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The neuraminidase (NA) of influenza A and B viruses plays a distinct role in viral replication and has a highly conserved catalytic site. Numerous sialic (neuraminic) acid analogs that competitively bind to the NA active site and potently inhibit enzyme activity have been synthesized and tested. Four NA inhibitors are now licensed in various parts of the world (zanamivir, oseltamivir, peramivir, and laninamivir) to treat influenza A and B infections. NA changes, naturally occurring or acquired under selective pressure, have been shown to reduce drug binding, thereby affecting the effectiveness of NA inhibitors. Drug resistance and other drawbacks have prompted the search for the next-generation NA-targeting therapeutics. One of the promising approaches is the identification of monoclonal antibodies (mAbs) targeting the conserved NA epitopes. Anti-NA mAbs demonstrate Fab-based antiviral activity supplemented with Fc-mediated immune effector functions. Antiviral Fc-conjugates offer another cutting-edge strategy that is based on a multimodal mechanism of action. These novel antiviral agents are composed of a small-molecule NA inhibitor and an Fc-region that simultaneously engages the immune system. The significant advancements made in recent years further support the value of NA as an attractive target for the antiviral development.

BACKGROUND Neuraminidase inhibitor-associated acute hemorrhagic colitis is rare. We report a case of ischemic enterocolitis that was likely caused by laninamivir. CASE SUMMARY A 54-year-old female patient with influenza type A was administered 40 mg of laninamivir via inhalation once. On the same day, the patient experienced bloody stools and lower abdominal pain. A contrast-enhanced abdominal computed tomography showed edema-like changes from the descending colon to the sigmoid colon, which suggested ischemic enterocolitis. CONCLUSION We treated a patient with ischemic enterocolitis caused by laninamivir, a rare but similar symptom following the administration of oseltamivir.

Background Baloxavir marboxil (baloxavir) is a single-dose, oral antiinfluenza drug with a novel mechanism of action. We compared the incidence of hospitalization in patients treated with baloxavir vs neuraminidase inhibitors. Methods In this retrospective, observational, cohort study, we used real-world patient data extracted from a Japanese health insurance claims database. The enrollment period was 1 October 2018 to 17 April 2019. On day 1, eligible patients (N = 339 007) received baloxavir, oseltamivir, zanamivir, or laninamivir. Baseline characteristics were standardized using the inverse probability of treatment weighting method. The primary end point was the incidence of hospitalization (days 2–14). Secondary end points included antibacterial use, secondary pneumonia, and additional antiinfluenza drug use. Results Compared with the baloxavir group, the incidence of hospitalization was greater in the oseltamivir group (risk ratio [RR] and 95% confidence interval [CI], 1.41 [1.00–2.00]; risk difference [RD] and 95% CI, 0.06 [.01–.12]) and zanamivir group (RR, 1.85 [1.23–2.78]; RD, 0.11 [.02–.20]). Oseltamivir-treated patients were less likely to require antibacterials than baloxavir-treated patients (RR, 0.87 [.82–.91]). However, oseltamivir-treated patients were more likely to be hospitalized with antibacterials (RR, 1.70 [1.21–2.38]) or antibacterial injection (RR, 1.67 [1.17–2.38]) than baloxavir-treated patients (post hoc analysis). Compared with baloxavir-treated patients, additional antiinfluenza drug use was greater in oseltamivir-, zanamivir-, and laninamivir-treated patients (RR, 1.51 [1.05–2.18], 2.84 [2.04–3.96], and 1.68 [1.35–2.10], respectively). Conclusions Baloxavir is an efficacious antiinfluenza treatment that may reduce hospitalization compared with oseltamivir and zanamivir. Clinical Trials Registration University hospital Medical Information Network Clinical Trials Registry (UMIN000038159)., Baloxavir marboxil is a single-dose oral antiinfluenza drug with a novel mechanism of action. This real-world data study indicates that baloxavir marboxil may reduce hospitalization after influenza outpatient treatment compared with neuraminidase inhibitor treatment.

A 16-year-old female patient had influenza and was treated by inhalation of an anti-influenza agent. However, two days later, she showed slight dyspnea, and massive atelectasis of the left lung with hypoxia was found. She was admitted to our hospital (Day 0) and started on antibiotics and steroids, but the atelectasis was worsend on Day 3. Therefore, bronchoscopy was performed on Day 5. After the pus in the left bronchus was removed, the atelectasis was significantly improved. Atelectasis after influenza may be a rare, but critical complication, and bronchoscopy should be considered to release the obstructive lesions.

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.

Baloxavir marboxil (baloxavir) is a single-dose antiviral which was previously found to be a cost-effective alternative to laninamivir in otherwise healthy adults in Japan. This study aimed at investigating the cost-effectiveness of baloxavir versus laninamivir in patients with influenza at high risk for complications.A decision tree was utilized to estimate costs and health gains associated with the use of antivirals. A lifetime horizon was applied to capture the long-term impact of influenza complications, and other events with associated costs and health outcomes were accounted for one influenza season. The study population was stratified into three categories: adolescents and non-elderly adults with high-risk conditions (HRC), elderly without other HRC, and elderly with other HRC. The cost-effectiveness was assessed from a public healthcare payer's perspective. The duration of influenza symptoms, probabilities of complications and probabilities of adverse events were obtained from a clinical trial and network meta-analysis. The costs of influenza and adverse events management were derived from the JammNet claims database. Utility values were informed by the clinical trial data and literature. Sensitivity analyses were also performed.The baloxavir strategy was associated with higher costs (+¥144) and higher quality-adjusted life-years (QALYs) in adults with HRC, elderly without HRC and elderly with HRC (+0.00078, +0.00183 and +0.00350 respectively). The overall incremental cost/QALY for baloxavir versus laninamivir was ¥68,855, which was below the willingness-to-pay threshold of ¥5 million/QALY gained. Key drivers of the model results were the probability of pneumonia and bronchitis. The probability of baloxavir being cost-effective was 72%.This study suggests that influenza treatment with baloxavir is cost-effective compared with laninamivir in the adult high-risk population in Japan.

Background Pharmacoeconomic studies have been less performed in Japan. The objective of this study was to clarify which neuraminidase inhibitor (NI; oseltamivir, zanamivir, laninamivir, and peramivir) is most cost-effective in an adult outpatient setting in Japan. Objective To clarify which neuraminidase inhibitor (NI; oseltamivir, zanamivir, laninamivir, and peramivir) is most cost-effective in an adult outpatient setting in Japan. Methods Cost-effectiveness analysis was constructed from the healthcare payer’s perspective. A decision tree model was constructed with probabilities from relevant randomized controlled trials. Costs included medical costs and drug prices. Medical costs were obtained from the medical fee schedule table (2016 version). We also applied authorized medication costs. Outcomes of effectiveness were measured using EQ-5D-3L questionnaires for adult patients who had experienced influenza virus infections previously. Time horizon was 14 days in this study. Results Cost-effectiveness ratios for oseltamivir, zanamivir, laninamivir, and peramivir were 393 674 Yen/quality-adjusted life year (QALY; US$3883.41/QALY), 408 241 (US$4027.10), 407 980 (US$4024.53), and 444 264 (US$4382.45), respectively. The cost-effectiveness analysis base-case analysis revealed oseltamivir as the most cost-effective NI. Zanamivir was dominated. Incremental cost effectiveness ratio (ICER) for laninamivir and peramivir were 1 129 459 Yen/QALY (US$11 141.58/QALY) and 1 287 118 (US$12 696.81), respectively. One-way sensitivity analyses revealed that minimum ICERs for laninamivir based on “quality of life (QOL) values (95% confidence interval)” was −596 850 Yen/QALY (US−$5887.64/QALY) owing to high cost and less effective. Also, maximum ICER for peramivir based on“QOL values” was 14 717 518 Yen/QALY (US$145 181.32/QALY); a value more than the 5 000 000 Yen/QALY threshold. Conclusions The study results reveal oseltamivir as the most cost-effective NI for the treatment of influenza virus infection in an adult outpatient setting. Our findings may provide decision makers with scientific evidence for clinical and economic evaluation to achieve optimal therapeutic outcomes.

