Specific Plasmin Inactivation by Anticatalytic Antibody (2023)

[0028]This disclosure provides antibodies and other binding molecules directed against unique loop structures in the plasmin protease domain, which act as a highly specific inhibitor of plasmin-mediated fibrinolysis in vitro and surgical bleeding in vivo.

[0029]In embodiments, the invention provides a method of inhibiting plasmin activity in a subject in need thereof comprising administering to the subject an effective amount of a plasmin inhibiting composition comprising a plasmin protease domain-specific monoclonal antibody or functional fragment thereof.

[0030]In embodiments, the invention provides a method of treating hemorrhage in a subject in need thereof comprising administering to the patient an effective amount of a pharmaceutical composition comprising a plasmin protease domain-specific monoclonal antibody or functional fragment thereof and a pharmaceutically acceptable excipient.

[0031]In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof inhibits fibrinolysis. In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof inhibits plasmin cleavage of Factor V protein. In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof inhibits plasmin cleavage of tripeptide paranitroanilide substrate more potently than epsilon amino caproic acid.

[0032]In embodiments, the invention provides the subject is a human. In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof is a non-competitive inhibitor of plasmin activity.

[0033]In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof requires loops four and five of plasmin to mediate binding of the monoclonal antibody to plasmin. In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof requires loop 7 of plasmin to mediate binding of the monoclonal antibody to plasmin.

[0034]In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof does not specifically bind non-plasmin serine-proteases trypsin, thrombin, activated protein C, kallikrein, neutrophil elastase, or a combination thereof.

[0035]In embodiments, the invention provides that the monoclonal antibody of functional fragment thereof comprises light and heavy variable region amino acid sequences at least 80%, 85%, 90%, 95%, 98%, and 100% identical to SEQ ID NOS:15 and 16.

[0036]In embodiments, the invention provides that the monoclonal antibody or functional fragment thereof comprises CDR amino acid sequences at least 80%, 85%, 90%, 95%, 98%, and 100% identical to amino acid sequences of SEQ ID NOS:9-14.

[0037]In embodiments, the invention provides a method of inhibiting plasmin activity or a method of treating hemorrhage in a subject in need thereof a monoclonal antibody or functional fragment thereof comprises amino acid sequences at least 80%, 85%, 90%, 95%, 98%, and 100% identical to amino acid sequences selected from those presented in Tables 1A and 1B, Tables 2A and 2B, and FIGS. 6A-6D.

[0038]The invention provides a pharmaceutical composition for inhibiting plasmin activity or treating hemorrhage comprising a therapeutically effective amount of an antifibrinolytic composition comprising the plasmin-specific monoclonal antibody or functional fragment thereof and a pharmaceutically acceptable carrier. The invention provides an at least partially isolated monoclonal antibody or a functional fragment thereof comprising the features described herein.

[0039]When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0040]It is understood that aspects and embodiments of the invention described herein include “consisting” and/or “consisting essentially of” aspects and embodiments.

[0041]Throughout this disclosure, various aspects of this invention are presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0042]As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term.

[0043]As used herein, “antibody” refers to an intact immunoglobulin (Ig) molecule of any isotype, or an immunologically active fragment thereof that can compete with the intact antibody for specific binding to the target antigen. In some instances, the antibody is an immunological fragment of an intact antibody (e.g., a Fab, a Fab′, a F(ab′)2, or a single-chain Fv fragment scFvs). Antibodies include, but are not limited to, monoclonal antibodies, polyclonal antibodies, bispecific antibodies, minibodies, domain antibodies, synthetic antibodies, chimeric antibodies, humanized antibodies, human antibodies, antibody fusions, and fragments thereof, respectively. An intact antibody will generally comprise at least two full-length heavy chains and two full-length light chains, but in some instances can include fewer chains such as antibodies naturally occurring in camelids which can comprise only heavy chains. Antibodies can be derived solely from a single source, or can be “chimeric,” that is, different portions of the antibody can be derived from two different antibodies. The basic antibody structural unit typically comprises a tetramer. Each such tetramer typically is composed of two identical pairs of polypeptide chains, each pair having one full-length “light” (about 25 kDa) and one full-length “heavy” chain (50-70 kDa). The amino-terminal portion of each chain typically includes a variable region of about 100 to 110 or more amino acids that typically is responsible for antigen recognition. The carboxy-terminal portion of each chain typically defines a constant region that can be responsible for effector function. Human light chains are typically classified as kappa and lambda light chains. Heavy chains are typically classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. Certain classes such as IgG and IgM have subclasses as well (e.g. IgG1, IgG2, IgG3, IgG4, and so forth).

[0044]As used herein, “monoclonal antibody” or “MAb” refers to a population of antibodies that are made by identical immune cells that are all clones of a unique parent cell.

[0045]As used herein, “antigen binding region” refers the part of an antibody molecule that contains the amino acid residues that interact with an antigen and confer on the antibody molecule its specificity and affinity for the antigen. An antigen binding region typically includes one or more “complementary binding regions” (“CDRs”). A “CDR” is an amino acid sequence that contributes to antigen binding specificity and affinity. Certain antigen binding regions also include one or more “framework” regions. “Framework” regions can aid in maintaining the proper conformation of the CDRs to promote binding between the antigen binding region and an antigen. Structurally, framework regions can be located in antibodies between CDRs.

[0046]As used herein, “epitope” refers to a region of an antigen that is bound by an antibody that targets that antigen, and typically includes specific amino acids that directly contact the antibody. Generally, antibodies specific for a particular target antigen will preferentially recognize an epitope on the target antigen in a complex mixture of proteins and/or macromolecules.

