KRN5500 is less cytotoxic toward normal T cells and B cells. (A) T cells were selected from normal peripheral blood mononuclear cells using CD3 MACS beads. (B) B cells were selected from normal peripheral blood mononuclear cells using CD19 MACS beads. In both panels, 1 × 10⁶ cells were incubated in each of 4 wells for each drug concentration. Plates were incubated for 4 hours, and cells were then washed and replated in fresh media without drug for an additional 92 hours. MTT reagent was then added, and after a further 24-hour incubation plates were processed and analyzed. Viability is expressed as percent of media control.