Clinical effectiveness of four neuraminidase inhibitors (oseltamivir, zanamivir, laninamivir, and peramivir) for children with influenza A and B in the 2014-2015 to 2016-2017 influenza seasons in Japan

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 2.13-times greater than that in patients aged 10-18 years (p = 0.012).

A meta-analysis of laninamivir octanoate for treatment and prophylaxis of influenza

BACKGROUND

Laninamivir octanoate is a recently developed inhaled neuraminidase inhibitor for treating influenza virus infection. We performed meta-analyses to clarify the efficacy of laninamivir octanoate on influenza treatment and prevention.

METHODS

MEDLINE and CENTRAL were searched to identify eligible studies. The log median time to event ratios (logMRs) and log odds ratios (logORs) were combined with meta-analysis.

RESULTS

Nine studies in treatment settings and three studies in prophylaxis settings were eligible for this meta-analysis. There was no significant difference between laninamivir octanoate and oseltamivir (8 studies, logMR 0.04, 95% CI [-0.05, 0.14]; P=0.36) or zanamivir (4 studies, logMR -0.01, 95% CI [-0.12, 0.11]; P=0.93) in alleviating fever. However, laninamivir octanoate was associated with significantly longer fever duration in treating H3N2 influenza as compared to oseltamivir (4 studies, logMR 0.29, 95% CI [0.00, 0.59]; P=0.047). Laninamivir octanoate was associated with significantly longer duration of fever as compared to peramivir (4 studies, logMR 0.46, 95% CI [0.14, 0.77]; P=0.004). Laninamivir octanoate significantly reduced the incidence of clinical influenza in post-exposure settings (3 studies, logOR -1.17, 95% CI [-1.72, -0.62]; P<0.001).

CONCLUSIONS

Overall, the efficacy of laninamivir octanoate in treating influenza was comparable to that of oseltamivir or zanamivir, but it should be noted that laninamivir octanoate was associated with significantly longer fever duration in treating influenza H3N2 as compared to oseltamivir and oseltamivir-resistant mutations in seasonal influenza H1N1 might have affected the results. Peramivir may be superior to laninamivir in treating influenza. Laninamivir octanoate is effective in preventing influenza in post-exposure settings as compared to placebo.

Intrapulmonary Pharmacokinetics of Laninamivir, a Neuraminidase Inhibitor, after a Single Nebulized Administration of Laninamivir Octanoate in Healthy Japanese Subjects

A single dose of laninamivir octanoate (LO) inhaled using a dry powder inhaler (DPI) is effective for the treatment and prophylaxis of influenza. Nebulizers are an option for pediatric and elderly patients who may have difficulty in using a DPI. A single-center, open-label study was conducted to evaluate the plasma and intrapulmonary pharmacokinetics (PK) of laninamivir after a single nebulized administration of LO in healthy male Japanese subjects for identifying a safe and effective dosage regimen for a nebulizer. A single dose of LO (40 to 320 mg) was administered using a nebulizer, and plasma concentrations of LO and laninamivir were analyzed up to 168 h after inhalation by validated liquid chromatography-tandem mass spectrometry methods. Subgroups of 6 subjects each underwent bronchoalveolar lavage at specified time intervals over 4 to 168 h following a single nebulized administration of LO (160 mg), and the concentrations in epithelial lining fluid (ELF) were calculated by the urea diffusion method. PK parameters were determined by noncompartment analysis. Inhaled nebulized LO was found to be safe and well tolerated up to the highest dose evaluated (320 mg). Plasma laninamivir concentrations increased almost dose proportionally. Laninamivir concentrations in ELF exceeded the 50% inhibitory concentrations for viral neuraminidase up to 168 h after the nebulized inhalation of 160 mg LO. Thus, similarly to the DPI, ELF concentration profiles of laninamivir after a single nebulized administration support its long-lasting effect against influenza virus infection. This study has been registered at JAPIC Clinical Trials Information (http://www.clinicaltrials.jp/) under registration no. JAPIC CTI-152996.

Factors associated with non-persistence to oral and inhaled antiviral therapies for seasonal influenza: a secondary analysis of a double-blind, multicentre, randomised clinical trial

OBJECTIVES

We aimed to evaluate and compare non-adherence to oral and inhaled antiviral therapies prescribed of a randomised clinical trial in outpatients with influenza A infection.

DESIGN

A parallel, three-arm, double-blinded trial randomly allocated antiviral therapies twice daily for 5 days: (1) oral oseltamivir plus inhaled zanamivir (arm OZ); (2) oseltamivir plus inhaled placebo (arm Opz); or (3) oral placebo plus inhaled zanamivir (arm poZ). Analysis of non-adherence was a secondary objective of the trial.

SETTINGS

Outpatients were enrolled by 145 general practitioners throughout France during the 2008-2009 seasonal influenza epidemics.

PARTICIPANTS

A total of 541 adults presenting with influenza-like illness for less than 36 hours.

PRIMARY OUTCOMES

Non-persistence, the time between inclusion and the last dose treated as a failure time, was used as the primary endpoint.

