Antiviral therapy for influenza : a clinical and economic comparative review

Modular Biomimetic Strategy Enables Discovery and SAR Exploration of Oxime Macrocycles as Influenza A Virus (H1N1) Inhibitors

Although vaccination remains the prevalent prophylactic means for controlling Influenza A virus (IAV) infections, novel structural antivirus small-molecule drugs with new mechanisms of action for treating IAV are highly desirable. Herein, we describe a modular biomimetic strategy to expeditiously achieve a new class of macrocycles featuring oxime, which might target the hemagglutinin (HA)-mediated IAV entry into the host cells. SAR analysis revealed that the size and linker of the macrocycles play an important role in improving potency. Particularly, as a 14-membered macrocyclic oxime, 37 exhibited potent inhibitory activity against IAV H1N1 with an EC50 value of 23 nM and low cytotoxicity, which alleviated cytopathic effects and protected cell survival obviously after H1N1 infection. Furthermore, 37 showed significant synergistic activity with neuraminidase inhibitor oseltamivir in vitro.

Epidemiology of influenza over a ten-year period in Belgium: overview of the historical and current evidence

BACKGROUND

Generally influenza, a contagious respiratory disease, leads to mild illness, but can present as a severe illness with significant complications for some. It entails significant health challenges and an economic burden. Annual vaccination is considered the most effective preventive measure against influenza, especially in high-risk groups.

METHOD

Epidemiological, demographic and vaccination data of influenza from 2009-to-2019 is collected from Sciensano, the Belgian Institute for Health. Sciensano monitors influenza virus through two surveillances: the Influenza-Like Illness (ILI) surveillance in primary care and the Severe Acute Respiratory Infections (SARI) surveillance in hospital settings.

RESULTS

49.6% [± 8.5] of all ILI-samples tested positive in this period. Influenza A was the dominant circulating type, accounting for 73.7% [± 27.5] of positive samples, while influenza B accounted for 24.3% [± 26.7]. For SARI-surveillance, the average rate of samples tested positive was 36.3% [± 9.3]. Influenza A was responsible for respectively 77.7% [± 23.8] of positive samples and influenza B for 22.2% [± 23.7]. Since 2010, epidemics typically lasted about 9.3 weeks [± 2.7]. From 2012 to 2019 the average vaccine effectiveness was 34.9% [± 15.3].

CONCLUSION

Influenza is quickly considered a trivial disease, but can have substantial repercussions. It remains difficult to identify the level of treat of influenza due to antigenic evolution. Measures to prevent, control and treat are needed. Vaccines that provide broader and more durable protection that can be produced more rapidly could be a potential solution.

Synthesis, Optimization, and Structure-Activity Relationships of Imidazo[1,2-a]pyrimidines as Inhibitors of Group 2 Influenza A Viruses

The influenza A virus (IAV) is a highly contagious virus that causes pandemics and seasonal epidemics, which are major public health issues. Current anti-influenza therapeutics are limited partly due to the continuous emergence of drug-resistant IAV strains; thus, there is an unmet need to develop novel anti-influenza therapies. Here, we present a novel imidazo[1,2-a]pyrimidine scaffold that targets group 2 IAV entry. We have explored three different regions of the lead compound, and we have developed a series of small molecules that have nanomolar activity against oseltamivir-sensitive and -resistant forms of group 2 IAVs. These small molecules target hemagglutinin (HA), which mediates the viral entry process. Mapping a known small-molecule-binding cavity of the HA structure with resistant mutants suggests that these molecules bind to that cavity and block HA-mediated membrane fusion.

