Japan has a new drug that could kill the flu in 24 hours. So why doesn't the U.S. have it?

This has been an especially deadly flu season here in the U.S., but a new breakthrough medication promises to kill the flu virus in 24 hours. The catch: It’s only available in Japan.

On Friday, officials in Japan approved the single-dose drug, known as Xofluza, for use in the country, according to the Wall Street Journal. In a clinical trial, Japanese and American patients who took the drug when they had the flu saw the virus wiped out, on average, in 24 hours.

Xofluza is manufactured by Japanese drug maker Shionogi and won’t hit shelves until at least May — again, in Japan. According to the Wall Street Journal, the drug won’t be available in the U.S. until at least 2019.

Currently, the only drug available in the U.S. to fight the flu is Tamiflu, which is taken twice daily over five consecutive days. Tamiflu doesn’t kill the flu virus — it just lowers the odds that patients will suffer serious complications, like pneumonia. It may also reduce the duration of the flu by a day, according to the Centers for Disease Control and Prevention.

Xofluza works differently — it inhibits an enzyme the flu virus needs to replicate. The drug can work in 24 hours because it inhibits a process known as “cap snatching,” which is a mechanism used by viruses to hijack the mRNA (a nucleic acid in living cells that acts as a messenger for DNA) transcription system to allow the creation of viral RNAs, Sherif Mossad, M.D., an infectious disease specialist at Cleveland Clinic, tells Yahoo Lifestyle. He calls Xofluza an “excellent addition” to current flu-fighting medications. “This could lead to easier treatment of flu,” he adds.

Infectious disease expert Amesh A. Adalja, M.D., senior scholar at the John’s Hopkins Center for Health Security, agrees. “The more antiviral options people have to treat the flu, the better,” he tells Yahoo Lifestyle.

Tamiflu has the highest impact when it’s taken within the first 48 hours after the onset of flu symptoms. Adalja says it’s likely that early intervention will be better with Xofluza too. “The earlier you take any kind of medication, the better in general it will work,” he says.

As with most drugs, there is potential for misuse. Mossad has concerns that the drug must be accompanied by a quick and accurate diagnosis to avoid misuse and development of resistance.

Regarding when we could see Xofluza in the U.S., Adalja says the medication will be subject to the standards of the Food and Drug Administration first. In a document on its website outlining the drug approval process, the FDA notes that drugs must pass animal testing for toxicity before drugmakers can apply for FDA approval. From there, they must undergo three phases of human trials to determine safety, effectiveness, dosage, and potential interactions with other drugs.

“FDA approval is a lengthy process,” Adalja says. “We often find that drugs are approved in other countries before they’re approved in the U.S.” In fact, Japan has two other drugs approved to treat the flu that we don’t have in the U.S., he points out.

Reza Nassiri, M.D., a professor of pharmacology and toxicology, family and community medicine at Michigan State University, tells Yahoo Lifestyle that the gone-in-24-hours report for Xofluza is based on symptoms, and that research is needed to confirm that the drug actually kills the flu virus.

“It is certainly worth it to start limited clinical trials of this novel drug in the USA, but it is my understanding this will not happen until next year,” Nassiri says.

Judging from the preclinical and clinical studies conducted by Shionogi, Nassiri says, the drug doesn’t seem to pose any kind of life-threatening risks to flu patients who take it as a single dose.

Bottom line: This drug could be coming to the U.S., but you might be waiting a while.

Read more from Yahoo Lifestyle:

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