RESULTS

The proportions of patients who persisted on treatment until the end of prescription were estimated at 85.73% (±3.28%) for the oral route and 82.73% (±3.44%) for the inhaled route. Based on multivariable models, non-persistence was associated with a PCR confirmation of influenza for both the oral (HR=0.54, p=0.010) and inhaled (HR=0.59, p=0.018) drugs and antibiotic coprescriptions (HR=2.07, p=0.007; and HR=1.88, p=0.017, respectively) and active combination treatment (HR=1.71, p=0.035; and HR=1.58, p=0.035, respectively). The hazard of non-persistence of the inhaled therapy was increased compared with that of the oral therapy (HR=1.23, p=0.043).

CONCLUSION

In addition to the clinical and virological profiles of influenza infection, non-persistence may have been influenced by an active combination and the route of administration.

RCT REGISTRATION NUMBER

NCT00799760. This is a post-result analysis.

Intravenous zanamivir or oral oseltamivir for hospitalised patients with influenza: an international, randomised, double-blind, double-dummy, phase 3 trial

BACKGROUND

Neuraminidase inhibitors are effective for the treatment of acute uncomplicated influenza. However, there is an unmet need for intravenous treatment for patients admitted to hospital with severe influenza. We studied whether intravenous zanamivir was a suitable treatment in this setting.

METHODS

In this international, randomised, double-blind, double-dummy, phase 3 trial, we recruited patients aged 16 years or older with severe influenza admitted to 97 hospitals from 26 countries. We randomly assigned patients (1:1:1 stratified by symptom onset ≤4 days or 5-6 days) to receive 300 mg or 600 mg intravenous zanamivir, or standard-of-care (75 mg oral oseltamivir) twice a day for 5-10 days; patients were followed up for 28 days. The randomisation schedule, including stratification, was generated using GlaxoSmithKline's RandAll software. Patients, site study staff, and sponsor were masked to study treatment. The primary endpoint was time to clinical response-a composite of vital sign stabilisation and hospital discharge-in the influenza-positive population. The trial was powered to show an improvement of 1·5 days or greater with 600 mg intravenous zanamivir. Pharmacokinetic, safety, and virology endpoints were also assessed. This trial is registered with ClinicalTrials.gov, number NCT01231620.

FINDINGS

Between Jan 15, 2011, and Feb 12, 2015, 626 patients were randomly assigned to receive 300 mg intravenous zanamivir (n=201), 600 mg intravenous zanamivir (n=209), or 75 mg oral oseltamivir (n=205) twice a day; 11 patients discontinued the study before receiving any study treatment. 488 (78%) of 626 patients had laboratory-confirmed influenza. Compared with a median time to clinical response of 5·14 days in the 600 mg intravenous zanamivir group, the median time to clinical response was 5·87 days (difference of -0·73 days, 95% CI -1·79 to 0·75; p=0·25) in the 300 mg intravenous zanamivir group and 5·63 days (difference of -0·48 days, 95% CI -2·11 to 0·97; p=0·39) in the oseltamivir group. Four patients with influenza A/H1N1pdm09 in the oseltamivir group developed H275Y resistance mutations. Adverse events were reported in 373 (61%) of treated patients and were similar across treatment groups; the most common adverse events (300 mg intravenous zanamivir, 600 mg intravenous zanamivir, oseltamivir) were diarrhoea (10 [5%], 15 [7%], 14 [7%]), respiratory failure (11 [5%], 14 [7%], 11 [5%]), and constipation (7 [3%], 13 [6%], 10 [5%]). 41 (7%) treated patients died during the study (15 [7%], 15 [7%], 11 [5%]); the most common causes of death were respiratory failure and septic shock.

INTERPRETATION

Time to clinical response to intravenous zanamivir dosed at 600 mg was not superior to oseltamivir or 300 mg intravenous zanamivir. All treatments had a similar safety profile in hospitalised patients with severe influenza.

FUNDING

GlaxoSmithKline.

Duration of fever and other symptoms after the inhalation of laninamivir octanoate hydrate for influenza treatment; comparison among the four Japanese influenza seasons from 2011-2012 to 2014-2015

The duration of fever and other symptoms as markers of the clinical effectiveness of laninamivir octanoate hydrate (laninamivir) were investigated in the Japanese 2014-2015 influenza season and the results were compared with those of the previous three seasons, 2011-2012 to 2013-2014. From these four seasons, the data of 636 influenza A(H3N2) and 128 influenza B patients was available for analysis. No significant difference was found in their baseline characteristics. The median duration of fever for all A(H3N2) patients ranged from 32.0 to 41.0 h. The duration of fever in the 2014-2015 season was significantly shorter than that in the 2012-2013 and 2013-2014 seasons (p = 0.0204 and 0.0391, respectively), but the differences were within nine hours. The median duration of symptoms for A(H3N2) ranged from 80.0 to 89.0 h, with no significant difference among the four seasons (p = 0.2222). The median duration of fever for B patients ranged from 43.0 to 50.0 h, with no significant difference among the four seasons. The duration of the symptoms for B varied by season, but no significant difference was found among the four seasons. Over the four seasons, 44 adverse events were reported from among 921 patients, with all resolving without treatment. These results indicate the continuing effectiveness of laninamivir against influenza A(H3N2) and B, with no safety issues. It is unlikely that the clinical use of laninamivir has caused viral resistance in the currently epidemic viruses.

