Xofluza (baloxavir marboxil) – New FDA Approval for Influenza Treatment

Baloxavir Marboxil (Xofluza): New FDA Approval for Influenza Treatment1,2,3,4

Baloxavir marboxil (Xofluza) was approved by the FDA on October 24, 2018 to treat influenza within 48 hours of onset of influenza symptoms. This approval has created many questions regarding the new product. The key points listed below will provide a general overview of important information with supporting detail available in the rest of the document.

Key Points:

  • Due to recent approval, baloxavir (Xofluza) is unlikely to be available from the manufacturer until at least the first quarter of 2019, with formulary coverage decisions by insurance companies potentially taking several additional months limiting utility of this medication this flu season due to lack of insurance coverage for the baloxavir (Xofluza).
  • Oseltamivir (Tamiflu) is an effective alternative, manufactured by the same company as baloxavir (Xofluza), and there is no current resistance to oseltamivir, according to the CDC.
  • Clinical trials are limited and only compare baloxavir (Xofluza) directly to placebo. One study did compare both baloxavir (Xofluza) and oseltamivir (Tamiflu) to placebo with no significant differences noted between the medications.
  • For the duration of this flu season it is recommended to continue utilization of oseltamivir (Tamiflu) for influenza treatment.

Availability, Cost & Coverage:

To better understand baloxavir (Xofluza) availability, indication for use, dosing and comparison to the currently available oseltamivir (Tamiflu) please review Table 1.

Table 1: baloxavir and oseltamivir comparison

*cost to patient will be largely dependent on insurance coverage. If not covered on formulary patient responsible for full cash price.

Clinical Evidence:

It must be noted that there are limited studies for baloxavir (Xofluza), all of which have been comparing the medication to placebo. There are no direct head-to-head studies comparing baloxavir to oseltamivir, likely because the same pharmaceutical company (Genentech) manufactures these products.

A Phase 2 clinical trial did compare both baloxavir (Xofluza) and oseltamivir (Tamiflu) to placebo, which showed greater antiviral activity in the baloxavir group, but no difference in the time to alleviation of symptoms. Both treatment options showed a 1 day reduction in flu symptoms.

Finally, while the mechanism of action for baloxavir is different from oseltamivir (selective inhibitor of cap-dependent endonuclease vs neuraminidase inhibitor) we are not seeing oseltamivir-resistant strains at this time, which is something the CDC is tracking. For 2016-2017 season: 100% of the tested influenza A(H1N1)pdm09 viruses were susceptible to oseltamivir (Tamilfu).

Current Recommendation:

For the duration of this influenza season, continued utilization of oseltamivir is recommended. The appropriate dose for influenza treatment within 48 hours of symptom onset in adults and adolescents 13 years and older is 75mg twice daily for 5 days. For pediatric patients the dose is weight based and can be found in the product monograph.


  1. Product Monograph for Xofluza. Genentech. South San Francisco, CA 94080. 2018.
  2. Hayden F, Sugaya N, Hirotsu N, Lee N, de Jong M, Hurt A, Ishida T, et al. Baloxavir Marboxil for Uncomplicated Influenza in Adults and Adolescents. N Engl J Med [Online] 2018 Sep 6;379(10):913-23. Available from doi: 10.1056/NEJMoa1716197
  3. https://www.cdc.gov/flu/weekly/overview.htm
  4. Product Monograph for Tamiflu. Genentech. South San Francisco, CA 94080. 2018.

Reviewed by: Angela Green, PharmD, BCPS & Tiffany Jenkins, PharmD, BCACP

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