Oral Presentation ISCT ANZ - BAA Joint Scientific Meeting 2022

In vitro studies in support of GD2-specific CAR-T cell therapy for aggressive adult and pediatric brain tumors (80462)

Tessa Gargett 1 2 3 , Lisa Ebert 2 , Nga Truong 2 , Kristyna Sedivakova 2 , Paris Kollis 2 , Orazio Vittorio 4 , David Ziegler 4 , Michael Brown 1 2 3
  1. Royal Adelaide Hospital, Adelaide, South Australia, Australia
  2. Translational Oncology Laboratory, Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA
  3. Department of Medicine, University of Adelaide, Adelaide, South Australia, Australia
  4. Children's Cancer Insititue, Sydney Children's Hospital, Sydney, NSW, Australia

Glioblastoma multiforme (GBM) is the commonest, most lethal adult primary brain cancer. Aggressive treatment with surgery and chemoradiotherapy has barely shifted 5-year survival rates of 4%. Similarly, the commonest childhood brain cancer is diffuse intrinsic pontine glioma (DIPG) with median survival of ~9 months; < 1% of patients survive 5 years. Only radiotherapy is used to palliate symptoms, and modestly prolongs survival. Transformative CD19-CAR-T cell therapy for relapsed/refractory B-cell cancer patients, and early-phase CAR-T cell clinical data in adult GBM patients, suggest that CAR-T cell therapy is promising when immune checkpoint inhibitors benefit > 5% of GBM patients.

Based on our experience with GD2-CAR-T cell therapy in patients with GD2-positive cancers, we aimed to evaluate GD2 tumor antigen expression in primary human tissues, assess the feasibility of CAR-T cell manufacture from patients’ peripheral blood. Using fresh frozen glioblastoma taken at surgery and patient-derived glioma neural stem (GNS) lines, we used immunofluorescence to profile GD2 expression in GBM and DIPG using the same 14g2a antibody from which the GD2-CAR derives. We found uniformly GD2 expression high levels in GBM (n=16) with variable levels of expression in different tumor regions and low-level expression in non-tumor regions. GNS cells were also highly GD2-positive (17 of 20 lines). Others report very high GD2 expression in DIPG. In 4 biopsy and 4 autopsy samples, we confirmed enhanced GD2 expression in H3K27M mutated DIPG. GD2-CAR-T cells can be manufactured from patient-derived T cells despite evident T-cell immunophenotypic abnormalities in starting material. Protocol-defined batch release criteria were met for each of 6 selected patients although cell expansion rates lagged. GD2-specific CAR-T cells demonstrated potent effector function in vitro. Moreover, killing was achieved at low effector: target ratios of 1 CAR-T cell to 10 tumour cells, indicating serial killing or a bystander killing effect. Stimulated CAR-T cells also secreted multiple effector cytokines including IFNγ, TNFα and IL-2. We provide in vitro validation of GD2 as a promising CAR-T cell target in adult GBM and pediatric DIPG patients including effective killing of primary tumor cells.