Serial ablation of CART123 with alemtuzumab in AML xenograft model. NSG mice were injected with luciferase-expressing MOLM14 cells at week 0 time point, then treated with saline, UTD, or CART123 (n = 10 mice per cohort) at week 1 time point. Some CART123-treated mice were subsequently treated with 1 dose of 1 mg/kg alemtuzumab (alem) IP at 1, 2, or 3 weeks following CART123 (denoted as colored bars or as “A”) (weeks 2, 3, or 4 time points; n = 5 to 8 mice per cohort). Animals were assessed by (A) BLI with (B) quantification of radiance as a surrogate for AML burden, then euthanized when moribund. Two CART123-treated animals (red line in panel A) were found dead at >3 months post-T cells without evidence of recurrent leukemia. Animals in CART123-induced “remission” without and with alemtuzumab were subsequently rechallenged with MOLM14. (C) AML burden by BLI and CD3-PacificBlue⁺ CART123 cells in peripheral blood were quantified during treatment. MOLM14 rechallenge of T-cell–ablated mice at the week 12 time point resulted in rapid AML progression and animal death versus sustained remission of rechallenged non–T-cell–ablated mice with CART123-induced AML remission (****P < .0001 by analysis of variance with log-rank test; denoted for alemtuzumab at week 3 [light green] or week 4 [blue] versus saline control [light blue], and for CART123 [red] versus saline at week 2 or week 3).