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

Viral-host molecular interactions and metabolic modulation: Strategies to inhibit flaviviruses pathogenesis

Flaviviruses, which include globally impactful pathogens, such as West Nile virus, yellow fever virus, Zika virus, Japanese encephalitis virus, and dengue virus, contribute significantly to human infections. Despite the ongoing emergence and resurgence of flavivirus-mediated pathogenesis, the absence of specific therapeutic options remains a challenge in the prevention and treatment of flaviviral infections. Through the intricate processes of fusion, transcription, replication, and maturation, the complex interplay of viral and host metabolic interactions affects pathophysiology. Crucial interactions involve metabolic molecules, such as amino acids, glucose, fatty acids, and nucleotides, each playing a pivotal role in the replication and maturation of flaviviruses. These viral-host metabolic molecular interactions hijack and modulate the molecular mechanisms of host metabolism. A comprehensive understanding of these intricate metabolic pathways offers valuable insights, potentially unveiling novel targets for therapeutic interventions against flaviviral pathogenesis. This review emphasizes promising avenues for the development of therapeutic agents that target specific metabolic molecules, such as amino acids, glucose, fatty acids, and nucleotides, which interact with flavivirus replication and are closely linked to the modulation of host metabolism. The clinical limitations of current drugs have prompted the development of new inhibitory strategies for flaviviruses based on an understanding of the molecular interactions between the virus and the host.

Repurposing existing drugs for the treatment ofCOVID-19/SARS-CoV-2: A review of pharmacological effects and mechanism of action

Following the coronavirus disease-2019 outbreak caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), there is an ongoing need to seek drugs that target COVID-19. First off, novel drugs have a long development cycle, high investment cost, and are high risk. Second, novel drugs must be evaluated for activity, efficacy, safety, and metabolic performance, contributing to the development cycle, investment cost, and risk. We searched the Cochrane COVID-19 Study Register (including PubMed, Embase, CENTRAL, ClinicalTrials.gov, WHO ICTRP, and medRxiv), Web of Science (Science Citation Index, Emerging Citation Index), and WHO COVID-19 Coronaviral Disease Global Literature to identify completed and ongoing studies as of February 20, 2024. We evaluated the pharmacological effects, in vivo and in vitro data of the 16 candidates in the paper. The difficulty of studying these candidates in clinical trials involving COVID-19 patients, dosage of repurposed drugs, etc. is discussed in detail. Ultimately, Metformin is more suitable for prophylactic administration or mildly ill patients; the combination of Oseltamivir, Tamoxifen, and Dexamethasone is suitable for moderately and severely ill patients; and more clinical trials are needed for Azvudine, Ribavirin, Colchicine, and Cepharanthine to demonstrate efficacy.

Favipiravir-induced bradycardia: A case report

Key Clinical Message

The purpose of this case report is to reveal one of the cardiovascular side effects of favipiravir, sinus bradycardia.

Abstract

Favipiravir has emerged as a potential treatment for COVID-19, with its antiviral properties showing promise in inhibiting viral replication. However, concerns regarding its safety profile, particularly its cardiac adverse effects, remain a subject of debate. We present the case of a 58-year-old man with a history of diabetes mellitus and chronic obstructive pulmonary disease who developed bradycardia following treatment with favipiravir for COVID-19 pneumonia. Despite being asymptomatic, the patient exhibited sinus bradycardia, which resolved upon discontinuation of favipiravir. Favipiravir has been associated with QT prolongation and sinus bradycardia, though the exact mechanisms remain unclear. Our case adds to the growing body of evidence highlighting the potential cardiac complications of favipiravir therapy in COVID-19 patients. Further research is warranted to clarify the underlying mechanisms and optimize patient management strategies. Clinicians should be cautious for cardiac adverse events when prescribing favipiravir for COVID-19 treatment, especially in patients with preexisting cardiac conditions. Continued research is essential to ensure the safe and effective use of favipiravir in the management of COVID-19.

Favipiravir does not improve viral clearance in mild to moderate COVID-19 - A systematic review and meta-analysis of randomized controlled trials

Purpose

Favipiravir has been used in the therapy of COVID-19, including patients with mild to moderate symptoms in certain countries. The aim of our systematic review and meta-analysis was to investigate its efficacy and safety in mild-to-moderate COVID-19 infections.

Methods

The PubMed, Embase, Web of Science, and Cochrane databases were systematically reviewed for articles reporting the results of randomized controlled trials published until January 6, 2023, resulting in the identification of 20 eligible studies.

Results

There were no significant differences in viral clearance time (HR = 1.20, p = 0.09) compared to those without favipiravir therapy. However, in the subgroup analyses, favipiravir treatment significantly increased viral clearance by 59 % (HR = 1.59, p < 0.01) and 42 % (HR = 1.42, p < 0.01], I2 = 20 %) compared to the comparator group in patients with moderate severity of COVID-19 and in the inpatient care setting, respectively. Favipiravir had no beneficial effects in the case of patients with mild symptoms and treated in ambulatory care.