Background Baloxavir marboxil (baloxavir) is a new oral antiviral for influenza types A and B. Objectives To determine the cost-effectiveness of baloxavir versus laninamivir in otherwise healthy (OwH) adults in Japan. Methods A decision tree was utilized to describe the course of influenza and predict associated costs and quality-adjusted life-years (QALYs) over one year by antiviral. Costs were valued from the public healthcare payer perspective, including influenza test, antiviral acquisition, other medications, physician visits, other outpatient costs associated with influenza or drug-related adverse events (DRAEs), and hospitalizations. Resource utilization and unit costs were obtained from the analysis of the JammNet claims database. Health state utilities were obtained from a clinical trial of baloxavir and previous models, and were driven by influenza symptoms, DRAEs, and complications caused by influenza. Sensitivity analyses were also performed. Results The total payer expenditure per patient for baloxavir versus laninamivir was ¥9383 versus ¥9132. The additional acquisition costs of baloxavir were partly offset by the DRAE costs avoided. Baloxavir showed a small gain in QALYs versus laninamivir and the incremental cost per QALY gained (¥2,231,260) was lower than the considered willingness-to-pay threshold (¥5,000,000/QALY). Key model drivers were the probability of DRAEs and the duration of symptoms. The probability of baloxavir being cost-effective was 64%. Conclusion This cost-effectiveness study on baloxavir suggests that it would be cost-effective compared to laninamivir in OwH adults in Japan. Further studies are needed in different settings such as high-risk population and with different comparators.

The novel anti-influenza virus agent baloxavir marboxil is a selective inhibitor of an influenza cap-dependent endonuclease. Although a single oral dose in tablet form of baloxavir marboxil is expected to improve drug compliance and rapidly reduce viral titers for pediatric patients with influenza, there is a concern that baloxavir marboxil-resistant influenza A variants could be generated. In this study, we investigated the frequency of prescription and pharmacy revisits for baloxavir marboxil at an outpatient clinic compared with that of neuraminidase inhibitors in pediatric patients with influenza. A total of 475 pediatric patients who were infected with the influenza virus visited the pharmacy between December 2019 and March 2020. Baloxavir marboxil (n = 149), oseltamivir (n = 161) and laninamivir (n = 162) were mainly prescribed and only a few patients were treated with peramivir (n = 2) or zanamivir (n = 1). Baloxavir marboxil-, oseltamivir- and laninamivir-treated pediatric patients were enrolled, and a log-rank test showed that the revisits of pediatric patients who were taking baloxavir marboxil was lower than those for oseltamivir (p

Baloxavir marboxil (baloxavir) is the first cap-dependent endonuclease inhibitor being studied for the treatment of influenza in single oral dosing regimen. This network meta-analysis (NMA) evaluated the efficacy and safety of baloxavir compared to other antivirals for influenza in otherwise healthy patients.A systematic literature review was performed on 14 November 2016 in Medline, Embase, CENTRAL, and ICHUSHI to identify randomized controlled trials assessing antivirals for influenza. A NMA including 22 trials was performed to compare the efficacy and safety of baloxavir with other antivirals.The time to alleviation of all symptoms was significantly shorter for baloxavir compared to zanamivir (difference in median time 19.96 h; 95% CrI [3.23, 39.07]). The time to cessation of viral shedding was significantly shorter for baloxavir than zanamivir and oseltamivir (47.00 h; 95% CrI [28.18, 73.86] and 56.03 h [33.74, 87.86], respectively). The mean decline in virus titer from baseline to 24 h was significantly greater for baloxavir than for the other drugs. Other differences in efficacy outcomes were not significant. No significant differences were found between baloxavir and the other antivirals for safety, except total drug-related adverse events where baloxavir demonstrated a decrease compared to oseltamivir and laninamivir.The NMA suggests that baloxavir demonstrated better or similar efficacy results compared to other antivirals with a comparable safety profile. Baloxavir led to a significant decrease in viral titer versus zanamivir, oseltamivir and peramivir and decreased viral shedding versus zanamivir and oseltamivir.Цель. Балоксавир марбоксил (балоксавир) первый ингибитор кэп-зависимой эндонуклеазы, который изучается на предмет его использования для лечения гриппа по схеме: однократный прием внутрь. В данном сетевом метаанализе (СМА) проведена оценка эффективности и безопасности балоксавира в сравнении с другими противовирусными препаратами при лечении гриппа у пациентов без факторов риска. Методы. Систематический обзор литературы проведен на 14 ноября 2016 г. в базах Medline, Embase, CENTRAL и ICHUSHI с целью отбора рандомизированных контролируемых исследований противовирусных препаратов, применяемых для лечения гриппа. СМА, включавший 22 исследования, выполнен с целью сравнения эффективности и безопасности балоксавира и других противовирусных препаратов. Результаты. Время до облегчения всех симптомов при лечении балоксавиром значительно короче в сравнении с занамивиром (разница в медиане времени 19,96 ч; 95% байесовский доверительный интервал credibility interval, CrI [3,23; 39,07]). Время до прекращения выделения вируса у пациентов, принимавших балоксавир, значительно короче в сравнении с занамивиром и осельтамивиром (47,00 ч; 95% CrI [28,18; 73,86] и 56,03 ч [33,74; 87,86] соответственно). Среднее снижение вирусного титра от исходного уровня через 24 ч от начала лечения балоксавиром значительно более выражено в сравнении с другими препаратами. Различия по другим исходам эффективности незначительные. Значимых различий в безопасности балоксавира и других противовирусных препаратов не выявлено, за исключением риска развития нежелательных явлений, связанных с приемом препарата, который при лечении балоксавиром снижался в сравнении с осельтамивиром и ланинамивиром. Заключение. СМА подтвердил, что балоксавир по показателям эффективности не уступает или превосходит другие противовирусные препараты, при этом имеет сопоставимый с ними профиль безопасности. Лечение балоксавиром приводило к значительному снижению вирусного титра в сравнении с занамивиром, осельтамивиром и перамивиром и снижению выделения вируса в сравнении с занамивиром и осельтамивиром.

Background Baloxavir marboxil (baloxavir) is expected to reduce influenza transmission by rapid reduction of viral load. The incidence of household transmission was compared between index patients (IPs) treated with baloxavir and those treated with neuraminidase inhibitors. Methods Using a Japanese claims database, the first family members with influenza diagnosis during the 2018–2019 influenza season were identified as IPs, and the diagnosis date was designated day 1. According to the anti-influenza drug dispensed to the IP, their families were classified into the oral baloxavir group and 3 controls: oral oseltamivir group (a primary control), inhaled zanamivir group, and inhaled laninamivir group. A household transmission was defined as influenza diagnosed for any non-IP family members during days 3−8. The incidence of household transmission was compared between groups using a logistic regression model adjusting backgrounds of IPs. Results The proportion of families with household transmission was 17.98% (15 226 of 84 672) in the baloxavir group and 24.16% (14 983 of 62 004) in the oseltamivir group. The covariate-adjusted odds ratio (oseltamivir/baloxavir) was 1.09 (95% confidence interval [95% CI], 1.05–1.12), which indicated significantly lower incidence in the baloxavir group. The adjusted odds ratios (controls/baloxavir) against zanamivir and laninamivir were 0.93 (95% CI, .89–.97) and 0.99 (95% CI, .96–1.02), respectively. Conclusions Baloxavir may contribute to reduction in household transmission compared with oseltamivir. In comparison between baloxavir and inhalants, a similar reduction was not shown and it might be due to unmeasured confounding by administration route differences.

