Antiviral influenza treatments and hemorrhage-related adverse events in the United States Food and Drug Administration Adverse Event Reporting System (FAERS) database

STUDY OBJECTIVE

To determine whether there is a signal for gastrointestinal (GI) or intracranial (IC) hemorrhage associated with the use of antiviral medications for influenza in the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) database.

DESIGN

Disproportionality analysis.

DATA SOURCE

The FAERS database was searched using OpenVigil 2.1 to identify GI and IC hemorrhage events reported between 2004 and 2022.

MEASUREMENTS

Antiviral medications for influenza included the following: oseltamivir, zanamivir, peramivir, and baloxavir marboxil. Hemorrhage events were identified using Standardized Medical Dictionary for Regulatory Activities (MedDRA) Queries for GI and IC hemorrhages. Reporting odds ratios (RORs) were calculated to compare the occurrence of GI and IC hemorrhage events between antiviral drugs for influenza and (i) all other medications and (ii) antibiotics. RORs were also calculated for each of the individual antiviral medications.

MAIN RESULTS

A total of 245 cases of GI hemorrhage and 23 cases of IC hemorrhage were identified in association with four antivirals. In comparison with all other drugs, the RORs of GI hemorrhage for oseltamivir, zanamivir, peramivir, baloxavir, and all antivirals combined were 1.17, 0.62, 4.44, 2.53, and 1.22, respectively, indicating potential variations in GI hemorrhage risk among the antivirals. In contrast, in comparison with all other drugs, the RORs of IC hemorrhage for oseltamivir (0.44), zanamivir (0.16), baloxavir (0.44), and all antivirals combined (0.41) were less than 1.0 which is consistent with no elevated risk of IC hemorrhage.

CONCLUSION

In this study, some signals for GI hemorrhage were observed, particularly for peramivir and baloxavir marboxil. Further investigation is warranted to better understand and evaluate the potential risks of GI hemorrhage associated with antiviral treatments for influenza.

Antibiotic prescription for outpatients with influenza and subsequent hospitalisation: A cohort study using insurance data

Background

Whether prophylactic administration of antibiotics to patients with influenza reduces the hospitalisation risk is unknown. We aimed to examine the association between antibiotic prescription in outpatients with influenza infection and subsequent hospitalisation.

Methods

We conducted a cohort study using health insurance records of Japanese clinic and hospital visits between 2012 and 2016. Participants were outpatients (age, 0-74 years) with confirmed influenza infection who were prescribed anti-influenza medicine. The primary outcomes were the hospitalisation risk from all causes and pneumonia and the duration of hospitalisation due to pneumonia.

Results

We analysed 903,104 outpatient records with 2469 hospitalisations. The risk of hospitalisation was greater in outpatients prescribed anti-influenza medicine plus antibiotics (0.31% for all causes and 0.18% for pneumonia) than in those prescribed anti-influenza medicine only (0.27% and 0.17%, respectively). However, the risk of hospitalisation was significantly lower in patients prescribed peramivir and antibiotics than in those prescribed peramivir only. Patients who received add-on antibiotics had a significantly longer hospital stay (4.12 days) than those who received anti-influenza medicine only (3.77 days). In all age groups, the hospitalisation risk from pneumonia tended to be greater in those who received antibiotics than in those prescribed anti-influenza medicine only. However, among older patients (65-74 years), those provided add-on antibiotics had an average 5.24-day shorter hospitalisation due to pneumonia than those provided anti-influenza medicine only (not significant).

Conclusions

In outpatient cases of influenza, patients who are prescribed antibiotics added to antiviral medicines have a higher risk of hospitalisation and longer duration of hospitalisation due to pneumonia.

Influenza vaccine for 2023-2024

Annual vaccination in the US against influenza A and B viruses is recommended for everyone ≥6 months old without a contraindication.1,2 Influenza vaccines that are available in the US for the 2023-2024 season are listed in Table 2.

Antiviral Drugs in Influenza

Flu is a serious health, medical, and economic problem, but no therapy is yet available that has satisfactory results and reduces the occurrence of these problems. Nearly 20 years after the registration of the previous therapy, baloxavir marboxil, a drug with a new mechanism of action, recently appeared on the market. This is a promising step in the fight against the influenza virus. This article presents the possibilities of using all available antiviral drugs specific for influenza A and B. We compare all currently recommended anti-influenza medications, considering their mechanisms of action, administration, indications, target groups, effectiveness, and safety profiles. We demonstrate that baloxavir marboxil presents a similar safety and efficacy profile to those of drugs already used in the treatment of influenza. Further research on combination therapy is highly recommended and may have promising results.

Impact of the R292K Mutation on Influenza A (H7N9) Virus Resistance towards Peramivir: A Molecular Dynamics Perspective

In March 2013, a novel avian influenza A (H7N9) virus emerged in China. By March 2021, it had infected more than 1500 people, raising concerns regarding its epidemic potential. Similar to the highly pathogenic H5N1 virus, the H7N9 virus causes severe pneumonia and acute respiratory distress syndrome in most patients. Moreover, genetic analysis showed that this avian H7N9 virus carries human adaptation markers in the hemagglutinin and polymerase basic 2 (PB2) genes associated with cross-species transmissibility. Clinical studies showed that a single mutation, neuraminidase (NA) R292K (N2 numbering), induces resistance to peramivir in the highly pathogenic H7N9 influenza A viruses. Therefore, to evaluate the risk for human public health and understand the possible source of drug resistance, we assessed the impact of the NA-R292K mutation on avian H7N9 virus resistance towards peramivir using various molecular dynamics approaches. We observed that the single point mutation led to a distorted peramivir orientation in the enzyme active site which, in turn, perturbed the inhibitor's binding. The R292K mutation induced a decrease in the interaction among neighboring amino acid residues when compared to its wild-type counterpart, as shown by the high degree of fluctuations in the radius of gyration. MM/GBSA calculations revealed that the mutation caused a decrease in the drug binding affinity by 17.28 kcal/mol when compared to the that for the wild-type enzyme. The mutation caused a distortion of hydrogen bond-mediated interactions with peramivir and increased the accessibility of water molecules around the K292 mutated residue.

