Appelbaum et al. reported evidence of in vitro and in vivo antitumor activity against established CD33+ human tumor xenografts in NSG (NOD scid gamma) mouse models.316 However, the Phase 1, PLAT-08 trial of SC-DARIC33 in pediatric patients with AML was put on hold by the FDA following a severe grade 5 adverse event report. Here, CD33 is linked to acute myeloid leukemia.