Patent Application
20240398853
Provided herein are compositions and methods to prevent and to treat thrombosis, to reverse the anticoagulant action of heparin, and to prevent and to treat the thrombotic and antifibrinolytic effect of nucleic acids. In particular, provided herein are compositions, methods, kits, systems and uses for switchable charge state multivalent biocompatible polycations for polyanion inhibition in blood.
Synthetic polycations provide biological applications as binding partners for polyanions including, for example, polyphosphates, heparin, and extracellular nucleic acids, due to strong affinity for their polyanion ligands. However, polycations are notorious for nonspecific interactions with negatively charged components in the blood and body with consequential deleterious off-target effects. An unmet challenge to the present is to increase the binding affinity and selectivity of biologic and clinical polycations while enhancing their biocompatibility.
Synthetic polycations provide applications in a diversity of biological settings, including gene delivery via interaction with the phosphate backbone of DNA (Liu, Z. et al. Hydrophobic Modifications of Cationic Polymers for Gene Delivery. Prog. Polym. Sci. 2010, 35 (9), 1144-1162., Tseng, W.-C. et al. The Role of Dextran Conjugation in Transfection Mediated by Dextran-Grafted Polyethylenimine. J. Gene Med. 2004, 6 (8), 895-905., and Pandey, A. P. and Sawant, K. K. Polyethylenimine: A Versatile, Multifunctional Non-Viral Vector for Nucleic Acid Delivery. Mater. Sci. Eng. C 2016, 68, 904-918.), lipid design in the delivery of nucleic acid medicines (Semple, S. C. et al. Rational Design of Cationic Lipids for SiRNA Delivery. Nat. Biotechnol. 2010, 28 (2), 172-176., Allen, T. M. and Cullis, P. R. Liposomal Drug Delivery Systems: From Concept to Clinical Applications. Adv. Drug Deliv. Rev. 2013, 65 (1), 36-48.), drug delivery vehicles (Kalaska, B. et al. Heparin-Binding Copolymer Reverses Effects of Unfractionated Heparin, Enoxaparin, and Fondaparinux in Rats and Mice. Transl. Res. 2016, 177, 98-112., Kim, K. et al. Polycations and Their Biomedical Applications. Prog. Polym. Sci. 2016, 60, 18-50., and Cole, H. et al. Nanoparticle Antigen Uptake in Epithelial Monolayers Can Predict Mucosal but Not Systemic in Vivo Immune Response by Oral Delivery. Carbohydr. Polym. 2018, 190, 248-254., Tarasova, E. et al. Cytocompatibility and Uptake of Polycations-Modified Halloysite Clay Nanotubes. Appl. Clay Sci. 2019, 169, 21-30.), anti-inflammatory agents (Lee, J. et al. Nucleic Acid-Binding Polymers as Anti-Inflammatory Agents. Proc. Natl. Acad. Sci. 2011, 108 (34), 14055-14060., and Gunasekaran, Pet al. Cationic Amphipathic Triazines with Potent Anti-Bacterial, Anti-Inflammatory and Anti-Atopic Dermatitis Properties. Sci. Rep. 2019, 9 (1), 1292.) and immunomodulatory applications (Yim, H. et al. A Self-Assembled Polymeric Micellar Immunomodulator for Cancer Treatment Based on Cationic Amphiphilic Polymers. Biomaterials 2014, 35 (37), 9912-9919., and Wusiman, A. et al., Macrophage Immunomodulatory Activity of the Cationic Polymer Modified PLGA Nanoparticles Encapsulating Alhagi Honey Polysaccharide. Int. J. Biol. Macromol. 2019, 134, 730-739.). Synthetic polycations may serve as binding partners for polyanions (for example, polyphosphates, heparins, nucleic acids), and the binding behavior can be tuned for specificity with the ability to control molecular weight, geometry, and charge distribution, thereby providing attenuation of nonspecific interactions. (La, C. et al. Targeting Biological Polyanions in Blood: Strategies toward the Design of Therapeutics. Biomacromolecules 2020, 21 (7), 2595-2621.) Polycations tested for these applications include polyethyleneimine (PEI) (Liu, ibid and Pandey, ibid) poly-L-lysine (PLL) (Zauner, W. et al. Polylysine-Based Transfection Systems Utilizing Receptor-Mediated Delivery. Adv. Drug Deliv. Rev. 1998, 30 (1), 97-113.), polyallylamine (Boussif, O. et al. Synthesis of Polyallylamine Derivatives and Their Use as Gene Transfer Vectors in Vitro. Bioconjug. Chem. 1999, 10 (5), 877-883.), and polyamidoamine (PAMAM) dendrimers (Caminade, A.-M. and Majoral, J.-P. Which Dendrimer to Attain the Desired Properties? Focus on Phosphorhydrazone Dendrimers. Molecules 2018, 23 (3), 622.). Though polycations have demonstrated utility in certain settings (Godbey, W. T. et al. Poly(Ethylenimine) and Its Role in Gene Delivery. J. Controlled Release 1999, 60 (2), 149-160., Kunath, K. et al. Low-Molecular-Weight Polyethylenimine as a Non-Viral Vector for DNA Delivery: Comparison of Physicochemical Properties, Transfection Efficiency and in Vivo Distribution with High-Molecular-Weight Polyethylenimine. J. Controlled Release 2003, 89 (1), 113-125., and Lungwitz, U et al. Polyethylenimine-Based Non-Viral Gene Delivery Systems. Eur. J. Pharm. Biopharm. 2005, 60 (2), 247-266.), their highly charged state causes toxicity due to nonspecific binding to cell surfaces and circulating proteins, as well as delayed toxicity from complexing with DNA and associating with cellular processing. (Godbey, W. T, et al. Improved Packing of Poly(Ethylenimine)/DNA Complexes Increases Transfection Efficiency. Gene Ther. 1999, 6 (8), 1380-1388.) This dilemma exemplifies the conventional balance sought in the design of a polycationic therapeutic system. While the cationic charges are necessary for the targeted site and application, a preponderance of biological surfaces are polyanionic. (Bernkop-Schn0rch, A. Strategies to Overcome the Polycation Dilemma in Drug Delivery. Adv. Drug Deliv. Rev. 2018, 136-137, 62-72.). When administered into the circulatory system, nonspecific binding events result in formation of harmful clusters of cells including blood cells and other cell surfaces, and negatively charged plasma proteins, which results in toxicity. (Fischer, D. et al. A Novel Non-Viral Vector for DNA Delivery Based on Low Molecular Weight, Branched Polyethylenimine: Effect of Molecular Weight on Transfection Efficiency and Cytotoxicity. Pharm. Res. 1999, 16 (8), 1273-1279.) Factors that contribute to the toxicity of polycations include molecular weight, degree of branching, strength of charge, ionic strength in solution, zeta potential, and particle size. (Kircheis, R. et al. Polycation-Based DNA Complexes for Tumor-Targeted Gene Delivery in Vivo. J. Gene Med. 1999, 1 (2), 111-120., Alazzo, A. et al. Investigating the Intracellular Effects of Hyperbranched Polycation-DNA Complexes on Lung Cancer Cells Using LC-MS-Based Metabolite Profiling. Mol. Omics 2019, 15 (1), 77-87., and Hu, Y. et al. Kinetic Control in Assembly of Plasmid DNA/Polycation Complex Nanoparticles. ACS Nano 2019, 13 (9), 10161-10178.).
Attempts to increase the biocompatibility of polycations have been reported. (Kim, Y. et al. Polyethylenimine with Acid-Labile Linkages as a Biodegradable Gene Carrier. J. Controlled Release 2005, 103 (1), 209-219., Hu, J. et al., A Biodegradable Polyethylenimine-Based Vector Modified by Trifunctional Peptide R18 for Enhancing Gene Transfection Efficiency In Vivo. PLOS ONE 2016, 11 (12), e0166673., and Wang, W. et al. Engineering Biodegradable Micelles of Polyethylenimine-Based Amphiphilic Block Copolymers for Efficient DNA and SiRNA Delivery. J. Controlled Release 2016, 242, 71-79.). Further examples include generation of biodegradable polycations and charge shielding utilizing surface functionalization with certain functional groups or neutral polymers such as polyethylene glycol or polyglycerol. (Hellmund, M. et al. Adjustment of Charge Densities and Size of Polyglycerol Amines Reduces Cytotoxic Effects and Enhances Cellular Uptake. Biomater. Sci. 2015, 3 (11), 1459-1465., and Ghasemi, A. eta al. Synthesis and Characterization of Polyglycerol Coated Superparamagnetic Iron Oxide Nanoparticles and Cytotoxicity Evaluation on Normal Human Cell Lines. Colloids Surf Physicochem. Eng. Asp. 2018, 551, 128-136.). Whereas these methods decrease toxicity of polycations either by decreasing the charge density or by reducing the molecular size upon biodegradation, they have major limitations due to shrouding of charges resulting in decreased binding to the target site when polycations are surface modified with neutral polymers. In conventional biodegradable systems, breakdown of the polymer backbone causes decreased binding to target site after degradation. Hence, it is crucial to develop polycations that are stable in physiological conditions while providing improved biocompatibility and binding capacity. Other than shrouding the cationic charge, another approach has been to improve the biocompatibility of synthetic polycations using polymeric systems or nanosystems that differ in charge state with pH of the medium. (Thambi, T. et al. Stimuli-Sensitive Injectable Hydrogels Based on Polysaccharides and Their Biomedical Applications. Macromol. Rapid Commun. 2016.). pH-sensitive polymers typically contain simple functional groups such as amines or carboxylic acids that can be protonated or deprotonated. (Bazban-Shotorbani, S. et al. Revisiting Structure-Property Relationship of PH-Responsive Polymers for Drug Delivery Applications. J. Controlled Release 2017, 253, 46-63., and Wei, R. et al. Bidirectionally PH-Responsive Zwitterionic Polymer Hydrogels with Switchable Selective Adsorption Capacities for Anionic and Cationic Dyes. Ind. Eng. Chem. Res. 2018, 57 (24), 8209-8219.). For example, polymers composed of monomers with pendant primary, secondary, and tertiary amines adopt a protonated state at low pH. The changed state of charge is a direct result of the pendant amines accepting protons when the pH of the environment is lower than their respective pKa values, and releasing the protons when the polymers are moved to environments with pH higher than the pKa.
Synthetic polycations have been developed as targeted inhibitors of polyphosphates (polyP). (Smith, S. A. et al. Inhibition of Polyphosphate as a Novel Strategy for Preventing Thrombosis and Inflammation. Blood 2012, 120 (26), 5103-5110., Shenoi, R. A. et al. Affinity-Based Design of a Synthetic Universal Reversal Agent for Heparin Anticoagulants. Sci. Transl. Med. 2014, 6 (260), 260ra150., Travers, R. J. et al. Nontoxic Polyphosphate Inhibitors Reduce Thrombosis While Sparing Hemostasis. Blood 2014, 124 (22), 3183-3190., Kalathottukaren, M. et al. Alteration of Blood Clotting and Lung Damage by Protamine Are Avoided Using the Heparin and Polyphosphate Inhibitor UHRA. Blood 2017, 129 (10), 1368-1379, Kalathottukaren, M. T. et al. A Polymer Therapeutic Having Universal Heparin Reversal Activity: Molecular Design and Functional Mechanism. Biomacromolecules 2017, 18 (10), 3343-3358., and Kalathottukaren, M. T. et al. Comparison of Reversal Activity and Mechanism of Action of UHRA, Andexanet, and PER977 on Heparin and Oral FXa Inhibitors. Blood Adv. 2018, 2 (16), 2104-2114.) PolyPs are polymers of inorganic phosphates with densely packed anionic charges connected by high-energy phosphoanhydride bonds. PolyP plays an important role in blood clot formation by acting as a procoagulant stimulus at several enzymatic steps of the blood coagulation cascade, accelerating the clotting process. (Smith, S. A. et al. Polyphosphate Modulates Blood Coagulation and Fibrinolysis. Proc. Natd. Acad. Sci. U.S.A 2006, 103 (4), 903-908., Smith, S. A. and Morrissey, J. H. Polyphosphate Enhances Fibrin Clot Structure. Blood 2008, 112 (7), 2810-2816., Morrissey, J. H. and Smith, S. A. Polyphosphate as Modulator of Hemostasis, Thrombosis, and Inflammation. J. Thromb. Haemost. 2015, 13, S92-S97. Travers, R. J. et al. Polyphosphate, Platelets, and Coagulation. Int. J. Lab. Hematol. 2015, 37, 31-35., and Baker, C. J.; Smith, S. A.; Morrissey, J. H. Polyphosphate in Thrombosis, Hemostasis, and Inflammation. Res. Pract. Thromb. Haemost. 2019, 3 (1), 18-25.). PolyP is a potent accelerant of coagulation. (Morrissey, J. H. Tissue Factor: A Key Molecule in Hemostatic and Nonhemostatic Systems. Int. J. Hematol. 2004, 79 (2), 103-108, and Colman, R. W. and Schmaier, A. H. Contact System: A Vascular Biology Modulator With Anticoagulant, Profibrinolytic, Antiadhesive, and Proinflammatory Attributes. Blood 1997, 90 (10), 3819-3843. PolyP is thereby a therapeutic target. By targeting and inhibiting an accelerant instead of a key component of the clotting process, novel antithrombotics with lower risk of bleeding in comparison to current anticoagulation therapies may be developed. (Smith, 2006, ibid, Smith, 2008, ibid, Ruiz, ibid.) Naked cationic structures such as low molecular weight PEI and PAMAM dendrimers are effective at inhibiting polyP in vitro with strong electrostatic interactions between polyP and these polymers. (Smith, 2012, ibid, Jain, S. et al. Nucleic Acid Scavengers Inhibit Thrombosis without Increasing Bleeding. Proc. Natl. Acad. Sci. 2012, 109 (32), 12938-12943.) However, high toxicity has constrained acceptance of this approach.
Heparins, another class of polyanions with substantial therapeutic utility, are a polydisperse and heterogenous mixture of sulfated polysaccharides belonging to the glycosaminoglycan family of carbohydrates that are broadly used for their anticoagulant and antithrombotic properties. Heparin based anticoagulants, including unfractionated heparin (UFH), low-molecular weight heparins (LMWHs), enoxaparin, tinzaparin, dalteparin, and fondaparinux (a synthetic heparin pentasaccharide) are the most widely administered class of anticoagulants to the present. The antithrombotic activity of heparin arises from a specific pentasaccharide sequence that binds antithrombin (AT/AT-III), a serine protease inhibitor and an endogenous anticoagulant, thereby accelerating the inhibition of coagulation. A major adverse side effect of heparins is bleeding that causes increased mortality and hospitalization. Accordingly, heparin reversal is often required in patients under emergency conditions that require a safe and effective heparin antidote. In certain medical procedures such as cardiopulmonary bypass surgery and certain intravascular surgical procedures that require high doses of heparin anticoagulation, reversal of heparin after the surgery or procedure is routine to prevent hemorrhage.
Currently, the highly cationic polypeptide, protamine sulfate (PS), is the sole FDA-approved heparin antidote. PS functions via electrostatic binding to polyanionic heparin to form a stable ion pair that does not exhibit anticoagulant activity, leading to neutralization of the anticoagulant effects of heparin. PS has only limited efficacy in neutralizing LMWHs and has no reversal activity against fondaparinux, one of the main limitations of these otherwise superior anticoagulants to UFH. Furthermore, PS itself often lead to complications such as hypotension, excessive bleeding and hypersensitivity due to its lack of specificity. Despite being the conventional standard of care in numerous cardiac surgical procedures, heparin and PS must be carefully titrated to prevent severe bleeding. PS has unpredictable activity with a very narrow therapeutic window and has been linked to increased incidences of hypersensitivity, among other adverse outcomes.
Due to heparin's hemorrhagic and non-bleeding side effects, heparin analogues have been investigated in search of improved anticoagulant properties by developing synthetic heparinoids composed of functionalized polysaccharide backbones such as heparan sulfates, dermatan sulfates, chitosan sulfates, among many others. This work has led to a better understanding of the structural parameters that govern the properties of heparins, demonstrating that the anticoagulant and antithrombotic properties of heparinoids are directly affected by the structure of the polysaccharide macromolecules, the quantity and distribution of appended sulfated groups, and their molecular weight.
In parallel to efforts to develop viable heparin alternatives, work has focused on the development of heparin antidotes in view of the multiple limitations and complications associated with protamine. Approaches to the development of protamine alternatives include: protamine-like variants, peptide-based approaches, cationic polymers, polyvalent scaffold based-approaches, and dendritic universal heparin reversal agent (UHRA). Most of these approaches target heparin via an electrostatic binding mechanism and rely on polycationic functional groups to bind the polyanionic heparin macromolecules. However, each of these approaches has specific limitations. Synthetic structures carry an advantage over peptide-based approaches by eliminating the need for biologically sourced starting materials, and the associated risks of contamination and sensitivity-based reactions by the patient. Besides improved control over purity of the final materials, synthetic protamine alternatives also provide complete control of the final molecular structure which allows for facile modification of the heparin antidote to specifically tune the activity of the drug. The ability to tune these protamine alternatives has improved significantly as the effect of physicochemical properties on the biological activity are better understood. Although synthetic heparin antidotes are a promising route forward, the high quantity of positive charge these molecules must bear to effectively neutralize heparin has limited the utility of current synthetic protamine alternatives, with persistent side reactions and affinity to other negatively charged biological compounds that result in nonspecific interactions with blood and tissue in the body.
A third type of polyanion or polyanion assembly is extracellular nucleic acids (ecNAs) including extracellular DNA and neutrophil extracellular traps (NETs). Clinical and biochemical studies show that pathological thrombosis is initiated by the contact pathway of blood coagulation, with polyanion triggers comprising extracellular nucleic acids (ecNAs) and neutrophil extracellular traps (NETs). Although no therapies currently exist to target these polyanion triggers, blocking the triggers provides the opportunity to prevent thrombosis while sparing normal hemostasis.
Accordingly, there is a need for polyanion inhibitors that increase charge upon binding to target polyanion molecules that also exhibit minimal cationic charge at physiological pH, thereby providing reagents and therapeutics with enhanced biocompatibility and selective polyanion binding behavior.
Provided herein are compositions and methods to prevent and to treat thrombosis, to reverse the anticoagulant action of heparin, and to prevent and to treat the thrombotic and antifibrinolytic effect of nucleic acids. In particular, provided herein are compositions, methods, kits, systems and uses for switchable charge state multivalent biocompatible polycations for polyanion inhibition in blood.
