Favipiravir pharmacokinetics in Ebola-Infected patients of the JIKI trial reveals concentrations lower than targeted

Improving Ebola virus disease outbreak control through targeted post-exposure prophylaxis

Ebola virus disease kills more than half of people infected. Since the disease is transmitted via close human contact, identifying individuals at the highest risk of developing the disease is possible on the basis of the type of contact (correlated with viral exposure). Different candidates for post-exposure prophylaxis (PEP; ie, vaccines, antivirals, and monoclonal antibodies) each have their specific benefits and limitations, which we discuss in this Viewpoint. Approved monoclonal antibodies have been found to reduce mortality in people with Ebola virus disease. As monoclonal antibodies act swiftly by directly targeting the virus, they are promising candidates for targeted PEP in contacts at high risk of developing disease. This intervention could save lives, halt viral transmission, and, ultimately, help curtail outbreak propagation. We explore how a strategic integration of monoclonal antibodies and vaccines as PEP could provide both immediate and long-term protection against Ebola virus disease, highlighting ongoing clinical research that aims to refine this approach, and discuss the transformative potential of a successful PEP strategy to help control viral haemorrhagic fever outbreaks.

N-Substituted Pyrrole-Based Heterocycles as Broad-Spectrum Filoviral Entry Inhibitors

Since the largest and most fatal Ebola virus epidemic during 2014-2016, there have been several consecutive filoviral outbreaks in recent years, including those in 2021, 2022, and 2023. Ongoing outbreak prevalence and limited FDA-approved filoviral therapeutics emphasize the need for novel small molecule treatments. Here, we showcase the structure-activity relationship development of N-substituted pyrrole-based heterocycles and their potent, submicromolar entry inhibition against diverse filoviruses in a target-based pseudovirus assay. Inhibitor antiviral activity was validated using replication-competent Ebola, Sudan, and Marburg viruses. Mutational analysis was used to map the targeted region within the Ebola virus glycoprotein. Antiviral counter-screen and phospholipidosis assays were performed to demonstrate the reduced off-target activity of these filoviral entry inhibitors. Favorable antiviral potency, selectivity, and drug-like properties of the N-substituted pyrrole-based heterocycles support their potential as broad-spectrum antifiloviral treatments.

Oral Favipiravir Exposure and Pharmacodynamic Effects in Adult Outpatients With Acute Influenza

BACKGROUND

The pharmacokinetics of oral favipiravir and the relationships of plasma concentrations to antiviral effects are incompletely studied in influenza.

METHODS

Serial plasma samples were collected from adults with uncomplicated influenza who were randomized to favipiravir (1800 mg twice a day on day 1, 800 mg twice a day on days 2 to 5; n = 827) or placebo (n = 419) in 2 phase 3 trials. Post hoc analyses assessed the frequency of reaching an average minimum concentration (Cmin) ≥20 µg/mL, its association with antiviral efficacy, and factors associated with reduced favipiravir exposure.

RESULTS

Wide interindividual variability existed in favipiravir concentrations, and this regimen failed to reach an average Cmin>20 µg/mL in 41%-43% of participants. Those attaining this threshold showed greater reductions in nasopharyngeal infectious virus titers on treatment days 2 and 3 and lower viral titer area under the curve compared to those who did not. Those with average Cmin <20 µg/mL had over 2-fold higher mean ratios of the metabolite T-705M1 to favipiravir, consistent with greater metabolism, and were more likely to weigh >80 kg (61.5%-64%).

CONCLUSIONS

Higher favipiravir levels with average Cmin>20 µg/mL were associated with larger antiviral effects and more rapid illness alleviation compared to placebo and to favipiravir recipients with lower average Cmin values in uncomplicated influenza. Clinical Trials Registration . NCT1068912 and NCT01728753.

A novel LC-MS/MS method for the determination of favipiravir ribofuranosyl-5'-triphosphate (T-705-RTP) in human peripheral mononuclear cells

Favipiravir is a broad-spectrum antiviral that is metabolised intracellularly into the active form, favipiravir ribofuranosyl-5'-triphosphate (F-RTP). Measurement of the intracellular concentration of F-RTP in mononuclear cells is a crucial step to characterising the pharmacokinetics of F-RTP and to enable more appropriate dose selection for the treatment of COVID-19 and emerging infectious diseases. The described method was validated over the range 24 - 2280 pmol/sample. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and lysed using methanol-water (70:30, v/v) before cellular components were precipitated with acetonitrile and the supernatant further cleaned by weak anion exchange solid phase extraction. The method was found to be both precise and accurate and was successfully utilised to analyse F-RTP concentrations in patient samples collected as part of the AGILE CST-6 clinical trial.

Comparison of Routes of Administration, Frequency, and Duration of Favipiravir Treatment in Mouse and Guinea Pig Models of Ebola Virus Disease

Favipiravir is a ribonucleoside analogue that has been explored as a therapeutic for the treatment of Ebola Virus Disease (EVD). Promising data from rodent models has informed nonhuman primate trials, as well as evaluation in patients during the 2013-2016 West African EVD outbreak of favipiravir treatment. However, mixed results from these studies hindered regulatory approval of favipiravir for the indication of EVD. This study examined the influence of route of administration, duration of treatment, and treatment schedule of favipiravir in immune competent mouse and guinea pig models using rodent-adapted Zaire ebolavirus (EBOV). A dose of 300 mg/kg/day of favipiravir with an 8-day treatment was found to be fully effective at preventing lethal EVD-like disease in BALB/c mice regardless of route of administration (oral, intraperitoneal, or subcutaneous) or whether it was provided as a once-daily dose or a twice-daily split dose. Preclinical data generated in guinea pigs demonstrates that an 8-day treatment of 300 mg/kg/day of favipiravir reduces mortality following EBOV challenge regardless of route of treatment or duration of treatments for 8, 11, or 15 days. This work supports the future translational development of favipiravir as an EVD therapeutic.

Development of favipiravir dry powders for intranasal delivery: An integrated cocrystal and particle engineering approach via spray freeze drying

The therapeutic potential of pharmaceutical cocrystals in intranasal applications remains largely unexplored despite progressive advancements in cocrystal research. We present the application of spray freeze drying (SFD) in successful fabrication of a favipiravir-pyridinecarboxamide cocrystal nasal powder formulation for potential treatment of broad-spectrum antiviral infections. Preliminary screening via mechanochemistry revealed that favipiravir (FAV) can cocrystallize with isonicotinamide (INA), but not nicotinamide (NCT) and picolinamide (PIC) notwithstanding their structural similarity. The cocrystal formation was characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and unit cell determination through Rietveld refinement of powder X-ray analysis. FAV-INA crystalized in a monoclinic space group P21/c with a unit cell volume of 1223.54(3) Å3, accommodating one FAV molecule and one INA molecule in the asymmetric unit. The cocrystal was further reproduced as intranasal dry powders by SFD, of which the morphology, particle size, in vitro drug release, and nasal deposition were assessed. The non-porous flake shaped FAV-INA powders exhibited a mean particle size of 19.79 ± 2.61 μm, rendering its suitability for intranasal delivery. Compared with raw FAV, FAV-INA displayed a 3-fold higher cumulative fraction of drug permeated in Franz diffusion cells at 45 min (p = 0.001). Dose fraction of FAV-INA deposited in the nasal fraction of a customized 3D-printed nasal cast reached over 80 %, whereas the fine particle fraction remained below 6 % at a flow rate of 15 L/min, suggesting high nasal deposition whilst minimal lung deposition. FAV-INA was safe in RPMI 2650 nasal and SH-SY5Y neuroblastoma cells without any in vitro cytotoxicity observed. This study demonstrated that combining the merits of cocrystallization and particle engineering via SFD can propel the development of advanced dry powder formulations for intranasal drug delivery.

Oral administration of obeldesivir protects nonhuman primates against Sudan ebolavirus

Obeldesivir (ODV, GS-5245) is an orally administered prodrug of the parent nucleoside of remdesivir (RDV) and is presently in phase 3 trials for COVID-19 treatment. In this work, we show that ODV and its circulating parent nucleoside metabolite, GS-441524, have similar in vitro antiviral activity against filoviruses, including Marburg virus, Ebola virus, and Sudan virus (SUDV). We also report that once-daily oral ODV treatment of cynomolgus monkeys for 10 days beginning 24 hours after SUDV exposure confers 100% protection against lethal infection. Transcriptomics data show that ODV treatment delayed the onset of inflammation and correlated with antigen presentation and lymphocyte activation. Our results offer promise for the further development of ODV to control outbreaks of filovirus disease more rapidly.

