS-CoV-2 and other infectious viruses. Thus, our work can help in preparing for future epidemics and pandemics.

Favipiravir in patients hospitalised with COVID-19 (PIONEER trial): a multicentre, open-label, phase 3, randomised controlled trial of early intervention versus standard care

BACKGROUND

COVID-19 has overwhelmed health services globally. Oral antiviral therapies are licensed worldwide, but indications and efficacy rates vary. We aimed to evaluate the safety and efficacy of oral favipiravir in patients hospitalised with COVID-19.

METHODS

We conducted a multicentre, open-label, randomised controlled trial of oral favipiravir in adult patients who were newly admitted to hospital with proven or suspected COVID-19 across five sites in the UK (n=2), Brazil (n=2) and Mexico (n=1). Using a permuted block design, eligible and consenting participants were randomly assigned (1:1) to receive oral favipiravir (1800 mg twice daily for 1 day; 800 mg twice daily for 9 days) plus standard care, or standard care alone. All caregivers and patients were aware of allocation and those analysing data were aware of the treatment groups. The prespecified primary outcome was the time from randomisation to recovery, censored at 28 days, which was assessed using an intention-to-treat approach. Post-hoc analyses were used to assess the efficacy of favipiravir in patients aged younger than 60 years, and in patients aged 60 years and older. The trial was registered with clinicaltrials.gov, NCT04373733.

FINDINGS

Between May 5, 2020 and May 26, 2021, we assessed 503 patients for eligibility, of whom 499 were randomly assigned to favipiravir and standard care (n=251) or standard care alone (n=248). There was no significant difference between those who received favipiravir and standard care, relative to those who received standard care alone in time to recovery in the overall study population (hazard ratio [HR] 1·06 [95% CI 0·89-1·27]; n=499; p=0·52). Post-hoc analyses showed a faster rate of recovery in patients younger than 60 years who received favipiravir and standard care versus those who had standard care alone (HR 1·35 [1·06-1·72]; n=247; p=0·01). 36 serious adverse events were observed in 27 (11%) of 251 patients administered favipiravir and standard care, and 33 events were observed in 27 (11%) of 248 patients receiving standard care alone, with infectious, respiratory, and cardiovascular events being the most numerous. There was no significant between-group difference in serious adverse events per patient (p=0·87).

INTERPRETATION

Favipiravir does not improve clinical outcomes in all patients admitted to hospital with COVID-19, however, patients younger than 60 years might have a beneficial clinical response. The indiscriminate use of favipiravir globally should be cautioned, and further high-quality studies of antiviral agents, and their potential treatment combinations, are warranted in COVID-19.

FUNDING

LifeArc and CW+.

Real-time monitoring of enzyme-catalyzed phosphoribosylation of anti-influenza prodrug favipiravir by time-lapse nuclear magnetic resonance spectroscopy

Favipiravir (brand name Avigan), a widely known anti-influenza prodrug, is metabolized by endogenous enzymes of host cells to generate the active form, which exerts inhibition of viral RNA-dependent RNA polymerase activity; first, favipiravir is converted to its phosphoribosylated form, favipiravir-ribofuranosyl-5'-monophosphate (favipiravir-RMP), by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Because this phosphoribosylation reaction is the rate-determining step in the generation of the active metabolite, quantitative and real-time monitoring of the HGPRT-catalyzed reaction is essential to understanding the pharmacokinetics of favipiravir. However, assay methods enabling such monitoring have not been established. ¹⁹ F- or ³¹ P-based nuclear magnetic resonance (NMR) are powerful techniques for observation of intermolecular interactions, chemical reactions, and metabolism of molecules of interest, given that NMR signals of the heteronuclei sensitively reflect changes in the chemical environment of these moieties. Here, we demonstrated direct, sensitive, target-selective, nondestructive, and real-time observation of HGPRT-catalyzed conversion of favipiravir to favipiravir-RMP by performing time-lapse ¹⁹ F-NMR monitoring of the fluorine atom of favipiravir. In addition, we showed that ³¹ P-NMR can be used for real-time observation of the identical reaction by monitoring phosphorus atoms of the phosphoribosyl group of favipiravir-RMP and of the pyrophosphate product of that reaction. Furthermore, we demonstrated that NMR approaches permit the determination of general parameters of enzymatic activity such as V_max and K_m . This method not only can be widely employed in enzyme assays, but also may be of use in the screening and development of new favipiravir-analog antiviral prodrugs that can be phosphoribosylated more efficiently by HGPRT, which would increase the intracellular concentration of the drug's active form. The techniques demonstrated in this study would allow more detailed investigation of the pharmacokinetics of fluorinated drugs, and might significantly contribute to opening new avenues for widespread pharmaceutical studies.

An Isomer of Galidesivir That Potently Inhibits Influenza Viruses and Members of the Bunyavirales Order

We report for the first time the antiviral activities of two iminovirs (antiviral imino-C-nucleosides) 1 and 2, structurally related to galidesivir (Immucillin A, BCX4430). An iminovir containing the 4-aminopyrrolo[2,1-f][1,2,4-triazine] nucleobase found in remdesivir exhibited submicromolar inhibition of multiple strains of influenza A and B viruses, as well as members of the Bunyavirales order. We also report the first syntheses of ProTide prodrugs of iminovir monophosphates, which unexpectedly displayed poorer viral inhibition than their parent nucleosides in vitro. An efficient synthesis of the 4-aminopyrrolo[2,1-f][1,2,4-triazine]-containing iminovir 2 was developed to enable preliminary in vivo studies, wherein it displayed significant toxicity in BALB/c mice and limited protection against influenza. Further modification of this anti-influenza iminovir will therefore be required to improve its therapeutic value.

Elucidating the Role of Noncovalent Interactions in Favipiravir, a Drug Active against Various Human RNA Viruses; a 1H-14N NQDR/Periodic DFT/QTAIM/RDS/3D Hirshfeld Surfaces Combined Study

Favipiravir (6-fluoro-3-hydroxypyrazine-2-carboxamide, FPV), an active pharmaceutical component of the drug discovered and registered in March 2014 in Japan under the name Avigan, with an indication for pandemic influenza, has been studied. The study of this compound was prompted by the idea that effective processes of recognition and binding of FPV to the nucleic acid are affected predominantly by the propensity to form intra- and intermolecular interactions. Three nuclear quadrupole resonance experimental techniques, namely ¹H-¹⁴N cross-relaxation, multiple frequency sweeps, and two-frequency irradiation, followed by solid-state computational modelling (density functional theory supplemented by the quantum theory of atoms in molecules, 3D Hirshfeld Surfaces, and reduced density gradient) approaches were applied. The complete NQR spectrum consisting of nine lines indicating the presence of three chemically inequivalent nitrogen sites in the FPV molecule was detected, and the assignment of lines to particular sites was performed. The description of the nearest vicinity of all three nitrogen atoms was used to characterize the nature of the intermolecular interactions from the perspective of the local single atoms and to draw some conclusions on the nature of the interactions required for effective recognition and binding. The propensity to form the electrostatic N-H···O, N-H···N, and C-H···O intermolecular hydrogen bonds competitive with two intramolecular hydrogen bonds, strong O-H···O and very weak N-H···N, closing the 5-member ring and stiffening the structure, as well as π···π and F···F dispersive interactions, were analysed in detail. The hypothesis regarding the similarity of the interaction pattern in the solid and the RNA template was verified. It was discovered that the -NH₂ group in the crystal participates in intermolecular hydrogen bonds N-H···N and N-H···O, in the precatalytic state only in N-H···O, while in the active state in N-H···N and N-H···O hydrogen bonds, which is of importance to link FVP to the RNA template. Our study elucidates the binding modes of FVP (in crystal, precatalytic, and active forms) in detail and should guide the design of more potent analogues targeting SARS-CoV-2. Strong direct binding of FVP-RTP to both the active site and cofactor discovered by us suggests a possible alternative, allosteric mechanism of FVP action, which may explain the scattering of the results of clinical trials or the synergistic effect observed in combined treatment against SARS-CoV-2.

