Background: No standard-of-care treatment was established for recurrent high-grade gliomas (rHGGs) yet. Intrathecal infusion of autologous chimeric antigen receptor-T (CAR-T) cells has displayed potent anti-tumor activity in one patient (Brown et al. N Engl J Med 2016). We evaluated the safety, efficacy, pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of B7H3-specific allogeneic universal CAR-T (B7H3 UCAR-T) cells in patients with rHGGs. Methods: Eligible patients who had received standard treatment for newly-diagnosed high-grade gliomas but failed were treated with 2.5×10⁷ B7H3 UCAR-T cells via intra-lumbar injection every month. Eligibility criteria included histologic and/or cytologic rHGGs, B7H3-positive antigen expression rate of >50% in tumor tissue and Karnofsky performance status (KPS) ≥ 40. The primary endpoint was treatment-related adverse events (TAEs); secondary endpoints include overall survival (OS) and objective response rate (ORR); exploratory endpoints were PK and PD characteristics of B7H3 UCAR-T cells. Results: In the 7 patients enrolled, 4 (57.1%) were female, 5 (71.4%) glioblastoma (WHO Grade IV) and 2 (28.6%) diffuse midline glioma (WHO Grade IV), and the mean age was 40.4 years. The most common reported TAEs were increased cerebrospinal fluid (CSF) IL-6 (7/7, 100%), headache (7/7, 100%), increased blood IL-6 (6/7, 86%) and fever (6/7, 86%). No adverse events of grade 3 or greater related to B7H3 UCAR-T cells were reported. All the adverse events recovered or relieved after treatment. No typical or severe systemic cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS) or graft versus host disease (GvHD) were observed during the study period. Based on Immunotherapy Response Assessment in Neuro-Oncology (iRANO), 3 of 7 patients had response to therapy (42.9%; 95% CI: 15.8 to 75.0) and 7 of 7 patients were stable disease (100%; 95% CI: 64.6 to 100). As of cutoff date (January 30, 2023), two patients died. The median OS was not reached (95% CI: 12.9 to could not be estimated). The median follow-up for OS was 15.6 months (95% CI: 14.7 to 16.1). OS rate at 12 months was 85.7% (95% CI: 48.7 to 97.4). The CAR DNA copy numbers increased 1 day after each administration and persist at least 1 month in cerebrospinal fluid. IL-6 concentrations in CSF and peripheral blood increased after each administration while the change and concentration values in peripheral blood were much lower than those in CSF. Conclusions: In patients with rHGGs, B7H3 UCAR-T cells was not associated with any toxic effects of grade 3 or higher. B7H3 UCAR-T cells resulted in a significantly longer overall survival and a higher objective response rate than history data. B7H3 UCAR-T cells persist well in patients. Clinical trial information: ChiCTR2100047968.