Favipiravir induces HuNoV viral mutagenesis and infectivity loss with clinical improvement in immunocompromised patients

Chronic human norovirus (HuNoV) infections in immunocompromised patients result in severe disease, yet approved antivirals are lacking. RNA-dependent RNA polymerase (RdRp) inhibitors inducing viral mutagenesis display broad-spectrum in vitro antiviral activity, but clinical efficacy in HuNoV infections is anecdotal and the potential emergence of drug-resistant variants is concerning. Upon favipiravir (and nitazoxanide) treatment of four immunocompromised patients with life-threatening HuNoV infections, viral whole-genome sequencing showed accumulation of favipiravir-induced mutations which coincided with clinical improvement although treatment failed to clear HuNoV. Infection of zebrafish larvae demonstrated drug-associated loss of viral infectivity and favipiravir treatment showed efficacy despite occurrence of RdRp variants potentially causing favipiravir resistance. This indicates that within-host resistance evolution did not reverse loss of viral fitness caused by genome-wide accumulation of sequence changes. This off-label approach supports the use of mutagenic antivirals for treating prolonged RNA viral infections and further informs the debate surrounding their impact on virus evolution.

Prevention and post-exposure management of occupational exposure to Ebola virus

There have been significant advances in the prevention and management of Ebola virus disease (EVD) caused by Zaire Ebola virus (ZEBOV), including the development of two effective vaccines, rVSV-ZEBOV and Ad26.ZEBOV/MVA-BN-Filo. In addition, ZEBOV monoclonal antibodies have become first-line therapy for EVD. However, the 2022-23 outbreak of Sudan Ebola virus (SUDV) in Uganda has highlighted the gap in current therapies and vaccines, whose efficacy is uncertain against non-ZEBOV species. Health-care and laboratory staff working in EVD treatment centres or Ebola virus diagnostic and research laboratories face unique risks relating to potential occupational exposure to Ebola viruses. Given the substantial morbidity and mortality associated with EVD, facilities should have strategies in place to manage occupational exposures, including consideration of post-exposure therapies. In this Review, we discuss currently available evidence for prevention and post-exposure prophylaxis of EVD, including therapies currently under evaluation for SUDV.

Clinical antiviral efficacy of favipiravir in early COVID-19 (PLATCOV): an open-label, randomised, controlled, adaptive platform trial

In early symptomatic COVID-19 treatment, high dose oral favipiravir did not accelerate viral clearance.

BACKGROUND

Favipiravir, an anti-influenza drug, has in vitro antiviral activity against SARS-CoV-2. Clinical trial evidence to date is inconclusive. Favipiravir has been recommended for the treatment of COVID-19 in some countries.

METHODS

In a multicentre open-label, randomised, controlled, adaptive platform trial, low-risk adult patients with early symptomatic COVID-19 were randomised to one of ten treatment arms including high dose oral favipiravir (3.6g on day 0 followed by 1.6g daily to complete 7 days treatment) or no study drug. The primary outcome was the rate of viral clearance (derived under a linear mixed-effects model from the daily log10 viral densities in standardised duplicate oropharyngeal swab eluates taken daily over 8 days [18 swabs per patient]), assessed in a modified intention-to-treat population (mITT). The safety population included all patients who received at least one dose of the allocated intervention. This ongoing adaptive platform trial was registered at ClinicalTrials.gov (NCT05041907) on 13/09/2021.

RESULTS

In the final analysis, the mITT population contained data from 114 patients randomised to favipiravir and 126 patients randomised concurrently to no study drug. Under the linear mixed-effects model fitted to all oropharyngeal viral density estimates in the first 8 days from randomisation (4,318 swabs), there was no difference in the rate of viral clearance between patients given favipiravir and patients receiving no study drug; a -1% (95% credible interval: -14 to 14%) difference. High dose favipiravir was well-tolerated.

INTERPRETATION

Favipiravir does not accelerate viral clearance in early symptomatic COVID-19. The viral clearance rate estimated from quantitative measurements of oropharyngeal eluate viral densities assesses the antiviral efficacy of drugs in vivo with comparatively few studied patients.

Genetic consequences of effective and suboptimal dosing with mutagenic drugs in a hamster model of SARS-CoV-2 infection

Mutagenic antiviral drugs have shown promise against multiple viruses, but concerns have been raised about whether their use might promote the emergence of new and harmful viral variants. Recently, genetic signatures associated with molnupiravir use have been identified in the global SARS-COV-2 population. Here, we examine the consequences of using favipiravir and molnupiravir to treat SARS-CoV-2 infection in a hamster model, comparing viral genome sequence data collected from (1) untreated hamsters, and (2) from hamsters receiving effective and suboptimal doses of treatment. We identify a broadly linear relationship between drug dose and the extent of variation in treated viral populations, with a high proportion of this variation being composed of variants at frequencies of less than 1 per cent, below typical thresholds for variant calling. Treatment with an effective dose of antiviral drug was associated with a gain of between 7 and 10 variants per viral genome relative to drug-free controls: even after a short period of treatment a population founded by a transmitted virus could contain multiple sequence differences to that of the original host. Treatment with a suboptimal dose of drug showed intermediate gains of variants. No dose-dependent signal was identified in the numbers of single-nucleotide variants reaching frequencies in excess of 5 per cent. We did not find evidence to support the emergence of drug resistance or of novel immune phenotypes. Our study suggests that where onward transmission occurs, a short period of treatment with mutagenic drugs may be sufficient to generate a significant increase in the number of viral variants transmitted.

In vitro antiviral activity of favipiravir and its 6- and 3-O-substituted derivatives against coronavirus: Acetylation leads to improvement of antiviral activity

Favipiravir is currently approved for the treatment of the influenza virus and has shown encouraging results in terms of antiviral capacity in clinical studies against severe acute respiratory syndrome coronavirus 2. Favipiravir is a prodrug, where its favipiravir-ribofuranosyl-5B-triphosphate metabolite is capable of blocking RNA replication of the virus. However, the antiviral efficiency of favipiravir is limited by two factors: (i) low accumulation in plasma and rapid excretion/elimination post-administration and (ii) low conversion rate into the active metabolite. To tackle these problems, herein, we have designed new favipiravir analogues focusing on the replacement of the fluorine atom at the 6-position by halogen or hydrogen atoms and 3-O-functionalization with labile groups. The first type of functionalization seeks to increase the antiviral activity because of the better ability of the keto-tautomer as a function of the halogen, and it is hypothesized that the keto-tautomer tends to promote the formation of the ribofuranosyl-5B-triphosphate (RTP) metabolite. Meanwhile, the second type of functionalization seeks to promote lipophilicity and increase accumulation in cells. From the in vitro antiviral activity against two coronavirus models (bovine and human 229E), it was identified that the replacement did not improve the antiviral activity against both the models, which seems to be attributable to the low water solubility of these new 6-functionalized analogues. Meanwhile, with 3-O-functionalization, acetylation provided the most active compounds with higher half-maximal inhibitory concentration and selectivity than favipiravir, whereas benzylation/methanosulfonation yielded the least active compounds. In summary, acetylation is found to be a convenient functionalization to enhance the antiviral profile of favipiravir.

Multivariate Optimization for Determination of Favipiravir, a SARS-CoV-2 Molecule, by the Reverse-Phase Liquid Chromatographic Method Using a QbD Approach

The object of the analytical work is to develop an analytical multivariate optimization for the determination of Favipiravir (FAV), a SARS-CoV-2 molecule, by the reverse-phase liquid chromatographic method using the analytical quality by design approach. FAV is used as an antiviral drug. Box-Behnken design is utilized for the optimization of the experiment and to identify the critical method parameters like the volume of acetonitrile, temperature and flow rate. Further, these factors are used to design the suitable mathematical models and illustrate their effect on various responses. This newly developed method utilized C18 column (5μm, 100 × 4.6 mm) and a temperature of 40°C with a flow rate of 0.5 mL/min. The mobile phase is composed of acetonitrile and ammonium acetate buffer (pH 4), in the ratio of 20:80v/v and the wavelength of HPLC UV-Detector was fixed to 323nm. This method is validated according to International Council for Harmonization Q2 (R1) guidelines. The System suitability is performed and the retention time of Favipiravir is 3.4min. The linearity range is obtained at 0.062 - 4 μg/mL with a correlation coefficient (r2 = 0.9979). The recovery is found to be in the range of 98.84-100%. Thus, the intended method is found to be simple and robust.

