Intracerebroventricular B7-H3-targeting CAR T cells for non-pontine DMG and recurrent/refractory pediatric CNS tumors: a phase 1 trial

BACKGROUND: High-grade central nervous system (CNS) tumors carry a poor prognosis with limited curative options if first-line therapy fails. B7-H3 is expressed in many of these tumors, and chimeric antigen receptor (CAR) T cell therapy is an emerging immunotherapeutic strategy. METHODS: BrainChild-03 (NCT04185038) is a single-center, dose-escalation phase 1 study of repeated intracerebroventricular (ICV) B7-H3 CAR T cells in children and young adults with recurrent/refractory CNS tumors (Arms A, B) and diffuse intrinsic pontine glioma (DIPG, Arm C). Here, we report results from Arm B, in which patients with refractory/relapsed CNS tumors or pre- or post-progression non-pontine diffuse midline glioma (DMG) received repeated ICV infusions. Primary objectives were feasibility and safety/tolerability; secondary objectives included CAR T cell detection, disease response, and survival. RESULTS: Of 36 enrolled patients (atypical teratoid rhabdoid tumor n = 5, DMG n = 8, embryonal tumor with multilayer rosettes n = 2, ependymoma n = 4, high-grade glioma n = 6, medulloblastoma n = 8, pineoblastoma n = 3), manufacturing was successful for 35 patients, 26 of whom received therapy. Median age was 10 years (range 1-26). Dose escalation from 1 × 107 to 10 × 107 CAR T cells/dose identified this dose as the maximally tolerated dose regimen, with no dose-limiting toxicities observed. Across 181 total doses (median 7/patient), common adverse events included headache (n = 26), fever (n = 15), and nausea (n = 14). Median survival from first infusion was 11.5 months, ranging from 3.2 months (pineoblastoma, HGG) to 21.4 months (ependymoma); two patients achieved a partial response. CONCLUSIONS: Repeated ICV B7-H3 CAR T cell dosing is feasible and tolerable across a spectrum of pediatric CNS tumors, supporting continued investigation in future trials.