Fig. 6

EP-1215 enhances the efficacy of immune checkpoint inhibitors in humanized CD34⁺ mouse models. a Docking pose of VK-1850 within the catalytic pocket of EBNA1 (PDB: 6NPP). b The binding mode of VK-1850 in the EBNA1 catalytic pocket. c Two-dimensional docking fitting diagram of VK-1850 at the EBNA1 binding site. d Design strategy for EBNA1 PROTACs. e HEK293FT cells overexpressing EBNA1-FLAG or EBNA1 were treated with five different EBNA1 degraders at varying concentrations for 72 h, and the degradation levels were assessed via western blotting. f EBNA1(labeled with GFP)-overexpressing HK1 cells were cocultured with T cells, and the therapeutic effects of EP-1215, αPD-1 monotherapy, or a combination of EP-1215 and αPD-1 treatment were evaluated. g Workflow for establishing the CD34⁺ humanized mouse model. The mouse diagram was created via FigDraw. h Xenograft tumors were established with HK1 control and EBNA1-overexpressing HK1 cells in CD34⁺ humanized mice. The mice were treated with DMSO, αPD-1, EP-1215, or αPD-1 combined with EP-1215. The mouse diagram was created via FigDraw. Representative images of xenograft tumors from different treatment groups are shown (n = 5 mice per group). i, j Tumor volume and tumor weight of the mice shown in (g) (n = 5 mice per group). k Survival analyses of the mice shown in (g) (n = 5 mice per group). l, m Representative IF images showing the characteristics of CD8⁺ T cells (green) and EBNA1 expression (red) in tumor cells following αPD-1 monotherapy or a combination of αPD-1 and EP-1215 treatment. The cell nuclei were stained with DAPI (blue). Scale bar: 200 µm. (n = 5 mice per group). f, i Data are shown as the mean ± s.e.m. f, i, j, m Two-way ANOVA with Tukey’s test for multiple comparisons. k Log-rank test. *P < 0.05;**P < 0.01; ***P < 0.001; ns, not significant. e, f Results are representative of three independent experiments