Baloxavir marboxil

Baloxavir marboxil is a prodrug that is metabolised to the active form baloxavir acid also known as S‐033447. S‐033447 is a small molecule inhibitor of the cap‐dependent endonuclease of influenza A and B viruses. It has shown nanomolar antiviral activity against influenza A and B viruses in vitro. In murine models of seasonal influenza and avian influenza A(H5N1) or A(H7N9), orally administered baloxavir showed a rapid reduction in pulmonary viral loads and decreased mortality. Baloxavir significantly reduced the time for alleviation of symptoms and reduced virus titres at 24 and 48 hours post‐treatment at three different doses (10 mg, 20 mg and 40 mg) in a phase II study with patients experiencing uncomplicated influenza.