A single dose of baloxavir marboxil was superior to placebo in controlling influenza symptoms in patients with uncomplicated disease, and did not appear to have any clinically significant adverse effects, according to new findings published in the New England Journal of Medicine.

Baloxavir marboxil is a selective inhibitor of influenza cap-dependent endonuclease, and has demonstrated activity in preclinical models with both influenza types A and B, including resistant strains. A phase 2 and phase 3 study were conducted to assess the efficacy and safety of baloxavir in patients with uncomplicated influenza.

In the phase 2 study, 389 patients were randomly assigned to single doses of baloxavir (10, 20, or 40 mg) or placebo. The median time to alleviating symptoms was significantly shorter in each of the baloxavir dose groups (54.2 hours in the 10-mg group, 51.0 hours in the 20-mg group, and 49.5 hours in the 40-mg group) vs placebo (77.7 hours; P =.009, P =.02, and P =.005, respectively).

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In the phase 3 study, 1064 patients were randomly assigned to receive a single oral dose of baloxavir (40 mg for patients weighing <80 kg or 80 mg for those weighing ≥80 kg), oseltamivir (75 mg twice daily for 5 days), or placebo. The median time to alleviation of symptoms was 53.7 hours with baloxavir vs 80.2 hours (P <.001) with placebo, and similar results were seen for baloxavir vs oseltamivir. Viral load reduction was greater with baloxavir after 1 day as compared with placebo or oseltamivir. The frequency of adverse events were similar in the 3 groups, occurring in 20.7% for baloxavir, 24.6% for placebo, and 24.8% for oseltamivir.

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“Because this treatment is inhibitory for influenza virus strains resistant to neuraminidase inhibitors or M2 ion-channel inhibitors, [baloxavir] could provide an option for patients with infections caused by such viruses,” wrote the authors.


Hayden FG, Sugaya N, Hirotsu N, et al. Baloxavir marboxil for uncomplicated influenza in adults and adolescents [published online September 6, 2018]. N Engl J Med. doi: 10.1056/NEJMoa1716197