The U.S. Food and Drug Administration (FDA) announced the approval of a new flu drug on Wednesday, October 24, 2018, making Xofluza (baloxavir marboxil) the first new anti-flu medication in nearly two decades.
In the clinical trials that were the basis for the drug’s fast-tracked FDA review, Xofluza reduced flu symptoms by a little more than a day in healthy patients over age 12.
“The efficacy is pretty similar to Tamiflu (oseltamivir) in that it shortens the duration for about 24 hours if it’s given within the first 48 hours of the onset of symptoms,” says Stan Deresinski, MD, a clinical professor in infectious disease at Stanford University in California. One major advantage of Xofluza is that it’s administered in a single dose as opposed to the five days of therapy that Tamiflu requires.
The pill will cost about $150 for patients without health insurance. Genentech, the company that will distribute the drug, plans on providing cost support for both insured and uninsured patients that would put the bill for therapy at $30 and $90, respectively. It is expected to be available in the United States in the coming weeks.
Although the severity of each flu seasons varies, the illness puts a substantial burden on health in the United States. According to Centers for Disease Control and Prevention (CDC) estimates, a record 900,000 people were hospitalized and more than 80,000 died from flu last season.
“With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical," said FDA Commissioner Scott Gottlieb, MD, in a statement announcing Xofluza’s approval. “This novel drug provides an important, additional treatment option.”
Dr. Gottlieb added that although a drug like Xofluza can help with flu symptoms, it’s no substitute for yearly vaccination. “Yearly vaccination is the primary means of preventing and controlling flu outbreaks,” he said.
What Makes Xofluza Different
Xofluza was discovered by the Japanese pharmaceutical company Shionogi, and is being developed globally by the Roche Group (which includes Genentech in the United States) and Shionogi. In February 2018, it was approved in Japan for the treatment of influenza types A and B.
Xofluza works through a different mechanism of action than other available anti-flu drugs. Once the flu virus gets into your system, it reproduces over and over and then spreads throughout the body. Xofluza works by inhibiting polymerase acidic endonuclease, the enzyme that allows the virus to reproduce. Tamiflu, by contrast, inhibits the enzyme that causes the spread of the virus after it reproduces.
“We’ve had to discard some medications that have been used for a long time because the virus had become resistant to them,” Dr. Deresinski says. Currently available flu drugs have maintained their efficacy and have met limited resistance so far, but that won’t last forever, he adds.
“It’s only a matter of time before resistance will occur with those drugs, and so it’s good to have a backup that works by a different mechanism and should remain active against those viruses,” he says.
Potential Public Health Benefit
Beyond treating individuals and shortening the duration of flu symptoms, Xofluza has a potential public health benefit, says Deresinski.
“It reduces the excretion of the virus more rapidly than Tamiflu,” he says. This means the time period when someone is infectious and can spread the flu should be shorter, which could mean fewer cases of the flu.
Some Concerns About Resistance
One note of concern about the new drug is the level of resistance, says Deresinski.
“In the Phase 2 trial, resistance only occurred 2.3 percent of the time; but in the larger Phase 3 trial, resistance happened 9.3 percent of the time. That’s about 1 in 10 people,” he says. “If that’s not a fluke, it does raise concern about how long you will be able use this drug before the virus is just resistant to it.”
What the New Drug Means for the Current Flu Season
How much of an impact will Xofluza have on this year’s flu? It depends, according to Deresinski.
“If we start seeing Tamiflu-resistant influenza, then it would potentially make an impact,” he says. “Purely in terms of outcomes in the patients that we know about, that is, those who are otherwise healthy other than the fact that they have influenza, it’s not going to make a great deal of difference.”
So far, there isn’t enough published research to be able to predict the efficacy or impact of the drug in the most vulnerable people, such as those who have to be hospitalized because of flu complications or pregnant women, says Deresinski.