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| Clinical data | |
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| Trade names | Relenza |
| Other names | 5-acetamido- 4-guanidino- 6-(1,2,3-trihydroxypropyl)- 5,6-dihydro- 4H-pyran- 2-carboxylic acid |
| AHFS/Drugs.com | Monograph |
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| Routes of administration | Inhalation |
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| Pharmacokinetic data | |
| Bioavailability | 2% (oral) |
| Protein binding | <10% |
| Metabolism | Negligible |
| Elimination half-life | 2.5–5.1 hours |
| Excretion | Renal |
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| CompTox Dashboard (EPA) | |
| ECHA InfoCard | 100.218.632  |
| Chemical and physical data | |
| Formula | C12H20N4O7 |
| Molar mass | 332.31 g/mol g·mol |
| 3D model (JSmol) | |
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| Influenza (flu) |
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| Types |
| Vaccines |
| Treatment |
| Pandemics |
| Outbreaks |
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Zanamivir INN (/zəˈnæmvɪər/) is a neuraminidase inhibitor used in the treatment and prophylaxis of influenza caused by influenza A virus and influenza B virus. Zanamivir was the first neuraminidase inhibitor commercially developed. It is currently marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation.
According to the Centers for Disease Control and Prevention (CDC), no flu, seasonal or pandemic, has shown any signs of resistance to zanamivir.
History
Zanamivir was discovered in 1989 by scientists led by Mark von Itzstein at the Victorian College of Pharmacy, Monash University, in collaboration with the CSIRO and scientists at Glaxo, UK. Zanamivir was the first of the neuraminidase inhibitors. The discovery was initially funded by the Australian biotechnology company Biota and was part of Biota's ongoing program to develop antiviral agents through rational drug design. Its strategy relied on the availability of the structure of influenza neuraminidase, by X-ray crystallography. It was also known, as far back as 1974, that 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (DANA), a sialic acid analogue, was an inhibitor of neuraminidase. Sialic acid (N-acetyl neuraminic acid, NANA), the substrate of neuraminidase, is itself a mild inhibitor of the enzyme, but the dehydrated derivative DANA, a transition-state analogue, is a better inhibitor.
Computational chemistry techniques were used to probe the active site of the enzyme, in an attempt to design derivatives of DANA that would bind tightly to the amino acid residues of the catalytic site, and so would be potent and specific inhibitors of the enzyme. The GRID software by Molecular Discovery was used to determine energetically favourable interactions between various functional groups and residues in the catalytic site canyon. This showed there was a negatively charged zone in the neuraminidase active site that aligned with the C4 hydroxyl group of DANA. This hydroxyl was therefore replaced with a positively charged amino group; the 4-amino DANA was 100 times better as an inhibitor than DANA, owing to the formation of a salt bridge with a conserved glutamic acid (119) in the active site. It was also noticed that Glu 119 was at the bottom of a conserved pocket in the active site just big enough to accommodate a more basic functional positively charged group, such as a guanidino group, which was also larger than the amino group. Zanamivir, a transition-state analogue inhibitor of neuraminidase, was the result.
As Biota was a small company, it did not have the resources to bring zanamivir to market by itself. In 1990, zanamivir patent rights were licensed to Glaxo, now GlaxoSmithKline (GSK). In 1999, the product was approved for marketing in the US and subsequently has been registered by GSK in a total of 70 countries (GlaxoSmithKline News release, 2006). Zanamivir is delivered via Glaxo's proprietary Diskhaler inhalation device. The license agreement entitled Biota to receive a 7% royalty on Glaxo's sales of zanamivir.
Developments
Recently, the reported oseltamivir-resistance H5N1 virus neuraminidase still retaining susceptibility to zanamivir indicates that the structure of zanamivir has some advantages over oseltamivir in binding to the active pocket of H5N1 neuraminidase.
In January 2011, GlaxoSmithKline started a pivotal study testing intravenous zanamivir against oral oseltamivir (the Tamiflu pill) as a treatment for patients hospitalised with influenza. GSK's press release
As a proven anti-influenza drug target, neuraminidase continues to be attractive for the development of new inhibitors. The crystal structure of H5N1 avian influenza neuraminidase (PDB code: 2HTY) provides the three-dimensional structural information and opportunity for finding new inhibitors in this regard, because the existing inhibitors, such as oseltamivir and zanamivir, were developed based on different structures of neuraminidase, such as subtypes N9, N2, and type B genus of influenza virus.
