Beyond Kinase Inhibition: From Catalytic Blockade to Control of Protein Fate.

Abstract

Kinase inhibitors are a cornerstone of modern drug discovery, with more than 100 approved compounds which have had a transformative impact in precision oncology and inflammatory disease. Their success has rested largely on small-molecule control of catalytic activity through ATP-site engagement; a framework that leaves important biology unaddressed, including non-catalytic kinase functions, resistance driven by active-site mutation, and the limits of selectivity imposed by pocket conservation. Against this backdrop, the observation that kinase inhibitors can reduce target protein abundance has gained new mechanistic depth. Chaperone deprivation, supercharging of native degradation circuits, and context-dependent mutant-selective depletion mark distinct routes through which inhibitor binding can intersect with cellular proteostasis. The kinase inhibitor CR8 extends this logic into chemically encoded degradation: CR8 acts as a molecular glue degrader by creating, within the ligand-bound kinase complex, a composite surface that directly recruits a ubiquitin ligase, resulting in cyclin K degradation. Thalidomide analogues can degrade kinases through scaffolds that do not bind the kinase in isolation: ligase-binding compounds that recruit neosubstrate kinases through recognition of structural surface degrons. Deliberately engineered PROTACs encode ligase-target proximity through heterobifunctional architecture to convert kinase binders into degraders. Beyond degradation, induced-proximity mechanisms - from the clinically established rapamycin to bifunctional molecules that redirect kinase activity or restrict inhibition to tumour cells - show how small molecules can reshape kinase interaction states rather than simply block active sites. Together, these examples define an expanding pharmacological vocabulary for kinase drug discovery: one that asks not only whether a molecule inhibits its target kinase, but how ligand binding rewires protein stability, interactions, localisation, and function.