Conclusions

The use of favipiravir is questionable in the treatment of outpatients with COVID-19 with mild symptoms. Moderate beneficial effects in the case of patients with moderate symptoms and inpatients should be treated with care due to the limitations of the analysed trials.

Pharmacogenomic Studies of Antiviral Drug Favipiravir

In this work, we conducted a study of the interaction between DNA and favipiravir (FAV). This chemotherapeutic compound is an antiviral drug for the treatment of COVID-19 and other infections caused by RNA viruses. This paper examines the electroanalytical characteristics of FAV. The determined concentrations correspond to therapeutically significant ones in the range of 50-500 µM (R2 = 0.943). We have shown that FAV can be electro-oxidized around the potential of +0.96 V ÷ +0.98 V (vs. Ag/AgCl). A mechanism for electrochemical oxidation of FAV was proposed. The effect of the drug on DNA was recorded as changes in the intensity of electrochemical oxidation of heterocyclic nucleobases (guanine, adenine and thymine) using screen-printed graphite electrodes modified with single-walled carbon nanotubes and titanium oxide nanoparticles. In this work, the binding constants (Kb) of FAV/dsDNA complexes for guanine, adenine and thymine were calculated. The values of the DNA-mediated electrochemical decline coefficient were calculated as the ratio of the intensity of signals for the electrochemical oxidation of guanine, adenine and thymine in the presence of FAV to the intensity of signals for the electro-oxidation of these bases without drug (S, %). Based on the analysis of electrochemical parameters, values of binding constants and spectral data, intercalation was proposed as the principal mechanism of the antiviral drug FAV interaction with DNA. The interaction with calf thymus DNA also confirmed the intercalation mechanism. However, an additional mode of interaction, such as a damage effect together with electrostatic interactions, was revealed in a prolonged exposure of DNA to FAV.

Favipiravir for treating COVID-19

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to challenge the health workforce and societies worldwide. Favipiravir was suggested by some experts to be effective and safe to use in COVID-19. Although this drug has been evaluated in randomized controlled trials (RCTs), it is still unclear if it has a definite role in the treatment of COVID-19.

OBJECTIVES

To assess the effects of favipiravir compared to no treatment, supportive treatment, or other experimental antiviral treatment in people with acute COVID-19.

SEARCH METHODS

We searched the Cochrane COVID-19 Study Register, MEDLINE, Embase, the World Health Organization (WHO) COVID-19 Global literature on coronavirus disease, and three other databases, up to 18 July 2023.

SELECTION CRITERIA

We searched for RCTs evaluating the efficacy of favipiravir in treating people with COVID-19.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures for data collection and analysis. We used the GRADE approach to assess the certainty of evidence for each outcome.

MAIN RESULTS

We included 25 trials that randomized 5750 adults (most under 60 years of age). The trials were conducted in Bahrain, Brazil, China, India, Iran, Kuwait, Malaysia, Mexico, Russia, Saudi Arabia, Thailand, the UK, and the USA. Most participants were hospitalized with mild to moderate disease (89%). Twenty-two of the 25 trials investigated the role of favipiravir compared to placebo or standard of care, whilst lopinavir/ritonavir was the comparator in two trials, and umifenovir in one trial. Most trials (24 of 25) initiated favipiravir at 1600 mg or 1800 mg twice daily for the first day, followed by 600 mg to 800 mg twice a day. The duration of treatment varied from five to 14 days. We do not know whether favipiravir reduces all-cause mortality at 28 to 30 days, or in-hospital (risk ratio (RR) 0.84, 95% confidence interval (CI) 0.49 to 1.46; 11 trials, 3459 participants; very low-certainty evidence). We do not know if favipiravir reduces the progression to invasive mechanical ventilation (RR 0.86, 95% CI 0.68 to 1.09; 8 trials, 1383 participants; very low-certainty evidence). Favipiravir may make little to no difference in the need for admission to hospital (if ambulatory) (RR 1.04, 95% CI 0.44 to 2.46; 4 trials, 670 participants; low-certainty evidence). We do not know if favipiravir reduces the time to clinical improvement (defined as time to a 2-point reduction in patients' admission status on the WHO's ordinal scale) (hazard ratio (HR) 1.13, 95% CI 0.69 to 1.83; 4 trials, 721 participants; very low-certainty evidence). Favipiravir may make little to no difference to the progression to oxygen therapy (RR 1.20, 95% CI 0.83 to 1.75; 2 trials, 543 participants; low-certainty evidence). Favipiravir may lead to an overall increased incidence of adverse events (RR 1.27, 95% CI 1.05 to 1.54; 18 trials, 4699 participants; low-certainty evidence), but may result in little to no difference inserious adverse eventsattributable to the drug (RR 1.04, 95% CI 0.76 to 1.42; 12 trials, 3317 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

The low- to very low-certainty evidence means that we do not know whether favipiravir is efficacious in people with COVID-19 illness, irrespective of severity or admission status. Treatment with favipiravir may result in an overall increase in the incidence of adverse events but may not result in serious adverse events.

