Ibrutinib treatment leads to decreased CLL levels and increased donor chimerism levels. CLL clones per 1 million WBCs and blood donor CD3 T-cell percentage were assessed at various time points posttransplant and during ibrutinib treatment. Data are shown for 6 representative patients: (A) SPN3975, (B) SPN3431, (C) SPN4158, (D) SPN3873, (E) SPN3697, and (F) SPN3903.