Drug That Claims to Kill Flu as Soon as 1 Day Okayed in Japan

Megan Brooks

February 23, 2018

Japan's health ministry has approved baloxavir marboxil tablets (Xofluza, Shionogi & Co Ltd), a drug that reportedly can kill influenza types A and B in as little as 1 day among some patients.

Baloxavir marboxil, a novel cap-dependent endonuclease inhibitor, can kill influenza viruses in 24 hours, although some symptoms could last longer, the company said, according to the Wall Street Journal. It suppresses viral replication by a mechanism different from that of existing anti-influenza drugs.

Unlike neuraminidase inhibitors, such as oseltamivir (Tamiflu, Genentech), which inhibit the action of neuraminidase (an enzyme that frees viruses from the infected cells' surface), baloxavir marboxil prevents replication by inhibiting cap-dependent endonuclease activity of the viral polymerase.

Also unlike oseltamivir, which necessitates twice-daily doses over 5 days to treat the flu, baloxavir marboxil is taken in a single dose regardless of age, making it convenient and possibly improving adherence, the company said. 

Baloxavir marboxil was tested in the randomized, double-blind, multicenter, parallel-group, placebo- and active-controlled study known as CAPSTONE-1. A total of 1436 otherwise healthy patients diagnosed with influenza participated. 

Results of the trial, reported at Infectious Disease Week 2017, showed significant improvement in median time to alleviation of symptoms with baloxavir compared with placebo (53.7 hours vs 80.2 hours; P < .0001).

There was also significantly faster resolution of fever with baloxavir than placebo (24.5 hours vs 42 hours; P < .0001). 

The study also found significant improvement compared with placebo or oseltamivir for key virologic endpoints. The percentage of patients determined to be positive for influenza virus titer was significantly lower in the baloxavir group than the oseltamivir group at 1, 2, and 4 days from the start of treatment, the company reported. In addition, the time to cessation of viral shedding was significantly decreased with baloxavir compared with oseltamivir.

Shionogi said it will launch Xofluza immediately in Japan after the National Health Insurance price listing, but the drug would not be up for approval in the United States before 2019, according to the Wall Street Journal.

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