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  Pharmaceutical Patents  

 

Title:  Polymer conjugates of mutated neublastin
United States Patent: 
7,442,370
Issued: 
October 28, 2008

Inventors:
 Sah; Dinah Wen-Yee (Boston, MA), Pepinsky; R. Blake (Arlington, MA), Boriack-Sjodin; Paula Ann (Waltham, MA), Miller; Stephan S. (Arlington, MA), Rossomando; Anthony (Revere, MA), Silvian; Laura (Waban, MA)
Assignee:
  Biogen Idec MA Inc. (Cambridge, MA)
Appl. No.:
 10/356,264
Filed:
 January 31, 2003


 

Executive MBA in Pharmaceutical Management, U. Colorado


Abstract

A dimer comprising a mutated neublastin polypeptide coupled to a polymer is disclosed. Such dimers exhibit prolonged bioavailability and, in preferred embodiments, prolonged biological activity relative to wild-type forms of neublastin.

Description of the Invention

Mutated Neublastin Polypeptides

The mutated neublastin polypeptides of the invention retain neurotrophic activity and have enhanced bioavailability as compared to the wild-type neublastin polypeptide. For example, the mutated neublastins of this invention activate the RET gene product in assays in which the wild-type neublastin activates RET. In general, the mutated neublastin polypeptide will retain at least one of the following features but will additionally comprise at least one modification, such that an internal polymer conjugation site is created: i) seven conserved cysteine residues at positions 16, 43, 47, 80, 81, 109, and 111 when numbered in accordance with SEQ ID NO:1-4; ii) amino acid residues as follows: C at position 16, L at position 18, V at position 25, L at position 28, G at position 29, L at position 30, G at position 31, E at position 36, F at position 40, R at position 41, F at position 42, C at position 43, G at position 45, Cat position 47, C at position 80, C at position 81, R at position 82, P at position 83, F at position 91, D at position 93, S at position 105, A at position 106, C at position 109 and C at position 111, each when numbered in accordance with SEQ ID NO:1-4; iii) an LGLG repeat (residues 28-31 of SEQ ID NO:1), an FRFC motif (residues 40-43 of SEQ ID NO:1), a QPCCRP motif (residues 78-83 of SEQ ID NO:1), and a SATACGC motif (residues 105-111 of SEQ ID NO:1).

In some embodiments, the invention provides a truncated mutated neublastin polypeptide, wherein the amino terminus of the truncated neublastin polypeptide lacks one or more amino-terminal amino acids of a mature neublastin polypeptide but is mutated to possess an internal polymer attachment. Preferably, the truncated mutated neublastin polypeptide, when dimerized, activates a RET polypeptide. In some embodiments the mutated neublastin polypeptide induces dimerization of the RET polypeptide. Such induction may require additional polypeptides or co-factors, as would be apparent to one of skill in the art.

Amino acid sequences of human and mouse neublastin polypeptides are disclosed in PCT publication WO00/01815. Examples of wild-type neublastin polypeptides according to the invention are presented in Table 1A (see Original Patent). A neublastin consensus sequence (consensus with respect to human, mouse and rat) is set forth in Table 1B (see Original Patent).

In some embodiments, at least one of the arginine (Arg or R) or asparagine (Asn or N) residues shown in bold in Table 1A is substituted with a different amino acid residue. In a preferred embodiment, the mutated neublastin polypeptide has a lysine (Lys or K) residue substituted for the asparagine at amino acid position 95, indicated by an asterisk in Table 1A, and is referred to as NBN-N95K. In general, the N95K substitution results in improved solubility. This facilitates formulation at high concentrations.

The invention includes a polymer-conjugated mutated neublastin polypeptide comprising an amino acid sequence that is, for example, at least 70% identical to amino acids 8-113 of SEQ ID NO:1 (also shown in Table 1). In one embodiment, one or more of the arginines at position 14, position 39, position 68, or the asparagine at position 95 is replaced by an amino acid other than arginine or asparagine. In one embodiment, the wild-type amino acid is substituted with lysine or cysteine.

The substituted residues in the mutated neublastin polypeptide can be chosen to facilitate coupling of a polymer, e.g., a polyalkylene glycol polymer, at the substituted amino acid. Advantageous sites of modification are those at solvent accessible regions in the neublastin polypeptide. Such sites can be chosen based on inspection of the crystal structure of the related neurotrophic factor, such as GDNF, whose crystal structure is described in Eigenbrot et al., Nat. Struct. Biol. 4:435-38, 1997. Sites also can be chosen based on the crystal structure of neublastin, whose crystallization and structure determination is described below. Also, sites can be chosen based on structural-functional information provided for persephin/neublastin chimeric proteins. These chimeras are described in Baloh et al., J. Biol. Chem. 275:3412-20, 2000. An exemplary listing of solvent accessible or surface exposed neublastin amino acids identified through this methodology is set forth in Table 2 (see Original Patent).

Table 2 provides a list of residues and numbers in human neublastin that are expected to be surface exposed. The first column refers to surface exposed residues determined by examining the structure of the rat GDNF dimer formed by chains A and B (PDB code 1AGQ) and determining whether a residue was on the surface of the structure. This structure was then compared to a sequence alignment of GDNF and neublastin in Baloh et al., Neuron 21:1291-1302, 1998 to determine the proper residues in neublastin. The second and third columns, respectively, refer to the surface exposed residues determined by examining the structure of the human neublastin dimer formed by chains A and B. The numbering scheme in Table 2 is that shown in Table 1.

Insome embodiments, the neublastin polypeptide retains the seven conserved Cys residues that are characteristic of the GDNF subfamily and of the TGF-beta super family.

The sequence of the human full-length prepro NBN polypeptide (SEQ ID NO:5) is shown in Table 3 (see Original Patent). Three mature forms of neublastin polypeptides were identified. These forms include: (i) the 140 AA polypeptide designated herein as NBN140, which possesses the amino acid sequence designated as SEQ ID NO:6; (ii) the 116 AA polypeptide designated herein as NBN116, which possesses the amino acid sequence designated as SEQ ID NO:7; and (iii) the 113 AA polypeptide designated herein as NBN113, which possesses the amino acid sequence designated as SEQ ID NO:2.

Table 3 illustrates the relationship between the disclosed prepro neublastin polypeptide sequences of the invention. Line 1 provides the polypeptide of SEQ ID NO:5, line 2 provides the polypeptide of SEQ ID NO:6, line 3 provides the polypeptide of SEQ ID NO:7 and line 4 provides the polypeptide of SEQ ID NO:2. The seven conserved cysteine residues are designated by symbols ("*", "#", "+" and "|") to indicate the intramolecular (* with *, # with #, and + with +) and intermolecular ("|") disulfide bridges formed in the mature dimerized neublastin ligand. The caret mark ("|") indicates the asparagine residue at amino acid position 95 that is substituted with a lysine in NBN106-N95K.

