GLIAL DERIVED NEUROTROPHIC FACTOR AS A NEUROPROTECTIVE AGENT

Abstract: The present invention is directed to the use of glial-derived neurotrophic factor (GDNF) to inhibit or prevent seizure activity. The methods of the present invention are accomplished by administering GDNF to patients having or potentially having a neurodegenerative disorder such as epilepsy. Pharmaceutical compositions containing a therapeutically effective amount of GDNF in a pharmaceutically acceptable carrier are also provided.

Description: Gl ial derived neurotrophi c factor as a neuroprotective agent Field of the Invention The present invention relates to the use of glial-derived neurotrophic facto (GDNF) as a neuroprotective agent, and more particularly as an anti-seizur therapeutic. Background of the Invention Epilepsy is a common neurodegenerative disorder. Children and teens hav the highest incidence of the disorder, with 75% of patients in this age grou developing epilepsy before the age of 20. The disorder is characterized by chroni or recurrent seizures indicative of a central nervous system dysfunction that ma be caused by a variety of different etiologic factors. For example, epilepsy has i part been ascribed to excessive release or impaired uptake of endogenous excitator amino acids, such as glutamate, which can lead to neuronal damage, and necrosi (Sperk, Proα. in Neurobiol.. 42:1-32 (1994); McNamara, J. Neurosci.. 14:3413 1325 (1994)). Seizures can be evoked in normal brain by treatments such as electroshoc (Swinyard et al., J. Pharmac. Exo. Ther.. 140:375-384 (1952)), kindling (Goddar et al., Exo. Neurol.. 25:295 (1969)), or chemical convulsants (Nadler, Life Sci. 24:2031-2042 (1981); Ben-Ari et al., Neurosci.. 6:1361-1391 (1981)). Seizur production via these methods and the subsequent brain damage initiate a comple cascade of regenerative and plastic changes including the expression of immediat early genes and growth factors in the hippocampus and in other brain regions of th adult rat (Sperk, Proo. in Neurobiol.. 42:1-32 (1994)). Changes in the expressio of nerve growth factor (NGF), basic fibroblast growth factor (bFGF) and brai derived neurotrophic factor (BDNF), contribute to plasticity of the injured brain i seizure models according to Gall et al., ol. Brain Res.. 9:113-123 (1991); Ernfor et al., Neuron. 7:165-176 (1991); and Follesa et al., EXD. Neurol.. 127:37-4 (1994). Systemic or intracraniai administration of kainic acid to rats induces syndrome characterized by an acute limbic status epilepticus and subsequen neuronal brain damage similar to that observed in temporal lobe epilepsy in huma Thus, kainic acid is widely used as a tool to study temporal lobe epilepsy experimental animals (Ben-Ari et a/., Neurosci.. 6:1361-1391 (1981); and Nadl Life Sci.. 24:2031-2042 (1981)). The kainate receptor is one of three ionotropic glutamate receptors, the ot two are named for their preferred agonists: NMDA (N-methyl-D-aspartate AMPA (σ-amino-3-hydroxy-5-methyl-4-isoxazole propionate). The kainate and AM receptors are often referred to collectively as non-NMDA receptors. Non-NM receptors pass mainly monovaient cations and mediate fast excitatory synap transmission, and more recently have been shown to play an important role in maintenance of certain plasticity processes (Miller, Neurosci.. 14:477-479 (199 and Muller et al., Science. 242:1694:1697 (1988)). In a recent report, m NA levels for a novel neurotrophic factor, g/ial deri neurotrophic factor (GDNF) were shown to increase in the adult hippocampus af seizures induced by kainic acid (Humpel et al., Neurosci.. 59:791-795 (199 Glial-derived neurotrophic factor, a member of the transforming growth facto (TGF- / 0) superfamily, has been cloned, expressed, and shown to manifest pot trophic activity for embryonic midbrain ventral mesencephafic dopaminergic neur in vitro (Lin et al., Science. 260:1130-1132 (1993); and Lin et al., J. Neuroche 63:758-768 (1994)). Recombinant human GDNF (rhGDNF) has also be demonstrated to induce sprouting of dopaminergic fibers in vivo (Hudson et Soc. Neurosci. Abstr.. 19:652 (1993)), increase dopaminβ turnover in t substantia nigra of rats (Hudson et al., supra.: Miller et al., Soc. Neurosci. Abs 20:535.7 (1994)), protect neurons against 6-OHDA lesions, and augment gro and fiber formation of rat fetal transplants of nigral tissue in oculo (Stromberg et Exo. Neurol.. 124:401-412 (1993)). Furthermore, in situ hybridization analysis h shown expression of GDNF mRNA in embryonic but not in normal adult brai suggesting that rhGDNF may be a target-derived factor during development (Ols et al., Soc. Neurosci. Abstr.. 