The role of quantum chemistry in covalent inhibitor design

Abstract

The recent ascent of targeted covalent inhibitors (TCI) in drug discovery brings new opportunities and challenges to quantum chemical reactivity calculations supporting discovery efforts. TCIs typically form a covalent bond with the targeted nucleophilic amino acid side chain. Their reactivity that can be both computed and experimentally measured is therefore one of the key factors in determining inhibitory potency. Calculation of relevant quantum chemical descriptors and corresponding reaction barriers of model reactions represent efficient ways to predict intrinsic reactivities of covalent ligands. A more comprehensive description of covalent ligand binding is offered by mixed quantum mechanical/molecular mechanical (QM/MM) potentials. Reaction mechanisms can be investigated by the exploration of the potential energy surface as a function of suitable reaction coordinates, and free energy surfaces can also be calculated with molecular dynamics based simulations. Here we review the methodological aspects and discuss applications with primary focus on high-end QM/MM simulations to illustrate the current status of quantum chemical support to covalent inhibitor design. Available QM approaches are suitable to identify likely reaction mechanisms and rate determining steps in the binding of covalent inhibitors. The efficient QM/MM prediction of ligand reactivities complemented with the computational description of the recognition step makes these computations highly useful in covalent drug discovery.