[0047]As used herein, “immunological binding,” refers to the non-covalent interactions of the type which occur between an antibody molecule and an antigen for which the antibody is specific. The strength, or affinity, of immunological binding interactions can be expressed in terms of a dissociation constant (Kd) of the interaction, wherein a smaller Kd represents a greater affinity. Immunological binding properties of selected antibodies can be quantified using methods well known in the art. One such method entails measuring the rates of antigen-binding site/antigen complex formation and dissociation wherein those rates depend on the concentrations of the complex partners, the affinity of the interaction, and geometric parameters that equally influence the rate in both directions. Thus, both the “on rate constant” (Kon) and the “off rate constant” (Koff) can be determined by calculation of the concentrations and the actual rates of association and dissociation. The ratio of Koff/Kon enables the cancellation of all parameters not related to affinity, and is equal to the dissociation constant Kd. An antibody of the present disclosure is said to specifically bind its target antigen when the dissociation constant (Kd) is ≤1 μM. An antibody of the present disclosure specifically binds antigen with “high affinity” when the Kd is <5 nM, and with “very high affinity” when the Kd is <0.5 nM.

[0048]Variations in the amino acid sequences of antibodies are contemplated as being encompassed by the present disclosure, providing that the variations in the amino acid sequence maintain at least 75%, more preferably at least 80%, 90%, 95%, and most preferably 99% sequence identity. Certain percentages in between are included, such as 75%, 76%, 77%, 78%, 79% 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99% sequence identity. In particular, conservative amino acid replacements are contemplated. Conservative replacements are those that take place within a family of amino acids that are related in their side chains. Genetically encoded amino acids are generally divided into families: (1) acidic amino acids are aspartate, glutamate; (2) basic amino acids are lysine, arginine, histidine; (3) non-polar amino acids are alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan, and (4) uncharged polar amino acids are glycine, asparagine, glutamine, cysteine, serine, threonine, tyrosine. The hydrophilic amino acids include arginine, asparagine, aspartate, glutamine, glutamate, histidine, lysine, serine, and threonine. The hydrophobic amino acids include alanine, cysteine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan, tyrosine and valine. Other families of amino acids include (i) serine and threonine, which are the aliphatic-hydroxy family; (ii) asparagine and glutamine, which are the amide containing family; (iii) alanine, valine, leucine and isoleucine, which are the aliphatic family; and (iv) phenylalanine, tryptophan, and tyrosine, which are the aromatic family. For example, it is reasonable to expect that an isolated replacement of a leucine with an isoleucine or valine, an aspartate with a glutamate, a threonine with a serine, or a similar replacement of an amino acid with a structurally related amino acid will not have a major effect on the binding or properties of the resulting molecule, especially if the replacement does not involve an amino acid within a framework site. Whether an amino acid change results in a functional antibody can readily be determined by assaying the specific activity of the antibody derivative. Fragments or analogs of antibodies can be readily prepared by those of ordinary skill in the art. Preferred amino- and carboxy-termini of fragments or analogs occur near boundaries of functional domains.

[0049]Preferred amino acid substitutions are those which: (1) reduce susceptibility to proteolysis, (2) reduce susceptibility to oxidation, (3) alter binding affinity for forming protein complexes, (4) alter binding affinities, and (4) confer or modify other physicochemical or functional properties of such antibodies. Antibodies can include various muteins of a sequence other than the naturally-occurring peptide sequence. For example, single or multiple amino acid substitutions (preferably conservative amino acid substitutions) may be made in the naturally-occurring sequence (preferably in the portion of the polypeptide outside the domain(s) forming intermolecular contacts. A conservative amino acid substitution should not substantially change the structural characteristics of the parent sequence (e.g., a replacement amino acid should not tend to break a helix that occurs in the parent sequence, or disrupt other types of secondary structure that characterizes the parent sequence).

[0050]As used herein, “substantially pure” means an object species is the predominant species present (i.e., on a molar basis it is more abundant than any other individual species in the composition), and preferably a substantially purified fraction is a composition wherein the object species comprises at least about 50% (on a molar basis) of all macromolecular species present. Generally, a substantially pure composition will comprise more than about 80% of all macromolecular species present in the composition, more preferably more than about 85%, 90%, 95%, and 99%. Most preferably, the object species is purified to essential homogeneity (contaminant species cannot be detected in the composition by conventional detection methods) wherein the composition consists essentially of a single macromolecular species.

[0051]As used herein, “patient” and “subject” are used interchangeably and include human and veterinary subjects.

[0052]As used herein, “target antigen” refers to a molecule or a portion of a molecule capable of being selectively bound by an antibody. In certain embodiments, a target can have one or more epitopes. In this context, it does not require that the molecule be foreign or that it be capable of inducing an immune response.

[0053]As used herein, “pharmaceutical agent composition” (or agent or drug) refers to a chemical compound, composition, agent or drug capable of inducing a desired therapeutic effect when properly administered to a patient. It does not necessarily require more than one type of ingredient.

[0054]As used herein, “pharmaceutically acceptable carrier” refers to an excipient, diluent, preservative, solubilizer, emulsifier, adjuvant, and/or vehicle with which an active agent is administered. Such carriers may be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents. Antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; and agents for the adjustment of tonicity such as sodium chloride or dextrose may also be a carrier. Methods for producing compositions in combination with carriers are known to those of skill in the art. In some embodiments, the language “pharmaceutically acceptable carrier” is intended to include any and all solvents, dispersion media, coatings, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. The use of such media and agents for pharmaceutically active substances is well known in the art.

[0055]As used herein, “therapeutically effective amount” refers to the amount of an antibody determined to produce a therapeutic response in a patient. Such therapeutically effective amounts are readily ascertained by one of ordinary skill in the art.

[0056]As used herein, “modulator,” refers to a composition that changes or alters the activity or function of a molecule. For example, a modulator can cause an increase or decrease in the magnitude of a certain activity or function of a molecule compared to the magnitude of the activity or function observed in the absence of the modulator. In certain embodiments, a modulator is an inhibitor, which decreases the magnitude of at least one activity or function of a molecule. Certain exemplary activities and functions of a molecule include, but are not limited to, binding affinity, enzymatic activity, and signal transduction.

[0057]As used herein, “treat” and “treatment” include therapeutic treatments, prophylactic treatments, and applications in which one reduces the risk that a subject will develop a disorder or other risk factor. Treatment does not require the complete curing of a disorder and encompasses embodiments in which one reduces symptoms or underlying risk factors.

