IMMU-29. LAG-3 COMPENSATES TIM-3 DOWN-REGULATION IN A HUMAN GLIOBLASTOMA MODEL

Abstract INTRODUCTION There are a few alternatives treatments beside the standard care for glioblastomas, one of them is adoptive cell therapy; our group has shown promising preliminary results with a dendritic cell-based vaccine that has being tested in first-in-human clinical trials. Checkpoint inhibitors have also shown promising results in the cancer arena, but not for brain tumors. OBJECTIVE We have assessed whether combination of checkpoint inhibition and transferred cellular therapy may enhance anti-tumor killing of adoptive T-cell therapies to improve survival in GBM patients. METHODS PBMCs were isolated from CMV+ donors, in order to generate dendritic cells and pulsed them with CMVpp65-mRNA. DCs were co-culture with T-cells for 15-days. Five groups were made (Tim3 at 300 ug/ml, PD1, Tim3, PD1+Tim3 at 10 ug/ml and PD1+Tim3 at 3 ug/ml) and their respective isotype-control groups. IL2 was added at 100UI/ml every 3 days as well as the blockade. Phenotyping was performed on Day0 and Day15th. Restimulation was made with pp65-pepmixes and UPGL a glioblastoma cell-line created by our group. Supernatant from overnight restimulation was analyzed for 10-cytokines. RESULTS PD1/Tim3 condition (3ug/ml), Lag3 expression was increased in central memory T-cells (mean 19.13% vs 30.98% p=0.02). On EM T-cells, Lag3 expression increased (57.98% vs 75.83%; p=0.03); for control vs 10ug/ml from combination checkpoint treatment group. On EMRA T-cells, the results were similar, Lag3 was upregulated in response of low-doses of double checkpoint inhibitor combination (8% vs 21% p=0.002). At increased doses (Tim3 at 300ug/ml), secretion of IFN-□ was reduced in T-cells treated with Tim3 vs relevant control. Secretion of IL-12 in treated T-cells with PD1/Tim3 was significantly increased. IL-1□ secretion was significantly lower in the PD1/Tim3 (10ug/ml) treatment-group compared with control-group (p < 0.004). CONCLUSIONS We have identified a potential activation component and dependent pathway between Tim3 and Lag3, once Tim3 and PD1 are blockade.