19:652 (1993); and Stromberg et al., EXP. Neur 124:401-412 (1993)). Epilepsy is often treated with drugs to prevent the occurrence of convulsi seizures. Of the patients who respond to such therapy, about 60% still experien seizures, although less frequently. Of the 40% of the patients who are treatable, many of these patients nevertheless experience severe side effects, for example, fatigue, drowsiness, and impotency that substantially affect a patient's quality of life. Accordingly, a need exists for alternative therapies that are effective and do not elicit such severe side effects. The present invention satisfies this need and provides related advantages as well. Summary of the Invention The present invention is directed to the discovery that GDNF provides neuroprotection against disorders associated with seizures, such as epilepsy. Accordingly, the present invention provides methods for inhibiting seizures by administering GDNF to a patient in need of anti-seizure therapy in an amount sufficient to inhibit or prevent the onset of seizures. Preferably, the GDNF is recombinantly produced and is administered in a pharmaceutically acceptable carrier. Therefore, the present invention further provides pharmaceutical compositions comprising a therapeutically effective amount of GDNF and a pharmaceutically acceptable carrier. grief PesgpPtion of th9 Drawings Figure 1 shows that rhGDNF protects against kainic acid induced neuronal loss. Intraventricle GDNF (0.5, 5 S0μgl2μ\) protects hippocampal CA1 (Figure 1 A), amygdala (Figure 1 B) and thalamic neurons (Figure 1 C) against kainic acid ( 12 mg/kg subcutaneous) induced lesions. Animals received either rhGDNF 0.05, 0.5, 5 or 50 μql*\μ\ (C-F), respectively), inactive GDNF (B) or vehicle (A) 1 hour before Kainic acid administration. Group G represent normal animals that received no manipulations. Compared to the kainic acid/vehicle group, GDNF treated animals significantly increased neuronal survival in all regions examined. Neuron counts are the average _+. S.E.M. of 9-24 determinations. Significance of the difference between vehicle and rhGDNF was P < 0.01 (* • ) and P < 0.05 (*) using the Students t-test. Similarly, there was a significant difference (P < 0.01) between the vehicle (A) and the no treatment (G) groups. Figure 2 shows that rhGDNF protects against kainic acid induce hippocampal CA1 pyramidal cell loss. Coronal sections of the rat CA1 hippocamp region stained with cresyl violet x 25. (Figure 2A): 7 days after kainate aci (12mg/kg s.c.) + vehicle (2 l icv). Note the necrosis of the CA1 pyramidal cell (Figure 2B): Normal rat sacrificed at the same time. (Figure 2C): 7 days after kainat acid (12mg/kg s.c.) + rhGDNF (50 //g/2μl, icv). Note the protection of the CA pyramidal ceils. Figure 3 graphs the effects of & rhGDNF (50//g/2 l icv), vehicle (2 l icv) D kainic acid (12mg/kg s.c.) + rhGDNF [50μql2μ , icv), O kainic acid (12mg/k s.c.) + rhGDNF (O.Sμq/2μ icv) and ■ kainic acid (12mg/kg s.c.) + vehicle (2μ icv), on mediating weight loss. Body weights were measured daily for seven day and values are expressed as body weight change from day zero. Compounds wer administered on day zero. Values are mean ± S.E.M., (n = 7-11). Detailed Description of the Invention The present invention provides methods for inhibiting seizures in a patient b administering a therapeutically effective amount of GDNF, preferably recombinan human GDNF (rhGDNF). In one embodiment of this invention, the preferred GDNF is the naturall occurring human protein. The naturally-occurring human protein is preferred fo human therapy in part because it is believed to pose a lower risk of producin unforeseen and undesirable physiological side effects in patients treated therewith However, to the extent that non-human GDNFs, such as rat GDNF, are substantiall equivalent to human GDNFs and possess equivalent biological activity, they ar considered to be within the scope of this invention as well. For purposes herein, a protein is deemed to be "naturally-occurring " if it o a substantially equivalent protein can be found to exist normally in healthy humans "Naturally-occurring" proteins specifically include forms of proteins found to exis in healthy humans that are partially truncated at the amino or carboxyl terminus o such proteins or that have amino acids that are deamidated or otherwise chemicall modified. "Naturally-occurring" proteins may be obtained by recombinant DN methods as well as by isolation from cells which ordinarily produce them "Naturally-occurring" also encompasses proteins that contain or lack an NH 2 - terminal methionyl group as consequence of expression E. coli. "Substantially equivalent" as used throughout the specification and claims is defined to mean possessing a very high degree of amino acid residue homology ( See g enerall y M. Dayoff, Atlas of Protein Sequence and Structure, vol. 5, p. 124 (1972), National Biochemical Research Foundation, Washington, D.C., specifically incorporated herein by reference) as well as possessing comparable biological activity. Particularly preferred GDNF of the present invention is the naturally-occurring protein that has been isolated from serum free growth conditioned medium of B49 giiobastoma cells as previously been described in PCT publication No. WO 93/061 16, which is specifically incorporated herein by reference. Other preferred forms of GDNF are also described in WO 93/06116. The nucleic acid