Aug 2026· Future Medicinal Chemistry· pp.
1-17
· 0 citations· 127 references
Medicine
TL;DR
The structural and medicinal chemistry principles underlying (i) allosteric inhibition and (ii) proximity-induced degradation are summarized, with an emphasis on design logic, structure-activity relationships, and key liabilities in the beyond rule of five space.
Abstract
Protein kinases are central regulators of cellular signaling and remain a major target class in precision medicine. While ATP-competitive inhibitors-including conformation-selective and covalent agents-have delivered substantial clinical benefit, durable responses are frequently limited by the conservation of the ATP pocket and the emergence of resistance mutations (e.g. gatekeeper and solvent-front substitutions), as well as kinase noncatalytic functions that are not addressed by enzymatic inhibition alone. Consequently, kinase drug discovery is expanding beyond orthosteric occupancy toward modalities that reprogram kinase conformations or eliminate the target protein. This Review summarizes the structural and medicinal chemistry principles underlying (i) allosteric inhibition and (ii) proximity-induced degradation, with an emphasis on design logic, structure-activity relationships, and key liabilities in the beyond rule of five space. We further highlight enabling technologies-including structural biology, chemical proteomics, and AI/ML-assisted modeling-that support allosteric site identification, ternary complex engineering, and multi-parameter optimization. Finally, we discuss translational challenges for bifunctional molecules, including permeability, exposure-response relationships, off-target degradation, and safety, and propose practical considerations for developing next-generation selective kinase therapeutics.
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.
J. Diepeveen, Z. Kozicka· Chimia (Basel)· 0 citations
An overview of the developmental trajectory of the TPD field is provided and how diverse modalities can be leveraged to address intracellular, membrane-associated, and extracellular protein targets are discussed.
Yu-bo Zhang, Junwei Fu, Yue Liu et al.· Acta Pharmacologica Sinica· 0 citations
Drug resistance in epidermal growth factor receptor (EGFR)-mutant cancers commonly arises from kinase-domain substitutions that remodel the adenosine triphosphate binding pocket and reduce complementarity to orthosteric inhibitors, with the T790M gatekeeper mutation posing a major challenge. This study evaluated whether pre-occupying a proximal allosteric pocket with selected phytochemicals could bias mutant EGFR toward drug-compatible conformations and improve inhibitor binding. A two-phase computational workflow was employed: (i) molecular docking of gefitinib and erlotinib to wild-type and mutant EGFR; and (ii) allosteric pre-docking of phytochemicals followed by redocking of the ATP-site inhibitor. Top-ranked complexes were advanced to 200-nanosecond all-atom molecular dynamics simulations in explicit solvent and end-state binding free-energy estimation using Molecular Mechanics Generalized Born Surface Area (MM/GBSA). Docking predicted stronger binding to wild-type EGFR and reduced affinity for the T790M mutant, whereas co-binding produced compound-dependent improvements. Simulations suggested partial stabilization of the protein-ligand complexes, characterized by reduced root mean square deviation, damped hinge and αC-helix motions, reduced solvent exposure, and radii of gyration approaching wild-type behavior. Binding free energies improved from -12.6 to -17.6 kcal mol-1 (Genistein) and -19.58 kcal mol-1 (Tupichinols C) for gefitinib, and from -13.4 to -18.1 and -20.1 kcal mol-1, respectively, for erlotinib. Absorption, distribution, metabolism, excretion, and toxicity screening supported the developability of the leading candidates. This integrated framework provides structural, dynamic, and energetic criteria for prioritize cooperative allosteric-orthosteric co-binding chemotypes for experimental validation.
