A new single-dose treatment gives doctors a novel way to fight influenza infections
There’s a new flu drug on the shelf, the first in 20 years to get a thumbs-up from the U.S. Food and Drug Administration.
On October 24, the agency approved the use of the new antiviral drug, called baloxavir marboxil and sold under the brand name Xofluza. The drug, already available in Japan, works differently to kill the influenza virus from the other main class of flu antivirals, which includes the drug Tamiflu.
Antiviral drugs can help alleviate symptoms and shorten the flu’s duration, although flu vaccination remains the best way to prevent illness and death caused by the virus. “Prevention is better than treatment in all things and that’s absolutely true for flu,” says infectious disease physician Andrew Pavia of the University of Utah School of Medicine in Salt Lake City. “So the first message is: Get your flu shot.”
Many people aren’t getting that message: The U.S. Centers for Disease Control and Prevention reports October 25 that less than 40 percent of adults got a flu shot last year, the lowest amount in at least eight seasons. The 2017–2018 season in the United States was particularly deadly; about 80,000 people died of flu or related complications (SN Online: 9/27/18).
The recent bad flu season highlights the importance of having ways to treat the flu, in addition to preventing it. The approval of the new drug is “kind of a big deal in terms of our overall arsenal against flu,” Pavia says.
How does Xofluza work?
It’s a single-dose treatment for people 12 years or older who’ve had flu symptoms for less than two days. In clinical trials that included more than 1,000 adolescents and adults, a single dose of Xofluza reduced — by around a day to a day and a half — the time a patient experienced flu symptoms such as fever, aches and coughs, compared with a placebo. Although approved for use up to 48 hours after symptoms appear, Xofluza worked best when taken within 24 hours.
The drug fights the influenza virus in a new way compared with other antivirals such as Tamiflu, targeting a different step in the virus’s quest to make more of itself. Xofluza blocks part of the influenza virus that’s instrumental in making proteins that are required to produce extra copies of the virus within a host cell. Tamiflu, in contrast, prevents the virus from releasing whole virus particles from an infected cell.
Why do we need a drug that can fight the flu in a new way?
Since the introduction of the first flu antivirals, flu strains resistant to the drugs have appeared. Researchers have worried that, particularly if there’s a pandemic, a resistant flu virus might emerge and a ready treatment might not be available.
“So clearly we do need alternative treatments,” says Frederick Hayden, a clinical virologist at the University of Virginia School of Medicine in Charlottesville and a member of the team that assessed the drug in clinical trials.
Considering the resistance to Tamiflu’s class of drugs, Hayden thinks it makes sense to study a dual-drug approach that combines Xofluza with an older antiviral to lower the risk that additional resistant strains will emerge and to perhaps produce “a much more potent antiviral effect.”
How else is Xofluza different from Tamiflu?
In terms of symptom relief, there isn’t much difference. In the clinical trials of adults and adolescents, Xofluza alleviated symptoms about as quickly as Tamiflu. But the latter drug requires a bigger commitment from a patient: a twice-daily dose for five days, compared with Xofluza’s one dose.
The new drug did beat out the older one when it came to reducing the amount of virus in a patient in the first day after use. Whether that means patients taking Xofluza will be less likely to transmit the virus to others remains to be seen.
Who stands to benefit the most from Xofluza?
For other antivirals, such as Tamiflu, the CDC recommends their use primarily for individuals most at risk of developing complications, such as bronchitis or pneumonia, when they have the flu. This group includes those 65 and older and those with underlying diseases like asthma, heart disease, diabetes or chronic lung disease.
Xofluza has yet to be approved for use in these high-risk patients. But recent results, presented in October at the Infectious Disease Society of America’s annual meeting, showed the drug was effective for them. Along with having fewer days with symptoms, patients with risk factors such as asthma or chronic lung diseases who received Xofluza developed fewer complications than those on placebo.
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