Long-acting Neuraminidase Inhibitor Laninamivir Octanoate as Post-exposure Prophylaxis for Influenza

BACKGROUND

A single administration of laninamivir octanoate, a long-acting neuraminidase inhibitor, has been proven to be effective in the treatment of influenza but not for post-exposure prophylaxis.

METHODS

We conducted a double-blind, multicenter, randomized, placebo-controlled study to determine if a single administration of laninamivir octanoate 40 mg was superior to placebo for post-exposure prophylaxis. Eligible participants who had cohabited with an influenza patient within 48 hours of symptom onset were randomly assigned (1:1:1) to 1 of 3 groups: 40 mg of laninamivir octanoate single administration (LO-40SD), 20 mg of laninamivir octanoate once daily for 2 days (LO-20TD), or placebo. The primary efficacy endpoint was the proportion of participants who developed clinical influenza (defined as influenza virus positive, an axillary temperature >37.5°C, and at least 2 symptoms) over a 10-day period.

RESULTS

A total of 803 participants were enrolled, with 801 included in the primary analysis. The proportions of participants with clinical influenza were 4.5% (12/267), 4.5% (13/269), and 12.1% (32/265) in the LO-40SD, LO-20TD, and placebo groups, respectively. A single administration of laninamivir octanoate 40 mg significantly reduced the development of influenza compared with placebo (P = .001). The relative risk reductions compared with the placebo group were 62.8% and 63.1% for the LO-40SD and LO-20TD groups, respectively. The incidence of adverse events in the LO-40SD group was similar to that of the LO-20TD and placebo groups.

CONCLUSIONS

A single administration of laninamivir octanoate was effective and well tolerated as post-exposure prophylaxis to prevent the development of influenza.

CLINICAL TRIALS REGISTRATION

JapicCTI-142679.

The Intranasal Application of Zanamivir and Carrageenan Is Synergistically Active against Influenza A Virus in the Murine Model

BACKGROUND

Carrageenan is a clinically proven and marketed compound for the treatment of viral upper respiratory tract infections. As infections caused by influenza virus are often accompanied by infections with other respiratory viruses the combination of a specific anti-influenza compound with the broadly active antiviral polymer has huge potential for the treatment of respiratory infections. Thus, the combination of the specific anti-influenza drug Zanamivir together with carrageenan in a formulation suitable for intranasal application was evaluated in-vitro and in-vivo.

PRINCIPAL FINDINGS

We show in-vitro that carrageenan and Zanamivir act synergistically against several influenza A virus strains (H1N1(09)pdm, H3N2, H5N1, H7N7). Moreover, we demonstrate in a lethal influenza model with a low pathogenic H7N7 virus (HA closely related to the avian influenza A(H7N9) virus) and a H1N1(09)pdm influenza virus in C57BL/6 mice that the combined use of both compounds significantly increases survival of infected animals in comparison with both mono-therapies or placebo. Remarkably, this benefit is maintained even when the treatment starts up to 72 hours post infection.

CONCLUSION

A nasal spray containing carrageenan and Zanamivir should therefore be tested for prevention and treatment of uncomplicated influenza in clinical trials.

Zanamivir versus trivalent split virus influenza vaccine: a pilot randomized trial

BACKGROUND

Healthcare workers may be exposed to people with respiratory viral infections more often than other working adults. Understanding the risk and the effectiveness of different preventive measures is of great importance.

OBJECTIVES

To estimate adherence to prophylactic antiviral medication for a full influenza season, to the compare efficacy of antiviral prophylaxis to that of the seasonal influenza vaccine and to identify exposures that increase risk of acute respiratory illnesses (ARI) in healthy adults.

METHODS

Participants were randomized 1:2 to receive the 2008-2009 influenza vaccine or daily prophylaxis with 10 mg of zanamivir during the season. Web-based questionnaires collected information on demographics, symptoms, exposures, medication use and side effects.

RESULTS

Sixty-four healthy adults were recruited in November 2008. Three of 40 active participants discontinued zanamivir due to side effects; the remaining 37 took >85% of scheduled doses for a median of 121 days. Symptomatic, laboratory-confirmed influenza was detected in one person randomized to zanamivir (2·5%) and 2/20 (10%) who received the vaccine (P = 0·25). Forty-seven participants reported 109 episodes of ARI. Factors associated with an ARI were exposure to a spouse (OR 7·2), child (OR 2·4) or patient (OR 2·0) with symptoms of an ARI in the previous 7 days.

CONCLUSIONS

Breakthrough influenza infection occurred in both vaccinated participants and those receiving antiviral prophylaxis. Most adults were willing and able to comply with season-long prophylaxis. Report of recent exposure to family members and patients with an ARI increased the risk of developing an ARI in healthy adults.

