Baloxavir Marboxil Approved for Flu Patients

The US Food and Drug Administration (FDA) has approved baloxavir marboxil (Xofluza) for the treatment of acute uncomplicated influenza (flu) in patients 12 years and older who have been symptomatic for up to 48 hours.

As the first new antiviral flu therapy with a novel mechanism of action to be approved by the FDA in 2 decades, physicians can add the single-dose, oral treatment to their repertoire for the ensuing 2018-19 flu season.

The Shionogi Inc. therapy, which received priority review designation from the FDA in June, was backed by the results of the phase 3 CAPSTONE study trials, in which single-dose baloxavir marboxil was compared with twice-daily placebo or oseltamivir 75 mg over 5 days.

Investigators had evaluated the efficacy and safety of baloxavir marboxil in1832 patients across the US and Japan, with a primary endpoint of time to alleviation of symptoms. Key secondary endpoints included time to resolution of fever, time to cessation of viral shedding and the proportion of participants positive for influenza virus titer, or virus levels in the body, by time point.

CAPSTONE-1 reported that patients on baloxavir marboxil met primary and secondary endpoints versus those on placebo—significantly reducing the duration of flu symptoms by more than 1 day (median time 53.7 hours vs 80.2 hours; P < .0001); significantly reducing the duration of fever by more than 1 day (median time 24.5 hours vs 42 hours; P < .0001); significantly reducing the length of time viruses continued to be released from the body (median time of viral shedding; 24 hours vs 96 hours; P < .0001); and significantly reducing the levels of virus in the nose and throat from 24-120 hours.

In the other treatment arm, patients reported no difference in time to alleviation of symptoms, as well as similar rates of adverse effect incidence and tolerability. The most common reactions in patients administered baloxavir marboxil included diarrhea and bronchitis.

Antiviral therapies such as baloxavir marboxil, when administered within 48 hours of a patient showing flu symptoms, have the capability to lessen symptoms and shorten the duration of time a patient feels sick, Debra Birnkrant, MD, director of the FDA’s Center for Drug Evaluation and Research’s Division of Antiviral Products, said.

“Having more treatment options that work in different ways to attack the virus is important because flu viruses can become resistant to antiviral drugs,” Birnkrant said.

That said, they should not replace annual vaccinations—the golden standard in flu care, FDA Commissioner Scott Gottlieb, MD, said.

“Flu season is already well underway, and the U.S. Centers for Disease Control and Prevention recommends getting vaccinated by the end of October, as seasonal flu vaccine is one of the most effective and safest ways to protect yourself, your family and your community from the flu and serious flu-related complications, which can result in hospitalizations,” Gottlieb said in a statement.