Yasuhiro Kamioka,1,2 Shota Kashiwagura,1,2 Masafumi Seki1 1Department of Infectious Diseases, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Sendai City, Miyagi, Japan; 2Division of Pharmacy, Tohoku Medical and Pharmaceutical University Hospital, Sendai City, Miyagi, JapanCorrespondence: Masafumi SekiDepartment of Infectious Diseases, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-Ku, Sendai City, Miyagi 983-8612, JapanTel +81-22-259-1221Fax +81-22-290-8956Email m-seki@tohoku-mpu.ac.jpObjective: 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.Keywords: anti-influenza agents, oseltamivir, laninamivir, zanamivir, peramivir, novel coronavirus-2019, COVID-19

To assess the extent of susceptibility to the four most commonly used neuraminidase inhibitors (NAIs) of the epidemic viruses in the 2018-19 Japanese influenza season, we measured the 50% inhibitory concentration (IC50) of four NAIs, oseltamivir, zanamivir, peramivir, and laninamivir, for influenza virus isolates from patients and compared them with the results from the 2010-11 to 2017-18 seasons. Viral isolation was done with specimens obtained prior to and after treatment, and the type/subtype was determined by RT-PCR using type- and subtype-specific primers. The IC50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. Virus isolates, 51 A(H1N1)pdm09, 125 A(H3N2), and one B, were measured in the 2018-19 season and the geometric mean IC50s of the four NAIs were quite comparable to the previous eight studied seasons. No A(H1N1)pdm09 with highly reduced sensitivity for oseltamivir was found in the 2018-19 season prior to drug administration, although such A(H1N1)pdm09 were found in two, two, and two samples in the 2010-11, 2013-14, and 2015-16 seasons, respectively. No isolates with highly reduced sensitivity to the four NAIs were found for A(H3N2) or B through the 2010-11 to 2018-19 seasons. Among 18 samples with A(H1N1)pdm09 virus isolated after NAI administration, highly reduced sensitivity to oseltamivir and peramivir was detected from one of the five patients treated with oseltamivir. These results suggest that the sensitivity to the four commonly used NAIs has been maintained, although viruses with highly reduced sensitivity to oseltamivir and peramivir have emerged in some adult patients treated with oseltamivir.

Highlights • Novel coronavirus (SARS-Coronavirus-2:SARS-CoV-2) which emerged in Wuhan, China, has spread to multiple countries rapidly. • This is the first case of meningitis associated with SARS-CoV-2 who was brought in by ambulance. • The specific SARS-CoV-2 RNA was not detected in the nasopharyngeal swab but was detected in a CSF. • This case warns the physicians of patients who have CNS symptoms., Novel coronavirus (SARS-Coronavirus-2:SARS-CoV-2) which emerged in Wuhan, China, has spread to multiple countries rapidly. We report the first case of meningitis associated with SARS-CoV-2 who was brought in by ambulance due to a convulsion accompanied by unconsciousness. He had never been to any foreign countries. He felt generalized fatigue and fever (day 1). He saw doctors nearby twice (day 2 and 5) and was prescribed Laninamivir and antipyretic agents, His family visited his home and found that he was unconsciousness and lying on the floor in his vomit. He was immediately transported to this hospital by ambulance (day 9). Under emergency transport, he had transient generalized seizures that lasted about a minute. He had obvious neck stiffness. The specific SARS-CoV-2 RNA was not detected in the nasopharyngeal swab but was detected in a CSF. Anti- HSV 1 and varicella-zoster IgM antibodies were not detected in serum samples. A brain MRI showed hyperintensity along the wall of right lateral ventricle and hyperintense signal changes in the right mesial temporal lobe and hippocampus, suggesting the possibility of SARS-CoV-2 meningitis. This case warns the physicians of patients who have CNS symptoms.

Our earlier study investigated the incidence of severe abnormal behavior associated with neuraminidase inhibitors (NIs), but some studies have specifically examined the association of oseltamivir use and moderately abnormal behavior. Therefore, this study was undertaken to assess associations between moderately abnormal behavior and administered drugs. All cases of patients with influenza who exhibited moderately abnormal behavior were reported to us by physicians of all sentinel clinics and hospitals for influenza throughout Japan. Open Data of the National Database of Electronic Medical Claims include the numbers of patients diagnosed as having influenza who were prescribed NI. Incidence by NI was tested using Fisher's exact test. We received 518 moderately abnormal cases in 5-9-year-olds and 207 moderately abnormal behavior cases in 10-19-year-olds. The incidence among NI ranged from 193 per one million influenza patients in laninamivir among 10-19-year-olds to 1021 for peramivir among 5-9-year-olds. Estimation results revealed the order of risk among NIs as peramivir, oseltamivir, zanamivir and laninamivir in moderate abnormal behavior. Because of data limitations, risk among patients with and without NI cannot be compared.

The recommended antiviral drugs available for the treatment and prevention of influenza are neuraminidase inhibitors (NAIs). The aim of this study was to evaluate age-related clinical manifestations of adverse events (AEs) related to NAIs. FAERS and WebMD data were downloaded. The available NAIs selected for the analysis were oseltamivir, peramivir, zanamivir, and laninamivir. Disproportionality was analyzed using the proportional reporting ratio (PRR), the reporting odds ratio (ROR), and the information component (IC) methods. In total, 16729 AEs from 4598 patients and 575 AEs from 440 patients in the FAERS and WebMD, respectively, were included in the analysis. In the FAERS, AEs were more common among those who were younger (65 years) for peramivir. A disproportionality analysis showed that signals for vomiting and hallucinations were detected in younger patients given oseltamivir, while an abnormal hepatic function, cardiac failure, shock, and cardio-respiratory arrest were detected in older patients given peramivir. Psychiatric disorders were most common in younger and older patients, while gastrointestinal disorders were most common in adult given oseltamivir in the WebMD. Adverse symptoms related to NAIs varied and depended on the drugs used and the age of the patient.

Background Here, we genetically and antigenically analyzed influenza B viruses (IBVs) isolated in Japan during the 2017‐2018 and 2018‐2019 influenza seasons. Methods A total of 68 IBVs (61 B/Yamagata/16/88‐like [B/Yamagata]‐lineage and 7 B/Victoria/2/87‐like [B/Victoria]‐lineage) were antigenically and genetically characterized by using hemagglutination inhibition (HI) assays and phylogenetic analysis, respectively. The susceptibility of IBVs to neuraminidase (NA) inhibitors was assessed by using a fluorescence‐based NA inhibition assay. Results All 61 B/Yamagata‐lineage isolates were genetically closely related to B/Phuket/3073/2013, the vaccine strain for these two seasons. Eleven B/Yamagata‐lineage isolates tested were antigenically similar to B/Phuket/3073/2013 by the HI test. Seven B/Victoria‐lineage isolates were genetically closely related to B/Texas/02/2013, the WHO‐recommended vaccine strain for the 2017‐2018 season; however, they were antigenically distinct from B/Texas/02/2013 with an eightfold or 16‐fold difference in HI titer. Of these 7 isolates, 4 possessed a two‐amino‐acid deletion at positions 162 and 163 in hemagglutinin (HA) and the other 3 had a three‐amino‐acid deletion at positions 162‐164 in HA. Importantly, the variants with the three‐amino‐acid deletion appeared to be antigenically different from the B/Colorado/06/2017 virus with the two‐amino‐acid deletion, the vaccine strain for the 2018‐2019 season with a fourfold or eightfold difference in HI titer. One B/Yamagata‐lineage isolate carrying a G407S mutation in its NA showed a marked reduction in susceptibility to zanamivir, peramivir, and laninamivir. Conclusions These results highlight the need for continued monitoring for the prevalence of the antigenic variant with the three‐amino‐acid deletion and the variant with reduced NA inhibitor susceptibility.

Background After the A/H1N1 influenza pandemic in 2009, two new drugs against influenza, namely laninamivir and peramivir, were released in 2010 in Japan. We investigated prescription trends of four neuraminidase inhibitors (NAIs), which are laninamivir, peramivir, oseltamivir, and zanamivir, and assessed clinical data related to influenza for 8 years. Methods Patients living in Osaka Prefecture and diagnosed with influenza responded to a postcard questionnaire that collected data regarding their demographic characteristics, symptoms including fever, prescribed drugs, and influenza type. Results Laninamivir was most prescribed to patients aged ≥ 10 years, and oseltamivir was most prescribed to patients aged, We showed the data of eight seasons and report prescription trends of four neuraminidase inhibitors (NAIs) and time course of fever in patients after taking these inhibitors. Doctors, especially general physicians, should consider how to choose anti‐influenza drugs. This study based on our 8‐year survey should be helpful to them when deciding which NAIs should be chosen in clinical settings and for which patients.