In some embodiments, the present invention provides a method of preventing and/or treating thrombosis, comprising administering a macromolecular polyphosphate inhibitor (MPI) to a subject wherein the administering prevents and/or treats said thrombosis. In certain embodiments, the MPI comprises one or more cationic binding groups (CBGs,) and one or more biocompatible scaffolds. In further embodiments, the one or more CBGs is a linear alkyl amine. In still further embodiments, the one or more biocompatible scaffolds is a polyethylene glycol (PEG) scaffold and/or a polyglycerol scaffold. In particular embodiments, the MPI is MPI 8. In given embodiments, the subject is a human subject. In specific embodiments, the administering is parenteral administering.
In some embodiments, the present invention provides a method of reversing anticoagulation, comprising administering a macromolecular polyphosphate inhibitor (MPI) to a subject wherein the administering prevents and/or treats said anticoagulation. In certain embodiments, the anticoagulation is heparin anticoagulation, UFH heparin anticoagulation, enoxaparin anticoagulation, tinzaparin anticoagulation, dalteparin anticoagulation and fondaparinux anticoagulation. In further embodiments, the MPI comprises one or more cationic binding groups (CBGs,) and one or more biocompatible scaffolds. In still further embodiments, the one or more CBGs is a linear alkyl amine. In particular embodiments, the one or more biocompatible scaffolds is a polyethylene glycol (PEG) scaffold and/or a polyglycerol scaffold. In given embodiments, the MPI is MPI 2. In other embodiments, the subject is a human subject. In yet other embodiments, the administering is parenteral administering.
In some embodiments, the present invention provides a composition comprising a) one or more cationic binding groups (CBGs), b) one or more biocompatible scaffolds, and c) a pharmaceutically acceptable carrier. In certain embodiments, one or more CBGs is a linear alkyl amine. In other embodiments, the one or more biocompatible scaffolds is a polyethylene glycol (PEG) scaffold and/or a polyglycerol scaffold. In further embodiments, the composition is MPI 8. In still further embodiments, the composition is MPI 2. In particular embodiments, the present invention provides use of the preceding embodiments. In given embodiments, the present invention provides use of the preceding embodiments for the treatment of disease in a subject.
In some embodiments, the present invention provides a polymeric compound, comprising a) a hyperbranched polyglyercol core, b) a plurality of polyethylene glycol chains covalently attached to the hyperbranched polyglyercol core, and c) a plurality of linear alkylamine moieties covalently attached to the hyperbranched polyglyercol core. In certain embodiments, the linear alkylamine moieties have structures of formula (I):
or a pharmaceutically salt thereof, wherein n1 and n2 are each independently selected from 2 and 3, R1, R2, R3, and R4 are each independently selected from C1-C3 alkyl; and
is the point of attachment to the hyperbranched polyglyercol core. In further embodiments, n1 and n2 are each 2. In other embodiments, n1 and n2 are each 3. In given embodiments, R1, R2, R3, and R4 are each methyl. In particular embodiments, the linear alkylamines have a structure selected from:
or a salt thereof.
In additional embodiments, the polymeric compound has a molecular weight of about 8 kDa to about 25 kDa, or about 10 kDa to about 23 kDa. In some embodiments, the core has a number average molecular weight of about 8 kDa, about 9 kDa, about 10 kDa, about 11 kDa, about 12 kDa, about 13 kDa, about 14 kDa, about 15 kDa, about 16 kDa, about 17 kDa, about 18 kDa, about 19 kDa, about 20 kDa, about 21 kDa, about 22 kDa, about 23 kDa, about 24 kDa, or about 25 kDa, or any range therebetween. In specific embodiments, the polymeric compound has an average of about 10 to about 25 linear alkylamine moieties covalently attached to the hyperbranched polyglyercol core, e.g., an average of about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, or about 25 linear alkylamine moieties covalently attached to the core.
Negative control: PPP with tricine buffer. Positive control: PPP with polyP (700 monomer units, 20 μM monomer concentration). a) Actual clot time of positive and negative controls, showing a significant decrease in clot time upon addition of polyP. b)-c) Calculated percentages of clotting times to demonstrate polyP inhibition. The dotted line indicates the value for plasma incubated with buffer (i.e., buffer control).
To facilitate an understanding of the present disclosure, a number of terms and phrases are defined below:
As used herein, the term “alkyl” means a straight or branched saturated hydrocarbon chain, e.g., containing 1 to 6 carbon atoms (C1-C6 alkyl), 1 to 4 carbon atoms (C1-C4 alkyl), 1 to 2 carbon atoms (C1-C3 alkyl), or 1 to 2 carbon atoms (C1-C2 alkyl). Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and n-hexyl.
As used herein, the term “hyperbranched polyglycerol” refers to a polymeric material prepared by ring-opening multibranching polymerization of glycidol using a 1,1,1-tris(hydroxymethyl)propane initiator.
As used herein, the term “subject” refers to any animal (e.g., a mammal), including, but not limited to, humans, non-human primates, rodents, and the like, which is to be the recipient of a particular treatment. Typically, the terms “subject” and “patient” are used interchangeably herein in reference to a human subject.
As used herein, the term “non-human animals” refers to all non-human animals including, but not limited to, vertebrates such as rodents, non-human primates, ovines, bovines, ruminants, lagomorphs, porcines, caprines, equines, canines, felines, aves, etc.
As used herein, the term “cell culture” refers to any in vitro culture of cells. Included within this term are continuous cell lines (e.g., with an immortal phenotype), primary cell cultures, transformed cell lines, finite cell lines (e.g., non-transformed cells), and any other cell population maintained in vitro.
As used herein, the term “in vitro” refers to an artificial environment and to processes or reactions that occur within an artificial environment. In vitro environments can consist of, but are not limited to, test tubes and cell culture. The term “in vivo” refers to the natural environment (e.g., an animal or a cell) and to processes or reaction that occur within a natural environment.
The terms “test compound” and “candidate compound” refer to any chemical entity, pharmaceutical, drug, and the like that is a candidate for use to treat or prevent a disease, illness, sickness, or disorder of bodily function (e.g., thromboembolism, atherosclerosis, cancer). Test compounds comprise both known and potential therapeutic compounds. A test compound can be determined to be therapeutic by screening using the screening methods of the present disclosure.
As used herein, the term “sample” is used in its broadest sense. In one sense, it is meant to include a specimen or culture obtained from any source, as well as biological and environmental samples. Biological samples may be obtained from animals (including humans) and encompass fluids, solids, tissues, and gases. Biological samples include blood products, such as plasma, serum and the like. Environmental samples include environmental material such as surface matter, soil, water, and industrial samples. Such examples are not however to be construed as limiting the sample types applicable to the present disclosure.
As used herein, the term “effective amount” refers to the amount of a compound (e.g., a compound described herein) sufficient to effect beneficial or desired results. An effective amount can be administered in one or more administrations, applications or dosages and is not limited to or intended to be limited to a particular formulation or administration route.
As used herein, the term “co-administration” refers to the administration of at least two agent(s) or therapies to a subject. In some embodiments, the co-administration of two or more agents/therapies is concurrent. In other embodiments, a first agent/therapy is administered prior to a second agent/therapy. Those of skill in the art understand that the formulations and/or routes of administration of the various agents/therapies used may vary. The appropriate dosage for co-administration can be readily determined by one skilled in the art. In some embodiments, when agents/therapies are co-administered, the respective agents/therapies are administered at lower dosages than appropriate for their administration alone. Thus, co-administration is especially desirable in embodiments where the co-administration of the agents/therapies lowers the requisite dosage of a known potentially harmful (e.g., toxic) agent(s).
As used herein, the term “pharmaceutical composition” refers to the combination of an active agent with a carrier, inert or active, making the composition especially suitable for diagnostic or therapeutic use in vivo, or ex vivo.
As used herein, the term “target binding agent” (e.g., “target-binding protein” or protein mimetic such as an aptamer) refers to proteins that bind to a specific target. “Target-binding proteins” include, but are not limited to, MPIs, immunoglobulins, including polyclonal, monoclonal, chimeric, single chain, single domain, scFv, minibody, nanobody, and humanized antibodies.
As used herein, the term “toxic” refers to any detrimental or harmful effects on a cell or tissue as compared to the same cell or tissue prior to the administration of the toxicant.
As uses herein, “thrombosis” is the formation of a blood clot or “thrombus” within a blood vessel. In certain conditions, thrombosis arises from an inherited condition including, for example, factor V Leiden, prothrombin gene mutation, deficiencies of natural proteins that prevent clotting (for example, antithrombin, protein C and protein S), elevated levels of homocysteine, elevated levels of fibrinogen or dysfunctional fibrinogen (dysfibrinogenemia), elevated levels of factor VIII (and other factors including factor IX and XI), and abnormalities in the fibrinolytic system, including hypoplasminogenemia, dysplasminogenemia and elevation in levels of plasminogen activator inhibitor (PA-1). In other conditions, thrombosis is associated with acquired hypercoagulable conditions including, for example, cancer, medications used to treat cancer (e.g., taroxifen, bevacizumab, thalidomide and lenalidomide), trauma or surgery, central venous catheter placement., obesity, pregnancy, supplemental estrogen use including oral contraceptive pills (birth control pills), hormone replacement therapy, prolonged bed rest or immobility, heart attack, congestive heart failure, stroke and other illnesses that lead to decreased physical activity, heparin-induced thrombocytopenia (i.e., decreased platelets in the blood due to heparin or low molecular weight heparin preparations), lengthy airplane travel, antiphospholipid antibody syndrome, previous history of deep vein thrombosis or pulmonary embolism, myeloproliferative disorders such as polycythemia vera or essential thrombocytosis., paroxysmal nocturnal hemoglobinuria, inflammatory bowel syndrome, HIV/AIDS and nephrotic syndrome among other inherited and acquired disorders of coagulation.
Provided herein are compositions and methods to prevent and to treat thrombosis, to reverse the anticoagulant action of heparin, and to prevent and to treat the thrombotic and antifibrinolytic effect of nucleic acids. In particular, provided herein are compositions, methods, kits, systems and uses for switchable charge state multivalent biocompatible polycations for polyanion inhibition in blood.
In experiments conducted in the course of development of certain embodiments of the present invention, biocompatible polycationic inhibitors were developed with high binding affinity to therapeutically relevant polyanions in blood (e.g., polyphosphates, heparins and extracellular nucleic acids) that provide selectivity and enhanced binding based on switchable protonation states and localized proton recruitment without the need for an external trigger. The polycations have low cationic charge states at physiological pH, while maintaining strong binding to different biologically relevant polyanions with high biocompatibility provided by polyglycerol and polyethylene glycol scaffolds. The cationic binding groups (CBGs) are based on pKa profiles of amines and spacing between the nitrogen atoms and are conjugated to the polymer scaffold. A library of polycations was synthesized using cationic ligands comprising novel combinations of strongly (pKa >8) and weakly (pKa ˜6-7) basic amine ligands presented on a semi-dendritic polymer scaffold. The protonation behavior of the new polycations has been characterized utilizing potentiometric titrations and speciation analyses. The binding affinities of the library of polycations has been confirmed using surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) analyses. The switchable protonation states of cationic ligands on these polycations have been established using potentiometry and ITC analyses, and 31P NMR analyses. Clotting and cell-based assays provide evidence of enhanced biocompatibility. We demonstrate the therapeutic utility of the polycation platforms of the present invention using three different targets: inhibition of polyphosphates, inhibition of extracellular nucleic acids, and reversal of the action of heparin. The therapeutic activities and safety of the molecules of the present invention are demonstrated both in vitro and in vivo. These results show that improved binding to polyanions has been achieved without excessive charge on the polycation structure at physiological pH via switchable protonation states, with improved biocompatibility and selectivity when compared to conventional polyP inhibitors. (Smith, 2012, ibid, Shenoi, ibid, Travers, ibid, Kalathottukaren and Abraham, 2017, ibid, Jain, ibid.)
Polyphosphate (PolyP) Inhibitors with Switchable Protonation State Prevent Thrombosis without Bleeding Risk
In experiments conducted in the course of development of certain embodiments of the present invention, optimization of polycationic drug systems and reduction of toxicity has been demonstrated. Conventional systems rely on a stealth cationicity to shield their polycationic character until they have reached the target site. Selective local unleashing of polycationic substructures typically requires a trigger, either chemical pH changes which are useful to target tumors (Kato, Y. et al., Acidic Extracellular Microenvironment and Cancer. Cancer Cell Int. 2013, 13 (1), 89.) inflammatory tissue (Trevani, A. S. et al. Extracellular Acidification Induces Human Neutrophil Activation. J. Immunol. 1999, 162 (8), 4849-4857., and Dubos, R. J. The Micro-Environment of Inflammation or Metchnikoff Revisited. Lancet 1955, 1-5.0, lipid nanoparticle-siRNA delivery systems (Semple, ibid, Allen, ibid), or physical triggers such as light (Hu, L.-C. et al. Light-Triggered Charge Reversal of Organic-Silica Hybrid Nanoparticles. J. Am. Chem. Soc. 2012, 134 (27), 11072-11075.), temperature (Don, T.-M. et al. Temperature/PH/Enzyme Triple-Responsive Cationic Protein/PAA-b-PNIPAAm Nanogels for Controlled Anticancer Drug and Photosensitizer Delivery against Multidrug Resistant Breast Cancer Cells. Mol. Pharm. 2017, 14 (12), 4648-4660.), or magnetism (Wong, J. E. et al. Dual-Stimuli Responsive PNiPAM Microgel Achieved via Layer-by-Layer Assembly: Magnetic and Thermoresponsive. J. Colloid Interface Sci. 2008, 324 (1), 47-54.) While such systems find utility for their specific drug targets, they require an external trigger to fulfill their intended task. In some embodiments of the present invention, the trigger for increasing the cationic charge is the target binding site itself: the intended polyanion.
Using an adaptable design approach, we developed polyP inhibitors with improved activity and substantially enhanced biocompatibility. The improvements were achieved via a two-pronged approach: 1) using a series of cationic binding groups with switchable protonation states, and 2) a biocompatible scaffold. The selective design of cationic binding groups structures for their amine pKa values, charge spacing to match their targeted polyanion and length of linker which may affect their flexibility. By embedding the cationic binding groups to a biocompatible scaffold known to preclude non-specific interactions, polycations are generated with low charge density compared conventional polycation inhibitors of polyP (Smith, 2012, ibid, Travers, ibid, Kalathottukaren and Abraham, ibid), while further preventing nonspecific binding via steric repulsion of larger polyanionic macromolecules with lower charge density. Furthermore, this approach facilitated specific tuning of the macromolecular polyanion inhibitor (MPI) efficacy by synthesis of a library of compounds by varying backbone size, CBG structure, and the quantity and density of charge.
The library of potential polyP inhibitors was characterized by several methods to select optimal inhibitors. Assessment of the number of cationic binding groups per MPI was accomplished via conductometric titration, a factor governing the biocompatibility of the inhibitors, coupled with determination of their protonation behavior measured via potentiometric titration. This measurement provides an approximation of the state of charge of each MPI candidate examined. With the microstructure of the MPIs generated, we determined the effect of empirically measured characteristics on the binding behavior of the MPIs.
MPI binding behavior with polyP, an important newly identified antithrombotic target, was characterized via two principal techniques: 1) high-throughput surface plasmon resonance experiment; and 2) isothermal titration calorimetry. The characterization demonstrated that MPIs generated demonstrate strong binding to multiple lengths of polyP. While MPIs carry significantly less charge than previous universal heparin reversal agent (UHRA) inhibitors (ca. 50%-85% of UHRA charge), the binding and corresponding Kd did not suffer a significant loss. All measured binding affinities were on the sub-micromolar range with minimal differences. The strongest binding behavior is observed with the more charged Me6TREN ligand, a ligand shown in further experiments to demonstrate lower biocompatibility due to a higher state of charge under physiological conditions. Of two CBGs, CBG II showed slightly enhanced binding behavior attributed to an inter-charge spacing that more closely matches that of the polyP partner. Isothermal titration calorimetry was then performed on a subset of the MPIs. For all binding pairs of MPI and polyP tested, a one-to-one stoichiometry was found, indicating a stable bound complex with no evidence of precipitation, a common occurrence in polycationic therapeutics. (Bernkop-Schnurch, ibid.) While the binding affinity increased with an increase in charge density on the MPI, the IC50 remained similar over the series of inhibitors indicating that only a subset of the charges on the MPI participate in binding.
Using CBGs with multiple protonatable sites, MPIs were generated that exhibited a sufficiently low quantity of charge and charge density at physiological pH to remain biocompatible while maintaining the capacity to adopt a more highly charged state when bound to polyP. This switchable protonation behavior is analogous to similar processes observed in protein-ligand binding events in which the microenvironment of the binding pocket is more stable with a protonated ligand and therefore the ligand adopts a protonated state, recruiting a proton from the surroundings. (Neeb, M. et al. Chasing Protons: How Isothermal Titration Calorimetry, Mutagenesis, and PKa Calculations Trace the Locus of Charge in Ligand Binding to a TRNA-Binding Enzyme. J. Med. Chem. 2014, 57 (13), 5554-5565., Antosiewicz, J. et al. The Determinants of PKas in Proteins. Biochemistry 1996, 35 (24), 7819-7833., and Graffner-Nordberg, M. et al. Computational Predictions of Binding Affinities to Dihydrofolate Reductase: Synthesis and Biological Evaluation of Methotrexate Analogues. J. Med. Chem. 2000, 43 (21), 3852-3861.) Proton recruitment during the binding process is illustrated in
The enhanced strength of the MPI-polyP bound state over more simplified small molecule cationic inhibitors (e.g., CBG I) with polyP was confirmed via 31P NMR studies that demonstrated the equilibrium binding process observed for small molecule inhibitors that is not observed with the MPI. Instead, the high strength MPI-polyP bond results in distinct peaks for bound and unbound phosphates in this NMR experiment as the MPI is too tightly bound to rapidly equilibrate. Furthermore, observation of the phosphorus in polyP over the course of binding to MPI indicated no appearance of monophosphate, diphosphate or triphosphate peaks created, indicating that MPI are binding to the negative charges on the polyP chain without hydrolyzing polyP into smaller fragments. These observations support a further advantage of MPI over therapeutic enzymes that degrade polyP (Labberton, L. et al. Neutralizing Blood-Borne Polyphosphate in Vivo Provides Safe Thromboprotection. Nat. Commun. 2016, 7, 12616.). Specific enzymes may degrade phosphate units from other sources of phosphate in the body while the specificity of MPI is inherent to the polyanionic character of polyP.