Potential RNA-dependent RNA polymerase (RdRp) inhibitors as prospective drug candidates for SARS-CoV-2

The SARS-CoV-2 pandemic is considered as one of the most disastrous pandemics for human health and the world economy. RNA-dependent RNA polymerase (RdRp) is one of the key enzymes that control viral replication. RdRp is an attractive and promising therapeutic target for the treatment of SARS-CoV-2 disease. It has attracted much interest of medicinal chemists, especially after the approval of Remdesivir. This study highlights the most promising SARS-CoV-2 RdRp repurposed drugs in addition to natural and synthetic agents. Although many in silico predicted agents have been developed, the lack of in vitro and in vivo experimental data has hindered their application in drug discovery programs.

Cheminformatics-Based Study Identifies Potential Ebola VP40 Inhibitors

The Ebola virus (EBOV) is still highly infectious and causes severe hemorrhagic fevers in primates. However, there are no regulatorily approved drugs against the Ebola virus disease (EVD). The highly virulent and lethal nature of EVD highlights the need to develop therapeutic agents. Viral protein 40 kDa (VP40), the most abundantly expressed protein during infection, coordinates the assembly, budding, and release of viral particles into the host cell. It also regulates viral transcription and RNA replication. This study sought to identify small molecules that could potentially inhibit the VP40 protein by targeting the N-terminal domain using an in silico approach. The statistical quality of AutoDock Vina’s capacity to discriminate between inhibitors and decoys was determined, and an area under the curve of the receiver operating characteristic (AUC-ROC) curve of 0.791 was obtained. A total of 29,519 natural-product-derived compounds from Chinese and African sources as well as 2738 approved drugs were successfully screened against VP40. Using a threshold of −8 kcal/mol, a total of 7, 11, 163, and 30 compounds from the AfroDb, Northern African Natural Products Database (NANPDB), traditional Chinese medicine (TCM), and approved drugs libraries, respectively, were obtained after molecular docking. A biological activity prediction of the lead compounds suggested their potential antiviral properties. In addition, random-forest- and support-vector-machine-based algorithms predicted the compounds to be anti-Ebola with IC50 values in the micromolar range (less than 25 μM). A total of 42 natural-product-derived compounds were identified as potential EBOV inhibitors with desirable ADMET profiles, comprising 1, 2, and 39 compounds from NANPDB (2-hydroxyseneganolide), AfroDb (ZINC000034518176 and ZINC000095485942), and TCM, respectively. A total of 23 approved drugs, including doramectin, glecaprevir, velpatasvir, ledipasvir, avermectin B1, nafarelin acetate, danoprevir, eltrombopag, lanatoside C, and glycyrrhizin, among others, were also predicted to have potential anti-EBOV activity and can be further explored so that they may be repurposed for EVD treatment. Molecular dynamics simulations coupled with molecular mechanics Poisson–Boltzmann surface area calculations corroborated the stability and good binding affinities of the complexes (−46.97 to −118.9 kJ/mol). The potential lead compounds may have the potential to be developed as anti-EBOV drugs after experimental testing.

Antiviral Approaches against Influenza Virus

Preventing and controlling influenza virus infection remains a global public health challenge, as it causes seasonal epidemics to unexpected pandemics. These infections are responsible for high morbidity, mortality, and substantial economic impact. Vaccines are the prophylaxis mainstay in the fight against influenza. However, vaccination fails to confer complete protection due to inadequate vaccination coverages, vaccine shortages, and mismatches with circulating strains. Antivirals represent an important prophylactic and therapeutic measure to reduce influenza-associated morbidity and mortality, particularly in high-risk populations. Here, we review current FDA-approved influenza antivirals with their mechanisms of action, and different viral- and host-directed influenza antiviral approaches, including immunomodulatory interventions in clinical development. Furthermore, we also illustrate the potential utility of machine learning in developing next-generation antivirals against influenza.

Virus Management Using Metal-Organic Framework-Based Technologies

The eradication and isolation of viruses are two concurrent approaches to protect ourselves from viral infections and diseases. The quite versatile porous materials called metal-organic frameworks (MOFs), have recently emerged as efficient nanosized tools to manage viruses, and several strategies to accomplish these tasks have been developed. This review describes these strategies employing nanoscale MOFs against SARS-CoV-2, HIV-1, tobacco mosaic virus, etc., which include the sequestration by host-guest penetration inside pores, mineralization, design of a physical barrier, controlled delivery of organic and inorganic antiviral drugs or bioinhibitors, photosensitization of singlet oxygen, and direct contact with inherently cytotoxic MOFs.

Chemical synthesis of oligosaccharides and their application in new drug research

Oligosaccharides are the ubiquitous molecules of life. In order to translate human bioglycosylation into clinical applications, homogeneous samples of oligosaccharides and glycoconjugates can be obtained by chemical, enzymatic or other biological methods for systematic studies. However, the structural complexity and diversity of glycans and their conjugates present a major challenge for the synthesis of such molecules. This review summarizes the chemical synthesis methods of oligosaccharides, the application of oligosaccharides in the field of medicinal chemistry according to their related biological activities, and shows the great prospect of oligosaccharides in the field of pharmaceutical chemistry.

In vitro bio-characterization of solid lipid nanoparticles of favipiravir in A549 human lung epithelial cancer cells

Objectives

Lung cancer is a leading cause of mortality worldwide. In lung cancer treatment, nebulized solid lipid nanoparticles may be a viable drug delivery method, helping the drug reach sites of action, and improving its inhalation efficiency and pulmonary deposition. This research focused on evaluating the effectiveness of solid lipid nanoparticles of favipiravir (Fav-SLNps) in facilitating drug delivery to sites of action in lung cancer treatment.

Methods

The hot-evaporation method was used to formulate Fav-SLNps. The in vitro cell viability, anti-cancer effects, and cellular uptake activity were evaluated in A549 human lung adenocarcinoma cells treated with the Fav-SLNp formulation.

Results

The Fav-SLNps were formulated successfully. Importantly, Fav-SLNps at a concentration of 322.6 μg/ml were found to be safe and non-toxic toward A549 cells in vitro. The formulation had potential anti-proliferative properties via increasing the proportions of cells in G2/M and G0/G1 phases to 1.20 and 1.13 times those in untreated cells. Additionally, Fav-SLNp treatment significantly induced necrosis in A549 cells. Furthermore, the use of SLNps in the Fav formulation resulted in a macrophage drug uptake 1.23 times that of the free drug.

Conclusion

Our results confirmed the internalization and anti-cancer activity of the Fav-SLNp formulation in the A549 lung cancer cell line. Our findings suggest that Fav-SLNps could potentially be used as lung cancer treatment to facilitate drug delivery to sites of action in the lungs.

