Rituximab pre-conditioning in a phase I study of CARv3-TEAM-E for recurrent glioblastoma (GBM): The INCIPIENT trial.

2059 Background: Chimeric Antigen Receptor (CAR) T cells for glioblastoma (GBM) have been limited by the challenge of targeting a single tumor antigen in a heterogeneous disease. To address this barrier, we generated a novel engineered T-cell product (CARv3-TEAM-E) that targets the EGFRvIII antigen while also secreting T-cell-Engaging Antibody Molecules (TEAMs) against wild-type EGFR. Methods: The INCIPIENT clinical trial is a first-in-human study of CARv3-TEAM-E in patients with GBM (NCT05660369). Patients with recurrent GBM were treated with intraventricular CARv3-TEAM-E T cells (10E6 cells per infusion) and one of three pre-treatment regimens: no lymphodepletion (N=3), lymphodepleting chemotherapy with cyclophosphamide and fludarabine (LDC) (N=7), or cyclophosphamide, fludarabine, and rituximab (LDC+R) (N=3). The primary objective was safety and tolerability. Immune cells were profiled in the cerebrospinal fluid (CSF) and peripheral blood by flow cytometry. Results: CAR T manufacturing was successful for all patients. There were no dose-limiting toxicities (DLT). Three patients were treated without LDC; all developed anti-CAR and/or anti-TEAM antibodies (i.e., anti-therapy antibodies) after a single infusion of CARv3-TEAM-E. Subsequently, 7 patients were treated with LDC prior to CARv3-TEAM-E, 5 of which underwent serial infusions (range 2-5 infusions). Four patients had reinfusions after which CAR T cells were not detected in the CSF. We therefore added rituximab to the LDC regimen. In the 3 individuals pre-treated with LDC+R, CAR T cells were detected in CSF not only after initial infusion (range 21-28 days) but also following repeat infusion in all patients (range 3-15 days post-reinfusion). Anti-therapy IgG was not detected in patients treated with LDC+R, as compared to 9/10 patients who developed an antibody response when rituximab was not administered. As of 12/15/2025, 10/13 patients are alive 6-30 months after first infusion, with 7 alive >14 months. Conclusions: Intraventricular CARv3-TEAM-E infusions were well-tolerated after LDC+R pre-conditioning and no DLTs were noted. The addition of Rituximab abrogated anti-therapy antibody formation and prolonged CAR T-cell persistence in 3/3 patients. Survival data reflect continued promise of CARv3-TEAM-E in patients with recurrent glioblastoma. Clinical trial information: NCT05660369 .