Design of novel pyrimidine based remdesivir analogues with dual target specificity for SARS CoV-2: A computational approach.

As the world undergone unpreceded time of tragedy with the corona virus, many researchers have raised to showcase their scientific contributions in terms of novel configured anti-viral drugs until now. Herein, we designed pyrimidine based nucleotides and assessed for the binding capability with SARS-CoV-2 viral replication targets of nsp12 RNA-dependent RNA polymerase and Mpro main protease. Molecular docking studies showed all the designed compounds to possess good binding affinity, with a few compounds which outperforms the control drug remdesivir GS-5743 and its active form GS-441524. Further molecular dynamics simulation studies confirmed their stability and preservation of the non-covalent interactions. Based on the present findings Ligand2-BzV_0Tyr, ligand3-BzV_0Ura, and ligand5-EeV_0Tyr showed good binding affinity with Mpro, whereas, ligand1-BzV_0Cys and Ligand2-BzV_0Tyr showed good binding affinity with RdRp, thus could act as potential lead compounds against SARS-CoV-2, which needs further validation studies. In particular, Ligand2-BzV_0Tyr could be more beneficial candidate with the dual target specificity for Mpro and RdRp.

Production of Modified Nucleosides in a Continuous Enzyme Membrane Reactor.

Nucleoside analogues are important compounds for the treatment of viral infections or cancers. While (chemo-)enzymatic synthesis is a valuable alternative to traditional chemical methods, the feasibility of such processes is lowered by the high production cost of the biocatalyst. As continuous enzyme membrane reactors (EMR) allow the use of biocatalysts until their full inactivation, they offer a valuable alternative to batch enzymatic reactions with freely dissolved enzymes. In EMRs, the enzymes are retained in the reactor by a suitable membrane. Immobilization on carrier materials, and the associated losses in enzyme activity, can thus be avoided. Therefore, we validated the applicability of EMRs for the synthesis of natural and dihalogenated nucleosides, using one-pot transglycosylation reactions. Over a period of 55 days, 2'-deoxyadenosine was produced continuously, with a product yield >90%. The dihalogenated nucleoside analogues 2,6-dichloropurine-2'-deoxyribonucleoside and 6-chloro-2-fluoro-2'-deoxyribonucleoside were also produced, with high conversion, but for shorter operation times, of 14 and 5.5 days, respectively. The EMR performed with specific productivities comparable to batch reactions. However, in the EMR, 220, 40, and 9 times more product per enzymatic unit was produced, for 2'-deoxyadenosine, 2,6-dichloropurine-2'-deoxyribonucleoside, and 6-chloro-2-fluoro-2'-deoxyribonucleoside, respectively. The application of the EMR using freely dissolved enzymes, facilitates a continuous process with integrated biocatalyst separation, which reduces the overall cost of the biocatalyst and enhances the downstream processing of nucleoside production.

A Comprehensive Mini-review on COVID-19 Pathogenesis on Perspectives of Cytokine Storm and Recent Developments in Anti-Covid Nucleotide Analogues

The world has been rocked by the 2019 coronavirus disease (COVID-19), which has significantly changed our way of life. Despite the unusual measures taken, COVID-19 still exists and affects people all over the world. A remarkable amount of study has been done to find ways to combat the infection's unsurpassed level. No ground-breaking antiviral agent has yet been introduced to remove COVID-19 and bring about a return to normalcy, even though numerous pharmaceuticals and therapeutic technologies have been reused and discovered. The cytokine storm phenomenon is of utmost importance since fatality is strongly connected with the severity of the disease. This severe inflammatory phenomenon marked by increased amounts of inflammatory mediators can be targeted for saving patients' life. Our analysis demonstrates that SARS-CoV-2 specifically generates a lot of interleukin-6 (IL-6) and results in lymphocyte exhaustion. Tocilizumab is an IL-6 inhibitor that is currently thought to be both generally safe and effective. Additionally, corticosteroids, tumor necrosis factor (TNF)-blockers and Janus kinase (JAK) inhibitors could be effective and dependable methods to reduce cytokine-mediated storm in SARS-CoV-2 patients.Copyright © The Author(s) 2023.