Discovery and development of oseltamivir at Gilead Sciences

John Martin's untimely death in March 2021 was a huge loss for us personally, Gilead Sciences, the company he built over 30 years and the scientific community concerned with antiviral therapies. We wish to honor John's legacy by retelling the discovery and history of Tamiflu and his contributions to it. Without his vision, persistence, and keen eye for opportunities, Tamiflu would not exist and Gilead's path would not have been the same. His strategic thinking around the first oral flu drug is still quite relevant today, when we are still in the SARS-CoV-2 pandemic. John explained it simply in an interview with the Science History Institute in May 2020: "…most of my colleagues, we travel with Tamiflu when we go internationally, because it works for treatment and prevention, and hopefully, there will be a solution like that, eventually, for the Covid virus in addition to vaccines. Most people will get a flu vaccine every year, but there is still disease, we need a pill for treatment and prevention.".

Discovery of Antivirals Using Phage Display

The latest coronavirus disease outbreak, COVID-19, has brought attention to viral infections which have posed serious health threats to humankind throughout history. The rapid global spread of COVID-19 is attributed to the increased human mobility of today's world, yet the threat of viral infections to global public health is expected to increase continuously in part due to increasing human-animal interface. Development of antiviral agents is crucial to combat both existing and novel viral infections. Recently, there is a growing interest in peptide/protein-based drug molecules. Antibodies are becoming especially predominant in the drug market. Indeed, in a remarkably short period, four antibody therapeutics were authorized for emergency use in COVID-19 treatment in the US, Russia, and India as of November 2020. Phage display has been one of the most widely used screening methods for peptide/antibody drug discovery. Several phage display-derived biologics are already in the market, and the expiration of intellectual property rights of phage-display antibody discovery platforms suggests an increment in antibody drugs in the near future. This review summarizes the most common phage display libraries used in antiviral discovery, highlights the approaches employed to enhance the antiviral potency of selected peptides/antibody fragments, and finally provides a discussion about the present status of the developed antivirals in clinic.

Nanotechnology for virus treatment

The continued emergence of novel viruses poses a significant threat to global health. Uncontrolled outbreaks can result in pandemics that have the potential to overburden our healthcare and economic systems. While vaccination is a conventional modality that can be employed to promote herd immunity, antiviral vaccines can only be applied prophylactically and do little to help patients who have already contracted viral infections. During the early stages of a disease outbreak when vaccines are unavailable, therapeutic antiviral drugs can be used as a stopgap solution. However, these treatments do not always work against emerging viral strains and can be accompanied by adverse effects that sometimes outweigh the benefits. Nanotechnology has the potential to overcome many of the challenges facing current antiviral therapies. For example, nanodelivery vehicles can be employed to drastically improve the pharmacokinetic profile of antiviral drugs while reducing their systemic toxicity. Other unique nanomaterials can be leveraged for their virucidal or virus-neutralizing properties. In this review, we discuss recent developments in antiviral nanotherapeutics and provide a perspective on the application of nanotechnology to the SARS-CoV-2 outbreak and future virus pandemics.

Self-Assembled Nanoparticles: Exciting Platforms for Vaccination

Vaccination is successfully advanced to control several fatal diseases and improve human life expectancy. However, additional innovations are required in this field because there are no effective vaccines to prevent some infectious diseases. The shift from the attenuated or inactivated pathogens to safer but less immunogenic protein or peptide antigens has led to a search for effective antigen delivery carriers that can function as both antigen vehicles and intrinsic adjuvants. Among these carriers, self-assembled nanoparticles (SANPs) have shown great potential to be the best representative. For the nanoscale and multiple presentation of antigens, with accurate control over size, geometry, and functionality, these nanoparticles are assembled spontaneously and mimic pathogens, resulting in enhanced antigen presentation and increased cellular and humoral immunity responses. In addition, they may be applied through needle-free routes due to their adhesive ability, which gives them a great future in vaccination applications. This review provides an overview of various SANPs and their applications in prophylactic vaccines.

