Postinfusion PD-1⁺ CD8⁺ CAR T cells identify patients responsive to CD19 CAR T-cell therapy in non-Hodgkin lymphoma

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized treatment for relapsed/ refractory B-cell non-Hodgkin lymphoma (NHL). Robust biomarkers and a complete understanding of CAR T-cell function in the postinfusion phase remain limited. Here, we used a 37-color spectral flow cytometry panel to perform high dimensional single-cell analysis of postinfusion samples in 26 patients treated with CD28 costimulatory domain containing commercial CAR T cells for NHL and focused on computationally gated CD8⁺ CAR T cells. We found that the presence of postinfusion Programmed cell death protein 1 (PD-1)⁺ CD8⁺ CAR T cells at the day 14 time point highly correlated with the ability to achieve complete response (CR) by 6 months. Further analysis identified multiple subtypes of CD8⁺ PD-1⁺ CAR T cells, including PD-1⁺ T cell factor 1 (TCF1)⁺ stem-like CAR T cells and PD-1⁺ T-cell immunoglobulin and mucin-domain containing-3 (TIM3)⁺ effector-like CAR T cells that correlated with improved clinical outcomes such as response and progression-free survival. Additionally, we identified a subset of PD-1⁺ CD8⁺ CAR⁺ T cells with effector-like function that was increased in patients who achieved a CR and was associated with grade 3 or higher immune effector cell–associated neurotoxicity syndrome. Here, we identified robust biomarkers of response to CD28 CAR T cells and highlight the importance of PD-1 positivity in CD8⁺ CAR T cells after infusion in achieving CR.