Molecular Weight(MW): 349.77
Silmitasertib (CX-4945) is a potent and selective inhibitor of CK2 (casein kinase 2) with IC50 of 1 nM in a cell-free assay, less potent to Flt3, Pim1 and CDK1 (inactive in cell-based assay). Phase 1/2.
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(E) Pretreatment with CX4945 blocks TNF-induced phosphorylation of BRMS1. H157 cells were pretreated with CX4945 (30 µM) for 2 h, followed by stimulation with TNF (20 ng/mL) for an additional 1 h. Immunofluorescence assays were performed using antibodies against BRMS1 (pS30) (red)/CK2α' (green)/DAPI (blue).
Cancer Res, 2016, 76(9):2675-86. Silmitasertib (CX-4945) purchased from Selleck.
Immunofluorescence analysis for Ser536 p-NF-κB cellular localization of RS4;11cells treated with CX-4945 (5 μM) and bortezomib (2.5 nM) either alone or in combination. Cells were treated, collected at 22 h and reacted with an antibody to Ser536 p-NF-κB which was revealed by a Cy3-conjugated secondary antibody. DAPI was used to label nuclei.
Oncotarget, 2015, 51: S659-S660. Silmitasertib (CX-4945) purchased from Selleck.
Purity & Quality Control
Choose Selective Casein Kinase Inhibitors
|Description||Silmitasertib (CX-4945) is a potent and selective inhibitor of CK2 (casein kinase 2) with IC50 of 1 nM in a cell-free assay, less potent to Flt3, Pim1 and CDK1 (inactive in cell-based assay). Phase 1/2.|
|Features||First clinical inhibitor of CK2.|
CX-4945 is selective for CK2, as it only inhibits 7 of the 238 kinases by more than 90% at concentration of 0.5 μM, which is 500-fold greater than the IC50 of CK2. Although in cell-free systems CX-4945 inhibits FLT3, PIM1, and CDK1 with IC50 of 35 nM, 46 nM, and 56 nM, respectively, CX-4945 treatment at 10 μM is inactive against FLT3, PIM1, and CDK1 in cell-based functional assays. CX-4945 exhibits a broad spectrum of antiproliferative activity, and the breast cancer cell lines displays the widest range of sensitivity to CX-4945 with EC50 of 1.71-20.01 μM. The antiproliferative activity of CX-4945 correlates with CK2α mRNA and protein levels but not the CK2α' catalytic subunit, the regulatory CK2β subunit, and the PI3K/Akt or PTEN mutational status. CX-4945 inhibits PI3K/Akt signaling by directly blocking the phosphorylation of Akt at Serine 129 by CK2 rather than through activation of PTEN. CX-4945 treatment causes reduced phosphorylation of p21 (T145), increased levels of total p21 and p27, and induction of caspase 3/7 activity. CX-4945 treatment induces a G2/M cell-cycle arrest in BT-474 cells and a G1 arrest in BxPC-3 cells. CX-4945 inhibits HUVEC proliferation, migration, and tube formation with IC50 of 5.5 μM, 2 μM, and 4 μM, respectively. Under hypoxic conditions in BT-474 and BxPC-3 cells, CX-4945 treatment prevents downregulation of p53 and pVHL and reduces activation of HIF-1α transcription.  CX-4945 potently inhibits endogenous intracellular CK2 activity with IC50 of 0.1 μM in Jurkat cells. 
|In vivo||Oral administration of CX-4945 at 25 mg/kg or 75 mg/kg twice daily displays potent antitumor activity in the BT-474 model, with TGI of 88% and 97%, respectively, and 2 of 9 animals in each group showing more than 50% reduction in tumor size compared with the initial tumor volume. In the BxPC-3 model, CX-4945 treatment at 75 mg/kg twice daily shows 93% TGI with 3 animals having no evidence of tumor remaining at the end of the treatment period.  In PC3 xenograft model, administration of CX-4945 at 25 mg/kg, 50 mg/kg, or 75 mg/kg causes tumor growth inhibition with TGI of 19%, 40%, and 86%, respectively. |
CK2 Kinase Assay:CX-4945 is added at a volume of 10 μL to a reaction mixture comprising 10 μL of assay dilution buffer (ADB; 20 mM MOPS, pH 7.2, 25 mM β-glycerolphosphate, 5 mM EGTA, 1 mM sodium orthovanadate, and 1 mM dithiothreitol), 10 μL of substrate peptide (RRRDDDSDDD, dissolved in ADB at a concentration of 1 mM), 10 μL of recombinant human CK2 (ααββ-holoenzyme, 25 ng dissolved in ADB). Reactions are initiated by the addition of 10 μL of ATP solution (90% 75 mM MgCl2, 75 μM ATP (final ATP concentration=15 μM) dissolved in ADB; 10% [γ-33P]ATP (stock 1 mCi/100 μL; 3000 Ci/mM and maintained for 10 minutes at 30 °C. The reactions are quenched with 100 μL of 0.75% phosphoric acid and then transferred to and filtered through a phosphocellulose filter plate. After washing each well five times with 0.75% phosphoric acid, the plate is dried under vacuum for 5 minutes and, following the addition of 15 μL of scintillation fluid to each well, the residual radioactivity is measured using a Wallac luminescence counter. The IC50 values are derived from eight concentrations of CX-4945 over a range of 0.0001 μM to 1 μM.
|In vitro||DMSO||16 mg/mL (45.74 mM)|
|In vivo||Add solvents individually and in order:
1% CMC Na
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Clinical Trial Information
|NCT Number||Recruitment||Conditions||Sponsor/Collaborators||Start Date||Phases|
|NCT02128282||Recruiting||Cholangiocarcinoma||Senhwa Biosciences, Inc.||June 2014||Phase 1|Phase 2|
|NCT01199718||Unknown status||Multiple Myeloma||Cylene Pharmaceuticals||September 2010||Phase 1|
|NCT00891280||Unknown status||Advanced Solid Tumors|Breast Cancer|Inflammatory Breast Cancer|Castlemans Disease|Multiple Myeloma||Cylene Pharmaceuticals||February 2009||Phase 1|
Answers to questions you may have can be found in the inhibitor handling instructions. Topics include how to prepare stock solutions, how to store inhibitors, and issues that need special attention for cell-based assays and animal experiments.
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Frequently Asked Questions
How to reconstitute the compound (S2248) for in vivo uses?
For injection, CX-4945 can be dissolved in 2% DMSO+30% PEG 300+2% Tween 80+ddH2O at 5mg/ml clearly. When making the solution, please dissolve the compound in DMSO clearly first. If it dissolves not readily, please sonicate and warm the solution in water bath at about 45-50℃. Then add PEG and Tween. After they mixed well, dilute with water. For oral gavage, CX-4945 can be dissolved in 1% CMC Na at 30mg/ml as a homogeneous suspension. This is a common formulation for oral gavage, and is convenience to prepare.