sequences of the genes encoding human and rat GDNFs and the amino acid sequences of such proteins are also given in the WO 93/06116 application. The present invention encompasses non-glycosylated forms of GDNF as well as truncated forms of the naturally-occurring and recombinant GDNF proteins. Modified forms of GDNF are also encompassed in the use of the present methods. For example, GDNF can be modified by attachment of one or more polyethylene glγcol (PEG), other repeating polymeric moieties, or other side chains attached to the basic polypeptide backbone of GDNF. In a further embodiment, the amino acid sequence of the polypeptide chain can be modified, for example by the substitution, addition or deletion of one or more amino acids as long as the desired anti-convulsant activity of GDNF is not substantially impaired. Accordingly, the term "GDNF" is intended to encompass all forms of GDNF. Methods for producing the various forms of GDNF are also disclosed in the WO 93/06116 application. One disclosed method consists of isolating GDNF from various sources, such as serum free medium of B49 cell. A second disclosed method involves isolating the genes responsible for coding GDNF, cloning the gene in suitable vectors and cell types, and expressing the gene in order to produce the GDNF. The latter method, which is exemplary of recombinant DNA methods in general, is a preferred method of the present invention. Recombinant DNA metho are preferred in part because they are capable of achieving comparatively high amounts of proteins with greater purity. Preferably, the above described GDNF is produced by the aforementione method in "substantially pure" form. By "substantially pure" it is meant that GDN in an unmodified form, has a comparatively high specific activity. It is to recognized, however, that derivatives or modified forms of GDNF may ha different specific activities. Because it is possible that the anti-convulsive activity of GDNF is imparte by one or more discrete and separable portions of the protein, it is also envision that the method of the present invention could be practiced by administering therapeutic composition whose active ingredient consists of that portion (or tho portions) of GDNF which controls (or control) the anti-convulsive function. In a preferred embodiment of the present invention, a pharmaceutic composition comprising GDNF is administered in an effective amount to patients f neuroprotection. For therapeutic applications, GDNF can be formulated in pharmaceuticaily-acceptable carrier to produce pharmaceutical compositions. T term "pharmaceutically acceptable carrier" as used herein means a non-toxi generally inert vehicle for the active agent, which does not adversely affect th agent or the patient to whom the composition is administered. Suitable vehicles carriers can be found in standard pharmaceutical texts, for example, in Remington' Pharmaceutical Sciences. 16th ed.. Mack Publishing Co., Easton, PA (1980 incorporated herein by reference. Such carriers include, for example, aqueo solutions such as bicarbonate buffers, phosphate buffers, Ringer's solution an physiological saline. In addition, the carrier can contain other pharmaceuticail acceptable excipients for modifying or maintaining the pH, osmolarity, viscosit clarity, color, sterility, stability, rate of dissolution, or odor of the formulation. The pharmaceutical compositions can be prepared by methods known in th art, including, by way of an example, the simple mixing of reagents. Those skille in the art will know that the choice of the pharmaceutical carrier and th appropriate preparation of the composition depend on the intended use and mod of administration. In one embodiment, it is envisioned that the carrier and GDNF as the active agent constitute a physiologically-compatible, slow-release formulation. It is possible to control the rate of release of the active agent(s) by proper choice of labile linking groups in the oligonucleot.de, which would be known to those skilled in the art. The primary solvent in such a carrier can be either aqueous or non- aqueous in nature. In addition, the carrier can contain other pharmacologically- acceptable excipients for modifying or maintaining the pH, osmolarity, viscosity, clarity, color, sterility, stability, rate of dissolution, or odor of the formulation. Similarly, the carrier can contain still other pharmacologically-acceptable excipients for modifying or maintaining the stability, rate of dissolution, release, or absorption of the active agents. Such excipients are those substances usually and customarily employed to formulate dosages for parenteral administration in either unit dose or multi-dose form. Once the pharmaceutical composition has been formulated, it can be stored in sterile vials as a solution, suspension, gel, emulsion, solid, or dehydrated or lyophilized powder. Such formulations may be stored either in a ready to use form or requiring reconstitution immediately prior to administration. The preferred storage of such formulations is at