Preclinical efficacy of combinatorial B7-H3 CAR T cells and ONC206 against diffuse intrinsic pontine glioma.

Background: Diffuse intrinsic pontine glioma (DIPG) is a fatal pediatric brain tumor affecting over 300 children annually in the United States. Chimeric antigen receptor (CAR) T cells are a targeted immune effector cell therapy with substantial clinical benefit against hematologic cancers. Against CNS tumors, CAR T cells targeting B7-H3, a protein highly expressed on DIPG, have rapidly advanced from preclinical studies to clinical trials. BrainChild-03 (NCT04185038), a phase 1 trial of repeatedly delivered intracerebroventricular (ICV) B7-H3-targeting CAR T cells (B7-H3 CAR T cells), demonstrated tolerability and potential efficacy for children and young adults with DIPG. However, clinical benefits were not uniformly seen, and multi-agent treatment strategies may be required against such an aggressive disease. Here, we combined B7-H3 CAR T cells with ONC206, an imipridone molecule also under clinical investigation. Methods: We tested B7-H3 CAR T cells combined with ONC206 across multiple DIPG cell cultures and orthotopic xenograft mouse models. Results: B7-H3 CAR T cell monotherapy induced robust cytotoxicity while ONC206 treatment resulted in significant mitochondrial dysfunction against DMG/DIPG cells. The combination of low effector-to-target ratios of B7-H3 CAR T cells and IC Conclusions: B7-H3 CAR T cells combined with ONC206 is a feasible and efficacious multi-agent approach against multiple DIPG models.