Library screen of β-lactams for more potent analogs. (A and B), Raji leukemic cells were treated with solvent (DMSO), 50 or 100 µM of each indicated compound for 24 h, followed by trypan blue exclusion assay. (C) HL-60 leukemic cells were treated with solvent (DMSO), 50 or 100 µM of each indicated analog for 24 h, followed by trypan blue exclusion assay. The numbers given are percentages of nonviable cells to total cells. Standard Deviations are shown with error bars from a mean of three different experiments.