Efficacy evaluation of quercetin and its analogues on the main protease enzyme of the COVID-19 using molecular docking studies

Introduction: COVID-19 is an acute respiratory infectious disease caused by the SARS-CoV-2 virus. There is an urgent need to discover antiviral drugs for better performance against new strains of coronaviruses (CoVs) due to the rapid spread of the disease despite scientific advances in vaccine development. This study aimed to evaluate the efficacy of quercetin and its analogues on the COVID-19 Mpro enzyme. Material & Methods: In this descriptive-analytical study, the three-dimensional structures of quercetin analogues (20 compounds), standard drugs (ritonavir and lopinavir), and the COVID-19 Mpro enzyme were obtained from PubChem and PDB databases for bioinformatics study, respectively. Molecular docking studies of the compounds on theMpro were performed using MOE-2014 software. Afterward, the physicochemical properties and biological activity of the compounds were predicted using Swiss ADME, PASS, and Swiss Target Prediction software. Findings: The findings of the present study showed that the most important bonds involved in drug-receptor binding are hydrogen, hydrophobic, and - interaction bonds. The best docking results were obtained for Baicalein, Genistein, Naringenin, and Quercetin compounds with strong binding energy (-12.83 to -13.54 kcal/mol), compared to ritonavir and lopinavir. These compounds have a greater tendency to bind to the catalytic amino acids His41 and Cys145 and other key amino acids of the active site of the COVID-19 Mpro enzyme. Discussion & Conclusion: Based on the results of bioinformatics studies, quercetin analogues had more effective inhibition than standard chemical drugs due to their suitable placement in the active site of the main protease enzyme of COVID-19 and can be good candidates for in vitro and in vivo studies.

Computational study for identifying promising therapeutic agents of hydroxychloroquine analogues against SARS-CoV-2.

Hydroxychloroquine (HCQ) and its derivatives have recently gained tremendous attention as a probable medicinal agent in the COVID-19 outbreak caused by SARS-CoV-2. An efficient agent to act directly in inhibiting the SARS-CoV-2 replication is yet to be achieved. Thus, the goal is to investigate the dynamic nature of HCQ derivatives against SARS-CoV-2 main protease and spike proteins. Molecular docking studies were also performed to understand their binding affinity in silico methods using the vital protein domains and enzymes involved in replicating and multiplying SARS-CoV-2, which were the main protease and spike protein. Molecular Dynamic simulations integrated with MM-PBSA calculations have identified In silico potential inhibitors ZINC05135012 and ZINC59378113 against the main protease with -185.171 ± 16.388, -130.759 ± 15.741 kJ/mol respectively, ZINC16638693 and ZINC59378113 against spike protein -141.425 ± 22.447, -129.149 ± 11.449 kJ/mol. Identified Hit molecules had demonstrated Drug Likeliness features, PASS values and ADMET predictions with no violations. Communicated by Ramaswamy H. Sarma.

Drug delivery improvements to enable a flexible care setting for monoclonal antibody medications in oncology - Analogue-based decision framework.

INTRODUCTION: The substantial acceleration in healthcare spending together with the expenditures to manage the COVID19 pandemic demand drug delivery solutions that enable a flexible care setting for high-dose monoclonal antibodies (mAbs) in oncology. AREAS COVERED: This expert opinion introduces an analogue-based framework applied to guide decision-making for associated product improvements for mAb medications that are either already authorized or in late-stage clinical development. The four pillars of this framework comprise (1) the drug delivery profile of current and emerging treatments in the market, (2) the needs and preferences of people treated with mAbs, (3) existing healthcare infrastructures, and (4) country-dependent reimbursement and procurement models. The following product optimization examples for mAb-based treatments are evaluated based on original research and review articles in the field: subcutaneous formulations, an established drug delivery modality to reduce parenteral dosing complexity, fixed-dose combinations, an emerging concept to complement combination therapy, and (connected) on-body delivery systems, an identified future opportunity to support dosing outside of a controlled healthcare institutional environment. EXPERT OPINION: Leveraging existing synergies and learnings from other disease areas is a measure to reduce associated development and commercialization costs and thus to provide sustainable product offerings already at the initial launch of a medication.

Elucidating the role of N440K mutation in SARS-CoV-2 spike - ACE-2 binding affinity and COVID-19 severity by virtual screening, molecular docking and dynamics approach.