Laninamivir, a neuraminidase inhibitor (NAI), has been used for the treatment and prophylaxis of influenza A/B. To date, pneumonia has not been reported as an adverse effect of NAIs. Here, we report the first 2 cases of drug-induced pneumonitis after the administration of laninamivir octanoate (LO), a pro-drug of laninamivir. Case 1 reports a 20-year-old healthy woman presenting with LO-induced pneumonitis so severe that it was necessary for endotracheal intubation and administration of mechanical ventilator support. Steroids were used for the treatment of pneumonitis and rapid improvement was observed. Case 2 reports a 35-year-old healthy woman presenting with less severe LO-induced pneumonitis that improved without any treatment. In both cases, drug-induced lymphocyte stimulation tests (DLSTs) were positive. In the bronchoalveolar lavage (BAL) fluid, the proportion of eosinophils to lymphocytes was higher in Case 1. Conversely, the proportion of lymphocytes to eosinophils was higher in Case 2. Collectively, we determined 3 clinical issues: (1) LO could cause pneumonia; (2) BAL and DLST could be helpful in the diagnosis of LO-induced pneumonitis; and (3) LO-induced pneumonia could become severe, though steroids were effective in improving it.

OBJECTIVES To investigate the susceptibility of epidemic influenza viruses to neuraminidase inhibitors (NAIs) and the emergence of resistant viruses after treatment, a prospective, observational study was done in the 2019-20 Japanese influenza season. METHODS Influenza viruses were isolated before and twice after treatment, the first at day 5 and the second at day 10. The 50% inhibitory concentrations (IC50s) to oseltamivir, zanamivir, peramivir, and laninamivir were measured and compared with those of 2010-11 to 2018-19 seasons. NA amino acid sequences were analyzed by next generation sequencing (NGS). RESULTS The IC50 geometric means of the NAIs for 128 A(H1N1)pdm09, 2 A(H3N2), and 33 B were comparable to those of the previous seasons. Only 2 (1.6%) A(H1N1)pdm09 with significantly high IC50 to oseltamivir were found pretreatment. No A(H3N2) or B had resistance. Treatment-emergent oseltamivir resistance was found in 2 among 33 oseltamivir-treated A(H1N1)pdm09, only at the second follow-up. The NGS indicated a rapid increase in the proportion of H275Y to wild type, from 0% to almost 100༅ between days 5 and 10. CONCLUSIONS These results suggest the continued effectiveness of these NAIs for epidemic influenza in Japan. Treatment-emergent resistant H275Y A(H1N1)pdm09 viruses were detected after oseltamivir treatment, rapidly replacing the wild type.

Four neuraminidase (NA) inhibitors and an RNA synthesis inhibitor were recently approved and are currently in clinical use for influenza. Among NA inhibitors, oseltamivir phosphate (OSE, Tamiflu®) and zanamivir are approved worldwide, whereas peramivir and laninamivir octanoate (LAN, Inavir®) are regionally approved for human use. Therefore, OSE has been used to treat infections of highly pathogenic influenza viruses, such as H5N1 and H7N9, which caused epidemic in southeast Asia and Egypt, and China, respectively. Generally, OSE is administered twice daily for 5 days by oral administration, and LAN once by inhalation for completing influenza therapy. In this study, we compared the efficacy of OSE and LAN administered according to the regimens in mice infected with highly lethal influenza viruses. The drugs were administered at the early and late stages of infection, which correspond to mild and severe inflammation in the lungs, respectively. Based on the drugs' regimens for human, a single administration of LAN at both stages of inflammation showed superior efficacy to repeated administration of OSE. LAN, as in OSE, could also be efficacious in treating severe influenza in humans.

Background The large consumption of neuraminidase inhibitors (NAIs) for the treatment of influenza virus infections places Japan at risk of becoming the epicenter of the global spread of NAI-resistant viruses. Objective To clarify NA amino acid mutations of epidemic influenza viruses in Japan and their related NAI resistance. Methods A total of 1791 samples, including 396 A/H1N1pdm09, 1117 A/H3N2, and 278 B isolates, were collected to determine of their 50% inhibitory concentration (IC50 ) values by NAIs (oseltamivir, zanamivir, peramivir, and laninamivir) during the Japanese seasons from 2011-2012 to 2016-2017. Then, 380 samples including 49 A/H1N1pdm09, 251 A/H3N2, and 80 B isolates were sequenced for the entire NA genes. Results Neuraminidase inhibitor-resistant A/H1N1pdm09 viruses were detected at a frequency of 1.3% (5/396 isolates) in the epidemic seasons. None of the A/H3N2 and B viruses developed resistance to any of the four NAIs during the six seasons. Only five and 13 AA mutations were detected in the NA catalytic sites of A/H1N1pdm09 and A/H3N2 viruses, respectively. No mutations were observed in the catalytic sites of B viruses. Four of the five mutations in the catalytic sites of A/H1N1pdm09 consisted of H275Y, which was related to high resistance to oseltamivir and peramivir. Most (10/13) of the catalytic site mutations in A/H3N2 were associated with MDCK-passaged induction (D151G/N). Finally, no mutations related to substantial NAI resistance were detected in the A/H3N2 and B viruses examined. Conclusion These findings suggest that the NA catalytic sites of influenza viruses are well preserved. Even in Japan, no spread of NAI-resistant viruses has been observed, and A/H1N1pdm09 viruses carrying H275Y remain limited.

Introduction We conducted a post-marketing surveillance of laninamivir octanoate hydrate for Inhalation Suspension Set in patients under the age of 5 infected with the influenza virus to evaluate safety and efficacy of the drug. Methods Subjects enrolled by the centralized enrollment system were administered laninamivir once using a nebulizer based on the package insert. Results Safety was evaluated in 1104 patients. The incidence of ADRs was 1.00% (11/1104). Compared to the incidence of ADRs of 2.04% (9/441) in the clinical trials for development, no increase in the frequency of ADRs was noted. Serious ADRs were noted in 3 patients (5 cases): 2 cases of convulsive attack, each 1 case of muscular weakness, a depressed level of consciousness, and pain in extremities. Excluding 2 patients with unknown outcomes, all of the patients recovered or their symptoms were alleviated. To detect risk factors for the occurrence of ADRs, 16 attributes were examined, and none of them were found to be significant. Efficacy was evaluated in 881 patients. The median time (95% CI) to fever resolution was 37.0 (33.0–39.0) h in type A virus (785 patients), 45.0 (34.0–56.0) h in type B virus (95 patients), and 22.0 h (1 patient) in the mixed type. This was similar to the time to fever resolution in the clinical trials. Conclusion The results of this surveillance verified that there are no noticeable problems with the safety or efficacy of laninamivir for children under the age of 5 infected with the influenza A and B viruses.

Laninamivir (LAN) is a long-acting neuraminidase (NA) inhibitor (NAI) with a similar binding profile in the influenza NA enzyme active site as those of other NAIs, oseltamivir (OS), zanamivir (ZAN), and peramivir, and may share common resistance markers with these NAIs. We screened viruses with NA substitutions previously found during OS and ZAN selection in avian influenza viruses (AIVs) of the N3 to N9 subtypes for LAN susceptibility. Of the 72 NA substitutions, 19 conferred resistance to LAN, which ranged from 11.2- to 549.8-fold-decreased inhibitory activity over that of their parental viruses. Ten NA substitutions reduced the susceptibility to all four NAIs, whereas the remaining 26 substitutions yielded susceptibility to one or more NAIs. To determine whether the in vitro susceptibility of multi-NAI-resistant AIVs is associated with in vivo susceptibility, we infected BALB/c mice with recombinant AIVs with R292K (ma81K-N3R292K) or Q136K (ma81K-N8Q136K) NA substitutions, which impart in vitro susceptibility only to LAN or OS, respectively. Both ma81K-N3R292K and ma81K-N8Q136K virus-infected mice exhibited reduced weight loss, mortality, and lung viral titers when treated with their susceptible NAIs, confirming the in vitro susceptibility of these substitutions. Together, LAN resistance profiling of AIVs of a range of NA subtypes improves the understanding of NAI resistance mechanisms. Furthermore, the association of in vitro and in vivo NAI susceptibility indicates that our models are useful tools for monitoring NAI susceptibility of AIVs. IMPORTANCE The chemical structures of neuraminidase inhibitors (NAIs) possess similarities, but slight differences can result in variable susceptibility of avian influenza viruses (AIVs) carrying resistance-associated NA substitutions. Therefore, comprehensive susceptibility profiling of these substitutions in AIVs is critical for understanding the mechanism of antiviral resistance. In this study, we profiled resistance to the anti-influenza drug laninamivir in AIVs with substitutions known to impart resistance to other NAIs. We found 10 substitutions that conferred resistance to all four NAIs tested. On the other hand, we found that the remaining 26 NA substitutions were susceptible to at least one or more NAIs and showed for a small selection that in vitro data predicted in vivo behavior. Therefore, our findings highlight the usefulness of screening resistance markers in NA enzyme inhibition assays and animal models of AIV infections.

