Pharmacokinetic characterization of favipiravir in patients with COVID-19

Unveiling therapeutic dynamics: An in-depth comparative analysis of neutralizing monoclonal antibodies and favipiravir in alleviating COVID-19 outpatients impacts among middle-aged and special populations (MA-FAST)

BACKGROUND

Neutralizing monoclonal antibodies (NMabs) are recognized for their efficacy against non-severe COVID-19. However, spike protein mutations may confer resistance. This study evaluates the effectiveness of favipiravir (FPV) versus NMabs in preventing severe COVID-19 in special populations.

METHODS

A retrospective cohort was conducted on middle-aged, elderly, diabetic, or obese patients with COVID-19 treated with either FPV or NMabs. Propensity score matching (PSM) was used for analysis.

RESULTS

The study included 1410 patients, resulting in four cohorts: middle-aged (36), elderly (48), diabetic (46), and obese (28) post-PSM. No significant differences were noted in 28-day emergency department (ED) visits across all groups between NMabs and FPV treatments, despite lower immunity in the FPV group. However, the diabetic group treated with FPV had higher 28-day hospitalization and oxygen supplemental, with no differences in the other groups. Intensive care unit (ICU) admissions, invasive mechanical ventilation, and mortality rates were similar between the two treatments.

CONCLUSIONS

Early dose-adjusted FPV showed no difference from NMabs in preventing ED visits, ICU admissions, ventilator needs, or mortality among patients with major comorbidities. Diabetic patients on FPV experienced higher hospitalizations and oxygen needs, with no observed differences in other groups. FPV may be a viable alternative, especially in settings with limited resources.

Human bronchopulmonary disposition and plasma pharmacokinetics of oral bemnifosbuvir (AT-527), an experimental guanosine nucleotide prodrug for COVID-19

BACKGROUND

Bemnifosbuvir (AT-527) is a novel oral guanosine nucleotide antiviral drug for the treatment of persons with COVID-19. Direct assessment of drug disposition in the lungs, via bronchoalveolar lavage, is necessary to ensure antiviral drug levels at the primary site of SARS-CoV-2 infection are achieved.

OBJECTIVES

This Phase 1 study in healthy subjects aimed to assess the bronchopulmonary pharmacokinetics, safety and tolerability of repeated doses of bemnifosbuvir.

METHODS

A total of 24 subjects were assigned to receive bemnifosbuvir twice daily at doses of 275, 550 or 825 mg for up to 3.5 days.

RESULTS

AT-511, the free base of bemnifosbuvir, was largely eliminated from the plasma within 6 h post dose in all dosing groups. Antiviral drug levels of bemnifosbuvir were consistently achieved in the lungs with bemnifosbuvir 550 mg twice daily. The mean level of the guanosine nucleoside metabolite AT-273, the surrogate of the active triphosphate metabolite of the drug, measured in the epithelial lining fluid of the lungs was 0.62 µM at 4-5 h post dose. This exceeded the target in vitro 90% effective concentration (EC90) of 0.5 µM for antiviral drug exposure against SARS-CoV-2 replication in human airway epithelial cells. Bemnifosbuvir was well tolerated across all doses tested, and most treatment-emergent adverse events reported were mild in severity and resolved.

CONCLUSIONS

The favourable pharmacokinetics and safety profile of bemnifosbuvir demonstrates its potential as an oral antiviral treatment for COVID-19, with 550 mg bemnifosbuvir twice daily currently under further clinical evaluation in persons with COVID-19.

Green chemometric-assisted UV-spectrophotometric methods for the determination of favipiravir, cefixime and moxifloxacin hydrochloride as an effective therapeutic combination for COVID-19; application in pharmaceutical form and spiked human plasma

