Figure 8.

The PBMC + aT PDX model demonstrates the activity of a CD19xTcR-specific DART. (A) Mice (n = 15) were injected with 0.5 × 10⁶ anti-CD3/28 + IL-2 pre-activated CLL-derived T cells and 20 × 10⁶ CLL PBMCs on Day 0. Expansion of both T and B cells was determined 25 days post transfer by detection of human IFNγ, and human IgG in murine plasma samples. DART bispecific antibodies (DART molecule, n = 4 animals; or DART control molecule, n = 4 animals) or saline were administered ip from Day 30 to Day 34. Plasma levels of human IFNγ and IgG were further determined at day 46 when euthanasia was performed. Animals with <10 pg/ml IFNγ at Day 25 were excluded from receiving DARTs and were not included in the analysis making 3 groups of 4 animals for each condition. (B) Plasma levels of IFNγ and IgG in the 3 groups of animals (n = 12, 4 per group), taken pre-DART injection at Day 25 and at euthanasia at Day 40. Results show no significant differences in IFNγ levels between the 3 groups before DART molecule injection and at euthanasia. In contrast, plasma Ig levels are significantly lower in CD19xTcR DART-treated animals (red dots), compared to the DART control molecule-treated control animals (blue dots). * corresponds to Kruskal-Wallis test P value < 0.05. (C) FC reveals absence of CD5⁺CD19⁺ cells in DART molecule-treated animals. Illustrative FC plots are representative of hCD45 single cell splenic suspensions obtained at euthanasia. Graph shows median CD5⁺CD19⁺ cells in each group as a percentage of total hCD45⁺ cells isolated. Compared to DART control molecule-treated control animals (blue dots), there are significantly fewer CD5⁺CD19⁺ cells in DART molecule-treated animals (red dots). * corresponds to Kruskal-Wallis test P value < 0.05. (D) Representative IHC (x20 original magnification) of DART control molecule-treated animals (upper panel) compared to DART molecule-treated animals (lower panel). These results were apparent for both a U-CLL1539 (illustrated in Figure) and M-CLL0545.