WO2005094873A1

WO2005094873A1 - Factor ixa for the treatment of bleeding disorders

Info

Publication number: WO2005094873A1
Application number: PCT/US2005/006527
Authority: WO
Inventors: Shane Donovan; Donald A. Baker
Original assignee: Baxter International Inc.; Baxter Healthcare S.A.
Priority date: 2004-03-19
Filing date: 2005-02-28
Publication date: 2005-10-13
Also published as: CA2557061C; CA2557061A1; JP2007529518A; JP2012126743A; US20050209149A1; US20090069543A1; AU2005228945B2; US7767647B2; DE602005024955D1; US7425539B2; ATE489105T1; AU2005228945A1; HK1102366A1; ES2357132T3; EP1755652B1; JP5037331B2; EP1755652A1

Abstract

The invention provides a method of treating bleeding disorders in a subject by administration of a preparation enriched for Factor IXa. The Factor IXa can be produced by proteolytically activating recombinantly-produced Factor IX. The invention also provides an improved method for producing Factor IXa from a plasma fraction, which method results in a Factor IXa product containing little or no prekallikrein activity, thus reducing the incidence of undesired side effects in a subject.

Description

FACTOR IXA FOR THE TREATMENT OF BLEEDING DISORDERS This application claims priority to US provisional application 60/554,726, filed March 19, 2004.

FIELD OF THE INVENTON

[001] This invention relates to the treatment of blood coagulation pathologies by pharmaceutical preparations containing Factor IXa.

BACKGROUND OF THE INVENTION

[002] Blood coagulation is a complex and dynamic biological process that depends on a series of interdependent biochemical reactions. In each step of the series, an active protease is generated from an inactive precursor. Each newly generated protease, in turn, acts on its substrate, another precursor protease, to generate a cascading reaction. This cascade produces ultimately sufficient active thrombin to generate a stable clot. [003] The terminal portion of this cascade occurs on phospholipid membrane of a platelet. On this surface, Factor IXa (activated by Factor Xla or Vila, illustrated in Figure 1), and in the presence of its co-Factor, Factor VIII, activates Factor X to Factor Xa. Factor Xa activates prothrombin to thrombin, which then activates fibrinogen to form the fibrin clot. Factor VIH's specific role is to enhance Factor IXa's catalysis of Factor X, as Factor IXa alone can only slowly activate Factor X in vitro, (van Dieijen et al, J Biol Chem. 1981 Apr 10;256(7):3433-42). [004] The most common blood coagulation pathology, Hemophilia A, is the X linked hereditary deficiency that leads to reduced levels of circulating Factor VIII in the blood of afflicted individuals. Concentrated Factor VIII preparations are used to treat such individuals to restore their circulating FVIII levels to functional levels. However, in approximately 20% of these patients, inhibitory allo- antibodies are produced against FVIII, abrogating the effectiveness of this treatment. [005] Treatment of patients that have become refractory to replacement FVIII therapy include immune tolerance induction (ITI), replacement therapy with Porcine FVIII, and a variety of preparations that are said to bypass the requirement for FVIII treatment in clotting. These bypassing preparations include recombinant FVIIa, Prothrombin Complexes Concentrates and activated Prothrombin Complex Concentrates (aPCCs). [006] The therapeutically effective substances in aPCCs have been speculated to be various combinations of the following factors: Thrombin, Factor Vila, Factor IXa, Factor Xa, Factor Xla, Factor Xlla, Prothrombin/ Factor Xa complex. However, the precise in vivo mechanism of action for aPCCs is still controversial. SUMMARY OF THE INVENTION