[0058]As used herein, “prevent” does not require the 100% elimination of the possibility of an event. Rather, it denotes that the likelihood of the occurrence of the event has been reduced in the presence of the compound or method.

EXAMPLES

[0059]In some exemplary embodiments, a monoclonal antibody was generated against unique sequences in the solvent-exposed, surface loops of the plasmin protease domain. This plasmin inhibitor (Pi) was up to seven logs more potent than EACA for neutralizing plasmin cleavage of small molecular substrates and ˜5000-fold more potent for quenching fibrinolysis. When compared to a2-antiplasmin, the most potent covalent inhibitor of plasmin, the Pi was similarly effective for blocking plasmin catalysis of a small molecular substrate and more potent for inhibiting fibrinolysis. This Pi was exquisitely specific by comparison to other inhibitors; it required loops 4 and 5 of human plasmin for binding and it neutralized plasmin activity in human plasma, but not in plasma from nine other species. Enzymatic analysis indicated that the Pi functions as a non-competitive inhibitor. Fab or chimerized Fab fragments of the Pi were equivalently effective for reducing plasmin catalysis and fibrinolysis. In vivo, in a humanized model of fibrinolytic surgical bleeding, the Pi was more effective at reducing bleeding than a clinical dose of EACA. The data shows that the exemplary monoclonal antibody Pi, directed to unique loop sequences in the protease domain, is an exquisitely specific, highly potent, non-competitive plasmin inhibitor, which significantly reduces experimental surgical bleeding in vivo. The improved specificity and potency of this Pi may translate into a more effective approach to serious, life-threatening bleeding. The ultra-potent and specific monoclonal antibody Pi does not significantly cross the blood brain barrier or placenta, and is not excreted by the kidney. By virtue of these properties, this Pi can help remedy the limitations in the current treatment of severe hemorrhage associated with fibrinolysis.

Methods

[0060]Monoclonal antibody generation. Monoclonal antibodies were generated by somatic cell fusion as described using the cells from mice immunized four times over eight months with human plasmin protease domain coupled to aprotinin agarose.19 Direct binding assays were performed to identify mice with the highest titer of antibody binding to the human plasminogen protease domain. Mice were hyper-immunized intraperitoneally with the human plasminogen protease domain (50 ug) pre-activated with urokinase (100 U, 30 min.). After euthanasia, immune splenocytes were fused with SP2/0 cells with polyethylene glycol as described.19 Fused cells were cultured in hypoxanthine aminopterin and thymidine selection medium at 37° C. in 5% CO2 atmosphere. Clones were selected by a radioimmunoassay in which microtiter plate were coated with goat-anti-mouse Fab antibody (5 ug/ml, 25 ul) for 1 hr. Wells were blocked with 1% bovine serum albumin. Hybridoma supernatants were added and plates were incubated for 1 hr at room temperature (RT). After washing, wells were incubated with 125I-human plasmin (50,000 cmp/25 ul) for 1 hr. After washing, bound 125I-human plasmin was detected by gamma scintigraphy. The positive hybridomas were subcloned by limiting dilution and stored in liquid nitrogen.

[0061]Monoclonal antibody purification. Hybridoma supernatant was applied to an anti-mouse IgG agarose column (Immunechem, Canada) with a flow speed at 1 ml/min. The column was washed with PBS pH 7.4. The antibody was eluted with 0.2M glycine, pH 2.9, followed by dialysis in PBS pH 7.4 at 4° C. overnight. The antibody was concentrated with Amicon Ultra-15 centrifugal filters (Millipore, Billerica, Mass.) according to the manufacturer. The protein concentration was determined by BCA method.

[0062]Recombinant proteins. Plasmin protease domain mutants were recombinantly expressed in E. coli as described.(9) The cDNA sequence of the Pi was isolated from hybridoma cells by PCR cloning with redundant primers. A humanized chimeric version of the Pi was expressed in HEK293 cells by transient cell transfection. After 96 hours, the suspension culture was collected. Purified chimeric Pi was purified by HiTrap rProteinG FF and passed through a 0.2 urn filter. It was provided by Translational Sciences (Memphis, Tenn.).

[0063]Saturation binding assay. Saturation binding assays were performed by ELISA in 96-well plates coated with 2 ug/ml of plasmin or plasminogen at room temperature for 1 hour. Wells were washed with PBS-T: (10 mM phosphate buffer pH 7.4, 150 mM NaCl, 0.05% Tween 20) six times. Non-specific protein binding sites were blocked with 1% BSA for 1 hour at room temperature. After washing the plate as above, various concentrations of antibody (0.002 to 100 ug/ml) were added to the plate in duplicate and for 1 hour at room temperature. The plate was washed and horseradish peroxidase (HRP) conjugated goat anti-mouse secondary antibody (1:8000, Santa Cruz, Dallas, Tex.) was added to the plate. After 1 hour incubation at room temperature, the plate was washed and TMB was added. The absorbance was then read at 370 nm.

[0064]Specificity of Pi binding. The binding of the Pi to different serine proteases was assessed by ELISA in 96-well plates coated with human plasminogen, mouse plasminogen, tPA, trypsin or chymotrypsin (10 ug/ml) and blocked with 1% BSA. After incubation and washing, Pi or control monoclonal antibody supernatants (anti-digoxin) were added to the wells for 1 h in triplicate. Then goat anti mouse antibody conjugated with HRP (1:5000, Sc-2005, Santa Cruz) was then added. The plate was washed after incubation for 1 h. TMB was added to the wells and absorbance at 370nm was recorded.

[0065]Plasmin inhibition analysis. Human plasmin (2.8 nM) was mixed with S2251 substrate and Pi (1×10−9 to 3.3×10−8M) or EACA (3.9×10−3 to 0.25x10-1M) or no inhibitor, and the rate of substrate cleavage was monitored by the release of paranitroanilide product at A405 nm for 20 min. The percent residual activity of plasmin as a function of the log concentration of inhibitor was determined.