temperatures at least as low as 4°C and preferably at -70°C. It is also preferred that such formulations containing the active agents are stored and administered at or near physiological pH. It is presently believed that administration in a formulation at a high pH (i.e. greater than 8) or at a low pH (i.e. less than 5) is undesirable. The manner of administering the pharmaceutical formulations containing the active agents for systemic delivery can be via intracranial, subcutaneous, intramuscular, intravenous, or oral. Preferably the manner of administration of the formulations containing active agents for local delivery is directly into the brain via intracranial ventricular (icv) with the aid of catheters and pumps. For oral administration, the pharmaceutical composition of the present invention is encapsulated. The encapsulated active agents can be formulated with or without pharmaceuticaily-acceptable carriers customarily used in the compounding of solid dosage forms. Preferably, the capsule is designed so that the active portion of the formulation is released at that point in the gastro-intestinal tract when bioavaiiability is maximized and pre-systemic degradation is minimize Additional excipients may be included to facilitate absorption of the active agent Diluents, flavorings, low melting point waxes, vegetable oils, lubricants, suspendin agents, tablet disintegrating agents, and binders may also be employed. Regardless of the manner of administration, the specific dose is calculate according to the approximate body weight of the patient. Other factors i determining the appropriate dosage can include the disease or condition to treated or prevented, route of administration and the age, sex and medical conditio of the patient. In certain embodiments, the dosage and administration is designe to create a preselected concentration range of GDNF in the patient's blood strea Preferably, GDNF is administered in doses between about 0.0005 mg/kg and mg/kg. Further refinement of the calculations necessary to determine th appropriate dosage for treatment involving each of the above mentione formulations is routinely made by those of ordinary skill in the art and is within th ambit of tasks routinely performed by them without undue experimentatio especially in light of the dosage information and assays disclosed herein. The dosages may be ascertained through use of the established assays for determinin dosages utilized in conjunction with appropriate dose-response data. As described above, the dosage sufficient to deliver a "therapeuticall effective amount" of GDNF can be determined by those of ordinary skill in the a without undue experimentation. A "therapeutically effective amount" may b defined as the amount of GDNF sufficient to inhibit or prevent seizures in th patient. It should be noted that the GDNF formulations described herein may be use for veterinary as well as human applications and that the term "patient" should n be construed in a limiting manner. In the case of veterinary applications, th dosage ranges should be the same as specified above. In studies relating to the present invention and described in more detail in th Examples, rhGDNF was shown to prevent kainate induced seizures and th associated neuronal cell loss. This effect was achieved at relatively low doses an in a dose-dependent manner. The pronounced immuπostaining for rhGDNF i hippocampal CA 1 and CA3 regions coincide with those hippocampal regions th are extremely vulnerable to kainic acid induced toxicity as reported by J.V. Nadler, The Hi pp ocamous-New Vistas, p. 463-481 (Alan R. Liss, 1989). The intense immunostaining for rhGDNF by a polyclonal anti-GDNF antibody was achieved bilaterally indicating that this protein can move throughout the ventricular system, which would explain the bilateral preservation of CA1 neurons. The results indicate that rhGDNF may have both anti-seizure and anti- epileptogenic activity as indicated by the inhibition of the tonic-clonic convulsions and wet dog shakes, respectively. The anti-convulsant properties of rhGDNF appear to be more potent than the anti-epileptogenic actions. Epileptogenesis and seizures appear to have different pharmacoiogic profiles. Epileptogenesis can be blocked by NMDA receptor antagonists (Stasheff et al., Science. 245:648-651 (1989)). In contrast, seizures may require a higher concentration of antagonist or may not be blocked at all by NMDA antagonists, yet may be quite sensitive to commonly used anticonvuisant drugs. Epileptogenesis is a relatively permanent change that occurs when neural tissue is transformed from a normal to an epileptic state (Stasheff et al., supra). In these studies, the effects of rhGDNF were not evaluated directly on these permanent changes in the neural tissue; however, wet dog shakes a prelude to such changes were inhibited by rhGDNF. Kainic acid induced seizures produces a consistent pattern of brain damage, once status epilepticus has been reached and maintained beyond a critical time period (Bβn-Ari, Neurosci.. 