Smart thrombosis inhibitors without bleeding side effects via charge tunable ligand design

Abstract

Current treatments to prevent thrombosis, namely anticoagulants and platelets antagonists, remain complicated by the persistent risk of bleeding. Improved therapeutic strategies that diminish this risk would have a huge clinical impact. Antithrombotic agents that neutralize and inhibit polyphosphate (polyP) can be a powerful approach towards such a goal. Here, we report a design concept towards polyP inhibition, termed macromolecular polyanion inhibitors (MPI), with high binding affinity and specificity. Lead antithrombotic candidates are identified through a library screening of molecules which possess low charge density at physiological pH but which increase their charge upon binding to polyP, providing a smart way to enhance their activity and selectivity. The lead MPI candidates demonstrates antithrombotic activity in mouse models of thrombosis, does not give rise to bleeding, and is well tolerated in mice even at very high doses. The developed inhibitor is anticipated to open avenues in thrombosis prevention without bleeding risk, a challenge not addressed by current therapies.

Inhibitors of Polyphosphate and Neutrophil Extracellular Traps

“…We found that our lead compound, MPI 8, was an effective thromboprotective agent in multiple mouse models of arterial and venous thrombosis, while showing no toxicity and, unlike the UHRA compounds, no prolongation of tail bleeding time even at very high doses. 62 This validated the "switchable" protonation state concept as a safer way of inhibiting polyP in vivo.…”

“…More recently, much more biocompatible dendrimer-like agents have been developed that are relatively selective for polyP, and are potent polyP inhibitors that avoid the toxicity of conventional cationic dendrimers. 62 These later-generation dendrimer-like molecules also protect mice against experimentally induced venous and arterial thrombosis, but without prolonging the tail bleeding time or toxicity. Future studies will be required to determine whether these novel agents that target polyP, NETs, or RNA can be translated into human therapeutics.…”

“…Given the effectiveness of targeting polyP to prevent arterial and venous thrombosis in mouse models, 53,54,60,62 it will be of interest to extend these studies to in vivo models of thrombosis and inflammation in other animals, to see if this approach holds promise as a potential future therapeutic modality for human patients.…”

In-vivo functions and regulation of polyphosphate in the vascular system

“…A recent study has also demonstrated the antithrombotic effects of macromolecular polyanion inhibitors (MPI) in mouse models. Similar to other inhibitors, these polyP inhibitors do not increase bleeding [35 ▪▪ ]. Moreover, infusion of a recombinant bacterial exopolyphosphatase (PPX), which specifically degrades polyP longer than 35 P i units, or a variant of PPK lacking enzymatic activity but still capable of binding to the polymer, was shown to interfere with FXII activation and thrombosis, while preserving hemostasis [18].…”

Polyphosphate as an antithrombotic target and hemostatic agent

“…More importantly, phosphatases may also remove phosphates from other physiologically important compounds such as adenosine diphosphate, and thus bring about uncertainties. 161…”