Optimization, and biological evaluation of 3-O-ß-chacotriosyl betulinic acid amide derivatives as novel small-molecule Omicron.

SARS-CoV-2 Omicron viruses possess a high antigenic shift, and the approved anti-SARS-CoV-2 drugs are extremely limited, which makes the development of new antiviral drugs for the clinical treatment and prevention of SARS-CoV-2 outbreaks imperative. We have previously discovered a new series of markedly potent small-molecule inhibitors of SARS-CoV-2 virus entry, exampled by the hit compound 2. Here, we report a further study of bioisosteric replacement of the eater linker at the C-17 position of 2 with a variety of aromatic amine moieties, followed by a focused structure-activity relationship study, leading to the discovery of a series of novel 3-O-ß-chacotriosyl BA amide derivatives as small-molecule Omicron fusion inhibitors with improved potency and selectivity index. Particularly, our medicinal chemistry efforts have resulted in a potent, and efficacious lead compound S-10 with appreciable pharmacokinetic properties, which exhibited broad-spectrum potency against Omicron and other variants with EC50 values ranging from 0.82 to 5.45 µM. Mutagenesis studies confirmed that inhibition of Omicron viral entry was mediated by the direct interaction with S in the prefusion state. These results reveal that S-10 is suitable for further optimization as Omicron fusion inhibitors, with the potential to be developed as therapeutic agents for the treatment and control of SARS-CoV-2 ant its variants infections.

Pharmacogenetics-guided dalcetrapib therapy after an acute coronary syndrome: the dal-GenE trial.

AIMS: In a retrospective analysis of dal-Outcomes, the effect of dalcetrapib on cardiovascular events was influenced by an adenylate cyclase type 9 (ADCY9) gene polymorphism. The dal-GenE study was conducted to test this pharmacogenetic hypothesis. METHODS AND RESULTS: dal-GenE was a double-blind trial in patients with an acute coronary syndrome within 1-3 months and the AA genotype at variant rs1967309 in the ADCY9 gene. A total of 6147 patients were randomly assigned to receive dalcetrapib 600 mg or placebo daily. The primary endpoint was the time from randomization to first occurrence of cardiovascular death, resuscitated cardiac arrest, non-fatal myocardial infarction, or non-fatal stroke. After a median follow-up of 39.9 months, the primary endpoint occurred in 292 (9.5%) of 3071 patients in the dalcetrapib group and 327 (10.6%) of 3076 patients in the placebo group [hazard ratio 0.88; 95% confidence interval (CI) 0.75-1.03; P = 0.12]. The hazard ratios for the components of the primary endpoint were 0.79 (95% CI 0.65-0.96) for myocardial infarction, 0.92 (95% CI 0.64-1.33) for stroke, 1.21 (95% CI 0.91-1.60) for death from cardiovascular causes, and 2.33 (95% CI 0.60-9.02) for resuscitated cardiac arrest. In a pre-specified on-treatment sensitivity analysis, the primary endpoint event rate was 7.8% (236/3015) in the dalcetrapib group and 9.3% (282/3031) in the placebo group (hazard ratio 0.83; 95% CI 0.70-0.98). CONCLUSION: Dalcetrapib did not significantly reduce the risk of occurrence of the primary endpoint of ischaemic cardiovascular events at end of study. A new trial would be needed to test the pharmacogenetic hypothesis that dalcetrapib improves the prognosis of patients with the AA genotype. CLINICAL TRIAL REGISTRATION: Trial registration dal-GenE ClinicalTrials.gov Identifier: NCT02525939.

Timeline of changes in spike conformational dynamics in emergent SARS-CoV-2 variants reveal progressive stabilization of trimer stalk with altered NTD dynamics.

SARS-CoV-2 emergent variants are characterized by increased viral fitness and each shows multiple mutations predominantly localized to the spike (S) protein. Here, amide hydrogen/deuterium exchange mass spectrometry has been applied to track changes in S dynamics from multiple SARS-CoV-2 variants. Our results highlight large differences across variants at two loci with impacts on S dynamics and stability. A significant enhancement in stabilization first occurred with the emergence of D614G S followed by smaller, progressive stabilization in subsequent variants. Stabilization preceded altered dynamics in the N-terminal domain, wherein Omicron BA.1 S showed the largest magnitude increases relative to other preceding variants. Changes in stabilization and dynamics resulting from S mutations detail the evolutionary trajectory of S in emerging variants. These carry major implications for SARS-CoV-2 viral fitness and offer new insights into variant-specific therapeutic development.