375-403 (1985); and Tanaka et al., Proo. Neurobiol.. 38:317-334 (1992)). The pattern of brain damage observed in these studies is similar to that previously reported in the literature. The lack of kainic acid induced neuronal loss in hippocampal CA3 region has been observed with peripheral kainate administration (Nadler, The Hippocampus-New Vistas, p.463-481 (Alan R. Liss, 1989). The neuroprotective effects of rhGDNF upon hippocampal, thalamic and amygdaloid neurons is consistent with a reduction in seizure activity by this neurotrophic factor. However, a possible direct effect of rhGDNF on kainic acid induced excitotoxicity cannot be excluded, since other neurotrophic factors, bFGF and NGF, can protect against glutamate induced excitotoxicity as described by Hefti et al., Neurobiol. Aoinα. 10:515-588 (1989); Beriove et al., $oς. Negrosci , Abstr., 17:1267 (1991); Shigeno et al., J. Neurosci.. 11 :2914-2919 (1991); Cheng and Mattsoπ, Neyrao, 7:1031-1041 (1991); Shimohama etal.. Neurosci. Lett.. 164:5 58 (1993); and Mattson and Cheng, Stroke. 24:1-136 - 1-140 (1993). However, it is believed that rhGDNF would unlikely act as an inhibitor glutamate receptor-channel complexes, based on the structural requirements these receptors for activation as described in Dingfedine et al., Neurobioloqy. 14: 96 (1988). It is more likely that rhGDNF would influence down stream events systems that are associated with glutamate receptor activation. Other neurotrophi factors have been shown to affect the following: (a) changes in glutamate recept number or function; (b) induction of protective enzymes either stress proteins enzymes of superoxide metabolism; (c) alterations in ionic baiances-specificafly i intracellular calcium stores or Na*/K* ATPase activity; and (d) indirect mediat effects via glial cells. The possibility that rhGDNF may have general depressant activity on synapti transmission would explain the inhibition of kainic acid induced seizure activit However, preliminary in vitro electrophysiological studies using rat hippocamp slices indicated that rhGDNF at 2//g/ml did not affect evoked potentials recorded i areas CA1 and CA3 using standard extracellular recording techniques. Th amelioration of kainic acid induced seizures may reflect a reduction in th bioavaiiability of kainic acid by rhGDNF. This seems unlikely based on th differential dose response relationships for rhGDNF on reducing wet dog shakes an tonic-clonic seizures. Furthermore, inactive rhGDNF did not inhibit kainic aci induced seizures. The ability of the hippocampus to express GDNF mRNA after kainic aci induced seizures, suggests that the brain may have the capacity to produce GDN under certain stressful conditions. This phemonoma is not unusual because man members of the NGF gene family are upreguiated by excitotoxic lesions and/ seizures. Although not wishing to be bound by any particular theory, it is believe that the local production of GDNF acts as a brake on the seizure/excitotoxic proces thus limiting the potential damage that may occur. Hippocampal neurons expres both ionotropic and metabotropic glutamate receptors and activation of th ionotropic NMDA receptor indirectly by kainate appears to participate in th regulation of GDNF mRNA. This finding is supported by the recent studie demonstrating that the specific NMDA receptor channel blocker MK-801 (Wong et al., Proc. Nat! Acad. Sci. U.S.A.. 83:7104-7108 (1986)) attenuated kainic acid induced GDNF mRNA expression (Humpel., Neurosci.. 59:791-795 (1994)). This reduction in GDNF mRNA expression is consistent with the above belief, since epileptiform activity would be reduced, less excitotoxic damage would occur, in the CA1 hippocampal region and the stimulus for endogenous GDNF production would be reduced. The finding that a single bolus intracerebral ventricular injection of rhGDNF reduces the body weights of rats supports previous studies that central or peripheral administration of neurotrophins induce weight loss (Altar et al., Proc. Natl Acad. Sci. U.S.A.. 89:11347-11351 (1992); Martin-lverson et al., J. Neurosci.. 14:1262-1270 (1994)). Possible mechanisms underlying the decrease in body weight may be related to alterations in central monoamines such as dopamine and 5-HT. Peripheral administration of kainic acid also induced body weight changes. Recently, Hajnal et al., Brain Res. Bull.. 29:209-916 (1992), demonstrated that the microlesions produced by iontophoretically applied kainic acid into the central nucleus of the amygdala caused body weight loss, hypo- or aphagia and hypo- or adipsia in a dose-dependent manner. These studies also suggested that the lasting feeding disturbances produced by kainic acid to the amygdala were not related causally to the pathological EEG activity changes, but were related to impairment of complex regulatory mechanisms involved in feeding behavior. The amygdala is not the only brain region that controls feeding behavior and the excitotoxicty produced by kainate may affect other brain regions that control feeding behavior. The