As pharmaceutical analysis progresses towards environmental sustainability, there is a growing need to enhance the safety and health conditions for analysts. Consequently, the incorporation of chemometrics into environmentally friendly analytical methods represents a promising approach. Favipiravir, cefixime, and moxifloxacin hydrochloride have been currently used in COVID-19 treatment. In this study, we develop spectrophotometric methods depending on chemometric based models to measure the levels of favipiravir, cefixime, and moxifloxacin hydrochloride in pharmaceutical preparations and spiked human plasma. It is challenging to determine favipiravir, cefixime, and moxifloxacin simultaneously because of overlap in their UV absorption spectra. Two advanced chemometric models, partial least square (PLS) and genetic algorithm (GA), have been developed to provide better predictive abilities in spectrophotometric determination of the drugs under study. The described models were created using a five-level, three-factor experimental design. The outcomes of the models have been thoroughly assessed and interpreted, and a statistical comparison with recognized values has been taken into consideration. The analytical eco-scale and the green analytical procedure index (GAPI) evaluation methods were also utilized to determine how environmentally friendly the mentioned models were. The outcomes demonstrated how well the models described complied with the environmental requirements.

Eco-friendly novel deconvoluted synchronous spectrofluorimetric approach for the determination of favipiravir, levodropropizine and moxifloxacin hydrochloride as an effective therapeutic combination for COVID-19; application in laboratory prepared mixtures and spiked human plasma

In this work, a green, fast, and simple synchronous spectrofluorimetric approach has been developed to simultaneously determine favipiravir, levodropropizine, and moxifloxacin hydrochloride as co-administered medications for COVID-19 treatment in pure form and spiked human plasma. The synchronous fluorescence spectroscopy technique to analyze the studied drugs at Δλ = 110 nm enabled the determination of levodropropizine at 360 nm. Then, applying Fourier Self-Deconvolution to each spectra to measure favipiravir and moxifloxacin hydrochloride at peak amplitudes of 431 nm and 479 nm, respectively, without any interference. Favipiravir, levodropropizine, and moxifloxacin hydrochloride could be sensitively determined using the described approach over concentration ranges of 20-300 ng/mL, 10-600 ng/mL, and 50-500 ng/mL, respectively. The method's validation was carried out effectively in accordance with guidelines recommended by the ICH. Finally, the Eco-scale and Green Analytical Procedure Index (GAPI) techniques have been used to evaluate the greenness of the proposed method.

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, remdesivir, and lopinavir: metabolites, degradation products and their analytical methods

Severe acute respiratory syndrome 2 (SARS-CoV-2) caused the emergence of the COVID-19 pandemic all over the world. Several studies have suggested that antiviral drugs such as favipiravir (FAV), remdesivir (RDV), and lopinavir (LPV) may potentially prevent the spread of the virus in the host cells and person-to-person transmission. Simultaneously with the widespread use of these drugs, their stability and action mechanism studies have also attracted the attention of many researchers. This review focuses on the action mechanism, metabolites and degradation products of these antiviral drugs (FAV, RDV and LPV) and demonstrates various methods for their quantification and discrimination in the different biological samples. Herein, the instrumental methods for analysis of the main form of drugs or their metabolite and degradation products are classified into two types: optical and chromatography methods which the last one in combination with various detectors provides a powerful method for routine and stability analyses. Some representative studies are reported in this review and the details of them are carefully explained. It is hoped that this review will be a good guideline study and provide a better understanding of these drugs from the aspects investigated in this study.

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.

Favipiravir treatment in non-severe COVID-19: promising results from multicenter propensity score-matched study (FAVICOV)

This study aimed to evaluate the efficacy of favipiravir (FPV) in preventing the development of severe COVID-19 in patients with mild-to-moderate symptoms. The study evaluated 1037 COVID-19 patients treated with FPV or standard treatment between April and September 2021, analyzed by propensity score matching. 149 patients were included in each arm after propensity score matching. The clinical outcomes showed no deterioration of the WHO clinical progression scale in the FPV group compared to the standard treatment group on day 5 (83.2% vs. 69.1%, p < 0.001). The WHO clinical progression scale also showed improvements on day 14 in the FPV group compared to the standard treatment group (66.4% vs. 46.3%, p < 0.001). The rates of oxygen supplementation and hospitalization were significantly lower in the FPV group compared to the standard treatment group (0% vs. 12.1% and 0.7% vs. 17.4%, respectively, p < 0.001 for both). There were no differences in adverse events between the two groups. The study highlights the effectiveness of FPV in preventing severe COVID-19 and hospitalization in patients with mild-to-moderate symptoms. The findings emphasize the importance of personalized treatment plans for COVID-19 patients, starting FPV treatment early, and adjusting dosages based on ethnicity and body weight.