A neuraminidase inhibitor, laninamivir octanoate (Inavir®; Daiichi Sankyo, Tokyo, Japan) is an inhaled drug with unique characteristics. The inhaled laninamivir octanoate is converted into its active form, laninamivir, in the lungs where a high concentration continues for a long period of time. The concentration of laninamivir exceeds the level necessary for virus replication inhibition for at least 5 days, thus treatment for influenza can be completed with only a single administration through inhalation.

Neuraminidase inhibitors (NAIs), that currently include oseltamivir (Tamiflu® ), zanamivir (Relenza® ), peramivir (Rapivab® ) and laninamivir (Inavir® ), constitute an important class of antivirals recommended against seasonal influenza A and B infections. NAIs target the surface NA protein whose sialidase activity is responsible for virion release from infected cells. Because of their pivotal role in the transcription/translation process, the polymerase acidic (PA) and polymerase basic 1 and 2 (PB1 and PB2, respectively) internal proteins also constitute targets of interest for the development of additional anti-influenza agents. Baloxavir marboxil (BXM), an inhibitor of the cap-dependent endonuclease activity of the influenza PA protein, was approved in the United States and Japan in 2018. Baloxavir acid (BXA), the active compound of BXM, demonstrated a potent in vitro activity against different types/subtypes of influenza viruses including seasonal influenza A/B strains as well as avian influenza A viruses with a pandemic potential. A single oral dose of BXM provided virological and clinical benefits that were respectively superior or equal to those displayed by the standard (5 days, twice daily) oseltamivir regimen. Nevertheless, BXM-resistant variants have emerged at relatively high rates in BXM-treated children and adults. Consequently, there is a need to study the fitness (virulence and transmissibility) characteristics of mutants with a high potential to emerge as such variants can compromise the clinical usefulness of BXM. The purpose of this manuscript is to review the fitness properties of influenza A and B isolates harbouring mutations of reduced susceptibility to BXA.

Yasuhiro Kamioka,1,2 Shota Kashiwagura,1,2 Masafumi Seki1 1Department of Infectious Diseases, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Sendai City, Miyagi, Japan; 2Division of Pharmacy, Tohoku Medical and Pharmaceutical University Hospital, Sendai City, Miyagi, JapanCorrespondence: Masafumi SekiDepartment of Infectious Diseases, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-Ku, Sendai City, Miyagi 983-8612, JapanTel +81-22-259-1221Fax +81-22-290-8956Email m-seki@tohoku-mpu.ac.jpObjective: 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.Keywords: anti-influenza agents, oseltamivir, laninamivir, zanamivir, peramivir, novel coronavirus-2019, COVID-19

Background: Several studies reported that abnormal behavior was noted in pediatric patients receiving several drugs, including neuraminidase inhibitors (NIs). However, the information on drugs associated with abnormal behavior in a real-world setting remains limited. The purpose of this study was to clarify the drugs associated with abnormal behavior using a spontaneous reporting system database. Methods: We performed a retrospective pharmacovigilance disproportionality analysis using the Japanese Adverse Drug Event Report database. Adverse event reports submitted to the Pharmaceuticals and Medical Devices Agency were analyzed, and the reporting odds ratio at 95% confidence interval were calculated. Results: A total of 1,144 reports of abnormal behavior were identified. The signals were detected through the association of 4 neuraminidase inhibitors (oseltamivir, zanamivir, laninamivir, and peramivir) with the abnormal behaviour. These signals were stronger for oseltamivir than other neuraminidase inhibitors. The signals were also detected for acetaminophen and montelukast. Conclusion: Our results should be able to raise physicians’ awareness of drugs associated with abnormal behavior, but further investigation of these medications is warranted.

Each year, 5% to 20% of the population of the United States becomes infected with influenza A virus. Combination therapy with two or more antiviral agents has been considered a potential treatment option for influenza virus infection. However, the clinical results derived from combination treatment with two or more antiviral drugs have been variable. We examined the effectiveness of cotreatment with two distinct classes of anti-influenza drugs, i.e., neuraminidase (NA) inhibitor, laninamivir, and interferon lambda 1 (IFN-λ1), against the emergence of drug-resistant virus variants in vitro. We serially passaged pandemic A/California/04/09 [A(H1N1)pdm09] influenza virus in a human lung epithelial cell line (Calu-3) in the presence or absence of increasing concentrations of laninamivir or laninamivir plus IFN-λ1. Surprisingly, laninamivir used in combination with IFN-λ1 promoted the emergence of the E119G NA mutation five passages earlier than laninamivir alone (passage 2 versus passage 7, respectively). Acquisition of this mutation resulted in significantly reduced sensitivity to the NA inhibitors laninamivir (∼284-fold) and zanamivir (∼1,024-fold) and decreased NA enzyme catalytic activity (∼5-fold) compared to the parental virus. Moreover, the E119G NA mutation emerged together with concomitant hemagglutinin (HA) mutations (T197A and D222G), which were selected more rapidly by combination treatment with laninamivir plus IFN-λ1 (passages 2 and 3, respectively) than by laninamivir alone (passage 10). Our results show that treatment with laninamivir alone or in combination with IFN-λ1 can lead to the emergence of drug-resistant influenza virus variants. The addition of IFN-λ1 in combination with laninamivir may promote acquisition of drug resistance more rapidly than treatment with laninamivir alone.

Influenza virus is an enveloped virus having segmented genome, coded by eight (negative-sense) RNA segments. The RNA segments are packed in a nucleocapsid protein. Neuraminidase (NA), an exosialidase, is the major antigen as well as vital virulence factor of the virus and is coded by the 6th segment of RNA. Eleven subtypes of NA are characterized for influenza A and the N1–N9 are divided into two phylogenic groups. NA is an active target for development of potent antivirals or Neuraminidase inhibitors (NAIs), which are reported to interact with multiple conserved residues in the active site of NA resulting in inhibition of virion release and prevention of viral spread to nearby cells. The current computational study focuses on docking of eleven different drug-like molecules including the known NAIs such as oseltamivir and zanamivir against crystal structures of NA of human Influenza A virus subtypes of both phylogenic groups. The docking results of this study indicated that zanamivir was the most active drug candidate against various NA subtypes followed by laninamivir. The study provides insights on interactions as well as cross-reactivity between lead compounds and NA proteins of various influenza subtypes. Observations on the efficacy of these NAIs assessed by the computational study have to be validated through in vitro and in vivo studies for successfully translating them as potential therapeutic agents to treat infection by various subtypes of influenza. Keywords: Influenza A virus, Computational analysis, Docking, Neuraminidase, Antivirals, Drugs

The duration of fever and symptoms after laninamivir octanoate hydrate (laninamivir) inhalation were investigated in the Japanese 2016/17 influenza season and the results were compared with those of the 2011/12 to 2015/16 seasons. A total of 1278 patients were evaluated for the duration of fever and symptoms in the six studied seasons. In the 2016/17 season, the influenza types/subtypes of the patients were 6 A (H1N1)pdm09 (2.9%), 183 A (H3N2) (87.6%), and 20 B (9.6%). The respective median durations of fever for A (H1N1)pdm09, A (H3N2), and B were 38.0, 33.0, and 38.5 h, without significant difference (p = 0.9201), and the median durations of symptoms were 86.5, 73.0, and 99.0 h, with significant difference (p = 0.0342). The median durations of fever and symptoms after laninamivir inhalation were quite consistent for the six studied seasons for A (H1N1)pdm09, A (H3N2), and B, without any significant differences. The percentage of patients with unresolved fever patients displayed a similar pattern through the six studied seasons for all these virus types. There was no significant difference in the duration of fever or symptoms between the Victoria and Yamagata lineages in the 2016/17 season and those of the previous studied seasons. Over the seasons tested, ten adverse drug reactions (ADRs) were reported from 1341 patients. The most frequent ADR was diarrhea and all ADRs were self-resolving and not serious. These results indicate the continuing clinical effectiveness of laninamivir against influenza A (H1N1)pdm09, A (H3N2), and B, with no safety issues.

