Multiple myeloma and other primary samples from patients with hematologic malignancies are sensitive to IPSI-001. (A) Cellular extracts (5 μg) from CD33⁺ acute myeloma leukemia (AML-01) patient cells were exposed to increasing doses of IPSI-001 and proteasome inhibition was assessed using fluorogenic substrates for the ChT-L, T-L, and C-L activities of the proteasome in triplicate. These data are similar to experiments performed in 3 additional CD19⁺ patient samples. The data shown are the mean plus or minus SD. (B) Purified CD138⁺ plasma cells from patient samples were treated with 25 and 50 μM IPSI-001 for 24 hours, and the effects on cell viability were examined using the WST-1 reagent in triplicate. All of the samples are from patients with chromosome 13 deletions (MM-17, MM-24, MM-26, MM-40, and MM-41). The data shown are the mean plus or minus SD. *P < .05 compared with vehicle control. (C) Apoptosis was measured in a patient-derived bone marrow aspirate purified for CD138⁺ cells, which were treated for 24 hours with IPSI-001 or bortezomib, and then evaluated for programmed cell death using annexin V/TO-PRO-3 staining. (D) Purified CD19⁺ cells or CD33⁺ cells from patient samples were treated with IPSI-001 for 24 hours, and the effects on cell viability were examined using the WST-1 reagent in triplicate. The data shown are the mean plus or minus SD. *P < .05 compared with vehicle alone treatment. (E) Purified lymphocytes from a CLL patient were treated with IPSI-001 for 24 hours. Apoptosis was evaluated using an enzyme-linked immunosorbent assay that detects apoptotic nuclear DNA fragmentation in triplicate. Cell death is expressed as the fold increase in apoptosis over the vehicle control, which was arbitrarily set at 1.0. The data shown are the mean plus or minus SD. (F) Purified lymphocytes from a CLL patient were treated with IPSI-001. Annexin V–positive cells were measured using flow cytometry and results are displayed as the percentage specific apoptotic population.