Patent Grant
11965160
This application is being filed electronically via EFS-Web and includes an electronically submitted Sequence Listing in .txt format. The .txt file contains a sequence listing entitled “2017-09-18 5667-00413_ST25_Seq_Listing.txt” created on Sep. 18, 2017 and is 35,071 bytes in size. The Sequence Listing contained in this .txt file is part of the specification and is hereby incorporated by reference herein in its entirety.
The invention generally relates to compositions and methods for preventing and treating thrombosis. More specifically, the invention relates to Von Willebrand Factor (VWF)-targeting agents and their use in preventing blood clotting (anti-thrombotic activity) and treating and/or reducing formed blood clots (thrombolytic activity).
Thrombosis is a major underlying problem in many cardiovascular and cerebrovascular diseases and is also a major post-surgical complication. Antithromotic drugs have been developed over the past 25 years with the goal of reducing the complications associated with cerebrovascular and cardiovascular disease. However, while reducing thrombotic events in patients, these drugs create a challenge with regard to hemorrhagic risk due to the lack of rapid and predictable reversibility.
Aptamers are single-stranded nucleic acids that adopt specific secondary and tertiary structures based on their sequence which enables specific binding to their target. Aptamers can bind to and inhibit protein targets. They are commonly generated by an in vitro selection process called SELEX (Systematic Evolution of Ligands by EXponential enrichment). See, e.g., Ellington A D, Szostak J W. 1990. In vitro selection of RNA molecules that bind specific ligands, Nature 346:818-22; Tuerk C, Gold L. 1990. Systematic evolution of ligands by exponential enrichment: RNA ligands to bacteriophage T4 DNA polymerase, Science 249:505-10. Aptamers can be systematically isolated to virtually any protein and may undergo extensive molecular modifications to optimize their pharmacokinetics for an intended use. Pegaptanib sodium, developed to treat macular degeneration, was the first aptamer approved for use and other compounds are in development. See, e.g., Wang P, Yang Y, Hong H, Zhang Y, Cai W, Fang D. 2011. Aptamers as therapeutics in cardiovascular diseases. Curr Med Chem 18:4169-74. Aptamers offer a promising safer class of anti-thrombotics given that aptamer activity may be rapidly reversed using universal or rationally designed antidotes. See, e.g., Rusconi C P, Scardino E, Layzer J, Pitoc G A, Ortel T L, et al. 2002, RNA aptamers as reversible antagonists of coagulation factor IXa, Nature 419:90-4; WO/2008/066621 A3; and WO/2008/121354.
Von Willebrand Factor (VWF) is a promising target for aptamer-based anti-thrombotics. VWF is a multimeric plasma glycoprotein that binds to glycoprotein IbIX, resulting in platelet adhesion—the first non-redundant step in platelet aggregation, resulting in a thrombus. The basic subunit is 260 kDa and is produced in endothelium and platelets. VWF is required for normal hemostatic plug formation and is a carrier protein for factor VIII. Aptamers targeting VWF have been shown to inhibit the formation of blood clots. See, e.g., WO/2008/066621 A3.
There is a need in the art, however, for new VWF-targeting aptamers having increased stability against nuclease degradation, smaller sizes to facilitate chemical synthesis, and increased circulation times in vivo.
Provided herein are VWF-targeting aptamer compositions and antidote compositions targeting such aptamer compositions as well as methods for preventing and treating blood clots using VWF-targeting agents.
In one aspect, aptamers are provided. The aptamer may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 1 and SEQ ID NO: 2, or any one of SEQ ID NOs: 3-102. See Tables 1 and 2 below.
Alternatively, the aptamer may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to a polynucleotide comprising from 5′ to 3′ a first stem forming region comprising or consisting of 2, 3, 4, or 5 nucleotides, a first loop region comprising or consisting of the nucleotide sequence AAC, a second stem forming region comprising or consisting of 3, 4, or 5 nucleotides, a second loop region comprising or consisting of the nucleotide sequence CC, a third stem forming region consisting of 2-8 nucleotides, a third loop region consisting of 1-12 nucleotides and/or a spacer sequence, a fourth stem forming region consisting of 2-8 nucleotides and capable of forming a stem with the third stem forming region, a fourth loop region comprising or consisting of the nucleotide C, a fifth stem forming region comprising or consisting of 3, 4, or 5 nucleotides and capable of forming a stem with the second stem forming region, a fifth loop region comprising or consisting the nucleotide sequence CAGA, and a sixth stem forming region comprising or consisting of 2, 3, 4, or 5 nucleotides and capable of forming a stem with the first stem forming region.
In some embodiments, the aptamers described herein may be no more than 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, or 16 nucleotides in length. In some embodiments the polynucleotide comprises unmodified nucleotides. In other embodiments, the polynucleotide comprises a modified form having at least one nucleotide base modification. The nucleotide base modifications include a 2′ O-methyl or 2′ fluoro modification of the nucleotide.
In some embodiments, the dissociation binding constant of the aptamer for vWF (Kd) is less than 500 nM, less than 100 nM, less than 50 nM, less than 10 nM, less than 5 nM, less than 3 nM, or less than 2 nM.
In another aspect, dimers, trimers, and tetramers including the aptamers described herein are also disclosed.
In another aspect, antidotes to the aptamers described herein are provided. The antidotes may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 103-180 (the nucleotide sequences in Table 3). Alternatively, the antidote may include a polynucleotide having sequence reverse complementary to and capable of hybridizing to at least 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or more nucleotides of any one of the aptamers described herein.
In a further aspect, pharmaceutical compositions including any of the aptamers or antidotes described herein are provided. The pharmaceutical compositions may include a pharmaceutical carrier, excipient, or diluent (i.e., agents), which are nontoxic to the cell or mammal being exposed thereto at the dosages and concentrations employed.
In another aspect, methods for preventing blood clot formation in a subject are provided. The methods may include administering to the subject any one of the aptamer compositions described herein in a therapeutically effective amount to prevent blood clot formation in the subject.
In a further aspect, methods for treating a blood clot in a subject are also provided. The methods may include administering to the subject a VWF-targeting agent in a therapeutically effective amount to reduce the blood clot in the subject.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The present disclosure is based, in part, on the inventors' discovery of new optimized reversible VWF-targeting aptamers useful for both preventing (anti-thrombotic activity) and treating (thrombolytic activity) blood clots. Compared to previous VWF-targeting aptamers, the presently disclosed VWF-targeting aptamers have increased stability against nuclease degradation, are smaller in size to facilitate chemical synthesis, and demonstrate increased circulation times in vivo.
Disclosed herein are compositions of aptamers and antidotes as well as methods for preventing and treating blood clots in a subject using VWF-targeting agents such as the newly discovered VWF-targeting aptamers. These compositions and methods may be useful in several applications including, without limitation, prevention or treatment of thrombi (in vitro, in vivo, or ex vivo), or the prevention or treatment of thrombi associated with stroke, cerebrovascular thrombi, deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation, coronary artery thrombus, intra-cardiac thrombi, post-surgical thrombi, cancer-induced thrombosis, cancer-related thrombin expression, infection, and disseminated intravascular coagulation (DIC).
Aptamers are provided herein. As used herein, the term “aptamer” refers to single-stranded oligonucleotides that bind specifically to targets molecules with high affinity. Aptamers can be generated against target molecules, such as VWF, by screening combinatorial oligonucleotide libraries for high affinity binding to the target (See, e.g., Ellington and Szostak, Nature 1990; 346: 8 18-22 (1990), Tuerk and Gold, Science 249:505-10 (1990)). The aptamers disclosed herein may be synthesized using methods well-known in the art. For example, the disclosed aptamers may be synthesized using standard oligonucleotide synthesis technology employed by various commercial vendors including Integrated DNA Technologies, Inc. (IDT), Sigma-Aldrich, Life Technologies, or Bio-Synthesis, Inc.
