In answer to your question as to what is standing in the way of filing NDAs for various indications.
PDD Too small of a trial. Only one trial. PD No trial at all for PD. AD Filing process started in EU. Adult Rett Small trial. I suspect the FDA would rather have a filing for pediatric and adult in one NDA. Pediatric Rett Awaiting guidance from the FDA on the current trial. See adult Rett response above.
My guess is that the US and AU filings for AD are waiting on pediatric Rett guidance from the FDA before a decision on those filings is made.