Development of effective anti-influenza drugs: congeners and conjugates - a review

Influenza is a long-standing health problem. For treatment of seasonal flu and possible pandemic infections, there is a need to develop new anti-influenza drugs that have good bioavailability against a broad spectrum of influenza viruses, including the resistant strains. Relenza™ (zanamivir), Tamiflu™ (the phosphate salt of oseltamivir), Inavir™ (laninamivir octanoate) and Rapivab™ (peramivir) are four anti-influenza drugs targeting the viral neuraminidases (NAs). However, some problems of these drugs should be resolved, such as oral availability, drug resistance and the induced cytokine storm. Two possible strategies have been applied to tackle these problems by devising congeners and conjugates. In this review, congeners are the related compounds having comparable chemical structures and biological functions, whereas conjugate refers to a compound having two bioactive entities joined by a covalent bond. The rational design of NA inhibitors is based on the mechanism of the enzymatic hydrolysis of the sialic acid (Neu5Ac)-terminated glycoprotein. To improve binding affinity and lipophilicity of the existing NA inhibitors, several methods are utilized, including conversion of carboxylic acid to ester prodrug, conversion of guanidine to acylguanidine, substitution of carboxylic acid with bioisostere, and modification of glycerol side chain. Alternatively, conjugating NA inhibitors with other therapeutic entity provides a synergistic anti-influenza activity; for example, to kill the existing viruses and suppress the cytokines caused by cross-species infection.

A small-molecule fusion inhibitor of influenza virus is orally active in mice

Recent characterization of broadly neutralizing antibodies (bnAbs) against influenza virus identified the conserved hemagglutinin (HA) stem as a target for development of universal vaccines and therapeutics. Although several stem bnAbs are being evaluated in clinical trials, antibodies are generally unsuited for oral delivery. Guided by structural knowledge of the interactions and mechanism of anti-stem bnAb CR6261, we selected and optimized small molecules that mimic the bnAb functionality. Our lead compound neutralizes influenza A group 1 viruses by inhibiting HA-mediated fusion in vitro, protects mice against lethal and sublethal influenza challenge after oral administration, and effectively neutralizes virus infection in reconstituted three-dimensional cell culture of fully differentiated human bronchial epithelial cells. Cocrystal structures with H1 and H5 HAs reveal that the lead compound recapitulates the bnAb hotspot interactions.

Asymmetric Synthesis of Rupestonic Acid and Pechueloic Acid

In this report, the originally proposed rupestonic acid (5) and pechueloic acid (3) were efficiently synthesized. The chiral lactone 13, recycled from the degradation of saponin glycosides, was utilized to prepare the key chiral fragment 11. During the exploration of this convergent assembly strategy, the ring-closing metathesis (RCM), SmI₂-prompted intermolecular addition, and [2,3]-Wittig rearrangement proved to be effective transformations for the synthesis of subunits.

Synthesis of Enantiopure Mixed Alkyl-Aryl Vicinal Diamines by the Diaza-Cope Rearrangement: A Synthesis of (+)-CP-99,994

The stereoselective synthesis of mixed alkyl-aryl vicinal diamines was demonstrated by the use of 1,2-bis(2-hydroxyphenyl)-1,2-diaminoethene (hpen). A sequential addition of aryl and alkyl aldehyde to hpen gave a fused imidazolidine-dihydro-1,3-oxazine ring stereoselectively, which undergoes the diaza-Cope rearrangement to provide mixed vicinal diimines at elevated temperature in good yields and excellent stereoselectivity. We also showed that (+)-CP-99,994 can be readily prepared by the diaza-Cope rearrangement in overall 42% yield.

Inhibition of influenza A virus matrix and nonstructural gene expression using RNA interference

Influenza antiviral drugs that use protein inhibitors can lose their efficacy as resistant strains emerge. As an alternative strategy, we investigated the use of small interfering RNA molecules (siRNAs) by characterizing three siRNAs (M747, M776 and M832) targeting the influenza matrix 2 gene and three (NS570, NS595 and NS615) targeting the nonstructural protein 1 and 2 genes. We also re-examined two previously reported siRNAs, M331 and M950, which target the matrix 1 and 2 genes. Treatment with M331-, M776-, M832-, and M950-siRNAs attenuated influenza titer. M776-siRNA treated cells had 29.8% less infectious virus than cells treated with the previously characterized siRNA, M950. NS570-, NS595- and NS615-siRNAs reduced nonstructural protein 1 and 2 expression and enhanced type I interferon expression by 50%. Combination siRNA treatment attenuated 20.9% more infectious virus than single siRNA treatment. Our results suggest a potential use for these siRNAs as an effective anti-influenza virus therapy.