Anti-influenza activity of Alchemilla mollis extract: possible virucidal activity against influenza virus particles

Influenza virus infection is a major public health problem that leads to significant morbidity and mortality. The emergence of resistance to the currently available anti-influenza agents has necessitated the development of new drugs with novel targets. Studying known ethno-medicinal plants is a promising approach for the discovery of new antiviral compounds. Alchemilla mollis is used in traditional medicine in Europe for different indications, including minimizing the symptoms of a sore throat. In this study, we found that A. mollis extract has anti-influenza activity, and investigated the mechanism underlying its inhibition of influenza virus replication. Plaque assays demonstrated that treatment of cells with A. mollis extract prior to infection did not inhibit influenza virus infection. However, plaque formation was markedly reduced when infected cells were overlaid with an agarose gel containing A. mollis extract. In addition, exposure of the virus to A. mollis extract prior to infection and treatment of cells during virus infection significantly suppressed plaque formation. Influenza virus-induced hemagglutination of chicken red blood cells was inhibited by A. mollis extract treatment. The inhibitory effect was observed against influenza A virus subtypes H1N1, H3N2, and H5N2. These findings suggest that A. mollis extract has virucidal or neutralizing activity against influenza virus particles. Furthermore, inhibitory effect of zanamivir synergistically increased after combination with A. mollis extract. Our results suggest that A. mollis extract has the potential to be developed as an antiinfluenza agent.

Permeability enhancers dramatically increase zanamivir absolute bioavailability in rats: implications for an orally bioavailable influenza treatment

We have demonstrated that simple formulations composed of the parent drug in combination with generally regarded as safe (GRAS) permeability enhancers are capable of dramatically increasing the absolute bioavailability of zanamivir. This has the advantage of not requiring modification of the drug structure to promote absorption, thus reducing the regulatory challenges involved in conversion of an inhaled to oral route of administration of an approved drug. Absolute bioavailability increases of up to 24-fold were observed when Capmul MCM L8 (composed of mono- and diglycerides of caprylic/capric acids in glycerol) was mixed with 1.5 mg of zanamivir and administered intraduodenally to rats. Rapid uptake (t_max of 5 min) and a C_max of over 7200 ng/mL was achieved. Variation of the drug load or amount of enhancer demonstrated a generally linear variation in absorption, indicating an ability to optimize a formulation for a desired outcome such as a targeted C_max for enzyme saturation. No absorption enhancement was observed when the enhancer was given 2 hr prior to drug administration, indicating, in combination with the observed t_max, that absorption enhancement is temporary. This property is significant and aligns well with therapeutic applications to limit undesirable drug-drug interactions, potentially due to the presence of other poorly absorbed polar drugs. These results suggest that optimal human oral dosage forms of zanamivir should be enteric-coated gelcaps or softgels for intraduodenal release. There continues to be a strong need and market for multiple neuraminidase inhibitors for influenza treatment. Creation of orally available formulations of inhibitor drugs that are currently administered intravenously or by inhalation would provide a significant improvement in treatment of influenza. The very simple GRAS formulation components and anticipated dosage forms would require low manufacturing costs and yield enhanced convenience. These results are being utilized to design prototype dosage forms for initial human pharmacokinetic studies.

Oseltamivir and inhaled zanamivir as influenza prophylaxis in Thai health workers: a randomized, double-blind, placebo-controlled safety trial over 16 weeks

OBJECTIVES

Long-term chemoprophylaxis using neuraminidase inhibitors may be needed during influenza epidemics but safety data are limited to several weeks. We sought to assess the tolerability of oseltamivir and zanamivir as primary prophylaxis over 16 weeks.

METHODS

We conducted a parallel group, double blind, 2 (active drug) :1 (placebo) randomized trial of oral oseltamivir/placebo or inhaled zanamivir/placebo over 16 weeks in healthy, Thai hospital professionals at two Bangkok hospitals. The primary endpoint was study withdrawal due to drug-related (possibly, probably, definitely) serious or adverse events (AEs) graded ≥ 2.

RESULTS

Recruited subjects numbered 129 oseltamivir/65 placebo and 131 zanamivir/65 placebo. A total of 102 grade ≥ 2 AEs were reported or detected in 69 subjects: 23/129 (17.8%) versus 15/65 (23.1%) (P=0.26), and 23/131 (17.6%) versus 8/65 (12.3%) (P=0.28). Intercurrent infections/fevers [26/102 (25.5%)], abnormal biochemistry [25/102 (24.5%)] and gastrointestinal symptoms [18/102 (17.6%)] were the most frequently reported AEs. There were no drug-related study withdrawals. Eight serious AEs were all due to intercurrent illnesses. Laboratory, lung function and ECG parameters were similar between drugs and placebos.

CONCLUSIONS

Oseltamivir and zanamivir were well tolerated in healthy hospital professionals. Both drugs can be recommended for primary influenza prophylaxis for up to 16 weeks.

Clinical efficacy of long-acting neuraminidase inhibitor laninamivir octanoate hydrate in postmarketing surveillance

Laninamivir octanoate hydrate (laninamivir) is a long-acting neuraminidase inhibitor which requires only a single inhaled dose to fully treat infection by the influenza virus. In Japan, this drug was launched in October 2010 as a new treatment for the influenza virus. A postmarketing surveillance study was conducted in the 2010/2011 influenza season to assess the efficacy of this drug in clinical settings. For 3542 patients evaluated for efficacy (type A, n = 3179; type B, n = 342, unknown type, n = 3), including the day of drug administration, the median duration to fever resolution was three days, and the median duration to relief from influenza symptoms was four days. Based on the judgment of participating physicians, the efficacy rate was 97.6 % for type A influenza, 93.3 % for type B influenza, and 100 % in unknown types. "Treatment failure," as judged by participating physicians, was most closely correlated with the inhalation status of laninamivir. Despite laninamivir requiring only the administration of a single dose, it was confirmed to be an effective treatment in more than 90 % of patients with type A or type B influenza virus infections. This drug was considered to be useful for the treatment of influenza infections due to ease of use and its improvement of compliance. It became clear that the efficacy of laninamivir depended strongly on the status of inhalation, and thus careful and detailed instructions on the correct method of inhalation were considered to be important in order to obtain reliable therapeutic effects.

