CD19-DE is efficient in combination with chemotherapy in an overt leukemia model of infant BCP-ALL in NSG mice. (A) Experimental scheme. Patient-derived ALL xenografts were established by orthotopic intrafemoral transplantation of 100 ALL cells per animal in NSG mice (patient 1), and engraftment was awaited for 21 days (day 0). Mice were then left untreated (control, n = 12), treated with antibody CD19-DE following the same scheme as depicted in Figure 1B (antibody, n = 12); treated with a chemotherapy regimen consisting of dexamethasone days 1-5, vincristine on day 1, and PEG-asparaginase day 1 every 28 days (chemotherapy, n = 11); or a combination of chemotherapy and antibody (combination, n = 11). (B) Marked prolongation of survival of xenografted mice by treatment with the combination of chemotherapy and antibody in comparison with all other groups (Kaplan-Meier log-rank test). (C) Percentage of human blasts in the peripheral blood of mice by FACS analysis on day +75 (Mann-Whitney U test). (D, E) Postmortem analyses of the mice depicted in panel B. Spleen volume measured by the formula: longest length × broadest width × highest height as a marker of leukemic burden (D); human leukemic blasts in the bone marrow (E) (Mann-Whitney U test). Note that there is 1 missing value in the combination group because this mouse was found dead and in decay after >24 h and could not be analyzed. Red triangles and squares represent the surviving animals. combi, combination; d, day; Dexa, dexamethasone; chemo, chemothrapy; PEG-Asp, PEG-asparaginase; VCR, vincristine.