Induction of CD40 signaling and cell death by CD4 T-cell engagement with mosunetuzumab. (A) Schematic of the rationale for using mosunetuzumab to engage CD40 signaling in lymphoma B cells. (B) GSEA normalized enrichment scores (NES) of signatures induced by CD40L + IL-4, comparing CD4 T-cell engagement with mosunetuzumab (mosun). (C) Heat maps showing regions of significantly (FDR <0.05) increased CREBBP (left), EP300 (middle), and H3K27Ac (right) at 12 and 24 hours after CD4 T-cell engagement with mosunetuzumab compared with control. (D) Altuna plot of the overlap of regions shown in panel C. (E) Heat map of hGSEA FDR q-values for genes with increased H3K27Ac, CREBBP, or EP300 at 12 and 24 hours after CD4 T-cell engagement with mosunetuzumab compared with control. (F) Bubble plot of motif enrichment analysis (HOMER) for increased H3K27Ac at 12 and 24 hours after CD4 T-cell engagement with mosunetuzumab compared with control. (G) Cell viability of CREBBP R1446C or Y1503C mutant RL cells with (red) or without (blue) CD40 KO at different effector-to-target ratios of CD4 T cells to lymphoma cells with 100 ng/mL of mosunetuzumab. Student t test ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. (H) CD4 T-cell killing of CREBBP Y1503C mutant RL cells within mixed cultures of CD40-positive and CD40-negative cells. (I) Comparison of the relative fraction of CD40 WT and CD40 KO cells within mixed cultures at the start (day 0) and end (day 2) of cocultures with CD4 T cells plus mosunetuzumab.