The FDA is corrupt so who knows what is going to happen. But, if they are granting breakthrough to a drug with damaging side effects then they would be hard pressed to explain why they would not grant AA to SRPT proven safe and effective. So if you're a doc going to prescribe a medication for DMD which would you chose? Any Drs. on the board here?
It's risk vs reward. Many kids on drisapersen do well w/o side effects. The FDA made the right call. They can still give AA to SRPT or if not AA, they can still give BTD. They are going to consider the merits of eteplirsen based on eteplirsen only.