Favipiravir Use in Kidney Transplant Recipients with COVID-19: A Single-Center Experience.

OBJECTIVES: Kidney transplant recipients are among the high-risk groups for severe COVID-19. To date, no specific antiviral agent has proved uniformly effective against SARS-CoV-2. Favipiravir, the recommended drug by the Turkish Ministry of Health, was uniformly supplied to all patients diagnosed with COVID-19 by a positive nasopharyngeal swab polymerase chain reaction test. The aim of our study was to retrospectively compare our kidney transplant recipients treated with favipiravir who developed COVID-19 infection versus those not treated with favipiravir during the clinical course of the disease, with a special emphasis on the occurrence of side effects and adverse events. MATERIALS AND METHODS: We included 37 consecutive kidney transplant recipients with a median age of 46 years (62.2% women). Recipients included 8 with deceased donors and 29 with living related donors; median posttransplant survival was 8.0 years (IQR, 5.5-12.5 years). RESULTS: Twenty-six patients (70.3%) received favipiravir, and 11 (29.7%) did not. There were no statistically significant differences between the groups for baseline demographic characteristics and clinical and laboratory data, except that the favipiravir-treated patients were older and had a higher requirement of oxygen treatment. There were no statistically significant differences between the 2 groups for the course and outcome of COVID-19 infection with regard to adverse side effects/events associated with favipiravir. Laboratory data at baseline, day 7, and day 30 were also comparable between the groups. CONCLUSIONS: Although the efficacy of favipiravir for treatment of COVID-19 infection remains controversial, favipiravir is safe for kidney transplant recipients.

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

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

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.

Triterpenic Acid Amides as Potential Inhibitors of the SARS-CoV-2 Main Protease.

Although the incidence and mortality of SARS-CoV-2 infection has been declining during the pandemic, the problem related to designing novel antiviral drugs that could effectively resist viruses in the future remains relevant. As part of our continued search for chemical compounds that are capable of exerting an antiviral effect against the SARS-CoV-2 virus, we studied the ability of triterpenic acid amides to inhibit the SARS-CoV-2 main protease. Molecular modeling suggested that the compounds are able to bind to the active site of the main protease via non-covalent interactions. The FRET-based enzyme assay was used to reveal that compounds 1e and 1b can inhibit the SARS-CoV-2 main protease at micromolar concentrations.

Favipiravir in the Treatment of Outpatient COVID-19: A Multicenter, Randomized, Triple-Blind, Placebo-Controlled Clinical Trial.

BACKGROUND: Finding effective outpatient treatments to prevent COVID-19 progression and hospitalization is necessary and is helpful in managing limited hospital resources. Repurposing previously existing treatments is highly desirable. In this study, we evaluate the efficacy of Favipiravir in the prevention of hospitalization in symptomatic COVID-19 patients who were not eligible for hospitalization. METHODS: This study was a triple-blind randomized controlled trial conducted between 5 December 2020 and 31 March 2021 in three outpatient centers in Isfahan, Iran. Patients in the intervention group received Favipiravir 1600 mg daily for five days, and the control group received a placebo. Our primary outcome was the proportion of hospitalized participants from day 0 to day 28. The outcome was assessed on days 3, 7, 14, 21, and 28 through phone calls. RESULTS: Seventy-seven patients were randomly allocated to Favipiravir and placebo groups. There was no significant difference between groups considering baseline characteristics. During the study period, 10.5% of patients in the Favipiravir group and 5.1% of patients in the placebo group were hospitalized, but there was no significant difference between them (p-value = 0.3). No adverse event was reported in the treatment group. CONCLUSIONS: Our study shows that Favipiravir did not reduce the hospitalization rate of mild to moderate COVID-19 patients in outpatient settings.

A favipiravir-induced angioedema and urticaria in a COVID-19 patient.

Although favipiravir is a promising drug for coronavirus disease 2019, some adverse effects, including skin lesions, have been reported. A 56-year-old female who was prescribed favipiravir by a filiation team following a positive severe acute respiratory syndrome coronavirus 2 polymerase chain reaction test presented to our hospital. After examination, favipiravir and paracetamol were prescribed. She represented to the hospital with facial swelling and itchy rashes on her forearm. Angioedema and urticaria were diagnosed. Favipiravir was discontinued. Steroid and antihistaminic therapy were administered for angioedema. To our knowledge, this is the first reported case of favipiravir-induced angioedema and urticaria in Turkey.