COVID-19 has become a public health concern around the world. The frequency of N440K variant was higher during the second wave in South India. The mutation was observed in the Receptor Binding Domain region (RBD) of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) spike (S) protein. The binding affinity of SARS-CoV-2-Angiotensin-Converting Enzyme-2 (ACE-2) plays a major role in the transmission and severity of the disease. To understand the binding affinity of the wild and mutant SARS-CoV-2 S with ACE2, molecular modeling studies were carried out. We discovered that the wild SARS-CoV-2 S RBD-ACE-2 complex has a high binding affinity and stability than that of the mutant. The N440K strain escapes from antibody neutralization, which might increase reinfection and decrease vaccine efficiency. To find a potential inhibitor against mutant N440K SARS-CoV-2, a virtual screening process was carried out and found ZINC169293961, ZINC409421825 and ZINC22060839 as the best binding energy compounds. Communicated by Ramaswamy H. Sarma.

Masitinib analogues with the N-methylpiperazine group replaced - A new hope for the development of anti-COVID-19 drugs.

Masitinib is an orally acceptable tyrosine kinase inhibitor that is currently investigated under clinical trials against cancer, asthma, Alzheimer's disease, multiple sclerosis and amyotrophic lateral sclerosis. A recent study confirmed the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) activity of masitinib through inhibition of the main protease (Mpro) enzyme, an important pharmacological drug target to block the replication of the coronavirus. However, due to the adverse effects and lower potency of the drug, there are opportunities to design better analogues of masitinib. Herein, we substituted the N-methylpiperazine group of Masitinib with different chemical moieties and evaluated their drug-likeness and toxicities. The filtered analogues were subjected to molecular docking studies which revealed that the analogues with substituents methylamine in M10 (CID10409602), morpholine in M23 (CID59789397) and 4-methylmorpholine in M32 (CID143003625) have a stronger affinity to the drug receptor compared to masitinib. The molecular dynamics (MD) simulation analysis reveals that the identified analogues alter the mobility, structural compactness, accessibility to solvent molecules, and the number of hydrogen bonds in the native target enzyme. These structural alterations can help explain the inhibitory mechanisms of these analogues against the target enzyme. Thus, our studies provide avenues for the design of new masitinib analogues as the SARS-CoV-2 Mpro inhibitors.

Some natural compounds and their analogues having potent anti- SARS-CoV-2 and anti-proteases activities as lead molecules in drug discovery for COVID-19.

Currently an emerging human pathogenic coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), caused coronavirus disease 2019 (COVID-19) that has posed a serious threat to public health worldwide. As it is a novel severe pneumonia-type viral disease, no effective therapeutic agents are available to treat this infection to date, emphasizing an urgent need for development of effective anti-SARS-CoV-2 agents. Based on screening in computational biology and biological in vitro assays, a good number of natural compounds and their synthetic analogues have been confirmed to possess target-specific inhibitory effects against the activity of host and viral proteases, namely, cathepsin-L, TMPRSS2, Sec61, Mpro (3CL-protease), RNA-dependent RNA protease (RdRp), helicase cap-binding proteases eEF1A, eIF4A, eIF4E, which play dominant roles in progression of infection and replication of SARS-CoV-2 virus in host cells. This review paper describes the potent antiviral activity and target-specific anti-proteases activity of some natural compounds and their synthetic analogues against SARS-CoV-2 infection. It will inspire the researchers to unleash their own creativity and to design potent and safe drugs to fight the current COVID-19 pandemic.

Antiviral Effects of Heparan Sulfate Analogue-Modified Two-Dimensional MXene Nanocomposites on PRRSV and SARS-CoV-2.

Due to the worldwide impact of viruses such as SARS-CoV-2, researchers have paid extensive attention to antiviral reagents against viruses. Despite extensive research on two-dimensional (2D) transition metal carbides (MXenes) in the field of biomaterials, their antiviral effects have received little attention. In this work, heparan sulfate analogue (sodium 3-mercapto-1-propanesulfonate, MPS) modified 2D MXene nanocomposites (Ti3C2-Au-MPS) for prevention of viral infection are prepared and investigated using severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus and porcine reproductive and respiratory syndrome virus (PRRSV) as two model viruses. Ti3C2-Au-MPS nanocomposites are shown to possess antiviral properties in the different stages of PRRSV proliferation, such as direct interaction with PRRS virions and inhibiting their adsorption and penetration in the host cell. Additionally, Ti3C2-Au-MPS nanocomposites can strongly inhibit the infection of SARS-CoV-2 pseudovirus as shown by the contents of its reporter gene GFP and luciferase. These results demonstrate the potential broad-spectrum antiviral property of Ti3C2-Au-MPS nanocomposites against viruses with the receptor of heparin sulfate. This work sheds light on the specific antiviral effects of MXene-based nanocomposites against viruses and may facilitate further exploration of their antiviral applications.