[0066]The effect of Pi on the velocity of substrate cleavage by human plasmin was examined. Human plasmin (100 nM, Hematologic Technologies, Inc.) was mixed with or without Pi (50 nM) in the presence of the substrate S2251 (0.1 to 4 mM). The initial rate of substrate cleavage (6 min.) was monitored at A405. Data were plotted and analyzed using Michaelis-Menten kinetics by the Graphpad Prism Program.

[0067]The inhibition of human plasmin by a2AP and Pi was compared. Human plasmin (200 nM) was mixed with a2AP (12.5 to 200 nM) or Pi (15.625 to 500 nM) or no inhibitor and the cleavage of S2251 was monitored at A405 in duplicate.

[0068]The effects of mouse or chimeric Fab on plasmin activity were examined. Plasmin (25 nM) was mixed with various concentrations (0-200 nM) of mouse Fab or chimeric Fab (cFab) and S2251 (0.5 mM) in TBS buffer pH 7.4. Plasmin activity was measured by the release of paranitroanilide product at A405 over time.

[0069]Specificity of plasmin inhibition. The effect of the Pi on different animal plasmins was examined after addition of the plasminogen activator urokinase. Various animal plasmas (5ul) were mixed in microtiter plates in the presence of Pi (1 uM, 10 ul) or buffer, S2251 (10 ul, 0.5 mM final), urokinase (100 or 200 U) in a total volume of 100 ul with PBS. The plates were incubated at 37 deg. C. and the rate of plasmin generation was monitored by substrate cleavage at 405 nm for 1 hr.

[0070]Factor V cleavage. Human factor V (2 ug, IHFV, Innovative Research) was mixed with plasmin (0.05 ug) for 1 hr at RT in the presence of EACA (1 mM), Pi (5 ug) or a control monoclonal antibody (digoxin, 5 ug). Samples were then subjected to SDS-PAGE under reducing conditions on 7.5% gels. Protein bands were detected by staining with Coomassie blue dye.

[0071]Fibrinolytic assays in vitro. The effects of EACA vs. Pi on fibrinolysis were examined in duplicate in human plasma clotted with CaC12 (10 mM) and thrombin (1 U/ml) in the presence of trace amounts of 125I fibrinogen for 1 h at 37 deg. C. After washing in 1 ml of TBS pH 7.4, tPA (5 nM) was added in the presence of various amounts of Pi (62.5 to 1000 nM), EACA (0.125 mM to 2mM) or no inhibitor. After 2.5 h the amount of fibrinolysis was determined by measuring the amount of 125I-fibrin dissolved in the supernatant.

[0072]The effects of a2AP and Pi on fibrinolysis were examined in clots were formed as above in the presence of human plasminogen (2 uM) and a2AP (1 uM) or Pi (1 uM) and various amounts of tPA (0-10 nM). Clot dissolution was monitored in duplicate over 2 h in microtiter plate wells at A405 nm. The amount of fibrinolysis was determined by the relative decrease in A405 as described. (26)

[0073]The ability of Pi to inhibit primate clot lysis was also examined in a microtiter plate assay. Human, baboon or African green monkey plasma (5 ul) was added to 96-well plates in the presence of various concentrations of Pi (0-2000 nM), CaCl2 (2 mM), thrombin (0.125 U/ml ) and human fibrinogen (2 mg/ml) and urokinase (10 U). The wells were incubated at 37° C., clot lysis was recorded kinetically for 120 min. and the time required for complete clot lysis was recorded.

[0074]The effects of Pi IgG, Fab or chimeric Fab were also compared in a clot lysis assay in microtiter plates. Human plasma (5 ul) was mixed with Pi (IgG or Fab, 0-400nM), fibrinogen (2 mg/ml), CaC12 (2 mM), thrombin (0.125 U/ml) and urokinase (10 U) in a total volume of 80 ul. Clot dissolution at 37 deg. C. was monitored at 405 nm. The percent clot dissolution at 30 min. was determined as the percent change in peak turbidity from baseline=100%×(peak absorbance−30 min. absorbance)/(peak absorbance−baseline absorbance).

[0075]The comparative effects of Pi, MAb 340 and a control MAb (anti-digoxin) were examined in a clot lysis assay in microtiter plates. Human plasma (50 ul) was mixed with the MAbs (20 ug) in duplicate and then clotted with CaCl2 and thrombin, with or without recombinant (r)-tPA (2 nm). Clot dissolution at 37 deg. C. was monitored at 405 nm for 120 min. The time required to fully dissolve the clots during the 120 min. observation period was recorded. Clots incubated with r-tPA and MAb 340 or the Pi did not significantly dissolve. ***p<0.001 vs. time for clot dissolution in samples with the control MAb or no MAb.

[0076]Fibrinolytic bleeding assays in vivo. Anesthetized mice were treated in a randomized, blinded fashion with saline (Control), Pi (100 nmole/kg) or EACA (510 micromole/kg). Human plasminogen (100 nmole/kg) and plasminogen activator (80,000 IU/kg) were given over 60 min. Tail bleeding started 40 min. after the infusion. Tails were pre-warmed for 5 mins in 3 mL of 37° C. saline as described.(27, 28).

[0077]Statistical analyses. Data are shown as mean±standard error. Saturation binding and velocity vs. substrate curves were analyzed by nonlinear regression using a one-site binding hyperbole and Michaelis-Menten kinetic models with the aid of GraphPad Prism. In vivo bleeding data was analyzed by a non-parametric, Kruskal Wallis one way ANOVA with Dunn's correction. A p<0.05 was considered significant.

Results

[0078]A monoclonal antibody plasmin inhibitor (Pi) directed against specific protease domain loops. A monoclonal antibody plasmin inhibitor (Pi) was generated that bound specifically to the protease domain of plasmin (microplasmin), as indicated by immunoblotting (FIG. 1A). Although the core protease structure is highly conserved among serine proteases, the external loop structures of plasmin (FIG. 1B) differ significantly from other enzymes and have been shown to mediate specific interactions of plasmin with substrate modifiers (such as streptokinase), substrates and inhibitors (FIG. 1B) (9). Binding studies with different plasmin mutants, in which the loop structures of plasmin were altered, showed that the Pi binds to an epitope in the protease domain (FIG. 1B) that requires native loops 4 and 5, but does not require the native sequences of loops 3, 6 or 7 (FIG. 1C). This Pi bound plasminogen with high avidity (Kd3.4±0.8 nM, FIG. 1D) suggesting that it will be fully bound at normal physiologic concentrations of plasminogen.