[007] This invention provides a method for treating bleeding disorders in a subject by administering a preparation enriched for Factor IXa. Factor IXa for use in the present invention can be produced by proteolytically activating recombinantly-produced Factor IX. The cDNA coding for Factor IX has been isolated, characterized, and cloned into expression vectors. For example, Choo et al., Nature 299:178-180 (1982); Fair et al., Blood 64:194-204 (1984) and Kurachi et al., Proc. Nat. Acad. Sci. USA 79:6461-6464 (1982). A recombinant Factor IX has been produced by recombinant techniques, as described in U.S. Pat. No. 4,770,999, Kaufmann et al., Sep. 13, 1988, which is hereby incorporated by reference. The invention also provides a method for preparing and isolating Factor IXa from a plasma fraction such as Cohn Fraction IV. 1 paste. It is accomplished by deliberately catalyzing the conversion of Factor IX to Factor IXa and introducing an anion exchange step, as a modification to the existing procedures, (described in U.S. Pat. Nos. 3,560,475 and 4,286,056) to selective purify Factor IXa from the impurities present. This preparation, enriched for Factor IXa, is able to correct the Factor VIM bleeding phenotype of Factor Vlll-deficient mice {fviii -/- mice). Therefore, it has clinical utility in treatment of bleeding disorders associated with Hemophilia. Furthermore, an additional utility of the invention is that it removes prekallikrein (PKA) activity from the starting material of Autoplex-T.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] Figure 1 shows the activation of Factor IX by Factor Xla and Calcium or Factor Vila-tissue factor, which results in cleavage of an Arginine (Arg) Alanine (Ala) bond and the formation of Factor IXα, an inactive intermediate of Factor IXa. Cleavage of a second bond, Arg 180-Valine 181 (Val) results in the formation of Factor IXαβ,.the active form of Factor IX (referred to as Factor IXa) and the release of a peptide fragment of approximately 10kDa. ( Figure modified from Royal A McGraw et al Clinics in Haematology -Vol 14.2 June 1985.) The immunoblot experiments used in subsequent figures employ sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to resolve proteins in specific preparations. As these gels were run under reducing conditions, the disulfide bond holding the heterodimer together is broken and the heavy and light chains of Factor IX resolve as discrete species. For example, in the case of Factor IXαβ, the heavy and light chains will resolve at approximately 30 and 20kDA respectively. In this strategy, concentration of the catalytic enzymes would be significantly lower than Factor IX facilitating their subsequent removal by an additional chromatographic, such as an monoclonal affinity column for Factor IX.

[009] Figure 2A is an immunoblot that measures the amount of activated Factor IX in specific

Autoplex-T preparations using a monoclonal antibody specific to the heavy chain of Factor IX. The indicated amounts of purified activated Factor IXa were loaded on the gel. Five μl of each Autoplex-T preparation was loaded on each lane. Therefore, the approximate concentration of activated Factor IX in 2839B065 and 2839B055 lies somewhere between 20 and 50ng/μl. The Factor Eight Correction Units (FECUs) for each Autoplex-T preparation (Lot numbers. 2839B065, 2839B055, 2839B053) is indicated below the appropriate lane. These results also indicate that the amount of activated Factor IX correlates positively with FECU potency.

[010] Figure 3 is an Immunoblot with a monoclonal antibody specific to the heavy chain of Factor IX using a panel of Autoplex-T manufacturing lots produced in 2002 and 2003 that had above the minimum acceptable potency ( > than 6 FECU units per ml). The Factor Eight Correction Units (FECUs) for each Autoplex-T preparation is indicated below the appropriate lane. In all cases, Factor IX has been activated to Factor IXa.

[011] Figures 4A & B show a dose response of purified activated Factor IX in a FECU clotting assay.

In this experiment, increasing amounts of Factor Xla (0, 10, 20, 30, 50and 75ng per ml) are used to regulate the amount of activated Factor IXa that was subsequently used in a FECU clotting assay. Figure 4A is a coomassie blue stained SDS-PAGE gel showing that at increasing concentrations of

Factor Xla, more activated Factor IX is produced. Purified standards of Factor IXa and Factor IX were resolved on the same gel for comparison.

