Two existing drugs used to treat osteoporosis may be effective in killing influenza viruses, including the new H1N1 swine flu and the H5N1 bird flu viruses, researchers in Hong Kong have found.

The two drugs are pamidronate and zoledronate, which are marketed by Novartis AG under the brand names Aredia and Reclast, respectively.

In their experiment, the researchers exposed human cells that had been infected with the influenza viruses to the two drugs.

They observed that the drugs triggered extra production of a type of white blood cell called yd-T cells, which went on to kill human cells that were infected with the flu viruses.

Flu viruses can only replicate in living human or animal cells and killing infected cells would stop the viruses from replicating, the researchers said.

Professor Lau Yu-lung at the University of Hong Kong's pediatrics and adolescent medicine department described the infected human cells as factories that will produce viruses.

These drugs attack the viruses specifically ... This approach kills the factories that are producing viruses.

Malik Peiris, also part of the research team, said the drugs could enhance immune responses of the human body.

That was especially important as flu viruses mutate constantly, which reduces the efficacy of vaccines, he added.

The researchers plan to move next into animal and then human clinical testing.

Medicine