Selective Inhibition of CK2: Emerging Strategies and Future Directions.

CK2 is a constitutively active serine/threonine kinase implicated in cancer, viral infection, and neurodegeneration, but its conserved ATP-binding site and complex holoenzyme assembly have long made selective inhibition challenging. This Perspective discusses three complementary strategies for selective CK2 inhibition: targeting the CK2α/β interface with small molecules, disrupting the same interface with conformationally constrained peptides, and exploiting the cryptic αD pocket for dual-site inhibitor design. CK2α/β-interface inhibitors, including CAM187, CAM7117 and P8C9, established structurally validated routes to modulate holoenzyme assembly and β-dependent substrate phosphorylation. Validation of the αD pocket as a ligandable cryptosteric site enabled dual-site ligands such as CAM4066 and αD-directed inhibitors such as CAM4712, followed by related advances including AB668, KDX1381 and Biv5. These efforts culminated in APL-5125, a highly selective, subnanomolar dual-site inhibitor now in Phase 1/2 clinical evaluation.