F.D.A. Approves New Drug for Flu

The first new flu drug in 20 years won approval Wednesday from the Food and Drug Administration.

The new antiviral generically referred to as baloxavir marboxil but sold under the brand name Xofluza is a single dose treatment.

It is to be used only in those aged 12 or more, the F.D.A. said, and will be taken only within the first two days after symptoms like fever, aches, and sniffles appear.

The pill will cost $150, consistent with a spokeswoman for Genentech, which can sell Xofluza in this country.

Genentech will offer coupons that lower the worth $30 for patients with health insurance and to about $90 for the uninsured.

Flu season has already begun, and last years was one among the foremost lethal in decades; about 80,000 Americans died of flu or its consequences, the Centers for Disease Control and Prevention said earlier this month.

The new drug is not any miracle cure and it's not approved for young children, who are one of the most vulnerable groups, so the C.D.C. still strongly recommends that every American over the age of six months get a flu shot as soon as possible.

Several other anti-flu drugs exist — the best-known of which is oseltamivir, sold as Tamiflu — but none cure the illness quickly.

Also, the influenza virus mutates very rapidly and has split into many strains that circulate simultaneously each winter, and a number of other have evolved resistance to older drugs.

“Having safe and effective treatment alternatives is critical,” said Dr. Scott Gottlieb, the F.D.A. commissioner, in a statement. “This novel drug provides an important additional treatment option.”

Xofluza works during a new way, by blocking an enzyme the virus must copy itself.

So, at least in theory, circulating flu strains immune to earlier drugs shouldn't have any resistance to it.

It has been shown to work against both A and B strains, which circulate each year, and it is expected to figure against dangerous bird touches of flu known to sometimes infect humans, such as the A strains of both H5N1 and A H7N9.

However, it's virtually inevitable that resistance to Xofluza will evolve as more people use it.

(To prevent that, doctors treat several diseases, including H.I.V. and tuberculosis, with cocktails of three or four different drugs, but that's not the norm for flu treatment.)

Xofluza was invented by Shionogi, a Japanese company that also created the statin Crestor.

It doesn't cure a bout of flu as rapidly as, for instance, antibiotics clear susceptible bacterial infections.

But it's going to alleviate some symptoms and shorten the time that patients feel sick, said Dr. Debra Birnkrant, the F.D.A.’s director of antiviral products.

Xofluza was approved after two clinical trials in 1,832 patients. In both trials, those treated with it recovered more quickly than those that got a placebo.

In one trial, there was no difference between Xofluza and Tamiflu.

Tamiflu, which is sold by Roche, Genentech’s parent company, is now available cheaply as a generic drug. It requires two pills each day for five days.

Xofluza’s commonest side effects were diarrhea and bronchitis, the F.D.A. said.

Further research is underway to ascertain whether it's safe and effective in children and whether it lowers rates of hospitalization and death.

In June, the F.D.A. granted Shionogi and Genentech “priority review” status, expediting the approval process because it had been considered a crucial drug.