Primary CP CML cells are killed by IL1RAP antibodies in vivo. NSGS mice were transplanted with CD34⁺ CP CML cells from 2 patients and treated biweekly with 50 μg IL1RAP antibody mAb81.2 or a mIgG2a isotype control antibody until euthanization 40 days after transplantation (mice given mAb81.2 or control antibody: n = 4 and n = 5 in CP-CML1, n = 5 and n = 5 in CP-CML2, respectively). Treatment was started 1 (CP-CML1) or 3 days (CP-CML2) after transplantation. (A-E) The levels of human (CD45⁺) cells and proportions of IL1RAP expressing and myeloid (CD33⁺) cells within the human cell population is presented in PB (A-B), BM (C), and spleen (D-E). (F) Levels of CD34⁺CD38⁻IL1RAP⁺ CML cells within the CD45⁺ population in the spleen. (G) Relative levels of BCR/ABL1 transcripts in spleens.