Comparative pathogenic potential of avian influenza H7N3 viruses isolated from wild birds in Egypt and their sensitivity to commercial antiviral drugs

Active surveillance and studying the virological features of avian-origin influenza viruses are essential for early warning and preparedness for the next potential pandemic. During our active surveillance of avian influenza viruses in wild birds in Egypt in the period 2014-2017, multiple reassortant low-pathogenic avian influenza H7N3 viruses were isolated. In this study, we investigated and compared the infectivity, pathogenicity, and transmission of four different constellation forms of Egyptian H7N3 viruses in chickens and mice and assessed the sensitivity of these viruses to different commercial antiviral drugs in vitro. Considerable variation in virus pathogenicity was observed in mice infected with different H7N3 viruses. The mortality rate ranged from 20 to 100% in infected mice. Infected chickens showed only ocular clinical signs at three days postinfection as well as systemic viral infection in different organs. Efficient virus replication and transmission in chickens was observed within each group, indicating that these subtypes can spread easily from wild birds to poultry without prior adaptation. Mutations in the viral proteins associated with antiviral drug resistance were not detected, and all strains were sensitive to the antiviral drugs tested. In conclusion, all of the viruses studied had the ability to infect mice and chickens. H7N3 viruses circulating among wild birds in Egypt could threaten poultry production and public health.

Evaluation of In Vitro Distribution and Plasma Protein Binding of Selected Antiviral Drugs (Favipiravir, Molnupiravir and Imatinib) against SARS-CoV-2

There are a number of uncertainties regarding plasma protein binding and blood distribution of the active drugs favipiravir (FAVI), molnupiravir (MOLNU) and imatinib (IMA), which were recently proposed as therapeutics for the treatment of COVID-19 disease. Therefore, proton dissociation processes, solubility, lipophilicity, and serum protein binding of these three substances were investigated in detail. The drugs display various degrees of lipophilicity at gastric (pH 2.0) and blood pH (pH 7.4). The determined pK_a values explain well the changes in lipophilic character of the respective compounds. The serum protein binding was studied by membrane ultrafiltration, frontal analysis capillary electrophoresis, steady-state fluorometry, and fluorescence anisotropy techniques. The studies revealed that the ester bond in MOLNU is hydrolyzed by protein constituents of blood serum. Molnupiravir and its hydrolyzed form do not bind considerably to blood proteins. Likewise, FAVI does not bind to human serum albumin (HSA) and α1-acid glycoprotein (AGP) and shows relatively weak binding to the protein fraction of whole blood serum. Imatinib binds to AGP with high affinity (logK' = 5.8-6.0), while its binding to HSA is much weaker (logK' ≤ 4.0). The computed constants were used to model the distribution of IMA in blood plasma under physiological and 'acute-phase' conditions as well.

Influenza antivirals and their role in pandemic preparedness

Effective antivirals provide crucial benefits during the early phase of an influenza pandemic, when vaccines are still being developed and manufactured. Currently, two classes of viral protein-targeting drugs, neuraminidase inhibitors and polymerase inhibitors, are approved for influenza treatment and post-exposure prophylaxis. Resistance to both classes has been documented, highlighting the need to develop novel antiviral options that may include both viral and host-targeted inhibitors. Such efforts will form the basis of management of seasonal influenza infections and of strategic planning for future influenza pandemics. This review focuses on the two classes of approved antivirals, their drawbacks, and ongoing work to characterize novel agents or combination therapy approaches to address these shortcomings. The importance of these topics in the ongoing process of influenza pandemic planning is also discussed.

Direct observation of backtracking by influenza A and B polymerases upon consecutive incorporation of the nucleoside analog T1106

The antiviral pseudo-base T705 and its de-fluoro analog T1106 mimic adenine or guanine and can be competitively incorporated into nascent RNA by viral RNA-dependent RNA polymerases. Although dispersed, single pseudo-base incorporation is mutagenic, consecutive incorporation causes polymerase stalling and chain termination. Using a template encoding single and then consecutive T1106 incorporation four nucleotides later, we obtained a cryogenic electron microscopy structure of stalled influenza A/H7N9 polymerase. This shows that the entire product-template duplex backtracks by 5 nt, bringing the singly incorporated T1106 to the +1 position, where it forms an unexpected T1106:U wobble base pair. Similar structures show that influenza B polymerase also backtracks after consecutive T1106 incorporation, regardless of whether prior single incorporation has occurred. These results give insight into the unusual mechanism of chain termination by pyrazinecarboxamide base analogs. Consecutive incorporation destabilizes the proximal end of the product-template duplex, promoting irreversible backtracking to a more energetically favorable overall configuration.

Preclinical development of kinetin as a safe error-prone SARS-CoV-2 antiviral able to attenuate virus-induced inflammation

Orally available antivirals against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are necessary because of the continuous circulation of new variants that challenge immunized individuals. Because severe COVID-19 is a virus-triggered immune and inflammatory dysfunction, molecules endowed with both antiviral and anti-inflammatory activity are highly desirable. We identified here that kinetin (MB-905) inhibits the in vitro replication of SARS-CoV-2 in human hepatic and pulmonary cell lines. On infected monocytes, MB-905 reduced virus replication, IL-6 and TNFα levels. MB-905 is converted into its triphosphate nucleotide to inhibit viral RNA synthesis and induce error-prone virus replication. Coinhibition of SARS-CoV-2 exonuclease, a proofreading enzyme that corrects erroneously incorporated nucleotides during viral RNA replication, potentiated the inhibitory effect of MB-905. MB-905 shows good oral absorption, its metabolites are stable, achieving long-lasting plasma and lung concentrations, and this drug is not mutagenic nor cardiotoxic in acute and chronic treatments. SARS-CoV-2-infected hACE-mice and hamsters treated with MB-905 show decreased viral replication, lung necrosis, hemorrhage and inflammation. Because kinetin is clinically investigated for a rare genetic disease at regimens beyond the predicted concentrations of antiviral/anti-inflammatory inhibition, our investigation suggests the opportunity for the rapid clinical development of a new antiviral substance for the treatment of COVID-19.

Influenza Treatment: Limitations of Antiviral Therapy and Advantages of Drug Combination Therapy

Influenza infection is serious and debilitating for humans and animals. The influenza virus undergoes incessant mutation, segment recombination, and genome reassortment. As a result, new epidemics and pandemics are expected to emerge, making the elimination challenging of the disease. Antiviral therapy has been used for the treatment of influenza since the development of amantadine in the 1960s; however, its use is hampered by the emergence of novel strains and the development of drug resistance. Thus, combinational therapy with two or more antivirals or immunomodulators with different modes of action is the optimal strategy for the effective treatment of influenza infection. In this review, we describe current options for combination therapy, their performance, and constraints imposed by resistance, calling attention to the advantages of combination therapy against severe influenza infections. We also discuss the challenges of influenza therapy and the limitations of approved antiviral drugs.