Molnupiravir for the treatment of COVID-19.

Molnupiravir (MK-4482, EIDD-2801) is a promising broad-spectrum experimental antiviral developed by Merck & Co. It is a nucleoside analogue prodrug that undergoes rapid conversion into nucleoside triphosphate (NTP) by intracellular metabolic processes. NTP inhibits viral polymerase by acting as an alternative substrate. Molnupiravir was initially developed to treat influenza and Venezuelan equine encephalitis virus (VEEV) infection as it exerts its antiviral activity by inhibiting RNA-dependent RNA polymerase (RdRp). Currently, it is being developed for the treatment of SARS-CoV-2 infection. Molnupiravir has demonstrated potent in vitro antiviral activity against positive-sense RNA viruses including influenza viruses, SARS-CoV, SARS-CoV-2 and MERS-CoV with low cytotoxicity and a high resistance barrier. Molnupiravir has been evaluated in phase I, II and III trials where it has demonstrated good efficacy, dose-dependent pharmacokinetics and a sound safety profile. In an interim analysis of a phase III study, treatment with molnupiravir reduced the risk of hospitalization or death by 50% in patients with COVID-19; in the final analysis, the reduction was 30%. On the basis of positive results in clinical trials, molnupiravir has been authorized for emergency use by the U.K. Medicines and Healthcare products Regulatory Agency (MHRA) and the U.S. Food and Drug Administration (FDA) in adults with mild to moderate COVID-19.

Identifying Structural Features of Nucleotide Analogues to Overcome SARS-CoV-2 Exonuclease Activity.

With the recent global spread of new SARS-CoV-2 variants, there remains an urgent need to develop effective and variant-resistant oral drugs. Recently, we reported in vitro results validating the use of combination drugs targeting both the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) and proofreading exonuclease (ExoN) as potential COVID-19 therapeutics. For the nucleotide analogues to be efficient SARS-CoV-2 inhibitors, two properties are required: efficient incorporation by RdRp and substantial resistance to excision by ExoN. Here, we have selected and evaluated nucleotide analogues with a variety of structural features for resistance to ExoN removal when they are attached at the 3' RNA terminus. We found that dideoxynucleotides and other nucleotides lacking both 2'- and 3'-OH groups were most resistant to ExoN excision, whereas those possessing both 2'- and 3'-OH groups were efficiently removed. We also found that the 3'-OH group in the nucleotide analogues was more critical than the 2'-OH for excision by ExoN. Since the functionally important sequences in Nsp14/10 are highly conserved among all SARS-CoV-2 variants, these identified structural features of nucleotide analogues offer invaluable insights for designing effective RdRp inhibitors that can be simultaneously efficiently incorporated by the RdRp and substantially resist ExoN excision. Such newly developed RdRp terminators would be good candidates to evaluate their ability to inhibit SARS-CoV-2 in cell culture and animal models, perhaps combined with additional exonuclease inhibitors to increase their overall effectiveness.

Discovery of C-12 dithiocarbamate andrographolide analogues as inhibitors of SARS-CoV-2 main protease: In vitro and in silico studies.

A global crisis of coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has impacted millions of people's lives throughout the world. In parallel to vaccine development, identifying potential antiviral agents against SARS-CoV-2 has become an urgent need to combat COVID-19. One of the most attractive drug targets for discovering anti-SARS-CoV-2 agents is the main protease (Mpro), which plays a pivotal role in the viral life cycle. This study aimed to elucidate a series of twenty-one 12-dithiocarbamate-14-deoxyandrographolide analogues as SARS-CoV-2 Mpro inhibitors using in vitro and in silico studies. These compounds were initially screened for the inhibitory activity toward SARS-CoV-2 Mpro by in vitro enzyme-based assay. We found that compounds 3 k, 3 l, 3 m and 3 t showed promising inhibitory activity against SARS-CoV-2 Mpro with >50% inhibition at 10 µM. Afterward, the binding mode of each compound in the active site of SARS-CoV-2 Mpro was explored by molecular docking. The optimum docked complexes were then chosen and subjected to molecular dynamic (MD) simulations. The MD results suggested that all studied complexes were stable along the simulation time, and most of the compounds could fit well with the SARS-CoV-2 Mpro active site, particularly at S1, S2 and S4 subsites. The per-residue decomposition free energy calculations indicated that the hot-spot residues essential for ligand binding were T25, H41, C44, S46, M49, C145, H163, M165, E166, L167, D187, R188, Q189 and T190. Therefore, the obtained information from the combined experimental and computational techniques could lead to further optimization of more specific and potent andrographolide analogues toward SARS-CoV-2 Mpro.