The aptamer may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to SEQ ID NO: 1 and SEQ ID NO: 2, or any one of SEQ ID NOS: 3-102. The aptamer may include a polynucleotide having at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOs: 3-6 (nucleotide sequences T25, T49, T59, or T79 in Table 1). In some embodiments, the aptamer includes SEQ ID NO: 7 (T79vrt7 in Table 2), SEQ ID NO: 8 (nucleotide sequence DTRI-019 in Table 2), or SEQ ID NO: 9 (nucleotide sequence DTRI-021 in Table 2).
The terms “polynucleotide,” “nucleotide sequence,” “polynucleotide sequence,” “nucleic acid” and “nucleic acid sequence” refer to a nucleotide, oligonucleotide, polynucleotide (which terms may be used interchangeably), or any fragment thereof. These phrases may refer to DNA or RNA of genomic, natural, or synthetic origin.
Regarding nucleotide sequences, the terms “sequence identity,” “percent identity,” and “% identity” refer to the percentage of base matches between at least two nucleotide sequences aligned using a standardized algorithm. Such an algorithm may insert, in a standardized and reproducible way, gaps in the sequences being compared in order to optimize alignment between two sequences, and therefore achieve a more meaningful comparison of the two sequences. Sequence identity for a nucleotide sequence may be determined as understood in the art. (See, e.g., U.S. Pat. No. 7,396,664). A suite of commonly used and freely available sequence comparison algorithms is provided by the National Center for Biotechnology Information (NCBI) Basic Local Alignment Search Tool (BLAST), which is available from several sources, including the NCBI, Bethesda, Md., at its website. The BLAST software suite includes various sequence analysis programs including “blastn,” that is used to align a known nucleotide sequence with other polynucleotide sequences from a variety of databases. Also available is a tool called “BLAST 2 Sequences” that is used for direct pairwise comparison of two nucleotide sequences. “BLAST 2 Sequences” can be accessed and used interactively at the NCBI website.
Regarding nucleotide sequences, sequence identity is measured over the length of an entire defined nucleotide sequence, for example, as defined by a particular sequence identified herein. Furthermore, sequence identity, as measured herein, is based on the identity of the nucleotide base in the nucleotide sequence, irrespective of any further modifications to the nucleotide sequence. For example, the nucleotide sequences in the tables described herein may include modifications to the nucleotide sequences such 2′fluoro, 2′O-methyl, and inverted deoxythymidine (idT) modifications. These modifications are not considered in determining sequence identity. Thus if a base, for example, is a 2′fluoro adenine (or 2′O-methyl, etc.), it is understood to be an adenine for purposes of determining sequence identity with another sequence. Likewise, the 3′ idT modifications to the nucleotide sequences in the tables described herein also are not considered in determining sequence identity.
Alternatively, the aptamer may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to a polynucleotide comprising from 5′ to 3′ a first stem forming region comprising or consisting of 2, 3, 4, or 5 nucleotides, a first loop region comprising or consisting of the nucleotide sequence AAC, a second stem forming region comprising or consisting of 3, 4, or 5 nucleotides, a second loop region comprising or consisting of the nucleotide sequence CC, a third stem forming region consisting of 2-8 nucleotides, a third loop region consisting of 1-12 nucleotides or a spacer sequence, a fourth stem forming region consisting of 2-8 nucleotides and capable of forming a stem with the third stem forming region, a fourth loop region comprising or consisting of the nucleotide C, a fifth stem forming region comprising or consisting of 3, 4, or 5 nucleotides and capable of forming a stem with the second stem forming region, a fifth loop region comprising or consisting the nucleotide sequence CAGA, and a sixth stem forming region comprising or consisting of 2, 3, 4, or 5 nucleotides and capable of forming a stem with the first stem forming region. Nonlimiting examples of such aptamers are shown as T25, T49, T59, T59 vrt19, T79, T79 vrt7, or DTRI-019 in
As used herein, a “spacer sequence” may be any chemical spacer that does not interfere with the binding activity of the aptamer. For example, the spacer sequence may include, without limitation, a hexaethylene glycol spacer (see, e.g., DTRI-009), a C3 spacer, spacer 9, or any other suitable stable linker known to those skilled in the art which would facilitate and maintain the proper folding and secondary structure of the aptamer.
Based on the general aptamer structure presented, for example, in
In some embodiments, the aptamer may include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 99%, or 100% sequence identity to a polynucleotide comprising from 5′ to 3′ SEQ ID NO: 1 (CGAAC(U/T)GCCC(U/T)C), a variable nucleotide sequence consisting of 1-18 (or any range therein) nucleotides or a spacer sequence, and SEQ ID NO: 2 (GACGCACAGACG).
As used herein, a “variable nucleotide sequence” may be any of the possible nucleotide sequences for a given length. For example, a “variable nucleotide sequence” consisting of 5 nucleotides may include any of the 45 (or 1,025) possible nucleotide sequences having 5 nucleotides.
In some embodiments, the aptamer may be no more than 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, or 16 nucleotides in length.
In some embodiments, the aptamer may have a dissociation constant (KD) for the human VWF protein that is less than 150, 125, 100, 90, 80, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 2.5, 2, 1, 0.5, or 0.1 nanomolar (nM). The KD of an aptamer may be measured using the methodology used by the inventors in the Examples. For example, binding studies using the double-filter nitrocellulose-filter binding assay with the human VWF protein may be performed.
The aptamers may include a polynucleotide (RNA, DNA, or peptide nucleic acid (PNA)) that is in an unmodified form or may be in a modified form including at least one nucleotide base modification. Nucleotide base modifications of polynucleotides to, for example, protect the polynucleotide from nuclease degradation and/or increase the stability of the polynucleotide are well-known in the art. Common nucleotide base modifications that may be used in accordance with the present invention include, without limitation, deoxyribonucleotides, 2′-O-Methyl bases, 2′-Fluoro bases, 2′ Amino bases, inverted deoxythymidine bases, 5′ modifications, and 3′ modifications.
In some embodiments, the aptamer may include a polynucleotide including a modified form including at least one nucleotide base modification selected from the group consisting of a 2′fluoro modification, a 2′O-methyl modification, a 5′ modification, and a 3′modification.
Typical 5′ modifications may include, without limitation, inverted deoxythymidine bases, addition of a linker sequence such as C6, addition of a cholesterol, addition of a reactive linker sequence which could be conjugated to another moiety such as a PEG. Typical 3′ modifications may include, without limitation, inverted deoxythymidine bases, and inverted abasic residues.
In some embodiments, the aptamer may further include a tail nucleotide sequence at the 5′ end or the 3′ end of the polynucleotide which is not capable of base pairing with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or more consecutive nucleotides in the polynucleotide. The tail nucleotide sequence may consist of 2-20 nucleotides or any range therein. As an exemplary tail nucleotide sequence, the present inventors added a 5-nucleotide Uracil (oligo-U tail) to the 3′-end of an aptamer as a potential artificial nucleation site for antidote binding. Thus, in some embodiments, the tail nucleotide sequence may include the nucleotide sequence (U/T)(U/T)(U/T)(U/T)(U/T). However, it is also contemplated that other nucleotide sequences could serve as tail nucleotide sequences so as that they were not capable of base pairing with 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or more consecutive nucleotides in the polynucleotide of the aptamer. Additionally, tail nucleotide sequences were also added successfully to the 5′ end of the aptamer without significantly affecting the activity of the aptamer.