The switchable protonation states achieved with the newly developed CBGs allow for precise specificity towards polyP while minimizing nonspecific interactions between the MPIs and negatively charged biomolecules, thereby resulting in enhanced biocompatibility. Enhanced biocompatibility was demonstrated by a series of tests to measure the effect of the polycationic drug candidates on hemostasis. Pooled plasma was treated with the MPI candidates as well as a buffer control to demonstrate no change in the lag time prior to clotting, showing that MPI addition alone does not have adverse effects on clotting behavior. Cationic therapeutics such as protamine sulfate performed considerably worse than MPI candidates, with a near 3-fold increase in clot time compared to that of the buffer control. This drawback is evidenced by the bleeding complications in patients who have been administered protamine sulfate without careful monitoring and titration. (Cobel-Geard, R. J. and Hassouna, H. I. Interaction of Protamine Sulfate with Thrombin. Am. J Hematol. 1983, 14 (3), 227-233., Wolberg, A. S. Thrombin Generation and Fibrin Clot Structure. Blood Rev. 2007, 21 (3), 131-142., and Ni Ainle, F. et al. Protamine Sulfate Down-Regulates Thrombin Generation by Inhibiting Factor V Activation. Blood 2009, 114 (8), 1658-1665.) Moreover, when used as a polyP inhibitor, MPIs of the present invention exhibit potent inhibition of procoagulant polyP activity in human plasma, a representation of their behavior in vivo as an antithrombotic.
To test the efficacy of each MPI as an inhibitor of bacterial-sized polyP and platelet-sized polyP in combining the IC50 values and the inherent influence of MPI on tissue factor pathway-initiated clotting, MPI 1, MPI 6 and MPI 8 were tested as antithrombotic therapeutics. The IC50 values did not correlate directly with increased charge density. Increasing charge density on certain MPI molecules (e.g., MPI 1, 2 and 3 with increasing charge density respectively) did not result in an increase in the efficacy of binding polyP, indicating binding behavior in which not all cationic ligands are necessarily interacting with the polyP, and highlighting the importance of CBG selection to optimally match the structure of polyP. MPI 1, 6, and 8, exhibit properties of a preferred polyP inhibitor with antithrombotic applications in vitro with minimal influence on clotting in the absence of added polyP. These MPIs provide a significant advantage in their ability to target multiple therapeutically relevant sizes of polyP by taking advantage of the strength of multivalent interactions between the two polyions, while mitigating nonspecific interactions with the reduced quantity of positive charge on MPI. Compared to other methods of inhibiting the effects of polyP such as enzymatic approaches, the MPIs of the present claims provide a significant advantage. MPIs of the present invention reverse the procoagulant effects of multiple sizes of polyP in keeping with the multivalency presented. This indicates that MPIs of the present invention target bacterial and platelet polyP without interference from other phosphate-containing compounds, in comparison to enzymatic degradation approaches that may cleave phosphates from other compounds. (Labberton, ibid.)
MPIs of the present invention demonstrated no interference with blood components including platelets, and were tested in more complex systems (e.g., whole blood) to probe whether these compounds have adverse effects on whole blood clotting. Whole blood is a preferred model system because it includes a full spectrum of biomolecules and cells that MPIs will encounter when used as an antithrombotic therapeutic in humans. Human whole blood is composed of multiple anionic components that typically lead to nonspecific interactions with unprotected polycations that have been previously investigated as drug candidates. Specifically, cationic PAMAM dendrimers and PEI have been shown to interact with and activate platelets and induce cell toxicity. (Pretorius, E. et al. Blood Clot Parameters: Thromboelastography and Scanning Electron Microscopy in Research and Clinical Practice. Thromb. Res. 2017, 154, 59-63.) MPIs of the present invention differ from conventional cationic polymers because they have minimized charge density while in circulation. This feature combined with cationic ligands via a carefully designed protonation state which is paired with a highly biocompatible polymer scaffold and PEG corona, provide new-generation inhibitors with significantly improved safety. The result of these measures has enhanced whole blood compatibility that is unrivaled by other polycationic drug candidates. (Kalathottukaren and Abraham, ibid.) The minimized effect on whole blood clotting is observed by the minimized change in clot time relative to buffer control in whole blood, measured via ROTEM, as well as by minimized change in maximum clot firmness upon MPI addition. Prior polyP inhibitors, UHRA-8 and UHRA-10, exhibited a significant increase in clot time and a decrease in maximum clot firmness, indicating that both these compounds interfere with the clotting process and the final clot stability. Because human whole blood more closely represents components that MPI may encounter in a therapeutic setting, the compatibility with whole blood clotting denotes improved biocompatibility.
The potential effect of the MPI 8 on the stability of the formed fibrin clots was assessed to observe potential changes in clot morphology and microstructure. The participation of MPIs of the present invention in clot formation and its resulting effects can be observed directly on the thickness and morphology of the generated fibrils as fibrinogen is converted to fibrin. Frequently, thickening of fibrin fibrils causes instability in the final clot, resulting in increased susceptibility to clot lysis which can in turn increase the risk of bleeding as a direct result of the abnormal clot structure. (Shenkman, B. et al. In Vitro Evaluation of Clot Quality and Stability in a Model of Severe Thrombocytopenia: Effect of Fibrinogen, Factor XIII and Thrombin-Activatable Fibrinolysis Inhibitor. Blood Transfus. 2014, 12 (1), 78-84.) Based on SEM measurements, a minimal difference was observed between clots generated in the presence of MPI 8 compared to clots generated in buffer control, further highlighting the minimal nonspecific interactions between polycations of the present invention and blood components that would potentially cause undesired activity in vivo. This was further evidenced by clots formed in the presence of conventional anticoagulants, that demonstrated increased clot turbidity attributed to increased fibril thickness that result in increased sensitivity of the clots formed to lysis. (Nenci, G. et al. Fibrin Clots Obtained from Plasma Containing Heparin Show a Higher Sensitivity to T-PA-Induced Lysis. Blood Coagul. Fibrinolysis 1992, 3 (3), 279-286., Collen, A. et al. Unfractionated and Low Molecular Weight Heparin Affect Fibrin Structure and Angiogenesis in Vitro. Cancer Res. 2000, 60 (21), 6196-6200.).
PolyP itself increases fibrin fiber thickness, leading to clots that are more resistant to fibrinolysis (Morrissey, ibid.) While the amount of polyP present in the physiological setting (up to approximately 3 μM in whole blood following complete platelet activation) may show less pronounced effects, changes in fibril thickness have shown significant thrombotic risk. (Wolberg, A. S. et al. Prothrombin Results in Clots with an Altered Fiber Structure: A Possible Mechanism of the Increased Thrombotic Risk. Blood 2003, 101 (8), 3008-3013., and Cooper, A. V. et al. Fibrinogen Gamma-Chain Splice Variant Γ′ Alters Fibrin Formation and Structure. Blood 2003, 102 (2), 535-540.) Notably, the MPI 8 reverses the polyP effect without altering the final clot structure, leaving a clot with fibrin fibrils similar to the buffer control, and providing a strong indication that MPIs of the present invention may reverse polyP activity without causing adverse effects on the final clot. In some embodiments of the present invention, therapeutics that modulate the degree of interaction between polyP and the fibrin clot directly modulate the final clot structure, its stability and lysis, and the physical properties of the resulting clot.
To test the properties and function of the MPIs of the present invention in vivo, the antithrombotic activity of MPIs of the present invention were tested in two mouse thrombosis models. Two additional mouse models were used to determine whether the MPIs produced undesired bleeding effects using a bleeding and toxicity model. The activity of the MPIs of the present invention were tested for antithrombotic activity via the rate and quantity of platelet and fibrin accumulation at the site of injury upon laser injury to cremaster arterioles. Mice administered with MPI 1 and MPI 6 demonstrated significantly less platelet accumulation. Mice administered 100 mg/kg MPI 8 demonstrated significantly less fibrin and platelet accumulation upon injury compared to the mice administered with saline. The ability of MPI 8 to prevent thrombus formation in a carotid artery model was tested wherein artery patency is monitored by Doppler flow probe following topical application of FeCl3, inducing injury. Percent patency was monitored over time (30 minutes) and mice were administered with either MPI 8, saline or UHRA-10 (
Experiments conducted in the development of the present invention indicate that MPI 8 does not influence normal hemostasis processes and is less likely to be associated with bleeding as compared to other antithrombotic agents. MPI 8 does not induce bleeding even at the high concentrations of 300 mg/kg, whereas previous studies have shown UHRA-10 does induce bleeding in mice at lower concentrations. (Travers, ibid.) The mean of bleeding times after administration of UIRA-10 was not significantly different from the saline control; however, the strong deviation (coefficient of variation of 49%) in the bleeding times indicates an erratic dose behavior for this compound. The more predictable bleeding time for MPI 8 similar to the saline control further indicates its advantages. MPIs of the present invention provide marked safety based on both acute and chronic toxicity studies in mice. These data show that even at the very high dose of 500 mg/kg, MPI 8 did not induce any changes in the enzyme levels, which would indicate cell/tissue damage, indicating that MPI 8 is well tolerated. These data also indicate that MPI 8 is the most non-toxic polycation reported in the literature to date. Compared to polycationic PS, MPI 8 provides much improvement over the toxic complications with a lethal dose of PS of 30 mg/kg in mice. (Shenoi, R. A. et al. Affinity-Based Design of a Synthetic Universal Reversal Agent for Heparin Anticoagulants. Sci. Transl. Med 2014, 6 (260), 260ra150.) In turn, PS is cytotoxic to cells and potentiates tissue damage. (Sokolowska, E. et al. The Toxicology of Heparin Reversal with Protamine: Past, Present and Future. Expert Opin. Drug Metab. Toxicol. 2016, 12 (8), 897-909.) Even small doses may result in capillary thrombosis and severe damage to the glomerular and tubular epithelium (located in the kidney), (Messina, A. et al. Protamine Sulphate-Induced Proteinuria: The Roles of Glomerular Injury and Depletion of Polyanion. J. Pathol. 1989, 158 (2), 147-156.), and heparin-protamine complexes cause distinct hemorrhage and pulmonary edema in the lungs of rats. (Cook, J. J. et al. Platelet Factor 4 Efficiently Reverses Heparin Anticoagulation in the Rat without Adverse Effects of Heparin-Protamine Complexes. Circulation 1992, 85 (3), 1102-1109.) Compared to other cationic polymers, PAMAM and polypropylenimine (PPI) from generations G3 to G5 have shown to be highly cytotoxic to cells. (Bodewein, L. et al. Differences in Toxicity of Anionic and Cationic PAMAM and PPI Dendrimers in Zebrafish Embryos and Cancer Cell Lines. Toxicol. Appl. Pharmacol. 2016, 305, 83-92.) In particular, high molecular weight polycations such as dendritic and hyperbranched polylysine of >20 kDa demonstrate acute cytotoxicity via direct cell membrane disruption. (Kadlecova, Z. et al. Comparative Study on the In Vitro Cytotoxicity of Linear, Dendritic, and Hyperbranched Polylysine Analogues. Biomacromolecules 2012, 13 (10), 3127-3137.) Polycations such as poly(L-lysine) and polydiallyldimethylammonium chloride (PDDAC) also cause acute toxicity in animals. At lethal doses, mice showed respiratory distress and convulsive movements before dying and the maximal non-toxic dose was low: 10 mg/kg for 24 kDa poly(L-lysine); 5 mg/kg for 124 kDa poly(L-lysine); and only 4 mg/kg for PDDAC. (Moreau, ibid.) These data provide a clear indication of the high biocompatibility of MPIs of the present invention in contact with more complex systems in the setting of antithrombotic therapy.
Compared to current polyP inhibitors, MPIs of the present invention provide multiple advantages. Conventional polycations (e.g., poly(lysine), PEI and PAMAM) are cytotoxic and cause adverse effects through their strong nonspecific interactions with other blood components. (Jones, C. F. et al. Cationic PAMAM Dendrimers Aggressively Initiate Blood Clot Formation. ACS Nano 2012, 6 (11), 9900-9910., and Hu, et al. Cardiovascular Toxicity Assessment of Poly (Ethylene Imine)-Based Cationic Polymers on Zebrafish Model. J. Biomater. Sci. Polym. Ed. 2017, 28 (8), 768-780.) Peptide-based approaches such as poly-L-lysine may alter fibrin fibril thickness resulting in an increased risk of thrombosis. (Shenkman, B. et al. In Vitro Evaluation of Clot Quality and Stability in a Model of Severe Thrombocytopenia: Effect of Fibrinogen, Factor XIII and Thrombin-Activatable Fibrinolysis Inhibitor. Blood Transfus. 2014, 12 (1), 78-84.) Another approach to reverse the effects of polyP includes uses polyphosphatase-based approaches, for example, use of a polyP degrading enzyme such as recombinant Escherichia coli exopolyphosphatase (PPX) and a PPX variant lacking domains 1 and 2 (PPX_D12, which binds polyP but does not degrade it). (Labberton, ibid.) However, degradation of polyP by the PPXenzyme may take substantial time to act, and also requires that the terminal phosphate(s) of polyP are not complexed with proteins or other substances. MPIs of the present invention do not have these adverse interactions, but rather demonstrate hemocompatibility and a high dose tolerance in mice. Because MPIs of the present invention inhibit polyP through an electrostatic neutralization without degrading polyP, they do not exhibit nonspecific interactions with critical small-molecule, phosphate-containing compounds.
Conventional anticoagulants such as heparin or LMWHs are effective at preventing venous thromboembolism (VTE) and therefore often administered to patients that are at high risk for VTE. (Schünemann, H. J. et al. American Society of Hematology 2018 Guidelines for Management of Venous Thromboembolism: Prophylaxis for Hospitalized and Nonhospitalized Medical Patients. Blood Adv. 2018, 2 (22), 3198-3225) who may further experience bleeding issues. Direct oral anticoagulants (DOACs) have been developed, which target factor Xa or thrombin, downstream enzymes in the coagulation cascade. (Weitz, J. I. and Fredenburgh, J. C. Factors XI and XII as Targets for New Anticoagulants. Front. Med. 2017, 4, 19.) Since 2010, DOACs have been FDA-approved and were considered to have good overall safety profiles and low bleeding risk. However, recent studies show that DOACs may not provide a lower bleeding risk to LMWH, highlighting the continued need for a safe and effective antithrombotic agent. (Tao, D. L. et al. The Efficacy and Safety of DOACs versus LMWH for Cancer-associated Thrombosis: A Systematic Review and Meta-analysis. Eur. J Haematol. 2020, 105 (3), 360-362., and Neumann, I. et al. DOACs vs LMWHs in Hospitalized Medical Patients: A Systematic Review and Meta-Analysis That Informed 2018 ASH Guidelines. Blood Adv. 2020, 4 (7), 1512-1517.) To the present, there is no effective anticoagulant drug available that does not present bleeding risks, with targeting newly identified polyanions as an attractive approach. (La, ibid.) Targeting polyP for its ability to prevent the acceleration of coagulation provides a pathway for the development of safer antithrombotic strategies. (Weitz, ibid.) The current absence of available therapeutics to target new pathologies such as those involving polyP or other polyanions underscores the value of MPIs of the present invention. (La, ibid, Weitz, ibid, Connors, J. M. and Levy, J. H. COVID-19 and Its Implications for Thrombosis and Anticoagulation. Blood 2020, 135 (23), 2033-2040., and Rangaswamy, C. et al. Polyanions in Coagulation and Thrombosis: Focus on Polyphosphate and Neutrophils Extracellular Traps. Thromb. Haemost. 2020.) Compared to conventional technologies (Smith, 2012, ibid, Jain, ibid, Labberton, ibid.) MPIs of the present invention provide therapeutics with nontoxic thromboprotection without bleeding risk and toxicity.
Other approaches to the development of biocompatible, effective cationic therapeutic agents including PEGylation (Veronese, F. M. Peptide and Protein PEGylation: A Review of Problems and Solutions. Biomaterials 2001, 22 (5), 405-417., and Turecek, P. L. et al PEGylation of Biopharmaceuticals: A Review of Chemistry and Nonclinical Safety Information of Approved Drugs. J. Pharm. Sci. 2016, 105 (2), 460-475.), HPG-conjugation (Frey, H. and Haag, R. Dendritic Polyglycerol: A New Versatile Biocompatible Material. Rev. Mol. Biotechnol. 2002, 90 (3), 257-267., Kurniasih, I. N. Synthesis and Transport Properties of New Dendritic Core-Shell Architectures Based on Hyperbranched Polyglycerol with Biphenyl-PEG Shells. New J. Chem. 2012, 36 (2), 371-379., Paulus, F. et al Structure Related Transport Properties and Cellular Uptake of Hyperbranched Polyglycerol Sulfates with Hydrophobic Cores. Polym. Chem. 2014, 5 (17), 5020-5028., and Abbina, S. et al. Hyperbranched Polyglycerols: Recent Advances in Synthesis, Biocompatibility and Biomedical Applications. J. Mater. Chem. B 2017, 5 (47), 9249-9277.), and the use of a polymeric shielding layer, do not comprise switchable polycationic inhibitors that do not require an extrinsic change in conditions, such as a change in the environmental pH or temperature. In experiments conducted in the development of certain embodiments of the present invention, we discovered a series of cationic binding groups with protonation states that vary significantly with shifts in dielectric strength at physiological pH. We further show that polycationic therapeutics adopt a highly charged state during binding while adopting a minimally charged state during free circulation. We developed highly effective polyP inhibitors that exhibit high polyP binding activity but with minimal non-specific binding that is otherwise endemic to polycationic macromolecules. Using this design methodology, we demonstrate that targeted polycationic inhibitors provide a new class of therapeutics that minimizes risks attendant to conventional drugs and technologies with high biocompatibility.
Through comprehensive physical characterizations, we have demonstrated new methods to design, manufacture and administration of new, safe and effective macromolecular polyanion inhibitors. Using specifically designed cationic binding groups, we show that MPIs with switchable protonation behavior of the present invention target polyP without undesirable nonspecific interactions in blood. The synthetic route to the MPIs of the present invention allows for rapid generation of a library of inhibitors available for high throughput screening and optimization. ITC and SPR experiments demonstrate that the new polyP inhibitors possess surprisingly high binding affinity towards diverse biologically relevant chain lengths of polyP in view of a low charge density at unbound physiological conditions. In turn, experiments in human plasma demonstrate that MPIs of the present invention provide high polyP inhibition activity in reversing the procoagulant behavior of polyP at sub-micromolar concentrations. The new combination of weakly acidic amine structures on a biocompatible scaffold maintains specificity towards polyP with a change in protonation state upon inhibitor binding. Cationic structures of the present invention demonstrate selectivity for polyP with no interference with other anionic blood components such as proteins and platelets which are activated by other cationic compounds. MPIs of the present invention exhibit minimal cationic charge density at physiological pH that increases significantly upon binding to polyP with improved biocompatibility and binding behavior.