An uncontrolled open-label, multicenter study to monitor the antiviral activity and safety of inhaled zanamivir (as Rotadisk via Diskhaler device) among Chinese adolescents and adults with influenza-like illness

BACKGROUND

It is the first multicenter clinical study in China to investigate zanamivir use among Chinese adolescents and adults with influenza-like illness (ILI) since 2009, when inhaled zanamivir (RELENZA(®)) was marketed in China.

METHODS

An uncontrolled open-label, multicentre study to evaluate the antiviral activity, and safety of inhaled zanamivir (as Rotadisk via Diskhaler device); 10 mg administered twice daily for 5 days in subjects ≥ 12 years old with ILI. Patients were enrolled within 48 hours of onset and followed for eight days. Patients were defined as being influenza-positive if the real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) test had positive results.

RESULTS

A total of 400 patients ≥ 12 years old were screened from 11 centers in seven provinces from March 2010 to January 2011. Three hundred and ninety-two patients who took at least one dose of zanamivir were entered into the safety analysis. The mean age was 33.8 years and 50% were male. Cardiovascular diseases and diabetes were the most common comorbidities. All the reported adverse events, such as rash, nasal ache, muscle ache, nausea, diarrhea, headache, occurred in less than 1% of subjects. Mild sinus bradycadia or arrhythmia occurred in four subjects (1%). Most of the adverse events were mild and did not require any change of treatment. No severe adverse events (SAE) or fatal cases were reported. Bronchospasm was found in a 38 years old woman whose symptoms disappeared after stopping zanamivir and without additional treatment. All the 61 influenza virus isolates (43 before enrollment, 18 during treatment) proved to be sensitive to zanamivir.

CONCLUSIONS

Zanamivir is well tolerated by Chinese adolescents and adults with ILIs. There is no evidence for the emergence of drug-resistant isolates during treatment with zanamivir.

Intravenous zanamivir in critically ill patients due to pandemic 2009 (H1N1) influenza A virus

INTRODUCTION

The 2009 (H1N1) influenza A pandemic started in April 2009 and has since spread globally. We have noticed that critically ill patients with confirmed pandemic 2009 (H1N1) influenza A require mechanical ventilation. This paper describes the use of intravenous zanamivir in this group of patients.

METHODS

Patients who had severe pneumonia with 2009 (H1N1) influenza A and required intravenous zanamivir were referred to the Infectious Diseases Department of our institution. Clinical data was collected from these patients. Clinical samples were sent to the National Public Health Laboratory for sequencing.

RESULTS

A total of five patients used intravenous zanamivir from April 8 to May 8, 2010. Only one death was reported. There were no side effects attributable to the use of intravenous zanamivir. H275 mutation, which confers resistance to oseltamivir, was seen in a subpopulation of the virus in one case.

CONCLUSION

Physicians can consider using intravenous zanamivir for the treatment of critically ill patients with 2009 (H1N1) influenza A infection.

Influenza-associated monophasic neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory demyelinating disorder characterized by optic neuritis and acute myelitis. A parainfectious pathogenesis may play a partial role in the development of this disorder. Several viral infections are known to cause NMO. Here we report the case of a 15-year-old girl diagnosed with postinfluenza monophasic NMO. The patient developed sudden fever and chills, and the rapid diagnostic test for influenza was positive. She was diagnosed as influenza A and was treated with zanamivir hydrate (10 mg/day, inhalation). Three days later, she complained of dysuria and dysesthesia in the lower extremities. After nine days, she experienced blurred vision bilaterally. Neurological examination revealed visual disturbance, dysuria, dysesthesia and hyperreflexia in the lower extremities. Her visual acuity was counting fingers in OD and 2/100 in OS. Pupillary size was 4.0 mm and light reflexes were sluggish on both sides. Ophthalmoscopy showed marked edema of the optic discs. Serum influenza immunoglobulin M antibodies were elevated and serum anti-aquaporin 4 (AQP4) antibodies were undetectable. Spinal cord magnetic resonance imaging (MRI) displayed longitudinally extensive lesions in the thoracic cord. Brain MRI disclosed three subcortical lesions. The patient fulfilled the revised diagnostic criteria for NMO (2006). After methylprednisolone pulse therapy followed by oral administration of prednisolone, visual dysfunction, dysuria, limb dysesthesia and hyperreflexia were improved. Subsequently, she experienced no attacks for 3 years. This is the first case report of influenza A-associated NMO with such features of postinfectious NMO as a pediatric onset, monophasic course and anti-AQP4 antibody-seronegative status.

