Activity of GX015-070 against primary myeloma cells and CFUs. (A) BM-derived MNCs from 14 MM patients were incubated with 125 nM (▩), 250 nM (▦), or 500 nM (▨) GX015-070 for 3 days, after which the samples were labeled with annexin V–FITC and CD138-PE antibody. Viable CD138⁺ plasma cells in drug-treated groups were normalized to vehicle-treated group. (B) Unpurified BM mononuclear cells from BM aspirate of a representative MM patient (which contain CD138⁺ MM cells and CD138⁻ non-MM cells) were cultured in the presence of DMSO control (left panel) or 500 nM GX015-070 (right panel). GX015-070 led to specific reduction in the percentage of the CD138⁺ MM population. (C) PBMCs (n = 3) were cultured in the presence of GX015-070 (0-4000 nM) for 48 hours. Cell viability was assessed by MTT assay, and data represent means of triplicate cultures; bars represent SD. (D) MNCs from BM were plated in methylcellulose cultures and treated with 250 nM (▦) or 500 nM (▨) GX015-070, and colonies were counted after 7 to 9 days. Each letter represents an individual BM sample. The results are reported as percent of vehicle treated control.