The anti-influenza virus drug oseltamivir has been reported to have several pharmacological actions including blocking of nicotinic acetylcholine receptor channels and activation of the dopaminergic system. These pharmacological actions highly overlap those of amantadine, another anti-influenza virus drug authorized in Japan, and ester-type local anesthetics. Moreover, oseltamivir and amantadine can clinically induce similar adverse neuropsychiatric reactions. In the present study, from the database of the Pharmaceuticals and Medical Devices Agency (PMDA), we surveyed 2576 drugs for which neuropsychiatric side effects similar to those of oseltamivir, amantadine and local anesthetics (abnormal behavior, confusion, consciousness disturbance, convulsion, delirium, delusion, hallucination, myoclonus, tremor) are listed as "clinically significant adverse reactions", and found 327 that had at least one of these adverse reactions. Other neuraminidase inhibitors (laninamivir, peramivir and zanamivir) did not elicit such adverse reactions. By discussing the pharmacological effects of drugs that elicit these adverse reactions, we propose that the similarity of adverse neuropsychiatric reactions between oseltamivir and amantadine is possibly attributable to their common pharmacological effects.

The global analysis of neuraminidase inhibitor (NAI) susceptibility of influenza viruses has been conducted since the 2012-13 period. In 2018 a novel cap-dependent endonuclease inhibitor, baloxavir, that targets polymerase acidic subunit (PA) was approved for the treatment of influenza virus infection in Japan and the United States. For this annual report, the susceptibilities of influenza viruses to NAIs and baloxavir were analyzed. A total of 15409 viruses, collected by World Health Organization (WHO) recognized National Influenza Centers and other laboratories between May 2017 and May 2018, were assessed for phenotypic NAI susceptibility by five WHO Collaborating Centers (CCs). The 50% inhibitory concentration (IC50) was determined for oseltamivir, zanamivir, peramivir and laninamivir. Reduced inhibition (RI) or highly reduced inhibition (HRI) by one or more NAIs was exhibited by 0.8% of viruses tested (n = 122). The frequency of viruses with RI or HRI has remained low since this global analysis began (2012-13: 0.6%; 2013-14: 1.9%; 2014-15: 0.5%; 2015-16: 0.8%; 2016-17: 0.2%). PA gene sequence data, available from public databases (n = 13523), were screened for amino acid substitutions associated with reduced susceptibility to baloxavir (PA E23 G/K/R, PA A36V, PA A37T, PA I38 F/M/T/L, PA E119D, PA E199G): 11 (0.08%) viruses possessed such substitutions. Five of them were included in phenotypic baloxavir susceptibility analysis by two WHO CCs and IC50 values were determined. The PA variant viruses showed 6-17-fold reduced susceptibility to baloxavir. Overall, in the 2017-18 period the frequency of circulating influenza viruses with reduced susceptibility to NAIs or baloxavir was low, but continued monitoring is important.

The clinical effectiveness of four neuraminidase inhibitors (NAIs) (oseltamivir, zanamivir, laninamivir, and peramivir) for children aged 0 months to 18 years with influenza A and B were investigated in the 2014-2015 to 2016-2017 influenza seasons in Japan. A total of 1207 patients (747 with influenza A and 460 with influenza B) were enrolled. The Cox proportional-hazards model using all of the patients showed that the duration of fever after administration of the first dose of the NAI was shorter in older patients (hazard ratio = 1.06 per 1 year of age, p < 0.001) and that the duration of fever after administration of the first dose of the NAI was shorter in patients with influenza A infection than in patients with influenza B infection (hazard ratio = 2.21, p < 0.001). A logistic regression model showed that the number of biphasic fever episodes was 2.99-times greater for influenza B-infected patients than for influenza A-infected patients (p < 0.001). The number of biphasic fever episodes in influenza A-or B-infected patients aged 0-4 years was 2.89-times greater than that in patients aged 10-18 years (p = 0.010), and the number of episodes in influenza A-or B-infected patients aged 5-9 years was 2.13times greater than that in patients aged 10-18 years (p = 0.012).

Neuraminidase (NA) mutations conferring resistance to NA inhibitors (NAIs) are expected to occur at framework or catalytic residues of the NA enzyme. Numerous clinical and in vitro reports already described NAI-resistant A(H1N1)pdm09 variants harboring various framework NA substitutions. By contrast, variants with NA catalytic changes remain poorly documented. Herein, we investigated the effect of R152K and R368K NA catalytic mutations on the NA enzyme properties, in vitro replicative capacity and virulence of A(H1N1)pdm09 recombinant viruses. In NA inhibition assays, the R152K and R368K substitutions resulted in reduced inhibition [10- to 100-fold increases in IC50 vs the wild-type (WT)] or highly reduced inhibition (>100-fold increases in IC50) to at least 3 approved NAIs (oseltamivir, zanamivir, peramivir and laninamivir). Such resistance phenotype correlated with a significant reduction of affinity observed for the mutants in enzyme kinetics experiments [increased Km from 20 ± 1.77 for the WT to 200.8 ± 10.54 and 565.2 ± 135 μM (P

A total of 13672 viruses, collected by World Health Organization recognised National Influenza Centres between May 2016 and May 2017, were assessed for neuraminidase inhibitor susceptibility by four WHO Collaborating Centres for Reference and Research on Influenza and one WHO Collaborating Centre for the Surveillance Epidemiology and Control of Influenza. The 50% inhibitory concentration (IC50) was determined for oseltamivir and zanamivir for all viruses, and for peramivir and laninamivir in a subset (n = 8457). Of the viruses tested, 94% were obtained from the Western Pacific, Americas and European WHO regions, while limited viruses were available from the Eastern Mediterranean, African and South East Asian regions. Reduced inhibition (RI) by one or more neuraminidase inhibitor was exhibited by 0.2% of viruses tested (n = 32). The frequency of viruses with RI has remained low since this global analysis began (2015/16: 0.8%, 2014/15: 0.5%; 2013/14: 1.9%; 2012/13: 0.6%) but 2016/17 has the lowest frequency observed to date. Analysis of 13581 neuraminidase sequences retrieved from public databases, of which 5243 sequences were from viruses not included in the phenotypic analyses, identified 58 further viruses (29 without phenotypic analyses) with amino acid substitutions associated with RI by at least one neuraminidase inhibitor. Bringing the total proportion to 0.5% (90/18915). This 2016/17 analysis demonstrates that neuraminidase inhibitors remain suitable for treatment and prophylaxis of influenza virus infections, but continued monitoring is important. An expansion of surveillance testing is paramount since several novel influenza antivirals are in late stage clinical trials with some resistance already having been identified., Highlights • A total of 13,672 influenza viruses were collected worldwide, May 2016–May 2017. • Approximately 0.2% showed reduced inhibition by at least one NA inhibitor. • The frequency of viruses with reduced inhibition by NA inhibitors was at the lowest since analysis began in 2012. • Newly licenced antivirals and drugs currently in clinical trials are summarized. • Global surveillance of influenza antiviral susceptibility should be continued.

