SURG-09. TARGETING A SHARED GLIOBLASTOMA CELL STATE THROUGH ADAPTIVE NATURAL KILLER CELLS AUGMENTED WITH TRISPECIFIC KILLER CELL ENGAGER (TRIKE) IMMUNE-MODULATOR AGAINST CD276

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Abstract INTRODUCTION T and NK (Natural Killer) cells have emerged as promising platforms for immunotherapy. While T cells require antigen priming and complex MHC-dependent interactions, NK cells exhibit limited persistence and limited antigen specificity. Trispecific Killer cell Engagers (TriKEs) are constructs developed to address these limitations, combining interleukin 15 (IL15, to enhance persistence), a single-chain antibody fragment against CD16 (to immune-activate NK), and a second fragment targeting a tumor surface marker. Objective: In this study, we identified CD276 (B7H3) as the surface marker optimal for an anti-glioblastoma TriKE and tested its effect on the anti-glioblastoma activity of NK cells. Method: Mass-spectrometry, RNA-Seq, and single cell RNA-Seq profiling of glioblastoma lines. Laboratory characterization and murine modeling Result: Orthogonal analysis of mass-spec identified cell surface molecules enriched in glioblastoma lines and RNA-seq of lines with defined sensitivity to NK cells identified surface proteins highly expressed in NK-resistant lines. Screening of these candidates for genes that showed poor survival association using the TCGA identified CD276. qPCR analysis confirmed higher CD276 expression in the NK-resistant lines, though expression is also detected in NK-sensitive glioblastoma lines. Western blotting analysis and TCGA analysis showed higher level CD276 expression in all glioblastoma subtypes (proneural, neural, mesenchymal, and classical) relative to normal brain. Single cell RNA-Seq of clinical specimens confirmed high expression of CD276 in glioblastoma cells in OPC-like, NPC-like, AC-like, and MES-like cell states. Co-incubation of a IL15, CD16, and CD276 targeting TriKE with either adaptive or iPS derived NK cells enhanced anti-glioblastoma cytotoxicity against cells otherwise refractory to NK treatment in vitro. Synergy between these reagents were also observed in vivo upon orthotopic injection. CONCLUSION Our results suggest that a therapeutic strategy combining intra-tumoral injections of NK cells and a B7H3 specific TriKE holds promise and warrants clinical trial consideration.