Simultaneous quantitation of favipiravir and its hydroxide metabolite in human plasma and hamster matrices using a UPLC-MS/MS method

Favipiravir, a broad-spectrum RNA-dependent RNA polymerase inhibitor, is currently being evaluated in preclinical and clinical studies for the treatment of various infectious diseases including COVID-19. We developed an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay for the quantification of favipiravir and its hydroxide metabolite (M1), in human and hamster biological matrices. Analytes were separated on an Acquity UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm) after a simple protein precipitation with acetonitrile. The mobile phase consisted of water and methanol, each containing 0.05% formic acid. Experiments were performed using electrospray ionization in the positive and negative ion mode, with protonated molecules used as the precursor ion and a total run time of 6 min. The MS/MS response was linear over the concentration ranges from 0.5-100 μg/ml for favipiravir and 0.25-30 μg/ml for M1. Intra- and inter-day accuracy and precision were within the recommended limits of the European Medicines Agency guidelines. No significant matrix effect was observed, and the method was successfully applied to inform favipiravir dose adjustments in six immunocompromised children with severe RNA viral infections. In conclusion, the UPLC-MS/MS assay is suitable for quantification of favipiravir over a wide range of dosing regimens, and can easily be adapted to other matrices and species.

LC-MS/MS Method Development and Validation for Determination of Favipiravir Pure and Tablet Dosage Forms

Objectives

Analytical method development and validation for determination of favipiravir (FVPR) in pure and tablet dosage forms by liquid chromatography with tandem mass spectrometry/mass spectrometry (LC-MS/MS) technique.

Materials and Methods

A simple LC-MS/MS method was developed for determination of a new antiviral drug, FVPR in pharmaceutical formulations. The stationary phase employed was a Shim pack GISS, C18 (100 mm × 2.1 mm, 1.9 μm) column and mobile phase used in pump A was 10.0 mM ammonium acetate and in pump B methanol was used. The gradient program was used with fixed mobile phase flow rate at 0.4 mL min-1. Total run time was 5.0 min. The proposed method was validated according to International Conference on Harmonization (ICH) guidelines. The established method found better outcomes.

Results

The linearity graph was found in the range of 50-200 μg/mL and the correlation coefficient value (R2) obtained was found to be 1.0. The limit of detection (LOD) and limit of quantification (LOQ) were 4.044 μg/mL and 12.253 μg/mL, respectively. Tremendous recovery outcomes were observed and found to be 101%, 99.0%, and 99.5% for FVPR at 150% upper, 100% middle, and 50% lower concentrations, respectively.

Conclusion

All outcomes obtained comply with ICH guidelines. The developed method was simple, unique, accurate, robust, precise, and reproducible for determination of FVPR in tablet formulation. The method is novel and could be adopted in formulation industry.

Therapeutic strategies for COVID-19: progress and lessons learned

The coronavirus disease 2019 (COVID-19) pandemic has stimulated tremendous efforts to develop therapeutic strategies that target severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and/or human proteins to control viral infection, encompassing hundreds of potential drugs and thousands of patients in clinical trials. So far, a few small-molecule antiviral drugs (nirmatrelvir-ritonavir, remdesivir and molnupiravir) and 11 monoclonal antibodies have been marketed for the treatment of COVID-19, mostly requiring administration within 10 days of symptom onset. In addition, hospitalized patients with severe or critical COVID-19 may benefit from treatment with previously approved immunomodulatory drugs, including glucocorticoids such as dexamethasone, cytokine antagonists such as tocilizumab and Janus kinase inhibitors such as baricitinib. Here, we summarize progress with COVID-19 drug discovery, based on accumulated findings since the pandemic began and a comprehensive list of clinical and preclinical inhibitors with anti-coronavirus activities. We also discuss the lessons learned from COVID-19 and other infectious diseases with regard to drug repurposing strategies, pan-coronavirus drug targets, in vitro assays and animal models, and platform trial design for the development of therapeutics to tackle COVID-19, long COVID and pathogenic coronaviruses in future outbreaks.

Favipiravir Inhibits Zika Virus (ZIKV) Replication in HeLa Cells by Altering Viral Infectivity

This study aims to evaluate the antiviral potential of the nucleoside analogue favipiravir (FAV) against ZIKV, an arbovirus for which there are no approved antiviral therapies, in three human-derived cell lines. HeLa (cervical), SK-N-MC (neuronal), and HUH-7 (liver) cells were infected with ZIKV and exposed to different concentrations of FAV. Viral supernatant was sampled daily, and infectious viral burden was quantified by plaque assay. Changes in ZIKV infectivity were quantified by calculating specific infectivity. FAV-related toxicities were also assessed for each cell line in both infected and uninfected cells. Our results demonstrate that FAV activity was most pronounced in HeLa cells, as substantial declines in infectious titers and viral infectivity were observed in this cell type. The decline in infectious virus occurred in an exposure-dependent manner and was more pronounced as FAV exposure times increased. Additionally, toxicity studies showed that FAV was not toxic to any of the three cell lines and, surprisingly, caused substantial improvements in the viability of infected HeLa cells. Although SK-N-MC and HUH-7 cells were susceptible to FAV's anti-ZIKV activity, similar effects on viral infectivity and improvements in cell viability with therapy were not observed. These results indicate that FAV's ability to substantially alter viral infectivity is host cell specific and suggest that the robust antiviral effect observed in HeLa cells is mediated through drug-induced losses of viral infectivity.

Fabric phase sorptive extraction-gas chromatography-mass spectrometry for the determination of favipiravir in biological and forensic samples

Favipiravir, a pyrazine analog, is proposed as providential antiviral agent against the COVID-19 infection during 2020 pandemic emergency. For the first time, a fabric phase sorptive extraction (FPSE) combined with gas chromatography-mass spectrometry (GC-MS) has been developed and applied for the determination of favipiravir (FAV) in biological samples (human plasma, blood and urine), pharmaceutical and forensic samples. The method comprises of extraction of FAV by FPSE followed by its derivatization with N, O-bis (trimethylsilyl) trifluoroacetamide (BSTFA) and GC-MS analysis. Design of experiment-based optimization was performed using Placket-Burman Design (PBD) and Central Composite Design (CCD) for the screening of significant factors of FPSE and their optimization, respectively. Among all tested membranes, sol-gel polyethylene glycol (PEG) has offered the best extraction efficiency for FAV. Under optimum conditions, the proposed method was found to be linear in the range of 0.01–10 µg mL⁻¹ by GC-MS. The LODs and LOQs were as low as 0.001-0.0026 μg mL⁻¹ and 0.003-0.0086 μg mL⁻¹, respectively by GC-MS. Intra-day and inter-day precisions were less than 5 and 10 %, respectively, showing good method precision. The proposed method has been successfully applied to detect and quantify FAV in human urine, whole blood and plasma samples along with seized forensic samples. In addition, the proposed method has been evaluated for its green character by ComplexGAPI index.

Expanded profiling of Remdesivir as a broad-spectrum antiviral and low potential for interaction with other medications in vitro

Remdesivir (GS-5734; VEKLURY) is a single diastereomer monophosphoramidate prodrug of an adenosine analog (GS-441524). Remdesivir is taken up by target cells and metabolized in multiple steps to form the active nucleoside triphosphate (GS-443902), which acts as a potent inhibitor of viral RNA-dependent RNA polymerases. Remdesivir and GS-441524 have antiviral activity against multiple RNA viruses. Here, we expand the evaluation of remdesivir's antiviral activity to members of the families Flaviviridae, Picornaviridae, Filoviridae, Orthomyxoviridae, and Hepadnaviridae. Using cell-based assays, we show that remdesivir can inhibit infection of flaviviruses (such as dengue 1-4, West Nile, yellow fever, Zika viruses), picornaviruses (such as enterovirus and rhinovirus), and filoviruses (such as various Ebola, Marburg, and Sudan virus isolates, including novel geographic isolates), but is ineffective or is significantly less effective against orthomyxoviruses (influenza A and B viruses), or hepadnaviruses B, D, and E. In addition, remdesivir shows no antagonistic effect when combined with favipiravir, another broadly acting antiviral nucleoside analog, and has minimal interaction with a panel of concomitant medications. Our data further support remdesivir as a broad-spectrum antiviral agent that has the potential to address multiple unmet medical needs, including those related to antiviral pandemic preparedness.