In alternative embodiments, the sequence of the above identified neublastin polypeptides have been truncated at their amino-terminal amino acid sequence. Examples of these include: (iv) the 112AA polypeptide sequence designated herein as NBN112, which possesses the 112 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 29-140 of SEQ ID NO:6 (SEQ ID NO:8) or amino acids 2-113 of SEQ ID NOs:1, 3, or 4. (v) the 111 AA polypeptide sequence designated herein as NBN111, which possesses the 111 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 30-140 of SEQ ID NO:6 (SEQ ID NO:9) or amino acids 3-113 of SEQ ID NOs:1, 3 or 4. (vi) the 110AA polypeptide sequence designated herein as NBN110, which possesses the 110 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 31-140 of SEQ ID NO:6 (SEQ ID NO:10) or amino acids 4-113 of SEQ ID NOs:1, 3 or 4. (vii) the 109AA polypeptide sequence designated herein as NBN109, which possesses the 109 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 32-140 of SEQ ID NO:6 (SEQ ID NO: 11) or amino acids 5-113 of SEQ ID NOs:1, 3 or 4. (viii) the 108AA polypeptide sequence designated herein as NBN108, which possesses the 108 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 33-140 of SEQ ID NO:6 (SEQ ID NO:12) or amino acids 6-113 of SEQ ID NOs:1, 3 or 4. (ix) the 107AA polypeptide sequence designated herein as NBN107, which possesses the 107 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 34-140 of SEQ ID NO:6 (SEQ ID NO:13) or amino acids 7-113 of SEQ ID NOs:1, 3 or 4. (x) the 106AA polypeptide sequence designated herein alternatively as NBN106 or N-7, which possesses the 106 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 35-140 of SEQ ID NO:6 (SEQ ID NO:14) or amino acids 8-113 of SEQ ID NOs:1, 3 or 4. (xi) the 105AA polypeptide sequence designated herein as NBN105, which possesses the 105 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 36-140 of SEQ ID NO:6 (SEQ ID NO:15) or amino acids 9-113 of SEQ ID NOs:1, 3 or 4. (xii) the 104AA polypeptide sequence designated herein alternatively as NBN104 or N-9, which possesses the 104 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 37-140 of SEQ ID NO:6 (SEQ ID NO:16) or amino acids 10-113 of SEQ ID NOs:1, 3 or 4. (xiii) the 103AA polypeptide sequence designated herein as NBN103, which possesses the 103 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 38-140 of SEQ ID NO:6 (SEQ ID NO:17) or amino acids 11-113 of SEQ ID NOs:1, 3 or 4. (xiv) the 102AA polypeptide sequence designated herein as NBN102, which possesses the 102 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 39-140 of SEQ ID NO:6 (SEQ ID NO:18) or amino acids 12-113 of SEQ ID NOs:1, 3 or 4. (xv) the 101AA polypeptide sequence designated herein as NBN101, which possesses the 101 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 40-140 of SEQ ID NO:6 (SEQ ID NO:19) or amino acids 13-113 of SEQ ID NOs:1, 3 or4. (xvi) the 100AA polypeptide sequence designated herein as NBN100, which possesses the 100 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 41-140 of SEQ ID NO:6 (SEQ ID NO:20) or amino acids 14-113 of SEQ ID NOs:1, 3 or 4. (xvii) the 99AA polypeptide sequence designated herein alternatively as NBN99 or N-14, which possesses the 99 carboxy terminal amino acids of a neublastin polypeptide, e.g., amino acids 42-140 of SEQ ID NO:6 (SEQ ID NO:21) or amino acids 15-113 of SEQ ID NOs:1, 3 or 4.

The polypeptide sequences of these truncated neublastin polypeptides are shown in Table 4 (see Original Patent) for NBN113 through NBN99. Disulfide bridge formation is as described for Table 3.

A mutated neublastin polypeptide according to the invention can be, e.g., at least 80%, 85%, 90%, 95%, 98% or 99% identical to amino acids 8-113 of SEQ ID NO:1. In some embodiments, the amino acid sequence of the mutated neublastin polypeptide includes the amino acid sequence of a naturally occurring rat, human or mouse neublastin polypeptide at amino acids 1-94 and 96-113 of the mutated neublastin polypeptide, e.g., the polypeptide has the amino acid sequence of SEQ ID NOs: 2, 3, or 4 at these positions.

A mutated neublastin polypeptide differing in sequence from those disclosed in SEQ ID NOs:1-4 may include one or more conservative amino acid substitutions. Alternatively, or in addition, the mutated neublastin polypeptide may differ by one or more non conservative amino acid substitutions, or by deletions or insertions. Preferably, the substitutions, insertions or deletions do not abolish the isolated protein's biological activity.

A conservative substitution is the substitution of one amino acid for another with similar characteristics. Conservative substitutions include substitutions within the following groups: valine, alanine and glycine; leucine, valine, and isoleucine; aspartic acid and glutamic acid; asparagine and glutamine; serine, cysteine, and threonine; lysine and arginine; and phenylalanine and tyrosine. The non-polar hydrophobic amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan and methionine. The polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine and glutamine. The positively charged (basic) amino acids include arginine, lysine and histidine. The negatively charged (acidic) amino acids include aspartic acid and glutamic acid. Any substitution of one member of the above-mentioned polar, basic or acidic groups by another member of the same group can be deemed a conservative substitution.

Other substitutions can be readily identified by those of ordinary skill in the art. For example, for the amino acid alanine, a substitution can be taken from any one of D-alanine, glycine, beta-alanine, cysteine and D-cysteine. For lysine, a replacement can be any one of D-lysine, arginine, D-arginine, homo-arginine, methionine, D-methionine, ornithine, or D-ornithine. Generally, substitutions in functionally important regions that may be expected to induce changes in the properties of isolated polypeptides are those in which: (i) a polar residue, e.g., serine or threonine, is substituted for (or by) a hydrophobic residue, e.g., leucine, isoleucine, phenylalanine, or alanine; (ii) a cysteine residue is substituted for (or by) any other residue; (iii) a residue having an electropositive side chain, e.g., lysine, arginine or histidine, is substituted for (or by) a residue having an electronegative side chain, e.g., glutamic acid or aspartic acid; or (iv) a residue having a bulky side chain, e.g., phenylalanine, is substituted for (or by) one not having such a side chain, e.g., glycine. The likelihood that one of the foregoing non-conservative substitutions may alter functional properties of the protein is also correlated to the position of the substitution with respect to functionally important regions of the protein. Some non-conservative substitutions may accordingly have little or no effect on biological properties.

In many cases, a polymer-conjugated mutated neublastin polypeptide has a longer serum half-life relative to the half-life of the wild-type polypeptide or mutated polypeptide in the absence of the polymer. In some embodiments, the polymer conjugated mutated neublastin polypeptide has significantly increased potency in vivo relative to the potency of the polypeptide or glycosylated-polypeptide in the absence of the polymer.

The polymer-conjugated neublastin polypeptide can be provided as a dimer that includes at least one polymer-conjugated neublastin polypeptide. In some embodiments, the dimer is a homodimer of polymer-conjugated mutated neublastin polypeptides. In other embodiments, the dimer is a homodimer of polymer-conjugated mutated truncated neublastin polypeptides. In other embodiments, the dimer is a heterodimer that includes one polymer-conjugated mutated neublastin polypeptide and one wild-type neublastin polypeptide. In other embodiments, the dimer is a heterodimer that includes one polymer-conjugated mutated neublastin polypeptide, and one polymer-conjugated wild-type neublastin polypeptide where the polymer conjugation is at the amino-terminus, and where the polypeptides may or may not be truncated. Other dimers include heterodimers or homodimers of polymer-conjugated mutated neublastin polypeptide forms that may or may not be truncated.

Provided in the invention are mature and truncated mutated polypeptide sequences comprising the carboxy-terminal-most amino acid residues of the preproNBN polypeptide, such as provided in SEQ ID NO:5, and which are designated herein as NBN#, where # represents the number of carboxy-terminal residues remaining in the referenced neublastin polypeptide. Polymer-conjugated neublastin polypeptides present in the bioactive neublastin dimers may be products of a protease cleavage reaction or a chemical cleavage reaction, or may be expressed from recombinant DNA construct, or may be synthesized. Example neublastin polypeptides include, e.g., NBN140, NBN116, and NBN113. Additional neublastin polypeptides of the invention include NBN112, NBN111, NBN110, NBN109, NBN108, NBN107, NBN106, NBN105, NBN104, NBN103, NBN102, NBN101, NBN100 and NBN99 (SEQ ID NOS:8-21).

A preferred polymer-conjugated neublastin polypeptide is a homodimer of NBN106-N95K conjugated either to three 10 kDa PEG moieties ("3.times.10 kDa PEG NBN106-N95K") or to four 10 kDa PEG moieties ("4.times.10 kDa PEG NBN106-N95K"). Also preferred is a mixed population of NBN106-N95K homodimers conjugated either to three 10 kDa PEG moieties or to four 10 kDa PEG moieties, referred to herein as "3(,4).times.10 kDa PEG NBN106-N95K". Also preferred is a 3(,4).times.10 kDa PEG NBN106-N95K homodimer, wherein the two amino-terminal amino acids are covalently linked to PEG moieties and the third and/or fourth PEG moiety is covalently linked to one or both substituted N95K residue(s).