[Etiotropic therapy of influenza: lessons from the last pandemic]

Analysis of the experience gained during the last pandemic of 'swine' influenza A (H1N1) sw1 is presented with reference to clinical studies and etiotropic therapy. The mechanism of development of severe pneumonia as a result of mutations at the binding site of hemagglutinin receptor enhancing a2'-3'-sialoside specificity and pneumotropism of the virus is described. The data on the efficiency of Ingavirin, a new Russian antiviral for the treatment of influenza, are reported.

[In vitro and in vivo effects of a long-acting anti-influenza agent CS-8958 (laninamivir octanoate, Inavir) against pandemic (H1N1) 2009 influenza viruses]

Laninamivir is a novel neuraminidase inhibitor of influenza viruses and it has been reported that its prodrug, CS-8958 shows a long-lasting characteristics. Using viruses isolated in Nagasaki of pandemic (H1N1) 2009 influenza virus which cause pandemic in 2009, it was shown that laninamivir has a strong inhibitory activities against their neuraminidases and virus replication in cultured cells, and strong binding stability to the virus NA. Furthermore, a single intranasal administration of CS-8958 showed a superior reduction of virus load in lungs in mouse infection model. These suggest that CS-8958 will work as a long-acting neuraminidase inhibitor to an infection with pandemic (H1N1) 2009 influenza viruses as well.

[Change of strategies for novel and seasonal flu during pregnancy]

In 2009/10 season pandemic (H1N1) 2009 epidemic, pregnant women were recognized as high risk group, and taken different measures from non-pregnant adults. This new recommendations for pregnant women was also different from Japanese conventional management for pregnant women suffering from seasonal flu. The policy of these recommendations of novel flu for pregnant women was highlighted to aggressive preventions and treatments. To put it concretely, 1) pregnant women will be preferably accepted influenza virus vaccines during all the period of pregnancy, 2) early administration of oseltamivir/zanamivir to pregnant women will not be hesitated. This new recommendation for pregnancy will be probably applied in this 2010/11 season too.

[Influenza A H1N1v treated with extracorporeal membrane oxygenation]

A 37-year-old woman with body mass index > 30 was admitted to hospital with severe pneumonia due to H1N1v. Thoracic X-ray showed bilateral, diffuse infiltrates. There was no sign of complicating bacterial infection and all microbiological tests of tracheal secretion, blood and urine were negative. Polymerase chain reaction test for H1N1v was positive until day ten. No mutations were found in the virus. The patient was given oseltamivir tablets and inhalable zanamivir as well as antibiotics. The patient was treated with extra-corporal membrane oxygenation (EcmO) for 12 days followed by ventilator weaning. The patient had no neurological sequelae.

Emerging antiviral targets for influenza A virus

The potential threat of a pandemic caused by H5N1 influenza A viruses has stimulated increased research on developing new antivirals against influenza A viruses. Current antivirals are directed against the M2 protein (named adamantanes) and the neuraminidase (named zanamivir and oseltamivir). However, both seasonal and H5N1 influenza A viruses have developed resistance to adamantanes and oseltamivir. Accordingly, new antivirals directed at the M2 and neuraminidase proteins, and against the hemagglutinin protein, are being developed. In addition, elucidation of the structural basis for several crucial functions of other viral proteins (specifically the non-structural NS1A protein, the nucleoprotein and the viral polymerase) has identified novel targets for the development of new antivirals. Here, we describe how functional and structural studies led to the discovery of these novel targets and also how structural information is facilitating the rational design of new drugs against previously identified targets.

Zanamivir: new indication. Influenza: in children as in adults, symptom relief or vaccination

Zanamivir has not been shown to reduce the incidence of influenza complications, whether used as prevention or cure. And the risk of adverse effects and the selection of resistant viruses argue against the use of this antiviral drug.

Evaluation of intravenous zanamivir against experimental influenza A (H5N1) virus infection in cynomolgus macaques

We investigated the prophylactic and therapeutic efficacy of an intravenous (IV) formulation of zanamivir in a macaque infection model for highly pathogenic influenza A (H5N1) virus. Antiviral efficacy was dose-dependent, with no reduction in viral load observed at 2 mg/kg, but a significant reduction observed at 10 mg/kg (p=0.039) and at 20 mg/kg in the combined prophylactic and therapeutic groups (p=0.049) with both prophylaxis (commencing 12 h before infection) and therapy (commencing 4 h after infection) showing similar reductions in viral load. Combined gross pathology and microscopic pneumonia scores in the treated animals relative to untreated controls were significantly reduced at 10 mg/kg (p=0.02) and at 20 mg/kg in the prophylaxis group (p=0.02), but were not significant in the treatment group (p=0.145). In this new animal model for evaluation of influenza antivirals, despite variability observed between individual animals, IV zanamivir showed evidence of efficacy against highly pathogenic H5N1 virus.

Inhaled zanamivir versus rimantadine for the control of influenza in a highly vaccinated long-term care population

BACKGROUND

Despite vaccination, influenza commonly causes morbidity and mortality in institutional settings. Influenza control with rimantadine and amantadine is limited by emergence and transmission of drug-resistant influenza A variants, ineffectiveness against influenza B, and toxicity. This study evaluated the efficacy and tolerability of zanamivir versus rimantadine for influenza outbreak control in long-term care facilities.

