Introduction/Background The observed clinical benefit of immunotherapy in EOC is limited. During cancer progression, tumor-specific T cells display increased expression of inhibitory receptors (IRs), causing their functional exhaustion. We hypothesize that protecting tumor-specific T cells from immunosuppression by gene editing approaches aimed at reducing IRs expression might maximize their therapeutic potential.

Methodology We characterized by flow cytometry EOC cell lines and patients’ ascites-derived primary cultures (PC) to evaluate their expression of selected tumor-associated antigens and IR ligands. Considering antigen expression, we selected a HLA-A*02:01-restricted WT1-specific TCR from our library (HD1-TCR) and tested different T-cell products engineered to express HD1-TCR and also harboring gene disruption ( HD1-IRKO) of distinct IRs (2B4, TIM3, LAG3).

To functionally characterize the putative advantage provided by IR disruption on the anti-tumor efficacy of engineered T cells, HD1-TCR and HD1-IRKO gene-edited T cells were challenged with WT-1pos HLA-A*02:01pos (or HLA-A*02:01neg, as control) cancer cell lines, PC and tumor derived organoids (PDOs). We evaluated cytokine secretion, T cell activation and apoptosis.

Results We observed high expression of WT-1 while IR ligands (IR-L) were expressed by a low percentage of tumor cells and increased by IFNγ exposure. After co-culture with tumor cells, the different T-cell products displayed similar killing of cell lines, while increased killing was observed with HD1-IRKO cells against EOC primary cultures expressing IR-Ls. In particular, TIM-3KO HD1-TCR edited T cells displayed more potent killing of PC expressing TIM-3 IR ligands compared to the other T cell products. Additionally, upon co-culture with HLA-matched PDOs, both TIM-3KO and LAG-3KO HD1-TCR T cells showed an increased induction of cancer cell apoptosis compared to IR-competent cells.

Conclusion HD1-IRKO T-cell products appear superior to HD1-TCR IR-competent counterparts in killing WT-1pos HLA-A*02:01 cancer cells. The most consistent advantages were observed with TIM-3KO HD1-TCR.

Disclosures Receipt of grants/research supports from Intellia Therapeutics.

Receipt of grants/research supports from GSK, MSD/Astrazeneca, Pharmamar