Patent Application
20100009902
1. Field of the Invention
The present invention relates to conjugates formed between a biologically relevant substrate (e.g., a glycosylated or non-glycosylated peptide or lipid) and a saccharyl fragment that includes a modifying group (“modified fragment”). The substrate and modified fragment are linked through an enzymatically formed bond between the modified fragment and an acceptor moiety on the substrate.
2. Background
The administration of glycosylated and non-glycosylated therapeutic agents for engendering a particular physiological response is well known in the medicinal arts. For example, both purified and recombinant hGH are used for treating conditions and diseases due to hGH deficiency, e.g., dwarfism in children. Interferon has known antiviral activity and granulocyte colony stimulating factor stimulates the production of white blood cells.
A principal factor that has limited the use of therapeutic peptides is the difficulty inherent in engineering an expression system to express a peptide having the glycosylation pattern of the wild-type peptide. Improperly or incompletely glycosylated peptides can be immunogenic; in a patient, an immunogenic response to an administered peptide can neutralize the peptide and/or lead to the development of an allergic response in the patient. Other deficiencies of recombinantly produced glycopeptides include suboptimal potency and rapid clearance rates. The problems inherent in peptide therapeutics are recognized in the art, and various methods of eliminating the problems have been investigated.
Post-expression in vitro modification of peptides is an attractive strategy to remedy the deficiencies of methods that rely on controlling glycosylation by engineering expression systems; including both modification of glycan structures or introduction of glycans at novel sites. A comprehensive toolbox of recombinant eukaryotic glycosyltransferases is becoming available, making in vitro enzymatic synthesis of mammalian glycoconjugates with custom designed glycosylation patterns and glycosyl structures possible. See, for example, U.S. Pat. Nos. 5,876,980; 6,030,815; 5,728,554; 5,922,577; and WO/9831826; US2003180835; and WO 03/031464.
Enzyme-based syntheses have the advantages of regioselectivity and stereoselectivity. Moreover, enzymatic syntheses are performed using unprotected substrates. Two principal classes of enzymes are used in the synthesis of carbohydrates, glycosyltransferases (e.g., sialyltransferases, oligosaccharyltransferases, N-acetylglucosaminyltransferases), and glycosidases. The glycosidases are further classified as exoglycosidases (e.g., β-mannosidase, β-glucosidase), and endoglycosidases (e.g., Endo-A, Endo-M). Each of these classes of enzymes has been successfully used synthetically to prepare carbohydrates. For a general review, see, Crout et al., Curr. Opin. Chem. Biol. 2: 98-111 (1998).
Glycosyltransferases modify the oligosaccharide structures on glycopeptides. Glycosyltransferases are effective for producing specific products with good stereochemical and regiochemical control. Glycosyltransferases have been used to prepare oligosaccharides and to modify terminal N- and O-linked carbohydrate structures, particularly on glycopeptides produced in mammalian cells. For example, the terminal oligosaccharides of glycopeptides have been completely sialylated and/or fucosylated to provide more consistent sugar structures, which improves glycopeptide pharmacodynamics and a variety of other biological properties. For example, β-1,4-galactosyltransferase was used to synthesize lactosamine, an illustration of the utility of glycosyltransferases in the synthesis of carbohydrates (see, e.g., Wong et al., J. Org. Chem. 47: 5416-5418 (1982)). Moreover, numerous synthetic procedures have made use of a-sialyltransferases to transfer sialic acid from cytidine-5′-monophospho-N-acetylneuraminic acid to the 3-OH or 6-OH of galactose (see, e.g., Kevin et al., Chem. Eur. J. 2: 1359-1362 (1996)). Fucosyltransferases are used in synthetic pathways to transfer a fucose unit from guanosine-5′-diphosphofucose to a specific hydroxyl of a saccharide acceptor. For example, Ichikawa prepared sialyl Lewis-X by a method that involves the fucosylation of sialylated lactosamine with a cloned fucosyltransferase (Ichikawa et al., J. Am. Chem. Soc. 114: 9283-9298 (1992)). For a discussion of recent advances in glycoconjugate synthesis for therapeutic use see, Koeller et al., Nature Biotechnology 18: 835-841 (2000). See also, U.S. Pat. Nos. 5,876,980; 6,030,815; 5,728,554; 5,922,577; and WO/9831826.