METHODS

This double-blind, randomized, controlled study prospectively enrolled nursing home residents for 3 influenza seasons (1997 to 2000). Vaccine was offered to all subjects. Following influenza outbreak declaration, subjects were randomized to inhaled zanamivir 10 mg or standard of care (rimantadine 100 mg for influenza A or placebo for influenza B) once daily for 14 days. The proportion of randomized subjects developing symptomatic, laboratory-confirmed influenza during prophylaxis was the primary endpoint.

RESULTS

Of 482 randomizations (238 zanamivir, 231 rimantadine, 13 placebo), 96% of subjects were elderly or had high-risk conditions; over 90% were vaccinated. Symptomatic, laboratory-confirmed influenza occurred in 3% of zanamivir subjects and 8% of rimantadine subjects during chemoprophylaxis (P = .038; additional protective efficacy for zanamivir over rimantadine = 61%). Since only 25 subjects were randomized during 2 influenza B outbreaks and none developed influenza, the influenza B data were excluded from further analysis. Zanamivir was well tolerated and unassociated with emergence of resistant virus; rimantadine-resistant variants were common.

CONCLUSIONS

This is the first prospective, controlled study demonstrating effectiveness of chemoprophylaxis for influenza outbreak control. Zanamivir prevents symptomatic, laboratory-confirmed influenza more effectively than rimantadine, is unassociated with resistant virus, and has a favorable safety profile. Zanamivir is an appropriate alternative for influenza outbreak control among institutionalized vaccinated elderly.

Antiviral management of seasonal and pandemic influenza

The goals of antiviral treatment for influenza are to decrease symptoms and functional disability and, more important, to decrease associated complications, hospitalizations, and mortality. Four drugs have been approved for treatment of and prophylaxis against influenza in the United States, but they are underutilized. The M2 ion channel inhibitors amantadine and rimantadine are effective for prophylaxis, and they decrease the duration of symptoms if they are used for early treatment of influenza A. The rapid emergence of resistance during therapy and, recently, the circulation of resistant H3N2 viruses in the community have decreased the usefulness of these M2 ion channel inhibitors. Early therapy with neuraminidase (NA) inhibitors, either oseltamivir or zanamivir, reduces the duration of symptoms, the duration of disability, and the risk of lower respiratory tract complications. Oseltamivir has been shown to decrease antibiotic use, the number of hospitalizations, and, probably, the risk of death after influenza. NA inhibitors might provide substantial benefits in the treatment of pandemic influenza, with reductions in the numbers of hospitalizations and deaths occurring if such treatment (1) is made available in sufficient time, through rapid distribution, and (2) is available in sufficient quantities as a result of stockpiling. Both of the aforementioned NA inhibitors are highly effective for prophylaxis. Geographically targeted mass chemoprophylaxis might contain the spread of a pandemic virus, but multiple hurdles to successful implementation exist. Resistance to oseltamivir occurs with the H274Y variant in viruses that contain N1; however, to date, such variants have been less fit, have not been transmitted from person to person, and have retained susceptibility to zanamivir. Alternative agents and approaches, including parenteral and combination therapy, for the treatment of influenza are needed in the near and long term.

Prevention and treatment of influenza in high-risk groups: children, pregnant women, immunocompromised hosts, and nursing home residents

The pediatric population experiences preventable hospitalizations and serves as a reservoir for influenza and its transmission to other children as well as adults. As a consequence, the Advisory Committee on Immunization Practices has recommended initiating influenza immunization of children as young as 6 months of age through 23 months of age and, recently, up to 5 years of age. However, immunization of older children has not yet become a priority of the US Public Health Service. As a consequence, the importance of antiviral agents, particularly neuraminidase (NA) inhibitors, cannot be overemphasized. From an epidemiological perspective, influenza resulted in higher childhood mortality than did Bordetella pertussis infection in 2003-2004. During that season, 153 children died of influenza, and two-thirds were <5 years of age. Importantly, nearly 50% of these children were previously healthy, with no underlying illness. Currently, 2 NA inhibitors are approved for the treatment of influenza in children. Zanamivir is approved for children >7 years of age, and oseltamivir is approved for children >1 year of age. Arguably, the younger children are at particular risk for influenza complications and hospitalization. In placebo-controlled studies in children >1 year of age, oseltamivir therapy accelerated resolution of clinical illness and defervescence and decreased both the incidence of otitis media and the concomitant use of antibiotics. However, oseltamivir is not currently approved for children <1 year of age. Three clinical toxicology studies identified neurotoxicity in newborn rats administered this medication. In these preclinical toxicology studies, the dose of oseltamivir exceeded that which would be used in humans. In addition, the metabolism of oseltamivir is different in rats than in humans. A key component of influenza therapy is the possibility for development of resistance. Although in studies performed in North America, resistance was not a frequent event, it has been documented in Japanese children treated with this medication; the adequacy of the dose used has been questioned. Children represent only one unique study population among others. Individuals who are at increased risk for influenza infection include the elderly, the immunocompromised, and pregnant women. Collectively, antiviral medications must be evaluated in populations in which they have not yet been assessed. The development of additional antiviral drugs is an important recommendation for the future, so that antiviral resistance can be circumvented. Similarly, availability of drugs for children <1 year of age is mandatory.