Identification of potent COVID-19 main protease inhibitors by loading of favipiravir on Mg12O12 and Zn12O12 nanoclusters: an in silico strategy for COVID-19 treatment

Pandemic new severe acute respiratory syndrome coronavirus (SARS-CoV-2) virus has increased throughout the world. There is no effective treatment against this virus until now. Since its appearance in Wuhan, China in December 2019, SARS-CoV-2 becomes the largest challenge the world is opposite today, including the discovery of an antiviral drug for this virus. Several viral proteins have been prioritized as SARS-CoV-2 antiviral drug targets, among them the papain-like protease (PLpro) and the main protease (Mpro). Inhibition of these proteases would target viral replication, viral maturation and suppression of host innate immune responses. Potential candidates have been identified to show inhibitory effects against Mpro, both in biochemical assays and viral replication in cells. There are different molecules such as lopinavir and favipiravir considerably inhibit the activity of Mpro in vitro. Different studies have shown that structurally improved favipiravir and other similar compounds can inhibit SARS-CoV-2 main protease. In this work, we study the interactions between favipiravir with Mg12O12 and Zn12O12 nanoclusters by density functional theory (DFT) and quantum mechanics atoms in molecules (QMAIM) methods to summarize the ability to load favipiravir onto Mg12O12 and Zn12O12 nanoclusters. Favipiravir-Mg12O12 and favipiravir-Zn12O12 lowest structures complexes were chosen to dock inside the SARS-CoV-2 main protease by molecular docking study. The molecular docking analysis revealed that the binding affinity of Mg12O12 and Zn12O12 nanoclusters inside the Mpro receptor is larger than that of favipiravir. Also, the loading of favipiravir on the surface of Mg12O12 and Zn12O12 nanoclusters increased the binding affinity against the Mpro receptor. Subsequently, 100 ns molecular dynamics simulation of the favipiravir-Mg12O12, and favipiravir-Zn12O12 docked inside the Mpro complexes established that favipiravir-Mg12O12, forms the most stable complex with the Mpro. Further molecular mechanics Poisson Boltzmann surface area (MMPBSA) analyses using the MD trajectories also demonstrated the higher binding affinity of favipiravir-Mg12O12 inside the Mpro. In summary, this study demonstrates a new way to characterize leads for novel anti-viral drugs against SARS-CoV-2, by improving the drug ability of favipiravir via loading it on Mg12O12 and Zn12O12 nanoclusters.Communicated by Ramaswamy H. Sarma.

Implications of the antiviral drug favipiravir on rabies immunoglobulin for post-exposure prophylaxis of rabies in mice model with category III-like exposures

Rabies is a fatal zoonotic disease caused by the rabies virus (RABV), with almost 100% mortality if proper post-exposure prophylaxis (PEP), consisting of rabies immunoglobulin (RIG) and rabies vaccine, is not applied in a timely manner. However, this is challenged by the limited availability of RIG, especially in resource-constrained countries. In this study, we assessed the scope of the antiviral drug favipiravir to treat rabies-infected mice as an alternative to RIG. Category III-like wounds were induced in RABV-challenged mice treated with favipiravir instead of RIG in the PEP regimen. The use of favipiravir followed by rabies vaccine provided complete protection against rabies-related death in 100% of mice, even after RABV propagated to the central nervous system during infection. Additionally, the virus-neutralizing antibody titer in the favipiravir and vaccine group was significantly higher than that of the RIG and vaccine recipients. The use of favipiravir with rabies vaccine seemingly prevents fatal outcomes and even rescues the cases that already express clinical symptoms. A clinical trial of this approach is warranted, especially in countries with low RIG availability.

Case report: Favipiravir-induced bluish corneal discoloration in infant with COVID-19

This report describes a case of a male infant diagnosed with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who was prescribed favipiravir therapy. The mother noticed a discoloration of the child's eyes within 18 h of therapy, and the cornea returned to normal color within 5 days of medication cessation. This case report highlights the need for monitoring of favipiravir therapy in children due to the potential side effect of corneal discoloration, which has not yet had its long-term effects identified.

In Silico Identification of Inhibitory Compounds for SARS-Cov-2 Papain-Like Protease

Virtual screening with high-performance computers is a powerful and cost-effective technique in drug discovery. A chemical database is searched to find candidate compounds firmly bound to a target protein, judging from the binding poses and/or binding scores. The severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infectious disease has spread worldwide for the last three years, causing severe slumps in economic and social activities. SARS-Cov-2 has two viral proteases: 3-chymotrypsin-like (3CL) and papain-like (PL) protease. While approved drugs have already been released for the 3CL protease, no approved agent is available for PL protease. In this work, we carried out in silico screening for the PL protease inhibitors, combining docking simulation and molecular mechanics calculation. Docking simulations were applied to 8,820 molecules in a chemical database of approved and investigational compounds. Based on the binding poses generated by the docking simulations, molecular mechanics calculations were performed to optimize the binding structures and to obtain the binding scores. Based on the binding scores, 57 compounds were selected for in vitro assay of the inhibitory activity. Five inhibitory compounds were identified from the in vitro measurement. The predicted binding structures of the identified five compounds were examined, and the significant interaction between the individual compound and the protease catalytic site was clarified. This work demonstrates that computational virtual screening by combining docking simulation with molecular mechanics calculation is effective for searching candidate compounds in drug discovery.

A Review of Pathology and Analysis of Approaches to Easing Kidney Disease Impact: Host-Pathogen Communication and Biomedical Visualization Perspective : Advanced Microscopy and Visualization of Host-Pathogen Communication

INTRODUCTION

In addition to affecting the upper respiratory tract, severe acute respiratory syndrome-coronavirus (SARS-CoV) and SARS-CoV-2) can target kidneys resulting in disease impact. There is a lack of effective treatment for SARs-CoV and SARS-CoV-2, and so one approach could be to consider to lower the probable risk and onset of disease amongst immunocompromised and immunosuppressed individuals and patients. Angiotensin Converting Enzyme 2 (ACE2) has a promising impact including acting against SARs-CoV and SARS-CoV-2 symptoms. Current literature states that ACE2 is expressed across several physiological systems, including the lungs, cardiovascular, gut, kidneys, and central nervous, and across endothelia.

AIMS

This chapter seeks to investigate causes and potential mechanisms during SARS infection (CoV-2), renal interaction, and the effects of acute kidney Injury (AKI).

OBJECTIVES

This chapter will provide an overview of microscopy and visualization of host-pathogen communication and principles of ACE2 in the context of immunology and impact on renal pathophysiology.

DESIGN

This chapter focuses to provide basic principles of ACE2 and the analysis and effect of immunology and pathological components important in relation to SARs infection.

DISCUSSION

There has been a surge in literature surrounding mechanisms attributing to SARS-CoV and SARS-CoV-2 action on immune response to pathogens. There is an advantage to implementing ACE2 treatment to improve immune response against infection.

CONCLUSION

ACE2 may provide appropriate strategies for the management of symptoms that relate to SARS-CoV and SARS-CoV-2 in most immunocompromised or immunosuppressed patients. Visualization of ACE2 action can be achieved through microscopy to understand host-pathogen communication.

Favipiravir-Tautomeric and Complexation Properties in Solution

The tautomeric properties of favipiravir were investigated experimentally for the first time by using molecular spectroscopy (UV-Vis absorption, fluorescence and NMR), as well as DFT quantum-chemical calculations. According to the obtained results, the enol tautomer is substantially more stable in most of the organic solvents. In the presence of water, a keto form appears to be favored due to the specific solute-solvent interactions. Upon the addition of alkaline-earth-metal ions, deprotonation and complexation occurred simultaneously, giving the formation of 2 : 1 ligand : metal complexes. According to the theoretical simulations, the metal ion is captured between the carbonyl groups as a result of the size-fit effect.