Intermolecular Mechanism and Dynamic Investigation of Avian Influenza H7N9 Virus' Susceptibility to E119V-Substituted Peramivir-Neuraminidase Complex

The H7N9 virus attaches itself to the human cell receptor protein containing the polysaccharide that terminates with sialic acid. The mutation of neuraminidase at residue E119 has been explored experimentally. However, there is no adequate information on the substitution with E119V in peramivir at the intermolecular level. Therefore, a good knowledge of the interatomic interactions is a prerequisite in understanding its transmission mode and subsequent effective inhibitions of the sialic acid receptor cleavage by neuraminidase. Herein, we investigated the mechanism and dynamism on the susceptibility of the E119V mutation on the peramivir–neuraminidase complex relative to the wildtype complex at the intermolecular level. This study aims to investigate the impact of the 119V substitution on the neuraminidase–peramivir complex and unveil the residues responsible for the complex conformations. We employed molecular dynamic (MD) simulations and extensive post-MD analyses in the study. These extensive computational investigations were carried out on the wildtype and the E119V mutant complex of the protein for holistic insights in unveiling the effects of this mutation on the binding affinity and the conformational terrain of peramivir–neuraminidase E119V mutation. The calculated total binding energy (ΔG_bind) for the peramivir wildtype is −49.09 ± 0.13 kcal/mol, while the E119V mutant is −58.55 ± 0.15 kcal/mol. The increase in binding energy (9.46 kcal/mol) is consistent with other post-MD analyses results, confirming that E119V substitution confers a higher degree of stability on the protein complex. This study promises to proffer contributory insight and additional knowledge that would enhance future drug designs and help in the fight targeted at controlling the avian influenza H7N9 virus. Therefore, we suggest that experimentalists collaborate with computational chemists for all investigations of this topic, as we have done in our previous studies.

Association between anaphylaxis and anti-influenza drug use: An analysis of the Japanese Adverse Drug Event Report database

We aimed to investigate the association between anaphylaxis and anti-influenza drug use using the Japanese Adverse Drug Event Report (JADER) database, a national spontaneous reporting database in Japan. We surveyed registered cases from the JADER database between April 2004 and November 2019. The target drugs were five anti-influenza drugs, namely oseltamivir, zanamivir, peramivir, laninamivir, and baloxavir. Adverse events associated with anaphylaxis, "anaphylactic reaction," "anaphylactic shock," "anaphylactoid reaction," and "anaphylactoid shock," were evaluated. The association between anaphylaxis and anti-influenza drug use was assessed by calculating the reporting odds ratio (ROR) and information component (IC) as a measure of disproportionality. Signals were considered positive if the lower limit of the 95% confidence interval (CI) of ROR was > 1, and that of IC was > 0. The number of anaphylaxis cases associated with anti-influenza drug use was 199 (0.9%). Signals were detected for inhaled laninamivir (ROR: 4.24 [95% CI: 3.06-5.88], IC: 1.83 [1.35-2.30]), intravenous peramivir (ROR: 2.97 [2.11-4.17], IC: 1.40 [0.90-1.89]), and oral baloxavir (ROR: 3.05 [2.22-4.18], IC: 1.44 [0.98-1.90]). Conversely, signals were not detected for oral oseltamivir or inhaled zanamivir. Although zanamivir and laninamivir were used as dry powder inhalers containing lactose as an additive, they differed in terms of signal detection. Our analysis indicated that the signal of anaphylaxis may varies based on the main component or dosage form of each anti-influenza drug. Appropriate use of these drugs is essential to prevent anaphylaxis and improve health status.

Neuraminidase inhibitors and single dose baloxavir are effective and safe in uncomplicated influenza: a meta-analysis of randomized controlled trials

BACKGROUND

Scarce evidence verifying the clinical impact of baloxavir on influenza complications is found.

METHODS

PubMed, Cochrane Library, and Web of Science databases were searched through December 2020. Randomized-controlled trials (RCT) that enrolled patients with laboratory-confirmed influenza receiving neuraminidase inhibitors (NAI) or baloxavir comparing to placebo were assessed. PROSPERO Registration-number: CRD42021226854.

RESULTS

Twenty-one RCTs (11,697 patients) were included. Antiviral administration significantly reduced time to clinical resolution (mean difference: -21.3 hours) and total influenza-related complications (OR:0.55, 95%CI: 0.42-0.73). Specifically, antivirals significantly decreased bronchitis (OR:0.54, 95%CI: 0.38-0.75), sinusitis (OR:0.51, 95%CI: 0.33-0.78), acute otitis media (OR:0.48, 95%CI: 0.30-0.77), and antibiotic prescription (OR:0.62; 95%CI: 0.48-0.80). A positive trend favored antivirals administration to reduce pneumonia (OR:0.47, 95%CI: 0.16-1.33), or hospitalization rates (OR:0.65; 95%CI: 0.34-1.24) compared to placebo, but did not reach statistical significance. Adverse events (AE) were reported in 11%, 8.9%, and 5.1% of NAIs, placebo and baloxavir recipients, respectively. Compared with NAIs, administration of baloxavir showed non-significantly reduced AEs (OR:0.74, 95%CI: 0.53-1.04).

CONCLUSIONS

Single-dose baloxavir and NAIs were superior to placebo to reduce complications in uncomplicated influenza, with 40% significant reduction in antibiotic prescription. Safety and efficacy of single-dose baloxavir were non-inferior to NAIs.

Improvement of respiratory symptoms and health-related quality of life with peramivir in influenza patients with chronic respiratory disease: Additional outcomes of a randomized, open-label study

BACKGROUND

To compare peramivir 300 mg single-dose, peramivir 600 mg repeat-dose, and oseltamivir effects on health-related quality of life, including respiratory symptoms and general conditions, time to symptom alleviation, time to fever resolution, incidence of exacerbations, and virus titer, in influenza patients with chronic respiratory disease.

METHODS

We report additional outcomes from a 2-week, multicenter, randomized, open-label study in Japan (UMIN000030118). Influenza patients with chronic respiratory disease received intravenous peramivir (300 mg single-dose [n = 66], 600 mg repeat-dose [600 mg/d of 2 consecutive days; n = 70]) or oral oseltamivir (75 mg twice daily, 5 days; n = 72). The principal endpoint of this analysis was change from baseline to Day 14 at each time point in Chronic Obstructive Pulmonary Disease Assessment Test (CAT) scores.

