I think what Dew's main point is, is that there is very little (if any) room for error.
I agree with Dew's point that ponatinib approval based on the PACE results may already be "baked in" to the current PPS. In that respect, you are correct that any little hiccup could send the share price crashing. It would be a fairly similar story to what INCY is going through right now.