CTIM-15. T CELL RESPONSE DYNAMICS IN PHASE 3 GLIOBLASTOMA PATIENTS IMMUNIZED WITH AUTOLOGOUS DENDRITIC CELLS PULSED WITH AUTOLOGOUS TUMOR CELL LYSATE

Abstract BACKGROUND 331 glioblastoma patients were immunized with autologous dendritic cells (DCs) pulsed with autologous tumor cell lysate or placebo in a Phase 3 clinical trial. Immunization with the pulsed DCs was associated with extended overall survival in both newly diagnosed and recurrent disease. Objective: To characterize T cell responses and T cell response dynamics in patients immunized with autologous dendritic cells pulsed with autologous tumor cell lysate. METHODS we performed T cell receptor sequencing on peripheral blood mononuclear cells from both newly diagnosed and recurrent glioblastoma patients that were treated with the pulsed DCs. Timepoints from both before and after immunization were compared to understand T cell response dynamics. RESULTS Expansion of several hundred new T cell clones as well as more than 700 previously detected T cell clones was detected over time in both newly diagnosed and recurrent GBM patients who were treated with the pulsed DCs. Investigation of the dynamics of the response demonstrated that further expansion was triggered by ongoing immunizations. Correlations between T cell response data and clinical outcomes are ongoing. CONCLUSION Immunization with autologous DCs pulsed with autologous tumor cell lysate induces broad spectrum immune responses in patients with glioblastoma.