RESULTS

Both peramivir regimens reduced total CAT score at Day 3 more than oseltamivir (peramivir 600 mg vs oseltamivir, P = .0032; peramivir 300 mg vs oseltamivir, P = .0203). Cough/phlegm CAT scores were most improved with peramivir 600 mg. Median time to alleviation of three respiratory symptoms was longer with peramivir 600 mg (68.9 hours) than with peramivir 300 mg (50.6 hours, hazard ratio [HR] 1.57; P = .0191) and shorter with peramivir 300 mg than oseltamivir (78.8 hours, HR 0.62; P = .0141). Alleviation of seven influenza symptoms and fever resolution was shortest with peramivir 300 mg.

CONCLUSIONS

Rapid improvement in CAT score, including cough, and shorter time to alleviation of respiratory symptoms associated with peramivir is of potential benefit to patients with chronic respiratory disease.

Comparing intravenous peramivir with oral oseltamivir for patients with influenza: a meta-analysis of randomized controlled trials

BACKGROUND

The study was to compare the efficacy between IV peramivir and oral oseltamivir treatments in patients with influenza.

METHODS

The PubMed, EMBASE, Scopus, ClinicalTrials.gov, and Cochrane Library databases were searched for studies published before January 2020.

RESULTS

The meta-analysis was conducted to calculate the pooled effect size by using a random-effects model. Seven randomized controlled trials (RCTs) including 1,138 patients were reviewed. The incidence of total complications revealed no significant difference between 600 mg IV peramivir (P600) and 75 mg oral oseltamivir (O75) treatments (2.8% vs. 4.1%; risk ratio [RR] = 0.70; 95% confidence interval [CI]: 0.36-1.38). The incidence of pneumonia was not significantly different between the P600 and O75 treatment groups (2.2% vs. 2.7%; RR = 0.74; 95% CI: 0.37-1.51). Regarding the time to the alleviation of symptoms, no difference was found in P600 and O75 treatment (MD = -3.00; 95% CI: -11.07 to 5.06). The rate of fever clearance in 24 h and the time to fever resolution were not statistically different between the IV peramivir and oral oseltamivir treatments (at different dosages) groups.

CONCLUSIONS

The treatment of influenza with IV peramivir or oral oseltamivir had similar clinical efficacy.

Evaluation of Baloxavir Marboxil and Peramivir for the Treatment of High Pathogenicity Avian Influenza in Chickens

Control measures in the case of high pathogenicity avian influenza (HPAI) outbreaks in poultry include culling, surveillance, and biosecurity; wild birds in captivity may also be culled, although some rare bird species should be rescued for conservation. In this study, two anti-influenza drugs, baloxavir marboxil (BXM) and peramivir (PR), used in humans, were examined in treating HPAI in birds, using chickens as a model. Chickens were infected with H5N6 HPAI virus and were treated immediately or 24 h from challenge with 20 mg/kg BXM or PR twice a day for five days. As per our findings, BXM significantly reduced virus replication in organs and provided full protection to chickens compared with that induced by PR. In the 24-h-delayed treatment, neither drug completely inhibited virus replication nor ensured the survival of infected chickens. A single administration of 2.5 mg/kg of BXM was determined as the minimum dose required to fully protect chickens from HPAI virus; the concentration of baloxavir acid, the active form of BXM, in chicken blood at this dose was sufficient for a 48 h antiviral effect post-administration. Thus, these data can be a starting point for the use of BXM and PR in treating captive wild birds infected with HPAI virus.

Clinical Effectiveness of Intravenous Peramivir Compared With Oseltamivir in Patients With Severe Influenza A With Primary Viral Pneumonia: A Randomized Controlled Study

Background

High-quality evidence confirms that the clinical efficacy of peramivir in severe influenza patients with primary viral pneumonia is lacking. To optimize clinical medication, we evaluate the different efficacy between peramivir and oseltamivir in the treatment of severe influenza A with primary viral pneumonia.

Methods

A single-center, randomized, controlled trial was conducted during the Chinese influenza season from December 2018 to April 2019 in patients with severe influenza A with primary viral pneumonia. A total of 40 inpatients were enrolled and treated with either intravenous peramivir (300 mg, once daily for 5 days) or oral oseltamivir (75 mg, twice daily for 5 days).

Results

The duration of influenza virus nucleic acid positivity in the oseltamivir group and the peramivir group was 2.95 days and 2.80 days, respectively. The remission times of clinical symptoms in the oseltamivir group and the peramivir group were 3.90 days and 3.25 days, respectively. In addition, the remission time of cough symptoms in the peramivir group (63.89 hours) was shorter than that in the oseltamivir group (75.53 hours). There was no significant difference between these values (P > .05). The remission time of fever symptoms in the oseltamivir group was 23.67 hours, which was significantly longer than that in the peramivir group (12.32 hours) (P = .034).

Conclusions

Peramivir is no less effective than oseltamivir in the treatment of severe influenza A with primary viral pneumonia, and patients treated with peramivir had significantly shorter remission times of fever symptoms than those treated with oseltamivir.

Intravenous peramivir vs oral oseltamivir in high-risk emergency department patients with influenza: Results from a pilot randomized controlled study

Background

Peramivir offers a single‐dose intravenous (IV) treatment option for influenza (vs 5‐day oral dosing for oseltamivir). We sought to compare outcomes of emergency department (ED) patients at high risk for influenza complications treated with IV peramivir vs oral oseltamivir.

Methods

During the 2015‐16 and 2016‐17 influenza seasons, adult patients in two US EDs were randomized to either oral oseltamivir or IV peramivir treatment group. Eligibility included positive molecular influenza test; met CDC criteria for antiviral treatment; able to provide informed consent and agree to follow‐up assessment. Outcomes were measured by clinical end‐point indicators, including FLU‐PRO Score, Ordinal Scale, Patient Global Impression on Severity Score, and Karnofsky Performance Scale for 14 days. Non‐inferior t test was performed to assess comparative outcomes between the two groups.