Figure 4B Each aliquot of the digest was then analyzed by an activated partial thromboplastin time assay of FVIII deficient plasma. The amounts of Factor Xla (0 -75ng/ml) added do not have significant FECU activity in this experiment. These results show that activated Factor IX has Factor

VIII bypassing activity.

[012] Figure 5A is a schematic demonstrating the purification scheme for purifying Factor IXa from Autoplex-T preparations. Figure 5B demonstrates by immunoblot (with a monoclonal antibody specific for the heavy chain of Factor IX) that the concentration of activated Factor IX in the pooled Q-sepharose eluate is similar to an Autoplex-T preparation.

DETAILED DESCRIPTION OF THE INVENTION

[013] The invention provides a method of treating a subject with a bleeding disorder by administering a pharmaceutical preparation containing concentrated FIXa, which does not contain detectable PKA activity. Surprisingly, the FIXa initiates clotting in a subject without endogenous FVIII or with an endogenous form of FVIII that is inactive. [014] To make the Factor IXa concentrate, the starting material can be recombinantly-produced

Factor IX, as provided in US Patent No. 4,770,999, which is herein incorporated by reference. Briefly, recombinant Factor IX at 114μg/ml (2μM) is incubated at 37°C with 2.4μg per ml (30nM) Factor Xla in Tris buffered Saline at 7.4 that contains 5 mM CaCI . This reaction is allowed to digest at 37°C for two hours. Alternatively, recombinant Factor IX at 114μg/ml (2μM) is incubated with both Factor Vila and Tissue Factor at 1μg per ml (20nM) at 37°C in Tris buffered saline that contains 5mM Ca2⁺ and 1mM adapted from Zhong et al, Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):3574-8. Furthermore, in both activation reactions an aliquot is removed, added to an equal volume of 2X reducing SDS-PAGE sample buffer and resolved on 10 % polyacrylamide gels to ensure that Factor IX is converted quantitatively to Factor IXa. The preparation of activated Factor IX is diluted into heparinized citrate saline in individual aliquots that are suitable for administration to a mammalian subject. If desired, the catalysts, Factor Xla or TF/ Factor Vila could be removed by selectively purifying Factor IXa using an anti-FIX:Mg(ll) IgG-Sepharose 4B column (1 mg of IgG/ml of gel) as described in Wojcik et al, Biochem. J. (1997) 323 (629-636). Bound FIXa is eluted from the column by a buffer containing 50 mM Tris EDTA Acetate (pH 7.5), 150 mM NaCI, 10 mM benzamidine and 10 mM EDTA. The eluted Factor IXa is subsequently dialyzed into a buffer containing heparinized citrate saline and aliquoted into concentrations suitable for administration to a mammalian subject.

[015] To make the Factor IXa concentrate, the starting material can also be Cohn plasma fraction IV-1 precipitate. The precipitate is dissolved in saline to a concentration of 10% weight/volume at about 20°C and then partially purified by adsorption onto tribasic calcium phosphate, as described in U.S. Pat. No. 3,560,475.

[016] The tribasic calcium phosphate eluant is further purified and concentrated by polyethylene glycol (PEG) precipitation as discussed in U.S. Pat. No. 3,560,475. The resulting precipitate is dissolved in a 0.2 M sodium citrate solution and adjusted for pH as described in U.S. Pat. No. 4,286,056.