In some embodiments, the polymer-conjugated neublastin polypeptide is based on the consensus sequence of SEQ ID NO:1. In certain embodiments, a polymer-conjugated neublastin polypeptide includes amino acids 1-7 of SEQ ID NO:1 in addition to amino acids 8-113.

In some embodiments, the polymer-conjugated neublastin polypeptide, when dimerized, binds GFR.alpha.3. In some embodiments, the polymer-conjugated neublastin polypeptide, when dimerized, stimulates tyrosine phosphorylation of a RET polypeptide, either on its own or when bound to GFR.alpha.3.

In some embodiments, the polymer-conjugated neublastin polypeptide, when dimerized, enhances neuron survival, e.g., enhances survival of a sensory neuron.

In some embodiments, the polymer-conjugated neublastin polypeptide, when dimerized, reduces or reverses pathological changes of a neuron, such as a sensory neuron.

In some embodiments, the polymer-conjugated neublastin polypeptide, when dimerized, enhances survival of a neuron, e.g., an autonomic neuron, or a dopaminergic neuron.

In some embodiments, the polymer-conjugated neublastin polypeptide includes one, two, three, four or more of the amino acid substitutions selected from the group consisting of an amino acid other than arginine at position 14 in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 39 in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 68 of the polymer-conjugated polypeptide, and an amino acid other than asparagine at position 95 of the polymer-conjugated polypeptide. In some embodiments, the amino acid at one or more of the amino acid at positions 14, 39, 68, and 95 is lysine. Preferably, amino acids 8-94 and 96-113 of the polymer-conjugated neublastin polypeptide are at least 90% identical to amino acids 8-94 and 96-113 of SEQ ID NO:1. More preferably, the amino acids sequences are at least 95% identical thereto. Most preferably, the amino acid sequence of the polymer-conjugated neublastin polypeptide includes the amino acid sequence of a naturally occurring human, mouse or rat neublastin polypeptide at amino acids 8-94 and 96-113 of the polymer-conjugated neublastin polypeptide. For example, amino acids 8-94 and 96-113 of the polymer-conjugated neublastin polypeptide can include the amino acid sequence of amino acids 8-94 and 96-113 of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3 or SEQ ID NO: 4. In the above embodiments, the preferred residue at amino acid position 95 is a lysine or a cysteine.

The invention includes a construct that is a heterodimer or a homodimer containing polymer-conjugated neublastin fusion proteins, e.g., the polyhistidine (His)-tagged neublastin provided in SEQ ID NO:36, or a neublastin fusion protein where the fusion moiety is an immunoglobulin (Ig) polypeptide,serum albumin polypeptide or a replicase-derived polypeptide. Neublastin fusion proteins can have enhanced pharmacokinetic and bioavailability properties in vivo.

The invention provides a nucleic acid molecule encoding a mature or truncated neublastin polypeptide, with a mutated polypeptide sequence. The nucleic acid molecule encoding a provided neublastin polypeptide is preferably provided in a vector, e.g., an expression vector. A mutated neublastin nucleic acid molecule, or a vector including the same, can be provided in a cell. The cell can be, e.g., a mammalian cell, fungal cell, yeast cell, insect cell, or bacterial cell. A preferred mammalian cell is a Chinese hamster ovary cell ("CHO cell").

Also provided by the invention is a method of making a polymer-conjugated neublastin polypeptide, by culturing a cell containing a nucleic acid encoding a neublastin polypeptide under conditions allowing for expression of a neublastin polypeptide. In some embodiments, the neublastin is conjugated to a naturally occurring moiety. In specific embodiments, the naturally occurring moiety is a glycosyl moiety. In certain embodiments, the glycosylated neublastin is expressed, e.g., in a CHO cell. The invention further includes a neublastin polypeptide expressed in a cell. Similar nucleic acids, vectors, host cells, and polypeptide production methods are disclosed herein for the fusion proteins (such as the neublastin-serum albumin fusion proteins) of this invention.

In some embodiments, a neublastin polypeptide that is expressed in a cell is recovered and conjugated to a polymer. In some embodiments, the polymer is a polyalkylene glycol moiety. In particular embodiments, the polymer is a PEG moiety.

Specifically provided by the invention is a composition that includes a mutated neublastin polypeptide coupled to a non-naturally occurring polymer. The mutated neublastin polypeptide in the composition preferably includes an amino acid sequence at least 70% identical to amino acids 8-113 of SEQ ID NO:1, provided that the polymer-conjugated neublastin polypeptide includes one or more of the amino acid substitutions selected from the group consisting of an amino acid other than arginine at position 14 in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 39 in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 68 of the polymer-conjugated polypeptide, and an amino acid other than asparagine at position 95 of the polymer-conjugated polypeptide, wherein the positions of the amino acids are numbered in accordance with the polypeptide sequence of SEQ ID NO:1.

The invention includes a stable, aqueous soluble conjugated neublastin polypeptide or mutated neublastin polypeptide complex comprising a neublastin polypeptide or mutated neublastin polypeptide coupled to a PEG moiety, wherein the neublastin polypeptide or mutated neublastin polypeptide is coupled to the PEG moiety by a labile bond. In some embodiments, the labile bond is cleavable by biochemical hydrolysis, proteolysis, or sulfhydryl cleavage. In some embodiments, the labile bond is cleavable under in vivo conditions.

Also provided by the invention is a method for making a modified neublastin polypeptide that has prolonged serum half-life relative to a wild-type neublastin. The method included providing a neublastin polypeptide or mutated neublastin polypeptide, and coupling the polypeptide or mutatedneublastin polypeptide to a non-naturally occurring polymer moiety, thereby forming a coupled polymer neublastin polypeptide composition.

The polymer-conjugated mutated neublastin polypeptides of this invention include one or more amino acid substitutions in which, for example, an amino acid other than arginine occurs at position 14 in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 39 occurs in the amino acid sequence of the polymer-conjugated polypeptide, an amino acid other than arginine at position 68 occurs in the polymer-conjugated polypeptide, or an amino acid other than asparagine at position 95 occurs in the polymer-conjugated polypeptide, when the positions of the amino acids are numbered in accordance with the polypeptide sequence of SEQ ID NO:1.

Synthesis and Isolation of Wild-Type and Mutated Neublastin Polypeptides

Neublastin polypeptides can be isolated using methods known in the art. Naturally occurring neublastin polypeptides can be isolated from cells or tissue sources by an appropriate purification scheme using standard protein purification techniques. Alternatively, mutated neublastin polypeptides can be synthesized chemically using standard peptide synthesis techniques. The synthesis of short amino acid sequences is well established in the peptide art. See, e.g., Stewart, et al., Solid Phase Peptide Synthesis (2d ed., 1984).

In some embodiments, mutated neublastin polypeptides are produced by recombinant DNA techniques. For example, a nucleic acid molecule encoding a mutated neublastin polypeptide can be inserted into a vector, e.g., an expression vector, and the nucleic acid can be introduced into a cell. Suitable cells include, e.g., mammalian cells (such as human cells or CHO cells), fungal cells, yeast cells, insect cells, and bacterial cells. When expressed in a recombinant cell, the cell is preferably cultured under conditions allowing for expression of a mutated neublastin polypeptide. The mutated neublastin polypeptide can be recovered from a cell suspension if desired. As used herein, "recovered" means that the mutated polypeptide is removed from those components of a cell or culture medium in which it is present prior to the recovery process. The recovery process may include one or more refolding or purification steps.

Mutated neublastin polypeptides can be constructed using any of several methods known in the art. One such method is site-directed mutagenesis, in which a specific nucleotide (or, if desired a small number of specific nucleotides) is changed in order to change a single amino acid (or, if desired, a small number of predetermined amino acid residues) in the encoded neublastin polypeptide. Those skilled in the art recognize that site-directed mutagenesis is a routine and widely used technique. In fact, many site-directed mutagenesis kits are commercially available. One such kit is the "Transformer Site Directed Mutagenesis Kit" sold by Clontech Laboratories (Palo Alto, Calif.).

