In October, the FDA approved baloxavir marboxil (Xofluza) for the treatment of acute, uncomplicated influenza in patients aged 12 years and older. The drug is the first new antiviral treatment for influenza in almost two decades.
“With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical. This novel drug provides an important, additional treatment option,” said FDA Commissioner Scott Gottlieb, MD.
Last year, influenza killed an estimated 80,000 people and hospitalized more than 900,000 individuals in the United States, according to the CDC. The severity of the 2017-2018 flu season contributed to the expedited approval of baloxavir marboxil, which was granted priority review by the FDA in June.
The FDA based approval on two randomized, controlled clinical trials that enrolled a total of 1,832 patients. Participants received either baloxavir marboxil, placebo, or oseltamivir. All patients experienced first influenza symptoms 48 hours or less before treatment and were otherwise healthy. Patients who received baloxavir marboxil experienced quicker relief from symptoms than those who took a placebo, 54 hours versus 80 hours. Baloxavir marboxil and oseltamivir had similar efficacy. Results were published in the September issue of the New England Journal of Medicine.
A polymerase acidic endonuclease inhibitor, baloxavir marboxil provides an alternative to the other influenza drugs approved in the U.S.—oral oseltamivir, inhaled zanamivir, and intravenous peramivir—which are all neuraminidase inhibitors. While the most recent CDC reports show that resistance to the three neuraminidase inhibitors remains low, influenza’s high degree of mutability means that that could change with little notice.
“Having more treatment options that work in different ways to attack the virus is important because flu viruses can become resistant to antiviral drugs,” said Debra Birnkrant, MD, director of the Division of Antiviral Products in the FDA’s Center for Drug Evaluation and Research.
Like the other approved treatments for influenza, baloxavir marboxil should be taken within 48 hours of the first appearance of symptoms. Unlike the others, it is a “once and done,” single-tablet, oral medication. It is not approved for children younger than age 12 years. Oseltamivir may be given to children as young as 2 weeks, while peramivir is approved for anyone over age 2 years, and zanamivir may be given to those over age 7 years.
According to the drug’s website, baloxavir marboxil should be available nationwide in mid-November. Developed by the Japanese pharmaceutical company Shionogi & Co, it will be distributed in the U.S. by Genentech. CNN reported that the wholesale acquisition price of baloxavir marboxil is $150; patients can get up to $60 off their cost with a coupon on the Xofluza website.
The FDA announcement of baloxavir marboxil’s approval emphasized that the drug is not a substitute for annual influenza vaccination, which provides the best protection against the flu and mitigates the severity of symptoms in those who contract it.
This year, the CDC recommends the use of any of the approved, age-appropriate vaccines without preference. After an absence of 2 years, the live-attenuated influenza vaccine nasal spray returns to the recommended list, along with inactivated influenza vaccine delivered by needle or jet injector and recombinant influenza vaccine. High-dose inactivated influenza vaccine and adjuvanted inactivated influenza vaccine are recommended for older patients. The intradermal flu vaccine (Fluzone Intradermal) is no longer being distributed in the U.S.
All cell-grown and recombinant vaccines and most regular-dose egg-based flu shots will be quadrivalent this season, as will the live-attenuated influenza vaccine. The vaccines protect against a different mix of viruses than last year and specifically target the following:
• A/Michigan/45/2015 (H1N1)pdm09-like virus
• A/Singapore/INFIMH-16-0019/2016 A(H3N2)-like virus (updated)
• B/Colorado/06/2017-like (Victoria lineage) virus (updated)
• B/Phuket/3073/2013-like (Yamagata lineage) virus
Based on the just-concluded Australian influenza season, this flu season should be relatively mild, and the vaccine appears to be well matched to the circulating viruses.
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