Selinexor Plus Bortezomib and Dexamethasone Versus Bortezomib and Dexamethasone for Previously-Treated MM?

The phase III BOSTON study found that once-weekly selinexor, bortezomib, and dexamethasone is a novel, effective, and convenient treatment option for previously treated patients with multiple myeloma (MM) compared with twice-weekly bortezomib and dexamethasone. The results were published in The Lancet.

The randomized, open-label trial was conducted at 123 sites in 21 countries and included adults with MM who had previously been treated with one to three lines of therapy, including proteasome inhibitors. Patients (n = 402) were randomized 1:1 to receive selinexor 100 mg once weekly, bortezomib 1.3 mg/m² once weekly, and dexamethasone 20 mg twice weekly (triplet; n = 195) or bortezomib 1.3 mg/m² twice weekly for the first 24 weeks and once weekly thereafter and dexamethasone 20 mg four times per week for the first 24 weeks and twice weekly thereafter (doublet; n = 207). Patients were stratified base on previous proteasome inhibitor therapy, lines of treatment, and MM stage.

Median follow-up was 13.2 months (range, 6.2-19.8 months) for the selinexor, bortezomib, and dexamethasone group and 16.5 months (range, 9.4-19.8 months) for the bortezomib and dexamethasone group. Median progression-free survival (primary endpoint) was 13.93 months (95% confidence interval [CI], 11.73 to not evaluable) in the triplet group versus 9.46 months (95% CI, 8.11-10.78) in the doublet group (hazard ratio, 0.70; 95% CI, 0.53-0.93; P = 0.0075).

The most common grade 3/4 adverse events in the triplet and doublet cohorts were thrombocytopenia (n = 77 [39%] vs. n=35 [17%], fatigue (n = 26 [13%] vs. n = 2 [1%]), anemia (n = 31 [16%] vs. n = 20 [10%]), and pneumonia (n = 22 [11%] vs. n = 22 [11%]). Grade 2 or higher peripheral neuropathy occurred less often in the selinexor, bortezomib, and dexamethasone group (n = 41; 21%) than the bortezomib and dexamethasone cohort (n = 70; 34%; odds ratio, 0.50; 95% CI, 0.32-0.79; P = 0.0013).

Deaths occurred in 47 patients (24%) in the selinexor, bortezomib, and dexamethasone group and 62 (30%) in the bortezomib and dexamethasone group.