Raje, Noopur S.

Abstract Improved understanding of how chimeric antigen receptor (CAR) and endogenous T‐cell phenotypes associate with progression‐free survival (PFS) is needed to individualize and improve immunotherapy outcomes in multiple myeloma (MM). We characterized and investigated the prognostic value of immune dynamics defined with multidimensional and computational flow cytometry in 258 bone marrow aspirates from 107 MM patients treated with idecabtagene vicleucel in the KarMMa trial. At screening, there was an association between longer PFS and increased percentages of PD1 + cytotoxic T cells and ICOS − TIGIT + Tregs. At Month 1 after infusion, the presence of >1% CAR‐T cells, a CD4/CD8 CAR‐T‐cell ratio >0.09, and greater abundance of non‐activated non‐cytolytic CAR‐T cells identified patients with longer PFS. Notably, 47 of the 115 endogenous T‐cell clusters were prognostic at the latest assessment performed after CAR‐T infusion. Lower percentages of ICOS + TIGIT − Tregs showed the strongest association with longer PFS. Altogether, this large dataset of dynamic immune profiling throughout treatment with anti‐B‐cell maturation antigen (anti‐BCMA) CAR‐T cells uncovered that the T‐cell composition prior to apheresis as well as CAR‐T and endogenous T‐cell phenotypes after infusion associates with PFS. These findings have potential for translation into routine laboratory practice for improved understanding of response and resistance to CAR‐T cells in relapsed/refractory MM.