The Real-World Clinical Outcomes of Favipiravir Treatment with Telemedicine Monitoring in Preventing Disease Progression in Mild to Moderate COVID-19 Patients; A Retrospective Cohort Study

Background: Favipiravir has complex pharmacokinetics, and varied efficacy has been reported in treating COVID-19. Telehealth and telemonitoring are disruptive challenges used for COVID-19 care during pandemics. Objective: This study aimed to assess the outcome of favipiravir treatment to prevent clinical deterioration in mild to moderate COVID-19 cases with adjunctive telemonitoring during the COVID-19 surge. Methods: This was a retrospective observational study of PCR-confirmed mild to moderate COVID-19 cases subjected to home isolation. Chest computed tomography (CT) was performed in all cases, and favipiravir was administrated. Results: This study involved 88 PCR-confirmed COVID-19 cases. In addition, 42/42 (100%) cases were Alpha variants. COVID-19 pneumonia was found in 71.5% of the cases, according to chest X-rays and chest CT on the first visit. Favipiravir started 4 days after symptoms, which was part of the standard of care. The 12.5% of the patients required supplemental oxygen and intensive care unit admission rate was 1.1%; 1.1% required mechanical ventilation, and the rate of all-cause mortality was 1.1%, with a value of 0% of severe COVID-19 deaths. All mild illness cases showed no clinical deterioration or requirement for supplemental oxygen. No significant deterioration in either obesity or diabetes mellitus was observed. Conclusions: Favipiravir treatment for mild to moderate COVID-19 cases in outpatient settings, coupled with telemonitoring, was both safe and effective in preventing clinical deterioration, including the need for oxygen supplementation. This approach proved valuable during surges of COVID-19 cases.

Safety and efficacy of four drug regimens versus standard-of-care for the treatment of symptomatic outpatients with COVID-19: A randomised, open-label, multi-arm, phase 2 clinical trial

Background

This exploratory study investigated four repurposed anti-infective drug regimens in outpatients with COVID-19.

Methods

This phase 2, single centre, randomised, open-label, clinical trial was conducted in South Africa between 3rd September 2020 and 23rd August 2021. Symptomatic outpatients aged 18–65 years, with RT-PCR confirmed SARS-CoV-2 infection were computer randomised (1:1:1:1:1) to standard-of-care (SOC) with paracetamol, or SOC plus artesunate-amodiaquine (ASAQ), pyronaridine-artesunate (PA), favipiravir plus nitazoxanide (FPV + NTZ), or sofosbuvir-daclatasvir (SOF-DCV). The primary endpoint was the incidence of viral clearance, i.e., the proportion of patients with a negative SARS-CoV-2 RT-PCR on day 7, compared to SOC using a log-binomial model in the modified intention-to-treat (mITT) population.

Findings

The mITT population included 186 patients: mean age (SD) 34.9 (10.3) years, body weight 78.2 (17.1) kg. Day 7 SARS-CoV-2 clearance rates (n/N; risk ratio [95% CI]) were: SOC 34.2% (13/38), ASAQ 38.5% (15/39; 0.80 [0.44, 1.47]), PA 30.3% (10/33; 0.69 [0.37, 1.29]), FPV + NTZ 27.0% (10/37; 0.60 [0.31, 1.18]) and SOF-DCV 23.5% (8/34; 0.47 [0.22, 1.00]). Three lower respiratory tract infections occurred (PA 6.1% [2/33]; SOF-DCV 2.9% [1/34]); two required hospitalisation (PA, SOF-DCV). There were no deaths. Adverse events occurred in 55.3% (105/190) of patients, including one serious adverse event (pancytopenia; FPV + NTZ).

Interpretation

There was no statistical difference in viral clearance for any regimen compared to SOC. All treatments were well tolerated.

Funding

10.13039/501100004167Medicines for Malaria Venture, with funding from the UK Foreign, Commonwealth and Development Office, within the Covid-19 Therapeutics Accelerator in partnership with 10.13039/100004440Wellcome, the 10.13039/100000865Bill and Melinda Gates Foundation, and Mastercard.