Predicting the combined effects of case isolation, safe funeral practices, and contact tracing during Ebola virus disease outbreaks

BACKGROUND

The recent outbreaks of Ebola virus disease (EVD) in Uganda and the Marburg virus disease (MVD) in Ghana reflect a persisting threat of Filoviridae to the global health community. Characteristic of Filoviridae are not just their high case fatality rates, but also that corpses are highly contagious and prone to cause infections in the absence of appropriate precautions. Vaccines against the most virulent Ebolavirus species, the Zaire ebolavirus (ZEBOV) are approved. However, there exists no approved vaccine or treatment against the Sudan ebolavirus (SUDV) which causes the current outbreak of EVD. Hence, the control of the outbreak relies on case isolation, safe funeral practices, and contact tracing. So far, the effectiveness of these control measures was studied only separately by epidemiological models, while the impact of their interaction is unclear.

METHODS AND FINDINGS

To sustain decision making in public health-emergency management, we introduce a predictive model to study the interaction of case isolation, safe funeral practices, and contact tracing. The model is a complex extension of an SEIR-type model, and serves as an epidemic preparedness tool. The model considers different phases of the EVD infections, the possibility of infections being treated in isolation (if appropriately diagnosed), in hospital (if not properly diagnosed), or at home (if the infected do not present to hospital for whatever reason). It is assumed that the corpses of those who died in isolation are buried with proper safety measures, while those who die outside isolation might be buried unsafely, such that transmission can occur during the funeral. Furthermore, the contacts of individuals in isolation will be traced. Based on parameter estimates from the scientific literature, the model suggests that proper diagnosis and hence isolation of cases has the highest impact in reducing the size of the outbreak. However, the combination of case isolation and safe funeral practices alone are insufficient to fully contain the epidemic under plausible parameters. This changes if these measures are combined with contact tracing. In addition, shortening the time to successfully trace back contacts contribute substantially to contain the outbreak.

CONCLUSIONS

In the absence of an approved vaccine and treatment, EVD management by proper and fast diagnostics in combination with epidemic awareness are fundamental. Awareness will particularly facilitate contact tracing and safe funeral practices. Moreover, proper and fast diagnostics are a major determinant of case isolation. The model introduced here is not just applicable to EVD, but also to other viral hemorrhagic fevers such as the MVD or the Lassa fever.

New Analytical Methods for the Determination of New Anti-Viral Drug Favipiravir: A Potential Therapeutic Drug Against Covid-19 Virus, in Bulk and Dosage Forms

Simple, accurate and robust analytical methods have been developed and validated for the determination of favipiravir (FVPR) by RP-HPLC and UV spectroscopy techniques as per the ICH guidelines. In the RP-HPLC method for FVPR determination, the mobile phase was ammonium acetate buffer pH 6.5 in pump Aand methanol in pump B. The C18 (Sunfire) 5 μm, 4.6 × 250 mm column was used as a stationary phase, and the detection wavelength was at 323 nm. Under these conditions, FVPR was eluted as a sharp peak at 2.65 min and the overall time taken for each injection was 10 min. In case of the UV spectroscopy method, standard FVPR solutions were prepared with pure ethanol and scanned from 250 to 400 nm and a flourishing spectrum was obtained at 323 nm. Hence, the wavelength of 323 nm was fixed for the whole process of validation in both techniques. The limit of detection (LOD) and limit of quantification (LOQ) in the RP-HPLC method were 1.0 and 3.5 μg/mL, respectively, and the linearity was established in the 10 to 50 μg/mL range. In the UV spectroscopy method, the LOD and LOQ values were found to be 3.5 and 12 μg/mL, respectively, and the linearity was established within 20 to 60 μg/mL range. The regression coefficient was found to exceed 0.999 in both methods. The proposed RP-HPLC and UV spectroscopy techniques are simple, accurate, rugged and robust.

A Non-Instrumental Green Analytical Method Based on Surfactant-Assisted Dispersive Liquid-Liquid Microextraction-Thin-Layer Chromatography-Smartphone-Based Digital Image Colorimetry(SA-DLLME-TLC-SDIC) for Determining Favipiravir in Biological Samples

Favipiravir (FAV) has become a promising antiviral agent for the treatment of COVID-19. Herein, a green, fast, high-sample-throughput, non-instrumental, and affordable analytical method is proposed based on surfactant-assisted dispersive liquid-liquid microextraction (SA-DLLME) combined with thin-layer chromatography-digital image colourimetry (TLC-DIC) for determining favipiravir in biological and pharmaceutical samples. Triton X-100 and dichloromethane (DCM) were used as the disperser and extraction solvents, respectively. The extract obtained after DLLME procedure was spotted on a TLC plate and allowed to develop with a mobile phase of chloroform:methanol (8:2, v/v). The developed plate was photographed using a smartphone under UV irradiation at 254 nm. The quantification of FAV was performed by analysing the digital images' spots with open-source ImageJ software. Multivariate optimisation using Plackett-Burman design (PBD) and central composite design (CCD) was performed for the screening and optimisation of significant factors. Under the optimised conditions, the method was found to be linear, ranging from 5 to 100 µg/spot, with a correlation coefficient (R2) ranging from 0.991 to 0.994. The limit of detection (LOD) and limit of quantification (LOQ) were in the ranges of 1.2-1.5 µg/spot and 3.96-4.29 µg/spot, respectively. The developed approach was successfully applied for the determination of FAV in biological (i.e., human urine and plasma) and pharmaceutical samples. The results obtained using the proposed methodology were compared to those obtained using HPLC-UV analysis and found to be in close agreement with one another. Additionally, the green character of the developed method with previously reported protocols was evaluated using the ComplexGAPI, AGREE, and Eco-Scale greenness assessment tools. The proposed method is green in nature and does not require any sophisticated high-end analytical instruments, and it can therefore be routinely applied for the analysis of FAV in various resource-limited laboratories during the COVID-19 pandemic.

Pharmacokinetic Comparison of Favipiravir Oral Solution and Tablet Formulations in Healthy Thai Volunteers

This study compared the pharmacokinetics and safety of favipiravir oral solution with those of tablet formulations, which were agents repurposed to treat nonsevere coronavirus disease 2019 in Thailand. In an open-label, single-dose, randomized, crossover study, 24 healthy subjects under fasting conditions were randomly assigned to a single dose of 200 mg of favipiravir, either as an oral solution of 200 mg/15 mL (test product) or a tablet (reference product), separated by a 7-day washout period. Fifteen plasma samples were collected over 12 hours after drug administration. Plasma favipiravir levels were quantified using in-house developed ultra-high-performance liquid chromatography-tandem mass spectrometry. The test/reference geometric mean ratio along with 90%CI for the maximum plasma concentration, area under the concentration-time curve (AUC) to the time of the last quantifiable concentration, and AUC after single-dose administration, extrapolated to infinity were 115.3% (90%CI, 107.7%-123.3%), 100.4% (90%CI, 96.9%-104.0%), and 100.4% (90%CI, 96.8%-104.2%), respectively. These results were within the predefined acceptance criteria for bioequivalence (80.0%-125.0%). No adverse events were observed in either group. The oral solution formulation could offer the advantage of easier swallowing in broader patient groups.

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.

