Synthesis and Anti-Influenza Virus Effects of Novel Substituted Polycyclic Pyridone Derivatives Modified from Baloxavir.

In this work, a series of novel substituted polycyclic pyridone derivatives were designed and synthesized as potent anti-influenza agents. The cytopathic effect (CPE) assay and cytotoxicity assay indicated that all of the compounds possessed potent anti-influenza virus activity and relatively low cytotoxicity; some of them inhibited the replication of influenza A virus (IAV) at picomolar concentrations. Further studies revealed that, at a concentration of 3 nM, three compounds (10a, 10d, and 10g) could significantly reduce the M2 RNA amounts and M2 protein expression of IAV and inhibit the activity of RNA-dependent RNA polymerase (RdRp). Among them, (R)-12-(5H-dibenzo[a,d][7]annulen-5-yl)-7-hydroxy-3,4,12,12a-tetrahydro-1H-[1,4]oxazino[3,4-c]pyrido[2,1-f][1,2,4]triazine-6,8-dione (10a) was found to be a promising anti-influenza drug candidate with good human liver microsomal stability, as well as with better selectivity index and oral bioavailability than Baloxavir.

Kinetic degradation study for the first licensed anti-influenza polymerase inhibitor, baloxavir marboxil, using high-performance liquid chromatography-mass spectrometry.

The first licensed polymerase inhibitor, baloxavir marboxil was recently approved for the treatment of influenza A and B viruses. Furthermore, there is growing interest in testing the antiviral activity of baloxavir marboxil against Coronavirus. Despite its critical clinical value, there is no information on the degradation products, pathways, or kinetics of baloxavir marboxil under various stress conditions. In this study, a new high-performance liquid chromatography-ultraviolet detection method for accurately quantifying baloxavir marboxil in the presence of its degradation products was developed. A study of degradation kinetics revealed that acidic, thermal neutral, and photolytic degradation reactions have zero-order kinetics, whereas basic and oxidative degradation reactions have first-order kinetics. The structural characterization of baloxavir marboxil degradation products was performed by coupling the optimized high-performance liquid chromatography method to the triple-quadrupole tandem mass spectrometer. The proposed approach was validated according to the International Council for Harmonisation Q2 (R1) requirements for accuracy, precision, robustness, specificity, and linearity. The validated new method was successfully used to analyze baloxavir marboxil as raw material and its pharmaceutical dosage form, Xofluza.

Combination of baloxavir and oseltamivir for treatment of severe influenza infection in hematopoietic cell transplant recipients: a novel treatment strategy for a high-risk population.

Baloxavir, a cap-dependent endonuclease inhibitor, was recently approved for treatment of severe influenza infections. Combining baloxavir with oseltamivir has been proposed to increase the response rate. We report 2 hematopoietic cell transplant recipients with severe influenza infections who were treated with this combination and discuss possible reasons for their different responses.

Comparison of Antiviral Agents for Seasonal Influenza Outcomes in Healthy Adults and Children: A Systematic Review and Network Meta-analysis.

