In vivo VpreB1-ADC efficacy against a B-ALL cell line xenograft model. NSG mice were transplanted through tail vein injection with 1 × 106 luciferase-labeled NALM-6 cells. (A) BLI was performed pretreatment to quantify engraftment and for randomization of treatment groups. VpreB1-ADC 2 mg/kg, VpreB1 antibody 2 mg/kg, or PBS control (n = 8 mice per group) were administered intraperitoneal (IP) on days 1, 4, and 7. Mice were then followed with serial BLI. (B) On day +10 of therapy, 2 mice from each group were euthanized, bone marrow stained with a human CD19 antibody, and leukemia cells measured by flow cytometry. (C) Kaplan-Meier survival curves for mice treated with VpreB1-ADC, VpreB1 antibody, or PBS. The gray square indicates treatment duration. The log-rank (Mantel-Cox) test was used to compare the survival curves (∗∗∗P < .001). (D) On day +110 of treatment, 2 of the remaining mice from the VpreB1-ADC group were euthanized, bone marrow stained with a human CD19 antibody, and leukemia burden assessed by flow cytometry.
