T-BsAb treatment demonstrated therapeutic efficacy against leukemia cells expressing the corresponding human antigens in huCD3-Tg mice. (A) huCD3-Tg mice were engrafted with huCD19⁺ E2A-PBX1 cells. On day 2, mice were injected twice with blinatumomab. Leukemia cell burden in the bone marrow were evaluated on day 7. Leukemia cells were identified as cells double positive for both CD19 and huCD19. Left: representative FACS plot. Right: scatter plot showing individual data points and the median. (B) huCD3/20 dual transgenic mice (bred to express CD45.1) were engrafted with huCD20 expressing E2A-PBX1 cells. Two days later, mice were injected with CD20 X CD3 T-BsAb and were then euthanized at day 7. Leukemia cell burden in the bone marrow was evaluated. Leukemia cells were identified based on negative staining for congenic marker CD45.1 and for being double positive for both CD19 and huCD20. Left: representative FACS plot. Right: scatter plot showing individual data points and the median.