BACKGROUND. Neuraminidase (NA) inhibitors are the recommended antiviral medications for influenza treatment. However, their therapeutic efficacy can be compromised by NA changes that emerge naturally and/or following antiviral treatment. Knowledge of which molecular changes confer drug resistance of influenza A(H7N9) viruses (group 2NA) remains sparse. METHODS. Fourteen amino acid substitutions were introduced into the NA of A/Shanghai/2/2013(H7N9). Recombinant N9 (recN9) proteins were expressed in a baculovirus system in insect cells and tested using the Centers for Disease Control and Prevention standardized NA inhibition (NI) assay with oseltamivir, zanamivir, peramivir, and laninamivir. The wild-type N9 crystal structure was determined in complex with oseltamivir, zanamivir, or sialic acid, and structural analysis was performed. RESULTS. All substitutions conferred either reduced or highly reduced inhibition by at least 1 NA inhibitor; half of them caused reduced inhibition or highly reduced inhibition by all NA inhibitors. R292K conferred the highest increase in oseltamivir half-maximal inhibitory concentration (IC(50)), and E119D conferred the highest zanamivir IC(50). Unlike N2 (another group 2NA), H274Y conferred highly reduced inhibition by oseltamivir. Additionally, R152K, a naturally occurring variation at the NA catalytic residue of A(H7N9) viruses, conferred reduced inhibition by laninamivir. CONCLUSIONS. The recNA method is a valuable tool for assessing the effect of NA changes on drug susceptibility of emerging influenza viruses.

This paper provides an overview of the currently available treatment options for influenza infections. Currently, the options are limited to only one class of drugs known as the neuraminidase inhibitors (NAIs) (oseltamivir, zanamivir, laninamivir and peramivir) as there is widespread resistance against the adamantanes, an older class of antivirals. This review therefore discusses the mode of action, dosing, summary of clinical trial data and resistance within the context of NAIs. Newer antiviral therapies in late-phase clinical trials are also summarized in this review. Oseltamivir is the most commonly used NAI amongst the four different types available. The most recent meta-analysis of placebo-controlled trials demonstrates that for uncomplicated seasonal influenza, oseltamivir reduces symptoms by 16–24 h, while observational studies cumulatively suggest that oseltamivir treatment reduces mortality in severely ill patients. NAIs also play an important role in the treatment and control of avian influenza infections in humans, which is a public health concern due to their high case fatality rate. The latest analysis of data suggests that early treatment with oseltamivir can be attributed to reducing mortality in patients with avian A(H5N1) infections; data regarding oseltamivir effectiveness against A(H7N9) infections is however more limited. During the 2014–2015 influenza season, the frequency of resistance to the NAIs in all circulating viruses was below 1%, but immunocompromised patients infected with influenza are often at higher risk of shedding resistant viruses due to slow viral clearance and extended treatment regimens. Favipiravir, a polymerase inhibitor, has received limited approval for use in Japan, but its use is restricted to novel viruses that are resistant to other antiviral therapies. Antivirals such as thiazolide, nitazoxanide and endonuclease inhibitor, S-033188, are currently in phase III clinical trials and other influenza antivirals are in early or mid-phase clinical trials. This review highlights a lack of different treatment options for influenza infections. While there are four different types of NAIs, in many countries, oseltamivir is the only available option. New therapies are being rapidly developed to meet the need for a greater variety of antivirals, and as such, it is likely that over the next decade, a broader range of influenza therapeutics will become available for treatment.

We evaluated the environmental fate of new three anti-influenza drugs, favipiravir (FAV), peramivir (PER), and laninamivir (LAN), and an active prodrug of LAN, laninamivir octanoate (LANO), in comparison with four conventional drugs, oseltamivir (OS), oseltamivir carboxylate (OC), amantadine (AMN), and zanamivir (ZAN) by photodegradation, biodegradation, and sorption to river sediments. In addition, we conducted 9-month survey of urban rivers in the Yodo River basin from 2015 to 2016 (including the influenza season) to investigate the current status of occurrence of these drugs in the river environment. The results clearly showed that FAV and LAN rapidly disappeared through photodegradation (half-lives 1 and 8 h, respectively), followed by LANO which gradually disappeared through biodegradation (half-life, 2 days). The remained PER and conventional drugs were, however, persistent and transported from upstream to downstream sites. Rates of their sorption to river sediments were negligibly small. Detected levels remained were in the range from N.D. to 89 ng/L for the river waters and from N.D. to 906 ng/L in sewage effluent. However, all of the remained drugs were effectively removed by ozonation after chlorination at a sewage treatment plant. These findings suggest the importance of introducing ozonation for reduction of pollution loads in rivers, helping to keep river environments safe. To the best of our knowledge, this is the first evaluation of the removal effects of natural sunlight, biodegradation, and sorption to river sediments on FAV, PER, LAN, LANO, and a conventional drug, AMN.

Emergence of pan neuraminidase inhibitor (NAI)-resistant variants constitutes a serious clinical concern. An influenza A(H1N1)pdm09 variant containing the I427T/Q313R neuraminidase (NA) substitutions was previously identified in a surveillance study. Although these changes are not part of the NA active site, the variant showed reduced susceptibility to many NAIs. In this study, we investigated the mechanism of resistance for the I427T/Q313R substitution and its impact on the NA enzyme and viral fitness. Recombinant wild-type (WT), I427T/Q313R and I427T A(H1N1)pdm09 viruses were generated by reverse genetics and tested for their drug susceptibilities, enzymatic properties and replication kinetics in vitro as well as their virulence in mice. Molecular dynamics (MD) simulations were performed for NA structural analysis. The I427T substitution, which was responsible for the resistance phenotype observed in the double (I427T/Q313R) mutant, induced 17-, 56-, 7-, and 14-fold increases in IC50 values against oseltamivir, zanamivir, peramivir and laninamivir, respectively. The I427T substitution alone or combined to Q313R significantly reduced NA affinity. The I427T/Q313R and to a lesser extent I427T recombinant viruses displayed reduced viral titers vs WT in vitro. In experimentally-infected mice, the mortality rates were 62.5%, 0% and 14.3% for the WT, I417T/Q313R and I427T viruses, respectively. There were about 2.5- and 2-Log reductions in mean lung viral titers on day 5 post-infection for the I427T/Q313R and I427T mutants, respectively, compared to WT. Results from simulations revealed that the I427T change indirectly altered the stability of the catalytic R368 residue of the NA enzyme causing its reduced binding to the substrate/inhibitor. This study demonstrates that the I427T/Q313R mutant, not only alters NAI susceptibility but also compromises NA properties and viral fitness, which could explain its infrequent detection in clinic.

There are three classes of antiviral drugs approved for the treatment of influenza: the M2 ion channel inhibitors (amantadine, rimantadine), neuraminidase (NA) inhibitors (laninamivir, oseltamivir, peramivir, zanamivir), and the protease inhibitor (favipiravir); some of the agents are only available in selected countries [1, 2]. These agents are effective at treating the signs and symptoms of influenza in patients infected with susceptible viruses. Clinical failure has been demonstrated in patients infected with viruses with primary resistance, i.e., antivirals can be present in the virus initially infecting the patient, or resistance may emerge during the course of therapy [3–5]. NA inhibitors are active against all nine NA subtypes recognized in nature [6], including highly pathogenic avian influenza A/H5N1 and recent low-pathogenic avian influenza A/H7N9 viruses [7]. Since seasonal influenza is usually an acute, self-limited illness in which viral clearance usually occurs rapidly due to innate and adaptive host immune responses, the emergence of drug-resistant variants would be anticipated to have limited effect on clinical recovery in otherwise healthy patients, as has been demonstrated clinically [3, 8, 9]. Unfortunately, immunocompromised or immunologically naïve hosts, such as young children and infants or those exposed to novel strains, are more likely to have mutations that confer resistance emergence during therapy; such resistant variants may also result in clinically significant adverse outcomes [10–13].

We herein report the first case of immune-mediated drug-induced liver injury that may have been caused by laninamivir. A 15-year-old girl was diagnosed with influenza and prescribed 40 mg laninamivir. Six weeks later, she was admitted to our hospital because of jaundice and fatigue. Laboratory examinations revealed elevated levels of hepatobiliary enzymes, and acute liver injury was suspected. Laboratory examinations and histological findings were characteristic of autoimmune hepatitis. Steroid treatment was ineffective, and azathioprine was added to the treatment. Twenty-two months after the onset, a second biopsy revealed the absence of inflammatory infiltrations, and the drugs were withdrawn. Liver function tests remained normal nine months after withdrawal.