[017] Silica at a concentration of 0.5mg/ml is used to activate Factor XI to Factor Xla. Factor XI is a constituent of Fraction IV.1 pastes. Factor Xla activates Factor IX in the paste to Factor IXa. [018] The bulk solution containing activated Factor IXa is then purified further and concentrated on a Q-sepharose resin. The flow through is discarded and the bound proteins are eluted using a sodium citrate solution with a gradient of increasing NaCI concentration. Appropriate tests of the eluant fractions are then performed. The fractions containing the highest concentration of Factor IXa are pooled. This Q-sepharose fraction is enriched for Factor IXa and devoid of PKA activity. [019] The invention was made after a biochemical characterization of an aPCC, Autoplex-T, revealed that it contains unexpectedly a high concentration of activated Factor IX (20-50μg per ml). Furthermore, the concentration of activated Factor IX correlates with the Factor Eight Correction Unit Activity (FECU) of Autoplex-T (Figure 2). The FECU activity assay measures how quickly an Autoplex preparation clots Factor VIII deficient plasma (described in U.S. Pat. No. 4,286,056). This assay is used to assign the potency of the Autoplex-T product, as it is thought to mimic the clinical utility of Autoplex-T: namely the ability to bypass the requirement for Factor VIII in clotting. [020] Figures 2 and 3 demonstrate that in multiple manufacturing lots of Autoplex-T, Factor IX is activated to Factor IXa. The correlation between the Factor IXa content of Autoplex and FECU activity indicates that Factor IXa could be the active pharmaceutical ingredient of Autoplex. Figure 4 demonstrates that purified Factor IXa corrects the clotting time of Factor VIII deficient plasma in a dose-dependent fashion, consistent with this notion. To evaluate this hypothesis, we prepared a more purified preparation of Factor IXa from Autoplex-T using an anion exchange chromatographic step: Q- purified preparation of Factor IXa from Autoplex-T using an anion exchange chromatographic step: Q- sepharose (Figures 5A and 5B). We then compared the biological efficacy of this preparation using a bleeding study in mice deficient for the fviii -/- gene. The results (Tables 3 and 4) show that the purified Factor IXa preparation is able to rescue the bleeding phenotype of these hemophiliac mice. [021] Autoplex-T contains significant amounts of PreKallikrein Activity, due the presence of JFXIIa, a proteolytic fragment of Factor XII. PKA activity is a labeled undesirable attribute of Autoplex-T, as it is associated with significant clinical symptoms, such as pain and hypotension. An additional utility of the invention is that purification of Factor IXa on the Q-sepharose column substantially removes PKA activity from the preparation (Table 1 ).

[022] The following examples refer to the initial isolation of such a preparation of Factor IXa and the demonstration that it is effective in treating bleeding disorders. Example I

[023] Sufficient amount of Fraction Cohn fraction IV- 1 precipitate was suspended in 0.9% saline to make a 10% solution w/v. manufactured in typical fashion as described in U.S. Pat. Nos. 3,560,475 and 4,286,056. The pH was adjusted to 7.2 with 1 N sodium hydroxide, creating sediment. After centrifugation, calcium phosphate was added to the supernatant. The solution was mixed and centrifuged to recover the calcium phosphate - adsorbed precipitate. The precipitate was resuspended in 0.1 M sodium citrate with a volume equal to 4% of the suspended IV-1 paste volume. The suspension was centrifuged and the supernatant, containing the coagulation Factors, was recovered.

Example

[024] This supernatant was adjusted to with 0.5 g/L silica for the time determined to reach a Factor Xla level of about 0.02 U/ml as measured by the S-2222 peptide based chromogenic assay with an aliquot described above. The activation was terminated by filtration of the mixture through a 1.5 micron filter.

Example I

[025] The product from Example II was purified further by polyethylene glycol (PEG) precipitation. First, the solution was brought to 5% w/v PEG by the addition of PEG solid with an average molecular weight of 4000. The suspension was centrifuged, the pH of the supernatant was adjusted to 5.2 with 1N hydrochloric acid, then brought to a 20% w/v solution of PEG by the addition of additional PEG solid. This suspension was centrifuged, the precipitate dissolved in a 0.02 M sodium citrate solution containing 0.72% sodium chloride and 1.5 units heparin/ml (hereafter referred to as heparinized citrated saline), and the pH adjusted to 7.0. The potency of this material was determined to be 23 FECU units per ml.

