Xofluza (baloxavir marboxil)

The following drug information is obtained from various newswires, published medical journal articles, and medical conference presentations.


Approval Status:

Approved October 2018

Specific Treatments:

acute uncomplicated influenza and in people at high risk of developing flu-related complications

Find Related Trials for The Following Conditions

General Information

Xofluza (baloxavir marboxil) is an antiviral drug with activity against the influenza virus. 

Xofluza is specifically indicated for the treatment of acute uncomplicated influenza in patients 12 years of age and older who have been symptomatic for no more than 48 hours. The FDA approval of Xofluza was expanded in October of 2019 to include the treatment of acute, uncomplicated influenza, or flu, in people 12 years of age and older who have been symptomatic for no more than 48 hours and who are at high risk of developing flu-related complications.

Xofluza is supplied as a tablet for oral administration. A single dose of Xofluza should be administered orally within 48 hours of symptom onset with or without food. Avoid co-administration of Xofluza with dairy products, calcium-fortified beverages, polyvalent cation-containing laxatives, antacids, or oral supplements (e.g., calcium, iron, magnesium, selenium, or zinc). The dose of Xofluza depends on weight, as follows:

• Patient Body Weight: 40 kg to less than 80 kg, the recommended dose is a single dose of 40 mg 

• Patient Body Weight: At least 80 kg, the recommended dose is a single dose of 80 mg 

Clinical Results

FDA Approval

The FDA approval of Xofluza was based on two randomized controlled clinical trials of 1,832 patients where participants were assigned to receive either Xofluza, a placebo, or another antiviral flu treatment (oseltamivir) within 48 hours of experiencing flu symptoms. The primary endpoint of both trials, time to alleviation of symptoms, was defined as the time when all seven symptoms (cough, sore throat, nasal congestion, headache, feverishness, myalgia, and fatigue) had been assessed by the subject as none or mild for a duration of at least 21.5 hours. In both trials, Xofluza treatment at the recommended dose resulted in a statistically significant shorter time to alleviation of symptoms compared with placebo in the primary efficacy population. In Trial 2, there was no difference in the time to alleviation of symptoms between subjects who received Xofluza (54 hours) and those who received oseltamivir (54 hours). For adolescent subjects (12 to 17 years of age) in Trial 2, the median time to alleviation of symptoms for subjects who received Xofluza was 54 hours compared to 93 hours in the placebo arm. 

The expanded indication for Xofluza was approved based on results from the Phase III CAPSTONE-2 study of a single dose of 40 mg or 80 mg of Xofluza compared to oseltamivir (75 mg twice daily for five days), or placebo in people 12 years of age or older who met CDC criteria for being at high risk of complications from the flu. Xofluza significantly reduced the time to improvement of flu symptoms compared to placebo, including in people infected with the flu type B virus.

Side Effects

Adverse effects associated with the use of Xofluza may include, but are not limited to, the following:






Mechanism of Action

Baloxavir marboxil is a prodrug that is converted by hydrolysis to baloxavir, the active form that exerts antiinfluenza virus activity. Baloxavir inhibits the endonuclease activity of the polymerase acidic (PA) protein, an influenza virus-specific enzyme in the viral RNA polymerase complex required for viral gene transcription, resulting in inhibition of influenza virus replication. The 50% inhibitory concentration (IC50) of baloxavir was 1.4 to 3.1 nM (n=4) for influenza A viruses and 4.5 to 8.9 nM (n=3) for influenza B viruses in a PA endonuclease assay. Viruses with reduced susceptibility to baloxavir have amino acid substitutions in the PA protein.

Additional Information

For additional information regarding Xofluza or acute uncomplicated influenza, please visit https://www.xofluza.com/