[0079]The Pi is a potent non-competitive inhibitor of plasmin catalytic function with small substrates. The Pi potently neutralized plasmin-mediated cleavage of a small tripeptide paranitroanilide substrate (S2251) with ˜7 logs greater potency than EACA (FIG. 2B). The Pi reduced the Vmax of plasmin cleavage of S2251, suggesting that it acted largely as a non-competitive inhibitor of plasmin activity (FIG. 2B). When compared to a2-antiplasmin, the most potent, covalent inhibitor of plasmin, the Pi had similar potency for inhibiting plasmin cleavage of S2251 (FIG. 3C). To determine whether the Fc region of the MAb resulted in steric hindrance or affected the inhibitory function of the Pi, the effects of Fab fragments of the Pi, which lacked the Fc domain, were examined. The cDNA sequence for the Pi was obtained by PCR cloning with redundant primers (Table 1). Both the mouse Fab and the chimeric, recombinantly expressed Fab forms of the Pi potently inhibited plasmin activity with the tripeptide substrate (FIG. 2D), indicating that steric effects by the larger IgG molecule did not contribute significantly to blocking plasmin activity.

[0080]Comparative specificity of the Pi. To determine the specificity of the Pi, we examined its binding to other serine proteases. By comparison to a control (anti-digoxin) monoclonal antibody, the Pi showed no specific binding to mouse plasminogen, human tPA, trypsin, chymotrypsin or bovine serum albumin (control) (FIG. 3A). The effects of the Pi on plasmin was studied in several different animal plasmas. The Pi suppressed plasmin in human plasma generated by urokinase, but the Pi did not inhibit plasmin activity in dog, guinea pig, bovine, cat, gerbil, hamster, pig, rabbit or rat plasma (FIG. 3B). Non-human primate plasmin has the greatest homology with human plasmin. The Pi markedly prolonged plasmin-induced fibrinolysis of human clots and also showed dose-related suppression of baboon and African green monkey clots (FIG. 3C). These data show that the Pi specifically inhibits human and non-human primate plasmin and does not affect non-primate plasmins or bind to other serine proteases. FIG. 3D shows comparative clot dissolution by two different anticatalytic antibodies, Pi MAb38 and PiMAb340, which bind to different epitopes of the plasmin protease domain.

[0081]Generation of other Pis directed to the plasmin protease domain. To examine the generalizability of this approach, other monoclonal antibodies specifically generated against the plasmin protease domain were tested. MAb 340, which binds to a different epitope than Pi (i.e., requiring loop 7), also inhibited human clot lysis initiated by r-tPA, whereas as a control (anti-digoxin) MAb did not (FIG. 3D).

[0082]Comparative inhibition of factor V cleavage and fibrinolysis. In vivo, factor V cleavage by plasmin is a hallmark of unregulated blood plasmin levels. In vitro, plasmin readily cleaved factor V to low molecular weight bands (FIG. 4A) in the presence of a control (anti-digoxin antibody). Therapeutic levels of EACA (1 mM) slightly diminished Factor V cleavage (FIG. 4A). However, in the presence of the Pi, Factor V cleavage was attenuated (FIG. 4A). The Pi also significantly suppressed plasmin-mediated fibrinolysis of human fibrin clots in a dose-related fashion (FIG. 4B). EACA also diminished fibrinolysis, but by comparison EACA was approximately 5,000-fold less potent than the Pi (FIG. 4B). When compared to a2-antiplasmin at the same dose, the Pi was 2-3-fold more potent in suppressing the plasmin-mediated dissolution of human fibrin clots induced by increasing doses of tPA (FIG. 4C). The whole IgG, Fab and chimeric Fab forms of the Pi effectively inhibited clot lysis with similar dose-related potency (FIG. 4D), suggesting that there are no steric effects on fibrinolysis related to the IgG molecule.

[0083]Suppression of fibrinolytic bleeding in vivo. The potential utility of the Pi for suppression of fibrinolytic bleeding was examined in vivo in randomized, blinded studies of surgical arterial and venous hemorrhage. Since the Pi specifically binds and inhibits human, but not mouse plasmin, a humanized model was developed in which mice were administered human plasminogen and human tPA.(2728) By comparison to saline (control), a clinical dose of EACA (510 micromole/kg) did not reduce bleeding time or blood loss (FIG. 5 A, B). The Pi (100 nmole/kg) markedly suppressed bleeding time (>80%, p<0.01, FIG. 5A) and blood loss vs. controls (FIG. 5B, >85%, p<0.05) or vs. EACA-treated mice (FIG. 5B, p<0.05).

[0084]The therapeutic value of current plasmin inhibitors for treating fibrinolytic hemorrhage is limited by lack of specificity, low potency and toxicity due to off-target effects. To address these challenges of potency and specificity, an exemplary monoclonal antibody Pi was generated against unique sequences in the surface-exposed loops of the plasmin protease domain, which have been shown to mediate interactions with substrate modifiers, inhibitors and substrates 18By comparison to lysine analogs and to α2-antiplasmin, this Pi showed exquisitely specific, high affinity binding to the protease domain of human plasmin but not to other serine proteases. The Pi acted as a potent, non-competitive inhibitor of plasmin-mediated proteolysis of small molecular substrates (S2251). In fibrinolysis studies, the Pi was ˜7 logs more potent than EACA for inhibiting small substrate cleavage and ˜5000-fold more potent for inhibiting fibrin cleavage. When compared to α2-antiplasmin, the most potent plasmin inhibitor known, the Pi was similarly effective for inhibiting plasmin cleavage of small molecular weight substrates and, it appeared more potent for inhibiting fibrinolytic activity. The Pi potently neutralized plasmin-mediated fibrinolysis in primate, but not other animal plasmas. In vivo, in a model of experimental surgical bleeding, the Pi was a more potent than clinical dose EACA for stopping fibrinolytic bleeding.