As additional 5′ and/or 3′ modifications, the aptamer may include a polynucleotide including a 5′ linker and/or a 3′ linker. Common 5′ and/or 3′ linkers for polynucleotides are known in the art and may include peptides, amino acids, nucleic acids, as well as homofunctional linkers or heterofunctional linkers. Particularly useful conjugation reagents that can facilitate formation of a covalent bond with an aptamer may comprise a N-hydroxysuccinimide (NHS) ester and/or a maleimide or using click chemistry. Typical 5′ and/or 3′ linkers for polynucleotides may include without limitation, amino C3, C4, C5, C6, or C12-linkers.
The aptamer may further include a stability agent. As used herein, a “stability agent” refers to any substance(s) that may increase the stability and/or increase the circulation time of a polynucleotide in vivo. Typical stability agents are known in the art and may include, without limitation, polyethylene glycol (PEG), cholesterol, albumin, or Elastin-like polypeptide.
The aptamer and stability agent may be “linked” either covalently or non-covalently. Additionally, the aptamer and stability agent may be linked using the 5′ and/or 3′ linkers described herein. The aptamer and stability agent may be linked at the 5′ end and/or the 3′ end of the aptamer. To link the aptamer and stability agent non-covalently, the aptamer and the stability agent may be linked by a tag system, A “tag system” may include any group of agents capable of binding one another with a high affinity. Several tag systems are well-known in the art and include, without limitation, biotin/avidin, biotin/streptavidin, biotin/NeutrAvidin, or digoxigenin (DIG) systems. In some embodiments, the tag system comprises biotin/avidin or biotin/streptavidin. In such embodiments, the aptamer may be modified at either the 5′ or 3′ end to include biotin while the stability agent may be modified to include streptavidin or avidin. Alternatively, the aptamer may be modified at either the 5′ or 3′ end to include streptavidin or avidin while the stability agent may be modified to include biotin.
Dimers, trimers, and tetramers including any one of the aptamers described herein are also provided. A “dimer” refers to the linking together of two aptamer molecules in order to, for example, to increase the stability and/or increase the circulation time of a polynucleotide in vivo. A “trimer” refers to the linking together of three aptamer molecules in order to, for example, to increase the stability and/or increase the circulation time of a polynucleotide in vivo. A “tetramer” refers to the linking together of four aptamer molecules in order to, for example, to increase the stability and/or increase the circulation time of a polynucleotide in vivo. The aptamer molecules may be linked together covalently, noncovalently, or a combination of both. The aptamer molecules may be linked at their 5′ or 3′ ends. To link the aptamers noncovalently, the aptamers may be linked by a tag system or through a scaffold system.
Antidotes are also provided herein and include a polynucleotide having at least 50%, 60%, 70%, 80%, 85%, 90%, 95%, 98%, 99%, or 100% sequence identity to any one of SEQ ID NOS: 103-180 (the nucleotide sequences in Table 3). Alternatively, the antidote may include a polynucleotide having sequence reverse complementary to and capable of hybridizing to at least 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or more nucleotides of any one of the aptamers described herein.
Pharmaceutical compositions including any of the aptamers or antidotes described herein are provided. The pharmaceutical compositions may include a pharmaceutical carrier, excipient, or diluent (i.e., agents), which are nontoxic to the cell or mammal being exposed thereto at the dosages and concentrations employed. Often a pharmaceutical agent is in an aqueous pH buffered solution. Examples of pharmaceutical carriers include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid; low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, arginine or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming counterions such as sodium; and/or nonionic surfactants such as TWEEN™ brand surfactant, polyethylene glycol (PEG), and PLURONICS™ surfactant. In some embodiments, the pharmaceutical carrier may include a buffer including about 20 mM Hepes, pH 7.4; 150 mM NaCl; 1 mM CaCl2); 1 mM MgCl2; 5 mM KCl.
Methods for preventing blood clot formation in a subject are provided. The methods may include administering to the subject any one of the aptamer compositions described herein in a therapeutically effective amount to prevent blood clot formation in the subject. “Preventing blood clot formation” may include reducing the likelihood of blood clots, reducing the size of blood clots or slowing further progression of blood clotting.
As used herein, the term “subject” refers to both human and non-human animals. The term “non-human animals” of the disclosure includes all vertebrates, e.g., mammals and non-mammals, such as non-human primates, sheep, dog, cat, horse, cow, mice, chickens, amphibians, reptiles, and the like. In some embodiments, the subject is a human patient.
The subject in need of blood clot prevention may need prevention of blood clots associated with, for example without limitation, stroke, cerebrovascular thrombi, deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation, coronary artery thrombus, intra-cardiac thrombi, post-surgical thrombi, cancer-induced thrombosis, cancer-related thrombin expression, infection, disseminated intravascular coagulation (DIC), and arterial thrombosis including cerebral arteries, coronary arteries and peripheral arteries in the head and neck, visceral arteries, arms and legs arteries. In some embodiments, the subject in need of blood clot prevention may suffer from atrial fibrillation, or be at risk of having a Deep Vein Thrombosis, a stroke, a heart attack, or a pulmonary embolism.
A therapeutically effective amount or an effective amount as used herein means the amount of a composition that, when administered to a subject for preventing or treating a blood clot is sufficient to effect a treatment (as defined above). The therapeutically effective amount will vary depending on the formulation or composition, the disease and its severity and the age, weight, physical condition and responsiveness of the subject to be treated.
In addition to disclosing methods of preventing blood clots in a subject, the inventors demonstrate that VWF-targeting agents may be used thrombolytically to reduce or “bust” blood clots that have already formed. In the Examples, the inventors demonstrate that one of the disclosed VWF-targeting aptamers, T79vrt7/DTRI-031, was superior to recombinant tissue plasminogen activator (rTPA) in a murine carotid artery occlusion model. These results surprisingly demonstrate that VWF-targeting agents may also be used to treat formed blood clots (thrombolytic activity) as well as being used to prevent blood clot formation (anti-thrombotic activity).
Based on this new use of VWF-targeting agents, methods for treating a blood clot in a subject are also provided. The methods may include administering to the subject a VWF-targeting agent in a therapeutically effective amount to reduce the blood clot in the subject. “Treating a blood clot” or “reducing a blood clot” refers to reducing the size and/or shape of the blood clot so as to allow blood flow to increase at the clot site.
The subject in need of blood clot treatment may need treatment of blood clots associated with, for example without limitation, stroke, cerebrovascular thrombi, deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation, coronary artery thrombus, intra-cardiac thrombi, post-surgical thrombi, cancer-induced thrombosis, cancer-related thrombin expression, infection, disseminated intravascular coagulation (DIC), and arterial thrombosis including cerebral arteries, coronary arteries and peripheral arteries in the head and neck, visceral arteries, arms and legs arteries. In some embodiments, the subject in need of blood clot treatment suffers from a Deep Vein Thrombosis, a stroke, a heart attack, or a pulmonary embolism.
As used herein, a “VWF-targeting agent” is any agent capable of partially or fully blocking, inhibiting, or neutralizing one or more of the biological activities of a von Willebrand Factor (VWF) protein including, without limitation, a polypeptide, a polynucleotide, or a small molecule. In some embodiments, a VWF-targeting agent may include an agent capable of binding to the A1 domain of a VWF protein and blocking the VWF protein's binding with a gp1b alpha protein. A VWF-targeting agent may function in a direct or indirect manner. For example, the VWF-targeting agent may directly bind to a VWF protein, thus partially or fully blocking, inhibiting or neutralizing one or more biological activities of the VWF protein, in vitro or in vivo. The VWF-targeting agent may also function indirectly by (1) interacting with (e.g., activating, inducing, blocking or inhibiting) another molecule that can bind to VWF or (2) modulating or affecting the expression (i.e, transcription or translation) of a VWF protein in a cell.
VWF proteins may be any of the VWF proteins found in any mammal including, without limitation, humans or domesticated animals such as dogs, cats, horses, cows, pigs, mice, or rats.