Pharmacology
Zanamivir is specifically for the treatment of infections caused by Influenzavirus A and Influenzavirus B.
Influenza, commonly known as the flu, is caused by a virus which targets the body's respiratory cells and damages the lining of the respiratory tract, leading to swelling and inflammation of the tract. Influenza spreads rapidly by replicating itself inside the host cell, producing hundreds of copies of the virus in a short period. In approximately an hour the virus can destroy the host cell and propel its replications out into the body to find new host cells. For some people, the flu and its complications can be very serious, even fatal.
Zanamivir works by binding to the active site of the neuraminidase protein, rendering the influenza virus unable to escape its host cell and infect others. It is also an inhibitor of influenza virus replication in vitro and in vivo. In clinical trials it was found that zanamivir was able to reduce the time to symptom resolution by 1.5 days if therapy was started within 48 hours of the onset of symptoms.
Dosing and side effects
The bioavailability of zanamivir is 2%. After inhalation, zanamivir is concentrated in the lungs and oropharynx, where up to 15% of the dose is absorbed and excreted in urine.
Dosing is limited to the inhaled route. This restricts its usage, as treating asthmatics could induce bronchospasms. The U.S. Food and Drug Administration (FDA) has issued a Public Health Advisory warning that it has received some reports of respiratory problems following inhalation of zanamivir by patients with underlying asthma or chronic obstructive pulmonary disease. The zanamivir package insert contains precautionary information regarding risk of bronchospasm in patients with respiratory disease.
Zanamivir has not been known to cause toxic effects, does not spread around through the body's systemic circulation and shows no signs of viral resistance from any flu.
GlaxoSmithKline (GSK) and FDA notified healthcare professionals of a report of the death of a patient with influenza who received Relenza (zanamivir) Inhalation Powder which was solubilized and administered by mechanical ventilation.
Commercial issues
Although zanamivir was the first neuraminidase inhibitor to the market, it had only a few months lead over the second entrant, oseltamivir (Tamiflu), with an oral tablet formulation.
According to the CDC, Tamiflu, zanamivir’s main competitor, is not as effective at treating the Influenza viruses as zanamivir, especially in H1N1 Seasonal Flu. In fact, tests showed that 99.6% of the tested strains of seasonal H1N1 flu and 0.5% of 2009 pandemic flu were resistant to Tamiflu while there have been absolutely zero flu samples seasonal or pandemic that show any resistance to zanamivir.
When first marketed in the US in 1999/2000, zanamivir captured only 25% of the influenza antiviral market, despite a huge promotional campaign. By the end of that season, Tamiflu was outselling zanamivir 3:1. During that season, zanamivir experienced worldwide safety warnings involving the risk of bronchospasm and death. Glaxo then reduced the marketing of zanamivir, and Tamiflu's dominance increased. More than US$20m worth of zanamivir sold by Glaxo in the first US season was returned to the company in the next two seasons because zanamivir's sales to patients were far less than expected.
Biota commenced legal proceedings in 2004 alleging that Glaxo's reduced marketing of zanamivir was a breach of contract. Biota claimed approximately A$700m from Glaxo. After Biota spent four years trying to progress its case, and incurring A$50m in legal costs, the company abandoned the claim in July 2008, recovering only A$20m including legal costs following settlement at mediation. Biota had refused an earlier tactical offer from Glaxo of A$75m plus legal costs.
In August 2006, Germany announced that it would buy 1.7 million doses of zanamivir, as part of its preparation strategy against bird flu. "Germany's purchase shows that countries are starting to take a balanced view of influenza preparedness," says Simon Tucker, head of research at Melbourne-based Biota, where zanamivir was originally developed.
In April 2009 many cases of swine flu (H1N1 type virus) were reported in US and Mexico. Zanamivir is one of only two drugs that are prescribed to treat it. A study published in June 2009 emphasized the urgent need for augmentation of oseltamivir (Tamiflu) stockpiles, with additional antiviral drugs including zanamivir, based on an evaluation of the performance of these drugs in the scenario that the 2009 H1N1 swine flu neuraminidase (NA) were to acquire the Tamiflu-resistance (His274Tyr) mutation which is currently widespread in 99.6% of all tested seasonal H1N1 strains.
In January 2011, GSK announced it was commencing Phase III trials for Intravenous zanamivir in a study which will span 20 countries in the Northern and Southern hemispheres.
