Epcoritamab induces autologous T-cell activation and expansion. Markers of T-cell activation and cytotoxic potential were assessed via flow cytometry, in PBMCs from patients who were TN (n = 7), IBR (n = 10), or ACA (n = 11) cultured with epcoritamab or B12 control for 3 days. Samples from RES (n = 7) were also included. (A) Heatmap depicts the median centered frequencies of CD4⁺ and CD8⁺ T cells expressing the indicated markers; samples were grouped based on hierarchical clustering. Comparison of CLL-specific killing after 3 and 7 days of treatment between grouping based on (B) CD4 activation and (C) CD8 activation state. Each symbol represents 1 patient sample, and the median and interquartile range are indicated. (D) CD4⁺ and CD8⁺ T-cell counts were quantified via flow cytometry after 7 days of culture with epcoritamab (blue symbols) or B12 control (red symbols). Each symbol represents 1 patient sample. Asterisks indicate statistical significance using Wilcoxon matched-pair signed rank test for comparison of different treatments applied to individual patient samples and Mann-Whitney test for comparison of different patient groups. ∗P < .05; ∗∗P < .001; ∗∗∗P< .001.