The VWF-targeting agent may be a polypeptide including, without limitation, a peptide or an antibody. As used herein, the term “antibody” is used in the broadest sense used in the art to refer to polypeptide affinity agents based on antibodies. For example, the antibody may include a polyclonal antibody, a monoclonal antibody, a single chain antibody, or antibody fragments such as Fab, Fab′, F(ab′)2, Fv fragments, diabodies, linear antibodies, nanobodies, or multispecific antibodies formed from antibody fragments. The antibody may be chimeric, humanized, or fully human. The antibody may be any one of the five known major classes of immunoglobulins including IgA, IgD, IgE, IgG, and IgM. In some embodiments, the VWF-targeting agent may be an anti-VWF antibody that is capable of binding a VWF protein and thereby partially or fully blocking, inhibiting, or neutralizing one or more of the biological activities of the VWF protein. Suitable anti-VWF antibodies include, without limitation, caplacizumab, ALX-0681, or ALX-0081.
Peptides useful as VWF-targeting agents may be identified using techniques well-known in the art such as phage display.
In some embodiments, the VWF-targeting agent may be an aptamer that is capable of binding a VWF protein and thereby partially or fully blocking, inhibiting, or neutralizing one or more of the biological activities of the VWF protein. Suitable VWF aptamers include, without limitation those described in WO/2008/066621 A3 to Sullenger et al. and the aptamers described herein.
The VWF-targeting agent may also be a small molecule. The small molecule may be chemical molecule having a molecular weight below about 2500 Daltons, 2000 Daltons, 1000 Daltons, or 500 Daltons.
The methods of preventing or treating blood clots described herein may further include administering to the subject an antidote in a therapeutically effective amount to neutralize the aptamer or the VWF-targeting agent. “Neutralizing” the aptamer or VWF-targeting agent refers to decreasing either the anti-thrombotic or thrombolytic activity of the aptamer or VWF-targeting agent.
Antidotes that may be used in accordance with the present methods may include sequence-specific antidotes such as the antidotes described herein and those described in WO/2008/066621 A3. The antidotes may also include sequence non-specific antidotes (i.e., cationic polymers) described in, for example, WO/2008/121354.
The compositions (i.e. aptamers, antidotes, and pharmaceutical compositions) described herein may be administered by any means known to those skilled in the art, including, but not limited to, oral, topical, intranasal, intraperitoneal, parenteral, intravenous, intramuscular, subcutaneous, intrathecal, transcutaneous, nasopharyngeal, intra-lesional, intra-tumoral, intradermal, or transmucosal absorption. Thus the compositions may be formulated as an ingestable, injectable, topical or suppository formulation. Administration of the compositions to a subject may exhibit beneficial effects in a dose-dependent manner. Thus, within broad limits, administration of larger quantities of the compositions is expected to achieve increased beneficial biological effects than administration of smaller amount. Moreover, efficacy is also contemplated at dosages below the level at which toxicity is seen.
It will be appreciated that the specific dosage administered in any given case will be adjusted in accordance with the composition(s) being administered, the disease to be treated or inhibited, the condition of the subject, and other relevant medical factors that may modify the activity of the compositions or the response of the subject, as is well known by those skilled in the art. For example, the specific dose for a particular subject depends on age, body weight, general state of health, diet, the timing and mode of administration, the rate of excretion, medicaments used in combination and the severity of the particular disorder to which the therapy is applied. Dosages for a given patient can be determined using conventional considerations, e.g., by customary comparison of the differential activities of the compositions described herein and of a known agent, such as by means of an appropriate conventional pharmacological protocol.
The maximal dosage for a subject is the highest dosage that does not cause undesirable or intolerable side effects. The number of variables in regard to an individual treatment regimen is large, and a considerable range of doses is expected. The route of administration will also impact the dosage requirements. It is anticipated that dosages of the compositions will prevent or treat blot clots by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% or more as compared to no treatment.
The compositions described herein may be administered one time or more than one time to the subject to effectively prevent or treat blood clots. Suitable dosage ranges are of the order of several hundred micrograms effective ingredient with a range from about 0.01 to 10 mg/kg/day, preferably in the range from about 0.1 to 1 mg/kg/day. Precise amounts of effective ingredient required to be administered depend on the judgment of the practitioner and may be peculiar to each subject. It will be apparent to those of skill in the art that the therapeutically effective amount of the compositions described herein will depend, inter alia, upon the administration schedule, the unit dose of drug administered, whether the composition is administered in combination with other therapeutic agents, the status and health of the recipient, and the therapeutic activity of the particular composition.
The present disclosure is not limited to the specific details of construction, arrangement of components, or method steps set forth herein. The compositions and methods disclosed herein are capable of being made, practiced, used, carried out and/or formed in various ways that will be apparent to one of skill in the art in light of the disclosure that follows. The phraseology and terminology used herein is for the purpose of description only and should not be regarded as limiting to the scope of the claims. Ordinal indicators, such as first, second, and third, as used in the description and the claims to refer to various structures or method steps, are not meant to be construed to indicate any specific structures or steps, or any particular order or configuration to such structures or steps. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to facilitate the disclosure and does not imply any limitation on the scope of the disclosure unless otherwise claimed. No language in the specification, and no structures shown in the drawings, should be construed as indicating that any non-claimed element is essential to the practice of the disclosed subject matter. The use herein of the terms “including,” “comprising,” or “having,” and variations thereof, is meant to encompass the elements listed thereafter and equivalents thereof, as well as additional elements. Embodiments recited as “including,” “comprising,” or “having” certain elements are also contemplated as “consisting essentially of” and “consisting of” those certain elements.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. For example, if a concentration range is stated as 1% to 50%, it is intended that values such as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expressly enumerated in this specification. These are only examples of what is specifically intended, and all possible combinations of numerical values between and including the lowest value and the highest value enumerated are to be considered to be expressly stated in this disclosure. Use of the word “about” to describe a particular recited amount or range of amounts is meant to indicate that values very near to the recited amount are included in that amount, such as values that could or naturally would be accounted for due to manufacturing tolerances, instrument and human error in forming measurements, and the like. All percentages referring to amounts are by weight unless indicated otherwise.
No admission is made that any reference, including any non-patent or patent document cited in this specification, constitutes prior art. In particular, it will be understood that, unless otherwise stated, reference to any document herein does not constitute an admission that any of these documents forms part of the common general knowledge in the art in the United States or in any other country. Any discussion of the references states what their authors assert, and the applicant reserves the right to challenge the accuracy and pertinence of any of the documents cited herein. All references cited herein are fully incorporated by reference in their entirety, unless explicitly indicated otherwise. The present disclosure shall control in the event there are any disparities between any definitions and/or description found in the cited references.
Unless otherwise specified or indicated by context, the terms “a”, “an”, and “the” mean “one or more.” For example, “a protein” or “an RNA” should be interpreted to mean “one or more proteins” or “one or more RNAs,” respectively.
The following examples are meant only to be illustrative and are not meant as limitations on the scope of the invention or of the appended claims.
Materials and Methods
RNA Aptamer Preparation and Folding
RNA aptamers were synthesized using conventional oligonucleotide synthetic methods in house. Prior to platelet function analysis (PFA) and in vivo models, RNA-based aptamers may be “folded” in an appropriate physiological buffer, e.g. Platelet Binding Buffer (20 mM Hepes, pH 7.4; 150 mM NaCl; 1 mM CaCl2); 1 mM MgCl2; 5 mM KCl). Aptamer solution is heated to 95° C. for 3 minutes, immediately placed on ice for 3 minutes, and then allowed to come to room temperature over approximately 5 to 10 minutes.
