Abstract 271: Targeting PD-1, TIM-3 and LAG-3 in combination for improved immunotherapy combinations

Abstract

Abstract Antibodies that inhibit the CTLA-4 and PD-1 checkpoint pathways have shown significant activity as either single agents or in combination in both mouse models and clinical studies. TIM-3 and LAG-3 have been reported to function as additional immune checkpoints which limit anti-tumor T cell responses and represent an opportunity for additional combination approaches to improve patient response to immunotherapy. To explore the potential for targeting other immune checkpoints in combination with anti-PD-1, studies were conducted in syngeneic mouse models and in human in vitro assays. A series of surrogate mouse specific reagents targeting TIM-3, LAG-3 and PD-1 have been generated to improve understanding of combination checkpoint therapy in several syngeneic models. Mouse tumor models were characterized by IHC and FACS for relevant markers including PD-L1, Foxp3, TIM3and LAG3, to identify those most likely to be subject to immunosuppressive mechanisms contributing to tumor growth and immune evasion. Initial syngeneic studies in MC38 and Colon 26 demonstrated that combinations of antibodies to murine PD-1, TIM-3 and LAG-3 improved efficacy over single agent therapy, suggesting that combinations of these checkpoint inhibitors might have therapeutic potential in the clinic. The results of ongoing studies to evaluate the dose response of the combinations as well as the contribution of the antibody isotype will be reported. Potent anti-human PD-1, -TIM-3 and LAG-3 clinical candidates have been identified using SHM-XEL™, which combines mammalian cell display of human IgG with somatic hypermutation in vitro to select and mature antibodies with desired biological activities. In a DC/T cell MLR assay, combination of the anti-LAG-3 antibody with a novel anti-PD-1 antibody could further increase T cell secretion of IL-2 up to 30-fold compared to anti-LAG-3 alone. Anti-TIM-3 in combination with anti-PD-1 also improved the EC50 up to 6-fold. Staining of activated purified CD4+ or CD8+ T-cells demonstrate that co-expression of PD-1 and LAG-3 increases upon activation compared to naïve T-cells, suggesting combination therapy may be particularly effective against activated or exhausted T-cells. These in vitro data and in vivo pre-clinical model results support evaluating combination immunotherapy with anti-LAG-3, anti-TIM-3, and anti-PD-1 in cancer patients. Citation Format: Marilyn Kehry, Robert Horlick, Peter Bowers, Toni Jun, Jean da Silva Correia, Jonathan Graves, Yan Wang, Haley Laken, David J. King. Targeting PD-1, TIM-3 and LAG-3 in combination for improved immunotherapy combinations. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 271. doi:10.1158/1538-7445.AM2015-271