As the need for a safe and effective heparin reversal agent expands, efforts have focused on several possible solutions to the challenges faced by protamine sulfate. These efforts include the development of protamine-like compounds (Byun, Y. et al. Low Molecular Weight Protamine: A Potential Nontoxic Heparin Antagonist. Thromb. Res. 1999, 94 (1), 53-61.), functionalized protamine derivatives (Kaminski, K et al. Cationic Derivatives of Dextran and Hydroxypropylcellulose as Novel Potential Heparin Antagonists. J. Med. Chem. 2011, 54 (19), 6586-6596.), and peptide-based approaches (Liu, Q. et al. Serum Albumin-Peptide Conjugates for Simultaneous Heparin Binding and Detection. ACS Omega 2019, 4 (26), 21891-21899.). While low molecular weight protamine (LMWP) with fragment sizes of approximately 1500 Da, maintain heparin neutralization properties, the pharmacological and toxicological profiles of this heparin antidote are unresolved. (He, H. et al. Low Molecular Weight Protamine (LMWP): A Nontoxic Protamine Substitute and an Effective Cell-Penetrating Peptide. J. Controlled Release 2014, 193, 63-73.). As alternatives to analogs of conventional protamine-based antidotes, cationic polymers provide heparin reversal with preferred properties and function. Because cationic polymers are synthetic, it is possible to control the final structure of the drug candidates while ensuring purity of the final materials. Improved control results in predictable pharmacokinetic profiles and removes risks that arise from compounds derived from biological sources. Recent examples of synthetically derived cationic polymers have been shown to be effective in vitro in the reversal of select heparins (Kalaska, ibid, Kaminski, ibid, and Kalaska, B. et al. Nonclinical Evaluation of Novel Cationically Modified Polysaccharide Antidotes for Unfractionated Heparin. PLOS ONE 2015, 10 (3), e0119486.), at the expense of abnormal bleeding, cell apoptosis, cell death, and histopathological changes including renal abnormalities and lung congestion due to the high density of cationic charges present. (Jones, ibid, Sokolowska, E. et al. The Toxicokinetic Profile of Dex40-GTMAC3-a Novel Polysaccharide Candidate for Reversal of Unfractionated Heparin. Front. Pharmacol. 2016, 7, 60., and Labieniec-Watala, M. and Watala, C. PAMAM Dendrimers: Destined for Success or Doomed to Fail? Plain and Modified PAMAM Dendrimers in the Context of Biomedical Applications. J. Pharm. Sci. 2015, 104 (1), 2-14.).
In experiments conducted in the development of the present invention, MPIs were tested as safer and more effective heparin reversal agents. The unique combination of cationic binding groups on a biocompatible scaffold enables a selective change in protonation state upon MPI binding to targeted anionic binding partners. The protonation properties and selective protonation properties of MPIs have been described. A change in overall charge upon polyanion binding provides selective binding and overcomes energetic barriers resulting in increased efficiency. In experiments conducted in the development of the present invention, we developed novel heparin antidotes by generating and screening a library of MPI molecules. While switchable protonation is present in most MPI candidates studied, MPI 2 generates multiple preferred activities including potent universal heparin neutralization, hemocompatibility, and no effect on bleeding, standing as an improved, useful and safe heparin antidote compared previously reported compounds. (Shenoi, ibid, Travers, ibid, and Kalathottukaren and Abraham, ibid.)
Using serial assays, MPI 2 was identified as an attractive agent from the library of inhibitors. MPI 2 is composed of a 23 kDa HPG-mPEG scaffold conjugated with ˜24 CBG I group per molecule resulting in an average charge of 35 positive charge at physiological pH. In comparison to UHRA, the charge of MPI 2 is significantly lower at physiological pH. Use of linear aliphatic triamine CBG-I ligand unlike Me6TREN in UHRA, reduces the charge state at physiological pH, resulting in a lower average number of charges per MPI. As well, the linear ligands demonstrate switchable protonation upon polyanion (e.g., heparin) binding to enhance the heparin reversal properties of MPIs derived from linear aliphatic CBGs. Accordingly, not all cationic residues on previous UHRA are necessary to stabilize binding with heparin because MPI 2 provides more effective heparin reversal using a ligand that exhibits a significant reduction in average cationic charge both per ligand and per macromolecule.
The reduction in net cationic charge on MPI 2 with increased selectivity to heparins provides multiple advantages over conventional heparin antidotes. For example, MPI 2 reverses multiple types of heparins including UFH, LMWH and fondaparinux with high efficiency whereas protamine sulfate (PS), the only FDA-approved heparin antidote, exhibits minimal reversal of LMWH anticoagulant activity, and is unable to reverse the effects of fondaparinux. (Mahan, C. E. A 1-Year Drug Utilization Evaluation of Protamine in Hospitalized Patients to Identify Possible Future Roles of Heparin and Low Molecular Weight Heparin Reversal Agents. J. Thromb. Thrombolysis 2014, 37 (3), 271-278.). Moreover, besides being ineffective as an antidote to all LMWHs and fondaparinux, PS has other undesirable properties when used as a heparin reversal therapeutic. (Pevni, D. et a. Protamine Induces Vasorelaxation of Human Internal Thoracic Artery by Endothelial NO-Synthase Pathway. Ann. Thorac. Surg. 2000, 70 (6), 2050-2053., Pretorius, M. et al, Pilot Study Indicating That Bradykinin B2receptor Antagonism Attenuates Protamine-Related Hypotension after Cardiopulmonary Bypass. Clin. Pharmacol. Ther. 2005, 78 (5), 477-485., Jenkins, C. S. P. et al. Interactions of Polylysine With Platelets. Blood 1971, 37 (4), 395., Bakchoul, T et al. Anti-Protamine-Heparin Antibodies: Incidence, Clinical Relevance, and Pathogenesis. Blood 2013, 121 (15), 2821., and Fairman, R. Pet al. Protamine Sulfate Causes Pulmonary Hypertension and Edema in Isolated Rat Lungs. J. Appl. Physiol. 1987, 62 (4), 1363-1367.). While protamine is an effective antidote to UFH (Garcia, D. et al. Parenteral Anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th Ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012, 141 (2 Suppl), e24S-e43S.), it must be carefully titrated upon administration to prevent serious adverse side effects that occur on overdose. As shown in
The advantages of MPI 2 are further highlighted using mouse tail bleeding models in vivo to establish the effects of anticoagulants and reversal of anticoagulants (Monroe, D. M. and Hoffman, M. A Mouse Bleeding Model to Study Oral Anticoagulants. Proc. 7th Symp. Hemost. Old Syst. New Play. New Dir. May 15-17 2014 Chap. Hill N. C. USA 2014, 133, S6-S8., Getz, T. M. et al. Mouse Hemostasis Model for Real-Time Determination of Bleeding Time and Hemostatic Plug Composition. J. Thromb. Haemost. 2015, 13 (3), 417-425., and Vaezzadeh, N. et al. Comparison of the Effect of Coagulation and Platelet Function Impairments on Various Mouse Bleeding Models. Thromb Haemost 2017, 112 (08), 412-418.). MPI 2 fully reverses the effects of 200 U/kg UFH and 200 U/kg enoxaparin in mice. When mice are administered MPI 2 without heparins, it has no significant effects on mice bleeding times or hemoglobin loss even at concentrations significantly higher than effective doses, thereby demonstrating that MPI 2 does not interfere with normal hemostasis. These observations provide support for the therapeutic role of MPI 2as a heparin reversal agent. Other heparin antidotes cannot provide such a large therapeutic window and may require careful titration upon administration (Kalathottukaren and Abraham, ibid, and Boer, ibid). The extended therapeutic window and minimal bleeding side effects with MPI 2 administration are particularly notable when compared to UHRA. While previous generation UHRAs demonstrated biocompatibility and potency (Shenoi, ibid, Kalathottukaren and Abraham, ibid), MPI 2 provides a substantially large therapeutic window for heparin neutralization for all heparins.
Compared to other PS alternatives, MPI 2 presents multiple advantages over protamine variants such as delparantag (McAllister R. Abstract 17322: Heparin-Antagonist PMX-60056 Rapidly and Completely Reverses Heparin Anticoagulation in Man. Circulation 2010, 122 (suppl_21), A17322-A17322), and PM102. (Shenoy, S. et al. Development of Heparin Antagonists with Focused Biological Activity. Curr. Pharm. Des. 1999, 5 (12), 965-986., and Cushing, D. J. et al. Reversal of Heparin-Induced Increases in APTT in the Rat by PM102, a Novel Heparin Antagonist. Eur. J. Pharmacol. 2010, 635 (1), 165-170.) Advantages over these peptide-based approaches includes the reduction of contamination that is common to biologically derived therapeutics. Our fully synthetic methods eliminate this risk at a low cost while simultaneously ensuring control of the final structure of the reversal agent. Other cationic polymers for electrostatic binding to heparins have been investigated, such as a pegylated cationic poly(3-(methacryloylamino)propyl)trimethylammonium chloride (PMAPTAC) block polymers prepared by Kalaska and colleagues. (Kalasaka, ibid.) While their heparin binding copolymer (HBC) showed reversal of low concentrations (on the range of 3-10 mg/kg) of enoxaparin and fondaparinux in vivo, the safety of HBC with bleeding at higher concentrations than necessary to reverse heparin was not reported. As seen by administration of high concentrations of other cationic structures such as PS, extended bleeding times and other complications, such as hypotension, can be lethal in some cases. (Labieniec-Watala, ibid, Boer, ibid.) MPI 2 does not extend bleeding times or hemoglobin loss at high concentrations, and its high biocompatibility underscores the utility of MPI 2 as a heparin antidote, thereby avoiding the complications when administering appropriate doses of PS or other potential protamine alternatives.
The present invention provides a new series of macromolecular polyanion inhibitors (MPIs) generated using cationic binding groups composed of linear alkyl amines. From this library of cationic polymers, compounds have been identified as safe and specific heparin antidotes. Candidate MPIs were screened by aPTT and calibrated automated thrombography, that highlight potent heparin reversal activity of MPI 2 over a broad range of concentrations tested. Heparin reversal activity of MPI 2 demonstrates a broad therapeutic window. Further characterization via thromboelastometry shows enhanced heparin reversal by MPI 2 vs. UHRA. Hemocompatibility of the MPIs from reduced net cationic charge per molecule provides optimized heparin reversal agents. Studies in vivo using a mouse tail bleeding model further confirm potent heparin reversal activity of MPI 2, and minimal bleeding side effects the polymeric therapeutics, even at doses an order of magnitude above the therapeutic dose. Together, these results show enhanced heparin reversal activity and minimized non-specific interactions achieved via the development of macromolecular polyanion inhibitors using a combination of tunable protonation properties of ligands, and highly biocompatible polymer scaffold towards novel therapeutics.
We determined the activities of MPIs as nucleic acid inhibitors. Diverse inhibitory compounds were used with PolyIC (Polyinosinic:polycytidylic acid) as a nucleic acid for the screening studies. MPI 3 was shown to correct the thrombotic and antifibrinolytic effect of nucleic acids in blood plasma.
The present disclosure further provides pharmaceutical compositions (e.g., comprising the compounds described above and elsewhere herein). The pharmaceutical compositions of the present disclosure may be administered in a number of ways depending upon whether local or systemic treatment is desired and upon the area to be treated. Administration may be topical (including ophthalmic and to mucous membranes including vaginal and rectal delivery), pulmonary (e.g., by inhalation or insufflation of powders or aerosols, including by nebulizer; intratracheal, intranasal, epidermal and transdermal), oral, intravenous or parenteral. Parenteral administration includes intravenous, intra-arterial, subcutaneous, intraperitoneal or intramuscular injection or infusion; or intracranial, e.g., intrathecal or intraventricular, administration. Administration may be achieved by single shot, a series of single shots, and/or by continuous administration. In certain embodiments, continuous administration is provided by a programmable external pump. In other embodiments, continuous administration is provided by a programmable implantable pump.
Pharmaceutical compositions and formulations for topical administration may include transdermal patches, ointments, lotions, creams, gels, drops, suppositories, sprays, liquids and powders. Conventional pharmaceutical carriers, aqueous, powder or oily bases, thickeners and the like may be necessary or desirable.
Compositions and formulations for oral administration include powders or granules, suspensions or solutions in water or non-aqueous media, capsules, sachets or tablets. Thickeners, flavoring agents, diluents, emulsifiers, dispersing aids or binders may be desirable.
Compositions and formulations for parenteral, intrathecal or intraventricular administration may include sterile aqueous solutions that may also contain buffers, diluents and other suitable additives such as, but not limited to, penetration enhancers, carrier compounds and other pharmaceutically acceptable carriers or excipients.
Pharmaceutical compositions of the present disclosure include, but are not limited to, solutions, emulsions, and liposome-containing formulations. These compositions may be generated from a variety of components that include, but are not limited to, preformed liquids, self-emulsifying solids and self-emulsifying semisolids.
The pharmaceutical formulations of the present disclosure, which may conveniently be presented in unit dosage form, may be prepared according to conventional techniques well known in the pharmaceutical industry. Such techniques include the step of bringing into association the active ingredients with the pharmaceutical carrier(s) or excipient(s). In general, the formulations are prepared by uniformly and intimately bringing into association the active ingredients with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product.
The compositions of the present disclosure may be formulated into any of many possible dosage forms such as, but not limited to, tablets, capsules, liquid syrups, soft gels, suppositories, and enemas. The compositions of the present disclosure may also be formulated as suspensions in aqueous, non-aqueous or mixed media. Aqueous suspensions may further contain substances that increase the viscosity of the suspension including, for example, sodium carboxymethylcellulose, sorbitol and/or dextran. The suspension may also contain stabilizers.
The compositions of the present disclosure may additionally contain other adjunct components conventionally found in pharmaceutical compositions. Thus, for example, the compositions may contain additional, compatible, pharmaceutically-active materials such as, for example, antipruritics, astringents, local anesthetics or anti-inflammatory agents, or may contain additional materials useful in physically formulating various dosage forms of the compositions of the present disclosure, such as dyes, flavoring agents, preservatives, antioxidants, opacifiers, thickening agents and stabilizers. However, such materials, when added, should not unduly interfere with the biological activities of the components of the compositions of the present disclosure. The formulations can be sterilized and, if desired, mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, colorings, flavorings and/or aromatic substances and the like which do not deleteriously interact with the nucleic acid(s) of the formulation.
Dosing is dependent on severity and responsiveness of the disease state to be treated, with the course of treatment lasting from several days to several months, or until a cure is affected or a diminution of the disease state is achieved. Optimal dosing schedules can be calculated from measurements of drug accumulation in the body of the patient. The administering physician can easily determine optimum dosages, dosing methodologies and repetition rates. Optimum dosages may vary depending on the relative potency of individual compounds, and can generally be estimated based on EC50s found to be effective in in vitro and in vivo animal models or based on the examples described herein. In general, dosage is from 0.01 μg to 100 g per kg of body weight, and may be given once or more daily, weekly, monthly or yearly. The treating physician can estimate repetition rates for dosing based on measured residence times and concentrations of the drug in bodily fluids or tissues. Following successful treatment, it may be desirable to have the subject undergo maintenance therapy to prevent the recurrence of the disease state, wherein the compound is administered in maintenance doses, ranging from 0.01 μg to 100 g per kg of body weight, once or more daily, to once every 20 years.
The following examples are provided to demonstrate and further illustrate certain embodiments and aspects of the present disclosure and are not to be construed as limiting the scope thereof.
All chemicals were purchased and used without further purification, unless indicated otherwise. Glycidol was purified by vacuum distillation and stored at 4° C. using molecular sieves (5 Å). Cellulose ester dialysis membranes were obtained from Spectra/Por Biotech (Rancho Dominguez, CA, USA). CDCl3 or D2O (Cambridge Isotope Laboratories, Andover MA) were used as solvents, with the relevant solvent peak as reference. Chelating resin (Chelex® 100) was purchased from Bio-Rad. Human fibrinogen (Fibrinogen), polyethyleneimine (PEI, 25 kDa), thrombin, protamine sulphate and N-2-hydroxyethyl piperazine-N′-2-ethanesulfonic acid (HEPES) were purchased from Sigma Aldrich. Recombinant tissue factor (TF, Innovin) was purchased from Dade-Behring. Polystyrene 96-well microplates (Costar) used for clotting assays were purchased from Corning. A microplate reader from Spectramax was used. Reagents used for calibrated automated thrombography such as thrombin calibrator, Flu-Ca solution and Immulon microplates were purchased from Diagnostica Stago. Citrated pooled normal human plasma (PNP) from 20 donors was purchased from Affinity Biologicals (ON, Canada). Buffer for biological assays was prepared with 20 mM HEPES with 150 mM NaCl, pH 7.4 unless otherwise stated. BD Vacutainer® Citrate Tubes containing 3.2% buffered sodium citrate solution were purchased from Becton, Dickinson and Company (New Jersey, USA). All other chemicals were purchased and used without further purification, unless indicated otherwise. Blood was drawn from consenting informed healthy volunteer donors at Centre for Blood Research, University of British Columbia, in vials containing EDTA or sodium citrate.
A NE-1000 Programmable Single Syringe Pump (Farmingdale, NY) was used for chemical synthesis and polymerization. Absolute molecular weights of the polymers were determined by GPC on a Waters 2695 separation module fitted with a DAWN EOS multi-angle laser light scattering (MALLS) detector coupled with Optilab DSP refractive index detector from Wyatt Technology. GPC analysis was performed using Waters ultrahydrogel 7.8×300 columns (guard, 250 and 120) and 0.1 N NaNO3 at pH 7.4 using 10 mM phosphate buffer as the mobile phase. 1H NMR spectra were recorded on a Bruker Advance 300 MHz NMR spectrometer and Bruker Advance 400 MHz NMR spectrometer.
mPEG350 Epoxide
To a 500 mL round bottom flask was added mPEG350 (110 g, 314 mmol, 1.0 eq.) with magnetic stir bar. To this, crushed NaOH pellets (39 g, 940 mmol, 3.0 eq.) were added and allowed to stir for 24 hours. The reaction mixture was then cooled to 0° C. and epichlorohydrin (53 mL, 658 mmol, 2.0 eq.) was slowly added over the course of 3 hours. The reaction was kept cool by replenishing the ice bath over the course of the slow addition. After complete addition of epichlorohydrin, the reaction mixture was stirred for an additional 24 hours and slowly warmed to room temperature. Once complete, the reaction was quenched with MeOH, and the remaining salts filtered off with DCM. Crude product was concentrated under vacuum. The crude product was dried on a vacuum drying line for 2 days to evaporate unreacted epichlorohydrin, affording the pure mPEG350 epoxide in 90% yield.
1H NMR (300 MHz, Chloroform-d): δ 3.78 (dd, J=11.7, 3.1 Hz, 1H), 3.73-3.51 (m, 33H), 3.47-3.35 (m, 4H), 3.16 (dq, J=6.1, 3.1 Hz, 1H), 2.79 (t, J=4.6 Hz, 1H), 2.61 (dd, J=5.0, 2.7 Hz, 1H).