Aptamer Binding Assays
Affinity constants (Kd values) were determined using double-filter nitrocellulose filter binding assays (Rusconi et al. Thromb. Haemost. 84:841-848 (2000)). All binding studies were performed in binding buffer F (20 mM HEPES, pH 7.4, 150 mM NaCl, 2 mM CaCl2), and 0.01% BSA) at 37° C. Human purified VWF (factor VIII free) was purchased from Hematologic Technologies Inc. (Essex Junction, VT) and used in the double-filter nitrocellulose filter binding assay to determine the Kd of the aptamers. Briefly, RNA were end-labeled at the 5′ end with T4 polynucleotide kinase (New England Biolabs, Beverly, MA) and [γ32P] ATP (Amersham Pharmacia Biotech, Piscataway, NJ) (Fitzwater and Polisky, Methods Enzymol. 267:275-301 (1996)). End-labeled RNA was diluted in binding buffer F, heat denatured at 65SC for 5 minutes, and subsequently equilibrated at 37° C. Direct binding was performed by incubating trace 32P-RNA with varying concentrations of VWF protein in binding buffer F at 37° C. for 5 min. The fraction of the nucleic acid-protein complex which bound to the nitrocellulose membrane was quantified with a phosphorimager (Molecular Dynamics, Sunnyvale, CA). Non-specific binding of the radiolabeled nucleic acid was subtracted out of the binding such that only specific binding remained (Wong and Lohman, Proc. Natl. Acad. Sci. USA 90:5428-5432 (1993)).
FeCl3-Induced Arterial Thrombosis
A FeCl3 chemical injury model for inducing arterial thrombosis in the mouse is described. The anesthesia was induced with 4 to 5% isoflurane inhaled in a sealed chamber for 5-7 minutes prior to intubation. After gas induction, a single injection of Avertin/tribromoethanol (1.25%, 12.5 mg/ml) was given IP with 27 g ½″ needle at a dose between 100-250 mg/kg depending on effect. The total volume ranged from 0.15 to 0.50 cc depending on weight (typically 20-25 g mouse). The animal was returned to the induction chamber for 1-2 more minutes prior to attempting intubation. The mouse was moved to a purpose built intubation stand and intubated with a needleless 20 to 22-gauge catheter. Once intubation was confirmed, the ventral neck was shaved and the mouse transferred to a heated surgery table. While in dorsal recumbency the mouse was immediately connected to a Harvard Apparatus rodent ventilator and maintained with a 70% nitrogen:30% oxygen mix at approximately 90-110 breaths per minute and a tidal volume of ˜0.2 ml. Isoflurane was maintained at ˜1-3%. Body temperature was maintained at approximately 37° C. with a Physitemp TCAT-2DF.
After ensuring a surgical plane of anesthesia, a midline cervical incision of the skin was made and the fascia was bluntly dissected to expose the right common carotid artery. After exposure and isolation of the right common carotid artery, the left jugular vein was exposed by blunt dissection and three 7-0 silk ligatures placed. A small incision was made with microsurgical scissors, hemostasis maintained with a single 7-0 silk ligature, and a PE-10 polyethylene catheter, or equivalent, was placed in the vein and secured with the two remaining 7-0 silk ligatures. Once catheter patency was confirmed with 0.9% saline, a continuous rate infusion of 0.9% saline was started with a Harvard Apparatus PHD2000 (or equivalent) infusion pump at a rate between 0.5-3 μL/min and maintained until the end of study. A 0.5-PSB transit-time flow probe (Transonic Systems Inc.) was placed around the carotid artery to measure blood flow. Blood flow and temperature measurements were captured with LabChart Software (ADInstruments) throughout the study. Once a normal blood flow (1.0 to 3.0 mL/min) was maintained for at least 5 minutes, antithrombotic test drug, or control, was administered via the jugular catheter in a volume of 100 to 200 μl with a saline based vehicle and given over one minute of time. Aptamer drug doses ranged from 0.005 to 1.0 mg/kg.
Approximately 5 minutes after drug or antidote administration, one or two small pieces of filter paper (1 mm×2 mm) was saturated with 2.5% to 10% FeCl3. These “patches” were then placed on the ventral+/−dorsal aspect of the exposed carotid artery proximal to the flow probe. They were left in place for 3 minutes. After removal of the patches, the respective region of the artery was lightly rinsed with 0.9% saline. Carotid artery blood transit time was then continually measured until the endpoint of the study. The endpoint of the procedure was defined as no more than 60 minutes beyond the formation of a stable thrombus (ie. ˜0.0 ml/min carotid artery transit time) or no more than 60 minutes beyond the application of the FeCl3 patches. Once the endpoint was reached, isoflurane was increased to 2-4%. Two encircling ligatures of 7-0 silk were then placed on the artery proximal to the site of thrombus formation. The flow probe was removed and the artery was transected between the silk ligatures and at a point approximately 5 to 8 mm distal. The artery section was removed for histopathology. The animals were then euthanized by an overdose of anesthetic gas followed by a secondary physical method.
Saphenous Vein Bleeding Model
A saphenous vein bleeding model for evaluating hemostasis in the mouse is described. Anesthesia was induced with 4 to 5% isoflurane inhaled in a sealed chamber for 2-3 minutes. A single injection of Avertin/tribromoethanol (1.25%, 12.5 mg/mL) was given IP with 27 g ½″ needle at a dose between 100-250 mg/kg depending on effect. The total volume ranged from 0.15 to 0.50 cc depending on weight (typically 20-25 g mouse). The animal was then returned to the induction chamber for 1-2 more minutes prior to intubation. The mouse was then moved to a purpose built intubation stand and intubated with a needleless 20 to 22-gauge catheter. Once intubation was confirmed, the ventral neck and the medial aspect of both pelvic limbs was shaved and the mouse transferred to a heated surgery table. While in dorsal recumbency the mouse was immediately connected to a Harvard Apparatus rodent ventilator and maintained with a 70% nitrogen:30% oxygen mix at approximately 90-110 breaths per minute and a tidal volume of ˜0.2 mL. Isoflurane was maintained at ˜1-3%. Body temperature was maintained at approximately 37° C. with a Physitemp TCAT-2DF and rectal probe.
After ensuring a surgical plane of anesthesia, a midline cervical incision of the skin was made. Surgical exposure of the left jugular vein was accomplished by blunt dissection. Once the jugular vein was isolated, a PE-10 polyethylene catheter, or equivalent, was placed in the vein and secured with two encircling 7-0 silk ligatures. Once catheter patency was confirmed with 0.9% saline, a continuous rate infusion of 0.9% saline was started with a Harvard Apparatus PHD2000 (or equivalent) infusion pump at a rate between 0.5-3 μL/min and maintained until the end of study. After catheter placement was complete, the skin on the medial aspect of the left or right pelvic limb was incised to expose a length of the saphenous vascular bundle (saphenous vein and artery, medial saphenous vein). The bundle was maintained under 1-2 drops of 0.9% saline to prevent drying.
Test drug or control was administered IV via the jugular catheter in a volume of 100 to 200 μL with a saline vehicle and given over one minute of time. Aptamer drug doses ranged from 0.005 to 1.0 mg/kg. Approximately 5 to 120 minutes after the test drug was given, the exposed saphenous vein was transected with a 23-26 g needle followed by a ˜1 to 2 mm longitudinal incision made in the distal portion of the vessel with micro-dissecting scissors. Extravasated blood was gently wicked away with a tapered mini cotton-tipped applicator until hemostasis occurs. The clot on the distal portion of the vessel was then removed with a 23-26 g needle to restart bleeding. Blood was again wicked away until hemostasis re-occurs. Clot disruption was repeated after every incidence of hemostasis for a total time of 15 to 30 minutes after the initial injury. Injury, clot disruption, hemostasis, and temperature measurements were captured with LabChart Software (ADInstruments) throughout the study. Corresponding antidote molecules were then administered IV via the jugular catheter in a volume of 100 to 200 μL after the test drug. RNA-based oligonucleotide antidotes ranged from 0.005 to 100 mg/kg. Approximately 5 minutes after the administration of the antidote, the clot on the distal portion of the vessel was again removed with a 23-26 g needle to restart bleeding. Blood was wicked away until hemostasis re-occurs. Clot disruption was repeated after every incidence of hemostasis for a total time of 15 to 30 minutes. Once the endpoint was reached, ˜0.5 mL of blood was collected via cardiac puncture or withdrawn from the caudal vena cava. The animal was then euthanized by an overdose of anesthetic gas followed by a secondary physical method.
