A breakthrough therapy designation is for a drug that treats a serious or life-threatening condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on a clinically significant endpoint(s) over available therapies.  In contrast, a fast track designation is for a drug that treats a serious or life-threatening condition, and nonclinical or clinical data demonstrate the potential to address unmet medical needs for the serious condition

Good catch Cancundude, I highlighted the two.  More weight is given to BT with evidence over data.  Substantial vs. Potential.  BP should be looking closer with this FDA release. JIMHO