The effect of Favipiravir on liver enzyme among patients with mild to moderate COVID-19 infection: A prospective cohort study

Teratogenicity and hyperuricemia are considered as the major adverse effects of favipiravir, but less is known about other possible side effects which includes drug-induced liver damage and renal injury. In the current research, assessment of favipiravir-induced liver injury was performed by evaluating liver enzymes among patients with mild to moderate COVID-19 infection. A prospective cohort study was conducted on 66 patients diagnosed with mild to moderate COVID-19 infection who were treated with favipiravir for 5 days. During this period, a baseline assessment of liver enzymes (aspartate aminotransferase - AST, alanine transaminase - ALT and alkaline phosphatase - ALP) in addition to bilirubin before initiation of therapy and after 1 day of completion of therapy were carried out. The comparison of all measured parameters among all patients before and after receiving the treatment showed that non-significant differences were obtained in their levels. It was noticed that COVID-19 patients demonstrated high AST levels in which only 16 patients out of the all-subjected cases (66 patients) had AST levels of less than 45 U/L whereas the majority of patients showed normal ALT, ALP, and bilirubin levels. It was concluded that 5 days administration of favipiravir in mild to moderate COVID-19 patients who had no previous liver diseases did not affect the liver enzymes significantly and only transient elevations were occurred.

Hydrophobic Rose Bengal Derivatives Exhibit Submicromolar-to-Subnanomolar Activity against Enveloped Viruses

Rose Bengal (RB) is an anionic xanthene dye with multiple useful biological features, including photosensitization properties. RB was studied extensively as a photosensitizer, mostly for antibacterial and antitumor photodynamic therapy (PDT). The application of RB to virus inactivation is rather understudied, and no RB derivatives have been developed as antivirals. In this work, we used a synthetic approach based on a successful design of photosensitizing antivirals to produce RB derivatives for virus photoinactivation. A series of n-alkyl-substituted RB derivatives was synthesized and evaluated as antiviral photosensitizers. The compounds exhibited similar 1O2 generation rate and efficiency, but drastically different activities against SARS-CoV-2, CHIKV, and HIV; with comparable cytotoxicity for different cell lines. Submicromolar-to-subnanomolar activities and high selectivity indices were detected for compounds with C4-6 alkyl (SARS-CoV-2) and C6-8 alkyl (CHIKV) chains. Spectrophotometric assessment demonstrates low aqueous solubility for C8-10 congeners and a significant aggregation tendency for the C12 derivative, possibly influencing its antiviral efficacy. Initial evaluation of the synthesized compounds makes them promising for further study as viral inactivators for vaccine preparations.

Development and Validation of HPLC-DAD Method for the Determination of Favipiravir and Studying the Impact of Vitamin C on the Pharmacokinetics of COVID-19 Antiviral Drug Favipiravir

A novel, sensitive, and low-cost HPLC method for the rapid determination of favipiravir (FVR) in rat plasma was developed and validated, and the effect of vitamin C on FVR pharmacokinetic parameters was investigated. FVR and oxcarbazepine (IS) were separated using a mobile phase of 50% acetonitrile and 50% water (with 0.25% trifluoroacetic acid) at 1.0 mL/min flow rate and detected at λmax 289 nm. The intra- and interday values for FVR in plasma were less than 15%, with low, medium, and high QC levels for the relative recovery rate, according to ICH guidelines. Cmax values in the control and experimental groups were 558 ± 124.42 and 979.13 ± 138.10 ng/mL, respectively; t1/2 values were 7.15 ± 1.60 and 9.09 ± 1.14 h, AUC(0-t) values were 5697.70 ± 536.58 and 7381.62 ± 1577.58 ng.h/mL, and AUC(0-∞) values were 5697.70 ± 536.58 and 8192.36 ±  1721.67, respectively. According to the results, the experimental group’s Cmax of FVR was 75.17% higher than the control group’s, the Vz/F was lower, and the t1/2 was 1.86 h longer. The technique developed for determining FVR in plasma was useful for FVR pharmacokinetics and food–drug interaction investigations.

Favipiravir, lopinavir-ritonavir, or combination therapy (FLARE): A randomised, double-blind, 2 × 2 factorial placebo-controlled trial of early antiviral therapy in COVID-19

BACKGROUND

Early antiviral treatment is effective for Coronavirus Disease 2019 (COVID-19) but currently available agents are expensive. Favipiravir is routinely used in many countries, but efficacy is unproven. Antiviral combinations have not been systematically studied. We aimed to evaluate the effect of favipiravir, lopinavir-ritonavir or the combination of both agents on Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) viral load trajectory when administered early.

METHODS AND FINDINGS

We conducted a Phase 2, proof of principle, randomised, placebo-controlled, 2 × 2 factorial, double-blind trial of ambulatory outpatients with early COVID-19 (within 7 days of symptom onset) at 2 sites in the United Kingdom. Participants were randomised using a centralised online process to receive: favipiravir (1,800 mg twice daily on Day 1 followed by 400 mg 4 times daily on Days 2 to 7) plus lopinavir-ritonavir (400 mg/100 mg twice daily on Day 1, followed by 200 mg/50 mg 4 times daily on Days 2 to 7), favipiravir plus lopinavir-ritonavir placebo, lopinavir-ritonavir plus favipiravir placebo, or both placebos. The primary outcome was SARS-CoV-2 viral load at Day 5, accounting for baseline viral load. Between 6 October 2020 and 4 November 2021, we recruited 240 participants. For the favipiravir+lopinavir-ritonavir, favipiravir+placebo, lopinavir-ritonavir+placebo, and placebo-only arms, we recruited 61, 59, 60, and 60 participants and analysed 55, 56, 55, and 58 participants, respectively, who provided viral load measures at Day 1 and Day 5. In the primary analysis, the mean viral load in the favipiravir+placebo arm had changed by -0.57 log10 (95% CI -1.21 to 0.07, p = 0.08) and in the lopinavir-ritonavir+placebo arm by -0.18 log10 (95% CI -0.82 to 0.46, p = 0.58) compared to the placebo arm at Day 5. There was no significant interaction between favipiravir and lopinavir-ritonavir (interaction coefficient term: 0.59 log10, 95% CI -0.32 to 1.50, p = 0.20). More participants had undetectable virus at Day 5 in the favipiravir+placebo arm compared to placebo only (46.3% versus 26.9%, odds ratio (OR): 2.47, 95% CI 1.08 to 5.65; p = 0.03). Adverse events were observed more frequently with lopinavir-ritonavir, mainly gastrointestinal disturbance. Favipiravir drug levels were lower in the combination arm than the favipiravir monotherapy arm, possibly due to poor absorption. The major limitation was that the study population was relatively young and healthy compared to those most affected by the COVID-19 pandemic.

CONCLUSIONS

At the current doses, no treatment significantly reduced viral load in the primary analysis. Favipiravir requires further evaluation with consideration of dose escalation. Lopinavir-ritonavir administration was associated with lower plasma favipiravir concentrations.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04499677 EudraCT: 2020-002106-68.

Cationic Perylene Antivirals with Aqueous Solubility for Studies In Vivo

Perylene-based compounds are attracting significant attention due to their high broad-spectrum antiviral activity against enveloped viruses. Despite unambiguous results of in vitro studies and high selectivity index, the poor water solubility of these compounds prevented in vivo evaluation of their antiviral properties. In this work, we synthesized a series of compounds with a perylene pharmacophore bearing positively charged substituents to improve the aqueous solubility of this unique type of antivirals. Three types of charged groups were introduced: (1) quaternary morpholinium salts (3a-b); (2) a 2'-O-l-valinyl-uridine hydrochloride residue (8), and (3) a 3-methylbenzothiazolium cation (10). The synthesized compounds were evaluated based both on antiviral properties in vitro (CHIKV, SARS-CoV-2, and IAV) and on solubility in aqueous media. Compound 10 has the greatest aqueous solubility, making it preferable for pre-evaluation by intragastrical administration in a mouse model of lethal influenza pneumonia. The results indicate that the introduction of a positively charged group is a viable strategy for the design of drug candidates with a perylene scaffold for in vivo studies.

