Relenza (Zanamivir) Commercial Issues

Relenza is the brand name of the drug that contains zanamivir, which is useful in the treatment of influenza. Although the drug promised to be a great success when it was first released for use in 1999, the commercial sales of the drug were much less than expected.

This is thought to be largely as a result of a subsequent neuroaminidase inhibitor drug, Tamiflu, which was licensed for use shortly after Relenza. This medication received stronger marketing support hence acquired the vast majority of sales of anti-influenza medications.

Drug Discovery and Licensing

Relenza was discovered in 1989 by Biota and was licensed to GlaxoSmithKline (GSK) in 1990 to for development and marketing of the medication. It was the first broad-spectrum anti-influenza drug known as a neuraminidase inhibitor to be approved for use in the US in 1999 and has since been registered for use in seventy countries. It had a few months lead over a second drug in the same class, Tamiflu (oseltamivir) available in an oral formulation, which was licensed for use shortly after.

Product Launch and Marketing

Relenza was launched into the market with considerable promotion and marketing campaigns but, despite this, in the first year of sales it held only a quarter of the anti-viral medications sold for influenza, despite its lower price. Tamiflu was the more popular option and was outselling Relenza at a ratio of 3:1.

This trend is thought to be a result of the safety warnings associated with Relenza when it was launched. As it is an inhalation powder drug, it can cause serious adverse effects for some patients, such as those that suffer from asthma, including bronchospasm and death. This led to physicians lending a preference to Tamiflu, whose oral formulation did not carry these effects. In addition to this, Relenza was only licensed for children over the age of seven, whereas Tamiflu could be administered to children as young as three months.

Following the initial launch year, more than US$20 million worth of the drug was returned to the company, as sales were much less than had been anticipated. GSK responded by reducing the marketing of Relenza, which then led to subsequent years of falling sales and Tamiflu monopolizing the market.

This was a disappointment for many involved with the drug, however, particularly as the efficacy of Relenza is considered to be superior to that of Tamiflu. In fact, the vast majority of HIN1 season flu strains are resistant to Tamiflu, whereas do not show any resistance to Relenza.

In 2006, Germany announced its preparation strategy against bird flu, which included the purchases of 1.7 million doses of Relenza. However, the general preference for Tamiflu continued, with its US$770 million revenue for the year greatly overshadowing Relenza revenue of $13 million.

Legal Following

In 2004, Biota launched legal proceedings, under the alleged claim that GSK had breached the licensing contract by failing to promote and support the commercial growth of the drug. It claimed that Relenza had the potential to be the dominating brand on the market but its marketing had been abandoned after the initial launch, leading to its poor sales. After four years of endeavors to progress the case, it was eventually withdrawn in 2008.


Further Reading

Last Updated: Aug 23, 2018

Yolanda Smith

Written by

Yolanda Smith

Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.


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