Design and synthesis of 1,2,3-triazole-containing N-acyl zanamivir analogs as potent neuraminidase inhibitors

The design of potent metabolically stable neuraminidase (NA) inhibitors represents an attractive approach for treating influenza virus infection. In this study, we describe the exploitation of the 150-cavity in the active site of group 1 NA for the design, synthesis, and in vitro evaluation of new triazole-containing N-acyl derivatives related to Zanamivir. Inhibition studies with influenza virus NAs of group 1 (H1N1) and group 2 (H3N2) revealed that several of them are good inhibitors, with IC50 values in the low nanomolar (2.3 nM-31 nM) range. Substituents that form stable van der Waals interaction with the 150-cavity residues play crucial roles in NA inhibition as demonstrated by the potency of 6a (H1N1 IC50 = 2.3 nM, and H3N2 IC50 = 2.9 nM). Docking studies indicated that the cyclohexane-substituted triazole ring extended toward the hydrophobic region in the active site of group 1 NA in open form. The high potency observed for inhibitor 6a may be attributable to the highly favorable hydrophobic interactions in this region.

Antiviral activity of SA-2 against influenza A virus in vitro/vivo and its inhibition of RNA polymerase

A target-free and cell-based approach was applied to evaluate the anti-influenza properties of six newly synthesized benzoic acid derivatives. SA-2, the ethyl 4-(2-hydroxymethyl-5-oxopyrrolidin-1-yl)-3-[3-(3-methylbenzoyl)-thioureido] benzoate (compound 2) was screened as a potential drug candidate. In a cytopathic effect assay, SA-2 dose dependently inhibited H1N1, H3N2 and the oseltamivir-resistant mutant H1N1-H275Y influenza viruses in both virus-infected MDCK and A549 cells, with 50% effective concentrations (EC50) in MDCK cells of 9.6, 19.2 and 19.8 μM respectively, and 50% cytotoxic concentration (CC50) of 444.5 μM, showing competitive antiviral activity with oseltamivir in vitro. Orally administered SA-2 effectively protected mice infected with lethal doses of H1N1 or oseltamivir-resistant strain H1N1-H275Y, conferring 70% or 50% survival at a dosage of 100 mg/kg/d, reducing body weight loss, alleviating the influenza-induced acute lung injury, and reducing lung virus titer. Mechanistic studies showed that SA-2 efficiently inhibited the activity of RNA polymerase and suppressed NP and M1 levels during viral biosynthesis by interfering with gene transcription without having an obvious influence on virus entry and release. Based on these favourable findings, SA-2, a novel anti-influenza agent, with its potent anti-influenza activity in vitro and in vivo, could be a promising antiviral for the treatment of infection of influenza A viruses, including oseltamivir-resistant mutants.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

Influenza is an acute respiratory illness caused by influenza A and B viruses. Complications may occur, especially among children and the elderly.

OBJECTIVES

To assess the effectiveness and safety of amantadine and rimantadine in preventing, treating and shortening the duration of influenza A in children and the elderly.

SEARCH METHODS

We searched CENTRAL (2014, Issue 9), MEDLINE (1966 to September week 4, 2014) and EMBASE (1980 to October 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing amantadine and/or rimantadine with no intervention, placebo, other antivirals or different doses or schedules of amantadine or rimantadine in children and the elderly with influenza A.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results. We extracted and analysed data using the standard Cochrane methodology.