Glycosidases can also be used to prepare saccharides. Glycosidases normally catalyze the hydrolysis of a glycosidic bond. Under appropriate conditions, however, they can be used to form this linkage. Most glycosidases used for carbohydrate synthesis are exoglycosidases; the glycosyl transfer occurs at the non-reducing terminus of the substrate. The glycosidase takes up a glycosyl donor in a glycosyl-enzyme intermediate that is either intercepted by water to give the hydrolysis product, or by an acceptor, to give a new glycoside or oligosaccharide. An exemplary pathway using an exoglycosidase is the synthesis of the core trisaccharide of all N-linked glycopeptides, including the difficult β-mannoside linkage, which was formed by the action of β-mannosidase (Singh et al., Chem. Commun. 993-994 (1996)).
In another exemplary application of the use of a glycosidase to form a glycosidic linkage, a mutant glycosidase was prepared in which the normal nucleophilic amino acid within the active site is changed to a non-nucleophilic amino acid. The mutant enzymes do not hydrolyze glycosidic linkages, but can still form them. The mutant glycosidases are used to prepare oligosaccharides using an a-glycosyl fluoride donor and a glycoside acceptor molecule (Withers et al., U.S. Pat. No. 5,716,812). Although the mutant glycosidases are useful for forming free oligosaccharides, it has yet to be demonstrated that such enzymes are capable of appending glycosyl donors onto glycosylated or non-glycosylated peptides, nor have these enzymes been used with unactivated glycosyl donors.
Although their use is less common than that of the exoglycosidases, endoglycosidases are also utilized to prepare carbohydrates. Methods based on the use of endoglycosidases have the advantage that an oligosaccharide, rather than a monosaccharide, is transferred. Oligosaccharide fragments have been added to substrates using endo-β-N-acetylglucosamines such as endo-F, endo-M (Wang et al., Tetrahedron Lett. 37: 1975-1978); and Haneda et al., Carbohydr. Res. 292: 61-70 (1996)).
In addition to their use in preparing carbohydrates, the enzymes discussed above are applied to the synthesis of glycopeptides. The synthesis of a homogeneous glycoform of ribonuclease B has been published (Witte K. et al., J. Am. Chem. Soc. 119: 2114-2118 (1997)). The high mannose core of ribonuclease B was cleaved by treating the glycopeptide with endoglycosidase H. The cleavage occurred specifically between the two core GlcNAc residues. The tetrasaccharide sialyl Lewis X was then enzymatically rebuilt on the remaining GlcNAc anchor site on the now homogeneous protein by the sequential use of β-1,4-galactosyltransferase, α-2,3-sialyltransferase and α-1,3-fucosyltransferase V. Each enzymatically catalyzed step proceeded in excellent yield.
Methods combining both chemical and enzymatic synthetic elements are also known. For example, Yamamoto and coworkers (Carbohydr. Res. 305: 415-422 (1998)) reported the chemoenzymatic synthesis of the glycopeptide, glycosylated Peptide T, using an endoglyosidase. The N-acetylglucosaminyl peptide was synthesized by purely chemical means. The peptide was subsequently enzymatically elaborated with the oligosaccharide of human transferrin glycopeptide. The saccharide portion was added to the peptide by treating it with an endo-β-N-acetylglucosaminidase. The resulting glycosylated peptide was highly stable and resistant to proteolysis when compared to the peptide T and N-acetylglucosaminyl peptide T.
