Ghaby, K. | bioRxiv Science

bioRxiv2025

Molecular Dynamics-Guided Design and Chemoproteomic Profiling of Covalent Kinase Activity Probes

Covalent small molecule activity probes can be powerful tools to interrogate protein function in native cellular environments. The design of family-wide activity probes requires an understanding of the molecular sources of general targeting potential and specificity to enable broad targeting of protein family members. Here, we developed and applied a multifaceted docking and molecular dynamics (MD) simulation pipeline to design and test cell-permeable covalent kinase activity probes from a set of hinge-binding pharmacophores. This computationally-guided approach yielded a new cell-active probe, K60P, which targets around 114 kinases across distinct kinase classes in live cells. Chemoproteomic profiling of this probe and a clinical candidate sharing the same indazole core, KW-2449, identified kinase and non-kinase target profiles that differ from recombinant protein assay profiles, underscoring the utility of native kinase profiling in situ. Biochemical studies with a model target kinase, ABL1, confirmed covalent labeling of the active site lysine across several kinase probes with distinct kinetics, as well as covalent labeling of key tyrosines in trans between ABL1 monomers. Finally, focused proteomics, kinetic modeling, and molecular dynamics simulations revealed that K60P, as well as the comparator probe XO44, preferentially engage with target kinases in their active, DFG-in conformations, which is driven by increasing population of reaction-ready small molecule conformation. These results together establish a computational and kinetic modeling framework for designing covalent activity probes and highlight the balance of target selectivity and kinetic efficiency as a key factor in determining their proteome-wide reactivity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/683178v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1ea3e5forg.highwire.dtl.DTLVardef@1a4e999org.highwire.dtl.DTLVardef@1e468c3org.highwire.dtl.DTLVardef@99e04e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2025

Kinetic Modeling of Covalent Inhibition: Effects of Rapidly Fluctuating Intermediate States

There is increasing interest in the discovery of small-molecule inhibitors that form covalent bonds with their targets for therapeutic applications. Nevertheless, identifying clear rational design principles remains challenging because the action of these molecules cannot be understood as common noncovalent inhibitors. Conventional kinetic models often reduce the binding of covalent inhibitors to a two-step irreversible process, overlooking rapid complex dynamics of the associated unlinked inhibitor before the formation of the covalent bond with its target. In the present analysis, we expand the intermediate state into two conformations--reactive (E{middle dot}I) and nonreactive (E{middle dot}{middle dot}I). To illustrate the consequences of such simplification, the expanded kinetic model can be reduced to an effective two-step scheme expressed in terms of the equilibrium probability of the unlinked inhibitor to form either conformation. A mass-action-based numerical workflow is implemented to simulate time-dependent kinetics, overcoming the common limitations of empirical models. The numerical workflow helps relate microscopic states observed in molecular dynamics simulations to macroscopic observables like EC50 and the apparent rate of covalent inhibition, showing the impact of transient intermediates on dissociation rates and potency. The proposed framework refines the interpretation of dose-response data, aiding medicinal chemists in optimizing covalent inhibitors and provides a quantitative platform for relating molecular conformational distributions to empirical parameters. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/656658v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@3ae1e6org.highwire.dtl.DTLVardef@1c4c535org.highwire.dtl.DTLVardef@16f3627org.highwire.dtl.DTLVardef@4c3f47_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