413 Genetic deletion of TIGIT enhances CAR-NK cell function in the solid tumor microenvironment

Abstract

Background Natural killer cells (NKs) expressing chimeric antigen receptors (CAR-NKs) were successful in hematological malignancies. 1 However, solid tumors resist CAR-NKs via a tumor microenvironment (TME) that includes myeloid derived suppressor cells (MDSCs) and M2 macrophages (M2s). 2 We demonstrated that ex vivo manufacture of therapeutic CAR-NKs significantly upregulated T cell immunoreceptor with Ig and ITIM domains (TIGIT), an inhibitory NK receptor. Analysis of pediatric neuroblastoma and sarcoma patient tumors confirmed high expression of TIGIT ligands on tumor cells and intra-tumoral MDSCs and M2s. Our main objective was to determine influence of TIGIT on CAR-NK function in the TME. Current TIGIT-targeting approaches using antibodies are handicapped by poor bioavailability and transient binding in the TME. We hypothesized that genetic deletion of TIGIT on CAR-NKs will lead to a more profound and durable antitumor response within the TME. 3 Methods TIGIT knockout (KO) CAR-NKs expressing a GD2.4-1BB.zeta CAR were generated by concurrent CRISPR/ cas9 and retroviral transduction of expanded primary human NK cells. Degranulation (CD107a) and IFN-g by TIGIT KO . GD2.