Practice of the present invention will employ, unless indicated otherwise, conventional techniques of cell biology, cell culture, molecular biology, microbiology, recombinant DNA, protein chemistry, and immunology, which are within the skill of the art. Such techniques are described in the literature. See, for example, Molecular Cloning: A Laboratory Manual, 2nd edition. (Sambrook, Fritsch and Maniatis, eds.), Cold Spring Harbor Laboratory Press, 1989; DNA Cloning, Volumes I and II (D. N. Glover, ed), 1985; Oligonucleotide Synthesis, (M. J. Gait, ed.), 1984; U.S. Pat. No. 4,683,195 (Mullis et al.,); Nucleic Acid Hybridization (B. D. Haines and S. J. Higgins, eds.), 1984; Transcription and Translation (B. D. Hames and S. J. Higgins, eds.), 1984; Culture of Animal Cells (R. I. Freshney, ed). Alan R. Liss, Inc., 1987; Immobilized Cells and Enzymes, IRL Press, 1986; A Practical Guide to Molecular Cloning (13.Perbal), 1984; Methods in Enzymology, Volumes 154 and 155 (Wu et al., eds), Academic Press, New York; Gene Transfer Vectors for Mammalian Cells (J. H. Miller and M. P. Calos, eds.), 1987, Cold Spring Harbor Laboratory; Immunochernical Methods in Cell and Molecular Biology (Mayer and Walker, eds.), Academic Press, London, 1987; Handbook of Experiment Immunology, Volumes I-IV (D. M. Weir and C. C. Blackwell, eds.), 1986; Manipulating the Mouse Embryo, Cold Spring Harbor Laboratory Press, 1986.

Polymer Conjugation of Neublastin Polypeptides

Chemically modified neublastin polypeptides may be prepared by one of skill in the art based upon the present disclosure. The chemical moieties preferred for conjugation to a neublastin polypeptide are water-soluble polymers. A water-soluble polymer is advantageous because the protein to which it is attached does not precipitate in an aqueous environment, such as a physiological environment. Preferably, the polymer will be pharmaceutically acceptable for the preparation of a therapeutic product or composition.

If desired, a single polymer molecule may be employed for conjugation with a neublastin polypeptide, although more than one polymer molecule can be attached as well. Conjugated neublastin compositions of the invention may find utility in both in vivo as well as non-in vivo applications. Additionally, it will be recognized that the conjugating polymer may utilize any other groups, moieties, or other conjugated species, as appropriate to the end use application. By way of example, it may be useful in some applications to covalently bond to the polymer a functional moiety imparting UV-degradation resistance, or antioxidation, or other properties or characteristics to the polymer. As a further example, it may be advantageous in some applications to functionalize the polymer to render it reactive or cross-linkable in character, to enhance various properties or characteristics of the overall conjugated material. Accordingly, the polymer may contain any functionality, repeating groups, linkages, or other constituent structures that do not preclude the efficacy of the conjugated neublastin composition for its intended purpose.

One skilled in the art will be able to select the desired polymer based on such considerations as whether the polymer/protein conjugate will be used therapeutically, and if so, the desired dosage, circulation time, resistance to proteolysis, and other considerations. The effectiveness of the derivatization may be ascertained by administering the derivative, in the desired form (e.g., by osmotic pump, or, more preferably, by injection or infusion, or, further formulated for oral, pulmonary or other delivery routes), and determining its effectiveness.

Suitable water-soluble polymers include, but are not limited to, PEG, copolymers of ethylene glycol/propylene glycol, carboxymethylcellulose, dextran, polyvinyl alcohol, polyvinyl pyrrolidone, poly-1, 3-dioxolane, poly-1, 3, 6-trioxane, ethylene/maleic anhydride copolymer, polyaminoacids (either homopolymers or random copolymers), and dextran or poly(n-vinyl pyrrolidone) PEG, propropylene glycol homopolymers, polypropylene oxide/ethylene oxide co-polymers, polyoxyethylated polyols (e.g., glycerol), polyvinyl alcohol, and mixtures thereof.

The polymer may be of any suitable molecular weight, and may be branched or unbranched.

For PEG, suitable average molecular weight is between about 2 kDa and about 100 kDa. This provides for ease in handling and manufacturing. Those of skill in the art will appreciate that in preparations of PEG, some molecules will weigh more, some less, than the stated molecular weight. Thus, molecular weight is typically specified as "average molecular weight." Other molecular weights (sizes) may be used, depending on the desired therapeutic profile (e.g., the duration of sustained release desired; the effects, if any, on biological activity; the ease in handling; the degree or lack of antigenicity and other known effects of PEG on a therapeutic protein). In various embodiments, the molecular weight is about 2 kDa, about 5 kDa, about 10 kDa, about 15 kDa, about 20 kDa, about 25 kDa, about 30 kDa, about 40 kDa or about 100 kDa. In certain preferred embodiments, the average molecular weight of each PEG chain is about 20 kDa. In certain preferred embodiments, the average molecular weight is about 10 kDa.

The number of polymer molecules so attached may vary, and one skilled in the art will be able to ascertain the effect on function. One may mono-derivatize, or may provide for a di-, tri-, tetra- or some combination of derivatization, with the same or different chemical moieties (e.g., polymers, such as different weights of PEGs). The proportion of polymer molecules to protein (or polypeptide) molecules will vary, as will their concentrations in the reaction mixture. In general, the optimum ratio (in terms of efficiency of reaction in that there is no excess unreacted protein or polymer) will be determined by factors such as the desired degree of derivatization (e.g., mono, di-, tri-, etc.), the molecular weight of the polymer selected, whether the polymer is branched or unbranched, and the reaction conditions.

The PEG molecules (or other chemical moieties) should be attached to the protein with consideration of effects on functional or antigenic domains of the protein. There are a number of attachment methods available to those skilled in the art. See, e.g., EP 0 401384 (coupling PEG to G-CSF); Malik et al., Exp. Hematol. 20: 1028-1035, 1992 (reporting PEGylation of GM-CSF using tresyl chloride).

For example, PEG may be covalently bound (PEGylation) through amino acid residues via a reactive group, such as, a free amino or carboxyl group. The amino acid residues having a free amino group include lysine residues and the amino-terminal amino acid residue. Those having a free carboxyl group include aspartic acid residues, glutamic acid residues, and the C-terminal amino acid residue. Sulfhydryl groups may also be used as a reactive group for attaching the PEG molecule(s). For therapeutic purposes, attachment can be at an amino group, e.g. at the N-terminus or lysine group. One may specifically desire an amino-terminal chemically modified protein.

Using PEG as an illustration of the present compositions, one may select from a variety of PEG molecules (by molecular weight, branching, etc.), the proportion of PEG molecules to protein (or peptide) molecules in the reaction mix, the type of PEGylation reaction to be performed, and the method of obtaining the selected amino-terminally PEGylated protein. The method of obtaining the amino-terminal PEGylated preparation (i.e., separating this moiety from other monoPEGylated moieties if necessary) may be by purification of the amino-terminal PEGylated material from a population of PEGylated protein molecules. Selective amino-terminal chemical modification may be accomplished by reductive alkylation that exploits differential reactivity of different types of primary amino groups (lysine versus the amino-terminal) available for derivatization in a particular protein. Under the appropriate reaction conditions, substantially selective derivatization of the protein at the amino-terminus with a carbonyl group containing polymer is achieved. For example, one may selectively PEGylate the amino-terminus of the protein by performing the reaction at a pH which allows one to take advantage of the pKa differences between the epsilon (.epsilon.)-amino group of the lysine residues and that of the alpha (.alpha.)-amino group of the amino-terminal residue of the protein. By such selective derivatization, attachment of a water soluble polymer to a protein is controlled: the conjugation with the polymer takes place predominantly at the amino-terminus of the protein and no significant modification of other reactive groups, such as the lysine side chain amino groups, occurs.

Using reductive alkylation, the water-soluble polymer may be of the type described above, and should have a single reactive aldehyde for coupling to the protein. PEG propionaldehyde, containing a single reactive aldehyde, may be used.

