Karyopharm (KPTI) slumped 17% in the pre-market yesterday, ahead of data from a mid stage study of selinexor in treatment-resistant multiple myeloma. A couple of years ago, this same drug was pitted against Darzalex in the same indication and showed similar efficacy. An FDA filing was planned in 2018, which seems to be on track. The sell-off was therefore probably profit taking ahead of expected good news.
That is just what has happened after the data was released. The stock was up 22% after news came out that selinexor showed treatment effect in the mid-stage