Small-molecule metabolites in SARS-CoV-2 treatment: a comprehensive review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has quickly spread all over the world. In this respect, traditional medicinal chemistry, repurposing, and computational approaches have been exploited to develop novel medicines for treating this condition. The effectiveness of chemicals and testing methods in the identification of new promising therapies, and the extent of preparedness for future pandemics, have been further highly advantaged by recent breakthroughs in introducing noble small compounds for clinical testing purposes. Currently, numerous studies are developing small-molecule (SM) therapeutic products for inhibiting SARS-CoV-2 infection and replication, as well as managing the disease-related outcomes. Transmembrane serine protease (TMPRSS2)-inhibiting medicinal products can thus prevent the entry of the SARS-CoV-2 into the cells, and constrain its spreading along with the morbidity and mortality due to the coronavirus disease 2019 (COVID-19), particularly when co-administered with inhibitors such as chloroquine (CQ) and dihydroorotate dehydrogenase (DHODH). The present review demonstrates that the clinical-stage therapeutic agents, targeting additional viral proteins, might improve the effectiveness of COVID-19 treatment if applied as an adjuvant therapy side-by-side with RNA-dependent RNA polymerase (RdRp) inhibitors.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and Mpro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Significant perspectives on various viral infections targeted antiviral drugs and vaccines including COVID-19 pandemicity

A virus enters a living organism and recruits host metabolism to reproduce its own genome and proteins. The viral infections are intricate and cannot be completely removed through existing antiviral drugs. For example, the herpes, influenza, hepatitis and human immunodeficiency viruses are a few dreadful ones amongst them. Significant studies are needed to understand the viral entry and their growth in host cells to design effective antivirals. This review emphasizes the range of therapeutical antiviral drugs, inhibitors along with vaccines to fight against viral pathogens, especially for combating COVID-19. Moreover, we have provided the basic and in depth information about viral targets, drugs availability, their mechanisms of action, method of prevention of viral diseases and highlighted the significances of anticoagulants, convalescent plasma for COVID-19 treatment, scientific details of airborne transmission, characteristics of antiviral drug delivery using nanoparticles/carriers, nanoemulsions, nanogels, metal based nanoparticles, alike the future nanosystems through nanobubbles, nanofibers, nanodiamonds, nanotraps, nanorobots and eventually, the therapeutic applications of micro- and nanoparticulates, current status for clinical development against COVID-19 together with environmental implications of antivirals, gene therapy etc., which may be useful for repurposing and designing of novel antiviral drugs against various dreadful diseases, especially the SARS-CoV-2 and other associated variants.

A comprehensive review on pharmacologic agents, immunotherapies and supportive therapeutics for COVID-19

The emergence of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected many countries throughout the world. As urgency is a necessity, most efforts have focused on identifying small molecule drugs that can be repurposed for use as anti-SARS-CoV-2 agents. Although several drug candidates have been identified using in silico method and in vitro studies, most of these drugs require the support of in vivo data before they can be considered for clinical trials. Several drugs are considered promising therapeutic agents for COVID-19. In addition to the direct-acting antiviral drugs, supportive therapies including traditional Chinese medicine, immunotherapies, immunomodulators, and nutritional therapy could contribute a major role in treating COVID-19 patients. Some of these drugs have already been included in the treatment guidelines, recommendations, and standard operating procedures. In this article, we comprehensively review the approved and potential therapeutic drugs, immune cells-based therapies, immunomodulatory agents/drugs, herbs and plant metabolites, nutritional and dietary for COVID-19.

Favipiravir in SARS-CoV-2 Infection: Is it Worth it?

Favipiravir is a potential antiviral drug undergoing clinical trials to manage various viral infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Favipiravir possesses antiviral properties against RNA viruses, including SARS-CoV-2. Unfortunately, these viruses do not have authorized antiviral drugs for the management of diseases resulting from their infection, hence the dire need to accentuate the discovery of antiviral drugs that are efficacious and have a broad spectrum. Favipiravir acts primarily by blocking inward and outward movements of the virus from cells. Favipiravir is a prodrug undergoing intracellular phosphorylation and ribosylation to form an active form, favipiravir-RTP, which binds viral RNA-dependent RNA polymerase (RdRp). Considering the novel mechanism of favipiravir action, especially in managing viral infections, it is vital to pay more attention to the promised favipiravir hold in the management of SARS-CoV-2, its efficacy, and dosage regimen, and interactions with other drugs. In conclusion, favipiravir possesses antiviral properties against RNA viruses, including COVID- 19. Favipiravir is effective against SARS-CoV-2 infection through inhibition of RdRp. Pre-clinical and large-scalp prospective studies are recommended for efficacy and long-term safety of favipiravir in COVID-19.

Considerations into pharmacogenomics of COVID-19 pharmacotherapy: Hope, hype and reality

COVID-19 medicines, such as molnupiravir are beginning to emerge for public health and clinical practice. On the other hand, drugs display marked variability in their efficacy and safety. Hence, COVID-19 medicines, as with all drugs, will be subject to the age-old maxim "one size prescription does not fit all". In this context, pharmacogenomics is the study of genome-by-drug interactions and offers insights on mechanisms of patient-to-patient and between-population variations in drug efficacy and safety. Pharmacogenomics information is crucial to tailoring the patients' prescriptions to achieve COVID-19 preventive and therapeutic interventions that take into account the host biology, patients' genome, and variable environmental exposures that collectively influence drug efficacy and safety. This expert review critically evaluates and summarizes the pharmacogenomics and personalized medicine aspects of the emerging COVID-19 drugs, and other selected drug interventions deployed to date. Here, we aim to sort out the hope, hype, and reality and suggest that there are veritable prospects to advance COVID-19 medicines for public health benefits, provided that pharmacogenomics is considered and implemented adequately. Pharmacogenomics is an integral part of rational and evidence-based medical practice. Scientists, health care professionals, pharmacists, pharmacovigilance practitioners, and importantly, patients stand to benefit by expanding the current pandemic response toolbox by the science of pharmacogenomics, and its applications in COVID-19 medicines and clinical trials.

Pulmonary delivery of favipiravir inhalation solution for COVID-19 treatment: in vitro characterization, stability, in vitro cytotoxicity, and antiviral activity using real time cell analysis

Favipiravir, an RNA-dependent RNA polymerase (RdRp) inhibitor, is used to treat patients infected with influenza virus and most recently with SARS-CoV-2. However, poor accumulation of favipiravir in lung tissue following oral administration has required an alternative method of administration that directly targets the lungs. In this study, an inhalation solution of favipiravir at a concentration of 2 mg mL^-1 was developed and characterized for the first time. The chemical stability of inhaled favipiravir solution in two different media, phosphate buffer saline (PBS) and normal saline (NS), was investigated under different conditions: 5 ± 3 °C, 25 ± 2 °C/60% RH ± 5% RH, and 40 ± 2 °C/75% RH ± 5% RH; in addition to constant light exposure. As a result, favipiravir solution in PBS revealed superior stability over 12 months at 5 ± 3 °C. Antiviral activity of favipiravir was assessed at the concentrations between 0.25 and 3 mg mL^-1 with real time cell analyzer on Vero-E6 that were infected with SARS-CoV-2/B.1.36. The optimum concentration was found to be 2 mg mL^-1, where minimum toxicity and sufficient antiviral activity was observed. Furthermore, cell viability assay against Calu-3 lung epithelial cells confirmed the biocompatibility of favipiravir at concentrations up to 50 μM (7.855 mg mL^-1). The in vitro aerodynamic profiles of the developed inhaled favipiravir formulation, when delivered with soft-mist inhaler indicated good lung targeting properties. These results suggest that favipiravir solution prepared with PBS could be considered as a suitable and promising inhalation formulation for pulmonary delivery in the treatment of patients with COVID-19.

