Baloxavir

Baloxavir marboxil is an antiviral medication used for the treatment of influenza. It is a prodrug that is orally administered and rapidly converted in the body to baloxavir acid, the active form.

Mechanism of action: Baloxavir acid inhibits the cap-dependent endonuclease activity of the influenza virus polymerase acidic (PA) protein. By blocking the cap-snatching process required for viral mRNA transcription, it prevents viral replication in influenza A and B viruses.

Administration and dosing: Baloxavir marboxil is given as a single oral dose and is typically used within 48 hours of onset of influenza symptoms. Because it is a one-dose regimen, it offers a convenient alternative to multi-dose neuraminidase inhibitors. It is intended for the treatment of uncomplicated influenza and is not a substitute for treatment of severe illness or hospitalization in all cases. The drug should not be co-administered with products containing polyvalent cations (such as calcium, iron, or aluminum) within a short window, and timing should be adjusted accordingly.

Clinical efficacy: In clinical trials, baloxavir can reduce viral load more rapidly than placebo and may shorten the duration of fever and cough in otherwise healthy individuals. Comparisons with oseltamivir have shown similar efficacy in some studies, with differences varying by patient population and setting.

Safety and limitations: Common adverse events include diarrhea, bronchitis, and nausea. Serious allergic reactions are rare. As with all antivirals, use should be guided by a clinician, and resistance can emerge through substitutions in the viral PA gene (notably I38X), reducing susceptibility to baloxavir.

History and status: Baloxavir marboxil, marketed as Xofluza in several markets, was developed by Shionogi & Co. and approved for the treatment of uncomplicated influenza in 2018.