I know that some work was done with potential prodrugs of...

I know that some work was done with potential prodrugs of Relenza in the years after launch, since it is the most obvious route to improve the pharmacokinetics of the drug, however none showed activity as good as the original inhaled drug. And that is pretty much where the research stopped, about 5 years ago.

However, when Relenza was first invented the starting material (Sialic acid (Neu5Ac)) was about $1000 a gram (it was isolated from the red combs on roosters heads) and was to expensive for a lot of research institutes etc. to play around with. But now due to it's popularity in medicinal chemistry and the need as a starting material for Relenza, other ways of isolating it from other sources have been sussed out and it is now less than $10/g.

So I am sure lots of other smaller research groups, (especially as an idea for a postgrad project) are trying to make good prodrugs of Relenza. Indian researchers especially love this kind of stuff.

However, nothing must of been found that is really good or we would of heard about it by now. I certainly know that less than 2 years ago, no breakthroughs had been made. MvI was/is working on a next generation of anti-influenza drugs based on other sugars etc. which computer modelling that I have seen, says should be better drugs. i.e. Relenza like activity, but more druggable. Of course though MvI, now has no connection with BTA.

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