IMMU-38. Single-cell RNA sequencing of cerebrospinal fluid in CARv3-TEAM-E treated glioblastoma

Abstract Glioblastoma is a highly aggressive primary brain tumor in adults with limited treatment options. Although there has been continuing interest in employing the immune system to combat this disease, monoclonal antibody therapies, such as checkpoint modulating agents, have yet to demonstrate clinically transformative outcomes. Conversely, adoptive cell therapies including chimeric antigen receptor (CAR)-T cell therapies have shown early indications of efficacy in select GBM patients. In a recent report, a first-in-human trial of CARv3-TEAM-E T cells engineered to target the epidermal growth factor receptor variant III tumor-specific antigen (EGFRvIII) as well as wild-type EGFR through secretion of a T-cell-engaging antibody molecule (TEAM) demonstrated preliminary evidence of CAR activity. We now report the findings of single-cell RNA sequencing (scRNA-seq) of cells isolated from the cerebrospinal fluid (CSF) of CARv3-TEAM-E treated GBM patients. Longitudinal CSF sampling in these patients was performed through an Ommaya reservoir. Using scRNA-seq, we demonstrate the ability to detect transduced CARv3-TEAM-E expressing T cells in the CSF from these patients. In this cohort, we assess the expression of cytotoxic effector gene expression programs over the course of longitudinal sampling. Unsupervised analysis shows promising early evidence of the expression of these cytotoxic effector gene expression programs. We further compare expression signatures in the CSF-sampled T cells to those present in the CARv3-TEAM-E infusion products. In summary, our results elucidate the longitudinal dynamics of T cell gene expression programs in the setting of this first-in-human trial of CARv3-TEAM-E T cells in GBM patients.