iC9-CAR.CSPG4 CAR-T Cells for Head and Neck Squamous Cell Carcinoma - PROJECT SUMMARY AND ABSTRACT Following treatment with platinum-doublet cytotoxic chemotherapy and a PD1 inhibitor, treatment options for recurrent/metastatic (incurable) HNSCC are limited in efficacy. CSPG4 is a cell surface proteoglycan that we and others have shown to be highly overexpressed in HNSCC. We developed a CAR-T encoding the CD28 endodomain and have shown in vitro and in vivo activity. We now propose to conduct a phase I, single center, open-label study in adult patients with HNSCC that is platinum and PD1 refractory. We propose a modified 3+3 design with doses of 5 × 105, 1 x 106 and 5 x 106 cells followed by a dose expansion cohort of 9 more patients at dose to better characterize safety, to provide pilot data on efficacy, and to provide samples for correlative analysis. To fully characterize the impact of CAR-T on both tumors and T cells, we will collect pre- and post- treatment biopsies as well as serial blood samples. We will model changes in both the CAR-T cells and non-CAR T cells through qPCR, flow cytometry for markers of exhaustion (CD57, PD1, LAG-3), metabolomic profile, and stemness. We will utilize TCR-seq to demonstrate the clonality of non-CAR T cells in tumor, comparing pre-treatment biopsy to post- treatment biopsy as well as to blood at serial time points. Further, we seek to study how to overcome tumor escape mediated by heterogeneity in CSPG4 expression. We have reported a bystander mechanism of tumor killing by CAR-Ts associated with CD95 expression in tumor cells and Fas-L expression by activated CAR-Ts and observed that TNFα released by CSPG4.CAR-Ts upon antigen engagement induces the upregulation of CSPG4 in tumor cells. We will assess CSPG4, CD95 and TNFα expression and co-localization. Finally, we will discover the extent to which iC9.CSPG4.CAR-T cell therapy induces epitope spreading in treated patients, including analysis of T cell responses to the full landscape of HPV antigens and neoantigens. This will both increase our understanding of mechanisms of CAR-T efficacy and provide rationale for combination of CAR-T therapy with T cell antigen-directed therapy (e.g. therapeutic neoantigen vaccination and/or TCR-T therapy).