Legal status
The drug is approved for use for the prevention and treatment of influenza in those over the age of 7 in the United States, Canada, European Union and many other countries. It is not recommended for people with respiratory problems and ailments.
Chemistry
After Scheigetz et al.
References
- ^ "2008-2009 Influenza Season Week 32 ending August 15, 2009". Flu Activity & Surveillance. Centers for Disease Control and Prevention (CDC). August 21, 2009.
- Meindl P, Bodo G, Palese P, Schulman J, Tuppy H (1974). "Inhibition of neuraminidase activity by derivatives of 2-deoxy-2,3-dehydro-N-acetylneuraminic acid". Virology. 58 (2): 457–63. doi:10.1016/0042-6822(74)90080-4. PMID 4362431.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) -
Laver, Graeme (2007). "Flu drugs - pathway to discovery". Education in Chemistry. Retrieved 2009-11-11.
{{cite journal}}: Unknown parameter|month=ignored (help) ISSN 0013-1350 - von Itzstein M, Wu WY, Kok GB; et al. (1993). "Rational design of potent sialidase-based inhibitors of influenza virus replication". Nature. 363 (6428): 418–23. doi:10.1038/363418a0. PMID 8502295.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^
Collins PJ, Haire LF, Lin YP, Liu J, Russell RJ, Walker PA, Skehel JJ, Martin SR, Hay AJ, Gamblin SJ. (2008). "Crystal structures of oseltamivir-resistant influenza virus neuraminidase mutants". Nature. 453 (7199): 1258–61. doi:10.1038/nature06956. PMID 18480754.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^
Garcia-Sosa AT, Sild S, Maran U. (2008). "Design of Multi-Binding-Site Inhibitors, Ligand Efficiency, and Consensus Screening of Avian Influenza H5N1 Wild-Type Neuraminidase and of the Oseltamivir-Resistant H274Y Variant". J. Chem. Inf. Model. 48 (10): 2074–2080. doi:10.1021/ci800242z. PMID 18847186.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - Du QS, Wang SQ, Chou KC (2007). "Analogue inhibitors by modifying oseltamivir based on the crystal neuraminidase structure for treating drug-resistant H5N1 virus". Biochemical and Biophysical Research Communications. 362 (2): 525–31. doi:10.1016/j.bbrc.2007.08.025. PMID 17707775.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Cyranoski D (2005). "Threat of pandemic brings flu drug back to life". Nature Medicine. 11 (9): 909. doi:10.1038/nm0905-909. PMID 16145557.
{{cite journal}}: Unknown parameter|month=ignored (help) - Moscona A (2005). "Neuraminidase inhibitors for influenza". The New England Journal of Medicine. 353 (13): 1363–73. doi:10.1056/NEJMra050740. PMID 16192481.
{{cite journal}}: Unknown parameter|month=ignored (help) - Hayden FG (2001). "Perspectives on antiviral use during pandemic influenza". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 356 (1416): 1877–84. doi:10.1098/rstb.2001.1007. PMC 1088564. PMID 11779387.
{{cite journal}}: Unknown parameter|month=ignored (help) - "Safe and Appropriate Use of Influenza Drugs". Public Health Advisories (Drugs). U.S. Food and Drug Administration (FDA). April 30, 2009. Retrieved 2009-11-11.
- www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm186081.htm
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Soundararajan V, Tharakaraman K, Raman R, Raguram S, Sasisekharan V, Sasisekharan R (2009). "Extrapolating from sequence--the 2009 H1N1 'swine' influenza virus". Nature Biotechnology. 27 (6): 510–3. doi:10.1038/nbt0609-510. PMID 19513050.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - Hirschler, Ben (2011-01-19). "GSK tests intravenous flu drug vs Roche's Tamiflu". Reuters.
- Scheigetz, J.; Zamboni, R.; Bernstein, M. A.;Roy, B. (December 1995). "A syntheses of 4-a-guanidino-2-deoxy-2,3-didehydro n-acetylneuraminic acid". Organic Letters. 27 (6): 637–644. doi:10.1021/ol901511x. Retrieved 2010-11-14.
{{cite journal}}: More than one of|work=and|journal=specified (help)CS1 maint: multiple names: authors list (link)
External links
- The development of Relenza for treatment of influenza
- Drug Information: Zanamivir Inhalation MedlinePlus drug
- Relenza: Consumer Questions and Answers US Food and Drug Administration (FDA)
- Relenza Biota Holdings
- Relenza web site GlaxoSmithKline
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