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.
Cited by 12 Publications
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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.
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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)|
* 1 mg/ml means slightly soluble or insoluble.
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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|
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