[026] In the FECU assay, one unit of FECU is defined as that quantity of activated prothrombin complex diluted 1:20 which, upon addition to an equal volume of Factor VIM deficient or FVIII-inhibitor- containing plasma, will correct the clotting time (ellagic acid - activated partial thromboplastin time) to 35 seconds (normal).

Example IV

[027] A sterile column was packed with Q-Sepharose Fast Flow™ (Amersham Biosciences). The column was equilibrated with sterile heparinized citrated saline, containing 0.025 M NaCI. After application of the product from Example III, the column was washed with the same buffer. Factor IXa was eluted with heparinized citrated saline containing increasing amounts of NaCI from 0.025 to 0.25 M. Samples were taken at intervals during the elution and those with the highest concentration of Factor IXa, as determined by immunoblot were pooled. This pool was then subsequently diluted in heparinized citrated saline, pH 7.0 to control for the increase in concentration during the chromatography. (Small aliquots of the bulk were diluted with heparinized citrated saline and tested for Factor VIM correction activity to determine what dilution would bring the potency levels down to 23 FECU/ml (potency of the starting material). The amount of activated Factor IXa in the preparation was determined by immunoblot (Figure 4b) and shown to be similar to an Autoplex-T preparation.

[028] Kallikrein (plasma kallikrein) is an enzyme that is involved in converting kininogen into kinins, which in turn may promote hypotension and associated undesired symptoms in a patient. Prekallikrein activator (PKA) is an enzyme that converts prekallikrein to kallikrein. The CBER reference used as a standard for the PKA assay lists beta-factor Xlla as a component of PKA (CBER Laboratory of Standards and Testing DMPQ/CBER/FDA Product Informatiom Circular for Reference Prekallikrein Activator (PKA) lot #3, date printed 3./31/99.). Prekallikrein activator (PKA) concentration was measured in Autoplex-T and in the purified FIXa preparation using a chromogenic assay (Tankersley et al; Blood. 62 (2): 448=-456, 1983).

[029] Table 1 shows that the PKA activity is removed from the preparation by introduction of the Q- sepharose step. The PKA activity is presented as a percentage of the Center for Biologies Evaluation and Research Standard (CBER). The results indicate that the majority of the PKA activity in the starting material is not recovered in the Q-sepharose eluate.

Table 1

Example V

[030] The following describes the experimental protocol that evaluates bleeding and clotting in fviii -/ - mice. Aliquots of test samples were frozen to -70 degrees C in heparinized citrate saline, and used upon rapid thawing. Groups of five fviii -/- mice were injected with increasing doses of either Factor IXa or anti-inhibitor coagulant complex, Autoplex-T. The Factor IXa groups were injected with the following doses of activated Factor IX 0.002μg/g, 0.01 μg/g, 0.02 μg/g, 0.13 μg/g, or 0.26 μg/g. The Autoplex-T groups were injected with 0.01 FECU/g, 0.075 FECU/g, or 0.150 FECU/g as a positive control. Five fviii -/- mice were injected with sterile heparinized citrated saline. Following a 30- minute incubation period for all mice, a lateral tail vein bleeding study was performed. Specifically, an incision was made on the lateral tail vein and the amount of blood that was discharged was collected during a thirty-minute period. At the end of this period the wound was cauterized to prevent lethality due to excessive blood loss. In addition, an incision was made to a group of 14 fviii -/- mice without any treatment and the amount of blood that was collected at specific time points was measured.

[031] The evaluation of the hemostatic efficacy of these preparations would be best evaluated by measuring mouse lethality due to bleeding. Methods that measure hemostasis by recording blood loss within in a given time period are beset by a high variation in bleeding rates from mouse to mouse, as the results in Table 3 demonstrate. However, to avoid unnecessary mouse lethality, we designed the assay to look for clear evidence of hemostasis in individual mice treated with these preparations, with the understanding that not every mouse in each treated group would stop bleeding within the thirty minutes time frame that blood loss was recorded.

