Karyopharm Plunges After FDA Briefing Materials Raise Questions About Safety of Multiple Myeloma Drug

Shares of Karyopharm Therapeutics plunged nearly 40 percent in trading Friday after the U.S. Food and Drug Administration (FDA) released briefing materials ahead of next week’s advisory committee meeting for the company’s experimental multiple myeloma treatment. The briefing materials indicate that Newton, Mass.-based Karyopharm faces much longer odds of seeing selinexor, a first-in-class, oral Selective Inhibitor of Nuclear Export (SINE) compound, approved for the treatment of patients with Penta-refractory multiple myeloma. The company is seeking approval of the drug for patients who have received at least three prior therapies. The company’s New Drug Application is based on data from the Phase IIb STORM trial that included 123 patients with RRMM who had received at least three prior treatments. Trial data showed an overall response rate of 25.4 percent, which included 23 patients who experience a partial response. When the FDA accepted Karyopharm’s New Drug Application, the regulatory agency granted the company priority review and assigned an action date of April 6, 2019, under the Prescription Drug User-Fee Act.