A new drug being developed to fight both bird flu and seasonal flu can be given safely to people in very high doses, BioCryst Pharmaceuticals Inc. said on Friday.

The drug, called peramivir, is still in experimental trials but is considered the next-line drug to fight influenza of all sorts, after Tamiflu and Relenza.

Experts want to have several antivirals to choose from in fighting flu because the virus mutates quickly, and because no drug has been completely effective.

“We demonstrated that you can go to very high levels of peramivir in humans,” Dr. Charles Bugg, Chairman and Chief Executive Officer of BioCryst, said in a telephone interview.

“We did escalating doses — starting at a low dose and showing it’s safe and going until we have a dose way, way above what we think it takes to inhibit the virus. We can go to very high levels,” Bugg added.

They gave more than 60 healthy volunteers intravenous peramivir each day for up to 10 days in doses ranging from about 30 mg to 600 mg.

All doses were well tolerated with no serious adverse effects, researchers independent of the company told a meeting in San Francisco of the American Society for Microbiology.

The U.S. Food and Drug Administration gave peramivir “fast-track status” in January to allow speedy review for approval. The company has said peramivir has shown broad spectrum activity against various strains of flu, including the H5N1 virus that causes bird flu, in animal trials.

The oldest influenza drugs, amantadine and rimantadine, are no longer recommended for use against seasonal flu because the viruses largely resist them.

RESISTANCE TO TAMIFLU

Roche and Gilead Sciences Inc.’s Tamiflu, also known as oseltamivir, also works against both seasonal flu and H5N1 avian influenza. Tamiflu is now routinely given to bird flu victims, but some strains of bird flu have already begun to evolve resistance to Tamiflu.

H5N1 mainly affects birds but experts fear it could mutate into a strain capable of killing millions of people in a global pandemic. It has killed 148 people out of 251 infected in 10 countries since 2003.

Relenza, made by GlaxoSmithkline under license from Australia’s Biota is an inhaled drug that also appears to treat both types of flu.

“There is really nothing now behind Tamiflu and Relenza as potential agents that could be made available,” Bugg said.

He said mutation of the viruses is the reason for testing very high doses of drugs. “You hit them with a drug and they eventually will figure out how to get around the drug. The way you get around this is to go in with huge amounts,” Bugg said.

Bugg said peramivir is easier to make than Tamiflu, which requires rare ingredients.

“We can manufacture large amounts of peramivir,” he said.

He said one Swiss manufacturer can make one metric ton of peramivir a month, and the company had identified a U.S. facility that can be up and running in seven months.

He estimates that one ton of peramivir would treat 8 million flu patients.

“It is not enough to treat everybody but we have got enough to treat millions and millions per month,” Bugg said.

Peramivir can be given either as an infusion or as an injection.

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