American Academy of Pediatrics Committee on Infectious Diseases. Antiviral therapy and prophylaxis for influenza in children

Antiviral agents are available that are safe and effective for the treatment and prophylaxis of influenza virus infections in children. The neuraminidase inhibitors (oseltamivir [Tamiflu] and zanamivir [Relenza]) are preferred agents because of current widespread resistance to the adamantanes (amantadine [Symmetrel] and rimantadine [Flumadine]). Therapy should be provided to children with influenza infection who are at high risk of severe infection and to children with moderate-to-severe influenza infection who may benefit from a decrease in the duration of symptoms. Prophylaxis should be provided (1) to high-risk children who have not yet received immunization and during the 2 weeks after immunization, (2) to unimmunized family members and health care professionals with close contact with high-risk unimmunized children or infants who are younger than 6 months, and (3) for control of influenza outbreaks in unimmunized staff and children in an institutional setting. Testing of current H5N1 avian influenza virus isolates, the potential agents of pandemic influenza, suggests susceptibility to oseltamivir and zanamivir. Because no prospective data exist on the efficacy of these agents in humans for H5N1 strains, the dosage and duration of therapy in adults and children may differ from those documented to be effective for epidemic influenza strains.

Oseltamivir: new indication. Prevention of influenza in at-risk children: vaccination is best

(1) Complications of influenza are rare in children and mainly affect children with serious birth defects or chronic underlying disorders such as cystic fibrosis and severe asthma. (2) Oseltamivir is the second antiviral drug, after amantadine, to be marketed in the European Union for the prevention of influenza in children aged from 1 to 12 years. (3) The clinical evaluation of oseltamivir in this indication is limited to a retrospective subgroup analysis of an unblinded trial versus no treatment. The data suggest that oseltamivir is at best only modestly effective in reducing the incidence of laboratory-confirmed influenza (about 7% versus 19%). With zanamivir, the incidence of laboratory-confirmed influenza was about 2%, versus 6% to 15% in the placebo groups in several trials. As of 5 January 2007, zanamivir had not been marketed for paediatric use in France. With amantadine, the incidence was about 3% to 9%, depending on the trial, versus 9% to 30% on placebo. Amantadine has only been shown to have an effect on type A influenza virus and is only available in tablet form (unsuitable for young children). In summary, there is no firm evidence that antiviral prophylaxis reduces the rate of influenza complications in children. (4) Severe cutaneous and neurological adverse effects have been reported in children treated with oseltamivir. Pharmacovigilance studies show a risk of angioedema and toxic epidermal lysis with oseltamivir. (5) There are worrisome reports of influenza virus strains resistant to available antivirals. (6) In practice, oseltamivir is not sufficiently effective or safe for the prevention of influenza in children, which does not justify its use other than in clinical trials.

Inhaled Zanamivir Versus Placebo for the Prevention of Influenza Outbreaks in an Unvaccinated Long-term Care Population

BACKGROUND

Antiviral chemoprophylaxis effectiveness for influenza control has not been prospectively established for unvaccinated residents of long-term care facilities. This study evaluated the efficacy and tolerability of zanamivir against the standard of care (no intervention, ie, placebo) for influenza outbreak control in a largely unvaccinated institutionalized population.

OBJECTIVE

To evaluate the efficacy and tolerability of zanamivir versus placebo for influenza outbreak control in long-term care facilities.

METHODS

This double-blind, randomized, placebo-controlled study prospectively enrolled/followed residents of long-term care facilities (LTCF) at 12 centers for 1 to 3 influenza seasons (1997 to 2000). Following influenza outbreak declaration, asymptomatic subjects were randomized for prophylaxis to inhaled zanamivir 10 mg or inhaled placebo given once daily for 14 days. The proportion of randomized subjects who during prophylaxis developed symptomatic, laboratory-confirmed influenza (SLCI) was the primary end point.

RESULTS

Influenza outbreaks were explosive. The attack rates varied from 9.5 to 14.8 per 100 residents. Of 1763 consents given and resulting in 494 randomizations, 49% received zanamivir and 51% placebo; 66% were elderly and 9% were vaccinated. SLCI occurred in 6% of zanamivir and 9% of placebo subjects (P = .355; protective efficacy for zanamivir = 29%, 95% confidence interval 31% to 62%), and symptomatic influenza confirmed by culture in 2% and 6%, respectively (P = .052; protective efficacy = 65%, 95% confidence interval 8.5% to 86%). Zanamivir use was also associated with a 70% (95% confidence interval 13% to 89%) reduction in laboratory-confirmed influenza with fever (2% vs 6%, P = .043). Influenza B was not detected. Zanamivir was well tolerated. No virus isolate demonstrated zanamivir resistance.

CONCLUSIONS

The protective efficacy of zanamivir versus placebo for SLCI was marginal, for all laboratory confirmed illnesses, but significant against culture proven and febrile influenza, suggesting zanamivir can be effective for outbreak control and symptom reduction of unvaccinated institutionalized residents. Zanamivir had an acceptable safety profile in elderly, high-risk LTCF residents and was not associated with the emergence of resistant strains.