Introduction: Hemorrhagic shock and encephalopathy syndrome (HSES) is a type of acute encephalopathy mainly seen in infants. It is a syndrome encompassing an onset of high fever, disturbance of consciousness, convulsion, and shock that rapidly progresses to watery diarrhea and liver and renal dysfunctions. It is extremely rare in adults, and the number of reports is limited worldwide. We report the case of an adult patient with HSES, which occurred after influenza A infection. Patient concerns: A 52-year-old man visited his family doctor 2 days after he noticed fever and was diagnosed with influenza A using an influenza rapid diagnosis kit; he underwent treatment on an outpatient basis. He was immediately hospitalized after developing fever, abdominal pain, malaise, and shock 16 hours after the commencement of the treatment. Abrupt acute brain swelling was noted 24 hours after hospitalization. Diagnoses: The antibody titer to influenza A (H3N2) was 1:40. Computed tomography obtained 24 hours after treatment initiation confirmed acute cerebral edema and cerebral herniation. Electroencephalogram at that time showed a flat line. Interventions: For the treatment of influenza A, laninamivir 150 mg was started immediately after the diagnosis by the family doctor, and 600 mg dose was given daily after hospitalization (or since 24 hours after the treatment initiation). For the management of shock, dobutamine 3 μg/kg/min and noradrenaline up to 0.2 μg/kg/min were used together with bolus infusion. Outcomes: The patient was declared brain dead on his 6th hospital day and he died on his 27th hospital day. Conclusion: Drastic courses such as that in our case with HSES can follow influenza infections even in adults.

Neuraminidase (NA) inhibitors (NAIs) are widely used antiviral drugs for the treatment of humans with influenza virus infections. There have been widespread reports of NAI resistance among seasonal A(H1N1) viruses, and most have been identified in oseltamivir-exposed patients or those treated with other NAIs. Thus, monitoring and identifying NA markers conferring resistance to NAIs—particularly newly introduced treatments—are critical to the management of viral infections. Therefore, we screened and identified substitutions conferring resistance to laninamivir by enriching random mutations in the NA gene of the 2009 pandemic influenza [A(H1N1)pdm09] virus followed by deep sequencing of the laninamivir-selected variants. After the generation of single mutants possessing each identified mutation, two A(H1N1)pdm09 recombinants possessing novel NA gene substitutions (i.e., D199E and P458T) were shown to exhibit resistance to more than one NAI. Of note, mutants possessing P458T—which is located outside of the catalytic or framework residue of the NA active site—exhibited highly reduced inhibition by all four approved NAIs. Using MDCK cells, we observed that the in vitro viral replication of the two recombinants was lower than that of the wild type (WT). Additionally, in infected mice, decreased mortality and/or mean lung viral titers were observed in mutants compared with the WT. Reverse mutations to the WT were observed in lung homogenate samples from D199E-infected mice after 3 serial passages. Overall, the novel NA substitutions identified could possibly emerge in influenza A(H1N1)pdm09 viruses during laninamivir therapy and the viruses could have altered NAI susceptibility, but the compromised in vitro/in vivo viral fitness may limit viral spreading. IMPORTANCE With the widespread emergence of NAI-resistant influenza virus strains, continuous monitoring of mutations that confer antiviral resistance is needed. Laninamivir is the most recently approved NAI in several countries; few data exist related to the in vitro selection of viral mutations conferring resistance to laninamivir. Thus, we screened and identified substitutions conferring resistance to laninamivir by random mutagenesis of the NA gene of the 2009 pandemic influenza [A(H1N1)pdm09] virus strain followed by deep sequencing of the laninamivir-selected variants. We found several novel substitutions in NA (D199E and P458T) in an A(H1N1)pdm09 background which conferred resistance to NAIs and which had an impact on viral fitness. Our study highlights the importance of continued surveillance for potential antiviral-resistant variants and the development of alternative therapeutics.

The Fukushima research has examined data form a cohort study of 10,000 Japanese children under 18 years old with influenza during three months to demonstrate that the relative risk of A-type abnormal behavior of patients with oseltamivir was 30 times greater than without oseltamivir. By contrast, our research group found that patients who had been administered no neuraminidase inhibitors (NI) or those administered peramivir had higher risk of abnormal behavior than those administered oseltamivir, zanamivir, or laninamivir. A plausible explanation for this gap is that the two studies specifically examined different criteria to report abnormal behavior. In actually, some A-type abnormal behavior might not be life-threatening. Our definition of severe abnormal behavior is better matched to public health concerns and comparison among incidents according to the administered drug is more appropriate as an analytical procedure.

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.

Avian A(H7N9) infections in humans have been reported in China since 2013 and are of public health concern due to their severity and pandemic potential. Oseltamivir and peramivir are neuraminidase inhibitors (NAIs) routinely used for the treatment of A(H7N9) infections, but variants with reduced sensitivity to these drugs can emerge in patients during treatment. Zanamivir and laninamivir are NAIs that are used less frequently. Herein, we performed in vitro serial passaging experiments with recombinant viruses, containing the neuraminidase (NA) from influenza A/Anhui/1/13 (H7N9) virus, in the presence of each NAI, to determine whether variants with reduced sensitivity would emerge. NA substitutions were characterized for their effect on the NA enzymatic activity and surface expression of the A/Anhui/1/13 (Anhui/1) NA, as well as NAs originating from contemporary A(H7N9) viruses of the Yangtze River Delta and Pearl River Delta lineages. In vitro passage in the presence of oseltamivir, peramivir and laninamivir selected for substitutions associated with reduced sensitivity (E119D, R292K and R152K), whereas passage in the presence of zanamivir did not select for any viruses with reduced sensitivity. All the NA substitutions significantly reduced activity, but not the expression of the Anhui/1 NA. In contemporary N9 NAs, all substitutions tested significantly reduced NA enzyme function in the Yangtze River lineage background, but not in the Pearl River Delta lineage background. Overall, these findings suggest that zanamivir may be less likely than the other NAIs to select for resistance in A(H7N9) viruses and that the impact of substitutions that reduce NAI susceptibility or enzyme function may be less in A(H7N9) viruses from the Pearl River lineage.

We recently isolated an influenza A(H1N1)pdm09 E119D/H275Y neuraminidase (NA) variant from an immunocompromised patient who received oseltamivir and zanamivir therapies. This variant demonstrated cross resistance to zanamivir, oseltamivir, peramivir and laninamivir. In this study, the viral fitness of the recombinant wild-type (WT), E119D and E119D/H275Y A(H1N1)pdm09 viruses was evaluated in vitro and in experimentally-infected C57BL/6 mice and guinea pigs. In replication kinetics experiments, viral titers obtained with the E119D and E119D/H275Y recombinants were up to 2- and 4-log lower compared to the WT virus in MDCK and ST6GalI-MDCK cells, respectively. Enzymatic studies revealed that the E119D mutation significantly decreased the surface NA activity. In experimentally-infected mice, a 50% mortality rate was recorded in the group infected with the WT recombinant virus whereas no mortality was observed in the E119D and E119D/H275Y groups. Mean lung viral titers on day 5 post-inoculation for the WT (1.2 ± 0.57 × 10(8) PFU/ml) were significantly higher than those of the E119D (9.75 ± 0.41 × 10(5) PFU/ml, P

Despite the significant burden of influenza outbreaks, active disease monitoring has been largely absent in the Middle East, including Lebanon. In this study we characterized influenza virus in 440 nasopharyngeal swabs collected from patients with acute respiratory infections during two influenza seasons in Lebanon. Influenza A(H3N2) was dominant in the 2013/14 season while the A(H1N1)pdm09 and B/Yamagata strains were most prevalent in the 2014/15 season. All tested isolates were susceptible to 4 neuraminidase inhibitors (oseltamivir, zanamivir, peramivir and laninamivir). Genetic analysis of the haemagglutinin gene revealed multiple introductions of influenza viruses into Lebanon from different geographic sources during each season. Additionally, large data gaps were identified in the Middle East region, as indicated by the lack of current influenza sequences in the database from many countries in the region.