The present invention includes mutated neublastin polypeptides that are expressed in prokaryotes or eukaryotes or made synthetically. In some embodiments, the neublastin is glycosylated. In some specific embodiments, the neublastin dimer is polymer-conjugated at each amino-terminus and glycosylated at each internal Asn95 residue. In other embodiments, the mutated neublastin dimer is polymer-conjugated at each amino-terminus and polymer-conjugated at one or both internal Lys95 residues.

PEGylation may be carried out by any suitable PEGylation reaction. Various PEGylation chemistries are known in the art. See, e.g., Focus on Growth Factors, 3 (2): 4-10, 1992; EP 0 154 316; EP 0 401 384; and the other publications cited herein that relate to PEGylation. The PEGylation may be carried out via an acylation reaction or an alkylation reaction with a reactive PEG molecule (or an analogous reactive water-soluble polymer).

PEGylation by acylation generally involves reacting an active ester derivative of PEG. Any known or subsequently discovered reactive PEG molecule may be used to carry out the PEGylation. A preferred activated PEG ester is PEG esterified to N-hydroxysuccinimide (NHS). As used herein, "acylation" includes without limitation the following types of linkages between the therapeutic protein and a water soluble polymer such as PEG: amide, carbamate, urethane, and the like. See, Bioconjugate Chem. 5: 133-140, 1994. Reaction conditions may be selected from any of those known in the PEGylation art or those subsequently developed, but should avoid conditions such as temperature, solvent, and pH that would inactivate the neublastin protein or polypeptide to be modified.

PEGylation by acylation will generally result in a poly-PEGylated neublastin protein product. Preferably, the connecting linkage will be an amide. Also preferably, the resulting product will be substantially only (e.g., >95%) mono, di- or tri-PEGylated. However, some species with higher degrees of PEGylation may be formed in amounts depending on the specific reaction conditions used. If desired, more purified PEGylated species may be separated from the mixture, particularly unreacted species, by standard purification techniques, including, among others, dialysis, salting-out, ultrafiltration, ion-exchange chromatography, gel filtration chromatography and electrophoresis.

PEGylation by alkylation generally involves reacting a terminal aldehyde derivative of PEG with neublastin in the presence of a reducing agent. PEGylation by alkylation can also result in poly-PEGylated neublastin protein products. In addition, one can manipulate the reaction conditions to favor PEGylation substantially only at the .alpha.-amino group of the amino-terminus of neublastin (i.e., a mono-PEGylated protein). In either case of mono-PEGylation or poly-PEGylation, the PEG groups are preferably attached to the protein via a --CH.sub.2--NH-- group. With particular reference to the --CH.sub.2-- group, this type of linkage is referred to herein as an "alkyl" linkage.

Derivatization via reductive alkylation to produce a mono-PEGylated product exploits differential reactivity of different types of primary amino groups (lysine versus the amino-terminal) available for derivatization. The reaction is performed at a pH that allows one to take advantage of the pKa differences between the .epsilon.-amino groups of the lysine residues and that of the .alpha.-amino group of the amino-terminal residue of the protein. By such selective derivatization, attachment of a water soluble polymer that contains a reactive group such as an aldehyde, to a protein is controlled: the conjugation with the polymer takes place predominantly at the amino-terminus of the protein and no significant modification of other reactive groups, such as the lysine side chain amino groups, occurs.

The polymer molecules used in both the acylation and alkylation approaches may be selected from among water-soluble polymers as described above. The polymer selected should be modified to have a single reactive group, such as an active ester for acylation or an aldehyde for alkylation, preferably, so that the degree of polymerization may be controlled as provided for in the present methods. An exemplary reactive PEG aldehyde is PEG propionaldehyde, which is water stable, or mono C1-C10 alkoxy or aryloxy derivatives thereof (see, U.S. Pat. No. 5,252,714). The polymer may be branched or unbranched. For the acylation reactions, the polymer(s) selected should have a single reactive ester group. For the present reductive alkylation, the polymer(s) selected should have a single reactive aldehyde group. Generally, the water-soluble polymer will not be selected from naturally-occurring glycosyl residues since these are usually made more conveniently by mammalian recombinant expression systems. The polymer may be of any molecular weight, and may be branched or unbranched.

An exemplary water-soluble polymer for use herein is PEG. As used herein, polyethylene glycol encompasses any of the forms of PEG that have been used to derivatize other proteins, including but not limited to, e.g., mono-(C1-C10) alkoxy- or aryloxy-PEG.

In general, chemical derivatization may be performed under any suitable condition used to react a biologically active substance with an activated polymer molecule. Methods for preparing a PEGylated neublastin will generally comprise the steps of (a) reacting a neublastin protein or polypeptide with PEG (such as a reactive ester or aldehyde derivative of PEG) under conditions whereby the molecule becomes attached to one or more PEG groups, and (b) obtaining the reaction product(s). In general, the optimal reaction conditions for the acylation reactions will be determined case by case based on known parameters and the desired result. For example, the larger the ratio of PEG:protein, the greater the percentage of poly-PEGylated product.

Reductive alkylation to produce a substantially homogeneous population of mono-polymer/neublastin will generally comprise the steps of: (a) reacting a neublastin protein or polypeptide with a reactive PEG molecule under reductive alkylation conditions, at a pH suitable to pen-nit selective modification of the .alpha.-amino group at the amino terminus of neublastin; and (b) obtaining the reaction product(s).

For a substantially homogeneous population of mono-polymer/neublastin, the reductive alkylation reaction conditions are those that permit the selective attachment of the water-soluble polymer moiety to the amino-terminus of neublastin. Such reaction conditions generally provide for pKa differences between the lysine amino groups and the .alpha.-amino group at the amino-terminus (the pKa being the pH at which 50% of the amino groups are protonated and 50% are not). The pH also affects the ratio of polymer to protein to be used. In general, if the pH is lower, a larger excess of polymer to protein will be desired (i.e., the less reactive the amino-terminal .alpha.-amino group, the more polymer needed to achieve optimal conditions). If the pH is higher, the polymer:protein ratio need not be as large (i.e., more reactive groups are available, so fewer polymer molecules are needed). For purposes of the present invention, the pH will generally fall within the range of 3-9, preferably 3-6.

Another important consideration is the molecular weight of the polymer. In general, the higher the molecular weight of the polymer, the fewer polymer molecules may be attached to the protein. Similarly, branching of the polymer should be taken into account when optimizing these parameters. Generally, the higher the molecular weight (or the more branches) the higher the polymer:protein ratio. In general, for the PEGylation reactions included herein, the preferred average molecular weight is about 2 kDa to about 100 kDa. The preferred average molecular weight is about 5 kDa to about 50 kDa, particularly preferably about 10 kDa to about 20 kDa. The preferred total molecular weight is about 10 kDa to about 40 kDa.

In some embodiments, the neublastin polypeptide is linked to the polymer via a terminal reactive group on the polypeptide. Alternatively, or in addition, the neublastin polypeptide may be linked via the side chain amino group of an internal lysine residue, e.g., a lysine residue introduced into the amino acid sequence of a naturally occurring neublastin polypeptide. Thus, conjugations can also be branched from the non terminal reactive groups. The polymer with the reactive group(s) is designated herein as "activated polymer". The reactive group selectively reacts with reactive groups on the protein, e.g., free amino.

Attachment may occur in the activated polymer at any available neublastin amino group such as the alpha amino groups or the epsilon amino groups of a lysine residue or residues introduced into the amino acid sequence of a neublastin polypeptide. Free carboxylic groups, suitably activated carbonyl groups, hydroxyl, guanidyl, imidazole, oxidized carbohydrate moieties and mercapto groups of the neublastin (if available) can also be used as attachment sites.

Generally from about 1.0 to about 10 moles of activated polymer per mole of protein, depending on protein concentration, is employed. The final amount is a balance between maximizing the extent of the reaction while minimizing non-specific modifications of the product and, at the same time, defining chemistries that will maintain optimum activity, while at the same time optimizing, if possible, the half-life of the protein. Preferably, at least about 50% of the biological activity of the protein is retained, and most preferably near 100% is retained.