A 3-neck round bottom flask was cooled under vacuum and filled with argon. To this, 1,1,1-tris(hydroxymethyl)propane (TMP, 167 mg) and potassium methylate (25 wt % solution in methanol, 0.110 mL) were added and stirred for 30 minutes. Methanol was removed under high vacuum for 4 hours. The flask was heated to 95° C. and distilled glycidol (3.8 mL) was added over a period of 15 hours. After complete addition of glycidol, the reaction mixture was stirred for an additional 12 hours. Then, mPEG350-epoxide (10.5 mL) was added over a period of 12 hours at 95° C. The reaction mixture was stirred for additional 4 hours. The reaction was cooled to room temperature, quenched with methanol, then passed through Amberlite IR-120H resin to remove the potassium ions and twice precipitated from diethyl ether. The polymer was then dissolved in water and dialyzed in water membrane for 3 days with periodic changes in water.
1H NMR (300 MHz, Chloroform-d) δ 4.04-3.40 (m, 50H), 3.38 (s, 3H).
mPEG content (by 1H NMR): 25 mol %; Polyglycerol: 75 mol %.
GPC-MALLS (0.1 M NaNO3): Mn 24 000; Mw/Mn 1.3.
For 10 kDa polymers, the same synthetic procedure was followed with higher initiator:monomer ratio. A 3-neck round bottom flask was cooled under vacuum and filled with argon. To this, 1,1,1-tris(hydroxymethyl)propane (TMP, 268 mg) and potassium methylate (25 wt % solution in methanol, 0.178 mL) were added and stirred for 30 minutes. Methanol was removed under high vacuum for 4 hours. The flask was heated to 95° C. and distilled glycidol (5.71 mL) was added over a period of 23 hours. After complete addition of glycidol, the reaction mixture was stirred for an additional 3 hours. Then, mPEG350-epoxide (12.8 mL) was added over a period of 12 hours at 95° C. The reaction mixture was stirred for additional 4 hours. The reaction was cooled to room temperature, quenched with methanol, then passed through Amberlite IR-120H resin to remove the potassium ions and twice precipitated from diethyl ether. The polymer was then dissolved in water and dialyzed in water membrane for 3 days with periodic changes in water.
1H NMR (300 MHz, Chloroform-d) δ 4.04-3.40 (m, 50H), 3.38 (s, 3H).
mPEG content (by 1H NMR): 27.5 mol %; Polyglycerol: 72.5 mol %.
GPC-MALLS (0.1 M NaNO3): Mn 10 360; Mw/Mn 1.2.
The reaction was carried out under an inert gas atmosphere and exclusion of water. (Roller, S. et al. High-Loading Polyglycerol Supported Reagents for Mitsunobu- and Acylation-Reactions and Other Useful Polyglycerol Derivatives. Mol. Divers. 2005, 9 (4), 305-316.) HPG-mPEG (200 mg) in a 3-necked 100 mL flask with thermometer magnetic stirrer was dissolved in pyridine (5 mL). The solution was cooled to 0° C. by an ice/NaCl bath, then, and a solution of tosyl chloride (TsCl) (1.2 eq. of target average number of groups) in pyridine (5 mL) was added dropwise so that the temperature did not exceed 5° C. The brown mixture was stirred for 16 hours as the reaction was allowed to warm to room temperature. Then solvent was removed in vacuo. The resulting mixture was then dialysed in water for 3 days with periodic changes in water to give a honey-like product.
1H NMR (400 MHz, Chloroform-d): δ 7.78 (m, 0.7H), 7.34 (m, 0.7H), 3.98-3.39 (m, 48H), 3.35 (s, 3H), 2.45 (s, 1.05H).
In a 50 mL 1-necked flask with reflux condenser and magnetic stirrer, HPG-mPEG-OTs (200 mg, 0.20 mmol OTs-groups) was dissolved in anhydrous 1,4-dioxane (10 mL). (Roller, ibid.) After addition of CBG (1 mmol, 5.0 eq.), the resulting suspension was heated to reflux at 115° C. for 24 hours. After cooling the reaction mixture, the mixture was dialyzed in water for 3 days with periodic changes in water to give a brown honey-like product.
1H NMR (300 MHz, Chloroform-d): δ 3.89-3.43 (m, 35H), 3.38 (s, 3H), 2.87 (m, 9H).
Amine functionalized HPG-mPEG (200 mg, 24 CBG per polymer), was transferred to a 20 mL side-necked flask. The reaction mixture was dissolved in DI water at room temperature. 10 mL of a formic acid/formaldehyde (1:1) mixture was added dropwise to the reaction flask. The reaction was stirred and heated to reflux at 110° C. for 24 hours. After cooling the reaction mixture, the mixture was dialyzed in water for 22 days with periodic changes in water until the pH of the water was neutral. Upon lyophilizing to remove excess water, CBG linked polymer was collected.
1H NMR (300 MHz, Chloroform-d): δ 8.11 (s), 4.11-3.19 (m), 3.19-2.95 (m), 2.78-1.94 (m).
Time allowed for equilibration was 15 seconds for conductometry titrations. A solution of CBG in water (0.1 mM) was acidified dropwise with 1.0 M HCl and titrated with carbonate-free NaOH (0.5012 M) that was standardized against freshly recrystallized potassium hydrogen phthalate. Temperature was kept constant at 25° C. with a warm water bath. Titration curves were manually fitted to calculate 1H concentration.
All data were collected in triplicate. Prior to each titration, the electrode was calibrated using a standard HCl solution. Calibration data were calculated to obtain parameters E0 and pKa. Time allowed for equilibration was 10 minutes for pKa titrations. Solutions were titrated with carbonate-free NaOH (0.141 M) that was standardized against freshly recrystallized potassium hydrogen phthalate. Protonation equilibria of the CBG were investigated by NaOH titrations of a solution containing (CBG) 1.1×10−3 M at 25° C. and 0.16 M NaCl ionic strength. Potentiometric data were processed using HyperQuad2013 software. (Gans, P. et al. Investigation of Equilibria in Solution. Determination of Equilibrium Constants with the HYPERQUAD Suite of Programs. Talanta 1996, 43 (10), 1739-1753.) Titrations were performed on a 809 Titrando from Metrohm. Temperature was kept constant with a circulating water bath.
The interaction of MPI and surface-bound polyP was carried out at 25° C. using a T200 Biacore (GE Healthcare, Life Sciences). Samples were prepared by making stock solutions of at least 100× the desired concentration at high volume and filtered using 0.2 m filters (Millex, Merck Millipore Ltd). Running buffer was prepared with 20 mM HEPES with 100 mM NaCl, 1 mM EDTA and 0.005% P20 surfactant. Running buffer was degassed, filtered and the pH was 7.4. Prior to titration, stock solutions of MPI were serially diluted with same running buffer. Multi-cycle assays were run with 1 M NaCl injection after each cycle. Using a flow rate of 30 L/min, an injection volume of 60 μL and therefore an injection over 120 seconds, a dissociation was run over 60 seconds. 7-8 concentrations for each MPI were run for each steady state affinity plot. All samples were run on a Series S sensor chip CM4 (GE Healthcare, Life Sciences), with streptavidin bound to the surface to allow for capture of biotinylated polyP. Three of the 4 flow cells contained biotinylated long chain polyP (P1075), biotinylated medium chain polyP (P560), and biotinylated platelet sized polyP (P110), while one flow cell contained streptavidin but no polyP (the reference cell). Data was analyzed on the Biacore T200 Software (GE Healthcare, Life Sciences).
The interaction of MPI and polyP was carried out at 25° C. using a MicroCal iTC200 calorimeter (MicroCal, Northampton, USA). Samples were prepared by making stock solutions of at least 100× the desired concentration at high volume and filtered using 0.2 m filters (Millex, Merck Millipore Ltd). The pH of each solution was then measured to ensure that they were between 7.35 and 7.40. Prior to titration, stock solutions were diluted with the same filtered buffer and degassed. Titrations consisted of 25 consecutive injections of 1.5 μL volume and 5 sec duration each, with a 3 min interval between injections with only the first injection between 0.2 μL volume, not used as part of the fit. Heat of dilution was measured by injecting MPI solution into buffer alone and was subtracted from the experimental curves prior to data analysis. The resulting data were fit into a single set of identical sites model using the MicroCal ORIGIN software supplied with the instrument.
NMR spectra for MPI and polyP binding interaction studies were acquired on a Bruker 500 MHz instrument (Bruker Biospin, Milton, ON), operating at a 1H frequency of 499.4 MHz. 31P NMR spectra were collected at 298 K. The NMR sample was prepared to yield 0.5 mM of polyphosphate in HEPES buffer with 150 mM NaCl and 10% D2O (by volume) for a total sample volume of 600 μL. All polyphosphate concentrations are provided in terms of the concentration of phosphate monomer. For the binding study, polyphosphate was first prepared with a known concentration of internal standard of trimethylphosphate. MPI was titrated in, and the total volume was increased by 1.5 μL of the 600 μL total per addition.
Microplate turbidimetric clotting assays were performed with platelet-poor plasma (PPP) obtained from three donors. MPI solutions were prepared in 20 mM HEPES (pH 7.4, 150 mM NaCl) buffer. Clotting was initiated in 90 μL of 30% diluted PPP spiked with MPI (dilution 1:10) by adding 5 μL of recombinant tissue factor (TF; Innovin (1:10,000; 0.73 μM)) and 5 μL of CaCl2) (20 mM). Clotting was evaluated by monitoring changes in turbidity (A405 nm) every 30 seconds with the Spectramax microplate reader for 2 hours at 37° C. Clotting parameters including lag time were calculated and considered as the time point when an exponential increase in absorbance was first observed.
Platelet activation was quantified by flow cytometry. Ninety microliters of platelet rich plasma (PRP) were incubated at 37° C. with 10 μL of stock MPI samples for one hour. 10 μL of post-incubation platelet/polymer mixture was diluted in 45 μL PPP and incubated for 15 minutes in the dark with 5 μL of monoclonal anti-CD62-PE (Immunotech, Marseille, France). The reaction was then stopped with 0.5 mL of phosphate-buffered saline solution. The level of platelet activation was analyzed in a BD FACS Canto II flow cytometer (Becton Dickinson, ON, Canada) by gating platelet-specific events based on their light scattering profile. Activation of platelets was expressed as the percentage of platelet activation marker CD62P-PE (phycoerythrin) fluorescence detected in the 10,000 total events counted. Triplicate measurements were performed and the mean was recorded. Thrombin receptor activator receptor 6 (TRAP6), a recognized platelet activator (SigmaAldrich, Oakville, ON, Canada), was used as a positive control for the flow cytometric analysis.
Determination of polyP Inhibition Activity by Serine Protease Activity Assay
Serine protease assays were carried out at 37° C. by measuring the absorbance intensity upon cleavage of a chromogenic substrate, Chromogenix S-2288 that is sensitive to a broad spectrum of serine proteases. Commercially available pooled platelet poor plasma (PPP, 20 donors) was purchased from Affinity Biologicals. A stock solution of MPI was prepared at concentrations for a 1:10 dilution of the polymer solution. Coming 96 well plates were pre-treated with 3% BSA solution for 30 minutes at room temperature and subsequently washed 3× with tricine buffer (10 mM tricine+150 mM NaCl).
For the inhibition studies, MPI were incubated with polyP-substrate-buffer mixture for 30 minutes at 37° C. In this mixture, polyphosphates of length 700 monomer units per polymer (P700) were used at a final concentration of 100 μM monomer concentration. A Final substrate concentration of 200 μM was prepared from a working stock after reconstitution following manufacturer's instructions. As a negative control, a solution of tricine buffer mixed with MPI was incubated without addition of P700, making up the solution difference with tricine buffer. As a positive control, P700 was incubated with buffer without addition of pPBA. Buffer control was also recorded, containing tricine buffer and chromogenic substrate only. 120 μL of the mixtures were pipetted out into a 96 well plate in triplicates. The serine protease assay was initiated by addition of 80 μL of the chromogenic substrate-polyP-pPBA mixture to each well containing 20 μL of pre-warmed (37° C.) plasma with a multichannel pipette, making the total reaction volume 100 μL. Serine protease activity was measured and recorded as absorbance intensity over time. The absorbance intensity was recorded at 37° C. every 15 seconds over a period of 45 minutes on a SpectraMax M3 plate reader at an excitation wavelength of 405 nm. Based on the positive control, a time frame of one minute was selected for analysis where the activity presented in mOD would be plotted over the one minute for each well, to obtain the activity of serine protease.
A thrombin generation assay was carried out at 37° C. by measuring the fluorescence intensity upon cleavage of the fluorogenic substrate Z-Gly-Gly-Arg-AMC by regenerated thrombin. Commercially available pooled normal platelet poor plasma (PNP, 30 donors) from George King Bio-Medical, USA was mixed 1:1 with HBS (20 mM HEPES with 100 mM NaCl at pH 7.4). Phosphatidylcholine (80): phosphatidylserine (20) (PCPS) liposomes were added to obtain a final concentration of 20 μM. Serial dilutions of MPI candidates and UHRA were prepared fresh for these experiments. Experiments were repeated twice with two technical replicates each. Thrombin calibrator was used following the manufacturer's instructions, and the thrombin generation assay was initiated by the addition of fluorogenic substrate (both from Diagnostica Stago). Substrate hydrolysis was monitored on a fluorescent plate reader from Diagnostica Stago. The fluorescence intensity was recorded at 37° C. every 30 seconds over a period of 1.5 hours and analyzed using Thrombinoscope™ software from Diagnostica Stago.
In order to determine what affect each MPI candidate (Error! Reference source not found.) had on thrombin generation in the absence of polyP, TF (Thrombinoscope™) was added to initiate clotting at a final concentration of 5 μM. Final concentrations of MPIs ranged from 5-50 μg/mL. No other clotting initiators or accelerators were added.
Determination of Long Chain Polyphosphate (LC polyP) Inhibition by Thrombin Generation Assay
To determine the efficacy of LC polyP inhibition, a mixture of plasma, PCPS and MPI or UHRA were incubated with LC polyP (200 μM) for 3 minutes at 37° C. prior to the initiation of clotting. Concentrations of inhibitors tested ranged from 0.2-100 μg/mL.
Determination of Short Chain Polyphosphate (SC polyP) Inhibition by Thrombin Generation Assay
To determine the efficacy of SC polyP inhibition, FXII deficient plasma (Haemtech) was used. To a mixture of plasma, PCPS and MPI, SC polyP was added at a final concentration of 5 μM. TF (Thrombinoscope™) at a final concentration of 8.3 fM was also included in the mixture. The inhibitor concentrations tested ranged from 0.2-100 μg/mL.
For the clotting assay, each well was filled with 100 μL of a mixture containing FXII deficient plasma (Haemtech) (50 μL), MPI (100 μg/mL, final) in HEPES buffered saline with bovine serum albumin (HBSA, 20 mM HEPES and 100 mM NaCl at pH 7.4 with 0.1% BSA) and relipidated tissue factor in 30% PCPS liposomes. This mixture was incubated for 120 seconds at 37° C., then clotting was initiated by addition of 50 μL pre-warmed (37° C.) 25 mM CaCl2). Clot time was measured on a STart 4® coagulometer (Diagnostica Stago, France).
Determination of polyP Inhibition Activity by Viscosity-Based Plasma Clotting Assay
MPI solutions were prepared in 10 mM tricine buffer (pH 7.4, 50 μM ZnCl2 and 150 mM NaCl). For inhibition studies, citrated human PPP from Affinity Biologicals (20 donors, pooled) was warmed to 37° C. and incubated with MPI solutions and polyP (700 monomer units at 20 μM final monomer concentration) at 37° C. for 15 minutes such that the final plasma concentration consisted of 50% of the reaction mixture. The final concentration of MPI in plasma ranged from 2.5 to 100 μg/mL. As a positive control, plasma was incubated with MPI without addition of polyP, maintaining the plasma concentration at 50%. As a negative control, plasma was incubated with tricine buffer, again maintaining the same concentration of plasma. Clotting was initiated by addition of a clotting mixture comprised of recombinant tissue factor (Dade® Innovin®rTF, Siemens/Dade-Behring), an 80:20 PCPS mixture and CaCl2) at final concentrations of 0.24 μM, 25 μM and 7.7 mM, respectively. One hundred microliters of the plasma mixture were transferred to cuvette-strips at 37° C. and clotting was initiated with addition of 50 μL of the clotting mixture. The clotting time was measured on a STart 4® coagulometer (Diagnostica Stago, France). Because each experimental cuvette strip had 4 wells, each experiment was run with one negative and one positive controls. All experiments were performed in triplicate and the average values (mean±standard error of the mean) are reported.
The level of platelet activation was quantified by flow cytometry. Ninety microliters of PRP were incubated at 37° C. with 10 μL of stock MPI samples (MPI 1, MPI 6 and MPI 8 at final concentrations ranging from 50-200 μg/mL) for 1 hour. Ten microliters of post-incubation platelet/MPI mixture were diluted in 45 μL PPP from the same donor and incubated for 15 minutes in the dark with 5 μL of monoclonal anti-CD62-PE (Immunotech, Marseille, France). The reaction was then stopped with 0.5 mL of phosphate-buffered saline solution. The level of platelet activation was analyzed from flow cytometry profiles by gating platelet-specific events based on their light scattering profile. Flow cytometry profiles were acquired using a 3-laser CytoFLEX flow cytometer from Beckman Coulter Life Sciences (Indianapolis, IN). Activation of platelets was expressed as the percentage of platelet activation marker CD62P-PE (phycoerythrin) fluorescence detected in the 10,000 total events counted. Triplicate measurements were done, the mean of which was recorded. Thrombin receptor activator peptide 6 (TRAP 6), a recognized platelet activator, (Sigma Aldrich, Oakville, ON, Canada) was used as a positive control for platelet activation analysis.
Whole blood was mixed with MPI (MPI 1, MPI 6 and MPI 8 with a final concentration of 100 μg/mL) in HEPES buffered saline (HBS) (20 mM HEPES+150 mM NaCl), and analyzed for whole blood clotting using a ROTEM® delta from Tem Innovations GmbH (Instrumentation Laboratory as of 2016) at 37° C. Stock solutions of the MPIs and UHRA were prepared at concentrations 100× the final desired concentration in HBS. Citrate anticoagulated whole blood (356 μL) was mixed with 44 μL of the MPIs or UHRA. Three hundred and forty microliters of this suspension were transferred into the ROTEM cup and was re-calcified with 20 μL of 0.2 M calcium chloride solution. HBS mixed with whole blood was used as a negative control for the experiment.
The effects of MPI 8 on the overall fibrin clot structure and fibrin diameter of the clot in the presence of MPI 8 were assessed by SEM. All samples were randomly coded and blinded to the individual performing the imaging analysis to avoid bias. Fibrin clots were prepared in sterile, 5 mL round-bottom polypropylene tubes (BD Falcon) by mixing human fibrinogen (2.6 mg/mL) in 20 mM HEPES (pH 7.4 and 150 mM NaCl) buffer with 2.5 mM CaCl2 (final). When indicated, MPI 8 (20 μg/mL) or polyP (P700, 100 μM) were added. Control clots were prepared in the absence of MPI 8 or polyP. Clotting was initiated with 3 nM thrombin. Clots were then allowed to mature for 1 hour and processed for SEM imaging.