Conventional and synchronous spectrofluorometric determination of the recently administered drugs for treatment of COVID-19 favipiravir and apixaban.

COVID-19 is a fast-spreading pandemic that is caused by SARS-CoV-2 viral pathogen. Combination therapy of the antiviral favipiravir and the anticoagulant apixaban is one of the efficient treatment regimens. Therefore, development of novel and sensitive methods for simultaneous analysis of such combination is highly advantageous. Herein, two eco-friendly, simple, rapid, and cost-effective spectrofluorometric methods were evolved for the estimation of favipiravir and apixaban in pharmaceutical and biological matrices. Method I was based on analysis of favipiravir and apixaban by the first-order derivative of the conventional fluorescence spectra obtained after excitation at 300 nm, where favipiravir and apixaban were detected at 468.8 and 432.0 nm, respectively. Method II relied on dual scan synchronous spectrofluorometry, in which favipiravir was determined at 364 nm using Δλ = 60 nm while apixaban was analyzed at 274 nm using Δλ = 200 nm. Method optimization was performed for selecting the optimum conditions at which maximum sensitivity and selectivity were obtained. This report is the first one that describes simultaneous analysis of favipiravir and apixaban by synchronous spectrofluorometry. The developed methods were successfully applied to evaluate favipiravir and apixaban in spiked human plasma and in pharmaceutical dosages with high %recoveries and low RSD.

A systematic review and Bayesian network meta-analysis for comparative safety assessment of favipiravir interventions in hospitalized COVID-19 patients.

INTRODUCTION: COVID-19 is a coronavirus-based infectious illness that was first detected at the end of 2019 in Wuhan, China. The novel virus induces severe acute respiratory syndrome (SARS-CoV-2) and has spread globally, resulting in an ongoing pandemic. There is still a lack of evidence for direct comparison of favipiravir therapy. Network meta-analysis (NMA), may incorporate direct and indirect comparisons in a pooled computation while depending on strong assumptions and premises. This study provides evidence-based recommendations on the safety of currently used clinical pharmacological treatments compared to favipiravir for COVID-19 patients. METHODOLOGY: We conducted a systematic review and Bayesian NMA. We searched the primary databases and clinical trials center for reports of short-term, randomized controlled trials (RCTs) of favipiravir for COVID-19 treatment. The primary endpoints here considered were any adverse events observed or reported during the treatment cycle with estimates of odds ratio (OR) and 95% confidence interval (CI), until November 6, 2021. RESULTS: Between January 2020 and July 2021, 908 individuals were randomly assigned to one of the seven active prescription medication regimens or placebo in this study, generating seven direct comparisons on 12 data points. The safety of favipiravir over the four clinically efficacious monotherapies or combinations including tocilizumab, arbidol, lopinavir + ritonavir, and chloroquine remained unknown due to the lack of a significant difference and the limited sample size. CONCLUSIONS: Overall, comparative rankings could assist doctors and guideline developers in decision-making. We have also concluded that the safety of favipiravir requires further attention.

Virtual Screening and Quantum Chemistry Analysis for SARS-CoV-2 RNA-Dependent RNA Polymerase Using the ChEMBL Database: Reproduction of the Remdesivir-RTP and Favipiravir-RTP Binding Modes Obtained from Cryo-EM Experiments with High Binding Affinity.

The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified as the pathogenic cause of coronavirus disease 2019 (COVID-19). The RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 is a potential target for the treatment of COVID-19. An RdRp complex:dsRNA structure suitable for docking simulations was prepared using a cryo-electron microscopy (cryo-EM) structure (PDB ID: 7AAP; resolution, 2.60 Å) that was reported recently. Structural refinement was performed using energy calculations. Structure-based virtual screening was performed using the ChEMBL database. Through 1,838,257 screenings, 249 drugs (37 approved, 93 clinical, and 119 preclinical drugs) were predicted to exhibit a high binding affinity for the RdRp complex:dsRNA. Nine nucleoside triphosphate analogs with anti-viral activity were included among these hit drugs, and among them, remdesivir-ribonucleoside triphosphate and favipiravir-ribonucleoside triphosphate adopted a similar docking mode as that observed in the cryo-EM structure. Additional docking simulations for the predicted compounds with high binding affinity for the RdRp complex:dsRNA suggested that 184 bioactive compounds could be anti-SARS-CoV-2 drug candidates. The hit bioactive compounds mainly consisted of a typical noncovalent major groove binder for dsRNA. Three-layer ONIOM (MP2/6-31G:AM1:AMBER) geometry optimization calculations and frequency analyses (MP2/6-31G:AMBER) were performed to estimate the binding free energy of a representative bioactive compound obtained from the docking simulation, and the fragment molecular orbital calculation at the MP2/6-31G level of theory was subsequently performed for analyzing the detailed interactions. The procedure used in this study represents a possible strategy for discovering anti-SARS-CoV-2 drugs from drug libraries that could significantly shorten the clinical development period for drug repositioning.

