Export protein inhibitor shows activity against refractory myeloma

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patient at this dose level had a minimal response, three had stable disease, one had disease progression, and one was withdrawn from the study before disease assessment, with no evidence of progression.