Antiviral efficacy of favipiravir against Zika and SARS-CoV-2 viruses in non-human primates

The COVID-19 pandemic has exemplified that rigorous evaluation in large animal models is key for translation from promising in vitro results to successful clinical implementation. Among the drugs that have been largely tested in clinical trials but failed so far to bring clear evidence of clinical efficacy is favipiravir, a nucleoside analogue with large spectrum activity against several RNA viruses in vitro and in small animal models. Here, we evaluate the antiviral activity of favipiravir against Zika or SARS-CoV-2 virus in cynomolgus macaques. In both models, high doses of favipiravir are initiated before infection and viral kinetics are evaluated during 7 to 15 days after infection. Favipiravir leads to a statistically significant reduction in plasma Zika viral load compared to untreated animals. However, favipiravir has no effects on SARS-CoV-2 viral kinetics, and 4 treated animals have to be euthanized due to rapid clinical deterioration, suggesting a potential role of favipiravir in disease worsening in SARS-CoV-2 infected animals. To summarize, favipiravir has an antiviral activity against Zika virus but not against SARS-CoV-2 infection in the cynomolgus macaque model. Our results support the clinical evaluation of favipiravir against Zika virus but they advocate against its use against SARS-CoV-2 infection.

Repurposed antiviral drugs present as a valuable resource in the defence during outbreaks, with rigorous evaluation in large animal models keys for translation to clinical implementation. Here, the authors explore the antiviral activity of favipiravir against Zika virus and SARS-CoV-2 in cynomolgus macaques, in order to support future clinical investigations into this RNA polymerase inhibitor.

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.

Real-World Effectiveness and Optimal Dosage of Favipiravir for Treatment of COVID-19: Results from a Multicenter Observational Study in Thailand

Favipiravir is a broad-spectrum oral antiviral agent that shows in vitro activity against SARS-CoV-2. Presently, data on the real-world effectiveness and optimal dosage of favipiravir for treating COVID-19 are limited. We conducted a retrospective observational study of hospitalized adult patients with COVID-19 at five tertiary care hospitals in Thailand. We reviewed patient charts to obtain all necessary data. Among 247 COVID-19 patients, 63 (23.0%) received ≥1 dose of favipiravir. Of these 63 patients, 61.9% were male with a median age of 48 years (range 22–85 years), 27.0% required an O₂ nasal cannula, 9.5% required non-invasive ventilation and/or high-flow O₂ therapy, and 6.4% required invasive mechanical ventilation and/or ECMO. The median baseline NEWS2 score was 5 (0–16). The Day-7 clinical improvement rate [95%CI] was 66.7% [53.7–78.0%] in all patients, 92.5% [75.7–99.1%] in patients who did not require O₂ supplementation, and 47.2% [0.4–64.5%] in patients who required O₂ supplementation. No life-threatening adverse events were identified. The 28-day mortality rate was 4.8%. A multivariate analysis revealed three poor prognostic factors for Day-7 clinical improvement (odds ratio (95%CI); p-value): older age (0.94 (0.89–0.99); p = 0.04), a higher baseline NEWS2 score (0.64 (0.47–0.88); p = 0.006), and a lower favipiravir loading dose (≤45 mg/kg/day) (0.04 (0.005–0.4); p = 0.006). In conclusion, our study reports the promising effectiveness of favipiravir for treating COVID-19 patients. In addition to older age and a high baseline NEWS2 score, a low loading dose of favipiravir (≤45 mg/kg/day) was also identified as a poor prognostic factor for early clinical improvement. Further studies to explore the optimal dose and the optimal timing of drug initiation for favipiravir should be performed.

Analytical Performance and Greenness Evaluation of Five Multi-Level Design Models Utilized for Impurity Profiling of Favipiravir, a Promising COVID-19 Antiviral Drug

In 2018, the discovery of carcinogenic nitrosamine process related impurities (PRIs) in a group of widely used drugs led to the recall and complete withdrawal of several medications that were consumed for a long time, unaware of the presence of these genotoxic PRIs. Since then, PRIs that arise during the manufacturing process of the active pharmaceutical ingredients (APIs), together with their degradation impurities, have gained the attention of analytical chemistry researchers. In 2020, favipiravir (FVR) was found to have an effective antiviral activity against the SARS-COVID-19 virus. Therefore, it was included in the COVID-19 treatment protocols and was consequently globally manufactured at large-scales during the pandemic. There is information indigence about FVR impurity profiling, and until now, no method has been reported for the simultaneous determination of FVR together with its PRIs. In this study, five advanced multi-level design models were developed and validated for the simultaneous determination of FVR and two PRIs, namely; (6-chloro-3-hydroxypyrazine-2-carboxamide) and (3,6-dichloro-pyrazine-2-carbonitrile). The five developed models were classical least square (CLS), principal component regression (PCR), partial least squares (PLS), genetic algorithm-partial least squares (GA-PLS), and artificial neural networks (ANN). Five concentration levels of each compound, chosen according to the linearity range of the target analytes, were used to construct a five-level, three-factor chemometric design, giving rise to twenty-five mixtures. The models resolved the strong spectral overlap in the UV-spectra of the FVR and its PRIs. The PCR and PLS models exhibited the best performances, while PLS proved the highest sensitivity relative to the other models.

Highly sensitive high-performance thin-layer chromatography method for the simultaneous determination of Molnupiravir, Favipiravir, and Ritonavir in pure forms and pharmaceutical formulations

Favipiravir, molnupiravir, and ritonavir have been recently approved as the first oral antivirals for treatment of SARS-CoV-2 viral infections. Their combination was reported in several clinical studies, alternatively, to enhance the viral eradication and improve patient's recovery times and rates. Being all orally administered, therefore, developing new sensitive and validated methodologies for their simultaneous determination is a necessitate. In the proposed research, a sensitive, selective and simple high-performance thin layer chromatography method was developed and validated for determination of favipiravir, molnupiravir, and ritonavir. Silica gel 60F254 thin layer chromatography plates were used as stationary phase for this separation using mobile phase composed of methylene chloride: ethyl acetate: methanol: 25% ammonia (6:3:4:1, v/v/v/v). Densitometric detection was performed at wavelength 289nm. Peaks of favipiravir, molnupiravir, and ritonavir were resolved at retention factors 0.22, 0.42 and 0.63, respectively. The proposed method was found linear within the specified ranges of 3.75-100.00 μg/mL for molnupiravir and favipiravir, and 2.75-100.00 μg/mL for ritonavir. Limits of detection were found to be 1.12, 1.21, and 0.89 μg/mL for favipiravir, molnupiravir, and ritonavir, respectively. This is the first method to be reported for the simultaneous determination of the cited three antiviral drugs. The method was assessed on novel greenness metrics. This article is protected by copyright. All rights reserved.

Anti-infective Medicines Use in Children and Neonates With Pre-existing Kidney Dysfunction: A Systematic Review

Background

Dosing recommendations for anti-infective medicines in children with pre-existing kidney dysfunction are derived from adult pharmacokinetics studies and adjusted to kidney function. Due to neonatal/pediatric age and kidney impairment, modifications in renal clearance and drug metabolism make standard anti-infective dosing for children and neonates inappropriate, with a risk of drug toxicity or significant underdosing. The aim of this study was the systematic description of the use of anti-infective medicines in pediatric patients with pre-existing kidney impairment.

Methods

A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The EMBASE, Medline and Cochrane databases were searched on September 21st, 2021. Studies in all languages reporting data on pre-defined outcomes (pharmacokinetics-PK, kidney function, safety and efficacy) regarding the administration of anti-infective drugs in children up to 18 years with pre-existing kidney dysfunction were included.

Results

29 of 1,792 articles were eligible for inclusion. There were 13 case reports, six retrospective studies, nine prospective studies and one randomized controlled trial (RCT), reporting data on 2,168 pediatric patients. The most represented anti-infective class was glycopeptides, with seven studies on vancomycin, followed by carbapenems, with five studies, mostly on meropenem. Antivirals, aminoglycosides and antifungals counted three articles, followed by combined antibiotic therapy, cephalosporins, lipopeptides with two studies, respectively. Penicillins and polymixins counted one study each. Nine studies reported data on patients with a decreased kidney function, while 20 studies included data on kidney replacement therapy (KRT). Twenty-one studies reported data on PK. In 23 studies, clinical outcomes were reported. Clinical cure was achieved in 229/242 patients. There were four cases of underdosing, one case of overdosing and 13 reported deaths.

Conclusion

This is the first systematic review providing evidence of the use of anti-infective medicines in pediatric patients with impaired kidney function or requiring KRT. Dosing size or interval adjustments in pediatric patients with kidney impairment vary according to age, critical illness status, decreased kidney function and dialysis type. Our findings underline the relevance of population PK in clinical practice and the need of developing predictive specific models for critical pediatric patients.