An Overview of Repurposed Drugs for Potential COVID-19 Treatment

The COVID-19 pandemic caused by SARS-CoV-2 has placed severe constraints on healthcare systems around the globe. The SARS-CoV-2 virus has caused upheaval in the healthcare and economic sectors worldwide. On the 20th of May 2020, the World Health Organisation declared COVID-19 a global pandemic due to the unprecedented number of cases reported around the globe. As of the 4th of November 2022, there were 637,117,429 coronavirus cases reported globally by Worldometer stats, with 6,602,572 related deaths. In South Africa, there were approximately 4,029,496 coronavirus cases and 102,311 associated deaths. As such, there is a need for efficacious therapeutic regimes. There has been a paucity of knowledge encompassing the use of effective and specific antiviral drug therapies for treating COVID-19 since the outbreak. In this review, we provide valuable insights into the repurposing of current drugs for COVID-19. Drug repurposing provides a suitable option for the discovery of efficacious drugs for COVID-19, thereby decreasing the costs and turnaround times of drug development strategies. This review provides an overview of ten drugs, including antimalarial, antiparasitic, anti-inflammatory, nucleoside analogue, monoclonal-antibody drugs, that were repurposed for the potential treatment of COVID-19.

Voltammetric Determination of Favipiravir Used as an Antiviral Drug for the Treatment of Covid-19 at Pencil Graphite Electrode

This work describes the sensitive voltammetric determination of favipiravir (FAV) based on its reduction for the first time with a low-cost and disposable pencil graphite electrode (PGE). In addition, the determination of FAV was also performed based on its oxidation. Differential pulse (DP) voltammograms recorded in 0.5 M H2SO4 for the reduction of FAV show that peak currents increase linearly in the range of 1.0 to 600.0 μM with a limit of detection of 0.35 μM. The acceptable recovery values (98.9-106.0 %) obtained from a pharmaceutical tablet, real human urine, and artificial blood serum samples spiked with FAV confirm the high accuracy of the proposed method.

An update on inhibitors targeting RNA-dependent RNA polymerase for COVID-19 treatment: Promises and challenges

The highly transmissible variants of SARS-CoV-2, the causative pathogen of the COVID-19 pandemic, bring new waves of infection worldwide. Identification of effective therapeutic drugs to combat the COVID-19 pandemic is an urgent global need. RNA-dependent RNA polymerase (RdRp), an essential enzyme for viral RNA replication, is the most promising target for antiviral drug research since it has no counterpart in human cells and shows the highest conservation across coronaviruses. This review summarizes recent progress in studies of RdRp inhibitors, focusing on interactions between these inhibitors and the enzyme complex, based on structural analysis, and their effectiveness. In addition, we propose new possible strategies to address the shortcomings of current inhibitors, which may guide the development of novel efficient inhibitors to combat COVID-19.

Progression of Antiviral Agents Targeting Viral Polymerases

Viral DNA and RNA polymerases are two kinds of very important enzymes that synthesize the genetic materials of the virus itself, and they have become extremely favorable targets for the development of antiviral drugs because of their relatively conserved characteristics. There are many similarities in the structure and function of different viral polymerases, so inhibitors designed for a certain viral polymerase have acted as effective universal inhibitors on other types of viruses. The present review describes the development of classical antiviral drugs targeting polymerases, summarizes a variety of viral polymerase inhibitors from the perspective of chemically synthesized drugs and natural product drugs, describes novel approaches, and proposes promising development strategies for antiviral drugs.

Lassa Virus Countermeasures

Lassa Fever (LF) is a viral hemorrhagic fever endemic in West Africa. LF begins with flu-like symptoms that are difficult to distinguish from other common endemic diseases such as malaria, dengue, and yellow fever making it hard to diagnose clinically. Availability of a rapid diagnostic test and other serological and molecular assays facilitates accurate diagnosis of LF. Lassa virus therapeutics are currently in different stages of preclinical development. Arevirumab, a cocktail of monoclonal antibodies, demonstrates a great safety and efficacy profile in non-human primates. Major efforts have been made in the development of a Lassa virus vaccine. Two vaccine candidates, MeV-NP and pLASV-GPC are undergoing evaluation in phase I clinical trials.

The Novel hDHODH Inhibitor MEDS433 Prevents Influenza Virus Replication by Blocking Pyrimidine Biosynthesis

The pharmacological management of influenza virus (IV) infections still poses a series of challenges due to the limited anti-IV drug arsenal. Therefore, the development of new anti-influenza agents effective against antigenically different IVs is therefore an urgent priority. To meet this need, host-targeting antivirals (HTAs) can be evaluated as an alternative or complementary approach to current direct-acting agents (DAAs) for the therapy of IV infections. As a contribution to this antiviral strategy, in this study, we characterized the anti-IV activity of MEDS433, a novel small molecule inhibitor of the human dihydroorotate dehydrogenase (hDHODH), a key cellular enzyme of the de novo pyrimidine biosynthesis pathway. MEDS433 exhibited a potent antiviral activity against IAV and IBV replication, which was reversed by the addition of exogenous uridine and cytidine or the hDHODH product orotate, thus indicating that MEDS433 targets notably hDHODH activity in IV-infected cells. When MEDS433 was used in combination either with dipyridamole (DPY), an inhibitor of the pyrimidine salvage pathway, or with an anti-IV DAA, such as N⁴-hydroxycytidine (NHC), synergistic anti-IV activities were observed. As a whole, these results indicate MEDS433 as a potential HTA candidate to develop novel anti-IV intervention approaches, either as a single agent or in combination regimens with DAAs.

Potential Drug Interaction Between Favipiravir and Warfarin in Patients With COVID-19: A Real-World Observational Study

Favipiravir is one of the most used antiviral agents for the treatment of coronavirus disease 2019 infection in many countries, including Thailand. This study aimed to investigate the effect of favipiravir-warfarin interaction in terms of changes in international normalized ratio (INR) of patients. Medication charts of all inpatients in a hospital in Thailand between April 2021 and March 2022 were reviewed. Patients who received either warfarin with standard care or warfarin with favipiravir were included. The INR levels of patients were monitored at baseline and the earliest date following treatment, as well as other laboratory parameters. There were 43 and 53 patients in the warfarin-favipiravir and the warfarin-only groups, respectively. Baseline characteristics, such as sex, age, body mass index, and warfarin dose, were not significantly different between the 2 groups. The results showed that the mean INR of patients using favipiravir and warfarin was increased from 2.14 to 3.88 (P < .001), while the patients using warfarin alone had no increase in the mean INR (1.93 vs 1.91; P = .906). Other parameters were not significantly changed, including white blood cell count, red blood cell count, hemoglobin, hematocrit, and liver function. However, an increase in platelet count was observed in the favipiravir-warfarin group, but not in the control group. This real-world study highlighted a significant increase in the INR levels of patients who used favipiravir together with warfarin, compared to patients who used only warfarin. However, the interaction did not affect other laboratory parameters, except an increase in platelet count.

