Setback for Karyopharm's selinexor in endometrial cancer sends shares tumbling

Following Discussion with the US Food and Drug Administration, Karyopharm Therapeutics (Nasdaq: KPTI) plans to initiate a new placebo-controlled randomized study of selinexor in the advanced or recurrent endometrial cancer p53 wild-type population.

The new data will support a future supplemental New Drug Application (sNDA) submission as the current top-line data from the SIENDO study are unlikely to support an sNDA approval, noted Karyopharm, whose shares plunged 40% to $6.26 by close of trading on Wednesday following the announcement.

During a productive meeting, Karyopharm and the FDA participants had differing views on the study significance and overall clinical benefit for the whole population and discussed that further exploration of patients with advanced or recurrent endometrial cancer with p53 wild-type is warranted. The company will continue to collect and analyze the SIENDO study data and work with the FDA to explore all regulatory pathways for patients with p53 wild-type.