MAIN RESULTS

We identified 12 studies (2494 participants: 1586 children and 908 elderly) comparing amantadine and rimantadine with placebo, paracetamol (one trial: 69 children) or zanamivir (two trials: 545 elderly) to treat influenza A.Amantadine was effective in preventing influenza A in children (773 participants, risk ratio (RR) 0.11; 95% confidence interval (CI) 0.04 to 0.30). The assumed risk of influenza A in the control group was 10 per 100. The corresponding risk in the rimantadine group was one per 100 (95% CI 0 to 3). Nevertheless, the quality of the evidence was low and the safety of the drug was not well established.For treatment, rimantadine was beneficial in abating fever on day three of treatment in children: one selected study with low risk of bias, moderate evidence quality and 69 participants (RR 0.36; 95% CI 0.14 to 0.91). The assumed risk was 38 per 100. The corresponding risk in the rimantadine group was 14 per 100 (95% CI 5 to 34).Rimantadine did not show any prophylactic effect in the elderly. The quality of evidence was very low: 103 participants (RR 0.45; 95% CI 0.14 to 1.41). The assumed risk was 17 per 100. The corresponding risk in the rimantadine group was 7 per 100 (95% CI 2 to 23).There was no evidence of adverse effects caused by treatment with amantadine or rimantadine.We found no studies assessing amantadine in the elderly.

AUTHORS' CONCLUSIONS

The quality of the evidence combined with a lack of knowledge about the safety of amantadine and the limited benefits of rimantadine, do not indicate that amantadine and rimantadine compared to control (placebo or paracetamol) could be useful in preventing, treating and shortening the duration of influenza A in children and the elderly.

A review of the surveillance systems of influenza in selected countries in the tropical region

Influenza viruses cause annual epidemics of respiratory tract disease that affect all age groups. Many developing countries do not have an influenza surveillance system or adequate laboratory capacity for virus detection. The objective of this study was to describe the influenza surveillance systems in the different countries in the tropics and to identify outstanding research needs. A questionnaire was designed and sent to 52 NICs and MoHs in the different countries in tropical Asia and Africa to gather information on the surveillance systems, sentinel sites, specimen and data collection, and laboratory testing. Replies were received from 32 NICs and MoHs (61.5% response)--17 were located in tropical Asia and 15 in Africa. There are 20 WHO recognized NICs in tropical Asia and 14 in tropical Africa, all with virus isolation and polymerase chain reaction (PCR) testing capacity. Of the Asian countries, only Hong Kong and Singapore reported that the patient population from the sites represents the broader community. In tropical Africa, only Senegal has sentinel sites distributed all over the country contributing to the geographic representativeness of the surveillance system. The rest of the countries in Africa have just established their influenza surveillance system in the past decade and are working toward geographic expansion of the ILI and SARI sites. Limited laboratory capacity or infrastructure to perform influenza surveillance makes difficult to justify the importance of influenza vaccine or other influenza control measures as a strategy for improving population health in the tropical region.

Stereospecific synthetic approach towards Tamiflu using the Ramberg–Backlund reaction from cysteine hydrochloride

The stereospecific formal synthesis of Tamiflu from l-cysteine hydrochloride as the chiral source is described. The notable feature of the present strategy is the Ramberg–Backlund reaction and Sharpless–Reich protocol as the key chemical transformations to access the cyclohexene skeleton of Tamiflu.

Influenza A☆

The influenza viruses, which contain single-stranded RNA, are classified into three types, A, B, and C and belong to the Orthomyxoviridae family of viruses. Types A and B cause annual epidemics and often pandemics of influenza illness, while type C is a less common disease with fewer symptoms.