Results

Five hundred and seventy‐five (68%) of 847 influenza‐positive patients were approached. Two hundred and eighty‐four met enrollment criteria and 179 were enrolled; of these 95 (53%) were randomized to peramivir, and 84 to oseltamivir. Average FLU‐PRO score at baseline was similar (peramivir: 2.67 vs oseltamivir: 2.52); the score decreased over time for both groups (day 5: peramivir: 1.71 vs oseltamivir: 1.62; day 10: peramivir: 1.48 vs oseltamivir: 1.37; day 14: peramivir: 1.40 vs oseltamivir: 1.33; all P < .05 for significantly non‐inferior). Influenza‐related complications were similar between two groups (All: peramivir: 31% vs oseltamivir: 21%, P > .05; pneumonia: peramivir: 11% vs oseltamivir: 14%, P > .05).

Conclusions

Clinical outcomes of influenza‐infected patients treated with single‐dose IV peramivir were comparable to those treated with oral oseltamivir, suggesting potential utility of peramivir for influenza‐infected patients in the ED.

In Vitro Characterization of Multidrug-Resistant Influenza A(H1N1)pdm09 Viruses Carrying a Dual Neuraminidase Mutation Isolated from Immunocompromised Patients

Influenza A(H1N1)pdm09 viruses carrying a dual neuraminidase (NA) substitution were isolated from immunocompromised patients after administration of one or more NA inhibitors. These mutant viruses possessed an H275Y/I223R, H275Y/I223K, or H275Y/G147R substitution in their NA and showed enhanced cross-resistance to oseltamivir and peramivir and reduced susceptibility to zanamivir compared to single H275Y mutant viruses. Baloxavir could be a treatment option against the multidrug-resistant viruses because these dual H275Y mutant viruses showed susceptibility to this drug. The G147R substitution appears to stabilize the NA structure, with the fitness of the H275Y/G147R mutant virus being similar or somewhat better than that of the wild-type virus. Since the multidrug-resistant viruses may be able to transmit between humans, surveillance of these viruses must continue to improve clinical management and to protect public health.

Reduced Prescription of Baloxavir After Suspected Prevalence of a Baloxavir-Resistant Influenza Virus Strain and the Emergence of SARS-CoV-2 in a Tertiary Hospital in Japan

Objective

The use of baloxavir, a new anti-influenza agent, began in Japan from the 2018 to 2019 season and became the focus of attention due to its efficient viral reduction ability; therefore, we should know the prescription changes of anti-influenza agents.

Methods

We analyzed the changes in the prescription of anti-influenza agents between the 2018-19 season and the 2019-20 season in our hospital.

Results

The share of baloxavir was 15%, while the shares of oseltamivir and laninamivir were 42% and 31%, respectively in the 2018-2019 season. However, in the 2019-20 season, the share of baloxavir and laninamivir was reduced to 3% and 17%, respectively, in contrast to an increase in the share of oseltamivir (66%). The total prescription of anti-influenza agents for patients decreased in the 2019-20 season (205 patients), compared with the 2018-19 season (509 patients).

Conclusion

These results suggest significant changes such as a reduction in the prescription of anti-influenza agents, especially baloxavir, likely due to the suspected prevalence of a baloxavir-resistant strain of influenza virus and the emergence of SARS-CoV-2 in Japan.

Effect of peramivir on respiratory symptom improvement in patients with influenza virus infection and pre-existing chronic respiratory disease: Findings of a randomized, open-label study

Background

The efficacy of neuraminidase inhibitors on improvement of respiratory symptoms triggered by influenza in patients with pre‐existing chronic respiratory diseases is unknown.

Methods

This 2‐week, randomized, open‐label study evaluated intravenous peramivir 600 mg on two consecutive days (peramivir‐repeat), peramivir 300 mg single dose (peramivir‐single), and oral oseltamivir 75 mg twice daily for 5 days in patients with confirmed influenza and chronic respiratory diseases. Patients recorded symptom scores daily. The primary endpoint of cumulative area of time vs symptoms (CATVS) was expressed as an index value of area under the curve vs time of the total score of cough, sore throat, and nasal congestion from baseline to 2 weeks.

Results

Of 214 randomized patients, 209 (56% female, 77% aged <65 years, 94% outpatients, 91% bronchial asthma, 62% influenza A) received ≥1 dose of study drug. Mean (standard deviation) CATVS was similar for peramivir‐repeat (782.78 [487.17]) vs peramivir‐single (717.35 [347.55]; P = .4371), and for peramivir‐repeat vs oseltamivir (856.34 [404.99]; P = 1.00). However, CATVS was significantly shorter for peramivir‐single vs oseltamivir, with an estimated treatment difference (TD) of −145.07 (95% confidence interval: −284.57, −5.56; P = .0416). In subgroup analyses, CATVS was significantly shorter for peramivir‐single vs oseltamivir among patients with influenza A (TD: −206.31 [−383.86, −28.76]; P = .0231), bronchial asthma (TD: −156.57 [−300.22, −12.92]; P = .0328), baseline respiratory severity score <5 (TD: −265.32 [−470.42, −60.21]; P = .0120), and age <65 (TD: −184.30 [−345.08, −23.52]; P = .0249).

Conclusions

In patients with chronic respiratory diseases, peramivir‐single was not significantly different from peramivir‐repeat and was more effective than oseltamivir at alleviating respiratory symptoms.

A Meta-Analysis Comparing the Efficacy and Safety of Peramivir with Other Neuraminidase Inhibitors for Influenza Treatment

Background and Objectives: This meta-analysis compared the efficacy and safety of peramivir compared to other neuraminidase inhibitors (NAIs). Materials and Methods: Data from PubMed, Embase, and Cochrane databases and ClinicalTrials.gov were searched until January 2019. Randomized controlled trials (RCTs) and observational studies (OSs) comparing peramivir with other NAIs for treating influenza were included. The Grading of Recommendations, Assessments, Development, and Evaluations (GRADE) system was used to judge the overall certainty of evidence; the result was moderate. The primary outcome was time to alleviation of symptoms. Twelve articles involving 2681 patients were included in this meta-analysis. We used a random-effect model to pool the effect size, which is expressed as the difference in means (MD), risk ratio (RR), and 95% confidence interval (CI). Results: Overall, peramivir was superior to other NAIs (MD = −11.214 hours, 95% CI: −19.119 to −3.310). The incidence of adverse events (RR = 1.023, 95% CI: 0.717 to 1.460) and serious adverse events (RR = 1.068, 95% CI: 0.702 to 1.625) in the peramivir group was similar to those in the oseltamivir group. In addition, peramivir had higher efficacy than each NAI alone. Conclusion: In conclusion, the efficacy of peramivir might be higher than that of other NAIs, and this agent is tolerated as well as other NAIs.