The effect of the vaccine against viral pneumoenteritis left-pointing-double-angle Bolshevak right-pointing-double-angle on the metabolism of cows

The problem of viral pneumoenteritis of young farm animals is relevant for agriculture of the Republic of Belarus. Today, the most effective method of preventing viral pneumoenteritis of calves is vaccination of pregnant cows. In case of mixed infections, the most effective means of preventing such diseases are polyvalent vaccines. But biological preparations should have not only high preventive effectiveness, but also not affect the quality of the final product. The author of the article studied the effect of a polyvalent inactivated culture vaccine against infectious rhinotracheitis, viral diarrhea, parainfluenza-3, respiratory syncytial, rotavirus and coronavirus infection of cattle left-pointing-double-angle BolsheVak right-pointing-double-angle on the state of metabolism of pregnant cows. For this purpose, 3 groups of pregnant cows of the Belarusian black-and-white Holstein breed were formed in the conditions of the Agricultural Republican subsidiary of the Ulishitsy Agro enterprise of the Gorodok district on the principle of pairs of analogues with10 animals in each group for 1.5-2 months before calving. The cows of the first experimental group were immunized with the vaccine against viral pneumoenteritis "Bolshevak" with the adjuvant ISA-15 intramuscularly into the croup area in compliance with the rules of asepsis and antiseptics in the volume of 5.0 cm3. Cows of the second experimental group were immunized with the vaccine against viral pneumoenteritis "Bolshevak" with the adjuvant ISA-25 - in the volume of 3.0 cm3. The cows of the control group were injected with isotonic sodium chloride solution according to a similar scheme. The animals were immunized twice with an interval of 21 days. The sampling was carried out before the start of the studies, on the 14th, 21st days after the first vaccination and on the 45th day after the revaccination. The clinical condition of the animals was monitored for 70 days. As a result of the research, it was found that the studied vaccine against viral pneumoenteritis does not have a negative effect on the general condition of the animal, does not cause allergic reactions, abortions, does not inhibit the synthesis of the studied biochemical parameters of the serum.

Synthesis of N-(2,4-dinitrophenyl) derivatives of D-ribosylamines; unexpected reaction and hydrolysis products.

Reaction of 2,3-O-isopropylidene-d-ribofuranosylamine with 2,4-dinitrofluorobenzene afforded the crystalline 2,3-O-isopropylidene-N-(2,4-dinitrophenyl)-ß-d-ribofuranosylamine (3) and a 1:1 crystalline complex of 2,3-O-isopropylidene-N-(2,4-dinitrophenyl-α-d-ribofuranosylamine and 2,3-O-isopropylidene-ß-d-ribofuranose; controlled acidic hydrolysis of 3 afforded N-(2,4-dinitrophenyl-α-d-ribopyranosylamine and not the expected ß-d-furanosylamine derivative. The structures of the new compounds were confirmed by NMR spectroscopy and X-ray crystallography.

A Nanopore Based Molnupiravir Sensor.

Nucleoside analogues are reagents that resemble the structure of natural nucleosides and are widely applied in antiviral and anticancer therapy. Molnupiravir, a recently reported nucleoside analogue drug, has shown its inhibitory effect against SARS-CoV-2. Rapid tracing of molnupiravir and its metabolites is important in the evaluation of its pharmacology effect, but direct sensing of molnupiravir as a single molecule has not been reported to date. Here, we demonstrate a nanopore-based sensor with which direct sensing of molnupiravir and its two major metabolites ß-d-N4-hydroxycytidine and its triphosphate can be achieved simultaneously. In conjunction with a custom machine learning algorithm, an accuracy of 92% was achieved. This sensing strategy may be useful in the current pandemic and is in principle suitable for other nucleoside analogue drugs.