The polymer can be coupled to the neublastin polypeptide using methods known in the art. For example, in one embodiment, the polyalkylene glycol moiety is coupled to a lysine group of the mutated neublastin polypeptide. Linkage to the lysine group can be performed with an N-hydroxylsuccinimide (NHS) active ester such as PEG succinimidyl succinate (SS-PEG) and succinimidyl propionate (SPA-PEG). Suitable polyalkylene glycol moieties include, e.g., carboxymethyl-NHS, norleucine-NHS, SC-PEG, tresylate, aldehyde, epoxide, carbonylimidazole, and PNP carbonate.

Additional amine reactive PEG linkers can be substituted for the succinimidyl moiety. These include, e.g. isothiocyanates, nitrophenylcarbonates, epoxides, and benzotriazole carbonates. Conditions are preferably chosen to maximize the selectivity and extent or reaction.

If desired, polymer-conjugated neublastin polypeptides may contain a tag, e.g., a tag that can subsequently be released by proteolysis. Thus, the lysine moiety can be selectively modified by first reacting a His-tag modified with a low molecular weight linker such as Traut's reagent (Pierce) which will react with both the lysine and amino-terminus, and then releasing the his tag. The polypeptide will then contain a free SH group that can be selectively modified with a PEG containing a thiol reactive head group such as a maleimide group, a vinylsulfone group, a haloacetate group, or a free or protected SH.

Traut's reagent can be replaced with any linker that will set up a specific site for PEG attachment. By way of example, Traut's reagent could be replaced with SPDP, SMPT, SATA, or SATP (all available from Pierce). Similarly one could react the protein with an amine reactive linker that inserts a maleimide (for example SMCC, AMAS, BMPS, MBS, EMCS, SMPB, SMPH, KMUS, or GMBS), a haloacetate group (SBAP, SIA, SIAB), or a vinylsulfone group and react the resulting product with a PEG that contains a free SH. The only limitation to the size of the linker that is employed is that it cannot block the subsequent removal of the amino-terminal tag.

Thus, in other embodiments, the polyalkylene glycol moiety is coupled to a cysteine group of the mutated neublastin polypeptide. Coupling can be effected using, e.g., a maleimide group, a vinylsulfone group, a haloacetate group, and a thiol group.

In preferred embodiments, the polymer-conjugated neublastin polypeptide in the composition has a longer serum half-life relative to the half-life of the neublastin polypeptide in the absence of the polymer. Alternatively, or in addition, the polymer-conjugated neublastin polypeptide dimer in the composition binds GFR.alpha., activates RET, normalizes pathological changes of a neuron, enhances survival of a neuron, or ameliorates neuropathic pain, or performs a combination of these physiological functions. Assays for determining whether a polypeptide enhances survival of a neuron, or normalizes pathological changes of a neuron, are described in, e.g., WO00/01815. Preferably, the neuron is a sensory neuron, an autonomic neuron, or a dopaminergic neuron.

In preferred embodiments, the composition is provided as a stable, aqueous soluble conjugated neublastin polypeptide complex comprising a neublastin polypeptide or mutated neublastin polypeptide coupled to a PEG moiety. If desired, the neublastin polypeptide or mutated neublastin polypeptide may be coupled to the PEG moiety by a labile bond. The labile bond can be cleaved in, e.g., biochemical hydrolysis, proteolysis, or sulfhydryl cleavage. For example, the bond can be cleaved under in vivo (physiological) conditions.

Other reaction parameters, such as solvent, reaction times, temperatures, etc., and means of purification of products, can be determined case by case based on the published information relating to derivatization of proteins with water soluble polymers.

If desired, a single polymer molecule for conjugation per neublastin polypeptides may be employed. Alternatively, more than one polymer molecule may be attached. Conjugated neublastin compositions of the invention may find utility in both in vivo as well as non-in vivo applications. Additionally, it will be recognized that the conjugating polymer may utilize any other groups, moieties, or other conjugated species, as appropriate to the end use application. By way of example, it may be useful in some applications to covalently bond to the polymer a functional moiety imparting UV-degradation resistance, or antioxidation, or other properties or characteristics to the polymer. As a further example, it may be advantageous in some applications to functionalize the polymer to render it reactive or cross-linkable in character, to enhance various properties or characteristics of the overall conjugated material. Accordingly, the polymer may contain any functionality, repeating groups, linkages, or other constituent structures that do not preclude the efficacy of the conjugated neublastin mutein composition for its intended purpose.

Illustrative polymers that may usefully be employed to achieve these desirable characteristics are described herein below in exemplary reaction schemes. In covalently bonded peptide applications, the polymer may be functionalized and then coupled to free amino acid(s) of the peptide(s) to form labile bonds.

The reactions may take place by any suitable method used for reacting biologically active materials with inert polymers, preferably at about pH 5-8, e.g., pH 5, 6, 7, or 8, if the reactive groups are on the alpha amino group at the amino-terminus. Generally the process involves preparing an activated polymer and thereafter reacting the protein with the activated polymer to produce the soluble protein suitable for formulation. The above modification reaction can be performed by several methods, which may involve one or more steps.

Linear and branched forms of PEG can be used as well as other alkyl forms. The length of the PEG can be varied. Most common forms vary in size from 2K-100 kDa. While the present examples report that targeted PEGylation at the amino-terminus does not affect pharmokinetic properties, the fact that the material retained physiological function indicates that modification at the site or sites disclosed herein is not deleterious. Consequently, in generating mutant forms of neublastin that could provide additional sites of attachment through insertion of lysine residues, the likely outcome that these forms would be PEGylated both at the lysine and at the amino-terminus is encompassed by the invention.

One or more sites on a neublastin polypeptide can be coupled to a polymer. For example, one two, three, four, or five PEG moieties can be attached to the polypeptide. In some embodiments, a PEG moiety is attached at the amino terminus and/or amino acids 14, 39, 68, and 95 of a neublastin polypeptide numbered as shown in Table 1 and SEQ ID NO:1.

In advantageous embodiments, the polymer-conjugated neublastin polypeptide in the composition has a longer serum half-life relative to the half-life of the neublastin wild-type or mutated polypeptide in the absence of the polymer. Alternatively, or in addition, the polymer-conjugated neublastin polypeptide in the composition binds GFR.alpha.3, activates RET, normalizes pathological changes of a neuron, enhances survival of a neuron, or ameliorates neuropathic pain, or performs a combination of these physiological functions.

In some embodiments, the mutated neublastin polypeptide or polymer conjugate in the complex has a physiological activity selected from the group consisting of: GFR.alpha.3 binding, RET activation, normalization of pathological changes of a neuron, enhancing neuron survival, or ameliorating neuropathic pain.

Also provided by the invention are multimeric polypeptides that include a polymer-conjugated neublastin polypeptide. The multimeric polypeptides are preferably provided as purified multimeric polypeptides. Examples of multimeric complexes include, e.g., dimeric complexes. The multimeric complex can be provided as a heteromeric or homomeric complex. Thus, the multimeric complex can be a heterodimeric polymer-conjugated polypeptide complex including one mutated neublastin polypeptide and one non-mutated neublastin or a heterodimeric polymer-conjugated polypeptide complex including two or more mutated neublastin polypeptides.

In some embodiments, the polymer-conjugated neublastin polypeptide binds GFR.alpha.3. Preferably, binding of the polymer-conjugated neublastin polypeptide stimulates phosphorylation of a RET polypeptide. To determine whether a polypeptide binds GFR.alpha.3, assays can be performed as described in WO00/01815. For example, the presence of neublastin in the media of CHO cell line supernatants can be described using a modified form of a ternary complex assay described by Sanicola et al. (Proc. Natl. Acad. Sci. USA, 1997, 94: 6238). In this assay, the ability of GDNF-like molecules can be evaluated for their ability to mediate binding between the extracellular domain of RET and the various co-receptors, GFR.alpha.1, GFR.alpha.2, and GFR.alpha.3. Soluble forms of RET and the co-receptors are generated as fusion proteins. A fusion protein between the extracellular domain of rat RET and placental alkaline phosphatase (RET-AP) and a fusion protein between the extracellular domain of rat GFR.alpha.-1 (disclosed in published application WO9744356; Nov. 27, 1997) and the Fc domain of human IgG1 (rGFR(.alpha.1-Ig) have been described (Sanicola et al., Proc. Natl. Acad. Sci. USA 1997, 94: 6238).

