Efficacy and Safety of Chimeric Antigen Receptor T-Cell Therapy for Relapsed/Refractory Immunoglobulin D Multiple Myeloma

Immunoglobulin D (IgD) multiple myeloma (MM) is a rare subtype of MM that carries a worse prognosis than non-IgD subtypes. Compared with non-IgD subtypes, IgD MM is associated with a shorter survival time. The application of chimeric antigen receptor (CAR) T-cell therapy for patients with relapsed or refractory multiple myeloma (R/R MM) has increasing evidence as an efficacious treatment. This study was designed to investigate efficacy and safety of chimeric antigen receptor (CAR) T-cell therapy for relapsed/refractory IgD MM (R/R IgD MM). In this single-arm, phase 2 trial, patients diagnosed with R/R IgD MM were infused with either a combination of anti-B-cell maturation antigen and anti-CD19 CAR T-cells or anti-CD19 CAR T-cells alone, with subsequent evaluation of therapeutic response and treatment-related toxicities. At the data cutoff date, 7 patients were enrolled in our study, and all patients achieved response based on the International Myeloma Working Group Uniform Response Criteria. Six patients achieved stringent complete remission (sCR) within 60 days after CAR T-cell infusion (median time 58 days, range 18 to 90 days), and 1 patient with extramedullary disease achieved minimal response (MR) at 30 days after infusion. Bone marrow minimal residual disease (MRD) negativity was achieved in all patients, and the median time to achieve MRD negativity was 22 days (range 14 to 60 days). The most common grade 3 to 4 treatment-related toxicities were hematological toxicities. All patients experienced cytokine release syndrome (CRS), although CAR T-cell-related neurotoxicity was not observed. In our study, CAR T-cell therapy showed encouraging efficacy in the patients with R/R IgD MM, achieving high rates of sCR and MRD negativity. Aside from CRS and prolonged hematologic toxicities, other adverse reactions were mild, suggesting that this is a well-tolerated treatment with a high therapeutic potential.