[0085]Deduced amino acid sequences of Pi. The cDNAs for Pi were obtained from cloned hybridoma cells. The HC and LC gene were amplified with degenerate mouse IgG primer pairs with the cDNA as the template.

TABLE 1A The sequence of intact LC Pi D I Q M T Q S P S S L S A S L 1 GAC ATC CAG ATG ACA CAG TCT CCA TCC TCA CTG TCT GCA TCT CTG CTG TAG GTC TAC TGT GTC AGA GGT AGG AGT GAC AGA CGT AGA GAC G G K V S I T C K A S Q D I N 46 GGG GGC AAA GTC TCC ATC ACT TGC AAG GCA AGC CAA GAC ATT AAC CCC CCG TTT CAG AGG TAG TGA ACG TTC CGT TCG GTT CTG TAA TTG K Y I S W Y Q H K P G K G P R 91 AAG TAT ATT TCT TGG TAC CAA CAC AAG CCT GGA AAA GGT CCT AGG TTC ATA TAA AGA ACC ATG GTT GTG TTC GGA CCT TTT CCA GGA TCC L L I H Y T S T L Q P G I P S 136 CTG CTC ATA CAT TAC ACA TCT ACA TTA CAG CCA GGC ATC CCA TCA GAC GAG TAT GTA ATG TGT AGA TGT AAT GTC GGT CCG TAG GGT AGT R F S G S G S G R D Y S F S I 181 AGG TTC AGT GGA AGT GGG TCT GGG AGA GAT TAT TCC TTC AGC ATC TCC AAG TCA CCT TCA CCC AGA CCC TCT CTA ATA AGG AAG TCG TAG S N L E P E D I A T Y Y C L Q 226 AGC AAC CTG GAG CCT GAA GAT ATT GCA ACT TAT TAT TGT CTA CAG TCG TTG GAC CTC GGA CTT CTA TAA CGT TGA ATA ATA ACA GAT GTC Y D N L Y T F G G G T K L E I 271 TAT GAT AAT CTG TAC ACG TTC GGA GGG GGG ACC AAG CTG GAA ATA ATA CTA TTA GAC ATG TGC AAG CCT CCC CCC TGG TTC GAC CTT TAT K R A D A A P T V S I F P P S 316 AAA CGG GCA GAT GCT GCA CCA ACT GTA TCC ATC TTC CCA CCA TCC TTT GCC CGT CTA CGA CGT GGT TGA CAT AGG TAG AAG GGT GGT AGG S E Q L T S G G A S V V C F L 361 AGT GAG CAG TTA ACA TCT GGA GGT GCC TCA GTC GTG TGC TTC TTG TCA CTC GTC AAT TGT AGA CCT CCA CGG AGT CAG CAC ACG AAG AAC N N F Y P K D I N V K W K I D 406 AAC AAC TTC TAC CCC AAA GAC ATC AAT GTC AAG TGG AAG ATT GAT TTG TTG AAG ATG GGG TTT CTG TAG TTA CAG TTC ACC TTC TAA CTA G S E R Q N G V L N S W T D Q 451 GGC AGT GAA CGA CAA AAT GGC GTC CTG AAC AGT TGG ACT GAT CAG CCG TCA CTT GCT GTT TTA CCG CAG GAC TTG TCA ACC TGA CTA GTC D S K D S T Y S M S S T L T L 496 GAC AGC AAA GAC AGC ACC TAC AGC ATG AGC AGC ACC CTC ACG TTG CTG TCG TTT CTG TCG TGG ATG TCG TAC TCG TCG TGG GAG TGC AAC T K D E Y E R H N S Y T C E A 541 ACC AAG GAC GAA TAT GAA CGA CAT AAC AGC TAT ACC TGT GAG GCC TGG TTC CTG CTT ATA CTT GCT GTA TTG TCG ATA TGG ACA CTC CGG T H K T S T S P I V K S F N W 586 ACT CAC AAG ACA TCA ACT TCA CCC ATT GTC AAG AGC TTC AAC TGG TGA GTG TTC TGT AGT TGA AGT GGG TAA CAG TTC TCG AAG TTG ACC N E C (SEQ ID NO: 1) 631 AAT GAG TGT (SEQ ID NO: 2) TTA CTC ACA (SEQ ID NO: 3)