The polymer of the invention is preferably a polyalkylene glycol moiety, and more preferably a PEG moiety. In some embodiments, a polymeric moiety has an average molecular weight of about 100 Da to about 25,000 Da; of about 1000 Da to about 20,000 Da; or of about 5000 Da to about 20,000 Da. In some embodiments, at least one polymeric moiety has an average molecular weight of about 5000 Da; an average molecular weight of about 10,000 Da; or an average molecular weight of about 20,000 Da.

The functional group on the polyalkylene glycol moiety can be, e.g., carboxymethyl-NHS, norleucine-NHS, SC-PEG, tresylate, aldehyde, epoxide, carbonylimidazole, or PNP carbonate. Coupling can occur via an N-hydroxylsuccinimide (NHS) active ester. The active ester can be, e.g., PEG succinimidyl succinate (SS-PEG), succinimidyl butyrate (SPB-PEG), or succinimidyl propionate (SPA-PEG). In some embodiments, the polyalkylene glycol moiety is coupled to a cysteine group of the neublastin polypeptide or mutated neublastin polypeptide. For example, coupling can occur via a maleimide group, a vinylsulfone group, a haloacetate group, and a thiol group. In various embodiments, the neublastin polypeptide or mutated neublastin polypeptide comprises one, two, three, or four PEG moieties.

In some embodiments, the polymer is coupled to the polypeptide at a site on the neublastin that is an N terminus. In some embodiments, the polymer is coupled to the polypeptide at a site in a non-terminal amino acid of the neublastin polypeptide or mutated neublastin polypeptide. In some embodiments, the polymer is coupled to a solvent exposed amino acid of the neublastin polypeptide or mutated neublastin polypeptide.

In some embodiments, the polymer is coupled to the neublastin polypeptide or mutated neublastin polypeptide at a residue selected from the group consisting of the amino terminal amino acid of the polymer-conjugated polypeptide, position 14 in the amino acid sequence of the neublastin polypeptide or mutated neublastin polypeptide, position 39 in the amino acid sequence of the neublastin polypeptide or mutated neublastin polypeptide, position 68 in the amino acid sequence of the neublastin polypeptide or mutated neublastin polypeptide, and position 95 in the amino acid sequence of the neublastin polypeptide or mutated polypeptide.

Polymer-Conjugated Neublastin Fusion Proteins

If desired, the polymer-conjugated neublastin polypeptide can be provided as a fusion protein. Fusion polypeptide derivatives of proteins of the invention also include various structural forms of the primary protein that retain biological activity.

Polymer-conjugated neublastin-serum albumin fusions can be constructed using methods known in the art. Any of a number of cross-linkers that contain a corresponding amino reactive group and thiol reactive group can be used to link neublastin to serum albumin. Examples of suitable linkers include amine reactive cross-linkers that insert a thiol reactive-maleimide. These include, e.g., SMCC, AMAS, BMPS, MBS, EMCS, SMPB, SMPH, KMUS, or GMBS. Other suitable linkers insert a thiol reactive-haloacetate group. These include, e.g., SBAP, SIA, SIAB and that provide a protected or non protected thiol for reaction with sulfhydryl groups to product a reducible linkage are SPDP, SMPT, SATA, or SATP all of which are commercially available (e.g., Pierce Chemicals). One skilled in the art can similarly envision with alternative strategies that will link the amino-terminus of neublastin with serum albumin.

It is also envisioned that one skilled in the art can generate conjugates to serum albumin that are not targeted at the amino-terminus of neublastin or at the thiol moiety on serum albumin. If desired, neublastin-serum albumin fusions can be generated using genetic engineering techniques, wherein neublastin is fused to the serum albumin gene at its amino-terminus carboxy-terminus, or at both ends.

Any neublastin conjugate that results in a product with a prolonged half-life, for example, in vivo or, specifically, in animals (including humans) can be generated using a similar strategy. Another example of a neublastin conjugate that results in a product with a prolonged half-life in vivo is a neublastin fusion protein where the fusion partner is an Ig.

Other derivatives of polymer-conjugated neublastins include covalent or aggregate conjugates of mutated neublastin or its fragments with other proteins or polypeptides, such as by synthesis in recombinant culture as additional amino-termini, or carboxy-termini. For example, the conjugated peptide may be a signal (or leader) polypeptide sequence at the amino-terminal region of the protein which co-translationally or post-translationally directs transfer of the protein from its site of synthesis to its site of function inside or outside of the cell membrane or wall (e.g., the yeast alpha-factor leader). Neublastin receptor proteins can comprise peptides added to facilitate purification or identification of neublastin (e.g., histidine/neublastin fusions). The amino acid sequence of neublastin can also be linked to the peptide Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys (DYKDDDDK) (SEQ ID NO:22) (Hopp et al., Biotechnology 6:1204 (1988)). The latter sequence is highly antigenic and provides an epitope reversibly bound by a specific monoclonal antibody, enabling rapid assay and facile purification of expressed recombinant protein.

This sequence is also specifically cleaved by bovine mucosal enterokinase at the residue immediately following the Asp-Lys pairing.

Bioactive Polypeptides

The polypeptides of the invention may be provided in any bioactive form, including the form of pre-pro-proteins, pro-proteins, mature proteins, glycosylated proteins, non-glycosylated proteins, phosphorylated proteins, non-phosphorylated proteins, truncated forms, or any other posttranslational modified protein. A bioactive neublastin polypeptide includes a polypeptide that, for example, when dimerized, alone or in the presence of a cofactor (such as GFR.alpha.3, or RET), binds to RET, induces dimerization of RET, and autophosphorylation of RET.

The polypeptides of the invention may in particular be an N-glycosylated polypeptide, which polypeptide preferably is glycosylated at the N-residues indicated in the sequence listings.

In some embodiments, a polypeptide of the invention has the amino acid sequence presented as SEQ ID NO:6, holding a glycosylated asparagine residue at position 122; or the amino acid sequence presented as SEQ ID NO:14, holding a glycosylated asparagine residue at position 95, or the analogous position in any mutated neublastin polypeptide when aligned by, e.g., ClustalW computer software.

In some embodiments, the polypeptide of the invention has the amino acid sequence presented as SEQ ID NO:23, referred to herein as NBN113-N95K, containing a lysine residue substituted for the asparagine residue at position 95 of SEQ ID NO:2; or the amino acid sequence presented as SEQ ID NO:24, referred to herein as NBN106-N95K; or the analogous position in any mutated neublastin polypeptide when aligned by, e.g., ClustalW computer software.

This invention also includes mutated neublastin fusion proteins, such as Ig-fusions, as described, e.g., in U.S. Pat. No. 5,434,131, or serum albumin fusions.

In some embodiments, the invention provides a polypeptide having the amino acid sequence shown as SEQ ID NO:1 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:1.

In other embodiments, the invention provides a polypeptide having the amino acid sequence of SEQ ID NO:2 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:2.

In some embodiments, the invention provides a polypeptide having the amino acid sequence of SEQ ID NO:3 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:3.

In some embodiments, the invention provides a polypeptides having the amino acid sequence of SEQ ID NO:4 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:4.

In some embodiments, the invention provides a polypeptide having the amino acid sequence of SEQ ID NO:5 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:5.

In some embodiments, the invention provides a polypeptides having the amino acid sequence of SEQ ID NO:6 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:6.

In some embodiments, the invention provides a polypeptide having the amino acid sequence of SEQ ID NO:7 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:7.

In some embodiments, the invention provides a polypeptide having the amino acid sequence of any one of SEQ ID NOs:8-21 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as any one of SEQ ID NOs:8-21.

In some embodiments, the invention provides a polypeptide having the amino acid sequence of SEQ ID NO:36 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to the sequence presented as SEQ ID NO:36.