Reduced Susceptibility to Neuraminidase Inhibitors in Influenza B Isolate, Canada

We identified an influenza B isolate harboring a Gly407Ser neuraminidase substitution in an immunocompromised patient in Canada before antiviral therapy. This mutation mediated reduced susceptibility to oseltamivir, zanamivir, and peramivir, most likely by preventing interaction with the catalytic Arg374 residue. The potential emergence of such variants emphasizes the need for new antivirals.

Peramivir binding affinity with influenza A neuraminidase and research on its mutations using an induced-fit docking approach

Influenza A virus (IAV) has caused epidemic infections worldwide, with many strains resistant to inhibitors of a surface protein, neuraminidase (NA), due to point mutations on its structure. A novel NA inhibitor named peramivir was recently approved, but no exhaustive computational research regarding its binding affinity with wild-type and mutant NA has been conducted. In this study, a thorough investigation of IAV-NA PDB entries of 9 subtypes is described, providing a list of residues constituting the protein-ligand binding sites. The results of induced-fit docking approach point out key residues of wild-type NA participating in hydrogen bonds and/or ionic interactions with peramivir, among which Arg 368 is responsible for a peramivir-NA ionic interaction. Mutations on this residue greatly reduced the binding affinity of peramivir with NA, with 3 mutations R378Q, R378K and R378L (NA6) capable of deteriorating the docking performance of peramivir by over 50%. 200 compounds from 6-scaffolds were docked into these 3 mutant versions, revealing 18 compounds giving the most promising results. Among them, CMC-2012-7-1527-56 (benzoic acid scaffold, IC50 = 32 nM in inhibitory assays with IAV) is deemed the most potential inhibitor of mutant NA resisting both peramivir and zanamivir, and should be further investigated.

Peramivir for Influenza A and B Viral Infections: A Pharmacokinetic Case Series

Objective

To describe the peramivir (PRV) pharmacokinetics in critically ill children treated for influenza A or B viral infections.

Design

Retrospective electronic medical record review of prospectively collected data from critically ill children receiving peramivir for influenza A or B viral infections in the pediatric intensive care unit (PICU).

Setting

A 189‐bed, freestanding children's tertiary care teaching hospital in Philadelphia, PA.

Patients

Critically ill children admitted to the PICU who were infected with influenza between January 1, 2016 and March 31, 2018.

Interventions

None.

Results

Eleven patients, two females (18%) and nine males (82%), accounted for 24 peramivir samples for therapeutic drug management. The median age was 5 years (interquartile range 1.5–6.5 yrs) with a median weight of 16.4 kg (interquartile range 14–24 kg). Ten (91%) patients demonstrated a larger volume of distribution, 11 (100%) patients demonstrated an increase in clearance, and 11 (100%) patients demonstrated a shorter half‐life estimate as compared with the package insert and previous pediatric trial data for peramivir. Eight (73%) patients tested positive for a strain of influenza A and 3 (27%) patients tested positive for influenza B; 4 of 11 (36%) patients tested positive for multiple viruses. All patients had adjustments made to their dosing interval to a more frequent interval. Ten (91%) patients were adjusted to an every‐12‐hour regimen and 1 (9%) patient was adjusted to an every‐8‐hour regimen. No adverse events were associated with peramivir treatment.

Conclusion

The pharmacokinetics of PRV demonstrated in this PICU cohort differs in comparison to healthy pediatric and adult patients, and alterations to dosing regimens may be needed in PICU patients to achieve pharmacodynamic exposures. Additional investigations in the PICU population are needed to confirm these findings.

Key amino acid residues of neuraminidase involved in influenza A virus entry

Generally, influenza virus neuraminidase (NA) plays a critical role in the release stage of influenza virus. Recently, it has been found that NA may promote influenza virus to access the target cells. However, the mechanism remain unclear. Here, we reported that peramivir indeed possessed anti-influenza A virus (IAV) activity in the stage of viral entry. Importantly, we verified the critical residues of influenza NA involved in the viral entry. As a result, peramivir as an efficient NA inhibitor could suppress the initiation of IAV infection. Furthermore, mutational analysis showed NA might be associated with viral entry via amino acids residues R118, E119, D151, R152, W178, I222, E227, E276, R292 and R371. Our results demonstrated NA must contain the key amino acid residues can involve in IAV entry.

Neuraminidase inhibitors as a strategy for influenza treatment: pros, cons and future perspectives

Introduction: Influenza represents a major public health threat worldwide. Implementation of good personal health and hygiene habits, together with vaccination, is the most effective tools to reduce influenza burden both in community and in healthcare setting. However, achieving adequate vaccination rates is challenging, and vaccination does not always guarantee complete protection. Neuraminidase inhibitors represent an important measure to reduce the risk of influenza-related complications among high-risk patients developing influenza infection. Areas covered: Neuraminidase inhibitors have been proven to be safe and effective in reducing influenza severity, duration of symptoms, hospitalizations, and influenza-related-mortality. Here the authors review the available data on neuraminidase inhibitors, including the mechanism of action, pharmacokinetics, efficacy, safety and current indications for their use in clinical practice. Expert opinion: Although vaccination is the most effective tool to reduce influenza-associated morbidity and mortality, neuraminidase inhibitors represent an important option for the treatment of patients with influenza infection, particularly in high-risk categories. Moreover, antivirals play an important role in influenza prevention and prophylaxis in selected settings.

The effect of neuraminidase inhibitors on household transmission in Japanese patients with influenza A and B infection: A prospective, observational study

Background

The relative ability of neuraminidase inhibitors (NAIs) to reduce household influenza transmission when given to index patients is not established.

Objectives

To compare daily secondary infection rates (SIR) of influenza A (A/H1pdm and A/H3) and B in households of index patients treated with oseltamivir, zanamivir, laninamivir, or peramivir.

