Baloxavir shows promise as postexposure prophylaxis for flu
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A study conducted at dozens of primary care clinics in Japan showed that household contacts of people with influenza were 86% less likely to develop influenza after receiving a single dose of baloxavir marboxil as postexposure prophylaxis.
The FDA originally approved baloxavir marboxil in October 2018 for the treatment of acute, uncomplicated influenza in patients aged at least 12 years — the first new influenza treatment in nearly 20 years. It expanded that approval last October to include patients at high risk for influenza-related complications, and is expected to decide on several pediatric-related applications involving the antiviral by Nov. 23.
In the new study, researchers enrolled 752 household contacts of 545 index patients at 52 primary care clinics and randomly assigned them in a 1:1 ratio to receive either baloxavir marboxil or placebo.
According to the findings, published today in The New England Journal of Medicine, influenza developed in 86% fewer contacts in the baloxavir group than in the placebo group, 1.9% vs. 13.6% (adjusted RR = 0.14; 95% CI, 0.06-0.3).
In a related editorial, Timothy M. Uyeki, MD, MPH, chief medical officer in the CDC’s Influenza Division, noted that most of the index patients in the study were children aged younger than 12 years and that more than half of them received treatment with baloxavir, which is not approved for children that young in the United States.
Also, 73% of household contacts received baloxavir within 24 hours after the onset of illness in their index patient, Uyeki noted. Not only is baloxavir not approved for influenza prophylaxis in the U.S. in patients of any age, but patients in the U.S. are less likely to seek treatment for influenza within 2 days of showing symptoms — when antiviral treatment is most effective — than patients in Japan, where they “typically seek medical care for influenza testing and early antiviral treatment soon after the onset of illness,” Uyeki wrote.
“This trial adds baloxavir to other antiviral agents (ie, the neuraminidase inhibitors oseltamivir and zanamivir) that have shown efficacy in reducing the transmission of influenza virus in households when used for early treatment in index patients and for postexposure prophylaxis in their contacts,” he wrote.
“Further studies are needed to assess whether administering additional doses of baloxavir for treatment and for postexposure prophylaxis might reduce the emergence and transmission of influenza viruses with reduced susceptibility to baloxavir and whether the combination of baloxavir for early treatment in symptomatic patients and oseltamivir for prompt postexposure prophylaxis in their close contacts might be useful for controlling institutional outbreaks.”
References:
- Ikematsu H, et al. N Engl J Med. 2020;doi:10.1056/NEJMoa1915341.
- Uyeki TM, et al. N Engl J Med. 2020;doi:10.1056/NEJMe2022702.
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