PFA100 Protocol
Platelet Function Analyzer, PFA-100 (Dade Behring, Deerfield, IL) provides a quantitative measure of platelet function in anticoagulated whole blood (Ortel et al, Thromb. Haemost. 84:93-97 (2000)). Briefly, aptamers were diluted in an appropriate buffer (i.e. 150 mM NaCl; 20 nM HEPES pH: 7.4; 5 mM KCl; 1 mM MgCl2 and 1 mM CaCl2, or 150 mM NaCl; 20 mM HEPES pH: 7.4; 2 mM CaCl2; or PBS) and heat denatured. Aptamers were added to fresh whole blood at the final concentration indicated; incubated at RT for 3-5 minutes and then run utilizing a collagen/ADP test cartridge in a PFA-100. The maximum closing time of the PFA-100 is 300 seconds. Antidote activity of aptamer was measured by mixing whole blood with aptamer in buffer followed by administration of antidote and measuring in PFA.
Results
VWF9.14 Variants
To optimize the VWF9.14 aptamer, we generated several VWF9.14 aptamer truncation variants and several VWF9.14 aptamer modification variants. See, e.g.,
The VWF9.14 aptamer modification variants created are listed in Table 2 below.
In addition to creating the VWF9.14 aptamer truncation variants and the VWF9.14 aptamer modification variants, we created several antidote sequences targeting these variants, which are listed in Table 3 below.
Binding Studies
To determine the binding affinity of the VWF9.14 aptamer variants for the VWF protein, we performed binding assays with several of the variants. The binding data is summarized above in Tables 1-2. See also
PFA Analysis of VWF9.14 Aptamer Variants
As shown in
In Vivo Testing of VWF9.14 Aptamer Variants
Several of the VWF9.14 aptamer variants were tested in a murine arterial thrombosis model and a murine saphenous vein bleeding model. See
The VWF9.14T79-VRT7 aptamer was also injected at a dosing of 0.0375 mg/kg into the model prior to FeCl3 injury, which resulted in the vessel remained patent for >60 minutes following removal of the FeCl3 patches. See
In the murine saphenous vein bleeding model, the left jugular vein of a mouse is cannulated and the right medial saphenous vein is exposed prior to injecting the aptamer at the indicated dose. Five minutes after injecting the aptamer the saphenous vein is transected and bleeding is followed for 15 minutes, the antidote is then injected to reverse the effects of the aptamer and bleeding is followed for an additional 20 minutes. The activity of the PEG-VWF9.14T79-VRT7 aptamer could be successfully reversed by injecting the VWF9.14T79-AO2 (AO55) antidote. See
Furthermore, we tested the PEG-VWF9.14T79-VRT7 aptamer, the Cholesterol-VWF9.14T79-VRT7 aptamer, the Elastin-like polypeptide (ELP)-VWF9.14T79-VRT7 aptamer, and the VWF9.14T79-AO2 (AO55) antidote in a combined murine arterial thrombosis and saphenous vein bleeding model. In this model the left jugular vein was cannulated and the right carotid artery was exposed and a transonic flow probe was placed in the animal. Five minutes after placement of the probe the aptamer was injected at the indicated dose. After an additional 5 minutes two 7.5% FeCl3 patches were placed on the right carotid artery for 3 minutes prior to removal. Thirty minutes after removal the saphenous vein was exposed and transected and bleeding monitored for 15 minutes. The antidote was injected and clot formation was observed for an additional 15 minutes. See
The T79VRT7 aptamer and was also tested for thrombolytic activity in a murine carotid artery occlusion model and a murine intracranial hemorrhage model. See
Murine Carotid Artery Occlusion and Thrombolysis Model
We employed a murine carotid artery occlusion model where we intubated adult C57BL/6J mice (Jackson Laboratory, Bar Harbor, ME) (18-24 g) and exposed the left jugular vein. Next, we exposed the right common carotid artery and placed a transonic flow probe (Transonic Systems Incorporated, Ithaca, N.Y.) around the artery. The blood flow was measured for 5 minutes to achieve a stable baseline. We then induced thrombosis by applying 10% ferric chloride-soaked Whatmann paper on the vessel. The time to occlusion was then recorded. Twenty minutes after occlusion, we intravenously inject either saline (negative control), anti-VWF aptamer (VWF9.14T79VRT7) at a dose of 0.5 mg/kg, or recombinant tissue plasminogen activator (rTPA) at a dose of 10 mg/kg. We monitored for reperfusion using the Doppler flow probe and determine the time to re-establish perfusion. We terminated the experiment if no recanalization occurred after 60 minutes. The animals were then sacrificed and the brain and common carotid arteries harvested for analysis.
As shown in
Murine Intracranial Hemorrhage Model
We anesthetized adult C57BL/6J mice (18-24 g) and exposed the left jugular vein and right common carotid artery. We then injected either saline (negative control), anti-VWF aptamer (VWF9.14T79-VRT7) at a dose of 0.5 mg/kg, rTPA at dose of 10 mg/kg or anti-VWF aptamer (0.5 mg/kg) and matched antidote oligonucleotide (VWF9.14T79-AO2, also called AO55) at a dose of 2.5 mg/kg 5 minutes after the aptamer. To induce intracranial hemorrhage, we inserted a silicone-coated 6-0 nylon filament into the carotid artery and advanced it until we punctured the internal carotid artery (ICA) terminus, resulting in subarachnoid hemorrhage (SAH). To evaluate the volume of infarct and hemorrhage, we performed magnetic resonance imaging (MRI) on a 9.4 Tesla MRI (Bruker Biospin, Billerica, MA) 90 minutes after induced intracranial hemorrhage.
Ischemic stroke is a leading cause of death and disability in the western world.1 Approved thrombolytic stroke therapy using recombinant tissue plasminogen activator (rTPA) is limited by several critical factors. First, the significant risk of hemorrhagic conversion resulting from in part, the inability to reverse rTPA activity. Second, the short therapeutic window for rTPA renders more than 90% of stroke patients ineligible for therapy.2, 3 Finally, rTPA only achieves approximately 30% recanalization and re-occlusion commonly occurs after primary thrombolysis, resulting in loss of initial neurological improvement.
von Willebrand factor (VWF) is a glycoprotein involved in the seminal event of platelet plug formation. VWF interacts with glycoprotein Ib alpha-IX-V complex on the platelet surface to induce platelet adhesion to the vessel wall.4 Following this glycoprotein IIb/IIIa (gpIIb/IIIa) becomes activated and binds to fibrinogen resulting in thrombus formation. von Willebrand disease (VWD) can be both a qualitative and quantitative reduction and von Willebrand factor. Type I VWD, the predominant form of VWF disease presents with mild bleeding after dental procedures or during menses and not spontaneous hemorrhage.5 Moreover, VWD Type I patients are protected from cerebrovascular and cardiovascular events.6 VWF therefore represents an attractive target in arterial thrombosis and may be superior to current therapies.
