Karyopharm Therapeutics Inc. said the U.S. Food and Drug Administration granted priority review to its application for Selinexor as a treatment for a highly resistant form of blood cancer.

The Newton, Mass.-based company is seeking approval for Selinexor as a treatment for patients with penta-refractory multiple myeloma. Multiple myeloma occurs when plasma cells, found in the bone marrow, become cancerous and grow out of control.

Patients with penta-refractory myeloma have previously received two proteasome inhibitors, Takeda Pharmaceutical Co. Ltd.'s Velcade and Amgen Inc.'s Kyprolis, the two immunomodulatory drugs, Celgene Corp.'s Revlimid and Pomalyst, and Johnson & Johnson's Darzalex as well as alkylating agents. These patients, however, do not respond to at least one proteasome inhibitor, at least one immunomodulatory drug and their most recent therapy.

The regulator set a decision date of April 6, 2019, to complete the drug's review. A priority review designation reduces the duration of FDA review to six months compared to 10 months for a normal application