In vitro activity: PS-1145 blocks TNFalpha-induced NF-kappaB activation through inhibition of IkappaBalpha phosphorylation, and blocks the protective effect of IL-6 against Dex-induced apotosis. PS-1145 also inhibits paracrine MM cell growth and IL-6 secretion in BMSCs triggered by MM cell adherence. In human primary CD4(+) T cells, PS-1145 abrogates cell proliferation and impairs the activation of NF-κB and AP-1 transcription factors by engagement of CD3 and CD28 coreceptor

Kinase Assay: PS-1145 are dissolved in DMSO and stored at −20 °C until use. Ki value of PS-1145 against the IKK complex is determined by measuring Km , ATP against varying fixed concentration of the inhibitor. Briefly, partially purified IKK complex obtained from unstimulated HeLa S3 cells are pre-activated using the catalytic domain of MEKK1 expressed in sf9. Kinase activity is assessed using a biotinylated IκBα peptide (250 μM, RHDSGLDSMKD,Km ,peptide = 30 μM,K m , ATP = 10 μM) and phospho-[Ser32]-phosphoantibodies in an ELISA format with appropriate standard curve for quantification. For PS-1145 Ki measurement, the activated IKK complex is first preincubated in varying fixed concentration of the inhibitor (0.1–1 μM) at 25 °C for 1 h. Then apparentK m measurement for MgATP is performed at each discrete inhibitor concentration. 

Cell Assay: The inhibitory effect of PS-1145 on MM growth is assessed by measuring MTT dye absorbance of the cells. Cells (MM.1S, U266, and RPMI8226 cell lines) from 48-h cultures are pulsed with 10 μL of 5 mg/ml MTT to each well for the last 4 h of 48-h cultures, followed by 100 μl of isopropanol containing 0.04N HCl. Absorbance is measured at 570 nm using a spectrophotometer.