Binding-Site Switch for Protein Kinase CK2 Inhibitors

The serine/threonine protein kinase CK2, a tetramer composed of a regulatory dimer (CK2β₂) bound to two catalytic subunits CK2α, is a well-established therapeutic target for various pathologies, including cancer and viral infections. Several types of CK2 inhibitors have been developed, including inhibitors that bind to the catalytic ATP-site, bivalent inhibitors that occupy both the CK2α ATP-site and the αD pocket, and inhibitors that target the CK2α/CK2β interface. Interestingly, the bivalent inhibitor AB668 shares a similar chemical structure with the interface inhibitor CCH507. In this study, we designed analogs of CCH507 using structure-based and fragment-based approaches. The ability of these analogs to bind the CK2α/CK2β interface was evaluated using biolayer interferometry and fluorescence anisotropy-based assays. Their potency to inhibit CK2 kinase activity was determined using the bioluminescent ADP-Glo assay. These experiments allowed us to investigate which chemical modifications prevent the binding of the compounds at the CK2α/CK2β interface. Seven out of sixteen compounds conserved the ability to bind at the protein-protein interface, among which three compounds exhibited better interface inhibition compared to CCH507.