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The Food and Drug Administration announced yesterday it had granted approval of a new one-dose drug to fight influenza.

It is what this drug does that is so very interesting.  Instead of targeting neuraminidase, the substance that allows virus particles to escape from a host cell that has been compromised, this new drug attacks an enzyme that the flu virus needs to replicate itself -- period.  Also, instead of a course of capsules, you take one dose and you're treated.

The drug is called Xofluza (baloxavir marboxil) and it is unknown when it will be available in the U.S.  

From a September press release:

"Baloxavir marboxil, discovered and developed by Shionogi, has a novel mechanism of action that inhibits cap-dependent endonuclease, an essential enzyme for viral replication. The regimen for baloxavir marboxil is a single-oral dose to treat uncomplicated influenza, which is different from most currently available antiviral treatments. In non-clinical studies, baloxavir marboxil demonstrated an antiviral effect against a wide range of influenza viruses including oseltamivir-resistant strains and avian strains (H7N9, H5N1).^{12, 13, 14}

"Shionogi and the Roche Group which includes Genentech in the U.S. are in a license and collaboration agreement to further develop and commercialize baloxavir marboxil globally. Under the terms of this agreement, the Roche Group holds worldwide rights to baloxavir marboxil excluding Japan and Taiwan where the rights are retained exclusively by Shionogi. Roche will further investigate baloxavir marboxil in a global Phase III development program including pediatric and severely ill hospitalized populations with influenza. Shionogi will conduct a post-exposure Phase III prophylaxis study in Japan in the 2018/2019 flu season."

I do not know if this is the Holy Grail of flu drugs:  Something that would attack all strains of the virus and be immune to immunity.  But it does appear to be effective against those strains that have acquired an immunity to Tamiflu, and also apparently dramatically reduces the actual viral load of the bug once it is in the human body pretty aggressively. This makes it a much better candidate for combating potential pandemic strains such as H5N1, H5N6, H7N9, and H9N2.

Roche has been manufacturing Xofluza to meet demand in Japan, where the drug went on sale in February. It is unknown when it will be available for sale in the U.S.