Effect of continuously intravenously infused blinatumomab on peripheral B-cell counts and apoptosis during the first treatment cycle of MRD⁺ ALL patients. (A) Individual B-cell counts of 20 evaluable patients are shown at baseline and at first occurrence of B-cell depletion ≤ 1 cell/μL. (B) Mean B-cell counts are shown at baseline, at the mean nadir of ≤ 1 cell/μL, at the end of the 4-week treatment period, and at 1 week after the end of infusion. Error bars indicate SD for the respective cell counts and time points. (C) Binding of annexin V to B cells of one patient with slowly declining peripheral B-cell counts. MFI indicates median fluorescence intensity as determined by FACS staining.