Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Japanese Flu Drug Shows Promising Results in Patient Trials

Dear Doctor: Apparently Japan just approved a new drug that can get rid of the flu virus in one day. When can we get this drug in the United States? And if we can't, can we order it online?

Dear Reader: The prospect of a one-dose drug that kills the influenza virus in 24 hours would be remarkable. As the most severe influenza outbreak in the U.S. in over a decade draws to a close, the news is riveting.

The drug, known as baloxavir marboxil, will be sold under the name Xofluza. In patient trials conducted in Japan, it killed influenza viruses in one day in most patients. That's significantly faster than Tamiflu, which until now has been the most effective influenza drug. With 3 to 5 million people worldwide affected each year by influenza epidemics that result in between 250,000 and 500,000 deaths, it's no surprise that Japanese officials put Xofluza on the fast track for approval.

According to the drug manufacturer, the new therapy is effective against influenza A and B viruses, and also showed promise against the H5N1 and H7N9 strains. Because viral shedding was shown to be controlled within two days, researchers are optimistic that the drug will also play a role in reducing transmission of the flu.

Viruses are basically microscopic (and sub-microscopic) protein-covered packets of genetic material whose core function is to copy themselves. They can only do this within the living cells of a host. Whether it's a bacterium, fungus, plant or animal, the virus gains control of the host cell's replication process and forces it to churn out copies of the viral genome.

The reason this new Japanese antiviral works so quickly is that it interferes with the ability of the influenza virus to copy itself. Specifically, the drug blocks an enzyme the virus needs to crack open and hijack the host cell's replication mechanisms. By killing the influenza virus within 24 hours, it is now the fastest-acting flu drug available.

Flu sufferers who take the new drug will still experience their fair share of flu symptoms. But results from patient studies suggest they will be milder and of shorter duration. Those who received the drug in patient trials had 24 hours of fever, while fever in those who received a placebo lasted nearly twice as long. Patients taking Xofluza returned to pre-influenza health status a full 40 hours faster than did those who received the placebo. And unlike Tamiflu, which is a five-day regimen of two pills per day, Xofluza is a single-dose, one pill regimen.

According to news reports, Xofluza is expected to be available in Japan sometime this spring, when the national insurer sets a price. The company plans to file for approval in the U.S., but Xofluza is not expected to be available until 2019.

As for whether you can buy the drug online before it becomes available here, the short answer is no. According to the Food and Drug Administration, it is illegal to buy drugs from other countries that have not been approved by the FDA for use and sale in the U.S.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)