Emergence of a novel drug resistant H7N9 influenza virus: evidence based clinical potential of a natural IFN-α for infection control and treatment

The novel avian H7N9 influenza virus has caused more than 130 human infections with 43 deaths (as of September, 2013) in China. Because of the lack of existing immunity against H7 subtype influenza viruses in the human population and the absence of a licensed commercial vaccine, antiviral drugs are critical tools for the treatment of infection with this novel H7N9. Both M2-ion channel blockers and neuraminidase inhibitors are used as antiviral drugs for influenza infections of humans. The emerging H7N9 viruses are resistant to the M2-ion channel blockers because of a S31N mutation in the M2 protein; additionally, some H7N9 isolates have gained neuraminidase R292K substitution resulting in broad resistance to neuraminidase inhibitors. In this study we report that Alferon N can inhibit wild type and 292K H7N9 viruses replication in vitro. Since Alferon N is approved for clinical use, this would allow a rapid regulatory approval process for this drug under pandemic threat.

Synthesis of oseltamivir and tamiphosphor from N-acetyl-D-glucosamine

Using N-acetyl-D-glucosamine as a starting material, the anti-influenza drugs oseltamivir and tamiphosphor were synthesized via a pivotal intermediate of aldehyde 8. An intramolecular Horner-Wadsworth-Emmons reaction was utilized to construct the highly functionalized cyclohexene ring. The existing N-acetyl group was transformed into an azido group for the subsequent aziridination, followed by implantation of a 3-pentoxy group of the desired stereochemistry.

Occurrence and characterization of oseltamivir-resistant influenza virus in children between 2007-2008 and 2008-2009 seasons

PURPOSE

There was a global increase in the prevalence of oseltamivir-resistant influenza viruses during the 2007-2008 influenza season. This study was conducted to investigate the occurrence and characteristics of oseltamivir-resistant influenza viruses during the 2007-2008 and 2008-2009 influenza seasons among patients who were treated with oseltamivir (group A) and those that did not receive oseltamivir (group B).

METHODS

A prospective study was conducted on 321 pediatric patients who were hospitalized because of influenza during the 2007-2008 and 2008-2009 influenza seasons. Drug resistance tests were conducted on influenza viruses isolated from 91 patients.

RESULTS

There was no significant difference between the clinical characteristics of groups A and B during both seasons. Influenza A/H1N1, isolated from both groups A and B during the 2007-2008 and 2008-2009 periods, was not resistant to zanamivir. However, phenotypic analysis of the virus revealed a high oseltamivir IC50 range and that H275Y substitution of the neuraminidase (NA) gene and partial variation of the hemagglutinin (HA) gene did not affect its antigenicity to the HA vaccine even though group A had a shorter hospitalization duration and fewer lower respiratory tract complications than group B. In addition, there was no significant difference in the clinical manifestations between oseltamivir-susceptible and oseltamivir-resistant strains of influenza A/H1N1.

CONCLUSION

Establishment of guidelines to efficiently treat influenza with oseltamivir, a commonly used drug for treating influenza in Korean pediatric patients, and a treatment strategy with a new therapeutic agent is required.

Photodegradation and inhibition of drug-resistant influenza virus neuraminidase using anthraquinone-sialic acid hybrids

The anthraquinone-sialic acid hybrids designed effectively degraded not only non-drug-resistant neuraminidase but also drug-resistant neuraminidase, which is an important target of anti-influenza therapy. Degradation was achieved using long-wavelength UV radiation in the absence of any additives and under neutral conditions. Moreover, the hybrids efficiently inhibited neuraminidase activities upon photo-irradiation.

Development of oseltamivir phosphonate congeners as anti-influenza agents

Oseltamivir phosphonic acid (tamiphosphor, 3a), its monoethyl ester (3c), guanidino-tamiphosphor (4a), and its monoethyl ester (4c) are potent inhibitors of influenza neuraminidases. They inhibit the replication of influenza viruses, including the oseltamivir-resistant H275Y strain, at low nanomolar to picomolar levels, and significantly protect mice from infection with lethal doses of influenza viruses when orally administered with 1 mg/kg or higher doses. These compounds are stable in simulated gastric fluid, liver microsomes, and human blood and are largely free from binding to plasma proteins. Pharmacokinetic properties of these inhibitors are thoroughly studied in dogs, rats, and mice. The absolute oral bioavailability of these compounds was lower than 12%. No conversion of monoester 4c to phosphonic acid 4a was observed in rats after intravenous administration, but partial conversion of 4c was observed with oral administration. Advanced formulation may be investigated to develop these new anti-influenza agents for better therapeutic use.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

The effectiveness and safety of amantadine (AMT) and rimantadine (RMT) for preventing and treating influenza A in adults has been systematically reviewed. However, little is known about these treatments in children and the elderly.