A. Sindi· Journal of Biomolecular Stru...· 0 citations
Current rational drug design relies predominantly on computational (CADD/AIDD) methods that model binding thermodynamics and static conformations of target proteins, primarily in their inactive states. However, the kinetic parameters that govern experimental efficacy—such as catalytic turnover and signaling potency—are determined by molecular interactions with transition states (TS), intermediate states (IS), and the entire continuum of conformations along the least free-energy activation pathway. The absence of this dynamic dimension has fundamentally limited the predictive power and success rate of conventional structure-based approaches. Here, we present a structural database that systematically maps the complete activation trajectories of pharmaceutically relevant targets, encompassing TS, IS, and all connecting conformational ensembles. This resource offers multiple strategic advantages for drug discovery: enabling rational targeting of previously “undruggable” proteins, facilitating biased agonism/antagonism design, revealing cryptic allosteric sites in inactive conformations, identifying novel transient pockets along the activation route, rationalizing the mechanisms of existing drugs, predicting mutational effects on activation barriers, and prospectively forecasting drug resistance and off-target liabilities. We demonstrate the utility of this database through representative case studies and provide implementation guidelines for integration into existing discovery pipelines. More detailed information can be found at our website: https://www.momedpamdb.com/en. Terminology The following terms are clarified in this document: Stable state (SS): In this document, this term refers exclusively to, and is synonymous with, the protein’s inactive state (IAS). Note that other states may also be stabilized into meta-stable states by certain means. Unstable state (US): This term encompasses all states other than SS, even if they appear computationally meta-stable on the free energy surface. Activated state (AS): The meta-stable working state of the protein. Transition state (TS): The state with the highest free energy along the least-energy pathway on the free energy surface that connects the inactive state to the activated state of the target protein. Intermediate state (IS): The state(s) located at a local minimum along the least-energy pathway, excluding SS and AS.
Protein kinases are central to biological regulation, dysregulated in many diseases, and the targets of a hundred clinically-approved drugs. Structural conservation of kinase active sites makes the development of specific inhibitors challenging. Targeting functional secondary sites can increase specificity, reduce toxicity, overcome resistance mutations, and also activate kinases. However, the functional secondary sites to target in most kinases are unknown, and the conservation of allosteric networks in kinases and other proteins that share the same structural fold is unclear. Here, we quantify the activity and abundance of >160,000 variants to construct complete maps of the energetic and allosteric architectures of five human kinase domains: SRC, FGR, JNK2/MAPK9, ZAK/MAP3K20, and TSSK2. For inhibition, all five kinases have distance-dependent but anisotropic allostery and each kinase has a unique allosteric architecture, surface, and set of pockets to therapeutically target. A set of functional secondary sites is conserved in all five proteins, but other allosteric pockets are protein-specific or switch from inhibitory to activating in different proteins. The differences in the energetic architectures are particularly striking for activation, where the allosteric maps are highly diverged. The allosteric architecture of each kinase is therefore unique, with a distinct set of functional secondary sites to regulate and therapeutically target.
Carla Folgado, Antoni Beltran, Ben Lehner· bioRxiv· 0 citations
The development of the C797S resistance mutation to third-generation tyrosine kinase inhibitors in EGFR-mutant non-small cell lung cancer is a key therapeutic barrier, and this renders standard orthosteric site competitive inhibitors futile. Allosteric inhibitors of EGFR have emerged as a promising strategy for overcoming this resistance mechanism due to a structurally distinct binding site approximately 15-20 Å from the C797S mutation that confers potency independent of the status of cysteine-797. This comprehensive review summarizes the last decade of allosteric EGFR inhibitor medicinal chemistry, including 185 compounds across eight scaffold classes representing the entire reported landscape of efforts toward targeting EGFR with small molecules allosterically. The aminothiazole scaffold dominates the field with 57 compounds, followed by 4-anilinoquinazoline with 39 compounds; the focus of the field is concentrated on these privileged scaffolds. Five universal design principles governing allosteric potency have been identified through structure-activity relationship analysis: the formation of a hydrogen bond network, complementarity to a hydrophobic pocket, bivalent binding architecture based on a dual heterocycle, precise linker geometry, and core heterocycle identity. These principles account for the spectacular potency achievements that include 11 compounds reaching ultra-nanomolar potency (IC₅₀ < 1 nM) and 54 compounds attaining single-digit nanomolar activity. The aminothiazole-isoindolinone hybrid attained the most potent compound 4 with 0.10 nM, which is 20-fold, improved from the foundational EAI045 compound. The maturity of the field peaked in 2022 in optimization efforts, with 85 compounds reported. This review establishes that allosteric EGFR inhibition represents a clinically viable strategy for addressing osimertinib resistance, with lead candidates ready for clinical translation.
Ibrahim Mohammed Hepishy, Mo'men Salem, Ahmed El-morsy et al.· Bioorganic chemistry (Print)· 0 citations