Table 2

Al FVIII -/- (14 mice)

§1 HCS vehicle (5 mice) initiate tail bleed C_i Autoplex-T (15 mice) Assay by volume of blood lost D) Purified Factor IXa (25 mice) and hemoglobin concentration

Table 2. Experimental protocol for evaluating the ability of a negative control (HCS), Autoplex-T and Purified Factor IXa for correcting the bleeding phenotype of fviii -/- mice. Table 3 Amount of blood volume lost and Hemoglobin concentrations in ft/;/ -/- mice

As can be seen from the results of Table 3, Factor VIII deficient mice bleed when an incision is made in their tails. The amount of blood collected from each mouse is variable and ranges from 65μl to 400μl

Table 4 Results of tail bleeding study

* The mouse was cauterized early due to excessive bleeding

** The volume is below the lower range of blood lost by fviii-/- deficient animals.

[032] In contrast to the hemophiliac mice of Table 3, when a lateral tail vein bleed is performed on wild type mice as shown in Table 4 they are able to form a clot as indicated by the low volume of blood collected (0 to 80μls).

[033] Factor IXa, at three of the lower dosages, was able to correct bleeding phenotype of specific fviii-/- mice. In four out of 15 mice at these three doses, the amount of blood lost was less than the lower range of 65 μls, and consistent with the amount of blood lost measured in the wild type animals (0 to 80μls). These instances provide clear evidence that bleeding has been stopped efficiently by the Factor IXa preparation. Similarly, for three out of 15 mice, Autoplex-T was able to restore hemostasis to wild type levels. The technician who performed the studies also noted that a partial hemostatic plug had formed in those Autoplex and Factor IXa treated mice that did not show evidence of hemostasis by the blood loss assay. Consequently, these results indicate that Factor IXa has similar in vivo efficacy to the commercial product Autoplex-T.

[034] Interestingly, at two of the higher doses of Factor IXa and the highest dose of Autoplex-T, bleeding appeared to increase, consistent with these agents causing Disseminated hitra-Vascular Coagulation (DIC). This is not surprising, as DIC is a well-recognized complication of higher doses of bypassing therapies.

[035] These results provide clear evidence that Factor IXa has biological efficacy in treating bleeding disorders: It reduced bleeding to wild type levels in specific mice and its spectrum of efficacy was comparable to the current commercial bypassing therapy Autoplex-T. Factor IXa is therapeutically active between 0.002 μg and 0.02 μg per g of body weight of treated mice. Based upon these results Factor IXa could be dosed in patients between 2 and 20mg per kg of body weight.

[036] Given the present disclosure, one of skill in the art will naturally think of additional embodiments of the invention, and the following claims are not intended to limit the scope of the invention.

Claims

We claim:

1. A method of treating a subject with a bleeding pathology, said method comprising administering a pharmaceutical preparation containing at least 10% Factor IXa (mg/mg total protein).

2. The method of claim 1 wherein said pharmaceutical preparation is essentially free of prekallikrein activator activity.

3. The method of claim 1 wherein said bleeding pathology is caused by the presence of FVIII inhibitors in the subject's blood.

4. The method of claim 1 wherein said bleeding pathology is caused by the absence of endogenous FVIII activity in the subject's blood.

5. The method of claim 1 wherein said bleeding pathology is caused by the absence of endogenous FIX activity in the subject's blood.

6. The method of claim 1 wherein the Factor IXa is produced by proteolytic activation of recombinantly-produced Factor IX.

7. A method of making a pharmaceutical preparation containing Factor IXa and essentially free of prekallikrein activity, said method comprising; a) dissolving a paste of Cohn fraction IV-1 ; b) adsorbing clotting factors contained in said Cohn fraction IV-1 onto calcium phosphate; c) eluting said clotting factors from said calcium phosphate to form a first eluate; d) applying said first eluate to an anion exchange resin, thereby adsorbing Factor IXa to said resin and allowing impurities having prekallikrein activity to flow through into a discard fraction; and e) eluting and collecting said Factor IXa from said resin.