Silmitasertib (CX-4945)

2 years -80 in solvent

Oral gavage twice daily

SKBr3, MDA-MB-453, BT-474, ZR-75-1, MDA-MB-231, MDA-MB-468, T47D, MCF 7, Hs578T, MDA-MB-361, UACC-812, et al.

Dissolved in DMSO, final concentrations ca.100 uM

Dissolved in DMSO, and diluted in PBS

CX-4945 is selective for CK2, as it only inhibits 7 of the 238 kinases by more than 90% at concentration of 0.5 uM, 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 uM 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 uM. The antiproliferative activity of CX-4945 correlates with CK2alpha mRNA and protein levels but not the CK2alpha' catalytic subunit, the regulatory CK2beta 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 uM, 2 uM, and 4 uM, 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-1alpha transcription. [1] CX-4945 potently inhibits endogenous intracellular CK2 activity with IC50 of 0.1 uM in Jurkat cells. [2]

4 days

Cells are seeded at a density of 3, 000 cells per well 24 hours prior to treatment, in appropriate media, and then treated with various concentrations of CX-4945. Suspensions cells are seeded and treated on the same day. Following 4 days of incubation, Alamar Blue (20 uL, 10% of volume per well) is added and the cells are further incubated at 37 C for 4-5 hours. Fluorescence with excitation wavelength at 530-560 nm and emission wavelength at 590 nm is measured.

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). Silmitasertib induces autophagy and promotes apoptosis. Phase 1/2.

First clinical inhibitor of CK2