That's the risk vrtx is running by keeping US rights and paying 50% of development costs.
Answer is we should know after the phase IIB Efficacy is eye popping, tox on the other hand...tbd
I'm not invested in vrtx btw, too rich for me. I wouldn't be surprised if 950 blows up but I hope it works out, would be very cool and one of the few true biotech breakthrough drugs.