The clot samples were rinsed three times using HEPES buffer then fixed with Karnovsky fixative (2.5% glutaraldehyde and 4% formaldehyde). To allow for better penetration of the buffer solutions into the clot, a PELCO344I Laboratory Microwave System was used between buffer changes. After clot fixation, the clot sample was washed three times using fresh 0.1 M sodium cacodylate buffer before staining using 1% osmium tetroxide dissolved in 0.1 M sodium cacodylate buffer in the microwave. The clot sample was washed gently using distilled water for a minimum of five exchanges and resuspended in 50% ethanol solution. It was left to incubate for 10 minutes at room temperature before subjecting it to the microwave. The dehydration procedure was repeated using a graded series of ethanol solutions (70%, 80%, 90%, and 95% ethanol in water followed by 100% ethanol three times). Once the sample was fully dehydrated, it was placed in a Tousimis Autosamdri 815B Critical Point Dryer overnight under stasis mode before fully completing the drying process the following day. The processed samples were mounted on SEM stubs using hot glue and coated in 10 nm of Au/Pd coating (16.38 g/cm3) using a Cressington 208HR High Resolution Sputter Coater. Samples were stored in a desiccator. Clot images were captured on a Helios NanoLab 650 SEM at different magnifications (5000×, 10000× and 25000×). Multiple images from different areas of each clot were captured. Fiber diameters of clots were measured with ImageJ. For fibrin fiber diameter calculations, images from two independent experiments were analysed. Fibrin fiber diameters (n=80) from 4 separate areas of each clot were used to calculate the mean fiber diameter.
Adult wild type mice (10-12 weeks old) were intravenously injected with 200 mg/kg MPI 8 or equivalent volume of PBS (vehicle) via tail vein injection. The effect of MPI 8 in hemostatic clot formation in vivo was examined using a laser-ablation saphenous vein hemostasis model as described. (Adili R. et al. A batroxobin containing activated Factor X effectively enhances hemostatic clot formation and reducing bleeding in hypocoagulant conditions in mice. Clin Appl Thromb Hemost. 2021 January-December; 27:10760296211018510, and Adili R. et al. First selective 12-LOX inhibitor, ML355, impairs thrombus formation and vessel occlusion in vivo with minimal effects on hemostasis. Arterioscler Thromb Vasc Biol. 2017 October; 37(10):1828-1839.) Mice were anesthetized by an intraperitoneal injection of ketamine/xylazine (100 and 10 mg/kg, respectively) and intravenously administered DyLight 488-conjugated rat anti-mouse platelet GP1bβ antibody (0.1 μg/g; EMFRET Analytics) and Alexa Fluor 647-conjugated anti-fibrin (0.3 g/g) via tail vein cannula. The saphenous vein was surgically prepared under a dissecting microscope and superfused with preheated bicarbonate saline buffer throughout the experiment. Blood flow of the saphenous vein was visualized under a 20× water immersion objective using a Zeiss Axio Examiner Z1 fluorescent microscope equipped with a solid laser launch system. The saphenous vascular wall was exposed to 2 maximum-strength 532-nm laser pulses (70 IJ; 100 Hz; for about 7 ns, 10 ms intervals) to puncture a hole (48 to 65 μm in diameter) in the vessel wall, resulting in bleeding visualized by the escape of fluorescent platelets to the extravascular space. The laser injury was performed at 30 seconds and repeated 5 and 10-minutes after the initial injury at the same site to assess platelet-fibrin hemostatic clot formation. The dynamics of platelet accumulation and fibrin deposition within the clot were recorded in real-time and the changes in the mean fluorescent intensity over time were analyzed using the Slidebook 6.0 program. A total of 4 mice (2 males and 2 females) with 3-4 independent injuries each were analyzed in the control and treatment groups.
Influence of MPI on Bleeding in Mice without Added polyP
A mouse model was used to assess the effect of MPI on bleeding in the absence of added polyP or any anticoagulants. Heparin was used as a positive control and saline was used as a negative control. Eight to ten week-old C57/BL6 mice were obtained from The Jackson Laboratories (Bar Harbor, ME), and the experimental protocol was approved by the International Animal Care and Use Committee at the University of Michigan. Mice were anesthetized, weighed and placed on a heated surgical tray. The tail was immersed into 15 mL of pre-warmed (37° C.) sterile saline (0.9% NaCl). To test the bleeding effects of different agents, MPIs, UHRA-10, saline or heparin were injected retro-orbitally and allowed to circulate for 5 minutes using solutions of MPI 1, MPI 6, MPI 8, UHRA-10 and UFH in sterile saline for maximum injection volumes of 50 μL and final concentrations of 100-300 mg/kg, or 200 U/kg for UFH. The distal tail (5 mm from the tip) was amputated with a surgical blade (Integra Miltex) and immediately re-immersed in 15 mL of pre-warmed (37° C.) sterile saline (0.9% NaCl). The time required for spontaneous bleeding to cease was recorded. After a maximum of 10 minutes, the tail was removed from the saline and the mouse was euthanatized by cervical dislocation. The blood samples were then pelleted at 500× g for 10 minutes at room temperature and the pellet was resuspended in 5 mL of Drabkin's Reagent (Sigma) and incubated at room temperature for 15 minutes. The amount of hemoglobin lost was quantified by comparing the absorbance of the samples at 540 nm to a standard curve of bovine hemoglobin in Drabkin's reagent.
A laser injury thrombosis model in mice was used to screen the efficiency of the MPIs. Intravital microscopy was used to measure the accumulation of platelets and fibrin at the site of the injury. Ten to twelve week-old C57/BL6 mice were obtained from The Jackson Laboratories (Bar Harbor, ME). The experimental protocol was approved by the International Animal Care and Use Committee at the University of Michigan. Male adult mice were anesthetized and a tracheal tube was inserted to facilitate breathing. Antibodies, anesthetic reagent (pentobarbital, 0.05 mg/kg body wt; Abbott Laboratories, Toronto, Ontario, Canada), and exenatide (60 nmol/kg body wt i.v.) were administered by a jugular vein cannula. The cremaster muscle was prepared under a dissecting microscope and superfused throughout the experiment with preheated bicarbonate buffer saline. Platelets were labeled by injecting a DyLight 649-conjugated rat anti-mouse GP1bb antibody (0.1 mg/g; EMFRET Analytics). Multiple independent upstream injuries were performed on a cremaster arteriole with the use of an Olympus BX51WI Microscope with a pulsed nitrogen dye laser. The dynamic accumulation of fluorescently labeled platelets within the growing thrombus was captured and analyzed using SlideBook software (Intelligent Imaging Innovations). Blood glucose levels were monitored throughout the experiment and remained constant.
Mice were anesthetized by an inhaled isoflurane-oxygen mixture. MPI and UHRA compounds diluted in sterile normal saline were injected retro-orbitally. The left carotid artery was exposed via a midline cervical incision and blunt dissection, and blood flow was monitored with a Doppler vascular flow probe (Transonic 0.5PSB) connected to a perivascular flowmeter (Transonic TS420). To induce thrombosis, two 1×2-mm pieces of filter paper (Whatman GB003) saturated with freshly prepared 7.5% anhydrous FeCl3 in 0.9% saline were applied to the deep and superficial surfaces of the artery. After 3 minutes, the filter papers were removed, and the vessel was irrigated with saline. Blood flow was monitored from FeCl3 application for 30 minutes or until occlusion, defined as no detectable flow for 3 minutes. Mice were then euthanized by cervical dislocation while still under anesthesia. Flow data were interpreted with LabScribe2 (iWorx Systems). Data for this study are reported as mean (n=8 mice)±standard deviation.
An escalating dose study in mice was used to measure the tolerance of MPI 8. Female Balb/C mice (6-8 weeks, 20-26 g) were individually weighed and were divided into groups of 4 for each dose. Each group of mice (N=4) were administered study compounds intravenously (via tail vein) with increasing doses of MPI 8 (250 to 500 mg/kg). The injection volume was 200 μL/20 g mouse. The mice were briefly restrained (less than 30 sec) during i.v. injections. Dilation of the vein was achieved by holding the animals under a heat lamp for about 1-2 min. After injection, the mice were returned to the cages and monitored for signs of acute toxicity over a period of 1 day. Body weights of individual mice were recorded prior to injection. After 24 hours of injection, mice were terminated by C02 asphyxiation, blood (50 μL) was collected from each mouse on the final day and necropsy was performed on all animals. Serum samples were analyzed for lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity.
Serum samples were analyzed for LDH activity using a lactate dehydrogenase enzyme assay kit (Abcam., Cambridge, UK). The kit measures the concentration of LDH using a direct, plate-based, colorimetric titration and consists of a 96-well microtiter plate, LDH reagent mix, standard and standard dilution buffer. When serum is added to the LDH reagent mix, the LDH in the sample converts the lactate and NAD+ in the mix to pyruvate and NADH, which interacts with a specific probe to produce a color which can be monitored by measuring the increase in the absorbance of the reaction at 450 nm over a 5 min time interval. In a typical test procedure, 5 μL of the serum sample (dilution factor determined upon initial reading) was added in duplicate to microplate wells and incubated with 50 μL of the reconstituted LDH per the supplier's instructions, and the absorbance was measured at 450 nm. A calibration curve was created using standards of NADH from 0-12.5 nmol/well. The average value of the absorbance was used in combination with the standard curve to obtain the LDH activity (IU/mL).
Serum samples were analyzed for AST activity using an aspartate aminotransferase enzyme assay kit (Sigma Aldrich., Oakville, ON). The kit measures the concentration of AST using a direct, plate-based, colorimetric titration and consists of a 96-well microtiter plate, AST reagent mix, standard and standard dilution buffer. When serum is added to the AST reagent mix, the AST in the sample transfers an amino group from aspartate to α-ketoglutarate resulting in oxaloacetate and glutamate, which results in the production of a colorimetric product proportional to the AST enzymatic activity present. This activity is monitored by measuring the increase in the absorbance of the reaction at 450 nm over a 30 min time interval. In a test procedure, 50 μL of the serum sample (dilution factor determined upon initial reading) was added in duplicate to microplate wells and incubated with 100 μL of the reconstituted AST reaction mixture per the supplier's instructions, and the absorbance was measured at 450 nm. A calibration curve was created using standards of glutamate from 0-10 nmol/well. The average value of the absorbance was used in combination with the standard curve to obtain the AST activity (IU/mL).
Serum samples were analyzed for ALT activity using an alanine aminotransferase enzyme assay kit (Sigma Aldrich., Oakville, ON). The kit measures the concentration of ALT using a direct, plate-based, colorimetric titration and consists of a 96-well microtiter plate, ALT reagent mix, standard and standard dilution buffer. When serum is added to the ALT reagent mix, the ALT in the sample transfers an amino group from alanine to α-ketoglutarate resulting in pyruvate and glutamate, which results in the production of a colorimetric product proportional to the ALT enzymatic activity present. This activity is monitored by measuring the increase in the absorbance of the reaction at 570 nm over a 30 min time interval. In a test procedure, 20 μL of the serum sample (dilution factor determined upon initial reading) was added in duplicate to microplate wells and incubated with 100 μL of the reconstituted ALT reaction mixture per the supplier's instructions, and the absorbance was measured at 570 nm. A calibration curve was created using standards of pyruvate from 0-10 nmol/well. The average value of the absorbance was used in combination with the standard curve to obtain the ALT activity (IU/mL).
An escalating dose study in mice was used. Female Balb/C mice (6-8 weeks, 20-26 g) were individually weighed and were divided into groups of 4 for each dose. Each group of mice (N=4) were administered test compounds intravenously (via tail vein) with increasing doses of MPI 8 (100 to 500 mg/kg). The injection volume was 200 μL/20 g mouse. The mice were briefly restrained (less than 30 sec) during i.v. injections. Dilation of the vein was achieved by holding the animals under a heat lamp for about 1-2 min. After injection, the mice were returned to cages and monitored daily for signs of acute toxicity over a period of 14 days. Body weights of individual mice were recorded prior to injection and every day except weekends thereafter. On day 15, mice were terminated by C02 asphyxiation, blood (50 μL) was collected from each mouse on the final day and necropsy was performed on all animals. Serum samples were analyzed for lactate dehydrogenase (LDH) activity using a lactate dehydrogenase enzyme assay kit (Abcam., Cambridge, UK) as described in above.
In Vivo Studies with MPI 3
The CLP model was adapted from established protocols in the literature. (Toscano, M. et al. (2011). Cecal ligation puncture procedure. JoVE (Journal of Visualized Experiments), (51), e2860.) Nine-week-old female mice (C57BL/6NCrl) were obtained from Charles River Laboratories. To gain access to the peritoneal cavity, a small incision was made in the abdomen. The cecum was located and exteriorized with wetted cotton tips. On the tip of the cecum, a ligature close to the size of a pinhead was made. A 19G needle was used to puncture the ligated cecum, and some feces were externalized. After that, the cecum was returned to the abdominal cavity, and the muscle and skin layers were closed with a Vicryl 6×0 running suture. For SHAM controls, the same procedure was followed except for the ligature and puncture in the cecum. Buprenorphine 0.1 mg/kg was administered 4 hours after surgery. MPI 3 at concentrations of 25 or 50 mg/kg were given subcutaneously at 2 hours, 4 hours, and 6 hours (3 doses) after surgery. Mice were euthanized 8 hours after surgery, and blood was collected via cardiac puncture into a syringe containing 3.2% sodium citrate.
Citrated blood was centrifuged at 1200×g for 10 minutes to remove RBCs, then at 10,000×g for 10 minutes to remove any residual cells and debris, thereby yielding platelet-poor plasma (PPP). Calibrated automated thrombography (CAT) was used to measure thrombin generation. In HEPES buffer, 80 μL of 1:4 diluted mouse plasma was mixed with 20 μL of the PPP—reagent LOW (Stago). The addition of 20 μL of FluCa reagent containing 2.5 mM Fluorogenic Urokinase Substrate III (Calbiochem, CAT #672159) and 100 mM CaCl2) in HEPES-BSA buffer triggered thrombin generation. The CAT software was used to process and analyze the data. TAT complex was measured using the Mouse Thrombin-Antithrombin (TAT) Complex ELISA Kit (Abcam, CAT #ab137994) as directed by the manufacturer. DNA concentration in the plasma was determined using the Quant-iT™ PicoGreen™ dsDNA Assay Kit (Fisher Scientific, CAT #-P11496) as directed by the manufacturer.
Blood was collected using the above-mentioned procedure and centrifuged at 1000×g for 10 minutes at 4° C. within 30 minutes of collection. The plasma was collected, diluted twice with phosphate-buffered saline (PBS), and stored at −80° C. Samples were sent to Eve Technologies to for a cytokine profile using their Mouse Cytokine/Chemokine 31-Plex Discovery Assay® Array (MD31).
Data are expressed as the mean±standard deviation from n (≥3) independent experiments unless otherwise specified. Statistical analyses were performed using GraphPad Prism version 7.0 software, using a Student's t-test or by one-way ANOVA followed by a Dunnett post hoc test. P values<0.05 were considered statistically significant. Samples were denoted as statistically significant. p<0.05 (*), p<0.01 (**), p<0.001 (***) and p<0.0001 (****). Experiments were performed in duplicate at least 3 times and results were pooled into a single dataset unless stated otherwise.
A 3-neck round bottom flask was cooled under vacuum and filled with argon. To this, 1,1,1-tris(hydroxymethyl)propane (TMP, 167 mg) and potassium methylate (25 wt % solution in methanol, 0.110 mL) were added and stirred for 30 minutes. Methanol was removed under high vacuum for 4 hours. The flask was heated to 95° C. and distilled glycidol (3.8 mL) was added over a period of 15 hours. After complete addition of glycidol, the reaction mixture was stirred for an additional 12 hours. Then, mPEG350-epoxide (10.5 mL) was added over a period of 12 hours at 95° C. The reaction mixture was stirred for additional 4 hours. The reaction was cooled to room temperature, quenched with methanol, then passed through Amberlite IR-120H resin to remove the potassium ions and twice precipitated from diethyl ether. The polymer was then dissolved in water and dialyzed in water membrane for 3 days with periodic changes in water.
1H NMR (300 MHz, Chloroform-d) δ 4.04-3.40 (m, 50H), 3.38 (s, 3H). mPEG350 content (by 1H NMR): 25 mol %; Polyglycerol: 75 mol %.
GPC-MALLS (0.1 M NaNO3): Mn 24 000; Mw/Mn 1.3.
This reaction was carried out under an inert gas atmosphere and exclusion of water. HPG-mPEG (200 mg) in a 3-necked 100 mL flask with thermometer and magnetic stirrer was dissolved in pyridine (5 mL). The solution was cooled to 0° C. by means of ice/NaCl bath, then, a solution of TsCl (1.2 eq. of target average number of groups) in pyridine (5 mL) was added dropwise so that the temperature did not exceed 5° C. The brown mixture was stirred for 16 hours as the reaction was allowed to warm to room temperature. Then solvent was removed in vacuo. The resulting mixture was then dialysed in water for 3 days with periodic changes in water to give a honey-like product.
1H NMR (400 MHz, Chloroform-d): δ 7.78 (m, 0.7H), 7.34 (m, 0.7H), 3.98-3.39 (m, 48H), 3.35 (s, 3H), 2.45 (s, 1.05H).
In a 50 mL q-necked flask with reflux condenser and magnetic stirrer was dissolved HPG-mPEG-OTs (200 mg, 0.20 mmol OTs-groups) in anhydrous 1,4-dioxane (10 mL). (Roller, ibid.) After addition of CBG (1 mmol, 5.0 eq.), the resulting suspension was heated to reflux at 115° C. for 24 hours. After cooling the reaction mixture, the mixture was dialyzed in water for three days with periodic changes in water to give a brown honey-like product.
1H NMR (300 MHz, Chloroform-d): δ 3.89-3.43 (m, 35H), 3.38 (s, 3H), 2.87 (m, 9H).
Amine functionalized HPG-mPEG (200 mg, 24 CBG per polymer) was transferred to a 20 mL side-necked flask. The reaction mixture was dissolved in DI water at room temperature. 10 mL of a formic acid/formaldehyde (1:1) mixture was added dropwise to the reaction flask. The reaction was stirred and heated to reflux at 110° C. for 24 hours. After cooling the reaction mixture, the mixture was dialyzed in water for two days with periodic changes in water until the pH of the water was neutral. Upon lyophilizing to remove excess water, MPI 2 was collected.