observation that low doses rhGDNF attenuated kainic acid induced weight loss may be consistent with its ability to reduce excitotoxic damage and to prevent disruption of the neural circuity that is involved in feeding behavior. The accentuation of the weight loss by the highest dose of rhGDNF represents more than the sum of the effects of kainic acid and rhGDNF. Thus, synergy between rhGDNF and other endogenous mediators released during brain injury may be involved in mediating the weight loss phenomena. Previous in vitro studies indicated that rhGDNF is a potent neurotrophic facto that enhances survival of midbrain dopaminergic neurons and that these effect appeared relatively specific to this transmitter system (Lin et al., Science 260:1130-1132 (1993)). The present studies indicate that rhGDNF can hav additional actions on other πeurotransmitter systems such as the glutaminergi system. This indication is further supported by the finding that GDNF mRN extends to neuronal populations other than dopamine containing neurons (Schaa et al., Exo. Neurol.. 124:368-371 (1993); Humpel et al., Neurosci.. 59:791-79 (1994). The use of neurotrophic factors as a potential therapy in epilepsy appears t be a novel approach, and these studies is believed to be the first demonstration o the effective blockade of seizure activity by a neurotrophic factor in a model o temporal lobe epilepsy. The following examples are intended to illustrate, but not limit, the presen invention. gXAMPte 1 A. Preparation of Active rhGDNF Mature rhGDNF was expressed in £ coll by the same methods described i McDonald et al., Biochim. Bioohvs. Acta. 1090:70-80 (1991), incorporated herei by reference. Thereafter, rhGDNF was recovered in the form of inclusion bodie which are isolated from cell lysate by centrifugation and solubilized in 4 guanidine, 90 mM cysteine, 20 mM Tris, pH 8.5. The protein was renatured to th active species by 10X dilution with 0.2 M guanidine, 2 M urea, 20 M Tris, p 8.75. The refold mixture was held at 4 °C for 2 days before being loaded onto an SP Sepharose Big Bead column (Pharmacia) equilibrated in 20 mM sodium acetate, 300 mM sodium chloride pH 5. Recombinant human GDNF was eiuted from th column using a salt gradient from 0.3 M to 0.6 M sodium chloride. Those fractions containing rhGDNF were combined and diluted with an equal volume of 5 M sodium chloride, 20 mM sodium citrate before being loaded onto a Phenyl-Sepharos column (High Capacity, Pharmacia), equilibrated in 2.5 M sodium chloride, 20 mM sodium citrate, pH 5. The rhGDNF was eiuted from high capacity column with descending salt gradient from 2.5 M to 0 M sodium chloride. The appropriate fractions are pooled and diluted with an equal volume of 20 mM sodium acetate. The diluted protein mixture was next applied to an SP Sepharose High Performance column (Pharmacia) equilibrated in 20 mM sodium acetate, 475 mM sodium chloride, pH 5. The rhGDNF was eiuted from the column with a salt gradient from 475 mM to 675 mM sodium chloride. Fractions containing the purified rhGDNF were combined, concentrated, and stored at -20 °C. B. Preparation of inactive rhGDNF Recombinant human GDNF was chemically inactivated by blocking the protein's carboxylic acid groups with excess glycine methyl ester via carbodiimide coupling. 100mgs of purified rhGDNF was diafiltered into 0.5 M MES pH 5 at a final protein concentration of 1mg/mL. EDC and glycine methyl ester were added to 80 and 800 mM, respectively. The reaction was allowed to sit at room temperature for 1 hour. The mixture was dialyzed against phosphate buffered saline to remove excess reagents before being stored at -20 °C. EXAMPLE 2 Surgery Adult male F344 rats (Harlen) weighing 200-225g were used. The animals were maintained at a constant temperature (22 °C) and 12 hour light and dark cycle. They were allowed free access to food and water. Animals were anesthetized with 2.5% isoflurane + O 2 and positioned in a Kopf stereotaxic frame under continued anesthesia. These animals received a unilateral injection of either rhGDNF (50, 5, 0.5, 0.05μgI2≠\, vehicle (Phosphate Buffered Saline; 2 l) or inactive GDNF (2μ l2μ\) over a 5 minute period into the lateral ventricle (icv) using a 26 gauge Hamilton syringe. The Hamilton syringe was left in place for a further 5 minutes before removal, injection coordinates relative to bregma were: AP -0.8, ML -1.5, at a depth of 3.5mm from dura. Animals had their skin sutured with wound clips and were allowed to recover. Either rhGDNF, inactive GDNF or vehicle were given 1hr before kainic acid. Kainic acid (Tocris Neuramin, England.,) Twelve mg/kg was dissolved in 0.9% saline and was administered subcutaneously. Ani weights were recorded daily for the duration of the study. EXAMPLE 3 Brain Histology Seven days after KA administration, the rats were anesthetized with sodi pentobarbitone 55mg/kg (i.p.) and transcardially perfused with phosphate buffer formalin solution. The brains were removed and immersion-fixed for at least 24 in the same fixative. The brains were