Enhanced CAR-T Function and Mitochondrial Fitness from Earlier Unfractionated Stem Cell Product in Multiple Myeloma.

Chimeric antigen receptor T-cells (CAR-T) targeting B-Cell Maturation Antigen (BCMA) have changed the treatment landscape for patients with relapsed and refractory multiple myeloma. However, T-cell dysfunction associated with progressive disease and multiple prior lines of therapy (PLOT) raises concerns about the feasibility of consistently manufacturing effective CAR-T cells. We investigated the practicality of utilizing previously cryopreserved mobilized apheresis to generate potent anti-BCMA CAR-T cells. Paired patient samples collected longitudinally from: 1) Mobilized, unfractionated apheresis obtained prior to hematopoietic cell transplantation (mobHCT), and 2) Apheresis obtained for commercial CAR-T manufacture (aphCAR) were directly compared head-to-head. Median time from transplant to commercial CAR-T infusion was 4.2 years (range 2.5-12.5), and prior to CAR-T collection all patients were triple-class exposed. Analysis revealed that mobHCT samples exhibited a higher CD4:CD8 ratio and a greater proportion of naïve T-cells (CCR7+CD45RO-) in both CD4 and CD8 compartments compared to aphCAR samples. CAR-T cells derived from mobHCT samples demonstrated superior expansion during manufacturing, enhanced interleukin-2 secretion, reduced expression of checkpoint inhibitors, improved cytotoxicity through multiple stimulation rounds, and enhanced mitochondrial function. These findings underscore the potential of utilizing cryopreserved mobilized apheresis collected earlier in the disease course to produce potent and metabolically robust CAR-T cells.