Post-infusion PD-1+CD8+CAR-T cells identify patients responsive to CD19-CAR-T therapy in non-Hodgkin's lymphoma

• After CAR-T infusion, circulating PD-1+CAR+CD8+ T cells are highly associated with response to CAR-T cell therapy for Non-Hodgkin's Lymphoma

• Spectral flow analysis reveals specific populations of stem-like and effector-like CAR-T cells which correlate with improved outcomes

Chimeric antigen receptor T cell therapy (CAR-T) has revolutionized treatment for relapsed/refractory (r/r) B-cell non-Hodgkin's lymphoma (NHL). Robust biomarkers and a complete understanding of CAR-T cell function in the post-infusion phase remain limited. Here we used a 37-color spectral flow cytometry panel to perform high dimensional single cell analysis of post-infusion samples in 26 patients treated with CD28 co-stimulatory domain containing commercial CAR-T (CD28-CAR-T) for NHL and focused on computationally gated CD8+ CAR-T cells. We found that the presence of post-infusion PD-1+ CD8+ CAR-T cells at the Day 14 timepoint 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+ TCF1+ stem-like CAR-T cells and PD-1+ 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 and highlight the importance of PD-1 positivity in CD8+ CAR-T cells post-infusion in achieving CR.