Aptamers are single-stranded oligonucleotides that have potential advantages over other classes of therapeutic agents. They bind to their target with high affinity and specificity.7 They can be chemically modified to customize their bioavailability, chemically synthesized in large scale and most pertinent to our application, can be rapidly reversed.8-11
In this Example, the inventors demonstrate that aptamer 9.14T79vrt7 inhibits platelet adhesion under high shear stress in a dose-dependent manner and prevents platelet aggregation. It prevents thrombus formation in a murine carotid injury model. It also demonstrates superior thrombolytic activity in both a murine and canine models of arterial occlusion compared to rTPA and did so without inducing intracranial hemorrhage or shedding of embolic clot to the brain. Finally, an antidote oligonucleotide designed against 9.14T79vrt7 reverses the antiplatelet activity of the aptamer within 2 minutes both in human blood and a murine model of bleeding.
The studies in this Example suggest that the 9.14T79vrt7 aptamer represents a novel and potentially safer approach to treat ischemic stroke and other acute thrombotic events.
Materials and Methods
Synthesis of Aptamer Truncates, Modifications and Antidote Oligonucleotides (AOs)
Aptamer truncates were either transcribed or synthesized in-house. Briefly, T7 RNA polymerase was used to transcribe RNA aptamer truncates T10, T21, and T22. Aptamer truncates, modifications, and antidotes were synthesized using a MerMade 6/12 Oligonucleotide synthesizer (BioAutomation, Irving, TX). Software predicting RNA secondary structure (Mfold by M. Zuker) was used to predict secondary structure.
RNA Aptamer Preparation and Folding
Prior to platelet function analysis (PFA) and in vivo models, RNA-based aptamers may be “folded” in an appropriate physiological buffer.13 Aptamer solution is heated to 95° C. for 3 minutes, immediately placed on ice for 3 minutes, and then allowed to come to room temperature over approximately 5 to 10 minutes.
Human Whole Blood Studies
Human blood was collected from healthy volunteers by vena puncture after written informed consent. Blood draws were performed in accordance with protocols that have been approved by the Institutional Review Board from both the Durham Veterans Administration Medical Center and Duke University Medical Center.
Platelet Adhesion Analysis
The Venaflux™ microfluidics system (Cellix, Dublin, Ireland) measures platelet adhesion on a collagen surface. Human blood was collected into hirudin tubes from healthy volunteers by vena puncture. An aliquot containing 300 μl of whole blood treated with aptamer or platelet-binding buffer alone was flowed through collagen-coated micro-channels at 60 dynes for 3 minutes. Channels were then rinsed with saline for 3 minutes to wash away RBC and unbound platelets. Venaflux imaging software and Image Pro Plus were used to image bound platelets and calculate covered surface area. Aptamer was incubated at 95° C. for 3 minutes, placed on ice for 3 minutes, then incubated for 10 minutes at room temperature. After cooling, aptamer was kept on ice until use. Total surface area covered by bound platelets in treated blood was expressed as a percentage of total coverage in negative control blood. Statistical significance was determined by analysis of variance; IC50 of the aptamer was calculated using a fitted linear regression curve.
Total Thrombus-Formation Analysis System (T-TAS)
The T-TAS (Zacrox, Fujimori Kogyo Co. Ltd., Tokyo, Japan) was used to assess thrombus formation in both human and canine whole blood.15 Blood was collected in a tube with hirudin in a PL chip that contains 25 capillary channels coated with type 1 collagen. The blood flow across the chip was maintained at a rate of 14 μl/min. Platelet aggregation was measured as a function of the amount of pressure (kPa) needed to maintain the flow rate. A camera was also used to observe platelet activity across the collagen-coated capillary channels.
Murine In Vivo Studies
Investigators that performed surgery or analyzed carotid flow and imaging data were blinded to the treatment groups. All in vivo experiments were approved by the Duke University Institutional Animal Care and Use Committee and The Ohio State University Institutional Animal Care and Use Committee. Moreover, these committees adhere to the NIH Guide for the Care and Use of Laboratory Animals.
Carotid Artery Occlusion and Thrombolysis
Murine carotid artery occlusion studies were performed on male and female 8-week old C57BL/6 mice were obtained from the Jackson Laboratory. Thrombosis/occlusion was achieved using Whatman filter paper soaked in FeCl3. Following 20 minutes of carotid occlusion, treatment was initiated. Male and female 8-week old C57BL/6 mice were obtained from the Jackson Laboratory. Animals were anesthetized with ketamine (55 mg/kg) and xylazine (15 mg/kg). Through a midline ventral incision, the animal was intubated (Harvard Apparatus mouse ventilator, Holliston, Mass.) and the common carotid artery was isolated. Baseline carotid flow was obtained with a Doppler flow probe (Transonic Systems Inc., Ithaca, N.Y.). Whatman filter paper soaked in 10% ferric chloride was placed on the artery for 3 minutes. Following 20 minutes of carotid occlusion, treatment was initiated. Through an intravenous saphenous infusion (Harvard Apparatus PHD 2000 Infusion Pump, Holliston, Mass.), animals were treated with control (platelet-binding buffer), VWF aptamer, TPA, aptamer/antidote, TPA/VWF aptamer or no perfusion. Carotid flow was monitored for an additional 90 minutes to assess reperfusion. Heart rate, EKG (ADInstruments PowerLab 4/35 EKG monitoring system, Sydney, Australia) and blood pressure (Kent Scientific CODA Non-Invasive BP Measurement system, Torrington, Conn.) were monitored throughout the procedure. Histological analysis was performed on the carotid arteries.
Femoral Vein Bleeding
Murine femoral vein bleeding model was performed on male and female 8-week old C57BL/6 mice were obtained from the Jackson Laboratory to assess reversibility of antidote oligonucleotide.16 Animals were anesthetized with isoflurane. The hair on the ventral side of both hind limbs was removed. They were then placed supine on a temperature and ECG monitoring board. Extremities were gently restrained. The skin on the left and right ventral hind limb was incised exposing a length of the saphenous neurovascular bundle; the bundle was covered with normal saline to prevent drying. The left saphenous vein was cannulated for drug administration. To assess hemostasis, the right saphenous vein was transected by piercing it with a 23-G needle followed by a longitudinal incision made in the distal portion of the vessel. Blood was gently wicked away until hemostasis occurred. The clot was then removed to restart bleeding and the blood was again wicked away until hemostasis occurs again. Clot disruption was repeated after every incidence of hemostasis for 30 minutes. Two parameters were measured: 1) the number of times that hemostasis occurs in a 30-minute period, and 2) the time required for each hemostasis.
Canine Carotid Artery Occlusion and Thrombolysis
Canine carotid artery occlusion studies were performed on male and female adult beagles (7-11 kg). Carotid occlusion was induced with FeCl3 and stabilized for 45 minutes before treatment was initiated. Dogs were anesthetized and intubated. Right femoral arterial and venous catheter was obtained. The right carotid artery was exposed, and baseline carotid flow was obtained using a Doppler flow probe. Thrombosis was induced with a 50% ferric chloride patch for 15 minutes, and the clot was stabilized for 45 minutes. Dogs were then intravenously infused with vehicle, 0.9 mg/kg TPA or 0.5 mg/kg VWF aptamer. The aptamer and vehicle were administered as a bolus while the rTPA was administered by standard clinical protocol of 10% bolus followed by the remaining drug infused over 45 minutes. Carotid flow was monitored for 120 minutes. A flow probe distal to the site of thrombosis monitored blood flow transit time throughout the experiment. Carotid angiography demonstrated baseline patency, thrombotic occlusion, and recanalization. Periodic blood draws assessed platelet inhibition (Platelet Function Analyzer-100). At the conclusion of the experiment, the brain and carotid arteries of each animal were collected and embedded for histological analysis.
Statistical Analysis
Values are expressed as mean±SD Statistical analysis was performed using multiple t-tests, chi-square analysis and two-way ANOVA where appropriate.
