I used to work with the inventor of Relenza (Professor Mark von...

I used to work with the inventor of Relenza (Professor Mark von Itzstein) as a project manager. And as far as the theory and computer modelling of the spike proteins involved and the drug substrate, it is essentially almost impossible(I won't say impossible cause, crap happens in science) for the influenza virus to mutate enough to become resistant to Relenza and still be a viable virus particle that is capable of spreading the virus.

It is either a viable virus particle, and susceptible to Relenza, OR somehow resistant to Relenza, but then it won't be a viable virus-spreading entity. Sort of a virus-particle version of one cutting of one's nose, to spite one's face.

Obviously, as everyone probably knows the price paid for being such an almost perfect drug from a mode-of-action view point is that it suffers from poorer oral bio-availability, due to it's extreme hydrophilicty.

Tamiflu, copied Relenza's mode of action, and was modified to be lipophilic enough to increase the oral bio-availabilty of the molecule, but the trade off was that it now suffers from being a less than ideal drug with the considerable signs of resistance starting to emerge. But it's always easier to get a kid to take a pill rather than use a micro-aerolized drug inhaler.

choice