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New Japanese flu drug protects mice from avian flu

January 2, 2010

An experimental influenza drug can protect mice against H5N1 avian influenza better than the preferred drug Tamiflu, researchers reported.

The drug, called T-705 or favipiravir, is made by Fujifilm Holdings Corp unit Toyama Chemical Co. It works differently from Tamiflu and Relenza and seems to work at lower doses, the researchers reported in the Proceedings of the National Academy

of Sciences.

Tamiflu, Roche AG and Gilead Sciences Inc’s popular pill and Relenza, GlaxoSmithKline’s and Biota Inc’s inhaled flu drug, must be given with 48 hours to be fully effective.

”This compound works much better, even three days after infection,” Yoshihiro Kawaoka of the University of Tokyo and the University of Wisconsin said in a statement.

”Our results suggest that T-705 is safe and effective in combating H5N1 influenza viruses and is, thus, a promising candidate antiviral for the treatment of highly pathogenic H5N1 patients,” Kawaoka and colleagues wrote.

Although it has not, like H1N1 swine flu, caused a pandemic, H5N1 avian influenza is still circulating. It has infected 447 people and killed 263 of them since 2003, and most experimental new flu drugs, such as T-705, were being tested against H5N1.

Flu experts still fear H5N1 could quickly change into a form that humans could easily pass from one to another and it is far more deadly than H1N1.

”H5N1 virus is so pathogenic even Tamiflu doesn’t protect all the infected animals,” Kawaoka said.

The virus also could combine with resistant strains of seasonal influenza virus to become both resistant to drugs and also more easily transmitted.

”Therefore, there is a need for unique and effective antivirals to combat H5N1 influenza viruses,” he said.


Experts also fear that H1N1 swine flu could become widely resistant to Tamiflu, as its seasonal strain has.

The government-funded study, available at http://www.pnas.org/cgi/doi/10.1073/pnas.0909603107, used mice infected with a highly pathogenic version of H5N1.

The drug also stopped the overreaction of the immune system that many researchers believe sometimes kills flu patients.

Kawaoka is sometimes paid to speak for drug companies, but this study was funded by the Japanese and US governments.

Other experimental flu drugs in the pipeline include peramivir, made by Biocryst Pharmaceuticals Inc and licensed to Shionogi & Co Ltd. It is licensed for emergency use in the United States for extremely ill patients who must be treated intravenously.

Daiichi Sankyo Co Ltd’s CS 8958 or laninamivir NexBio Inc.’s FluDase are also being tested.

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