IMMU-11. BRAINCHILD PIPELINE: LOCOREGIONAL IMMUNOTHERAPY WITH CHIMERIC ANTIGEN RECEPTOR (CAR) T-CELLS FOR RECURRENT/REFRACTORY CENTRAL NERVOUS SYSTEM TUMORS

Abstract

Chimeric antigen receptor (CAR) T-cell therapy carries the promise of a broadly applicable, targeted, yet molecular pathway-independent, intervention for pediatric central nervous system (CNS) tumors. The BrainChild pipeline at Seattle Children's utilizes engineered CAR T-cells directed against the surface epitopes HER2, EGFR, B7-H3 and IL13Ralpha2, which are commonly expressed in pediatric CNS tumors including high-grade glioma, diffuse intrinsic pontine glioma, medulloblastoma, and ependymoma. Using in vitro and in vivo preclinical modeling, we have optimized the efficacy and specificity of the CAR constructs. The extracellular target-specific scFv domain for the HER2-specific and EGFR-specific CARs are derived from trastuzumab and an EGFR806 antibody, respectively. Third-generation CAR T-cells with medium-length (HER2-CAR) and short (EGFR806-CAR) spacers coupled to an intracellular 4-1BBζ domain result in complete and durable tumor eradication in mouse xenograft CNS tumor models. We now are poised to begin enrolling Phase 1 clinical trials for children and young adults with recurrent or refractory CNS tumors expressing the respective target epitopes. We will deliver locoregional adoptive therapy with autologous CD4 and CD8 T cells lentivirally transduced with the optimized CAR constructs. Using a dose-escalation regimen, CAR T-cells will be injected on a weekly schedule via indwelling catheters into the tumor resection cavity or the ventricular system. The primary objectives are safety and feasibility, along with secondary and exploratory objectives to define the CAR T-cell distribution in the CSF and peripheral circulation, target epitope expression across tumor populations, progression free and overall survival, and biomarkers of anti-tumor CAR T-cell activity.