Electrochemical Sensing of Favipiravir with an Innovative Water-Dispersible Molecularly Imprinted Polymer Based on the Bimetallic Metal-Organic Framework: Comparison of Morphological Effects

Molecularly imprinted polymers (MIPs) are widely used as modifiers in electrochemical sensors due to their high sensitivity and promise of inexpensive mass manufacturing. Here, we propose and demonstrate a novel MIP-sensor that can measure the electrochemical activity of favipiravir (FAV) as an antiviral drug, thereby enabling quantification of the concentration of FAV in biological and river water samples and in real-time. MOF nanoparticles’ application with various shapes to determine FAV at nanomolar concentrations was described. Two different MOF nanoparticle shapes (dodecahedron and sheets) were systematically compared to evaluate the electrochemical performance of FAV. After carefully examining two different morphologies of MIP-Co-Ni@MOF, the nanosheet form showed a higher performance and efficiency than the nanododecahedron. When MIP-Co/Ni@MOF-based and NIP-Co/Ni@MOF electrodes (nanosheets) were used instead, the minimum target concentrations detected were 7.5 × 10−11 (MIP-Co-Ni@MOF) and 8.17 × 10−9 M (NIP-Co-Ni@MOF), respectively. This is a significant improvement (>102), which is assigned to the large active surface area and high fraction of surface atoms, increasing the amount of greater analyte adsorption during binding. Therefore, water-dispersible MIP-Co-Ni@MOF nanosheets were successfully applied for trace-level determination of FAV in biological and water samples. Our findings seem to provide useful guidance in the molecularly imprinted polymer design of MOF-based materials to help establish quantitative rules in designing MOF-based sensors for point of care (POC) systems.

Insights on the Quantitative Concurrent Fluorescence-Based Analysis of Anti-COVID-19 Drugs Remdesivir and Favipiravir

We hereby introduce a sensitive fast straightforward spectrofluorometric method for the estimation of remdesivir and favipiravir. The two drugs are prescribed in some regimens to treat COVID-19 pandemic disease, which is caused by SARS-CoV-2. The method is based on the first derivative synchronous spectrofluorimetry approach for the measurement of remdesivir and favipiravir. This was accomplished at 251 nm and 335 nm respectively using the first derivative order at delta lambda of 140 nm. A linear response with a correlation coefficient 0.9994 was achieved between the concentration and the derivative amplitudes in the ranges of 20.0-100.0 ng ml-1 and 40.0-100.0 ng ml-1 for remdesivir and favipiravir, respectively. The methods were validated for different parameters as stated by the pharmacopeial rules and were applied successfully for estimation of the studied drugs in their synthetic mixtures and in spiked human plasma samples. No significant difference was observed between the proposed and comparison methods as revealed from the analysis of data.

Influenza

Annual seasonal influenza epidemics of variable severity caused by influenza A and B virus infections result in substantial disease burden worldwide. Seasonal influenza virus circulation declined markedly in 2020-21 after SARS-CoV-2 emerged but increased in 2021-22. Most people with influenza have abrupt onset of respiratory symptoms and myalgia with or without fever and recover within 1 week, but some can experience severe or fatal complications. Prevention is primarily by annual influenza vaccination, with efforts underway to develop new vaccines with improved effectiveness. Sporadic zoonotic infections with novel influenza A viruses of avian or swine origin continue to pose pandemic threats. In this Seminar, we discuss updates of key influenza issues for clinicians, in particular epidemiology, virology, and pathogenesis, diagnostic testing including multiplex assays that detect influenza viruses and SARS-CoV-2, complications, antiviral treatment, influenza vaccines, infection prevention, and non-pharmaceutical interventions, and highlight gaps in clinical management and priorities for clinical research.

SARS-CoV-2 pre-exposure prophylaxis: A potential COVID-19 preventive strategy for high-risk populations, including healthcare workers, immunodeficient individuals, and poor vaccine responders

The unprecedented worldwide spread of SARS-CoV-2 has imposed severe challenges on global health care systems. The roll-out and widespread administration of COVID-19 vaccines has been deemed a major milestone in the race to restrict the severity of the infection. Vaccines have as yet not entirely suppressed the relentless progression of the pandemic, due mainly to the emergence of new virus variants, and also secondary to the waning of protective antibody titers over time. Encouragingly, an increasing number of antiviral drugs, such as remdesivir and the newly developed drug combination, Paxlovid® (nirmatrelvir/ritonavir), as well as molnupiravir, have shown significant benefits for COVID-19 patient outcomes. Pre-exposure prophylaxis (PrEP) has been proven to be an effective preventive strategy in high-risk uninfected people exposed to HIV. Building on knowledge from what is already known about the use of PrEP for HIV disease, and from recently gleaned knowledge of antivirals used against COVID-19, we propose that SARS-CoV-2 PrEP, using specific antiviral and adjuvant drugs against SARS-CoV-2, may represent a novel preventive strategy for high-risk populations, including healthcare workers, immunodeficient individuals, and poor vaccine responders. Herein, we critically review the risk factors for severe COVID-19 and discuss PrEP strategies against SARS-CoV-2. In addition, we outline details of candidate anti-SARS-CoV-2 PrEP drugs, thus creating a framework with respect to the development of alternative and/or complementary strategies to prevent COVID-19, and contributing to the global armamentarium that has been developed to limit SARS-CoV-2 infection, severity, and transmission.

Rapid and ecofriendly UPLC quantification of Remdesivir, Favipiravir and Dexamethasone for accurate therapeutic drug monitoring in Covid-19 Patient's plasma

Innovative therapeutic protocols to the rapidly spreading coronavirus disease (COVID19) epidemic is highly required all across the world. As demonstrated by clinical studies, Favipiravir (FVP) and Remdesivir (REM) are new antiviral medicines that are effective against COVID-19. REM is the first FDA approved antiviral medicine against COVID-19. In addition to antivirals, corticosteroids such as dexamethasone (DEX), and anticoagulants such as apixaban (PX) are used in multidrug combinations protocols. This work develops and validates simple and selective screening of the four medicines of COVID -19 therapeutic protocol. FVP, REM, DEX, and PX as internal standard in human plasma using UPLC method by C18 column and methanol, acetonitrile, and water acidified by orthophosphate (pH = 4) in a ratio of (15: 35: 50, by volume) as an eluate flowing at 0.3 mL/min. The eluent was detected at 240 nm. The method was linear over (0.1-10 μg/mL) for each of FVP, REM, and DEX. The validation of the UPLC method was assessed in accordance with FDA guidelines. The method can detect as low as down to 0.1 μg/mL for all. The recoveries of the drugs in spiked human plasma ranged from 97.67 to 102.98 percent. Method accuracy and precision were assessed and the drugs showed good stability. The method was proven to be green to the environment after greenness checking by greenness profile and Eco-Scale tool.