The use of glycosyltransferases to modify peptide structure with reporter groups has been explored. For example, Brossmer et al. (U.S. Pat. No. 5,405,753) discloses the formation of a fluorescent-labeled cytidine monophosphate (“CMP”) derivative of sialic acid and the use of the fluorescent glycoside in an assay for sialyl transferase activity and for the fluorescent labeling of cell surfaces, glycoproteins and gangliosides. Gross et al. (Analyt. Biochem. 186: 127 (1990)) describe a similar assay. Bean et al. (U.S. Pat. No. 5,432,059) discloses an assay for glycosylation deficiency disorders utilizing reglycosylation of a deficiently glycosylated protein. The deficient protein is reglycosylated with a fluorescent-labeled CMP glycoside. Each of the fluorescent sialic acid derivatives is substituted with the fluorescent moiety at either the 9-position or at the amine that is normally acetylated in sialic acid. The methods using the fluorescent sialic acid derivatives are assays for the presence of glycosyltransferases or for non-glycosylated or improperly glycosylated glycoproteins. The assays are conducted on small amounts of enzyme or glycoprotein in a sample of biological origin. The enzymatic derivatization of a glycosylated or non-glycosylated peptide on a preparative or industrial scale using a modified sialic acid has not been disclosed or suggested.
Considerable effort has also been directed towards the modification of cell surfaces by altering glycosyl residues presented by those surfaces. For example, Fukuda and coworkers have developed a method for attaching glycosides of defined structure onto cell surfaces. The method exploits the relaxed substrate specificity of a fucosyltransferase that can transfer fucose and fucose analogs bearing diverse glycosyl substrates (Tsuboi et al., J. Biol. Chem. 271: 27213 (1996)).
The methods of modifying cell surfaces have not been applied in the absence of a cell to modify a glycosylated or non-glycosylated peptide. Moreover, the methods of cell surface modification are not utilized for the enzymatic incorporation preformed modified glycosyl donor moiety into a peptide. Moreover, none of the cell surface modification methods are practical for producing glycosyl-modified peptides on an industrial scale.
Enzymatic methods have also been used to activate glycosyl residues on a glycopeptide towards subsequent chemical elaboration. The glycosyl residues are typically activated using galactose oxidase, which converts a terminal galactose residue to the corresponding aldehyde. The aldehyde is subsequently coupled to an amine-containing modifying group. For example, Casares et al. (Nature Biotech. 19: 142 (2001)) have attached doxorubicin to the oxidized galactose residues of a recombinant MHCII-peptide chimera.
In addition to manipulating the structure of glycosyl groups on polypeptides, interest has developed in preparing glycopeptides that are modified with one or more non-saccharide modifying group, such as a water-soluble polymer. Poly(ethyleneglycol) (“PEG”) is an exemplary polymer that has been conjugated to polypeptides. The use of PEG to derivatize peptide therapeutics has been demonstrated to reduce the immunogenicity of the peptides. For example, U.S. Pat. No. 4,179,337 (Davis et al.) discloses non-immunogenic polypeptides, such as enzymes and peptide hormones coupled to polyethylene glycol (PEG) or polypropylene glycol. Between 10 and 100 moles of polymer are used per mole polypeptide. Although the in vivo clearance time of the conjugate is prolonged relative to that of the polypeptide, only about 15% of the physiological activity is maintained. Thus, the prolonged circulation half-life is counterbalanced by the dramatic reduction in peptide potency.
The loss of peptide activity is directly attributable to the non-selective nature of the chemistries utilized to conjugate the water-soluble polymer. The principal mode of attachment of PEG, and its derivatives, to peptides is a non-specific bonding through a peptide amino acid residue. For example, U.S. Pat. No. 4,088,538 discloses an enzymatically active polymer-enzyme conjugate of an enzyme covalently bound to PEG. Similarly, U.S. Pat. No. 4,496,689 discloses a covalently attached complex of α-1 proteinase inhibitor with a polymer such as PEG or methoxypoly(ethyleneglycol) (“(m-) PEG”). Abuchowski et al. (J. Biol. Chem. 252: 3578 (1977)) discloses the covalent attachment of (m-) PEG to an amine group of bovine serum albumin. U.S. Pat. No. 4,414,147 discloses a method of rendering interferon less hydrophobic by conjugating it to an anhydride of a dicarboxylic acid, such as poly(ethylene succinic anhydride). PCT WO 87/00056 discloses conjugation of PEG and poly(oxyethylated) polyols to such proteins as interferon-β, interleukin-2 and immunotoxins. EP 154,316 discloses and claims chemically modified lymphokines, such as IL-2 containing PEG bonded directly to at least one primary amino group of the lymphokine. U.S. Pat. No. 4,055,635 discloses pharmaceutical compositions of a water-soluble complex of a proteolytic enzyme linked covalently to a polymeric substance such as a polysaccharide.
