Multivalent Benzamidine Molecules for Plasmin Inhibition: Effect of Valency and Linker Length

There is an emerging interest in utilizing synthetic multivalent inhibitors that comprise of multiple inhibitor moieties linked on a common scaffold to achieve strong and selective enzyme inhibition. As multivalent inhibition is impacted by valency and linker length, in this study, we explore the effect of multivalent benzamidine inhibitors of varying valency and linker length on plasmin inhibition. Plasmin is an endogenous enzyme responsible for digesting fibrin present in blood clots. Monovalent plasmin(ogen) inhibitors are utilized clinically to treat hyperfibrinolysis‐associated bleeding events. Benzamidine is a reversible inhibitor that binds to plasmin's active site. Herein, multivalent benzamidine inhibitors of varying valencies (mono‐, bi‐ and tri‐valent) and linker lengths (∼1–12 nm) were synthesized to systematically study their effect on plasmin inhibition. Inhibition assays were performed using a plasmin substrate (S‐2251) to determine inhibition constants (Ki). Pentamidine (shortest bivalent) and Tri‐AMB (shortest trivalent) were the strongest inhibitors with Ki values of 2.1±0.8 and 3.9±1.7 μM, respectively. Overall, increasing valency and decreasing linker length, increases effective local concentration of the inhibitor and therefore, resulted in stronger inhibition of plasmin via statistical rebinding. This study aids in the design of multivalent inhibitors that can achieve desired enzyme inhibition by means of modulating valency and linker length.