Chaetocin kills freshly collected sorted patient CD138⁺ myeloma cells while sparing matched normal CD138⁻ bone marrow leukocytes, normal B cells, and neoplastic B-CLL (chronic lymphocytic leukemia) cells. Results from 3 representative myeloma patients (of 20 similarly assessed; A-C), 3 healthy patients (D-F), and 3 B-CLL patients (G-H) are displayed. (A-C) Chaetocin kills patient myeloma cells while sparing matched normal patient leukocytes. Patient A (M-1) had therapy-refractory myeloma, failing prior treatment with thalidomide, dexamethasone, and bortezomib (labeling index = 0.6%); patient B (M-2) had previously untreated smoldering myeloma (labeling index = 1%); patient C (M-3) had stable disease, currently undergoing treatment with dexamethasone (labeling index = 0.2%). (D-F) Chaetocin treatment of normal B cells or matched leukocytes from 3 healthy patients indicates that, unlike myeloma cells, normal B cells are not selectively killed by chaetocin. (G-H) Treatment of B-CLL cells or matched patient leukocytes from 2 B-CLL patients with chaetocin also indicates that, unlike myeloma cells, B-CLL cells are not selectively killed by chaetocin. All patient samples were treated with chaetocin for 24 hours, with survival assessed at that time using trypan blue exclusion and quantitation with a hemocytometer.