Click Chemistry In Situ: Acetylcholinesterase as a Reaction Vessel for the Selective Assembly of a Femtomolar Inhibitor from an Array of Building Blocks

Abstract

The generation and/or optimization of lead compounds by combinatorial methods has become widely accepted in medicinal chemistry, and is the subject of continued improvement. [1±3] However, most combinatorial strategies remain dependent upon iterative cycles of synthesis and screening. The direct involvement of the target, usually a receptor or enzyme, in the selection, evolution, and screening of drug candidates can accelerate the discovery process by shortcircuiting its traditionally stepwise nature. [4±11] The use of an enzyme target to select building blocks and synthesize its own inhibitor is a relatively unexplored option. This approach depends on the simultaneous binding of two ligands, decorated with complementary reactive groups, to adjacent sites on the protein; their co-localization is then likely to accelerate the reaction that connects them. [12] When the catalysis of such bond formation is blocked by product inhibition, the higher affinity products [12±14] then serve as lead compounds. This and similar approaches that have been adopted by a number of investigators employ one of five types[*] Prof.

Multivalency in Ligand Design

“…This patch was relatively non-discriminating towards the type of hydrophobic group in the ligand, depending only on the size of the group: for instance, ligands with benzyl, adamantyl, and octyl groups all bound with roughly the same (~nM) avidity [96]. Finn, Sharpless, and co-workers applied a Huisgen 1,3-dipolar cycloaddition templated by acetylcholinesterase to generate a tight-binding ligand for the enzyme (K d avidity = 77-410 fM) from known monovalent ligands (K d affinity~n M-mM) that bound two different sites on the enzyme: the active site and a "peripheral" site at the rim of the active site gorge [127]. Rosenberg, Fesik, and co-workers reported similar covalent tethering to synthesize a high-avidity (K d avidity^1 nM) hetero-bivalent ligand for Bcl-2 family proteins from low-affinity monovalent ligands (K d affinity~m M) to an active site and an adjacent hydrophobic patch (Chapter 9) [128].…”

New approaches to selectively target cancer-associated matrix metalloproteinase activity

“…Click chemistry can be used for the design of MMP inhibitors via the in situ assembly of inhibitors inside MMP binding pocket. Similar approaches have been successfully employed for other enzymes such as acetylcholinesterase (AChE) [33]. AChE acted as the reaction bait and selected possible pairs of reactants in the synthesis of its own highly regioselective inhibitor, by an equilibrium-controlled sampling of various combinations until the irreversible cycloaddition (azidealkyne cycloaddition) between azide and acetylene essentially "froze" the pair that best fit into AChE's fits binding pocket.…”

The Design of RNA Binders: Targeting the HIV Replication Cycle as a Case Study

“…[131] However, entry of this dimeric compound in the binding pocket should be obviously seriously constrained due to the geometry of both "A site motifs" and the very limited amount of free space left for the linker within the loop-loop helix. An attractive approach to overcome this drug entry problem would be an RNA-templated in situ click reaction [132,133] leading to the formation of an aminoglycoside dimer.…”