Influenza Antiviral Drug Baloxavir Marboxil

What is baloxavir marboxil?

Baloxavir marboxil (trade name Xofluza®) is an influenza (flu) antiviral drug given as a pill in a single dose by mouth that was approved on October 24, 2018, by the U.S. Food and Drug Administration (FDA). More information is available in the FDA press release.

Who can take baloxavir?

Baloxavir is currently approved by the FDA for treatment of flu in children aged 5 years to less than 12 years who do not have any chronic medical conditions, and for all people aged 12 years and older. Baloxavir also is approved by the FDA for post-exposure prophylaxis of flu in people aged 5 years and older. CDC does not recommend use of baloxavir in pregnant people, breastfeeding people, outpatients with complicated or progressive illness, severely immunosuppressed people, or hospitalized patients because of the lack of information on use of baloxavir for these groups to date.

How is baloxavir given?

Baloxavir is available as an oral suspension for children or as tablet, given as a single dose by mouth. (The oral suspension when constituted by the pharmacy has a concentration of 2 mg/kg. There are also 20 mg and 40 mg tablets and dosage depends on patient weight.)

What other antiviral drugs for flu are available?

In the United States, there are four FDA-approved antiviral drugs recommended by CDC this season:

  • oseltamivir (available as a generic version or under the trade name Tamiflu®)
  • zanamivir (trade name Relenza®)
  • peramivir (trade name Rapivab®), and
  • baloxavir (trade name Xofluza®).

More information regarding antiviral drugs is available.

Where can I get baloxavir?

Antiviral drugs for flu treatment are not sold over the counter. You can only get them from a pharmacy if you have a prescription from your doctor or health care provider. More information regarding supply of antiviral drugs is available.

Why was there a need for a different antiviral drug for flu?

Baloxavir works differently than the other currently recommended flu antiviral drugs, which are neuraminidase inhibitors (oseltamivir, zanamivr and peramivir). Given how frequently flu viruses change and the potential for flu viruses to develop resistance or reduced susceptibility to one or more flu antiviral drugs, it is good to have more options for treating flu. For example, flu viruses that are resistant to oseltamivir should still be susceptible to baloxavir.

Can antiviral resistance to baloxavir occur?

Reduced susceptibility and antiviral resistance mean, respectively, that a flu virus has changed in such a way that antiviral drugs are less effective or not effective at all in treating or preventing illnesses with that flu virus. Flu viruses can develop reduced susceptibility or resistance to one or more antiviral drugs, including baloxavir. In randomized clinical trials, there was evidence of development of reduced susceptibility in some patients treated with baloxavir.

More information regarding antiviral resistance is available on the Influenza Antiviral Drug Resistance webpage.

How does CDC test for antiviral resistance to baloxavir?

CDC’s Influenza Division has taken specific actions in the laboratory to incorporate the antiviral drug baloxavir into routine virologic surveillance. This includes the creation and validation of assays to determine baloxavir susceptibility, and training of laboratorians to conduct baloxavir susceptibility testing.

More information regarding CDC labs’ preparation for testing baloxavir susceptibility is available.