In further embodiments, the invention provides a polypeptide having the amino acid sequence of any one of SEQ ID NOS:1-21 and 36 with the exception of one substitution, or an amino acid sequence that has at least about 85%, preferably at least about 90%, more preferably at least about 95%, more preferably at least about 98%, and most preferably at least about 99% identity to any one of the sequences presented as SEQ ID NOS:1-21 and 36.

In other embodiments, the mutated polypeptide of the invention holds the GDNF subfanily fingerprint, i.e. the conserved cysteine amino acid residues designated in Tables 3 and 4 (see Original Patent).

In some embodiments, the invention provides a mutated polypeptide encoded by a polynucleotide sequence capable of hybridizing under high stringency conditions with the polynucleotide sequence encoding the polypeptide of SEQ ID NO:1, its complementary strand, or a sub-sequence thereof. In some embodiments, the mutated polypeptide of the invention is encoded by a polynucleotide sequence having at least 70% identity to the polynucleotide sequence encoding the polypeptide of SEQ ID NO:1.

In some embodiments, the invention provides novel polypeptides encoded by a polynucleotide sequence capable of hybridizing under high stringency conditions with the polynucleotide sequence encoding the polypeptide of SEQ ID NO:2, its complementary strand, or a sub-sequence thereof. In some embodiments, the mutated polypeptide of the invention is encoded by a polynucleotide sequence having at least 70% identity to the polynucleotide sequence encoding the polypeptide of SEQ ID NO:2.

In some embodiments, the invention provides mutated polypeptides encoded by a polynucleotide sequence capable of hybridizing under high stringency conditions with the polynucleotide sequence encoding the polypeptide of any one of SEQ ID NOs:8-21, its complementary strand, or a sub-sequence thereof. In other embodiments, the mutated polypeptide of the invention is encoded by a polynucleotide sequence having at least 70% identity to the polynucleotide sequence encoding the polypeptide of any one of SEQ ID NO: 8-21.

In some embodiments, the invention provides novel polypeptides encoded by a polynucleotide sequence capable of hybridizing under high stringency conditions with the polynucleotide sequence encoding the polypeptide of SEQ ID NO:36, its complementary strand, or a sub-sequence thereof. In some embodiments, the mutated polypeptide of the invention is encoded by a polynucleotide sequence having at least 70% identity to the polynucleotide sequence encoding the polypeptide of SEQ ID NO:36.

Biological Origin

A non-conjugated neublastin polypeptide dimer can be isolated and then conjugated to one or more polymers to obtain a polymer conjugated neublastin polypeptide dimer of the invention. The neublastin polypeptide dimer can be isolated from a mammalian cell, preferably from a human cell or from a cell of murine origin or from a cell of Chinese hamster ovary origin.

Neurotrophic Activity

Modified neublastin polypeptides, including truncated neublastin polypeptides, of the invention are useful for moderating metabolism, growth, differentiation, or survival of a nerve or neuronal cell. In particular, modified neublastin polypeptides are used to treat or alleviate a disorder or disease of a living animal, e.g., a human, which disorder or disease is responsive to the activity of a neurotrophic agent. Such treatments and methods are described in more detail below.

Pharmaceutical Compositions Comprising Neublastin-Polymer Conjugates

Also provided is a pharmaceutical composition comprising a modified neublastin polypeptide dimer of the present invention.

The polymer-neublastin conjugates of the invention may be administered per se as well as in the form of pharmaceutically acceptable esters, salts, and other physiologically functional derivatives thereof. In such pharmaceutical and medicament formulations, the polymer-conjugated neublastin conjugate preferably is utilized together with one or more pharmaceutically acceptable carrier(s) and optionally any other therapeutic ingredients.

The carrier(s) must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not unduly deleterious to the recipient thereof. The polymer-conjugated neublastin is provided in an amount effective to achieve a desired pharmacological effect or medically beneficial effect, as described herein, and in a quantity appropriate to achieve the desired bioavailable in vivo dose or concentration.

The formulations include those suitable for parenteral as well as non parenteral administration, and specific administration modalities include oral, rectal, buccal, topical, nasal, ophthalmic, subcutaneous, intramuscular, intravenous, transdermal, intrathecal, intra-articular, intra-arterial, sub-arachnoid, bronchial, lymphatic, vaginal, and intra-uterine administration. Formulations suitable for aerosol and parenteral administration, both locally and systemically, are preferred.

When the polymer-conjugated neublastin is utilized in a formulation comprising a liquid solution, the formulation advantageously may be administered orally, bronchially, or parenterally. When the polymer-conjugated neublastin is employed in a liquid suspension formulation or as a powder in a biocompatible carrier formulation, the formulation may be advantageously administered orally, rectally, or bronchially. Alternatively, it may be administered nasally or bronchially, via nebulization of the powder in a carrier gas, to form a gaseous dispersion of the powder that is inspired by the patient from a breathing circuit comprising a suitable nebulizer device.

The formulations comprising the proteins of the present invention may conveniently be presented in unit dosage forms and may be prepared by any of the methods well known in the art of pharmacy. Such methods generally include the step of bringing the active ingredient(s) into association with a carrier that constitutes one or more accessory ingredients.

Typically, the formulations are prepared by uniformly and intimately bringing the active ingredient(s) into association with a liquid carrier, a finely divided solid carrier, or both, and then, if necessary, shaping the product into dosage forms of the desired formulation.

Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets, tablets, or lozenges, each comprising a predetermined amount of the active ingredient as a powder or granules; or a suspension in an aqueous liquor or a non-aqueous liquid, such as a syrup, an elixir, an emulsion, or a draught.

Formulations suitable for parenteral administration conveniently comprise a sterile aqueous preparation of the active conjugate, which preferably is isotonic with the blood of the recipient (e.g., physiological saline solution). Such formulations may include suspending agents and thickening agents or other microparticulate systems which are designed to target the compound to blood components or one or more organs. The formulations may be presented in unit-dose or multi-dose form.

Nasal spray formulations comprise purified aqueous solutions of the active conjugate with preservative agents and isotonic agents. Such formulations are preferably adjusted to a pH and isotonic state compatible with the nasal mucus membranes.

Formulations for rectal administration may be presented as a suppository with a suitable carrier such as cocoa butter, hydrogenated fats, or hydrogenated fatty carboxylic acid. Ophthalmic formulations such as eye drops are prepared by a similar method to the nasal spray, except that the pH and isotonic factors are preferably adjusted to match that of the eye.

Topical formulations comprise the conjugates of the invention dissolved or suspended in one or more media, such as mineral oil, petroleum, polyhydroxy alcohols, or other bases used for topical pharmaceutical formulations.

In addition to the aforementioned ingredients, the formulations of this invention may further include one or more accessory ingredient(s) selected from diluents, buffers, flavoring agents, disintegrants, surface active agents, thickeners, lubricants, preservatives (including antioxidants), and the like. The foregoing considerations apply also to the neublastin fusion proteins of the invention (e.g., neublastin-human serum albumin fusion proteins).

Accordingly, the present invention includes the provision of suitable fusion proteins for in vitro stabilization of a polymer-conjugated neublastin conjugate in solution, as a preferred illustrative application of the invention. The fusion proteins may be employed for example to increase the resistance to enzymatic degradation of the polymer-conjugated neublastin polypeptide and provides a means of improving shelf life, room temperature stability, and the like. It is understood that the foregoing considerations apply also to the neublastin-serum albumin fusion proteins (including the human neublastin-human serum albumin fusion proteins) of the invention.
 

Claim 1 of 68 Claims

1. An isolated polypeptide comprising an amino acid sequence at least 90% identical to amino acids 8-113 of SEQ ID NO:1, wherein the polypeptide includes at least one amino acid substitution selected from the group consisting of: (a) an amino acid other than arginine at the position corresponding to position 14 in SEQ ID NO:1; (b) an amino acid other than arginine at the position corresponding to position 39 in SEQ ID NO:1; (c) an amino acid other than arginine at the position corresponding to position 68 in SEQ ID NO:1; and (d) an amino acid other than asparagine at the position corresponding to position 95 in SEQ ID NO:1, wherein the polypeptide, when dimerized, binds to GFR.alpha.3.

 

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