Importance: Antiviral treatment of influenza is recommended for patients with influenza-like illness during periods of community cocirculation of influenza viruses and SARS-CoV-2; however, questions remain about which treatment is associated with the best outcomes and fewest adverse events. Objective: To compare the efficacy and safety of neuraminidase inhibitors and the endonuclease inhibitor for the treatment of seasonal influenza among healthy adults and children. Data Sources: Medline, Embase, and the Cochrane Register of Clinical Trials were searched from inception to January 2020 (the last search was updated in October 2020). Study Selection: Included studies were randomized clinical trials conducted among patients of all ages with influenza treated with neuraminidase inhibitors (ie, oseltamivir, peramivir, zanamivir, or laninamivir) or an endonuclease inhibitor (ie, baloxavir) compared with other active agents or placebo. Data Extraction and Synthesis: Two investigators identified studies and independently abstracted data. Frequentist network meta-analyses were performed; relative ranking of agents was conducted using P-score probabilities. Quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations criteria. Data were analyzed in October 2020. Main Outcomes and Measures: The time to alleviation of influenza symptoms (TTAS), complications of influenza, and adverse events (total adverse events, nausea, and vomiting). Results: A total of 26 trials were identified that investigated antiviral drugs at high or low doses; these trials included 11 897 participants, among whom 6294 (52.9%) were men and the mean (SD) age was 32.5 (16.9) years. Of all treatments comparing with placebo in efficacy outcomes, high-quality evidence indicated that zanamivir was associated with the shortest TTAS (hazard ratio, 0.67; 95% CI, 0.58-0.77), while baloxavir was associated with the lowest risk of influenza-related complications (risk ratio [RR], 0.51; 95% CI, 0.32-0.80) based on moderate-quality evidence. In safety outcomes, baloxavir was associated with the lowest risk of total adverse events (RR, 0.84; 95% CI, 0.74-0.96) compared with placebo based on moderate-quality evidence. There was no strong evidence of associations with risk of nausea or vomiting among all comparisons, except for 75 mg oseltamivir, which was associated with greater occurrence of nausea (RR, 1.82; 95% CI, 1.38-2.41) and vomiting (RR, 1.88; 95% CI, 1.47-2.41). Conclusions and Relevance: In this systematic review and network meta-analysis, all 4 antiviral agents assessed were associated with shortening TTAS; zanamivir was associated with the shortest TTAS, and baloxavir was associated with reduced rate of influenza-related complications.

Influenza polymerase inhibitor resistance: Assessment of the current state of the art - A report of the isirv Antiviral group.

It is more than 20 years since the neuraminidase inhibitors, oseltamivir and zanamivir were approved for the treatment and prevention of influenza. Guidelines for global surveillance and methods for evaluating resistance were established initially by the Neuraminidase Inhibitor Susceptibility Network (NISN), which merged 10 years ago with the International Society for influenza and other Respiratory Virus Diseases (isirv) to become the isirv-Antiviral Group (isirv-AVG). With the ongoing development of new influenza polymerase inhibitors and recent approval of baloxavir marboxil, the isirv-AVG held a closed meeting in August 2019 to discuss the impact of resistance to these inhibitors. Following this meeting and review of the current literature, this article is intended to summarize current knowledge regarding the clinical impact of resistance to polymerase inhibitors and approaches for surveillance and methods for laboratory evaluation of resistance, both in vitro and in animal models. We highlight limitations and gaps in current knowledge and suggest some strategies for addressing these gaps, including the need for additional clinical studies of influenza antiviral drug combinations. Lessons learned from influenza resistance monitoring may also be helpful for establishing future drug susceptibility surveillance and testing for SARS-CoV-2.

Clinical efficacy of antiviral agents against coronavirus disease 2019: A systematic review of randomized controlled trials.

Despite aggressive efforts on containment measures for the coronavirus disease 2019 (COVID-19) pandemic around the world, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continuously spreading. Therefore, there is an urgent need for an effective antiviral agent. To date, considerable research has been conducted to develop different approaches to COVID-19 therapy. In addition to early observational studies, which could be limited by study design, small sample size, non-randomized design, or different timings of treatment, an increasing number of randomized controlled trials (RCTs) investigating the clinical efficacy and safety of antiviral agents are being carried out. This study reviews the updated findings of RCTs regarding the clinical efficacy of eight antiviral agents against COVID-19, including remdesivir, lopinavir/ritonavir, favipiravir, sofosbuvir/daclatasvir, sofosbuvir/ledipasvir, baloxavir, umifenovir, darunavir/cobicistat, and their combinations. Treatment with remdesivir could accelerate clinical improvement; however, it lacked additional survival benefits. Moreover, 5-day regimen of remdesivir might show adequate effectiveness in patients with mild to moderate COVID-19. Favipiravir was only marginally effective regarding clinical improvement and virological assessment based on the results of small RCTs. The present evidence suggests that sofosbuvir/daclatasvir may improve survival and clinical outcomes in patients with COVID-19. However, the sample sizes for analysis were relatively small, and all studies were exclusively conducted in Iran. Further larger RCTs in other countries are warranted to support these findings. In contrast, the present findings of limited RCTs did not indicate the use of lopinavir/ritonavir, sofosbuvir/ledipasvir, baloxavir, umifenovir, and darunavir/cobicistat in the treatment of patients hospitalized for COVID-19.