1H NMR (300 MHz, Chloroform-d): δ 8.11 (s), 4.11-3.19 (m), 3.19-2.95 (m), 2.78-1.94 (m).
Determination of Heparin Reversal Activity by Activated Partial Thromboplastin Time Assay (aPTT)
Stock MPI, UHRA or protamine sulfate solutions were prepared in 20 mM HEPES buffer (pH 7.4 and 150 mM NaCl). Unfractionated heparin (Fresenius Kabi, Canada) or tinzaparin (LEO Pharma, Canada), 4 U/mL and 1 U/mL final concentrations, respectively, were incubated with sodium citrate anticoagulated pooled normal plasma (Affinity Biologicals, Canada) to prepare heparinized plasma, and were used to study the neutralization activity by various MPI and UHRA constructs. The neutralization activity of MPI, UHRA and protamine sulfate on the coagulation cascade was examined by mixing 20 μL of MPI or UHRA or protamine solution with 180 μL of heparin derivative incubated plasma ( 1/10 v/v). The final concentration of MPI, UHRA and protamine in plasma ranged from 0.025 mg/mL to 0.25 mg/mL. 200 μL of aPTT reagent (Dade®Actin®FS Activated PTT, Siemens/Dade-Behring) was then added to the neutralization reagent-plasma sample and 100 μL of this resulting mixture was transferred to cuvette-strips and incubated at 37° C. for 3 minutes. The clotting time was measured on a STart® 4 coagulometer (Diagnostica Stago, France) and began when 50 μL of 25 mM CaCl2) was added into each cuvette. Saline added to plasma with and without heparin-derivatives was used as a control for the experiments. The percentage of neutralization was calculated from the difference in the clotting times observed for MPI/UHRA/protamine versus control saline and heparinized plasma. All experiments were performed with pooled plasma of 20 donors in triplicates and the average values (mean±SD) are reported.
A thrombin generation assay was carried out at 37° C. by measuring the fluorescence intensity upon cleavage of a fluorogenic substrate, Z-Gly-Gly-Arg-AMC by the regenerated thrombin. Commercially available pooled platelet normal plasma (PNP, 30 donors) from George King Bio-Medical, USA was mixed 1:1 with HBS (20 mM HEPES with 100 mM NaCl at pH 7.4). Phosphatidylcholine (80): phosphatidylserine (20) (PCPS) liposomes were added to obtain a final concentration of 25 μM. Serial dilutions of MPI in HBS were prepared fresh each for each experimental replicate and two technical replicates were performed each time. Plasma-liposomes incubated with thrombin-α2-macroglobulin were used as a thrombin calibrator. The thrombin generation assay was initiated by addition of fluorogenic substrate in 60% BSA in HEPES buffer and CaCl2) (0.1M final concentration) to each well with a multichannel pipette. Substrate hydrolysis was monitored with Thrombinoscope™ plate reader. Fluorescence intensity was recorded at 37° C. every 30 seconds over a period of 1.5 hours and analyzed using Thrombinoscope™ software from Diagnostica Stago. For determination of heparin neutralization efficacy, the specific heparin tested would be added directly to the warmed PNP at 37° C. Only the type of heparin was varied: UFH, enoxaparin and Fondaparinux. TF (Thrombinoscope™) was added to initiate clotting at a final concentration of 5 μM.
The level of platelet activation was quantified by flow cytometry. Ninety microliters of PRP were incubated at 37° C. with 10 μL of stock MPI samples for one hour. Ten microliters of post-incubation platelet/polymer mixture were diluted in 45 μL PPP and incubated for 15 minutes in the dark with 5 μL of monoclonal anti-CD62-PE (Immunotech, Marseille, France). The reaction was then stopped with 0.5 mL of phosphate-buffered saline solution. The level of platelet activation was analyzed in a BD FACS Canto II flow cytometer (Becton Dickinson, ON, Canada) by gating platelet-specific events based on their light scattering profile. Activation of platelets was expressed as the percentage of platelet activation marker CD62P-PE (phycoerythrin) fluorescence detected in the 10,000 total events counted. Measurements were performed with PRP from three different donors and mean of which was recorded. Thrombin receptor activator receptor 6 (TRAP6), a known platelet activator (Sigma Aldrich, Oakville, ON, Canada) was used as a positive control for the flow cytometric analysis.
Whole blood collected in sodium citrate anticoagulant mixed with MPI in HEPES buffered saline (HBS) was subjected to a coagulation study using ROTEM® delta from Tem Innovations GmbH (Instrumentation Laboratory as of 2016) at 37° C. Stock solutions of MPI and UHRA were prepared at concentrations 100× the final desired concentration in HBS. Citrate anticoagulated whole blood (356 μL) collected from normal volunteers after informed consent and using an approved UBC protocol was mixed with 44 μL of MPI, UHRA or HBS mixture. The blood mixture (340 μL) was transferred into the ROTEM cup and was re-calcified with 20 μL of 0.2 M calcium chloride solution. As a negative control, HBS (20 mM HEPES+150 mM NaCl) mixed with whole blood was used as control for the experiment. The experiments were repeated with at least 5 different donors and average values are reported. For heparin reversal studies, UFH was included in the 44 μL mixture for a final concentration of 0.5 U/mL and as a positive control no MPI was added. To prepare heparinized blood, 10 000 U/mL stock UFH was added to 4 mL whole blood at 37° C. for a final concentration of 0.5 U/mL. All the experiments were initiated within 10 minutes of blood collection and the clot characteristics such as clotting time and clot strength were measured from the ROTEM generated. Whole blood collected from five donors was used and the mean value with standard deviation was reported.
In Vivo Studies with MPI 2
C57/BL6 mice (8- to 10-week-old) were purchased from The Jackson Laboratories (Bar Harbor, ME), and the experimental protocol was approved by the International Animal Care and Use Committee at the University of Michigan. Mice (N=8) were anesthetized, weighed, and placed on a heated surgical tray. The tail was immersed into 15 mL of pre-warmed (37° C.) sterile saline (0.9% NaCl). To test the bleeding side effects, MPI 2, saline, and heparin, were injected retro-orbitally and allowed to circulate for 5 minutes. The distal tail (5 mm from the tip) was amputated with a surgical blade (Integra Miltex) and immediately re-immersed in 15 mL of pre-warmed (37° C.) sterile saline (0.9% NaCl). The time required for spontaneous bleeding to cease was recorded. After a maximum of 10 minutes, the tail was removed from the saline and the mouse was euthanatized by cervical dislocation. The blood samples were then pelleted at 500 g for 10 minutes at room temperature, the pellet was resuspended in 5 mL of Drabkin's Reagent (Sigma), and then incubated at room temperature for 15 minutes. The amount of hemoglobin lost was quantified by comparing the absorbance of the samples at 540 nm to a standard curve of bovine hemoglobin in Drabkin's reagent.
To test the ability of MPI 2 to reverse the activity of heparins in mice, the same mouse tail bleeding model as described above was used, except for the following exception. Mice were first injected retro-orbitally with either unfractionated heparin (200 U/kg) or enoxaparin (200 U/kg) which was allowed to circulate for 5 minutes. Mice were then injected retro-orbitally with either MPI 2, or saline, circulated for 5 minutes prior to tail tip amputation. All other experimental details were the same.
Inhibitors were incubated with 50% plasma spiked with 67.11 μg/mL of LMW poly IC for 45 minutes at room temperature followed by 3 minutes incubation at the 37° C. Clotting was triggered in Stago Start 4 coagulometer by 10 mM calcium, 1:15000 diluted re-lapidated tissue factor and PCPS vesicles. For concentration dependent studies, 20 μg/mL HMW poly IC was used.
Inhibitors were incubated with 50% plasma spiked with 100 g/mL of HMW poly IC for 45 minutes. S2302 substrate activity in plasma was monitored by measuring absorbance for 1 hr at 37° C. at 405 nm. Initial maximum velocity of the reaction was calculated and plotted with concentration.
Thrombin generation was measured by calibrated automated thrombography. Commercially available pooled platelet normal plasma (PNP, 30 donors) from George King Bio-Medical, USA was incubated with nucleic acids with or without the inhibitor at 37° C. for 45 minutes. 80 μL of this mixture was mixed with 20 μL of Stago's PPP low reagent in clear round-bottom immuno 96-well plates from Thermo Fisher. Thrombin generation was triggered using 20 μL of FluCa reagent and measured in a thrombinoscope.
Plasma clot lysis assays were performed by triggering 30% commercially available pooled platelet normal plasma (PNP, 30 donors) from George King Bio-Medical, USA with 0.04IU/mL thrombin, 20 mM calcium and 70 ng/mL tissue Plasminogen Activator(tPA). The lysis was monitored by measuring absorbance at 405 nm for 10 hrs.
The protocol for blood collection from human subjects in the Centre for Blood Research at the University of British Columbia has been approved by the Institutional Review Board (IRB) within the University of British Columbia (UBC Ethics approval no: H10-01896) with written consent obtained from donors.
Blood was drawn from consenting informed healthy volunteer donors at Centre for Blood Research, University of British Columbia, in BD Vacutainer® Citrate Tubes containing 3.2% buffered sodium citrate solution. Blood was centrifuged at 150×g for 10 minutes to separate platelet-rich plasma (PRP), and then spun at 1000×g for 15 minutes for platelet-poor plasma (PPP). Pooled normal plasma (PNP) from 20 donors was purchased from Affinity Biologicals (ON, Canada).
Specificity of MPI 8 Toward polyP in ADP-Mediated Platelet Activation
Human whole blood collected was into 3.8% sodium citrate tubes. Tubes were then centrifuged at 156×g for 12 minutes to generate platelet-rich plasma (PRP). The influence of MPI 8 on ADP-mediated platelet activation was assessed in 2 ways. In both cases, the final concentration of ADP was 40 μM. In the first approach, MPI 8 was pre-mixed with ADP (10 μL total) immediately before the addition of 90 μL of PRP, and the resulting suspension was incubated for 15 minutes at 37° C. In the second, PRP was pre-incubated with MPI 8 for 1 hour at 37° C. before activation with ADP (15 minutes at 37° C.). Controls containing PBS alone (vehicle) as well as ADP without MPI 8 were also included. Activation was then assessed by flow cytometry (CytoFLEX Flow Cytometer, Beckman Coulter). Briefly, 5 μL of PRP suspension was added to 50 μL of PBS containing 20×-diluted anti-human CD62P-PE (BD Biosciences). Platelets were gated based on anti-human CD42-FITC (BD Biosciences), prepared in the same manner. Using this gate, 10,000 events were counted, and activation was quantified by the percentage of cells positive for CD62P.
The structure of the macromolecular polyanion inhibitors (MPIs) of the present invention provides 2 components: A charge switchable cationic binding group (CBG); and a biocompatible scaffold as illustrated in
Two novel cationic binding groups were identified based on a comparison of multiple synthetic and biologically derived amine structures reported in the literature (Table 1): CBG I (linear amine with two-carbon alkyl linker) and CBG II (linear amine with three-carbon alkyl linker) are depicted in
Preferred polymer scaffolds covalently conjugate to the selected CBGs in the MPIs. We created a library of MPIs with a varying number of different CBGs on different scaffold sizes, to identify the optimal protonation pattern for MPIs to bind polyP. We have identified a scaffold with hyperbranched polyglycerol (HPG) core attached with a swollen PEG corona that accounts for approximately 30 mol % of final copolymer scaffold (HPG-PEG). The PEG corona provided sufficient graft density to generate brush layer to prevent non-specific interactions. (Shenoi, ibid, Kalathottukaren and Abbina, ibid.) Selection of this HPG-PEG scaffold allows testing of the switchable protonation state and local recruitment of protons by CBGs upon its binding to polyP without the influence of other factors.
Two distinct HPG-PEG core scaffold sizes with 10 kDa and 20 kDa molecular weight were developed. Post functionalization of the HPG-PEG scaffold with different CBG groups at different densities provided the generation of a library of the MPI candidates for evaluation (Table 2).
aObtained from GPC-MALLS.
bObtained from conductometric titrations.
cObtained from potentiometric titrations.
Another polycationic polymer was prepared from our generation of compounds (UHIRA), to serve as a reference from which the improved activity and increased biocompatibility of the novel MIPI candidates can be measured. Detailed characteristics of the MPI candidates including their NMR spectra, conductometric titration curve, GPC profiles are provided in
Using CBGs with multiple alkylamines with different protonation constants, MPIs were generated whose protonation state was switchable, presenting a low charge density at physiological pH but adopting a highly charged state when binding to polyP due to the highly anionic microenvironment surrounding the polyP partner after the binding event. These MPIs provide the solution with one or two amine residues on CBG protonated prior to polyP binding are able to support up to three charges per CBG with an energetic incentive to adopt this conformation. (Gohlke, H. and Klebe, G. Approaches to the Description and Prediction of the Binding Affinity of Small-Molecule Ligands to Macromolecular Receptors. Angew. Chem. Int. Ed. 2002, 41 (15), 2644-2676., and Barril, S et al. Salt Bridge Interactions: Stability of the Ionic and Neutral Complexes in the Gas Phase, in Solution, and in Proteins. Proteins 1998, 32 (1), 67-79.)
The pKa values of the amines on the overall MPI structure determined the ability of each amine on the final MPI structure to accept a proton, depending on its local electronic environment. Each CBG candidate was carefully selected for protonation properties. Both CBG I and CBG II present two amines with pKa >7.4, indicating the likelihood of being protonated at physiological conditions. The 2 amines are on the extremities of the CBG structure (
HL
H2L
H3L
H4L
Potential in mV was measured as standardized base (0.15 M NaOH) was titrated into acidified (pH 2) solution of CBG or MI at 25° C., 160 mM NaCl.
After determining the structure and characterization of protonation of the MIPIs, we investigated their polyP inhibition capabilities. Using surface plasmon resonance (SPR), the binding affinity of each MPI towards two chain lengths of surface bound polyP long chain (LC) and medium chain (MC) polyP, long chain (LC) polyP (characterized as having hundreds to thousands of phosphate units, in this case a mode of 1070 phosphate units), and MC polyP approximately half the size with a mode of 560 phosphate units, were compared in this high-throughput experiment. Results are provided in Table 4 and
Differences were observed in binding between MPIs with different CBGs, with the smallest dissociation constants observed for the Me6TREN ligand, with CBG II and CBG I showing slightly weaker binding affinity, albeit still sub-micromolar. The stronger binding of the Me6TREN ligand may be explained by the higher pKa of the second and third protonation compared to the bare CBG I and CBG II ligands (Table 3), resulting in a higher charge density at physiological pH for Me6TREN based UHRA (Table 2). The slightly increased binding strength of the CBG II based MPIs (MPI 4, MPI 5, MPI 8, and MPI 9) over those based on CBG I (MPI 1-MPI 3, MPI 6, and MPI 7) may therefore be attributed to the charge spacing on CBG II being more amenable to binding with the polyP anionic backbone. Furthermore, improved binding may be due to the increased charge density upon binding with CBG II due to the lower pKa of a second protonation event due to reduced strain induced by reduced electrostatic repulsion of the adjacent cationic amine residues when spaced by propyl linkers rather than the ethyl bridging groups used in CBG I.
Analysis of MPI Binding to polyP Via Isothermal Titration Calorimetry
Isothermal titration calorimetry (ITC) analyses were performed with MPIs of the present invention. The association constant (Ka) of the MPIs relative to different polyP chain lengths were measured. As well, the thermodynamic data of the binding reaction including the free energy (ΔG), the enthalpy (ΔH) and stoichiometry (N) of the binding reaction were obtained, as indicia of the driving force, strength and stability of the reaction (Table 5 and Table 6).
aUsed in the ITC cell.
b Added to cell via syringe.
c Ratio of MPI to polyP.
dBuffer used was sodium phosphate buffer composed of dibasic phosphate buffer (Na2HPO4), monobasic phosphate buffer (NaH2PO4) and NaCl. NaCl concentration is 10 mM.
eBuffer used was HEPES buffer consisted of HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and NaCl.
aPhosphate buffered saline (PBS): 10 mM dibasic phosphate buffer (Na2HPO4), 2.7 mM KCl and 137 mM NaCl.
bSodium phosphate buffer: dibasic phosphate buffer (Na2HPO4), monobasic phosphate buffer (NaH2PO4) and NaCl.
cHEPES buffer consisted of HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) and NaCl.
Titration ITC curves and binding curves for small molecule CBG and MPI 3 with LC polyP are provided in
The binding affinities of MPI 3 toward different chain lengths of polyP (P45, P75, P700) (Table 5, Table 6) do not significantly change, indicating relative insensitivity of the MPI to the size of the polyP. Representative titrations for all binding pairs studied are shown in
When comparing MPI 1 and MPI 3, two MPIs with the same size scaffold and same CBG structure but different in the number of CBGs attached, apparent binding affinity increased with an increase in charge. This indicates that not all charges present on the MPI cores may be necessary for the binding to polyP. The binding affinities of MPI 3 toward different chain lengths of polyP (P45, P75, P700) (
A comparison of MPI 9 and MPI 5 (
In experiments conducted in the development of the present invention, we investigated the switchable protonation properties of MPIs using ITC experiments. The ITC analysis showed that even though MPIs have lower charge at physiological pH, comparable binding affinities are observed when compared to the higher charge density UHRA due to the switchable protonation states associated with our CBGs of the present invention on binding to polyP. This results in a higher cationic charge density for MPI upon binding to polyP. In the selected CBGs, a second protonation is possible with pKa of 6-7.
Potentiometric titration analyses demonstrate that the CBGs of the present invention exhibit slightly more than one positive charge per ligand at physiological pH, indicating that once MPI is partially bound to the polyanionic partner, the local dielectric conditions surrounding the binding site due to the presence of a high density of negative charges stabilize an additional CBG protonation. This causes in an increased population of doubly protonated CBGs, whose additional proton is acquired via proton recruitment from the aqueous surroundings, thereby resulting in higher cationic charge density on the MPI on polyP binding, and stabilizing the multidentate binding reaction without requiring a highly cationic conformation at physiological pH.