Favipiravir does not appear to be a major teratogen: Case series from Türkiye

INTRODUCTION

Favipiravir has gained attention during the Coronavirus Disease-2019 pandemic due to its potential antiviral effect against Severe Acute Respiratory Syndrome Coronavirus-2. Favipiravir has been identified as a teratogen in animal studies, but there is limited human data. We aimed to evaluate the pregnancy outcomes of women exposed to favipiravir during the pandemic.

MATERIAL AND METHODS

Pregnant women who were exposed to favipiravir and applied to Marmara University School of Medicine Medical Pharmacology Outpatient Clinic Teratology Information Service between December 2020-September 2021 are included in the study. The demographic information, medical and obstetric histories of patients were acquired during admission, the outcomes of the pregnancies and the characteristics of the infants were gathered by regular phone calls. The infants whose parents consented were evaluated by a pediatrician for general well-being and congenital anomalies.

RESULTS

22 pregnant women were included in this study. 81.8 % received the recommended favipiravir dose (8000 mg in 5 days), in the first trimester. Two patients were lost to follow-up, there was one elective termination and 19 live births. Congenital anomalies were found in 2 infants, one of whom had 9q34 duplication syndrome. Except for these, all newborns examined by the pediatrician were healthy.

DISCUSSION

Within a limited case series, a subset of the infants exposed to favipiravir prenatally were followed up to 1 year of age. Two infants exhibited congenital malformations that cannot be directly linked to favipiravir due to confounding variables. Considering the limited data published, favipiravir does not appear to be a major teratogen.

Luminescence of favipiravir in skin appendages and sclera. A controlled study and literature review

BACKGROUND/OBJECTIVES

Favipiravir is an antiviral agent, recently used for COVID-19 infections. Several reports associate favipiravir intake with Wood's lamp fluorescence of hair, nails, and sclera. The present study was designed to elucidate the positivity rates, and sites of favipiravir-related fluorescence and to unravel the site-specific changes in fluorescence positivity rates by a function of time past exposure.

METHODS

The study population comprised 50 patients and 50 control individuals. All patients in the patient group had received a full dose of favipiravir for COVID-19 infection. Fifty volunteers served as the control group. Wood's lamp examination was performed in a completely darkened room, and the positivity rate, extent, pattern, and distribution of fluorescence were recorded.

RESULTS

Wood's light revealed fluorescence of the fingernails, toenails, sclera, and hair in 35 (70%), 35 (70%), 22 (44%), and 8 (16%) patients, respectively. No control individual tested positive by Wood's lamp. Statistical analysis revealed significant differences between patient and control groups in terms of Wood's light luminescence in the fingernails (p = .000), toenails (p = .000), sclera (p = .000) and hair (p = .003). Although fingernail, toenail, and hair fluorescence positivity rates declined or ceased at or after 91 days of favipiravir exposure, ocular fluorescence positivity rates were prolonged up to 188 days.

CONCLUSIONS

These findings confirm that favipiravir may produce fluorescence of nails, sclera, and hair, detectable by Wood's light starting from the initial month and peaking at second- and third months following exposure to the medication. Although nail and hair fluorescence tend to abate after 3 months, ocular fluorescence may persist even longer than 6 months after cessation of the medication.

Efficacy and Safety of Novel Oral Antivirals in Hospitalized COVID-19 Patients: A Network Meta-Analysis of Randomized Clinical Trials

Objective

Numerous pharmacological interventions are now under investigation for the treatment of the 2019 coronavirus pandemic (COVID-19), and the evidence is rapidly evolving. Our aim is to evaluate the comparative efficacy and safety of these drugs.

Methods

We searched for randomized clinical trials (RCTs) on the efficacy and safety of novel oral antivirals for the treatment of hospitalized COVID-19 patients until November 30, 2022, including baricitinib, ivermectin (IVM), favipiravir (FVP), chloroquine (CQ), lopinavir and ritonavir (LPV/RTV), hydroxychloroquine (HCQ), and hydroxychloroquine plus azithromycin (HCQ+AZT). The main outcomes of this network meta-analysis (NMA) were in-hospital mortality, adverse event (AE), recovery time, and improvement in peripheral capillary oxygen saturation (SpO2). For dichotomous results, the odds ratio (OR) was used, and the 95% confidence interval (CI) was determined. We also used meta-regression to explore whether different treatments affected efficacy and safety. STATA 15.0 was used to conduct the NMA. The research protocol was registered with PROSPERO (#CRD 42023415743).

