In vitro activity: KW-2478 inhibits the binding of bRD to Hsp90α with IC50 of 3.8 nM. KW-2478 degradates the Hsp90 client proteins, including FGFR3 and IGF-1Rβand c-Raf-1. KW-2478 reduces the level of phosphorylated Erk1/2. KW-2478 induces apoptosis by cleavage of PARP, a substrate of caspase-3 In U266 cells,. KW-2478 has Time dependency of antiproliferative activity, consecutive drug exposure for at least 12 hours is necessary to to exert potent antitumor activity. KW-2478 downregulates the translocation products of IgH locus. KW-2478 inhibits the transcription of c-Maf and cyclin D1 genes by mainly suppressing the function of Cdk9. KW-2478 has potent and broad growth inhibitory activities against various cell lines, KW-2478 inhibites cancer cell growth in all cell lines, with EC50 of 101-252 nM, 81.4-91.4 nM and 120-622 nM for B-cell lymphoma, mantle cell lymphoma and multiple myeloma, respectively. KW-2478 also shows potent growth inhibitory activity in primary CLL and NHL cells with EC50 of 40-170 nM and 200-400 nM, respectively

Kinase Assay: Human Hsp90α solution (0.5 μg/mL) is fixed on 96-well plates, followed by blocking with TBS containing 1% bovine serum albumin. KW-2478 solutions is added to the wells, and bRD is added to a concentration of 0.1 μmol/L. After removal of solution, poly-HRP streptavidin solution dilutes with poly-HRP dilution buffer is added to the wells. After removal of solution, equal volumes of TMB peroxidase substrate and peroxidase solution B are added to the wells. To stop the HRP reaction, 2 mol/L H2SO4 are added, followed by measurement of absorbance at 450 nm using a microplate spectrophotometer.

Cell Assay: To measure the IC50, OPM-2/green fluorescent protein (GFP) cells, KMS-11 cells, OPM-2/GFP and other cells are plated into 96-well plates and treat with KW-2478. After 72 hours of cultivation, cell viability is determined using Cell Proliferation Reagent WST-1. WST reagent is added to the wells, followed by incubation for 4 hours at 37 °C. After that, the absorbance at 450 nm with reference at 650 nm is measured with a microplate spectrophotometer. To examine time dependency of antiproliferative activity of KW-2478, the cells are plated into 96-well V-bottomed plates and treated with KW-2478. After 0 hour and at intervals from 3 to 72 hours at 37 °C, the supernatant is aspirated. After drug-free medium is added to the wells, the supernatant is aspirated again. Finally, drug-free medium is added to the wells, and the plates are further incubated for the remainder of the 72-hour period, followed by measurement of cell viability.

Clin Cancer Res. 2010 May 15;16(10):2792-802.