then dehydrated, embedded in paraffin w and cut coronally in 5-//m-thick slices and sections were Nissl stained. Using a Lei microscope, viable cell counts were performed bilaterally in the CA1 and C regions of the hippocampus, thalamus (parafascicular thalamic and periventricul thalamic nuclei) and amdydala (amygdafohippocampal area, anterolater basomedial amygdaloid nucleus, posterior; basolateral amygdaloid nucleus, posteri and postermedial cortical amygdaloid nucleus). Counts, lengths and areas we performed at Bregma -4.16 mm (Paxinos and Watson). The total linear length the hippocampal CA1 sector was measured by means of the Image- (Univer Imaging Corp., West Chester, PA) image analysis system. The area of the thalam and amygdaloid areas were measured by means of a 100 mm 2 eye piece graticu corresponding to 0.25mm 2 on a linear calibrated scale using a 20x objective. C counts were expressed as cells/mm for the hippocampal region and cells/mm 2 f the thalamus and amdydala. EXAMPLE 4 Distribution of rhGDNF Twenty-four hours after intracranial ventricular (icv) injection of rhGD C\00μgl4μi), the rats were perfused with 10% neutral buffered formalin, brai removed, paraffin embedded and sectioned at 5 microns onto charged slide Sections were immunostained for GDNF using an affinity-purified rabbit antibo to rhGDNF. The antibody (0.59 mg/ml) was used at a 1 : 100 dilution and incubat with the sections for 1 hour prior to applying monovalent biotiπylated anti-rab and subsequently, Omnitags Streptavidin Alkaline Phosphatase (Lipshaw Immuno Pittsburgh, PA). The sections were developed using the New Fuchsin Substrate System (Dako Corp., Carpinteria, CA). Negative controls included, sections in which irrelevant antibody at similar concentrations was substituted for the primary antibody and sections from phosphate buffered saline injected rats. Slides were mounted with Crystal Mount (Biomeda, Foster City, CA) and later, Permount (Fischer Scientific, Fairlawn, NJ) to create a permanent preparation. Distribution of rhGDNF was evaluated using a Leitz microscope equipped with an ocular micrometer. EXAMPLE 5 Bioassay Bioassay for rhGDNF and inactive GDNF activity was performed as described by Lin et al., J. Biol. Chem.. 265:8942-8947 (1990), incorporated herein by reference. Briefly, the in vitro assay for GDNF activity measures the survival of chick embryo sympathetic chain (E9) neurons. Two thousand purified neurons were placed into each well of a 96-well dish and serial dilutions of GDNF samples were added. After 44 hours, neuronal survival was estimated by the ability of live ceils to reduce the vital dye MTT (3-4_,5-dimethγlthiazol-2-yl]-2,5-diphenyltetrazolium) (Sigma Chemical Co., St. Louis, MO). The bioactivity of rhGDNF was expressed as an EC S0 value, a dilution of rhGDNF that gave 50% of the maximal neuronal survival based on the MTT assay. EXAMPLE 6 Statistics Histological comparisons between control and GDNF treated animals were analyzed using students t-test. Logistic regression was performed to test for a dose- response effect due to rhGDNF on wet dog shakes and tonic-clonic seizures, followed by a Fisher exact test. Body weight comparisons were analyzed using Wald test, one way analysis of variance (ANOVA) followed by a Scheffe multiple comparison procedure. EXAMPLE 7 Results Peripheral injection of 12mg/kg kainate to Fischer 344 rats induced wet do shakes and seizures within two hours and mortality within the first 8 hours (Tabl 1 ). Table 1 GDNF///2//L Wet dog shakes Tonic-clinic si -ires De 50 2/10 0/10 0/ 5 5/8 1/8 00..55 171/17 00//77 0.05 8/8 7/8 2, inactive 8/8 7/8 Vehicle 13/13 13/13 2/ Table 1 shows the anti-convulsant activity of rhGDNF against kainic aci (12mg/kg s.c). Recombinant human GDNF, vehicle or inactive GDNF were give (icv) 1 hour before kainic acid. The values indicate the number of rats that had w dog shakes, tonic-clonic seizures or died. All animals were monitored for the fir 12 hours after administration of kainic acid and then on a daily basis. Using Fisher' exact test, the dose levels that were significant for wet dog shakes were 50μ (p = 0.00009) and 5//g (p =0.042). For tonic-clonic seizures doses 0.05 (p = 0.012 0.5 (p =0.00001), 5 (p = 0.00007) and 50 (p = 0.0000009) were significant. These behavioral changes as reported in Table 1 were consistent wit previous studies reported in Lothman & Collins, Brain Res.. 218:299-318 (1981 Intravβntricular rhGDNF (0.05-50_/g/? g) significantly (p =0.0036) attenuated kaini acid induced wet dog shakes in a dose-dependent manner. Similarly, kainic aci treated rats that received rhGDNF by the intracerebroveπtricular route at dose between (0.5-50/ / g/2 l) did not exhibit tonic-clonic seizure activity, whereas 50 of the animals at the low dose rhGDNF (O. Sμqll≠), and ail animals injected wit either vehicle (PBS n = 13) or inactive GDNF (2μql2μ\), had tonic-clonic seizure (p = 0.0008, logistic regression analysis; see Table 1). No deaths occurred in rats receiving rhGDNF whereas deaths occurred in rats receiving