Patients/Methods

This Japanese, single‐center, prospective, observational study (UMIN‐CTR: UMIN000024650) enrolled index patients with confirmed influenza who were treated with an NAI during 6 influenza seasons (2010‐2016). Secondary infection patients were household members diagnosed with the same influenza subtype 1‐7 days after onset in the index patient. Daily SIR was calculated using a modified Reed‐Frost model. The rate of household members with secondary infection and proportion of households with any secondary infection were also calculated.

Results

Index patients with influenza A (n = 1146) or B (n = 661) were enrolled (~3400 total index and secondary patients). Daily SIR for all virus subtypes was highest when oseltamivir was used (eg, unadjusted estimate: type A, 1.47% vs 0.71%‐1.13%; type B, 1.30% vs 0.59%‐0.88%). Pairwise comparisons revealed significant differences in daily SIR between NAIs for influenza type A, type B, and subtype A/H3; for example, for type A, SIR was significantly higher with oseltamivir than with peramivir or zanamivir. The rate of household members with secondary infection and proportion of households with any secondary infection also varied between NAIs.

Conclusions

Neuraminidase inhibitors differed in their ability to reduce household influenza transmission; transmission was highest with oseltamivir. Physicians may consider effects on household transmission when deciding which NAI to prescribe.

Preparation and Evaluation of Oseltamivir Molecularly Imprinted Polymer Silica Gel as Liquid Chromatography Stationary Phase

To improve the chromatographic performance of an oseltamivir (OS) molecularly imprinted polymer (MIP), silica gel coated with an MIP layer for OS (OSMIP@silica gel) was prepared by the surface molecular imprinting technology on the supporter of porous silica gel microspheres. A nonimprinted polymer with the silica gel (NIP@silica gel) was also prepared for comparison. The obtained particles were characterized through FT–IR, scanning electron microscopy, specific surface area analysis, and porosity measurements. The results indicated that the polymer was successfully synthesized and revealed the structural differences between imprinted and nonimprinted polymers. The results of static adsorption experiments showed that adsorption quantity of the OSMIP@silica gel for OS was higher than that for NIP@silica gel, and the OSMIP@silica gel had two kinds of affinity sites for OS but the NIP@silica gel had one. The chromatographic performance of the OSMIP@silica gel column had significant improvement. The imprinting factor of the OSMIP@silica gel column for OS was 1.64. Furthermore, the OSMIP@silica gel column showed good affinity and selectivity for template OS and another neuraminidase inhibitor, peramivir, but not for quinocetone. These results indicated that the prepared OSMIP could be used to simulate the activity center of neuraminidase, and the OSMIP@silica gel column could be also employed in future studies to search for more active neuraminidase inhibitor analogues from traditional Chinese herbs.

Vogt-Koyanagi-Harada Disease Associated with Influenza A Virus Infection

We herein report a case of a 31-year-old Japanese man who simultaneously had a positive influenza A virus antigen test result and Vogt-Koyanagi-Harada disease (VKHD), demonstrated by both diffuse multiple early hyperfluorescent points on fluorescein fundus photography and serous retinal detachments on optical coherence tomography. He had meningitis. It was difficult to determine whether the main cause of meningitis was influenza A or VKHD. After initial treatment with peramivir for influenza A and then methylprednisolone pulse with subsequent corticosteroid therapy for VKHD, his symptoms improved gradually. These findings suggest that influenza A virus infection contributes to the onset or exacerbation of VKHD.

HPLC-MS/MS analysis of peramivir in rat plasma: Elimination of matrix effect using the phospholipid-removal solid-phase extraction method

A simple HPLC-MS/MS method has been developed for the determination of peramivir in rat plasma in the present study. The analytes were separated on a C₁₈ column (50 × 2.1 mm, 1.7 μm) and a triple-quadrupole mass spectrometer equipped with an electrospray ionization source was applied for the detection. A phospholipid-free cartridge solid-phase extraction was used to pretreat the plasma and eliminate the endogenous phospholipid. The in-source collision-induced dissociation approach showed that this pretreatment could result in negligible ion suppression from the extracted sample and could produce cleaner samples when compared with the protein precipitation. The method was linear over the concentration range of 0.12-1200.0 ng/mL for peramivir. The method was validated and successfully applied to a pharmacokinetic study after peramivir was orally and intravenously administered to Sprague-Dawley rats.

Comparison of Efficacy of Intravenous Peramivir and Oral Oseltamivir for the Treatment of Influenza: Systematic Review and Meta-Analysis

PURPOSE

Peramivir is the first intravenously administered neuramidase inhibitor for immediate delivery of an effective single-dose treatment in patients with influenza. However, limited data are available on intravenous (IV) peramivir treatment compared to oral oseltamivir for these patients.

MATERIALS AND METHODS

With a systematic review and meta-analysis, we compared the efficacy of IV peramivir with oral oseltamivir for treatment of patients with seasonal influenza. MEDLINE, EMBASE, and Cochrane Central Register were searched for relevant clinical trials.

RESULTS

A total of seven trials [two randomized controlled trials (RCTs) and five non-randomized observational trials] involving 1676 patients were finally analyzed. The total number of peramivir- and oseltamivir-treated patients was 956 and 720, respectively. Overall, the time to alleviation of fever was lower in the peramivir-treated group compared with the oseltamivir-treated group [mean difference (MD), -7.17 hours; 95% confidence interval (CI) -11.00 to -3.34]. Especially, pooled analysis of observational studies (n=4) and studies of outpatients (n=4) demonstrated the superiority of the peramivir-treated group (MD, -7.83 hours; 95% CI -11.81 to -3.84 and MD, -7.71 hours; 95% CI -11.61 to -3.80, respectively). Mortality, length of hospital stay, change in virus titer 48 hours after admission, and the incidence of adverse events in these patients were not significantly different between the two groups.

CONCLUSION

IV peramivir therapy might reduce the time to alleviation of fever in comparison with oral oseltamivir therapy in patients with influenza; however, we could not draw clear conclusions from a meta-analysis because of the few RCTs available and methodological limitations.

