Impact of prior treatment on selinexor, bortezomib, dexamethasone outcomes in patients with relapsed/refractory multiple myeloma: Extended follow‐up subgroup analysis of the BOSTON trial

Abstract Objectives To analyze the impact of prior therapies on outcomes with selinexor, bortezomib, and dexamethasone (SVd) versus bortezomib and dexamethasone (Vd) in 402 patients with relapsed/refractory multiple myeloma (RRMM) in the phase 3 BOSTON trial. Methods Post hoc analysis of progression‐free survival (PFS), overall survival (OS), and safety for lenalidomide‐refractory, proteasome inhibitor (PI)‐naïve, bortezomib‐naïve, and one prior line of therapy (1LOT) patient subgroups. Results At a median follow‐up of over 28 months, clinically meaningful improvements in PFS were noted across all groups with SVd. The median SVd PFS was longer in all subgroups (lenalidomide‐refractory: 10.2 vs. 7.1 months, PI‐naïve: 29.5 vs. 9.7; bortezomib‐naïve: 29.5 vs. 9.7; 1LOT: 21.0 vs. 10.7; p < .05). The lenalidomide‐refractory subgroup had longer OS with SVd (26.7 vs. 18.6 months; HR 0.53; p = .015). In all subgroups, overall response and ≥very good partial response rates were higher with SVd. The manageable safety profile of SVd was similar to the overall patient population. Conclusions With over 2 years of follow‐up, these clinically meaningful outcomes further support the use of SVd in patients who are lenalidomide‐refractory, PI‐naïve, bortezomib‐naïve, or who received 1LOT (including a monoclonal antibody) and underscore the observed synergy between selinexor and bortezomib.