Baloxavir Marboxil: A Review in Acute Uncomplicated Influenza

Baloxavir marboxil (Xofluza®; hereafter referred to as baloxavir), the prodrug of baloxavir acid, is a first-in-class, small molecule inhibitor of the polymerase acidic (PA) protein subunit of the influenza virus polymerase complex. Baloxavir (after conversion to baloxavir acid) acts to block influenza virus replication by inhibiting the cap-dependent endonuclease activity of the PA protein. Taken orally as a single dose, baloxavir is approved in the USA for the treatment of acute uncomplicated influenza in patients ≥ 12 years of age who have been symptomatic for ≤ 48 h. Data from randomized, double-blind, placebo- and oseltamivir-controlled phase III trials have shown that baloxavir is efficacious in improving influenza symptoms both in otherwise healthy adolescents and adults and in those at high risk of influenza complications, displaying similar efficacy to that of oseltamivir. Furthermore, there is evidence that baloxavir can reduce influenza viral load more rapidly than oseltamivir. Baloxavir has activity against influenza A and B viruses (including strains resistant to neuraminidase inhibitors) and is well tolerated. Evidence of the emergence and likely human-to-human transmission of variant viruses with reduced susceptibility to baloxavir highlights the importance of monitoring and surveillance for changes in influenza virus drug susceptibility patterns. However, currently available evidence suggests that baloxavir, with the benefits of a single oral dose regimen, provides a useful alternative to neuraminidase inhibitors for the treatment of acute uncomplicated influenza in adolescents and adults.