Efficacy and Safety of Intravenous Peramivir Compared With Oseltamivir in High-Risk Patients Infected With Influenza A and B Viruses: A Multicenter Randomized Controlled Study

Background

Clinical studies comparing the different neuraminidase inhibitors for treatment of at-risk patients with influenza have not been performed. To optimize such treatments, we assessed the efficacy and safety of intravenous peramivir compared with oral oseltamivir in treating seasonal influenza A or B virus infection.

Methods

A multicenter, randomized, controlled clinical trial was conducted from December 2012 to May 2014 in high-risk patients infected with seasonal influenza. A total of 92 adult inpatients and outpatients with high risk factors (HRFs) were treated by either a single intravenous infusion of peramivir (600 mg) or oral administration of oseltamivir (75 mg, twice per day for 5 days).

Results

The median times to clinical stability (time to reach <37°C) were 40.0 hours (95% confidence interval [CI] = 23.3–64.5) and 37.8 hours (95% CI = 26.3–45.3) in the peramivir and oseltamivir groups, respectively; these values did not reveal a significant difference. The virus titer and change of mean total symptom scores decreased similarly with both treatments. Results of step-wise regression suggested that virus type was a significantly effective prognostic factor with respect to illness resolution. Adverse events (AEs) with peramivir and oseltamivir occurred in 2.2% (n = 1/46) and 13.0% (n = 6/46) of patients, respectively. The severity of AEs was mild in all cases except 2 patients who showed pneumonia or COPD aggravation; both were in the oseltamivir group.

Conclusions

Intravenous peramivir was effective based on the result of direct comparison with oral oseltamivir. Thus our data show that peramivir is a useful option for the treatment of influenza-infected patients with HRFs.

The pharmacological management of severe influenza infection - 'existing and emerging therapies'

INTRODUCTION

Over the last century several influenza outbreaks have traversed the globe, most recently the influenza A(H1N1) 2009 pandemic. On each occasion, a highly contagious, virulent pathogen has emerged, leading to significant morbidity and mortality amongst those affected. Areas covered: Early antiviral therapy and supportive care is the mainstay of treatment. Treatment should be started as soon as possible and not delayed for the results of diagnostic testing. Whilst oseltamivir is still the first choice, in case of treatment failure, oseltamivir resistance should be considered, particularly in immunosuppressed patients. Here we review the antivirals currently used for management of influenza and explore a number of investigational agents that may emerge as effective antivirals including parenteral agents, combination antiviral therapy and novel agents in order to adequately target influenza virulence. Expert Commentary: New tools for rapid diagnosis and susceptible strains will help if a patient is not improving because of a resistant strain or an inadequate immune response. Further randomized control trials will be conducted to investigate the use of new antivirals and co-adjuvant therapies that will help to elucidate the process of immune modulation, particularly in immunocompetent patients.

Peramivir: A Novel Intravenous Neuraminidase Inhibitor for Treatment of Acute Influenza Infections

Peramivir is a novel cyclopentane neuraminidase inhibitor of influenza virus. It was approved by the Food and Drug Administration in December 2014 for treatment of acute uncomplicated influenza in patients 18 years and older. For several months prior to approval, the drug was made clinically available under Emergency Use authorization during the 2009 H1N1 influenza pandemic. Peramivir is highly effective against human influenza A and B isolates as well as emerging influenza virus strains with pandemic potential. Clinical trials demonstrated that the drug is well-tolerated in adult and pediatric populations. Adverse events are generally mild to moderate and similar in frequency to patients receiving placebo. Common side effects include gastrointestinal disorders and decreased neutrophil counts but are self-limiting. Peramivir is administered as a single-dose via the intravenous route providing a valuable therapeutic alternative for critically ill patients or those unable to tolerate other administration routes. Successful clinical trials and post-marketing data in pediatric populations in Japan support the safety and efficacy of peramivir in this population where administration of other antivirals might not be feasible.

Efficacy of oseltamivir-peramivir combination therapy compared to oseltamivir monotherapy for Influenza A (H7N9) infection: a retrospective study

BACKGROUND

Since the novel H7N9 avian influenza outbreak occurred in China in 2013, neuraminidase inhibitors (NAIs) such as oseltamivir and peramivir have been used as first-line drugs to treat the influenza virus infection. This study aimed to compare the efficacy of oseltamivir-peramivir combination therapy versus oseltamivir monotherapy.

METHODS

A retrospective study of 82 H7N9 confirmed patients was conducted by reviewing medical charts at the First Affiliated Hospital of ZheJiang University in China from April 1, 2013 to Feb 28, 2014. The patients' clinical information was collected systematically, and we compared the virology and clinical data between oseltamivir monotherapy group (43 patients) and oseltamivir-peramivir combination group (39 patients).

RESULTS

The median duration from NAIs administration to H7N9 virus-negative in oseltamivir monotherapy group and oseltamivir-peramivir combination group was 6.50 and 7.00 days (p >0.05), respectively. The median decline of Day 2 to Day 0 (initiation of NAIs therapy) viral load was 0.00 and 0.69 log10 copies/μl (p >0.05) respectively in the monotherapy vs. combination therapy groups. The incidence of new Acute Respiratory Distress Syndrome during NAI administration was 63.89 and 77.78 % (p >0.05); while the mortality rates were 25.58 and 43.59 % (p >0.05) in the oseltamivir group vs. oseltamivir-peramivir group.

CONCLUSIONS

Our results suggest that in adults with H7N9 virus infection, the use of oseltamivir-peramivir combination therapy was not superior to oseltamivir monotherapy.

Optimizing antiviral therapy for influenza: understanding the evidence

Influenza is an important cause of annual epidemics of respiratory viral infection associated with significant morbidity and mortality. Three classes of drugs, the M2 ion channel, neuraminidase and RNA-dependent RNA polymerase inhibitors, are approved for the prevention and treatment of influenza. Due to widespread resistance to the class, the M2 ion channel inhibitors are not recommended currently for therapy. The only polymerase inhibitor, favipiravir, is approved only in Japan and its use is highly restricted. Despite significant data to support the early use of the neuraminidase inhibitors, their use in all patient populations is suboptimal. The data to support the early use of neuraminidase inhibitors will be reviewed, as will current data on the utilization rates in ambulatory and hospitalized populations.