TABLE 1B The sequence of intact HC of Pi E V K L L E S G G G L V Q P G 1 GAG GTG AAG CTT CTC GAG TCT GGA GGT GGC CTG GTG CAG CCT GGA CTC CAC TTC GAA GAG CTC AGA CCT CCA CCG GAC CAC GTC GGA CCT G S L K L S C A A S G F D F S 46 GGA TCC CTG AAA CTC TCC TGT GCA GCC TCA GGA TTC GAT TTT AGT CCT AGG GAC TTT GAG AGG ACA CGT CGG AGT CCT AAG CTA AAA TCA R Y W M S W V R Q A P G K G L 91 AGA TAC TGG ATG AGT TGG GTC CGG CAG GCT CCA GGG AAA GGG CTA TCT ATG ACC TAC TCA ACC CAG GCC GTC CGA GGT CCC TTT CCC GAT E W I G E I N P D S S T I N Y 136 GAA TGG ATT GGA GAA ATT AAT CCA GAT AGC AGT ACG ATA AAC TAT CTT ACC TAA CCT CTT TAA TTA GGT CTA TCG TCA TGC TAT TTG ATA T P S L K D K F I I S R D N A 181 ACG CCA TCT CTA AAG GAT AAG TTC ATC ATC TCC AGA GAC AAC GCC TGC GGT AGA GAT TTC CTA TTC AAG TAG TAG AGG TCT CTG TTG CGG K N S L Y L Q M S K V R S E D 226 AAA AAT TCG CTG TAC CTG CAA ATG AGC AAA GTG AGA TCT GAG GAC TTT TTA AGC GAC ATG GAC GTT TAC TCG TTT CAC TCT AGA CTC CTG T A L Y Y C A S Y C G Y S Y D 271 ACA GCC CTT TAT TAC TGT GCA AGT TAC TGC GGT TAT AGC TAC GAT TGT CGG GAA ATA ATG ACA CGT TCA ATG ACG CCA ATA TCG ATG CTA A L D C W G Q G T S V T V S S 316 GCT CTG GAC TGC TGG GGT CAA GGA ACC TCA GTC ACC GTC TCC TCA CGA GAC CTG ACG ACC CCA GTT CCT TGG AGT CAG TGG CAG AGG AGT A K T T P P S V Y P L A P G S 361 GCC AAA ACG ACA CCC CCA TCT GTC TAT CCA CTG GCC CCT GGA TCT CGG TTT TGC TGT GGG GGT AGA CAG ATA GGT GAC CGG GGA CCT AGA A A Q T N S M V T L G C L V K 406 GCT GCC CAA ACT AAC TCC ATG GTG ACC CTG GGA TGC CTG GTC AAG CGA CGG GTT TGA TTG AGG TAC CAC TGG GAC CCT ACG GAC CAG TTC G Y F P E P V T V T W N S G S 451 GGC TAT TTC CCT GAG CCA GTG ACA GTG ACC TGG AAC TCT GGA TCC CCG ATA AAG GGA CTC GGT CAC TGT CAC TGG ACC TTG AGA CCT AGG L S S G V H T F P A V L Q S D 496 CTG TCC AGC GGT GTG CAC ACC TTC CCA GCT GTC CTG CAG TCT GAC GAC AGG TCG CCA CAC GTG TGG AAG GGT CGA CAG GAC GTC AGA CTG L Y T L S S S V T V P S S T W 541 CTC TAC ACT CTG AGC AGC TCA GTG ACT GTC CCC TCC AGC ACC TGG GAG ATG TGA GAC TCG TCG AGT CAC TGA CAG GGG AGG TCG TGG ACC P S E T V T C N V A H P A S S 586 CCC AGC GAG ACC GTC ACC TGC AAC GTT GCC CAC CCG GCC AGC AGC GGG TCG CTC TGG CAG TGG ACG TTG CAA CGG GTG GGC CGG TCG TCG T K V D K K I V P R D C G C K 631 ACC AAG GTG GAC AAG AAA ATT GTG CCC AGG GAT TGT GGT TGT AAG TGG TTC CAC CTG TTC TTT TAA CAC GGG TCC CTA ACA CCA ACA TTC P C I C T V P E V S S V F I F 676 CCT TGC ATA TGT ACA GTC CCA GAA GTA TCA TCT GTC TTC ATC TTC GGA ACG TAT ACA TGT CAG GGT CTT CAT AGT AGA CAG AAG TAG AAG P P K P K D V L T I T L T P K 721 CCC CCA AAG CCC AAG GAT GTG CTC ACC ATT ACT CTG ACT CCT AAG GGG GGT TTC GGG TTC CTA CAC GAG TGG TAA TGA GAC TGA GGA TTC V T C V V V D I S K D D P E V 766 GTC ACG TGT GTT GTG GTA GAC ATC AGC AAG GAT GAT CCC GAG GTC CAG TGC ACA CAA CAC CAT CTG TAG TCG TTC CTA CTA GGG CTC CAG Q F S W F V D D V E V H T A Q 811 CAG TTC AGC TGG TTT GTA GAT GAT GTG GAG GTG CAC ACA GCT CAG GTC AAG TCG ACC AAA CAT CTA CTA CAC CTC CAC GTG TGT CGA GTC T Q P R E E Q F N S T F R S V 856 ACG CAA CCC CGG GAG GAG CAG TTC AAC AGC ACT TTC CGC TCA GTC TGC GTT GGG GCC CTC CTC GTC AAG TTG TCG TGA AAG GCG AGT CAG S E L P I M H Q D W L N G K E 901 AGT GAA CTT CCC ATC ATG CAC CAG GAC TGG CTC AAT GGC AAG GAG TCA CTT GAA GGG TAG TAC GTG GTC CTG ACC GAG TTA CCG TTC CTC F K C R V N S V A F P A P I E 946 TTC AAA TGC AGG GTC AAC AGT GTA GCT TTC CCT GCC CCC ATC GAG AAG TTT ACG TCC CAG TTG TCA CAT CGA AAG GGA CGG GGG TAG CTC K T I S K T K G R P K A P Q V 991 AAA ACC ATC TCC AAA ACC AAA GGC AGA CCG AAG GCT CCA CAG GTG TTT TGG TAG AGG TTT TGG TTT CCG TCT GGC TTC CGA GGT GTC CAC Y T I P P P K E Q M A K D K V 1036 TAC ACC ATT CCA CCT CCC AAG GAG CAG ATG GCC AAG GAT AAA GTC ATG TGG TAA GGT GGA GGG TTC CTC GTC TAC CGG TTC CTA TTT CAG S L T C M I T D F F P E D I T 1081 AGT CTG ACC TGC ATG ATA ACA GAC TTC TTC CCT GAA GAC ATT ACT TCA GAC TGG ACG TAC TAT TGT CTG AAG AAG GGA CTT CTG TAA TGA V E W Q W N G Q P A E N Y K N 1126 GTG GAG TGG CAG TGG AAT GGG CAG CCA GCG GAG AAC TAC AAG AAC CAC CTC ACC GTC ACC TTA CCC GTC GGT CGC CTC TTG ATG TTC TTG T Q P I M D T D G S Y F V Y G 1171 ACT CAG CCC ATC ATG GAC ACA GAT GGC TCT TAC TTC GTC TAC GGC TGA GTC GGG TAG TAC CTG TGT CTA CCG AGA ATG AAG CAG ATG CCG K L N V Q K S N W E A G N T F 1216 AAG CTC AAT GTG CAG AAG AGC AAC TGG GAG GCA GGA AAT ACT TTC TTC GAG TTA CAC GTC TTC TCG TTG ACC CTC CGT CCT TTA TGA AAG T C S V L H E G L H N H H T E 1261 ACC TGC TCT GTG TTA CAT GAG GGC CTG CAC AAC CAC CAT ACT GAG TGG ACG AGA CAC AAT GTA CTC CCG GAC GTG TTG GTG GTA TGA CTC K S L S H S P G K (SEQ ID NO: 4) 1306 AAG AGC CTC TCC CAC TCT CCT GGT AAA (SEQ ID NO: 5) TTC TCG GAG AGG GTG AGA GGA CCA TTT (SEQ ID NO: 6)

