Figure 1.

ABL501 augments effector T cell activation by the inhibition of both LAG-3 and PD-L1 axes

(A) Schematic of LAG-3xPD-L1 BsAb, ABL501. (B) FACS analysis of ABL501 or anti-LAG-3 binding to LAG-3 and PD-1 expressing Jurkat cells (left panel) is shown (ABL501: half-maximal effective concentration [EC₅₀] = 0.15 nM; anti-LAG-3: EC₅₀ = 0.16 nM). FACS analysis of ABL501 or anti-PD-L1 binding to endogenously PD-L1 expressing SNU-324 cells (right panel) is shown (ABL501: EC₅₀ = 0.87 nM; anti-PD-L1: EC₅₀ = 0.36 nM). (C) LAG-3 and PD-1 expressing NF-κB-Luc2 reporter Jurkat cells were co-incubated with target cells expressing MHC-II and PD-L1 in the presence of the indicated antibodies at various concentrations. Blocking activity was analyzed by measuring luminance of the downstream NF-κB reporter (ABL501: EC₅₀ = 1.78 nM, Combi: EC₅₀ = 0.7 nM, and anti-PD-L1: EC₅₀ = 0.53 nM). (D and E) CD4⁺ T or CD8⁺ T cells isolated from PBMCs were co-cultured with allogeneic mo-DCs in the presence of the indicated antibodies at various concentrations for 5 days. (D) Schematic illustration of mixed lymphocyte reaction (MLR) assay (left panel) is shown. FACS analysis shows CTV dilution of CD4⁺ and CD8⁺ T cells with the indicated antibodies at a final concentration of 33.4 nM. Representative FACS plots (above) and a summary plot (below) show the percentages of CTV_low CD4⁺ and CD8⁺ T cells. Each dot represents an individual human sample. (E) ELISA of IFN-γ secretion by CD4⁺ T cells (left; ABL501: EC₅₀ = 7.27 nM, Combi: EC₅₀ = 10.78 nM, anti-PD-L1: EC₅₀ = 14.9 nM, and anti-LAG-3: EC₅₀ = 14.07 nM) or by CD8⁺ T cells (right; ABL501: EC₅₀ = 7.99 nM, Combi: EC₅₀ = 13.61 nM, anti-PD-L1: EC₅₀ = 18.04 nM, and anti-LAG-3: EC₅₀ = 26.28 nM). Data were compiled from three to five independent experiments with two replications. Statistical significance was determined by one-way ANOVA with Holm-Sidak multiple comparisons. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001, and ns, not significant.