OBJECTIVES

To systematically review the effectiveness and safety of AMT and RMT in preventing and treating influenza A in children and the elderly.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2) which contains the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register, MEDLINE (1966 to June week 3, 2011) and EMBASE (1980 to June 2011).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing AMT and/or RMT with placebo, control, other antivirals or different doses or schedules of AMT or RMT, or both, or no intervention, in children and the elderly.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and assessed methodological quality. We resolved disagreements by consensus. In all comparisons except for one, we separately analysed the trials in children and the elderly using Review Manager software.

MAIN RESULTS

A total of 12 studies involving 2494 participants (1586 children and adolescents and 908 elderly) compared AMT and RMT with placebo, paracetamol (one trial; 69 children) or zanamivir (two trials; 545 seniors). All studies were RCTs but most were still susceptible to bias. Two trials in the elderly had a high risk of bias because of incomplete outcome data. In one of those trials there was also a lack of outcome assessment blinding. Risk of bias was unclear in 10 studies due to unclear random sequence generation and allocation concealment. Only two trials in children were considered to have a low risk of bias.AMT was effective in preventing influenza A in children. A total of 773 participants were included in this outcome (risk ratio (RR) 0.11; 95% confidence interval (CI) 0.04 to 0.30). The assumed risk of influenza in the control group was 10 per 100 and the corresponding risk in the RMT group was one per 100 (95% CI 0 to 3). The quality of the evidence was considered low. For treatment purposes, RMT was beneficial for abating fever on day three of treatment. For this purpose one study was selected with low risk of bias and included 69 children (RR 0.36; 95% CI 0.14 to 0.91). The assumed risk was 38 per 100 and the corresponding risk in the RMT group was 14 per 100, 95% CI 5 to 34. The quality of the evidence was moderate.RMT did not show a prophylactic effect against influenza in the elderly, but the quality of evidence was considered very low. There were 103 participants (RR 0.45; 95% CI 0.14 to 1.41, for an assumed risk of 17 per 100 and a corresponding risk in the RMT group of 7 per 100, 95% CI 2 to 23). We did not identify any AMT trials in the elderly that met our inclusion criteria.There was no evidence of adverse effects of AMT and RMT in children or an adverse effect of RMT in the elderly. We did not identify any AMT trials in the elderly that met our inclusion criteria.

AUTHORS' CONCLUSIONS

AMT is effective in preventing influenza A in children but the NNTB is high (NNTB: 12 (95% CI 9 to 17). RMT probably helps the abatement of fever on day three of treatment, but the quality of the evidence is poor. Due to the small number of available studies, we could not reach a definitive conclusion on the safety of AMT or the effectiveness of RMT in preventing influenza in children and the elderly.

Oseltamivir in seasonal, pandemic, and avian influenza: a comprehensive review of 10-years clinical experience

