In vitro activity: BMS-345541 dose-dependently inhibits the TNF-α-stimulated phosphorylation of IκBα in THP-1 monocytic cells with an IC50 of ~4 μM. BMS-345541 inhibits lipopolysaccharide-stimulated tumor necrosis factorα, interleukin-1β, interleukin-8, and interleukin-6 in THP-1 cells with IC50 values in the 1- to 5 μM range. BMS-345541 binds in a mutually exclusive manner with respect to a peptide inhibitor corresponding to amino acids 26 - 42 of IκBα with Ser-32 and Ser-36 changed to aspartates and in a non-mutually exclusive manner with respect to ADP. BMS-345541 binds to similar allosteric sites on IKK-1 and IKK-2, which then affects the active sites of the subunits differently. BMS-345541 affects several mitotic cell cycle transitions, including mitotic entry, prometaphase to anaphase progression and cytokinesis. Adding BMS-345541 to the cells released form arrest in G-phase blocks the activation of Aurora A, B, and C, Cdk1 activation and histone H3 phosphorylation. Treatment of the mitotic cells with BMS-345541 results in precocious cyclin B1 and securin degradation, defective chromosome separation and improper cytokinesis. BMS-345541 is also found to override the spindle checkpoint in nocodazole-arrested cells. These effects are not primarily due to a direct inhibitory effect of BMS-345541 on mitotic kinases such as Cdk1, Aurora A or B, Plk1 or NEK2. BMS-345541 (10 μM) inhibits growth of Normal human epidermal melanocytes, and metastatic melanoma cells (SK-MEL-5, A375, and Hs 294T) by 96% and 99% at 72h, respectively. Application of 100 μM of BMS-345541 to SK-MEL-5 cell culture results in 87% apoptotic cells at 24 h through caspase-independent and AIF-dependent mitochondria-mediated manner. BMS-345541 treatment (10 μM) results in 76% and 95% reduction in IKK activities and NF-kB activity, as well as CXCL1 production.

Kinase Assay: Assays measuring the enzyme-catalyzed phosphorylation of GST-IκBα are performed by adding enzyme (a final concentration of 0.5 μg/mL) at 30 ℃ to solutions of 100 μg/mL GST- IκBα and 5 μM [33P]ATP in 40 mM Tris HCl, pH 7.5, containing 4 mM MgCl2, 34mM sodium phosphate, 3 mM NaCl, 0.6 mM potassium phosphate, 1 mM KCl, 1 mM dithiothreitol, 3% (w/v) glycerol, and 250 μg/mL bovine serum albumin. The specific activity of [33P]ATP used in the assay is 100 Ci/mmol. After 5 min, the kinase reactions are stopped by the addition of 2× Laemmli sample buffer and heat-treated at 90 ℃ for 1 min. The samples are then loaded on to NuPAGE 10% BisTris gels. After completion of SDS-PAGE, gels are dried on a slab gel dryer. The bands are then detected using a 445Si PhosphorImager, and the radioactivity is quantified using ImageQuant software. Under these conditions, the degree of phosphorylation of GST-IκBα is linear with time and concentration of enzyme.

Cell Assay: 1×105 cells (Metastatic human melanoma cells SK-MEL-5) per well are plated in six-well plates with 10% fetal bovine serum medium overnight to allow cell adhesion. Cells ae cultured in medium containing BMS-345541 for 72 hours of treatment. Cells are counted with a hemocytometer.