To exclude the possibility that the observed results of the irinotecan treatment are only valid in leukemia cell line models, we also investigated the anti-leukemic efficacy of irinotecan in patient-derived xenograft (PDX) models with leukemic cells from two MLL-rearranged infant ALL patients (UPID VU9815, corresponding to patient C in Figure 1e, and UPID 788). This evidence concerns the gene KMT2A and leukemia.