Oseltamivir (Tamiflu®; F. Hoffmann-La Roche Ltd, Basel, Switzerland) is an orally administered antiviral for the treatment and prevention of influenza A and B infections that is registered in more than 100 countries worldwide. More than 83 million patients have been exposed to the product since its introduction. Oseltamivir is recommended by the World Health Organization (WHO) for use in the clinical management of pandemic and seasonal influenza of varying severity, and as the primary antiviral agent for treatment of avian H5N1 influenza infection in humans. This article is a nonsystematic review of the experience gained from the first 10 years of using oseltamivir for influenza infections since its launch in early 2000, emphasizing recent advances in our understanding of the product and its clinical utility in five main areas. The article reviews the pharmacokinetics of oseltamivir and its active metabolite, oseltamivir carboxylate, including information on special populations such as children and elderly adults, and the co-administration of oseltamivir with other agents. This is followed by a summary of data on the effectiveness of oseltamivir treatment and prophylaxis in patients with all types of influenza, including pandemic (H1N1) 2009 and avian H5N1 influenza. The implications of changes in susceptibility of circulating influenza viruses to oseltamivir and other antiviral agents are also described, as is the emergence of antiviral resistance during and after the 2009 pandemic. The fourth main section deals with the safety profile of oseltamivir in standard and special patient populations, and reviews spontaneously reported adverse event data from the pandemic and pre-pandemic periods and the topical issue of neuropsychiatric adverse events. Finally, the article considers the pharmacoeconomics of oseltamivir in comparison with vaccination and usual care regimens, and as a component of pandemic influenza mitigation strategies.

A practical synthesis of zanamivir phosphonate congeners with potent anti-influenza activity

Two phosphonate compounds 1a (4-amino-1-phosphono-DANA) and 1b (phosphono-zanamivir) are synthesized and shown more potent than zanamivir against the neuraminidases of avian and human influenza viruses, including the oseltamivir-resistant strains. For the first time, the practical synthesis of these phosphonate compounds is realized by conversion of sialic acid to peracetylated phosphono-DANA diethyl ester (5) as a key intermediate in three steps by a novel approach. In comparison with zanamivir, the high affinity of 1a and 1b can be partly attributable to the strong electrostatic interactions of their phosphonate groups with the three arginine residues (Arg118, Arg292, and Arg371) in the active site of neuraminidases. These phosphonates are nontoxic to the human 293T cells; they protect cells from influenza virus infection with EC(50) values in low-nanomolar range, including the wild-type WSN (H1N1), the 2009 pandemic (H1N1), the oseltamivir-resistant H274Y (H1N1), RG14 (H5N1), and Udorn (H3N2) influenza strains.

[Influenza : clinical symptoms, diagnostics and therapy]

Influenza infections have important socio-economic consequences. Risk groups identified so far include small children and elderly adults with comorbidities. In recent years in addition to seasonal influenza an outbreak of avian influenza occurred in 2005 and the new H1N1 pandemic occurred in 2009. For the latter other at risk groups were affected and a different clinical course has been documented. The focus of this article is to give an overview on the epidemiology, clinical characteristics, diagnosis and therapy of influenza infections.

Seasoned adaptive antibody immunity for highly pathogenic pandemic influenza in humans

Fundamentally new approaches are required for the development of vaccines to pre-empt and protect against emerging and pandemic influenzas. Current strategies involve post-emergent homotypic vaccines that are modelled upon select circulating 'seasonal' influenzas, but cannot induce cross-strain protection against newly evolved or zoonotically introduced highly pathogenic influenza (HPI). Avian H5N1 and the less-lethal 2009 H1N1 and their reassortants loom as candidates to seed a future HPI pandemic. Therefore, more universal 'seasoned' vaccine approaches are urgently needed for heterotypic protection ahead of time. Pivotal to this is the need to understand mechanisms that can deliver broad strain protection. Heterotypic and heterosubtypic humoral immunities have largely been overlooked for influenza cross-protection, with most 'seasoned' vaccine efforts for humans focussed on heterotypic cellular immunity. However, 5 years ago we began to identify direct and indirect indicators of humoral-herd immunity to protein sites preserved among H1N1, H3N2 and H5N1 influenzas. Since then the evidence for cross-protective antibodies in humans has been accumulating. Now proposed is a rationale to stimulate and enhance pre-existing heterotypic humoral responses that, together with cell-mediated initiatives, will deliver pre-emptive and universal human protection against emerging epidemic and pandemic influenzas.