The study, performed in centers in Canada, the United States, and Denmark, was designed primarily to identify the recommended dose of oral selinexor for phase 2 trials, with or without corticosteroids.
A total of 84 patients were enrolled, including 22 with MM and 3 with Waldenstrom macroglobulinemia in the dose-escalation phase, and 59 with MM in the dose expansion phase.
In the dose-expansion phase, patients were treated with one of two dosing schemes: either selinexor at a dose of 45 or 60 mg/m2 plus dexamethasone 20 mg twice weekly in 28-day cycles, or selinexor in a 40 mg or 60 mg flat dose without corticosteroids in 21-day cycles.
As a single agent, selinexor showed minimal activity, with an ORR of 4%, and clinical benefit rate of 21% in 57 patients.
Among 12 patients assigned to the 45 mg/m2 selinexor dose plus dexamethasone, the ORR was 50%, consisting of one complete response and five partial responses. In addition, one patient at this dose level had a minimal response, three had stable disease, one had disease progression, and one was withdrawn from the study before disease assessment, with no evidence of progression.