Towards the targeted protein degradation of CK2: design and synthesis of CAM4066-based PROTACs

Human protein kinase CK2 is a constitutively active serine/threonine kinase implicated in numerous cancers. Although ATP-competitive inhibitors such as CX-4945 show therapeutic potential, they are limited by off-target effects and incomplete or transient CK2 suppression. PROTACs offer an alternative strategy by inducing proteasome-mediated degradation, with potential advantages in potency, selectivity, and duration of action. Herein, a series of CK2-targeting PROTACs has been designed and synthesised. By conjugating a CAM4066-derived warhead to CRBN or VHL ligands, four VHL-recruiting PROTACs, were prepared using PEG and alkyl linkers, alongside two CRBN-recruiting analogues featuring constrained linkers. A ligand–linker analogue in which a linker is projected from the solvent-exposed region of CK2α retained binding affinity comparable to CAM4066, confirming that linker installation is tolerated and preserves key interactions in the αD and ATP sites.