Two Green Micellar HPLC and Mathematically Assisted UV Spectroscopic Methods for the Simultaneous Determination of Molnupiravir and Favipiravir as a Novel Combined COVID-19 Antiviral Regimen

Following the spread of the COVID-19 pandemic crisis, a race was initiated to find a successful regimen for postinfections. Among those trials, a recent study declared the efficacy of an antiviral combination of favipiravir (FAV) and molnupiravir (MLP). The combined regimen helped in a successful 60% eradication of the SARS-CoV-2 virus from the lungs of studied hamster models. Moreover, it prevented viral transmission to cohosted sentinels. Because both medications are orally bioavailable, the coformulation of FAV and MLP can be predicted. The developed study is aimed at developing new green and simple methods for the simultaneous determination of FAV and MLP and then at their application in the study of their dissolution behavior if coformulated together. A green micellar HPLC method was validated using an RP-C18 core-shell column (5 μm, 150 × 4.6 mm) and an isocratic mixed micellar mobile phase composed of 0.1 M SDS, 0.01 M Brij-35, and 0.02 M monobasic potassium phosphate mixture and adjusted to pH 3.1 at 1.0 mL min-1 flow rate. The analytes were detected at 230 nm. The run time was less than five minutes under the optimized chromatographic conditions. Four other multivariate chemometric model methods were developed and validated, namely, classical least square (CLS), principal component regression (PCR), partial least squares (PLS-1), and genetic algorithm-partial least squares (GA-PLS-1). The developed models succeeded in resolving the great similarity and overlapping in the FAV and MLP UV spectra unlike the traditional univariate methods. All methods were organic solvent-free, did not require extraction or derivatization steps, and were applied for the construction of the simultaneous dissolution profile for FAV tablets and MLP capsules. The methods revealed that the amount of the simultaneously released cited drugs increases up until reaching a plateau after 15 and 20 min for FAV and MLP, respectively. The greenness was assessed on GAPI and found to be in harmony with green analytical chemistry concepts.

Favipiravir in the Battle with Respiratory Viruses

Abstract:

Among antiviral drugs, the vast majority targets only one or two related viruses. The conventional model, one virus - one drug, significantly limits therapeutic options. Therefore, in the strategy of controlling viral infections, there is a necessity to develop compounds with pleiotropic effects. Favipiravir (FPV) emerged as a strong candidate to become such a drug. The aim of the study is to present up-to-date information on the role of favipiravir in the treatment of viral respiratory infections. The anti-influenza activity of favipiravir has been confirmed in cell culture experiments, animal models and clinical trials. Thoroughly different - from the previously registered drugs - mechanism of action suggests that FVP can be used as a countermeasure for the novel or re-emerging influenza virus infections. In recent months, favipiravir has been broadly investigated due to its potential efficacy in the treatment of Covid-19. Based on preclinical and clinical studies and a recently published meta-analysis it seems that favipiravir may be a promising antiviral drug in the treatment of patients with Covid-19. FPV is also effective against other RNA respiratory viruses and may be a candidate for the treatment of serious infections caused by human rhinovirus, respiratory syncytial virus, metapneumovirus, parainfluenza viruses and hantavirus pulmonary syndrome.

Rational Development of a Carrier-Free Dry Powder Inhalation Formulation for Respiratory Viral Infections via Quality by Design: A Drug-Drug Cocrystal of Favipiravir and Theophylline

Formulating pharmaceutical cocrystals as inhalable dosage forms represents a unique niche in effective management of respiratory infections. Favipiravir, a broad-spectrum antiviral drug with potential pharmacological activity against SARS-CoV-2, exhibits a low aqueous solubility. An ultra-high oral dose is essential, causing low patient compliance. This study reports a Quality-by-Design (QbD)-guided development of a carrier-free inhalable dry powder formulation containing a 1:1 favipiravir-theophylline (FAV-THP) cocrystal via spray drying, which may provide an alternative treatment strategy for individuals with concomitant influenza infections and chronic obstructive pulmonary disease/asthma. The cocrystal formation was confirmed by single crystal X-ray diffraction, powder X-ray diffraction, and the construction of a temperature-composition phase diagram. A three-factor, two-level, full factorial design was employed to produce the optimized formulation and study the impact of critical processing parameters on the resulting median mass aerodynamic diameter (MMAD), fine particle fraction (FPF), and crystallinity of the spray-dried FAV-THP cocrystal. In general, a lower solute concentration and feed pump rate resulted in a smaller MMAD with a higher FPF. The optimized formulation (F1) demonstrated an MMAD of 2.93 μm and an FPF of 79.3%, suitable for deep lung delivery with no in vitro cytotoxicity observed in A549 cells.

Pharmacokinetic characterization of favipiravir in patients with COVID-19

This prospective observational study describes the pharmacokinetic characteristics of favipiravir in adult patients hospitalized for mild to moderate COVID-19 with a positive RT-PCR test. Favipiravir was administered for 5 days, with a loading dose of 3200 mg and a maintenance dose of 1200 mg/day. Serial blood samples were collected on Day-2 and Day-4 of the therapy. Laboratory findings of the patients (n=21) and in-hospital mortality were recorded. Favipiravir concentrations exhibited substantial variability and a significant decrease during the treatment of COVID-19. The median favipiravir trough concentration (C_0-trough ) on Day-2 was 21.26 (IQR, 8.37-30.78) μg/mL whereas it decreased significantly to 1.61 (IQR, 0.00-6.41) μg/mL on Day-4, the area under the concentration versus time curve decreased by 68.5%. Day-2-C_0-trough of female patients was higher than male patients. Our findings indicate that favipiravir concentrations show significant variability during the treatment of COVID-19 and therapeutic drug monitoring may be necessary to maintain targeted concentrations.

Full title: High doses of favipiravir in two men survivors of Ebola virus disease carrying Ebola virus in semen in Guinea

Background

Persistence of Ebola virus (EBOV) in semen remains of deep concern, as sexual transmission of EBOV seems plausible up to 6 months after acute phase of Ebola virus disease (EVD). Favipiravir, a broad spectrum antiviral product, has been evaluated in reducing EVD mortality in Guinea in 2014–2015 in the JIKI trial, the pharmacokinetic results of which suggest that an increase of dose might be necessary to achieve a therapeutically relevant exposure. In FORCE trial, we aimed at evaluating the tolerance and activity of high doses of favipiravir in male EVD survivors with EBOV RNA detection in semen in Guinea.

Case

In 2016, we launched a phase IIa open-labeled multicenter dose escalation study. Male survivors of EVD with EBOV RT-PCR positive on semen received a loading dose of 2400 mg BID of favipiravir on day 1 then a maintenance dose of 1800 mg BID from day 2–14. The primary outcome was the tolerance, assessed daily during period treatment and up to day 90. Unfortunately only two participants were included and the trial was stopped for lack of recruitment. No clinical adverse event of grade 3/4 was reported for both patients. One patient experienced a grade 3 hypocalcemia at day 10 and 14.

Conclusions

High doses of favipiravir were well tolerated in these two participants. Better characterized tolerance and pharmacokinetics of high doses of favipiravir are of utmost importance considering that favipiravir is a candidate treatment for a variety of emerging severe viral diseases with poor prognosis.

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Ebola virus (EBOV) RNA in semen of survivors of EBOV disease up to 17 months after disease onset.

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High doses of Favipiravir were well tolerated in EBOV disease survivors.

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No QTc interval prolongation of grade 2, 3 or 4 with high doses of Favipiravir.