Results

Thirty-six RCTs, with 33,555 hospitalized COVID-19 patients, were included in this analysis. First, we compared the efficacy of different novel oral antivirals. Baricitinib (OR 0.56, 95% CI: 0.35 to 0.90) showed the highest probability of being the optimal probiotic species in reducing in-hospital mortality and suggested that none of the interventions reduced AE better than placebo. In terms of safety outcomes, IVM ranked first in improving the recovery time of hospitalized COVID-19 patients (mean difference (MD) -1.36, 95% CI: -2.32 to -0.39). In addition, patients were most likely to increase SpO2 (OR 1.77, 95% CI: 0.09 to 3.45). The meta-regression revealed no significant differences between participants using different novel oral antivirals in all outcomes in hospitalized COVID-19 patients.

Conclusion

Currently, baricitinib has reduced in-hospital mortality in hospitalized COVID-19 patients, with moderate certainty of evidence. IVM appeared to be a safer option than placebo in improving recovery time, while FVP was associated with increased SpO2 safety outcomes. These preliminary evidence-based observations should guide clinical practice until more data are made public.

Does COVID-19 Cause Non-Dıpper Hypertension?

Coronavirus disease 2019 (COVID-19) remains a health problem worldwide. The present study aimed to investigate the effect of blood pressure (BP) on the circadian pattern and prevalence of new-onset non-dipper hypertension in the post-COVID period in patients with known hypertension. This prospective single-center study included 722 patients hospitalized for COVID-19 infection. Ambulatory BP (ABP) data were collected during their initial hospitalization. The ABP data were reassessed 1 month after the patients were discharged. The results were compared with a healthy control group with known hypertension but without COVID-19 infection. After exclusion criteria were applied, the study included 187 patients with COVID-19 and 136 healthy hypertensive controls. Post-COVID ABP showed that patients with COVID-19 had significantly higher mean 24-h systolic and diastolic BP, mean nighttime systolic and diastolic BP, and mean daytime diastolic BP than the control group. In addition, new-onset non-dipper hypertension was significantly higher in patients with COVID-19. This study demonstrated for the first time that the circadian pattern is disturbed and a non-dipper pattern develops in individuals with known hypertension during the post-COVID period.

Impact of common comorbidities on antimicrobial consumption and mortality amongst critically ill COVID-19 patients: A retrospective two center study in Saudi Arabia

Objectives

To determine the association between common comorbidities, ICU mortality and antimicrobial consumption among critically ill COVID 19 patients in Saudi Arabia.

Methods

A retrospective observational study of patients admitted to the ICU from March 1st, 2020, through August 31st, 2021. We excluded patients who stayed <24 h in the ICU and with no confirmed COVID-19 PCR testing.

Results

Of the 976 screened ICU patients, 848 were included. While there was no difference in mortality between patients with and without comorbidities, those with at least one comorbidity had a higher severity of illness (p = 0.013). Compared to survivors, non-survivors were more likely to require mechanical ventilation and vasopressor support (P < 0.001). Almost all patients received at least one antimicrobial therapy. Predictors independently associated with ICU mortality were: older age (adjusted odds ratio [AOR], 1.03; 95% confidence interval [CI], 1.01-1.04), vancomycin use (AOR, 2.69; 95% [CI], 1.65-4.37), linezolid use (AOR, 2.65; 95% [CI], 1.65-4.04), sepsis or septic shock (AOR, 6.39; 95% [CI], 3.68-11.08), Acute Kidney Injury (AKI) (AOR, 2.51; 95% [CI], 1.61-3.92) and Acute Respiratory Distress Syndrome (ARDS) (AOR, 2.03; 95% [CI], 1.61-3.92).

Conclusion

Older age, vancomycin and linezolid use, sepsis/septic shock, AKI, and ARDS were negative prognostic factors in critically ill COVID-19 patients. More studies are needed to evaluate the outcomes of survived critically ill patients in relation to their vaccination status.

Protein structure-based in-silico approaches to drug discovery: Guide to COVID-19 therapeutics

