THURSDAY, Sept. 6, 2018 -- An experimental single-dose flu drug shows promise as a new way to alleviate the misery of influenza, researchers say.
The drug -- called baloxavir -- worked better than no treatment in one phase of a new study. The study also found it as effective as the current standard drug, oseltamivir (Tamiflu), at controlling symptoms such as coughing, sore throat, headache, fever, muscle and joint pain, and fatigue.
Moreover, in light of concerns about flu-drug resistance, most patients treated with baloxavir responded as expected, the study authors said.
"There are few approved influenza antivirals, and current treatments have limitations," said study lead author Dr. Frederick Hayden, of the University of Virginia School of Medicine.
"For example, currently circulating influenza viruses are resistant to the older class of antivirals," he said. These include the drugs amantadine (brand name Symmetrel) and rimantadine (Flumadine).
Resistance is also growing to the class of drugs including widely used Tamiflu and Relenza (zanamivir), Hayden said. "Consequently, there are medical needs for new anti-influenza agents with different mechanisms of action and greater potency," he added.
Hayden, professor emeritus of clinical virology and medicine, said the new study indicates that baloxavir resolves flu symptoms as quickly, effectively and safely as current options, without yet raising concerns about resistance. It also demonstrated "significantly greater antiviral effects," he added.
Also, while Tamiflu must be taken twice a day for five days, baloxavir requires just one dose.
The investigation was funded by the drug company Shionogi, Inc., which developed and manufactures baloxavir.
Baloxavir is approved for use in Japan. In the United States, it remains an "investigational drug," with the U.S. Food and Drug Administration expected to decide on approval by the end of this year.
The new study, which was published Sept. 6 in the New England Journal of Medicine, unfolded in two trials, both involving otherwise healthy flu patients at low risk for influenza complications.
One trial was conducted during the 2015-2016 flu season. About 400 patients, aged 20 to 64, received one of three doses of baloxavir (ranging from 10 to 40 milligrams) or a placebo. Flu symptoms eased notably faster among all three baloxavir groups, compared with placebo (untreated) patients, the findings showed.
The following flu season, nearly 1,100 patients, aged 12 to 64, were treated with baloxavir or Tamiflu. The drugs relieved symptoms in roughly the same time period, with similar side-effect risk.
However, about 10 percent of the baloxavir patients had a less than robust response to the drug. Hayden acknowledged that "the clinical and public health implications of reduced susceptibility to baloxavir are not fully understood."
Dr. Timothy Uyeki, author of an accompanying journal editorial, heads the influenza division at the U.S. Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases.
"There is a need for antiviral drugs with new mechanisms of action," he agreed.
Uyeki highlighted the benefit of baloxavir's single-dose regimen. Besides its convenience, it "avoids concerns about compliance with a five-day treatment course of oseltamivir," he said.
But he also stressed the need for further testing.
It remains unclear what benefits might accrue from combining baloxavir with Tamiflu, Uyeki noted.
Also, he cautioned, the current research only included otherwise healthy people aged 12 to 64 who were not at high risk for flu complications. Whether baloxavir will benefit high-risk groups -- young children, the elderly, pregnant women and others with underlying chronic medical conditions -- remains unknown, Uyeki said.
"A lot more studies are needed of the clinical benefit of baloxavir treatment of influenza in high-risk outpatients," he added.
There's more on flu treatment at the U.S. National Institute of Allergy and Infectious Diseases.
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