A novel stability-indicating HPLC-DAD method for determination of favipiravir, a potential antiviral drug for COVID-19 treatment; application to degradation kinetic studies and in-vitro dissolution profiling

Modern pharmaceutical analysis is paying a lot of attention to the stability of novel drug formulations as well as establishment of suitable stability-indicating approaches. In the current work, a comprehensive stability-indicating HPLC-DAD method has been developed and validated for determination of favipiravir (FAV) which is a novel and emerging antiviral option in COVID-19 treatment. The stability of FAV was examined under different stress conditions. FAV was found to be susceptible to acid, base hydrolysis and oxidative degradation. Structure elucidation of the forced degradation products was carried out using mass spectrometry (MS) operated in electrospray ionization mode. Effective separation of FAV and its induced degradation products was achieved using isocratic elution mode on Zorbax C₁₈ column maintained at 30 °C. The mobile phase used was comprised of 25.0 mM phosphate buffer (pH 3.5 ± 0.05) containing 0.1% (w/v) heptane sulphonic acid sodium salt-methanol-acetonitrile (62:28:10, by volume), delivered at flow rate of 1.0 mL/min. The diode array detector signal for FAV was monitored at 321.0 nm over a concentration range of 6.25-250.00 µg/mL. The potential mechanisms for generation of degradation products were postulated through comparison of MS¹ fragmentation pattern of FAV and its degradation products. Moreover, the proposed method was also extended to study the degradation kinetics. Additionally, dissolution profiling of FAV in different media was monitored. Clearly, the suggested approach is accurate, reliable, time-saving, and cost-effective. As a result, it may be utilized for regular quality control and stability assessment of FAV in its tablet dosage form.

The discovery and development of novel treatment strategies for filoviruses

INTRODUCTION

Filoviruses are negative-stranded, enveloped RNA viruses that can cause hemorrhagic fever in humans and include Ebola and Marburg viruses. Lethality rates can reach 90% in isolated outbreaks. The 2013-2016 Ebola virus epidemic demonstrated the global threat of filoviruses and hastened development of vaccines and therapeutics. There are six known filoviruses that cause disease in humans, but still few therapeutics are available for treatment.

AREAS COVERED

This review summarizes identification, testing, and development of therapeutics based on the peer-reviewed scientific literature beginning with the discovery of filoviruses in 1967. Small molecules, antibodies, cytokines, antisense, post-exposure vaccination, and host-targeted therapeutic approaches are discussed. An emphasis is placed on therapeutics that have shown promise in in vivo studies.

EXPERT OPINION

Two monoclonal antibody regimens are approved for use in humans for one filovirus (Ebola virus), and preclinical nonhuman primate studies suggest that other monoclonal-based therapies are likely to be effective against other filoviruses. Significant progress has been made in small-molecule antivirals and host-targeted approaches. An important consideration is the necessity of pan-filovirus therapeutics via broadly effective small molecules, antibody cocktails, and cross-reactive antibodies. The use of filovirus therapeutics as prophylactic treatment or in chronically infected individuals should be considered.

Scoping insight on antiviral drugs against COVID-19

Background

COVID-19 is an ongoing viral pandemic produced by SARS-CoV-2. In light of in vitro efficacy, several medications were repurposed for its management. During clinical use, many of these medications produced inconsistent results or had varying limitations.

Objective

The purpose of this literature review is to explain the variable efficacy or limitations of Lopinavir/Ritonavir, Remdesivir, Hydroxychloroquine, and Favipiravir in clinical settings.

Method

A study of the literature on the pharmacodynamics (PD), pharmacokinetics (PK), safety profile, and clinical trials through academic databases using relevant search terms.

Results & discussion

The efficacy of an antiviral drug against COVID-19 is associated with its ability to achieve therapeutic concentration in the lung and intestinal tissues. This efficacy depends on the PK properties, particularly protein binding, volume of distribution, and half-life. The PK and PD of the model drugs need to be integrated to predict their limitations.

Conclusion

Current antiviral drugs have varying pharmacological constraints that may associate with limited efficacy, especially in severe COVID-19 patients, or safety concerns.

Enhancing the Antiviral Potency of Nucleobases for Potential Broad-Spectrum Antiviral Therapies

Broad-spectrum antiviral therapies hold promise as a first-line defense against emerging viruses by blunting illness severity and spread until vaccines and virus-specific antivirals are developed. The nucleobase favipiravir, often discussed as a broad-spectrum inhibitor, was not effective in recent clinical trials involving patients infected with Ebola virus or SARS-CoV-2. A drawback of favipiravir use is its rapid clearance before conversion to its active nucleoside-5′-triphosphate form. In this work, we report a synergistic reduction of flavivirus (dengue, Zika), orthomyxovirus (influenza A), and coronavirus (HCoV-OC43 and SARS-CoV-2) replication when the nucleobases favipiravir or T-1105 were combined with the antimetabolite 6-methylmercaptopurine riboside (6MMPr). The 6MMPr/T-1105 combination increased the C-U and G-A mutation frequency compared to treatment with T-1105 or 6MMPr alone. A further analysis revealed that the 6MMPr/T-1105 co-treatment reduced cellular purine nucleotide triphosphate synthesis and increased conversion of the antiviral nucleobase to its nucleoside-5′-monophosphate, -diphosphate, and -triphosphate forms. The 6MMPr co-treatment specifically increased production of the active antiviral form of the nucleobases (but not corresponding nucleosides) while also reducing levels of competing cellular NTPs to produce the synergistic effect. This in-depth work establishes a foundation for development of small molecules as possible co-treatments with nucleobases like favipiravir in response to emerging RNA virus infections.

Elevated blood favipiravir levels are inversely associated with ferritin levels and induce the elevation of uric acid levels in COVID-19 treatment: A retrospective single-center study

Introduction

Measurement of blood Favipiravir (FPV) levels and accumulation of data in COVID-19 patients are critical for assessing FPV efficacy and safety. We performed a retrospective study based on measurements of blood levels of FPV and related factors in COVID-19 patients admitted to our hospital. Furthermore, we also investigated the association between blood FPV levels and uric acid level alterations before and after FPV administration.

Methods

We enrolled 27 COVID-19 patients who had received FPV treatment at Hokushin General Hospital from April 1 to December 31, 2020. Age, gender, COVID-19 severity, presence of comorbidities, and laboratory data for each subject were investigated to identify factors that correlate with blood FPV levels. Uric acid levels were measured before and after FPV administration and a difference between the levels (i.e., a change of uric acid level) was evaluated.

Results

When a significant univariate variable was input by the stepwise method and a combination of variables that maintained statistical superiority was searched, serum ferritin was the only factor that independently affected blood FPV level. Furthermore, in the high-FPV group (20 μg/mL or more), a significant increase in uric acid levels was observed after FPV administration. The increment value was significantly larger than that in the low-FPV group (less than 20 μg/mL).

Conclusions

Ferritin level was an important independent factor inversely affecting blood FPV level. Furthermore, a high blood FPV level induced the elevation of uric acid levels in COVID-19 treatment.

Development and Validation of a Rapid HPLC-DAD Method for Determination of Favipiravir in Pharmaceutical Formulation

Objective: The aim of this work was to develop and validate a rapid and simple high-performance liquid chromatography method with a diode- array detector (HPLC-DAD) for determination of favipiravir in bulk and tablet formulations. Methods: The chromatographic analysis was performed at 30 °C with a Poroshell 120EC-C18 column (4.6 x 50 mm, 2.7 µm). The mobile phase was a mixture of 0.1% formic acid in water and 0.1% formic acid in acetonitrile (90:10, v/v). The run time was 5 min at a flow rate of 0.5 mL/min. Results: The proposed method was successfully validated in terms of precision, accuracy, linearity, robustness, limits of detection (LOD) and quantification (LOQ) parameters. The calibration plot was linear over a concentration range of 10-100 µg/mL. The LOD and LOQ values were found to be 0.58 µg/mL and 2.03 µg/mL, respectively. The average recovery values were found to vary from 99.45 percent to 104.29 percent. Conclusion: As a result, it was concluded that the developed method can be used successfully in the determination of favipiravir in pharmaceutical preparations.

Optimization of Analytical Procedure for In-hospital Rapid Quantification of Serum Level of Favipiravir in the Pharmacological Treatment of COVID-19

An in-hospital rapid method for quantifying the serum level of favipiravir (FPV) in the pharmacological treatment of COVID-19 was developed by an appropriate combination of a solid-phase extraction treatment and a reversed-phase HPLC/UV detection system. The quantification method was well-validated and applied to measuring the serum FPV level in a clinical practice at a general hospital that accepts COVID-19 patients. Furthermore, an analysis of data from our preliminary interaction analysis revealed, for the first time, that FPV selectively forms complexes with ferric (Fe3+) and cupric (Cu2+) ions.