With more than 5 million fatalities and close to 300 million reported cases, COVID-19 is the first documented pandemic due to a coronavirus that continues to be a major health challenge. Despite being rapid, uncontrollable, and highly infectious in its spread, it also created incentives for technology development and redefined public health needs and research agendas to fast-track innovations to be translated. Breakthroughs in computational biology peaked during the pandemic with renewed attention to making all cutting-edge technology deliver agents to combat the disease. The demand to develop effective treatments yielded surprising collaborations from previously segregated fields of science and technology. The long-standing pharmaceutical industry's aversion to repurposing existing drugs due to a lack of exponential financial gain was overrun by the health crisis and pressures created by front-line researchers and providers. Effective vaccine development even at an unprecedented pace took more than a year to develop and commence trials. Now the emergence of variants and waning protections during the booster shots is resulting in breakthrough infections that continue to strain health care systems. As of now, every protein of SARS-CoV-2 has been structurally characterized and related host pathways have been extensively mapped out. The research community has addressed the druggability of a multitude of possible targets. This has been made possible due to existing technology for virtual computer-assisted drug development as well as new tools and technologies such as artificial intelligence to deliver new leads. Here in this article, we are discussing advances in the drug discovery field related to target-based drug discovery and exploring the implications of known target-specific agents on COVID-19 therapeutic management. The current scenario calls for more personalized medicine efforts and stratifying patient populations early on for their need for different combinations of prognosis-specific therapeutics. We intend to highlight target hotspots and their potential agents, with the ultimate goal of using rational design of new therapeutics to not only end this pandemic but also uncover a generalizable platform for use in future pandemics.

Activation of the urotensin-II receptor by remdesivir induces cardiomyocyte dysfunction

Remdesivir is an antiviral drug used for COVID-19 treatment worldwide. Cardiovascular side effects have been associated with remdesivir; however, the underlying molecular mechanism remains unknown. Here, we performed a large-scale G-protein-coupled receptor screening in combination with structural modeling and found that remdesivir is a selective, partial agonist for urotensin-II receptor (UTS2R) through the Gα_i/o-dependent AKT/ERK axis. Functionally, remdesivir treatment induced prolonged field potential and APD₉₀ in human induced pluripotent stem cell (iPS)-derived cardiomyocytes and impaired contractility in both neonatal and adult cardiomyocytes, all of which mirror the clinical pathology. Importantly, remdesivir-mediated cardiac malfunctions were effectively attenuated by antagonizing UTS2R signaling. Finally, we characterized the effect of 110 single-nucleotide variants in UTS2R gene reported in genome database and found four missense variants that show gain-of-function effects in the receptor sensitivity to remdesivir. Collectively, our study illuminates a previously unknown mechanism underlying remdesivir-related cardiovascular events and that genetic variations of UTS2R gene can be a potential risk factor for cardiovascular events during remdesivir treatment, which collectively paves the way for a therapeutic opportunity to prevent such events in the future.

Multicenter, single-blind, randomized controlled study of the efficacy and safety of favipiravir and nafamostat mesilate in patients with COVID-19 pneumonia

OBJECTIVES

To evaluate the efficacy and safety of nafamostat combined with favipiravir for the treatment of COVID-19.

METHODS

We conducted a multicenter, randomized, single-blind, placebo-controlled, parallel assignment study in hospitalized patients with mild-to-moderate COVID-19 pneumonia. Patients were randomly assigned to receive favipiravir alone (n = 24) or nafamostat with favipiravir (n = 21). The outcomes included changes in the World Health Organization clinical progression scale score, time to improvement in body temperature, and improvement in oxygen saturation (SpO₂).

RESULTS

There was no significant difference in the changes in the clinical progression scale between nafamostat with favipiravir and favipiravir alone groups (median, -0.444 vs -0.150, respectively; least-squares mean difference, -0.294; P = 0.364). The time to improvement in body temperature was significantly shorter in the combination group (5.0 days; 95% confidence interval, 4.0-7.0) than in the favipiravir group (9.0 days; 95% confidence interval, 7.0-18.0; P =0.009). The changes in SpO₂ were greater in the combination group than in the favipiravir group (0.526% vs -1.304%, respectively; least-squares mean difference, 1.831; P = 0.022). No serious adverse events or deaths were reported, but phlebitis occurred in 57.1% of the patients in the combination group.

CONCLUSION

Although our study showed no differences in clinical progression, earlier defervescence, and recovery of SpO₂ were observed in the combination group.

Favipiravir for symptomatic COVID-19: A nationwide observational cohort study

INTRODUCTION

Favipiravir, an antiviral agent with activity against SARS-CoV-2, was made available to hospitals in Japan for off-label use among COVID-19 patients between 2020 and 2021.

METHODS

A nationwide observational cohort study was conducted on patients who received favipiravir as part of clinical care between February 2020 and December 2021. Information was collected on demographics, comorbidities, severity of illness, use of favipiravir and other medications targeting COVID-19, adverse events, clinical status at 7 and 14 days and clinical outcome one month after admission to the hospital.

RESULTS

A total of 17,508 hospitalized patients who received favipiravir were registered from 884 hospitals. In terms of demographics, 55.9% were age ≥60 years, and 62.3% were male. At least one of the four surveyed comorbidities was present in 45.5% of the patients. The rates of clinical improvement at 7 and 14 days were 72.4％ and 87.5%, 61.4% and 76.6%, and 45.4% and 59.5% for mild, moderate, and severe diseases, respectively. The case fatality rates within a month from hospitalization were 3.3%, 12.6%, and 29.1% for mild, moderate, and severe diseases, respectively. Significant correlations were observed between death and advanced age, male sex, moderate or severe disease, diabetes, cardiovascular diseases, and immunosuppression. Commonly reported adverse events included uric acid level increase or hyperuricemia (16.8%), liver function abnormalities (6.9%), and rash (1.0%).