vehicle or inactive GDNF. Furthermore, rhGDNF delayed the onset of wet dog shakes. Vehicle treated animals displayed wet dog shakes within 30 minutes post kainic acid administration. Recombinant human GDNF (50 and 5μg/2 l) delayed the onset of wet dog shakes by a further 30-60 minutes, whereas the lower doses delayed the onset by only 15-20 minutes. Peripheral injection of kainate consistently produced selective hippocampal CA1 , thalamic, and amygdala neuronal loss that was detected seven days later. Histological examination of the hippocampus revealed a 50-60% loss of CA1 pyramidal cells in all animals that received vehicle or inactive GDNF (icv) compared to normal control animals (Fig 1 and 2). The loss of CA1 pyramidal cells by kainate was highly significant (p < 0.01 , students t-tβst). Administration of rhGDNF (0.5- 50μg/2μl, icv) significantly (p < 0.001) attenuated the extensive CA1 pyramidal ceil loss induced by kainate in both left and right hippocampi compared to the vehicle (2μ\ icv), low dose GDNF (0.05μg/2μl) or inactive GDNF (2μg/2μl) treated animals. The number of viable CA1 pyramidal cells was not significantly different in the rhGDNF (50//g) treated compared to normal animals (Figure 1). Kainate acid also caused extensive thalamic and amygdaloid neuronal loss which was significantly (p < 0.01) attenuated by rhGDNF (0.5-50 μq/μ\) (Figure 1 ). Protection by rhGDNF (50μg/2μl) was also shown against kainic acid induced neuronal cell loss by inhibiting the extensive necrosis and vacuolization of the thalamic formation by kainic acid without rhGDNF. Immunostained sections of rhGDNF (100 μg!4μi) injected rats revealed widespread distribution of the protein throughout the ventricular system, periventricular tissues, subarachnoid space and subjacent neuropil at 24 hours after the injection of rhGDNF. Positive immunostaining was present at the lateral aspect of the hippocampus in areas CA 1b, CA 1c, CA2 and CA3 which are adjacent to the posterior portions of the lateral ventricles. Administration of rhGDNF (\50μgl2μ) icv to naive animals produced a large decrease in body weight and a slower rate of body weight increase over the study duration compared to vehicle treated animals (Figure 3). The analysis showed both a difference in the rate of body weight change from day zero to day seven (Wal test p<0.001), and a difference in the total weight change (Wald test p<0.001) The change from baseline to day 7 in body weight between kainate and rhGDN dose groups, as well as the kainate and vehicle group were compared (one-wa ANOVA). The analysis revealed a clear difference between the weight chang among the treatment groups (p< 0.001). Lower doses of rhGDNF appear t attenuate the weight loss caused by kainate while producing no additional weigh loss themselves (Scheffe test p<0.05). However, the addition of higher doses o rhGDNF (50 and 5μglμl) appear to exacerebate weight loss (Scheffe test p<0.05 (Table 2). Table 2 Group Mean SD 50 /g rhGDNF -10.6 6.8 Vehicle 5.4 4.8 KA + Vehicle -6.5 9.0 KA + O.Oδμg rhGDNF 4.3 6.4 KA + O.S/tg rhGDNF 10.1 4.7 KA + 5μg rhGDNF -15.9 22.1 KA + 50// rhGDNF -31.4 11.9 Highly-purified rhGDNF promoted the survival in culture of chick sympathetic chain neurons. The chick embryo sympathetic chain neuronal survival assay on the chemically modified rhGDNF (up to 750ng/ml) showed no detectable biological activity when compared to the active rhGDNF (EC 50 10ng/ml). The inactive and active forms of GDNF were tested for lipopolysaccharide (LPS) and E. coli protein (ECP) levels. These levels were > 1 EU/mg and > 50 ppm respectively. The foregoing description of the invention is exemplary for purposes o illustration and explanation. It will be apparent to those skilled in the art that changes and modifications are possible without departing from the spirit and scope of the invention. It is intended that the following claims be interpreted to embrace ail such changes and modifications.

Claims: What is claimed is: 1. A method for inhibiting a neurodegenerative disorder associated wit seizure activity comprising administering to a patient in need thereof an effectiv amount of glial-derived neurotrophic factor (GDNF) to inhibit said neurodegenerativ disorder. 2. The method of claim 1 , wherein said neurodegenerative disorder i epilepsy. 3. The method of claim 1, wherein said GDNF is produced b recombinant DNA methods. 4. The method of claim 1 , wherein said seizure is caused by a deleteriou amount of kainic acid. 5. The method of claim 1, wherein said GDNF is administered in pharmaceutically acceptable carrier. 6. The method of claim 1, wherein said GDNF is administered intracranially. 7. A pharmaceutical composition comprising GDNF and a pharmaceutically acceptable carrier, wherein GDNF is in a therapeutically effective amount to inhibit a seizure.

Inventors: MARTIN DAVID, MARTIN, DAVID
Applicants: AMGEN BOULDER INC, MARTIN DAVID, AMGEN BOULDER INC., MARTIN, DAVID
Application year: 1995
Main classification: A61K38
IPC codes: A61K38, A61P25, C12N15, C12P21