IPSI-001 is able to overcome chemotherapy resistance. (A) Drug-free for at least 48 hours; doxorubicin-, melphalan-, and bortezomib-resistant RPMI 8226; and dexamethasone-sensitive and-resistant MM1 multiple myeloma cell lines were exposed to increasing doses of IPSI-001 for 24 hours in duplicate, followed by determination of apoptotic cell populations using dual annexin V/TOPRO-3 staining. The data shown are the mean plus or minus SD from 3 independent experiments. (B) Melphalan-resistant 8226.LR5 cells were treated with IPSI-001 (25 and 50 μM) for 24 hours and apoptosis was measured using a commercial kit for apoptotic DNA fragmentation. The data shown are the mean plus or minus SD. *P < .05 compared with vehicle control. (C) ANBL-6.wt and ANBL-6.BR were compared for their sensitivity to IPSI-001 after a 24-hour exposure using WST-1 proliferation assay. The data shown are the mean plus or minus SD from experiments performed in triplicate. (D) 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 in triplicate. Cytogenetic studies showed that MM-33 had a chromosome 13 deletion and MM-38 had a chromosome 9 deletion and trisomy 11, whereas the MM-42 sample was not evaluated. The data shown are the mean plus or minus SD. (E) RPMI 8226 cell lines resistant to doxorubicin, melphalan, and bortezomib were treated with the calpain inhibitor E64d and analyzed for annexin V staining by flow cytometry. Representative results from 2 independent experiments are shown as the mean plus or minus SD.