CONCLUSIONS

Favipiravir was well tolerated among COVID-19 patients. The study provides insights into the use of this agent at hospitals across Japan in the early phase of the pandemic.

Kill or corrupt: Mechanisms of action and drug-resistance of nucleotide analogues against SARS-CoV-2

Nucleoside/tide analogues (NAs) have long been used in the fight against viral diseases, and now present a promising option for the treatment of COVID-19. Once activated to the 5'-triphosphate state, NAs act by targeting the viral RNA-dependent RNA-polymerase for incorporation into the viral RNA genome. Incorporated analogues can either 'kill' (terminate) synthesis, or 'corrupt' (genetically or chemically) the RNA. Against coronaviruses, the use of NAs has been further complicated by the presence of a virally encoded exonuclease domain (nsp14) with proofreading and repair capacities. Here, we describe the mechanism of action of four promising anti-COVID-19 NAs; remdesivir, molnupiravir, favipiravir and bemnifosbuvir. Their distinct mechanisms of action best exemplify the concept of 'killers' and 'corruptors'. We review available data regarding their ability to be incorporated and excised, and discuss the specific structural features that dictate their overall potency, toxicity, and mutagenic potential. This should guide the synthesis of novel analogues, lend insight into the potential for resistance mutations, and provide a rational basis for upcoming combinations therapies.

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

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

COVID-19 Therapeutics: Use, Mechanism of Action, and Toxicity (Xenobiotics)

SARS-CoV-2 emerged in 2019 and led to the COVID-19 pandemic. Efforts to develop therapeutics against SARS-Cov-2 led to both new treatments and attempts to repurpose existing medications. Here, we provide a narrative review of the xenobiotics and alternative remedies used or proposed to treat COVID-19. Most repositioned xenobiotics have had neither the feared toxicity nor the anticipated efficacy. Repurposed viral replication inhibitors are not efficacious and frequently associated with nausea, vomiting, and diarrhea. Antiviral medications designed specifically against SARS-CoV-2 may prevent progression to severe disease in at-risk individuals and appear to have a wide therapeutic index. Colloidal silver, zinc, and ivermectin have no demonstrated efficacy. Ivermectin has a wide therapeutic index but is not efficacious and acquiring it from veterinary sources poses additional danger. Chloroquine has a narrow therapeutic index and no efficacy. A companion review covers vaccines, monoclonal antibodies, and immunotherapies. Together, these two reviews form an update to our 2020 review.

CURRENT ASPECTS OF ETIOTROPIC COVID-19 THERAPY

Since the beginning of the pandemic, repeated attempts have been made to develop etiotropic therapy for a novel coronavirus infection. Hydroxychloroquine, lopinavir/ritonavir, etc. derivatives were used as antiviral agents, however, they demonstrated a low efficiency and an insufficient safety. In this connection, other groups of drugs with a more effective and safe pharmacological profile are currently being actively used.

The aim of the study was to analyze the literature references on the efficacy and safety of antiviral drugs for the COVID-19 treatment.

Materials and methods. When searching for the materials for the review article writing, such abstract databases as PubMed, Google Scholar, e-Library were used. The search was carried out on publications for the period from January 2020 to september 2022. The key queries were: COVID-19, etiotropic therapy; immunological drugs; antiviral drugs; interferons.

Results. Currently, there are various degrees of effective etiotropic drugs for the treatment of COVID-19 patients. The review has considered a few groups of drugs that are of interest from the point of view of etiotropic therapy: immunological drugs (anticovid plasma, the drugs based on antiviral antibodies, the drugs of recombinant interferons-α2 and -β1, as well as interferon inducers, i.e., the drugs based on double-stranded RNA sodium salt, and others); drugs that block the penetration of the virus into the cell (umifenovir); the drugs that disrupt the process of the viral replication (favipiravir, remdesivir, molnupiravir, nirmatrelvir/ritonavir).

Conclusion. Synthetic antivirals, in particular favipiravir, molnupiravir, remdesivir, and nirmatrelvir/ritonavir, have the largest evidence base for their efficacy and safety. The search for new effective and safe etiotropic drugs for the treatment of COVID-19, as well as the collection and analysis of post-registration data on the drugs already used in clinical practice, continues.