TABLE 2A Deduced amino acid sequence of mouse-human chimeric light chain. Bold-variable region, preceded by a heterologous signal peptide; underlined, human kappa constant region. MYRMQLLSCI ALSLALVTNS DIQMTQSPSS LSASLGGKVS TKLEIKRTVA APSVFIFPPS DEQLKSGTAS VVCLLNNFYP REAKVQWKVD NALQSGNSQE SVTEQDSKDS TYSLSSTLTL SKADYEKHKV YACEVTHQGL SSPVTKSFNR GEC (SEQ ID NO: 7)

TABLE 2B Deduced amino acid sequence of mouse-human chimeric heavy chain Fab fragment. Bold- variable region, preceded by a heterologous signal peptide; underlined, human CH1 constant domain. MYRMQLLSCI ALSLALVTNS EVKLLESGGG LVQPGGSLKL GYSYDALDCW GQGTSVTVSS ASTKGPSVFP LAPSSKSTSG GTAALGCLVK DYFPEPVTVS WNSGALTSGV HTFPAVLQSS GLYSLSSVVT VPSSSLGTQT YICNVNHKPS NTKVDKKVEP KSCDKTHTCP PCP (SEQ ID NO: 8)

[0086]FIGS. 6A-6D show Clothia sequence numbering of variable sequences of Pi (FIG. 6A) light chain and (FIG. 6B) heavy chain. The CDR loops and sequences (CDR1, CDR2, and CDR3) are shown in FIG. 6C for the light chain (blue and two shades of green greyscales) CDR1 QDINKY (SEQ ID NO:9); CDR2 YTS (SEQ ID NO:10); CDR3 LQYDNLYT (SEQ ID NO:11). The CDR loops and sequences (CRD1, CDR2, and CDR3) are shown in FIG. 6D for the heavy chain (red, orange and purple greyscales) CDR1 GFDFSRYW (SEQ ID NO:12); CDR2 INPDSSTI (SEQ ID NO:13); CDR3 ASYCGYSYDALDC (SEQ ID NO:14). Produced on IMGT/DomainGapAlign Program version: 4.9.2 (2016-09-26) Ehrenmann F., Kaas Q. and Lefranc M.-P. Nucleic Acids Res., 38, D301-307 (2010). PMID: 19900967. Light chain variable region (SEQ ID NO:15). Heavy chain variable region (SEQ ID NO:16).

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<160> NUMBER OF SEQ ID NOS: 16

<210> SEQ ID NO: 1

<211> LENGTH: 213

<212> TYPE: PRT

<213> ORGANISM: Artificial Sequence

<223> OTHER INFORMATION: Description of Artificial Sequence Synthetic

polypeptide

<400> SEQENCE: 1

Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Leu Gly

1 5 10 15

Gly Lys Val Ser Ile Thr Cys Lys Ala Ser Gln Asp Ile Asn Lys Tyr

20 25 30

Ile Ser Trp Tyr Gln His Lys Pro Gly Lys Gly Pro Arg Leu Leu Ile

35 40 45

His Tyr Thr Ser Thr Leu Gln Pro Gly Ile Pro Ser Arg Phe Ser Gly

50 55 60

Ser Gly Ser Gly Arg Asp Tyr Ser Phe Ser Ile Ser Asn Leu Glu Pro

65 70 75 80

Glu Asp Ile Ala Thr Tyr Tyr Cys Leu Gln Tyr Asp Asn Leu Tyr Thr

85 90 95

Phe Gly Gly Gly Thr Lys Leu Glu Ile Lys Arg Ala Asp Ala Ala Pro

100 105 110

Thr Val Ser Ile Phe Pro Pro Ser Ser Glu Gln Leu Thr Ser Gly Gly

115 120 125

Ala Ser Val Val Cys Phe Leu Asn Asn Phe Tyr Pro Lys Asp Ile Asn

130 135 140

Val Lys Trp Lys Ile Asp Gly Ser Glu Arg Gln Asn Gly Val Leu Asn

145 150 155 160

Ser Trp Thr Asp Gln Asp Ser Lys Asp Ser Thr Tyr Ser Met Ser Ser

165 170 175

Thr Leu Thr Leu Thr Lys Asp Glu Tyr Glu Arg His Asn Ser Tyr Thr

180 185 190

Cys Glu Ala Thr His Lys Thr Ser Thr Ser Pro Ile Val Lys Ser Phe

195 200 205

Asn Trp Asn Glu Cys

210

<210> SEQ ID NO: 2

<211> LENGTH: 639

<212> TYPE: DNA

<213> ORGANISM: Artificial Sequence

<223> OTHER INFORMATION: Description of Artificial Sequence Synthetic

polynucleotide

<221> NAME/KEY: CDS

<222> LOCATION: (1)..(639)

<400> SEQENCE: 2

gac atc cag atg aca cag tct cca tcc tca ctg tct gca tct ctg ggg 48

Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Leu Gly

1 5 10 15

ggc aaa gtc tcc atc act tgc aag gca agc caa gac att aac aag tat 96

Gly Lys Val Ser Ile Thr Cys Lys Ala Ser Gln Asp Ile Asn Lys Tyr

20 25 30

att tct tgg tac caa cac aag cct gga aaa ggt cct agg ctg ctc ata 144

Ile Ser Trp Tyr Gln His Lys Pro Gly Lys Gly Pro Arg Leu Leu Ile

35 40 45

cat tac aca tct aca tta cag cca ggc atc cca tca agg ttc agt gga 192