Scooby, well said. I agree and share your frustration. But that's why I think if the crossover study results are good then the FDA will re-visit this NDA with the SPA and approve the drug.
I imagine that the FDA knows that for cost reasons and maybe duration of action reasons (or possibly even improved bone strength although this has only been alluded to) that many people would be switched to Uplyso and that they would look silly if there was any problem with the cross-over patients.
The FDA is being very careful because of the game-changing nature of the plant technology. Better for PLX in the long-run. PLX is very close and the barrier to entry into the biosimilar market as per the FDA is very high.