In vitro activity: NPI-2358 binds to the colchicine-binding site of tubulin and has potent inhibitory to human tumor cell lines which have overexpressed Pgp or reduced nuclear Topo II catalytic activity, with IC50 from 9.8 to 18 nM. NPI-2358 is able to rapidly induce tubulin depolymerization in HUVECs and monolayer permeability even at 20 nM. NPI-2358 induces cell death in MM cells with IC50 of 8-10 nM, which due to trigger early mitotic arrest in MM cells. NPI-2358 also inhibits tubule formation and migration of endothelial as well as MM cells, which leads to disrupt tumor vasculature. NPI-2358 could induces cell death in patient MM (CD138+) cells without effecting viability of normal mononuclear cells. Blockade of JNK abrogates NPI-2358-induced mitotic arrest or MM cell death.

Cell Assay: The adherent cells (HT-29, PC-3, DU 145, MDA-MB-231, NCI-H292, Jurkat, MES-SA, MES-SA/Dx5, HL-60, HL-60/MX2.) are plated in 96-well flat-bottomed plates and allowed to attach for 24 hours at 37 °C. HL-60 and HL-60/MX2 cells are plated in 96-well plates on the day of NPI-2358 addition. Serially diluted NPI-2358 is added to cells at concentrations ranging from 2 pM to 20 μM. Cells treated with a final concentration of 0.25% (v/v) DMSO serves as the vehicle control. Cell viability is assessed 48 hours later by measuring the reduction of resazurin with a fluorimeter. The IC50 value is calculated.