Drug susceptibility profile and pathogenicity of H7N9 influenza virus (Anhui1 lineage) with R292K substitution

Neuraminidase inhibitors (NAIs) are the only available licensed therapeutics against human H7N9 influenza virus infections. The emergence of NAI-resistant variants of H7N9viruses with an NA R292K mutation poses a therapeutic challenge. A comprehensive understanding of the susceptibility of these viruses to clinically available NAIs, non-NAIs and their combinations is crucial for effective treatment. In this study, by using limited serial passage and plaque purification, an R292K variant of the Anhui1 lineage was isolated from a patient with clinical evidence of resistance to oseltamivir. In vitro and cell-based assays confirmed a high level of resistance conferred by the R292K mutation to oseltamivir carboxylate and a moderate level of resistance to zanamivir and peramivir. Non-NAI antivirals, such as T-705, ribavirin and NT-300, efficiently inhibited both the variant and the wild-type in cell-based assays. A combination of NAIs and non-NAIs did not exhibit a marked synergistic effect against the R292K variant. However, the combination of two non-NAIs (T-705 and ribavirin) exhibited significant synergism against the mutant virus. In experimentally infected mice, the variant showed delayed onset of symptoms, a reduced viral load and attenuated lethality compared with the wild-type. Our study suggested non-NAIs should be tested clinically for H7N9 patients with a sustained high viral load. Possible drug combination regimens, such as T-705 plus ribavirin, should be further tested in animal models. The pathogenicity and transmissibility of the R292K H7N9 variant should be further assessed with genetically well-characterized pairs of viruses and, most-desirably, with competitive fitness experiments.

Pharmacokinetics of peramivir after single intravenous doses in healthy Chinese subjects

1.The aim of the study was to evaluate the pharmacokinetics of peramivir after single intravenous (i.v.) doses in healthy Chinese subjects. 2.In a cross-over study, 12 subjects were given 300 and 600 mg peramivir by i.v. infusion. Blood and urine samples were collected at 17 designated time points and 7 designated intervals up to 36 h post-dose. Plasma and urine concentrations of peramivir were quantified by LC-MS/MS. 3.After single i.v. doses of 300 and 600 mg peramivir, Cmax and AUC0-t of peramivir were 21.4 ± 3.7, 41.1 ± 5.3 mgċL(-1) and 55.90 ± 10.62, 112.1 ± 13.2 mgċh L(-1), respectively. Cmax and AUC increased in proportion to the dose. Within 12 h, accumulative urinary recoveries of peramivir after single i.v. doses of 300 and 600 mg peramivir were 84.31 ± 11.75% and 88.10 ± 7.39%, respectively. 4.In healthy Chinese subjects, peramivir displayed linear pharmacokinetics in the range of 300-600 mg, and was primarily excreted via urine as unchanged drug.

Compounds with anti-influenza activity: present and future of strategies for the optimal treatment and management of influenza. Part I: Influenza life-cycle and currently available drugs

Influenza is a contagious respiratory acute viral disease characterized by a short incubation period, high fever and respiratory and systemic symptoms. The burden of influenza is very heavy. Indeed, the World Health Organization (WHO) estimates that annual epidemics affect 5-15% of the world's population, causing up to 4-5 million severe cases and from 250,000 to 500,000 deaths. In order to design anti-influenza molecules and compounds, it is important to understand the complex replication cycle of the influenza virus. Replication is achieved through various stages. First, the virus must engage the sialic acid receptors present on the free surface of the cells of the respiratory tract. The virus can then enter the cells by different routes (clathrin-mediated endocytosis or CME, caveolae-dependent endocytosis or CDE, clathrin-caveolae-independent endocytosis, or macropinocytosis). CME is the most usual pathway; the virus is internalized into an endosomal compartment, from which it must emerge in order to release its nucleic acid into the cytosol. The ribonucleoprotein must then reach the nucleus in order to begin the process of translation of its genes and to transcribe and replicate its nucleic acid. Subsequently, the RNA segments, surrounded by the nucleoproteins, must migrate to the cell membrane in order to enable viral assembly. Finally, the virus must be freed to invade other cells of the respiratory tract. All this is achieved through a synchronized action of molecules that perform multiple enzymatic and catalytic reactions, currently known only in part, and for which many inhibitory or competitive molecules have been studied. Some of these studies have led to the development of drugs that have been approved, such as Amantadine, Rimantadine, Oseltamivir, Zanamivir, Peramivir, Laninamivir, Ribavirin and Arbidol. This review focuses on the influenza life-cycle and on the currently available drugs, while potential antiviral compounds for the prevention and treatment of influenza are considered in the subsequent review.

Characterization of drug-resistant influenza A(H7N9) variants isolated from an oseltamivir-treated patient in Taiwan

BACKGROUND

Patients contracting influenza A(H7N9) infection often developed severe disease causing respiratory failure. Neuraminidase (NA) inhibitors (NAIs) are the primary option for treatment, but information on drug-resistance markers for influenza A(H7N9) is limited.

METHODS

Four NA variants of A/Taiwan/1/2013(H7N9) virus containing a single substitution (NA-E119V, NA-I222K, NA-I222R, or NA-R292K) recovered from an oseltamivir-treated patient were tested for NAI susceptibility in vitro; their replicative fitness was evaluated in cell culture, mice, and ferrets.

RESULTS

NA-R292K led to highly reduced inhibition by oseltamivir and peramivir, while NA-E119V, NA-I222K, and NA-I222R caused reduced inhibition by oseltamivir. Mice infected with any virus showed severe clinical signs with high mortality rates. NA-I222K virus was the most virulent in mice, whereas virus lacking NA change (NA-WT) and NA-R292K virus seemed the least virulent. Sequence analysis suggests that PB2-S714N increased virulence of NA-I222K virus in mice; NS1-K126R, alone or in combination with PB2-V227M, produced contrasting effects in NA-WT and NA-R292K viruses. In ferrets, all viruses replicated to high titers in the upper respiratory tract but produced only mild illness. NA-R292K virus, showed reduced replicative fitness in this animal model.

CONCLUSIONS

Our data highlight challenges in assessment of the replicative fitness of H7N9 NA variants that emerged in NAI-treated patients.