Another mode of attaching PEG to peptides is through the non-specific oxidation of glycosyl residues on a glycopeptide. The oxidized sugar is utilized as a locus for attaching a PEG moiety to the peptide. For example M'Timkulu (WO 94/05332) discloses the use of an amino-PEG to add PEG to a glycoprotein. The glycosyl moieties are randomly oxidized to the corresponding aldehydes, which are subsequently coupled to the amino-PEG.
In each of the methods described above, poly(ethyleneglycol) is added in a random, non-specific manner to reactive residues on a peptide backbone. For the production of therapeutic peptides, it is clearly desirable to utilize a derivatization strategy that results in the formation of a specifically labeled, readily characterizable, essentially homogeneous product. A promising route to preparing specifically labeled peptides is through the use of enzymes, such as glycosyltransferases to append a modified sugar moiety onto a peptide.
Glycosyl residues have also been modified to bear ketone groups. For example, Mahal and co-workers (Science 276: 1125 (1997)) have prepared N-levulinoyl mannosamine (“ManLev”), which has a ketone functionality at the position normally occupied by the acetyl group in the natural substrate. Cells were treated with the ManLev, thereby incorporating a ketone group onto the cell surface. See, also Saxon et al., Science 287: 2007 (2000); Hang et al., J. Am. Chem. Soc. 123: 1242 (2001); Yarema et al., J. Biol. Chem. 273: 31168 (1998); and Charter et al., Glycobiology 10: 1049 (2000).
In addition to an industrially relevant method that utilizes the enzymatic conjugation to specifically conjugate a modified sugar to a peptide or glycopeptide, a method for controlling and manipulating the position of glycosylation on a glycopeptide would be highly desirable.
Carbohydrates are attached to glycopeptides in several ways of which N-linked to asparagine and mucin-type O-linked to serine and threonine are the most relevant for recombinant glycoprotein therapeutics. A determining factor for initiation of glycosylation of a protein is the primary sequence context, although clearly other factors including protein region and conformation play roles. N-linked glycosylation occurs at the consensus sequence NXS/T, where X can be any amino acid but proline.
O-linked glycosylation is initiated by a family of about 20 homologous enzymes termed UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferases). O-linked glycosylation does not appear to be ruled by one simple consensus sequence, although studies of the GalNAc-transferase enzymes that initiate O-linked glycosylation clearly supports the notion that their acceptor specificities are driven by primary sequence contexts. Each of these enzymes transfer a single monosaccharide GalNAc to serine and threonine residues, but they transfer to different peptide sequences although they show a large degree of overlap in functions. It is envisioned that the substrate specificity of each GalNAc-transferase is ruled primarily by a linear short acceptor consensus sequence.
Recently, a method of producing an ester linked carbohydrate-peptide conjugate was described by Davis (WO 03/014371, published Feb. 20, 2003). In this publication, a vinyl ester amino acid group was reacted with a carbohydrate acyl acceptor in the presence of an enzyme such as a protease (such as a serine protease), lipase, esterase or acylase. At this time, however, no other substrates, e.g., glycopeptides, glycolipids, are known to conjugate with carbohydrate acyl acceptors under these conditions.
The present invention answers the need for modified therapeutic species in which a modified glycosyl moiety is conjugated onto N- or O-linked glycosylation sites of the peptides and other bioactive species, e.g., glycolipids, sphingosines, ceramides, etc. The invention provides a route to new therapeutic conjugates and addresses the need for more stable and therapeutically effective species. Moreover, despite the efforts directed toward the enzymatic elaboration of saccharide structures, there remains still a need for alternative industrially practical methods for the modification of therapeutic agents, e.g., peptides, glycopeptides and lipids with modifying groups such as water-soluble polymers, therapeutic moieties, biomolecules and the like. Of particular interest are methods in which the modified peptide has improved properties, which enhance its use as a therapeutic or diagnostic agent. The present invention fulfills these and other needs.