Nucleoside analogs for management of respiratory virus infections: mechanism of action and clinical efficacy

The COVID-19 pandemic has accelerated the development of nucleoside analogs to treat respiratory virus infections, with remdesivir being the first compound to receive worldwide authorization and three other nucleoside analogs (i.e. favipiravir, molnupiravir, and bemnifosbuvir) in the pipeline. Here, we summarize the current knowledge concerning their clinical efficacy in suppressing the virus and reducing the need for hospitalization or respiratory support. We also mention trials of favipiravir and lumicitabine, for influenza and respiratory syncytial virus, respectively. Besides, we outline how nucleoside analogs interact with the polymerases of respiratory viruses, to cause lethal virus mutagenesis or disturbance of viral RNA synthesis. In this way, we aim to convey the key findings on this rapidly evolving class of respiratory virus medication.

Pulmonary Delivery of Favipiravir in Rats Reaches High Local Concentrations without Causing Oxidative Lung Injury or Systemic Side Effects

Favipiravir displays a rapid viral clearance, a high recovery rate and broad therapeutic safety; however, its oral administration was associated with systemic side effects in susceptible patients. Considering that the pulmonary route could provide a high drug concentration, and a safer application with less absorption into systemic circulation, it was aimed to elucidate whether favipiravir delivered via soft-mist inhaler has any deleterious effects on lung, liver and kidney tissues of healthy rats. Wistar albino rats of both sexes (n = 72) were placed in restrainers, and were given either saline or favipiravir (1, 2.5, 5 or 10 mg/kg in 1 mL saline) by inhalation within 2 min for 5 consecutive days. On the 6th day, electrocardiographic recording was obtained, and cardiac blood and lung tissues were collected. Favipiravir did not alter cardiac rhythm, blood cell counts, serum levels of alanine transaminase, aspartate transaminase, blood urea nitrogen, creatinine, urea or uric acid, and did not cause any significant changes in the pulmonary malondialdehyde, myeloperoxidase activity or antioxidant glutathione levels. Our data revealed that pulmonary use of favipiravir via soft-mist inhaler enables a high local concentration compared to plasma without oxidative lung injury or cardiac or hepatorenal dysfunction.

Efficacy of tocilizumab in the treatment of COVID-19: An umbrella review

Tocilizumab is an interleukin (IL)-6 receptor inhibitor that has been proposed as a therapeutic agent for treating coronavirus disease 2019 (COVID-19). The aim of this umbrella review was to determine the efficacy of tocilizumab in treating COVID-19, and to provide an overview of all systematic reviews on this topic. We systematically searched PubMed, Scopus, the Web of Science collection, the Cochrane library, Epistemonikos, and Google Scholar, as well as the medRxiv preprint server. These databases were searched up to 30 September 2021, using the following keywords: 'SARS-CoV-2', 'COVID-19', 'tocilizumab', 'RHPM-1', 'systematic review', and 'meta-analysis'. Studies were included if they were systematic reviews (with or without meta-analysis) investigating the efficacy or safety of tocilizumab in confirmed COVID-19 patients. The AMSTAR 2 checklist was used to assess quality of the included articles, while publication bias was examined using Egger's test. A total of 50 eligible systematic reviews were included. The pooled estimates showed significant reductions in clinical failure (risk ratio (RR) 0.75; 95% confidence interval (CI), 0.61-0.93), deaths (RR 0.78; 95%CI, 0.71-0.85) and the need for mechanical ventilation (RR 0.77; 95%CI, 0.64-0.92) for those receiving tocilizumab compared with the control group. Also, an emerging survival benefit was demonstrated for those who received tocilizumab, over those in the control group (adjusted hazard ratio (aHR) 0.52; 95%CI, 0.43-0.63). In addition, tocilizumab substantially increased the number of ventilator-free days, compared with the control treatments (weighted mean difference (WMD) 3.38; 95%CI, 0.51-6.25). Furthermore, lymphocyte count (WMD 0.26 × 109 /L; 95%CI, 0.14-0.37), IL-6 (WMD 176.99 pg/mL; 95%CI, 76.34-277.64) and D-dimer (WMD 741.08 ng/mL; 95%CI, 109.42-1372.75) were all significantly elevated in those receiving tocilizumab. However, the level of lactate dehydrogenase (LDH) (WMD -30.88 U/L; 95%CI, -51.52, -10.24) and C-reactive protein (CRP) (WMD -104.83 mg/L; 95%CI, -133.21, -76.46) were both significantly lower after treatment with tocilizumab. Tocilizumab treatment reduced the risk of intubation, mortality and the length of hospital stay, without increasing the risk of superimposed infections in COVID-19 patients. Therefore, tocilizumab can be considered an effective therapeutic agent for treating patients with COVID-19.