Effect of Hydroxychloroquine, Favipiravir, Lopinavir/Ritonavir, Remdesivir, Umifenovir, and Interferon beta-1a in Covid-19 patients: A systematic review of Randomized Clinical Trials

"Background: Coronavirus disease 2019 (COVID-19) was recognized by the World Health Organization (WHO) as a global pandemic on March 11, 2020. Since then, researchers worldwide have focused their attention on identifying effective treatments and developing vaccines to combat this disease. Aim: To report the effectiveness of the drugs employed in the COVID-19 treatment protocols based on data from clinical trial studies conducted from the beginning of the pandemic until December 10, 2020. Methods: Following the PRISMA guidelines, we conducted an advanced search in several electronic databases. A total of 13553 studies was screened by two people simultaneously and separately based on the article title, abstract and full-text. The quality of the studies was evaluated using the Cochrane criteria. Results: Of the 13553 studies identified, 50 clinical trials were included in this systematic review. Of these, three studies explored the use of remdesivir, nine studies the use of hydroxychloroquine, five studies the use of lopinavir/ritonavir, six studies the use of favipiravir, one study the use of tocilizumab, two studies the use of interferon beta-1a and two studies the use of umifenovir. "

Antiviral therapy for COVID-19: Derivation of optimal strategy based on past antiviral and favipiravir experiences

Favipiravir, a broad-spectrum RNA-dependent RNA polymerase inhibitor, inhibits the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at significantly lower concentrations than the plasma trough levels achieved by the dosage adopted for influenza treatment and exhibits efficacy against coronavirus disease 2019 (COVID-19) pneumonia. Although high doses of favipiravir are required due to the molecule being a purine analog, its conversion into the active form in infected cells with active viral RNA synthesis enhances the antiviral specificity and selectivity as a chain terminator with lethal mutagenesis. Another characteristic feature is the lack of generation of favipiravir-resistant virus. COVID-19 pneumonia is caused by strong cell-mediated immunity against virus-infected cells, and the inflammatory response induced by adaptive immunity continues to peak for 3 to 5 days despite antiviral treatment. This has also been observed in herpes zoster (HZ) and cytomegalovirus (CMV) pneumonia. Inflammation due to an immune response may mask the effectiveness of favipiravir against COVID-19 pneumonia. Favipiravir significantly shortened the recovery time in patients with mild COVID-19 pneumonia by 3 days with the start of treatment by the 5th day of symptom onset. Since both CMV and COVID-19 pneumonia are caused by adaptive immunity and prevention of cytomegalovirus pneumonia is the standard treatment due to difficulties in treating refractory CMV pneumonia, COVID-19 pneumonia should be prevented with early treatment as well. In the present study, we have comprehensively reviewed the optimal antiviral therapy for COVID-19 based on clinical trials of favipiravir for the treatment of COVID-19 pneumonia and the concurrently established therapies for other viral infections, particularly HZ and CMV pneumonia. Optimally, antivirals should be administered immediately after COVID-19 diagnosis, similar to that after influenza diagnosis, to prevent COVID-19 pneumonia and complications resulting from microangiopathy.

The efficacy and adverse effects of favipiravir on patients with COVID-19: A systematic review and meta-analysis of published clinical trials and observational studies

OBJECTIVES

This study aimed to evaluate the efficacy and adverse events of favipiravir in patients with COVID-19.

METHODS

Our protocol was registered on PROSPERO (CRD42020206305). Fourteen databases were searched until February 8th, 2021. An update search for new RCTs was done on March 2nd, 2022. Meta-analysis was done for randomized controlled trials (RCTs) and non-RCTs.

RESULTS

Overall, 157 studies (24 RCTs, 1 non-RCT, 21 observational studies, 2 case series, and 106 case reports) were included. On hospitalized patients, in comparison to standard of care, favipiravir showed a higher rate of viral clearance at day 5 (RR = 1.60, p = 0.02), defervescence at day 3-4 (RR = 1.99, p <0.01), chest radiological improvement (RR = 1.33, p <0.01), hospital discharge at day 10-11 (RR = 1.19, p <0.01), and shorter clinical improvement time (MD = -1.18, p = 0.05). Regarding adverse events, favipiravir groups had higher rates of hyperuricemia (RR = 9.42, p <0.01), increased alanine aminotransferase (RR = 1.35, p <0.01) but lower rates of nausea (RR = 0.42, p <0.01) and vomiting (R R= 0.19, p=0.02). There were no differences regarding mortality (RR=1.19, p=0.32), and increased aspartate aminotransferase (RR = 1.11, p = 0.25). On nonhospitalized patients, no significant differences were reported.

CONCLUSIONS

Adding favipiravir to the standard of care provides better outcomes for hospitalized patients with COVID-19. Pregnant, lactating women, and patients with a history of hyperuricemia should avoid using favipiravir.

Supplemental Medicines-Nutritions Used by Health Personnel in their own Covid-19 Treatment Schedule

ABSTRACT OBJECTIVE. İn this study, with a view to investigate drug use behaviors of healthcare personnels who had Covid 19 infection in the first 1 year of the pandemic, it was aimed to determine the additional drugs and nutritional supplements they used in their own treatment. MATERIAL METHOD This is a descriptive cross-sectional study. The data were obtained through an online survey voluntarily completed under pandemic conditions by doctors, dentists, nurses, pharmacists and other health personnel who declared that they had Covid-19. RESULTS The study consisted of 405 individuals. 98% of healthcare personnels preferred to support their treatment. The medicines and herbal products that the participants started to use by their own decisions, without the advice of the physician who examined them, and the frequency of their use were vitamin C 53.3%, vitamin D 48.1%, acetylsalicylic acid 26.7%, paracetamol 23%, zinc 26.4%, multivitamin 19%, acetylcysteine 14.8%, famotidine 14.3%, subcutaneous heparin 12.6%. As for herbal products, inhaling thyme oil was noted in 11.6%, drinking thyme oil 10.1%, consuming ginger 14.3% of the participants. Non-prescription support products were found to be beneficial in 44.4%. CONCLUSION Almost all of the participants took a supplement with an intention to support the treatment. The fact that one out of two participants declared that they benefited from over-the-counter supplements reveals that further studies are needed to support the rational use of over-the-counter products in the treatment of Covid 19.

Current strategies in diagnostics and therapeutics against novel coronavirus disease (COVID-19)

The epidemic of COVID-19 spread quickly through China and engulfed all of the countries across the globe. Several advances have been made in understanding the novel coronavirus's pathophysiology and in the development of newer diagnostics with pinpoint accuracy. Several newer therapeutic methods have either been accepted or are awaiting acceptance. In many countries, vaccination programs have been rolled out. Despite all these efforts, coronavirus still exists, though with lesser propensity. Multiple new forms of the novel coronavirus unexpectedly appeared in various areas of the world, undermining previously existing diagnosis and care protocols. This article highlights our understanding of the novel coronavirus's symptoms in brief, pathogenesis, diagnostics, and therapeutic strategies to contain COVID-19. The clinical findings, including serological, radiological, and other advanced diagnostic strategies, contributed much to control the disease. To date, supportive interventions have been used in tandem with potent antiviral therapies such as remdesivir, lopinavir/ritonavir, or corticosteroids with a level of trust in the care of COVID-19 patients. However, in several areas of the world, vaccination initiatives took place; the vaccines' safety and efficacy to control the outbreak is yet to be identified. This review concludes that improvement in therapies and diagnostics for COVID-19 must continually be explored as new variants constantly emerge.