Clinical Outcomes and Plasma Concentrations of Baloxavir Marboxil and Favipiravir in COVID-19 Patients: An Exploratory Randomized, Controlled Trial.

BACKGROUND: Effective antiviral drugs for COVID-19 are still lacking. This study aims to evaluate the clinical outcomes and plasma concentrations of baloxavir acid and favipiravir in COVID-19 patients. METHODS: Favipiravir and baloxavir acid were evaluated for their antiviral activity against SARS-CoV-2 in vitro before the trial initiation. We conducted an exploratory trial with 3 arms involving hospitalized adult patients with COVID-19. Patients were randomized assigned in a 1:1:1 ratio into baloxavir marboxil group, favipiravir group, and control group. The primary outcome was the percentage of subjects with viral negative by Day 14 and the time from randomization to clinical improvement. Virus load reduction, blood drug concentration and clinical presentation were also observed. The trial was registered with Chinese Clinical Trial Registry (ChiCTR 2000029544). RESULTS: Baloxavir acid showed antiviral activity in vitro with the half-maximal effective concentration (EC50) of 5.48 µM comparable to arbidol and lopinavir, but favipiravir didn't demonstrate significant antiviral activity up to 100 µM. Thirty patients were enrolled. The percentage of patients who turned viral negative after 14-day treatment was 70%, 77%, and 100% in the baloxavir marboxil, favipiravir, and control group respectively, with the medians of time from randomization to clinical improvement was 14, 14 and 15 days, respectively. One reason for the lack of virological effect and clinical benefits may be due to insufficient concentrations of these drugs relative to their antiviral activities. One of the limitations of this study is the time from symptom onset to randomization, especially in the baloxavir marboxil and control groups, which is higher than the favipiravir group. CONCLUSIONS: Our findings could not prove a benefit of addition of either baloxavir marboxil or favipiravir under the trial dosages to the existing standard treatment.

Modeling mitigation of influenza epidemics by baloxavir.

Influenza viruses annually kill 290,000-650,000 people worldwide. Antivirals can reduce death tolls. Baloxavir, the recently approved influenza antiviral, inhibits initiation of viral mRNA synthesis, whereas oseltamivir, an older drug, inhibits release of virus progeny. Baloxavir blocks virus replication more rapidly and completely than oseltamivir, reducing the duration of infectiousness. Hence, early baloxavir treatment may indirectly prevent transmission. Here, we estimate impacts of ramping up and accelerating baloxavir treatment on population-level incidence using a new model that links viral load dynamics from clinical trial data to between-host transmission. We estimate that ~22 million infections and >6,000 deaths would have been averted in the 2017-2018 epidemic season by administering baloxavir to 30% of infected cases within 48 h after symptom onset. Treatment within 24 h would almost double the impact. Consequently, scaling up early baloxavir treatment would substantially reduce influenza morbidity and mortality every year. The development of antivirals against the SARS-CoV2 virus that function like baloxavir might similarly curtail transmission and save lives.

Baloxavir for the treatment of Influenza in allogeneic hematopoietic stem cell transplant recipients previously treated with oseltamivir.

BACKGROUND: Seasonal influenza causes significant morbidity and mortality in allogeneic stem cell transplant (SCT) recipients. In this population, influenza virus can replicate for prolonged periods, despite neuraminidase inhibitor treatment, leading to resistance and treatment failure. Baloxavir targets the influenza polymerase and may be an effective treatment option in these patients. METHODS: We used baloxavir to treat five allogeneic SCT recipients that were still symptomatic and shedding influenza virus after completing one or more treatment courses of oseltamivir and characterized the viral isolates before and during treatment. RESULTS: Two patients were infected with influenza A/H1pdm09 carrying a neuraminidase variant (H275Y) linked to oseltamivir resistance. Both these two patients were successfully treated with baloxavir. Of the three patients infected with wild-type influenza virus, two cleared the virus after baloxavir treatment, while the third patient developed the polymerase I38T variant linked to baloxavir resistance. CONCLUSIONS: Our data suggest that baloxavir treatment can be effective in treating neuraminidase inhibitor-resistant influenza in profoundly immunocompromised patients. Randomized clinical trials are needed to define the role of baloxavir alone and combined with oseltamivir for the treatment of influenza in SCT recipients and other immunocompromised populations.