Substance of the Year 2007

 

oseltamivir phosphate

 

 

 

Tamiflu is the proprietary name for oseltamivir phosphate – an oral antiviral treatment for influenza, designed to prevent flu viruses from replicating within the body (it is neither a vaccine nor a substitute for one). A neuraminidase inhibitor (NAI), Tamiflu targets neuraminidase – the enzyme found on the surface of flu viruses – and hinders the virus from travelling cell to cell to spread the infection.

 

The drug can be used both for the prevention and treatment of flu, though for full efficacy, Tamiflu should be taken within 48 hours of the onset of flu symptoms. The adult dose is one 75mg capsule taken orally twice a day for 5 days.

 

Tamiflu is one of two main drugs thought to be effective against avian flu H5N1 – the other drug, zanamivir, less conveniently, has to be inhaled. The drug company Roche acquired the rights to manufacture and distribute Tamiflu from Gilead Sciences in 1996, and the drug’s patent expires in 2016†.

 

As the threat of an H5N1 pandemic grew, demand for Tamiflu threatened to outstrip supply. Real and counterfeit supplies of the drug flooded the web (Tamiflu-related spam became rife), and in December 2005 eBay halted a British auction where a 10-capsule course had reached >£100.

 

Under political pressure from governments worldwide† (and market pressure to maximise profits), Roche took steps to increase production. One of the issues affecting Tamiflu’s supply is the complexity of its manufacture: the 10-step process takes 6–8 months, and currently starts with the extraction of shikimic acid from star anise pods grown in the Guanxi, Sichuan, Yunnan, and Guizhou mountain provinces of SW China.

 

In March 2006, Roche pledged to manufacture c.400m treatments annually by the end of the year, using 15 external contractors in 9 countries. According to Roche, they have fulfilled Tamiflu ‘pandemic orders’ from >65 countries, with some governments stockpiling treatments for 20–40% of their population. Roche has also donated 5·125m courses of Tamiflu to the WHO for rapid response in flu-hit areas.

 

While some reports have questioned the effectiveness of oseltamivir for bird flu, Tamiflu remains the drug of choice. As a result, Roche announced a 22% growth in sales during the first 3 months of 2006, to 7·7bn Swiss Francs ($6bn; £3·4bn).

 

[† New drug patents allow the creators a 20-year monopoly of supply. However, international law permits governments to break patents, and ‘compulsorily licence’ generic versions in the event of severe national health emergencies.]