Abstract: Protein structure is increasingly understood as a dynamic ensemble rather than a single rigid entity. Within this ensemble, transient cavities can emerge that are absent or poorly defined in conventional ligand-free structures. These cryptic binding pockets provide opportunities to modulate proteins for which conventional orthosteric drug discovery has been unsuccessful. Because many cryptic pockets are spatially separated from catalytic or orthosteric sites, their exploitation frequently overlaps with the pharmacological concept of allostery. Structural fluctuations, loop displacement, side-chain rearrangement, hydration changes, and domain motions can therefore generate previously unrecognized ligandable states. Experimental approaches including fragment-based crystallography, nuclear magnetic resonance, hydrogen–deuterium exchange mass spectrometry, covalent tethering, and cryogenic electron microscopy are increasingly complemented by molecular dynamics, enhanced sampling, Markov state modeling, mixed-solvent simulations, and machine-learning-based pocket prediction. These approaches have revealed therapeutically relevant vulnerabilities in KRAS, mutant p53, BACE-1, muscarinic receptors, SARS-CoV-2 proteins, Ebola virus VP35, kinases, and other disease-associated proteins. The KRAS G12C switch-II pocket provides a landmark example in which a mutation-associated cryptic site was transformed into a clinically validated therapeutic opportunity. More recent developments demonstrate that cryptic-pocket discovery can also support fragment-derived, covalent, macrocyclic, allosteric, and targeted-degradation strategies. Nevertheless, transient occupancy, uncertain ligandability, resistance, species differences, and incomplete links between binding and functional modulation remain important barriers. Integration of dynamic structural biology with artificial intelligence, chemical biology, medicinal chemistry, and translational pharmacology is likely to define the next stage of cryptic-pocket-enabled drug discovery.
Keywords: Cryptic Pocket, Allostery, Protein Dynamics, KRAS, Mutant p53, BACE-1