Selinexor-Containing Regimens for the Treatment of Patients with Multiple Myeloma Refractory to Chimeric Antigen Receptor T-Cell (CAR-T) Therapy

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.1854-1854
• Main Authors: Chari, Ajai, Vogl, Dan T., Jagannath, Sundar, Jasielec, Jagoda K., DeCastro, Andrew, Unger, TJ, Shah, Jatin, Jakubowiak, Andrzej
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-128887

Introduction: There are limited data on treatment options for patients with multiple myeloma whose disease has progressed after chimeric antigen receptor T-cell (CAR-T) therapy. Selinexor is a novel, oral selective inhibitor of nuclear export (SINE) that forces nuclear retention and activation of tumor suppressor proteins. Selinexor plus low dose dexamethasone (Sel-dex) was recently approved in the United States based on data from the STORM study wherein, Sel-dex induced an overall response rate (ORR) of 26.2% in patients with penta-exposed, triple-class refractory multiple myeloma. The activity of Sel-dex was preserved regardless of specific prior therapies, as expected given its unique and novel mechanism of action. The efficacy of selinexor after CAR-T therapy remains unknown. Here, we report on observations of the efficacy of Sel-dex alone or administered as a triplet in combination with bortezomib or carfilzomib in patients with multiple myeloma whose disease has progressed after CAR-T therapy. Methods: We identified 7 patients across all selinexor myeloma trials who had received lymphodepleting conditioning (fludarabine/cyclophosphamide n=6; Cyclophosphamide n=1) followed by an effective dose of CAR-T cell therapy (>108 CAR-positive cells targeting B-cell maturation antigen) for their multiple myeloma prior to being enrolled in a trial using a selinexor-containing regimen. Four were female and 3 were male. Median age was 64 years (range: 35-70 years). One patient was treated in the STORM study, with selinexor (starting at 80 mg twice-weekly) and dexamethasone (20 mg twice-weekly), 1 patient was treated with selinexor (100 mg once-weekly) plus bortezomib (1.3 mg/m2 once-weekly for 4 of 5 weeks) and dexamethasone (40 mg once-weekly) and 5 patients were treated with selinexor (100 mg once-weekly) plus carfilzomib (20/56 mg/m2 or 20/70 mg/m2) and dexamethasone (40 mg once-weekly or 20 mg twice-weekly). Response was assessed by the treating physician per International Myeloma Working Group (IMWG) criteria. Results: Patients had a median of 10 prior therapeutic regimens (range:5-15), all had high-risk cytogenetics, and 6 of the 7 had rapidly progressing disease as indicated by the percent increase in paraprotein (17-91%) between screening and Cycle 1 Day 1 (range: 7-22 days). All patients responded to treatment, including 1 unconfirmed complete response (uCR), 2 very good partial responses (VGPR), 3 partial responses (PR), and 1 minimal response (MR). Resp