Identification of Drug Combination Therapies for SARS-CoV-2: A Molecular Dynamics Simulations Approach.

Purpose: The development of effective treatments for coronavirus infectious disease 19 (COVID-19) caused by SARS-Coronavirus-2 was hindered by the little data available about this virus at the start of the pandemic. Drug repurposing provides a good strategy to explore approved drugs' possible SARS-CoV-2 antiviral activity. Moreover, drug synergism is essential in antiviral treatment due to improved efficacy and reduced toxicity. In this work, we studied the effect of approved and investigational drugs on one of SARS-CoV-2 essential proteins, the main protease (Mpro), in search of antiviral treatments and/or drug combinations. Methods: Different possible druggable sites of Mpro were identified and screened against an in-house library of more than 4000 chemical compounds. Molecular dynamics simulations were carried out to explore conformational changes induced by different ligands' binding. Subsequently, the inhibitory effect of the identified compounds and the suggested drug combinations on the Mpro were established using a 3CL protease (SARS-CoV-2) assay kit. Results: Three potential inhibitors in three different binding sites were identified; favipiravir, cefixime, and carvedilol. Molecular dynamics simulations predicted the synergistic effect of two drug combinations: favipiravir/cefixime, and favipiravir/carvedilol. The in vitro inhibitory effect of the predicted drug combinations was established on this enzyme. Conclusion: In this work, we could study one of the promising SARS-CoV-2 viral protein targets in searching for treatments for COVID-19. The inhibitory effect of several drugs on Mpro was established in silico and in vitro assays. Molecular dynamics simulations showed promising results in predicting the synergistic effect of drug combinations.

Ultramicronized Palmitoylethanolamide and Luteolin Supplement Combined with Olfactory Training to Treat Post-COVID-19 Olfactory Impairment: A Multi-Center Double-Blinded Randomized Placebo- Controlled Clinical Trial.

BACKGROUND: Olfactory training is the only evidence-based treatment for post-viral olfactory dysfunction. Smell disorders after SARS-CoV-2 infection have been attributed to neuroinflammatory events within the olfactory bulb and the central nervous system. Therefore, targeting neuroinflammation is one potential strategy for promoting recovery from post-COVID-19 chronic olfactory dysfunction. Palmitoylethanolamide and luteolin (PEA-LUT) are candidate antiinflammatory/ neuroprotective agents. OBJECTIVE: To investigate recovery of olfactory function in patients treated with PEA-LUT oral supplements plus olfactory training versus olfactory training plus placebo. METHODS: Multicenter double-blinded randomized placebo-controlled clinical trial was held. Eligible subjects had prior COVID-19 and persistent olfactory impairment >6 months after follow-up SARS-CoV-2 negative testing, without prior history of olfactory dysfunction or other sinonasal disorders. Participants were randomized to daily oral supplementation with ultramicronized PEA-LUT 770 mg plus olfactory training (intervention group) or olfactory training with placebo (control). Sniffin' Sticks assessments were used to test the patients at baseline and 90 days. RESULTS: A total of 185 patients, including intervention (130) and control (55) were enrolled. The intervention group showed significantly greater improvement in olfactory threshold, discrimination, and identification scores compared to controls (p=0.0001). Overall, 92% of patients in the intervention group improved versus 42% of controls. Magnitude of recovery was significantly greater in the intervention group versus control (12.8 + 8.2 versus mean 3.2 + 3), with >10-fold higher prevalence of anosmia in control versus intervention groups at the 90-day endpoint. CONCLUSION: Among individuals with olfactory dysfunction post-COVID-19, combining PEA-LUT with olfactory training resulted in greater recovery of smell than olfactory training alone.

Palmitoylethanolamide Reduces Proinflammatory Markers in Unvaccinated Adults Recently Diagnosed with COVID-19: A Randomized Controlled Trial.