To confirm the switchable protonation ability of the generated MPIs, a series of ITC measurements were conducted using several buffers with a range of values for ΔHion,buffer0. If proton recruitment plays a significant role in the binding process, the effect of the heat of ionization of the buffer will be observed as a change in the observed ΔHexp0. Therefore, to confirm the role of proton recruitment in the MPI-polyP binding process, the observed ΔHexp0 was measured in different buffers and plotted against the ΔHion0 on of each buffer. (Goldberg, R. et al. Thermodynamic Quantities for the Ionization Reactions of Buffers. J. Phys. Chem. Ref Data 2002, 31 (2), 231-370.) (
Effects of MPI Binding on polyP Via 31P NMR
While ITC experiments indicate the behavior of the amine functionalities on the CBGs during the MPI-polyP binding event, the effect of the MPI on the polyP phosphate backbone have previously been unknown. To determine the interaction between the MPI and polyP backbone, and how the interaction effects the electronic environment of the phosphorus nuclei, 31P NMR titration experiments were performed. PolyP of 45 chain length was used for the measurement because for this molecule both internal and terminal phosphorus units may be visualized. In these experiments, the binding properties of small molecule CBGs were compared directly to the behavior of the same CBGs bound to an MPI (
Upon titrating polyP (P45) with MPI 3 and CBG I, a distinct binding behavior was observed. This titration showed only one major internal phosphate peak at each concentration of CBG I tested, with approximately equal intensity between the runs (
The interaction between MPI 3 and P45 does not exhibit this behavior. The 31P NMR spectra obtained during the binding of polyP to MPI showed the phosphorus nuclei exists in two potential states, an unbound state and a bound state (
These observations indicate that the multivalent nature of the MPI-polyP binding event results in a much stronger interaction than would be expected for just the small molecule CBG I alone, even with a much higher molar equivalent (millimolar range). This experiment was carried out with a representative 20 kDa MPI, MPI 3 with P45, as a direct comparison to CBG I, as well as additional experiments with MPI 3 and P700 and MPI 9 with P45 to demonstrate the consistency of this binding behavior over different core sizes, CBGs, and polyP binding partners (
In addition, observing the electronic behavior of the phosphorus nuclei by 31P NMR while slowly titrating a consistent amount of MPI 3 enabled the visualization of the identity of phosphorus on the entire chain that would first bind to MPI. Upon the initial addition of MPI, a change in chemical shift was observed for the internal phosphorus groups, while the terminal phosphorus peaks remained unchanged (
Inhibition of Long Chain polyP Measured by Plasma Clot Time
Plasma clotting triggered by recalcification and LC polyP (P700) was used to investigate the inhibition activity of MPI candidates. LC polyP, UHRA-8 and buffer were used as controls. The ability of MPIs to inhibit the procoagulant effects of polyP is shown in
Inhibition of Long Chain and Short Chain polyP Via Thrombin Generation Measurement
Thrombin generation was investigated in presence of LC and SC polyP using calibrated automated thrombography, a sensitive method for evaluating the effect of the added blood coagulation modulators. In this assay, a calibrated fluorogenic substrate is used to infer the quantity of thrombin generated. Addition of LC polyP, a potent activator of clotting, significantly shortens the clot time of plasma, while the addition of MPI normalized the thrombin generation curve (
The inhibition potential of MPI against SC polyP was investigated by measuring plasma clotting triggered by tissue factor (TF), using thrombin generation assay. While SC polyP (platelet sized polyP) is a less potent activator of the contact pathway, it plays many roles in the downstream events of clotting and remains a useful target to develop antithrombotic agents. Less pronounced effects are seen than in the case of LC polyP in thrombin generation; the short chain polyP remains a strong accelerant for blood clotting (
A titration of the MPI candidate library provides a dose dependent response of short chain polyP inhibition, normalizing thrombin generation parameters to that of the buffer control (
While MPI compounds and UHRA-10 generated classical sigmoidal dose-response curves which could be fitted using the Hill equation, UHRA-8 did not fit this model. The effects of each MPI on plasma clotting triggered by LC polyP on 4 clotting parameters were assessed. Since LC polyP is a potent activator of the contact pathway, the lag time was taken as the primary parameter affected by the addition of LC polyP, and was used to generate the IC50 of each MPI. This methodology was also used to determine the half maximal inhibitory concentration of each MPI towards SC polyP in this plasma clotting system. While a range of IC50 values towards SC and LC polyP were observed for each MPI and UHRA compounds, all 20 kDa and 10 kDa MPI candidates demonstrated a lower IC50 value towards LC polyP than UHRA-8 and UHRA-10 respectively (Table 7). Moreover, MPI compounds of the present invention possess significantly less charge than their UHRA (about half to two thirds lower), and no significant loss of inhibition efficacy against both LC and SC polyP was observed.
Biocompatibility of MPI Candidates—Low Charge State of MPI Resulted in High Compatibility with Blood Components and Blood Clotting In Vitro.
To characterize the hemocompatibility of the MPI library, the effect of the polycationic molecules on plasma clotting kinetics was tested in the absence of added polyP. Previous studies on polycations have shown that they adversely impact blood coagulation. (Malik, N. et al. Relationship between Structure and Biocompatibility in Vitro, and Preliminary Studies on the Biodistribution of 125I-Labelled Polyamidoamine Dendrimers in Vivo. J. Control. Release Off. J. Control. Release Soc. 2000, 65 (1-2), 133-148., and Moreau, ibid.) Additionally, we investigated the effect of MPI candidates on whole blood coagulation, platelet activation and their influence on clot structure. These in vitro studies together with polyP inhibition activity allowed us to identify lead candidates for further investigation in vivo using mouse models.
To demonstrate the utility of the charge-switchable MPIs over previously reported polyP inhibitors, the biocompatibility and activity in vitro of these MPIs were characterized. The blood compatibility of the MPIs were measured using blood clotting analysis using pooled normal human plasma of each MPI relative to a buffer control (
Further advantages of the low charge state of MPIs at physiological conditions were evidenced by their compatibility with blood components, such as platelets. Platelets can be activated by polycations such as PEI and PAMAM dendrimers which cause clotting complications and affect normal hemostasis. (Jones, ibid.) Platelet activation in presence of MPI in comparison to other controls are shown in
Additional assessment of the influence of MPIs on the clotting characteristics of human whole blood containing all of its components demonstrated no significant effect on the clot time or maximum clot firmness compared to the negative control with no MPI added (
The clotting properties of citrated pooled PPP were assessed in a turbidity microplate assay in the presence of two different concentrations (75 and 200 μg/mL) of MPIs. Clotting was initiated by recalcification and the time taken to form a turbid clot from absorbance measurement was taken as the lag time. (Carter A. M. et al. Heritability of Clot Formation, Morphology, and Lysis. Arterioscler. Thromb. Vasc. Biol. 2007, 27 (12), 2783-2789.) We used UHRA-10, UHRA-8, UFH, protamine and buffer as controls added to PPP. Any significant deviation in lag time by the MPI candidates with respect to buffer control is considered as a change in clotting profile. As shown in
We investigated the influence of MPI on clotting in a TF-initiated system measured on a coagulometer using FXII deficient plasma. In addition to MPI candidates, control polyP inhibitors and buffer control were evaluated. Results are shown in
MPI influence on thrombin generation in TF-initiated plasma clotting
In view of the minimal effect of MPIs on clot time in the coagulation assays described, we further characterized the influence of the MPI library on the clotting process. This was performed utilizing a calibrated automated thrombography analysis, e.g., a thrombin generation assay (TGA). This assay provides enhanced sensitivity to thrombin generation, providing more insight into the effect MPI has on the clotting process by allowing for measurement of the quantity of thrombin generated over time compared to other methods. This assay also provides a direct method to measure additional parameters including endogenous thrombin potential, time to peak thrombin, and peak thrombin concentration.
Preferred MPIs exhibit minimal deviation over a range of concentrations from the buffer control in the case of thrombin generated over time, while maximizing the polyphosphate inhibition effects. Each of the parameters that can be extracted from thrombin generation assays, as shown in
Although favorable compatibility behavior is seen in MPI 2 and MPI 4, neither produced efficient high polyP inhibition. Furthermore, all the MPI compounds exhibit less impact on thrombin generation than that observed for UHRA-8 and UHRA-10, thereby highlighting the enhanced compatibility and minimal effect on hemostasis that this new family of polyphosphate inhibitors possesses.
Selected lead MPI agents were further characterized in depth to investigate their compatibility with more complex and sensitive systems. These measurements were performed to confirm that the MPI candidates do not exhibit incompatibility with blood components that might preclude them from therapeutic applications, an issue that is common to many conventional polycationic macromolecules. These studies also confirm that the new design of molecules resulted in significant improvements, which were enabled by their switchable protonation behavior and minimal charge under physiological conditions.
Platelet activation was determined via expression of platelet activation marker CD62P in human platelet rich plasma (PRP) after incubation with MPIs. TRAP-6 treated platelets were used as a positive control and buffer added to PRP was a normal control. The degree of platelet activation was measured via flow cytometry with results shown in
Because the interaction of whole blood provides a closer representation of exposure to MPI polyP inhibitors, for example, during injection into the body the influence of MPIs on whole blood clotting were investigated. Blood components include many anionic biomolecules and blood cells that can potentially interact with these polycations via undesired non-specific pathways. Therefore, demonstrating compatibility with whole blood clotting is critical to establish the biocompatibility of these compounds. This information was obtained by measuring the whole blood clotting using rotational thromboelastometry (ROTEM). ROTEM measurements are considered to be closer to in vivo conditions than other coagulation assays because all blood components are present. (Bolliger, D. et al. Principles and Practice of Thromboelastography in Clinical Coagulation Management and Transfusion Practice. Transfus. Med. Rev. 2012, 26 (1), 1-13.) The clot time of whole blood, and strength of the final clot formed in presence of lead MPI compounds of the present invention, along with UHRA-8 and UHRA-10 were measured.
Buffer added to whole blood was used as a normal control. As shown in
Influence of MPIs on fibrin clot morphology and fibril thickness To investigate the influence of MPIs of the present invention on final clot structure, clot structure was visualized using scanning electron microscopy. By comparing the fibrin clots formed in the presence and absence of MPIs, the influence of MPI on clot morphology and fibrin dimensions may be observed. As shown in
In addition, we tested whether the addition of MPIs normalize clot structure formed in the presence of polyP. Fibrin clots formed in the presence of polyP, MPI 8 alone, MPI 8 together with polyP and buffer control were investigated using scanning electron microscopy (SEM). Micrographs obtained from SEM showing the clot microstructure and the calculated fibrin thickness are illustrated in
Based on the in vitro studies detailed above, MPIs 1, 6, and 8 demonstrate strong binding behavior with minimal nonspecific interactions. MPIs 1, 6, and 8 also exhibited efficient reversal of both SC and LC polyP in human plasma. Investigations of the antithrombotic activities of MPI 1, 6, and 8, were performed in a mouse cremaster arteriole thrombosis model using intravital microscopy. MPIs were injected and the platelet accumulation and fibrin deposition were measured in comparison to the buffer control. Platelets and fibrin were then labelled with fluorescent antibodies to allow direct observation of the clot formation process. Clotting was then initiated via laser injury to the cremaster arteriole followed by observation of the clot formation over time, as shown in
The ability of MPI 8 to inhibit mouse carotid artery thrombosis in a FeCl3 model was evaluated, wherein topical application of FeCl3 was used to induce thrombosis (
In vivo assessment of MPI safety—mouse tail bleeding
In view of the positive results over the broad range of in vitro and ex vivo measurements used to probe the biocompatibility of the MPI library, MPIs of the present invention were selected for further in vivo studies. To investigate the safety of the MPI candidates, mice were treated with high doses of MPI to confirm three key parameters: bleeding effect, acute toxicity, and long-term toxicity. The effect of the MPIs on bleeding was assessed in a mouse-tail bleeding model. In this experiment, mice were treated with the 3 MPIs, as well as saline and UFH as normal and positive controls, respectively. Following injection of MPI or controls, the bleeding time and hemoglobin loss were recorded after a tail clip to determine bleeding. As shown in
In vivo assessment of MPI safety—acute toxicity Based on the antithrombotic activity of MPI compounds, MPI 8 was selected for a dose tolerance study. A single escalating dose tolerance study in mice was performed to determine the acute toxicity. Mice were injected with MPI 8 intravenously at high doses (250 mg/kg and 500 mg/kg) and sacrificed after 24 h. Mice injected with saline were used as a control. Determination of LDH, AST and ALT levels in serum was used as a measure of acute toxicity. As shown in
The long-term effects of exposure to MPI 8 in mice was quantified using an escalating dose injection study (100 to 500 mg/kg). Over the course of the 14-day study, mice body weights were monitored, as shown in
A schematic representation of MPIs as heparin reversal agents is shown in
Following structural characterization of the MPI library, heparin reversal activities of MPIs were determined in vitro using heparinized pooled normal plasma. As a method to determine optimal activity against LMWH (tinzaparin in this case) and UFH, the MPI library was screened using an activated partial thrombin time (aPTT) coagulation assay. A known heparin reversal agent, UHRA (Travers, ibid, Kalathottukaren and Abraham, ibid) was re-synthesized and used as a reference with demonstrated heparin reversal ability in plasma. To identify suitable MPIs for heparin reversal, the clot time was measured for each MPI at several concentrations as shown in
A preferred heparin antidote would demonstrate effective heparin reversal activity starting at a low concentration over a wide range of doses to ensure a broad therapeutic window, with activity unchanged over the range of concentrations examined. Of the compounds, MPIs 3, 5, and 7 demonstrated increased clotting time at higher concentrations of MPI, with significant deviances from the non-heparinized (buffer) control at a concentration of 150 μg/mL. MPI 2, on however, demonstrated complete heparin reversal and virtually unchanged clotting times in the dose range explored, from 10 to 50 μg/mL with tinzaparin (I U/mL), and 25 to 150 μg/mL with UFH (4 U/mL). In comparison to UHRA, this represents an increased activity for MPI 2, and the neutralization activity of MPI did not change over a range of concentrations studied. These results were further confirmed in a calibrated automated thrombography assay of all MPI compounds in heparinized (UFH, 0.5 U/mL) plasma by measuring thrombin generation (
To further investigate the efficacy of MPI 2 as a universal heparin reversal agent, calibrated automated thrombography was used to evaluate the impact of MPI on thrombin generation in heparinized plasma. The amount of thrombin generated was assayed by measuring fluorescence intensity over time using a fluorogenic substrate calibrated to thrombin (
Beyond demonstrating high heparin neutralization activity of MPI 2, the results from thrombin generation curves demonstrate that upon reversal of the heparin therapeutic, clotting properties in neutralized samples return to conditions analogous to those observed when no heparin was added to the plasma as in the buffer control. This is shown in
To determine the range of concentrations that MPI is effective against UFH, the neutralization activity of MPI 2 was compared to both commercially available protamine sulfate (PS) and UHRA. The dose range studied was from 0-250 μg/mL. As shown in
The same assay was performed with plasma that was heparinized with a LMWH, tinzaparin. This experiment is critical because it highlights the significant increase in utility of MPI 2 over PS as a heparin antidote. PS has almost no neutralization activity on LMWH, shown in
To determine whether the heparin reversal activity of MPI 2 persists in whole blood, rotational thromboelastometry (ROTEM) was performed. This viscoelastic method allows for direct investigation of the effect of anticoagulant alone (UFH) as well as the effect of added heparin antidotes (MPI 2 and UHRA are shown above, and
MPI 2 Compatibility with Blood Components and Whole Blood Clotting in the Absence of Heparin—Flow Cytometry
While heparin reversal efficacy is a key property of the MPI compounds of the present invention, a heparin antidote must further exhibit hemocompatibility to be used as a safe heparin reversal agent, and the antidote must not interfere with normal hemostasis, clot properties or clot severity whether bound to heparin or freely circulating. Accordingly, we determined whether the addition of MPIs of the present invention to whole blood have an impact on hemostasis. To demonstrate that even at extremely high doses, MPIs do not induce platelet activation, (activation of platelets is a frequent effect of highly positively charged macromolecules, such as polyethyleneimine (PEI) or polyamidoamine (PAMAM) dendrimers (Dubois, ibid, Hu, ibid)), platelet activation in platelet rich plasma (PRP) was studied using flow cytometry. When compared to positive and negative controls, thrombin receptor activating peptide 6 (TRAP) and buffer/platelet poor plasma respectively, addition of MPI 2 did not cause an increase in platelet activation, even at concentrations as high as 200 μg/mL, while the IC50 in plasma of MPI 2 ranged from 1-5 μg/mL towards various heparins.
MPI 2 Compatibility with Blood Components and Whole Blood Clotting in the Absence of Heparin—ROTEM
To further demonstrate the compatibility of MPI 2 with blood components, blood coagulation in whole blood using ROTEM was performed (
The efficacy of MPI 2 as a universal heparin reversal agent in vivo was determined using a mouse tail bleeding model. Mice were administered either 200 U/kg UFH or 200 U/kg enoxaparin followed by the antidote (MPI 2) or negative saline control. The bleeding time was recorded, and the hemoglobin loss was quantified. To examine the effect of MPI 2 as a UFH antidote, two MPI 2 doses were studied. When given 20 mg/kg of MPI 2, bleeding times and hemoglobin loss were both significantly decreased relative to UFH alone, however, when the dose was increased to 30 mg/kg, bleeding times and hemoglobin loss were decreased to levels similar to the saline control (
MPI 2 does not Affect Bleeding in Mice in the Absence of Heparin
To determine the effect of MPI heparin antidotes of the present invention on bleeding in vivo, a mouse tail bleeding model was used in the absence of heparins. C57/BL6 mice were administered doses of MPI 2 that were five-fold (100 mg/kg) and ten-fold (200 mg/kg) the therapeutic doses demonstrated in the heparin reversal studies above. As illustrated in
To determine the activities of MPIs as nucleic acid inhibitors. PolyIC (Polyinosinic:polycytidylic acid) was used as a nucleic acid for this screening studies of MPI compounds of the present invention. A plate-based coagulation assay was used to compare candidate compounds Data is shown in
Thrombotic complications and cytokine storm are hallmarks of disease conditions such as sepsis. Organ damage associated with such complications is highly prevalent. Extracellular DNA-induced activation of blood coagulation and induction of inflammation may occur. Molecules which can prevent extracellular DNA-induced blood coagulation are hypothesized to prevent such complications. MPI 3 is directed against the polyanionic neutrophil extracellular traps (NETs) that neutrophils release in response to infection. To ensure inhibitor bioavailability throughout the study, 3 three doses of MPI 3 were administered every 2 hours after CLP surgery. Eight hours after surgery, mice were euthanized, and blood was collected for further analysis.
Studies were designed to evaluate the specificity of MPI 8 as a polyP inhibitor. Adenosine diphosphate (ADP) is a naturally occurring negatively charged phosphate containing molecule. We investigated whether polycationic MPI 8 binds to ADP (which is anionic) and alters its activity. For this purpose, we used an assay studying ADP-mediated platelet activation.
The saphenous vein hemostasis model was used to assess hemostatic clot formation at the site of vascular injury following laser-induced rupture of the saphenous vein wall under intravital microscopy, with results shown in
All publications and patents mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described method and system of the disclosure will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. Although the disclosure has been described in connection with specific embodiments, it should be understood that the disclosure as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the disclosure that are obvious to those skilled relevant fields are intended to be within the scope of the following claims.
This invention was made with government support under HL120877 and HL135823 awarded by the National Institutes of Health. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US22/44259 | 9/21/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63247635 | Sep 2021 | US |
