CTIM-40. EARLY RADIOGRAPHIC RESPONSE AND ENGRAFTMENT OF PHASE I FIRST-IN-HUMAN BICISTRONIC CAR T CELLS CORRELATE WITH REAL-TIME AUTOLOGOUS GBM ORGANOID CYTOLYSIS

Abstract

Abstract Glioblastoma (GBM) is a highly treatment-resistant cancer, in part due to prominent inter- and intratumoral heterogeneity. To date, monovalent CAR T-cell therapies have failed to overcome this heterogeneity. Bivalent CAR-T cells may overcome this challenge by expanding the population of target-positive tumor cells. NCT05168423 is first-in-human, phase 1 dose escalation study to assess safety and feasibility of intrathecal delivery of autologous bicistronic CAR-T cells, targeting both EGFR and IL13Rα2, in patients with EGFR-amplified recurrent GBM. For each patient enrolled in this study, high-fidelity glioblastoma organoids (GBOs) are derived from tumor tissue and utilized to test the autologous CAR-T product in real-time. GBOs are co-cultured with autologous CAR-T cells and individually monitored using modified impedance spectroscopy assays over six days for quantification of real-time tumor cytolysis. CAR-T efficacy in GBOs was correlated to matched clinical trial patient outcomes, including CAR-T engraftment. To date, three patients have been treated at the initial dose level (10,000,000 CART-EGFR-IL13Rα2 cells). All three patients demonstrated tumor shrinkage on MRI obtained within 24-48hrs post-infusion. MRI changes were accompanied by significant tumor-inflammation associated neurotoxicity that resolved with steroids and IL1R blockade. Serial CSF collection for qPCR following CAR-T infusion revealed average peaks of >100,000 copies of CAR-T cells/μg of gDNA, comparable to CART19-treated patients. Cytotoxicity values in GBOs strongly correlated with peak CSF engraftment levels of CAR-T cells in all three patients (r = 0.998, p = 0.037). In summary, we present striking radiographic and biological responses from the first cohort of recurrent GBM patients treated with a bivalent, intrathecally delivered CAR T cell product simultaneously targeting EGFR and IL13Rα2. Potent anti-tumor activity of CART-EGFR-IL13Rα2 cells was also observed by treating patient-derived GBOs with the patients’ corresponding autologous CAR T-cell products, providing a parallel, ex vivo system for real-time prediction of CAR T-cell engraftment.