Efficacy of entecavir versus tenofovir disoproxil fumarate in treatment of chronic hepatitis B patients with high viral load. (Theme Issue: New advances in the precise diagnosis and treatment of liver cancer.) [Chinese]

Objective: To investigate the efficacy of entecavir (ETV) versus tenofovir disoproxil fumarate (TDF) and the treatment measures for poor response in previously untreated chronic hepatitis B (CHB) patients with high viral load.

Synthesis and antiplasmodial assessment of nitazoxanide and analogs as new antimalarial candidates.

During the last years, the progression to control malaria disease seems to be slowed and WHO (World Health Organization) reported a modeling analysis with the prediction of the increase in malaria morbidity and mortality in sub-Saharan Africa during the COVID-19 pandemic. A rapid way to the discovery of new drugs could be carried out by performing investigations to identify drugs based on repurposing of "old" drugs. The 5-nitrothiazole drug, Nitazoxanide was shown to be active against intestinal protozoa, human helminths, anaerobic bacteria, viruses, etc. In this work, Nitazoxanide and analogs were prepared using two methodologies and evaluated against P. falciparum 3D7. A bithiazole analog, showed attractive inhibitory activity with an EC50 value of 5.9 µM, low propensity to show toxic effect against HepG2 cells at 25 µM, and no cross-resistance with standard antimalarials.

Androgen-deprivation therapy and cognitive decline in the NEON-PC prospective study during the COVID-19 pandemic.

BACKGROUND: Androgen-deprivation therapy (ADT) has been associated with cognitive decline, but results are conflicting. This study describes changes in cognitive performance in patients with prostate cancer, according to ADT, during the first year after prostate cancer diagnosis. PATIENTS AND METHODS: Patients with prostate cancer treated at the Portuguese Institute of Oncology of Porto (n = 366) were evaluated with the Montreal Cognitive Assessment (MoCA), before treatment and after 1 year. All baseline evaluations were performed before the coronavirus disease 2019 (COVID-19) pandemic and 69.7% of the 1-year assessments were completed after the first lockdown. Cognitive decline was defined as the decrease in MoCA from baseline to the 1-year evaluation below 1.5 standard deviations of the distribution of changes in the whole cohort. Participants scoring below age- and education-specific normative reference values in the MoCA were considered to have cognitive impairment. Age- and education-adjusted odds ratios (aORs) were computed for the association between ADT and cognitive outcomes. RESULTS: Mean MoCA scores increased from baseline to the 1-year evaluation (22.3 versus 22.8, P < 0.001). Cognitive decline was more frequent in the ADT group, and even more after the onset of the COVID-19 pandemic (aOR 6.81 versus 1.93, P for interaction = 0.233). The 1-year cumulative incidence of cognitive impairment was 6.9% (9.1% before and 3.7% after the pandemic onset), which was higher among patients receiving ADT, but only after the pandemic (aOR 5.53 versus 0.49, P for interaction = 0.044). CONCLUSIONS: ADT was associated with worse cognitive performance of patients with prostate cancer, mostly among those evaluated after the first COVID-19 lockdown.

In vitro studies for BCS classification of an antiviral agent, favipiravir. (COVID-19 dedicated issue.)

Favipiravir (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) is a purine nucleic acid analog, which is an antiviral agent used in the treatment of influenza. Since the recent outbreak caused by 2019-novel coronavirus (nCoV), there has been a seek for effective antiviral agents to be used in the treatment of coronavirus disease 2019 (COVID-19), and favipiravir has been one of the options which provides a broad-spectrum therapy. Herein, we studied the aqueous solubility and in vitro permeability characteristics of favipiravir in order to shed light on the BCS classification of this antiviral agent used in COVID-19 therapy. The in vitro solubility was assessed using saturated solution of favipiravir in four different aqueous media and the solubility values were evaluated during 72 h at 37..C. The solubility of favipiravir was between 4.48 to 8.5 mg/ml, which is 5.85 to 10.63 times of calculated solubility limit. Caco-2 cell monolayers were utilized for the permeability assessment, and the drug solutions in three different concentrations including the highest dose required for bioequivalence exemption of the immediate release dosage form were applied. The effect of efflux transporters on the permeability of favipiravir was also determined using a P-gp inhibitor, Verapamil HCl. According to the data obtained from the in vitro studies, favipiravir can be considered as a representative of class I compound.