Results
Optimized VWF Aptamer 9.14T79 Binds and Inhibits VWF Activity In Vitro and Ex Vivo
To create a VWF aptamer that would be amenable for future clinical, we designed and tested a series of VWF aptamer derivatives derived from the 2′Fluoro-pyrimidine modified RNA aptamer VWF9.14.12, 13 See Example 1. This effort resulted in a lead VWF aptamer, T59, which is 30 nucleotides long that retained high affinity binding and inhibitory activity. Next, to improve nuclease resistance and optimize the composition, we systematically substituted 2′ O-methyl and/or 2′ Fluoro moieties into the T25 and T59 aptamer truncates. Almost 90 truncates were synthetized and tested in vitro. The fully optimized aptamer 9.14T79vrt7 is 35-nucleotides and binds to VWF with a dissociation constant (Kd)=11.2 nmol/L, Bmax 56% compared to the 60-mer Kd=18.4 nmol/L, Bmax=51% (See Tables 1 and 2 above and
To evaluate the inhibitory effect of the aptamer on platelet adhesion, human whole blood samples were treated with aptamer starting at 900 nmol/L with 2-fold dilutions to 14 nmol/L and tested by measuring platelet adhesion under high-shear stress. The aptamer prevented platelet adhesion to the collagen surface in a dose-dependent manner (
The aptamer's effect on platelet aggregation was measured ex vivo in a PFA-100 human whole blood assay. The VWF aptamer completely inhibited platelet aggregation in this system at doses over 100 nmol/L, where platelet plug formation and closing time exceeded 300 seconds, representing the upper limit of the assay (
9.14T79 Demonstrates Increased Thrombolysis in a Murine Model of Carotid Occlusion than Recombinant Tissue Plasminogen Activator (rTPA)
A murine model of carotid artery occlusion was next used to evaluate aptamer thrombolytic activity. After 20 minutes of stable carotid artery occlusion, animals received aptamer 9.14T79, saline control or rTPA. The dose of rTPA used in this experiment was 10 mg/kg, 11-fold higher than 0.9 mg/kg (the dose used to treat humans who present with ischemic strokes within 3-4.5 hours of last known well) because this was the dose reported to be effective for recanalization in murine models of arterial thrombosis.17 The aptamer was dosed at 0.5 mg/kg and as shown in
9.14T79vrt7 Demonstrates Dose-Dependent Platelet Inhibition of Canine Whole Blood
In order to evaluate platelet thrombus formation under high shear, and begin to assess the aptamer in a large animal model, we tested the VWF aptamer in a Total Thrombus-formation Analysis System (T-TAS) (Fujimori Kogyo Co., Yokohama, Japan)18. 9.14T79vrt7 inhibited canine platelet aggregation and maintained blood flow pressure at doses between 18.75-100 nmol/L (
9.14T79vrt7 Demonstrates Recanalization in a Canine Model of Carotid Occlusion
A canine model of cerebrovascular thrombotic disease was used to corroborate the murine results in a large, clinically relevant animal. Arterial occlusion established and persistent for 45 minutes before treatment. Animals received an intravenous injection of 0.5 mg/kg of 9.14T79vrt7 as a bolus or 0.9 mg/kg of rTPA by the standard clinical protocol of 10% injection followed by the remaining 90% infused over 45 minutes. The carotid arteries of all 3 dogs that received 9.14T79vrt7 recanalized between 5 and 15 minutes after administration (
To investigate the safety of 9.14T79vrt7, we evaluated bleeding and clotting in the brain of these dogs. 9.14T79vrt7 did not induce intracranial hemorrhage nor did carotid artery recanalization result in cerebral thromboemboli in any of the 3 animals (
An Antidote Oligonucleotide can Rapidly Reverse the Antiplatelet Activity of 9.14T79vrt7 In Vitro and In Vivo
We created an antidote oligonucleotide (AO, also called VWF9.14T79-AO2 or AO55) to reverse 9.14T79vrt7 activity if needed. None of the antidotes initially tested could reverse the 30-nucleotide aptamer T59 likely because they could not access a good nucleation site on the aptamer once it was tightly bound to VWF. Therefore, we added a 5-nucleotide Uracil (oligo-U tail) to the 3′-end of the molecule as an artificial nucleation site and tested a 16-nucleotide antidote complementary to this tail and the 3′ end of the aptamer. The antidote oligonucleotide (AO) reversed the aptamer's antiplatelet activity in vitro within 2 minutes at a ratio as low as of 2:1 over 9.14T79vrt7 (
The ability of the antidote to reverse the antiplatelet aptamer was evaluated in a murine femoral vein bleeding model.16 The control untreated mice group demonstrated 12±3 disruptions, (n=7) which were similar to the saline group of 17±3 disruptions (n=7) (p>0.05). 9.14T79vrt7 administered at a dose of 0.375 mg/kg resulted in no clot disruptions, which was highly significant compared to untreated control and saline treated animals (n=11) (p<0.0001). 9.14T79vrt7 administration followed by antidote oligonucleotide addition demonstrated 16±9 disruptions, which was similar to animals that never received the aptamer (n=7). This data was expressed as a % of normal thrombosis (
Currently, there are no acute treatment options for the vast majority of ischemic stroke patients. rTPA treatment, results in hemorrhage, it time-limited and cannot be reversed. Our research demonstrates that an antidote-controlled VWF inhibitor may provide a robust yet safe treatment option for these patients. 9.14T79vrt7 demonstrated improved binding affinity compared to the full-length aptamer,12 commensurate with the potency of a monoclonal antibody.7, 19 Aptamer 9.14T79vrt7 prevented adhesion of human platelets to a collagen surface (
In vivo, 9.14T79vrt7 maintained arterial patency and maintain a transit time greater than 75% at a dose as low as 0.0188 mg/kg (
At first glance, the idea of a drug that targets an endothelial and platelet factor breaking up a formed arterial thrombus is not intuitive, however, a growing body of literature supports the “disaggregation” activity of VWF inhibitors. An in vitro study, high fluid shear stress and irregular vessel surface showed that VWF collates into thick bundles and meshes that span the vessel lumen, binding platelets together, resulting in arterial occlusion.20 Anti-VWF therapy could therefore have an impact on arterial occlusion. This hypothesis is supported by our observation that even in major arteries in dogs, VWF aptamer 9.14T79vrt7 can engender recanalization of an occluded vessel (
The main class of parenteral anti-platelet agents used clinically is glycoprotein IIb/IIIa (gpIIb/IIIa) inhibitors (Abciximab, Eptifibatide and Tirofiban). These agents significantly improved outcomes in acute coronary syndromes (ACS) and percutaneous coronary interventions (PCI).21 When tested in acute ischemic stroke however, they resulted in significant increase in intracranial hemorrhage without improvement in morbidity or mortality.22 Therefore, we developed an antidote oligonucleotide that can readily reverse VWF aptamer activity in case of hemorrhage. The antidote completely reversed 9.14T7vrt79 activity at a molar ratio of aptamer to antidote as low as 1:2 (
This patent application is a divisional application of U.S. application Ser. No. 16/334,307, filed on Mar. 18, 2019 and issuing as U.S. Pat. No. 10,889,816 on Jan. 12, 2021, which is a national stage filing under 35 U.S.C. 371 of International Patent Application No. PCT/US2017/052063, filed Sep. 18, 2017, which application claims the benefit of priority of U.S. Provisional Patent Application No. 62/395,642, filed Sep. 16, 2016, all of which are incorporated herein by reference in their entirety.
This invention was made with government support by the National Institutes of Health under Award Numbers 1U54HL112307 and 5K12NS080223-3,220901. The government has certain rights in the invention.
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| Number | Date | Country | |
|---|---|---|---|
| 20210222170 A1 | Jul 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62395642 | Sep 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16334307 | US | |
| Child | 17146147 | US |
