Synthesis of Polyvalent Inhibitors of Controlled Molecular Weight:  Structure−Activity Relationship for Inhibitors of Anthrax Toxin

Abstract

We describe a novel method to synthesize activated polymers of controlled molecular weight and apply this method to investigate the relationship between the structure and activity of polyvalent inhibitors of anthrax toxin. In particular, we observe an initial sharp increase in potency with increasing ligand density, followed by a plateau where potency is independent of ligand density. Our simple strategy for designing polyvalent inhibitors of controlled molecular weight and ligand density will be broadly applicable for designing inhibitors for a variety of pathogens and toxins, and for elucidating structure-activity relationships in these systems. Our results also demonstrate a role for kinetics in influencing inhibitory potency in polyvalent systems. Finally, our work presents a synthetic route to polyvalent inhibitors that are more structurally defined and effective in vivo. This control over inhibitor composition will be generally useful for the optimization of inhibitor potency and pharmacokinetics, and for the eventual application of these molecules in vivo.

Design of Monodisperse and Well‐Defined Polypeptide‐Based Polyvalent Inhibitors of Anthrax Toxin

“…[3] In previous work, phage display was used to identify a 12-mer peptide (HTSTYWWLDGAP) that binds to (PA 63 ) 7. [10] Polyvalent inhibitors have been created by attaching multiple copies of this peptide to a variety of scaffolds such as polymers, [12] liposomes, [13] and β-cyclodextrin. [14] Structure-based design is a particularly effective strategy to design polyvalent inhibitors of anthrax lethal toxin and other targets.…”

“…[14] Structure-based design is a particularly effective strategy to design polyvalent inhibitors of anthrax lethal toxin and other targets. [11][12][13][14][15][16] Ligand spacing and valency are key parameters that influence the efficacy of polyvalent molecules (Scheme 1A). [12][13][14]17] The ligand spacing is simply the distance separating adjacent ligands on a polyvalent molecule.…”

“…[11][12][13][14][15][16] Ligand spacing and valency are key parameters that influence the efficacy of polyvalent molecules (Scheme 1A). [12][13][14]17] The ligand spacing is simply the distance separating adjacent ligands on a polyvalent molecule. [5,13,14] Matching the ligand spacing on the polyvalent molecule to the distance between ligand binding sites on the target molecule has been shown to be an effective strategy to design potent polyvalent ligands.…”

“…Optimizing the valency is another effective strategy to enhance the binding of a synthetic polyvalent molecule to its target. [3,5,12,13,14] For instance, Gujraty et al designed polyvalent inhibitors of anthrax toxin using polymeric scaffolds of controlled molecular weight and reported an initial sharp increase in potency with increasing valency, followed by a plateau where potency was independent of valency. [12] Matching the valency of the polyvalent molecule to the number of binding sites on the target molecule may also be an effective strategy.…”

“…[3,5,12,13,14] For instance, Gujraty et al designed polyvalent inhibitors of anthrax toxin using polymeric scaffolds of controlled molecular weight and reported an initial sharp increase in potency with increasing valency, followed by a plateau where potency was independent of valency. [12] Matching the valency of the polyvalent molecule to the number of binding sites on the target molecule may also be an effective strategy. [5,12,14] For polyvalent conjugates, the number of ligand molecules attached to the scaffold can usually be adjusted by varying the relative molar ratio of ligands to scaffold during a conjugation reaction.…”