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The first new antiviral treatment for acute, uncomplicated influenza in nearly 20 years received FDA approval in late October, just as a small uptick in outpatient visits for flu-like symptoms was reported.
Baloxavir marboxil is an oral influenza cap–dependent endonuclease inhibitor that disables flu viruses by interfering with viral messenger RNA transcription. It is indicated for patients aged 12 years or older who have had symptoms for no longer than 48 hours. Antiviral medication taken in that time frame can minimize symptoms and shorten the duration of illness, Debra Birnkrant, MD, director of the FDA’s Division of Antiviral Products, said in a statement.
“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 added. Three other FDA-approved influenza antiviral drugs are neuraminidase inhibitors that block release of the virus from infected cells. Resistance to neuraminidase inhibitors remains low, unlike the M2 ion-channel inhibitors amantadine and rimantadine, which have become resistant to almost all influenza A and B strains.
In preclinical models, baloxavir has shown therapeutic activity against influenza A and B strains. The majority of patients in phase 2 and phase 3 clinical trials had influenza A virus infections. Among 400 patients in the phase 2 trial, symptoms lasted significantly less time for those who received baloxavir compared with the placebo group. Treated patients also had significantly lower influenza virus titer levels on the second and third days of treatment.
The phase 3 trial compared baloxavir with placebo and another antiviral, the neuraminidase inhibitor oseltamivir. Among 1064 patients in the intention-to-treat analysis, symptom duration was shorter in the baloxavir group than in the placebo group. It took about 54 hours for symptoms to resolve in both treatment groups. Viral load declined significantly faster among patients who received baloxavir than among those who received either oseltamivir or placebo.
Common adverse events included diarrhea and bronchitis.
Voelker R. New Flu Drug Approved. JAMA. 2018;320(21):2193. doi:10.1001/jama.2018.18772
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