Efficacy and Safety of Selinexor, Pomalidomide, and Dexamethasone (SPd) for Treatment of Patients with Relapsed or Refractory Multiple Myeloma (RRMM)
Methods: The SPd arm of the multi-arm STOMP study evaluated selinexor at multiple doses and schedules in combination with Pd (P doses tested consisted of 2 mg, 3 mg, or 4 mg QD) in patients with RRMM. Study objectives were to determine the maximum tolerated dose and the recommended Phase 2 dose to assess safety and to examine the efficacy of the SPd regimen. Response assessments were investigator-determined per International Myeloma Working Group criteria.
The investigator-assessed overall response rate (ORR) was 39.5% (95% CI 28.8, 51.0) for the entire cohort, 55.0% (95% CI 31.5, 76.9) for SPd60, and 43.8% (95% CI 19.8, 70.1) for SPd40. The very good partial response or better rate was 19.8% (95% CI 11.7, 30.1) in the entire cohort, 30.0% (95% CI 11.9, 54.3) in SPd60, and 31.3% (95% CI 11.0, 58.7) in SPd40. There were 2 stringent complete responses (CRs; 1 in SPd60 and 1 in SPd40, both TCE) and 1 CR (SPd40). For the entire cohort, the median time to response was 1.1 months (95% CI 1.0, 2.0).
Conclusions: The all-oral combination of SPd showed signs of preliminary efficacy and was generally tolerable in patients with RRMM. Although the ORR was greater in the SPd60 cohort, TEAEs were less frequent, duration of exposure was longer, and higher dose intensity was achieved for patients treated with SPd40. These data support the further evaluation of low-dose weekly selinexor in the ongoing EMN29 trial (NCT05028348) of SPd40 versus elotuzumab and Pd in TCE RRMM progressing immediately after a αCD38-containing line of therapy.