BACKGROUND: Inflammation is at the core of many chronic conditions and exacerbates infectious conditions, including the severity of coronavirus disease 2019 (COVID-19) infections. OBJECTIVES: This study aimed to examine the effects of a novel food supplement, palmitoylethanolamide (PEA), specifically Levagen+, as compared with a placebo on proinflammatory biomarkers in adults recently diagnosed with COVID-19 who were unvaccinated and nonhospitalized. METHODS: This study was a double-blind randomized placebo-controlled trial conducted October 2020-March 2021 (clinicaltrials.gov: NCT04912921). Participants aged 19-53 y were unvaccinated and recently infected with COVID-19 as indicated by a positive test result per RT-PCR or antigen test, and they reported to the test site following diagnosis as allowed by the CDC's return-to-work policy. Participants were stratified by age, sex, and BMI and randomly assigned by coin toss to receive 600 mg Levagen+ twice daily (LEV) or placebo tablets twice daily (CON) for 4 wk. At baseline and week 4, participants completed health histories, 24-h dietary recalls, anthropometrics, and nonfasting blood sampling. The primary outcomes were the 4-wk change between groups for IL-6, C-reactive protein, ferritin, intercellular adhesion molecule 1, soluble P-selectin (sP-selectin), and neutrophil/lymphocyte ratio. Multiple linear regression models were utilized to assess treatment effects on outcomes, adjusting for covariates. RESULTS: A total of 60 participants completed the study (LEV: n = 30; CON: n = 30). After 4 wk of supplementation, sP-selectin (ß = -11.5; 95% CI: -19.8, -3.15; P = 0.0078), IL-1ß (ß = -22.9; 95% CI: -42.4, -3.40; P = 0.0222), and IL-2 (ß = -1.73; 95% CI: -3.45, -0.065; P = 0.0492) concentrations were significantly reduced in the LEV group compared with the CON group. CONCLUSIONS: Inflammatory mechanisms are crucial to optimal resolution of infectious conditions, yet unchecked secretion of inflammatory mediators can promote the dysregulated immune response implicated in COVID-19 complications. Overall, PEA supplementation produced anti-inflammatory effects in individuals recently diagnosed with COVID-19 who were nonhospitalized.

Efficacy of Early Treatment With Favipiravir on Disease Progression Among High-Risk Patients With Coronavirus Disease 2019 (COVID-19): A Randomized, Open-Label Clinical Trial.

BACKGROUND: The role of favipiravir in preventing disease progression in coronavirus disease 2019 (COVID-19) remains uncertain. We aimed to determine its effect in preventing disease progression from nonhypoxia to hypoxia among high-risk COVID-19 patients. METHODS: This was an open-label, randomized clinical trial conducted at 14 public hospitals across Malaysia (February-July 2021) among 500 symptomatic, RT-PCR-confirmed COVID-19 patients, aged ≥50 years with ≥1 comorbidity, and hospitalized within first 7 days of illness. Patients were randomized 1:1 to favipiravir plus standard care or standard care alone. Favipiravir was administered at 1800 mg 2×/day on day 1 followed by 800 mg 2×/day until day 5. The primary endpoint was rate of clinical progression from nonhypoxia to hypoxia. Secondary outcomes included rates of mechanical ventilation, intensive care unit (ICU) admission, and in-hospital mortality. RESULTS: Of 500 patients randomized (mean [SD] age, 62.5 [8.0] years; 258 women [51.6%]; 251 [50.2%] had COVID-19 pneumonia), 487 (97.4%) patients completed the trial. Clinical progression to hypoxia occurred in 46 (18.4%) patients on favipiravir plus standard care and 37 (14.8%) on standard care alone (OR, 1.30; 95% CI: .81-2.09; P = .28). All 3 prespecified secondary endpoints were similar between both groups. Mechanical ventilation occurred in 6 (2.4%) vs 5 (2.0%) (OR, 1.20; 95% CI: .36-4.23; P = .76), ICU admission in 13 (5.2%) vs 12 (4.8%) (OR, 1.09; 95% CI: .48-2.47; P = .84), and in-hospital mortality in 5 (2.0%) vs 0 (OR, 12.54; 95% CI: .76-207.84; P = .08) patients. CONCLUSIONS: Among COVID-19 patients at high risk of disease progression, early treatment with oral favipiravir did not prevent their disease progression from nonhypoxia to hypoxia. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov (NCT04818320).

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.