Abstract GD2 is a validated cancer immunotherapy target with a highly restricted normal tissue expression. Clinical GD2-CAR-T cell therapy is active in high GD2-expressing pediatric diffuse midline glioma and neuroblastoma. We initiated the KARPOS phase 1 clinical trial of escalating doses of intravenously administered autologous GD2-CAR-T cells in adult patients with recurrent glioblastoma at Royal Adelaide Hospital (www. anzctr. org. au - ACTRN12622001514796). Study Objectives: Primary: (i) establish feasibility of CAR-T manufacture; (ii) determine safety profile and dose limiting toxicities (DLTs) ; (iii) establish maximum tolerated dose. Secondary: (i) assess in vivo persistence and immunophenotype of CAR-T and associated serum cytokine profile, (ii) evaluate tumour responses, (iii) measure progression-free survival at 6 months (PFS6) and median overall survival (mOS). Exploratory: investigate in peripheral blood (PB) the activation and immunophenotype of CAR-T and myeloid cells, and PB cytokine and single cell mRNA sequencing (scRNAseq) profiles. Methodology: Patients were enrolled in a 3+3 dose-escalation design at: (i) Dose Level 0 (DL0) - 1x107 cells/m2 without prior lymphodepletion (LD) chemotherapy; (ii) DL1 - 1x107 cells/m2 with prior LD chemotherapy; and (iii) DL2 - 3x107 cells/m2 with prior LD chemotherapy. PB CAR-T were measured using quantitative DNA-PCR. Extent of PB CAR-T expansion was described using area under the curve (AUC) and peak expansion (Cmax). PB cell immunophenotyping was done by multi-colour flow cytometry. Cytokine profiles were generated using LegendPlex ELISA kits. Olink proteomics assays were used to measure PB analytes of immune interest. PARSE Evercode WT was used to generate and analyse PB cell scRNAseq data. Results: Eight patients were enrolled: 3 at each DL, with one patient re-enrolled at DL1. All planned CAR-T doses were manufactured except one patient required extra cells. No safety concerns were attributed to CAR-T. No DLTs were recorded. Cmax and AUC values were indistinguishable between dose cohorts. Three patients had repeat CAR-T infusions allowed because of stable or responding disease. Cmax and AUC values were lower than for first infusions. By RANO2. 0 criteria after the first infusion there were 3 cases of partial response, 4 stable disease, and 3 progressive disease on brain MR imaging. PFS6 was 33% and mOS was 8. 3 months. Many patients had baseline elevations in serum CCL2 and CXCL10, which may be myeloid- and/or tumour-derived. Most patients had significant post-infusion rises in serum cytokines with some instances of effector-related cytokines, but most reflected probable regulatory cytokine responses made by myeloid and tumour cells. Post-infusion increases in PB myeloid-derived suppressor cell numbers were seen in most patients. Conclusions: GD2-CAR-T cell therapy was feasible and safe. CAR-T expanded even without LD chemotherapy. Limited clinical activity was observed with evidence of transient tumour stabilisation. CAR-T activation was associated with evidence of a cytokine-driven myeloid cell reaction that may ultimately limit CAR-T activity. In the next patient cohorts, we will investigate intracerebroventricular CAR-T injections and attempt pharmacologic interruption of the myeloid cell reaction. Citation Format: Michael P. Brown, Abbey Le Blanc, Sidra Khan, Sandy Patel, Jesikah Logan, Olivia Franze, Erica C. Yeo, Nga T. Truong, Tessa Gargett. Initial clinical and laboratory results of an ongoing dose escalation study of autologous GD2-CAR-T cells in patients with recurrent GD2-positive glioblastoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86 (8Suppl): Abstract nr CT070.
Brown et al. (Fri,) studied this question.