Why This Antiviral Flu Drug May Be a Game Changer

Updated: Dec. 17, 2019

For this year's flu season, there are four drugs that are FDA-approved for treating people at high risk for severe symptoms.

flushotMarlon Lopez MMG1 Design/Shutterstock

Influenza is constantly changing, therefore, making it unpredictable. This means the timing, severity, and the length of flu season can vary. For the 2019-2020 season, influenza has been higher than normal, as the US has seen an estimated 1.7 million cases of the flu, 16,0000 flu-related hospitalizations, and 910 flu-related deaths, according to the Centers for Disease Control and Prevention (CDC). A new flu vaccine is created each year to try to fight the ever-changing virus; however, it’s hard to tell how well a vaccine is working when it’s early in flu season. Here is how long the flu lasts.

So what happens if you get vaccinated and still get the flu?

In late 2018, the U.S. Food & Drug Administration approved a new antiviral drug called baloxavir marboxil (Xofluza) to treat the flu after you get sick. It became the first new FDA-approved antiviral flu drug with a novel mechanism of action in almost 20 years. In October 2019, the FDA expanded the drug’s indication for the treatment of influenza to individuals who are at increased risk for developing flu-related complications, which includes adults 65 years of age or older, and those with asthma, chronic lung disease, diabetes, heart disease, or morbid obesity.

The FDA has approved a total of four drugs for fighting flu—baloxavir; oseltamavir (Tamiflu), which also is sold as a generic drug; zanamivir (Relenza); and peramivir (Rapivab).

How much different is baloxavir from oseltamivir (Tamiflu), the original flu-fighting drug?

Unlike oseltamivir, which inhibits influenza by blocking a viral enzyme called neuraminidase, baloxavir inhibits a “subunit of the viral polymerase, the enzyme responsible for influenza virus replication,” according to Harvard Medical School. Simply put: Baloxavir inhibits the virus’s ability to multiply, while oseltamivir and other drugs inhibit the virus’s ability to spread within the body.

Waleed Javaid, MD, director of infection prevention and control at Mount Sinai in New York says “both decrease duration of illness by approximately one day.” However, “baloxavir is taken once daily versus twice daily for oseltamivir; and baloxavir decreases viral load on day one more than oseltamivir. But the clinical implications of this are not clear at this time,” adds Dr. Javaid, referring to a study published in 2018 in The New England Journal of Medicine showing that baloxavir effectively alleviates flu symptoms in people with uncomplicated flu.

Currently, baloxavir is being further studied in several clinical trials that include children under the age of one, and severely ill, hospitalized patients, and it’s also being studied to measure its potential to reduce flu transmission from an infected individual to healthy individuals. The main advantage of baloxavir is that it’s effective as a single oral dose compared to oseltamivir, which needs to be taken twice daily for five days. Yet, oseltamivir is generically available, and could potentially be less expensive than baloxavir.

The drug is available for people age 12 and older who get diagnosed with the flu within 48 hours of experiencing symptoms. While the side effects are minimal, they do include diarrhea and bronchitis. “Baloxavir works by blocking a step where the influenza virus can replicate and multiply,” which is why it’s important to start the drug soon after infection, says Tina Ardon, MD, a family physician at Mayo Clinic in Jacksonville, Florida. “What this means clinically is that the patient has a shorter duration of symptoms and may be less likely to pass the infection to [others].” Here are 11 things doctors do to treat the flu.