FDA Approves Baloxavir Marboxil for Patients at High Risk of Flu Complications

The US Food and Drug Administration (FDA) has approved a supplemental New Drug Application for baloxavir marboxil (Xofluza) for the treatment of influenza in individuals who are at increased risk of developing flu-related complications.

Baloxavir marboxil is a first-in-class, 1 dose oral agent that was first approved by the FDA in 2018 for the treatment of acute, uncomplicated influenza in individuals 12 years and older, who have been symptomatic for less than 48 hours. The medication had a novel proposed mechanism of action that inhibits polymerase acidic endonuclease, an enzyme essential for viral replication. When it was approved in 2018, it became the first new antiviral to treat influenza in 20 years.

“With the flu season rapidly approaching, we can now offer Xofluza as the first and only FDA-approved treatment option indicated specifically for those at high risk of flu complications,” said Levi Garraway, MD, PhD, chief medical officer and head of Global Product Development at Genentech said in a statement. “People with chronic conditions such as asthma, heart disease and diabetes are at higher risk of developing serious complications from the flu, so it is critical that these patients speak with their health care providers about possible treatment at the first signs and symptoms of the disease.”

According to the statement, the expanded indication was based upon the results from the phase 3 CAPSTONE-2 study. In this study, a single dose of 40 mg or 80 mg of baloxavir marboxil was compared to oseltamivir (75 mg twice daily for 5 days), or placebo in people 12 years of age or older who met the US Centers for Disease Control and Prevention's criteria for being at high risk of complications from the flu. This criterion defines people at high risk of serious flu complications as those who have conditions such as asthma, chronic lung disease, diabetes, heart disease, morbid obesity or adults 65 years of age or older.

In the multicenter, randomized, double-blind, phase 3 study, baloxavir marboxil reportedly reduced the time to the improvement of symptoms including in individuals with influenza type B virus (median time 73 hours versus 102 hours; p<0.001). The investigators observed similar efficacy results between baloxavir marboxil and oseltamivir regarding duration of symptom (median time 73 hours versus 81 hours). Among individuals infected with influenza type B, the median time to improvement of symptoms was shorter in the baloxavir group compared to the placebo group (75 hours versus 101 hours respectively).

Adverse events were reported in at least 1% of adults and adolescent participants treated with baloxavir marboxil included diarrhea (3%), bronchitis (3%), nausea (2%), sinusitis (2%) and headache (1%).

Baloxavir marboxil is being evaluated in a phase 3 development program, including children under the age of 1, severely ill individuals, patients hospitalized with influenza and in assessment of the potential to reduce transmission of the flu from an infected person to healthy people.

Baloxavir marboxil was discovered by Shionogi & Co., Ltd. and is being further developed and commercialized globally in collaboration with the Roche Group, including Genentech in the United States.