Case report: Novel treatment regimen for enterovirus encephalitis in SCID

Most non-polio enterovirus infections in immunocompetent individuals are acute and self-limiting in nature; however, infection can be severe, chronic and have devastating outcomes in immunocompromised hosts. Therapeutic strategies have predominantly involved supportive care, with the lack of approved antiviral treatments proving challenging for management. We report a case of an 8-month-old child who presented with severe enterovirus encephalitis following gene therapy for X-linked severe combined immunodeficiency (X-SCID) and who demonstrated clinical and microbiological improvement after a novel regimen of favipiravir, fluoxetine, and high-dose intravenous immunoglobulin (IVIg). The patient presented 6 weeks post–gene therapy with rapid neurological deterioration in the context of incomplete immune reconstitution, with microbiological and radiological evidence confirming enterovirus encephalitis. His neurologic examination stabilised 8 weeks after treatment, and he subsequently demonstrated excellent immune recovery. This is the first case report of combined therapy with favipiravir, fluoxetine, and high-dose IVIg in the context of severe enterovirus encephalitis in an immunocompromised host. This case highlights the importance of considering enterovirus encephalitis in immunocompromised patients presenting with both acute and chronic neurological signs, as well as developmental regression. The demonstrated treatment success and the associated low risk of toxicity warrant further investigation of this therapeutic regimen.

Perspective: repurposed drugs for COVID-19

Introduction

The article aims to emphasize the necessity of proper research design, both scientifically and ethically, in order to provide good evidence for physicians to base their decisions on when prescribing drug treatment.

Methods

Research articles and guidelines related to therapy of COVID-19 were searched from the PubMed database.

Results

Only remdesivir and tocilizumab are medicines that have been approved by the US FDA's decision to approve their clinical use in moderate and severe COVID-19.

Conclusions

Favipiravir, ivermectin and andrographolide need further well-conducted research to confirm the efficacy and safety against COVID-19 at different stages.

Real-World Use of Molnupiravir in the Treatment of Outpatients with SARS-CoV-2 Infection-A Patient Profile Based on the Experience of a Tertiary Infectious Disease Center

During the current pandemic, the gap between fundamental research and clinical practice has been narrowing at a faster pace than ever before. While clinical trials play the main role of confirming the safety and efficacy of new drugs, a drug's introduction into clinical practice creates the need for further research in order to best position the use of the novel drug in terms of when, to whom, and how it would be best administered to achieve the best possible outcome under feasible clinical circumstances. We briefly present the results of a retrospective analysis of the characteristics of outpatients treated with molnupiravir in a tertiary care infectious disease hospital in Bucharest, Romania, between February and March 2022, when Romania was experiencing its fifth wave of COVID-19. A total of 46 outpatients received molnupiravir treatment and had complete clinical data available; of them, 56.5% (n = 20) were males and the median age was 48.5 years (IQR: 37.8, 67.0 years). A total of 54.2% (n = 26) of patients had at least one chronic condition. Of the 45 patients who underwent lung CT imaging evaluation, 13 (28.9%) showed changes suggestive of COVID-19 pneumonia. COVID-19 vaccination status was strongly protective for pneumonia (p = 0.002). All patients were symptomatic, and molnupiravir was initiated at a mean time from onset of symptoms of 3.5 (±1.5) days. At phone follow-up 5 days after the initial evaluation and initiation of molnupiravir treatment, all patients, except for one, confirmed a favorable course under treatment, with no worsening of COVID-19 severity and improvement in symptoms; none of them progressed to respiratory failure or required hospitalization. In conclusion, treatment was well tolerated and associated a favorable outcome of COVID-19 in routine practice in a clinical population that was slightly older and had a smaller burden of comorbidities and a higher rate of COVID-19 vaccination compared to that from the pivotal trial.

A Versatile Class of 1,4,4-Trisubstituted Piperidines Block Coronavirus Replication In Vitro

There is a clear need for novel antiviral concepts to control SARS-CoV-2 infection. Based on the promising anti-coronavirus activity observed for a class of 1,4,4-trisubstituted piperidines, we here conducted a detailed analysis of the structure-activity relationship of these structurally unique inhibitors. Despite the presence of five points of diversity, the synthesis of an extensive series of analogues was readily achieved by Ugi four-component reaction from commercially available reagents. After evaluating 63 analogues against human coronavirus 229E, four of the best molecules were selected and shown to have micromolar activity against SARS-CoV-2. Since the action point was situated post virus entry and lying at the stage of viral polyprotein processing and the start of RNA synthesis, enzymatic assays were performed with CoV proteins involved in these processes. While no inhibition was observed for SARS-CoV-2 nsp12-nsp7-nsp8 polymerase, nsp14 N7-methyltransferase and nsp16/nsp10 2'-O-methyltransferase, nor the nsp3 papain-like protease, the compounds clearly inhibited the nsp5 main protease (Mpro). Although the inhibitory activity was quite modest, the plausibility of binding to the catalytic site of Mpro was established by in silico studies. Therefore, the 1,4,4-trisubstituted piperidines appear to represent a novel class of non-covalent CoV Mpro inhibitors that warrants further optimization and development.

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.