Glycotherapeutics (e.g., glycopeptides and glycolipids) present a challenging target for recombinant production of therapeutics. For example, specific carbohydrate moieties are often indispensable for the function and favorable pharmacokinetic properties of glycopeptide therapeutics; however, many of the most robust expression systems produce glycopeptides with non-human glycosylation patterns. Incorrect glycosylation can produce a peptide that is inactive, aggregated, antigenic and/or has unfavorable pharmacokinetics. Accordingly, considerable efforts are expended to develop recombinant expression cell systems capable of producing glycoproteins with biologically appropriate carbohydrate structures. This approach is hampered by numerous shortcomings, including cost, and heterogeneity and limitations in glycan structures.
Post-expression, in vitro glyco-modification of glycotherapeutics, e.g., glycopeptides, is an attractive strategy to remedy the deficiencies of methods that rely on controlling glycosylation by engineering expression systems; including both modification of glycan structures or introduction of glycans at novel sites. A comprehensive toolbox of recombinant eukaryotic glycosyltransferases is becoming available, making in vitro enzymatic synthesis of glycoconjugates with custom designed glycosylation patterns and glycosyl structures possible. See, for example, U.S. Pat. Nos. 5,876,980; 6,030,815; 5,728,554; and 5,922,577; and WO 98/31826; US03/180835; and WO 03/031464.
In vitro glycosylation offers a number of advantages compared to recombinant expression of glycoproteins of which custom design and higher degree of homogeneity of the glycosyl moiety are examples. Moreover, combining bacterial expression of glycotherapeutics with in vitro modification (or placement) of the glycosyl residue offers numerous advantages over traditional recombinant expression technology including reduced potential exposure to adventitious agents, increased homogeneity of product, and cost reduction.
Ideally, conjugates of therapeutic species, such as peptides and lipids, are obtained using methods that provide the conjugates in a reproducible and predictable manner. Moreover, in forming the conjugates it is generally preferred that the site of conjugation between the therapeutic species and the modifying group is selected such that its modification does not adversely affect advantageous properties of the therapeutic species, e.g. activity, specificity, low antigenicity, low toxicity, etc.
The present invention provides a method of forming conjugates between a glycosyl residue, amino acid or aglycone moiety of a selected substrate (e.g., (glyco)peptide, (glyco)lipid, etc.) and a modifying group, such as a water-soluble- or water-insoluble-polymer, a therapeutic moiety or a diagnostic agent. The invention exploits the recognition that saccharides, e.g., sialic acid, can be oxidized in a predictable and reproducible fashion, converting a primary or secondary hydroxyl moiety to an aldehyde or a ketone. The carbonyl moiety is readily modified with an amine-containing modifying group, affording a Schiff base, which is reduced to the corresponding amine modified saccharyl fragment. The fragment is recognized as a substrate by one or more enzyme capable of transferring a glycosyl moiety onto a substrate.
In an exemplary embodiment, the modified saccharyl fragment is a substrate for an enzyme that transfers a glycosyl donor moiety to a glycosyl acceptor. In an exemplary embodiment, the enzyme is a transferase, e.g., a sialyltransferase, which utilizes the modified fragment as a saccharyl donor in an enzymatically-mediated glycosylation reaction. In another embodiment, the enzyme is a mutant of a degradative enzyme, such as an exo- or endoglycosidase, amidase, etc.
In another embodiment, the modified saccharyl fragment is coupled to an intact saccharide residue. For example, coupling Sia*-(modifying group) to galactose affords, Gal-Sia*-(modifying group), which serves as a glycosyl donor that is added to a substrate, e.g, peptide, lipid, aglycone, etc.
The present invention is exemplified by reference to modified saccharyl fragments in which the side chain of a sialic acid is oxidized and the resulting carbonyl moiety (aldehyde) is converted to an amine by reductive amination with ammonia or an amine-containing modifying group. Those of skill will appreciate that saccharides, as a group, possess a rich oxidation chemistry that is readily exploited in variations on the exemplification of the invention presented herein.
In an exemplary aspect, the present invention provides a conjugate of a bioactive species, e.g., a peptide, nucleotide, activating moiety, carbohydrate, lipid (e.g., ceramide or sphingosine) that includes a subunit according to Formula I:
In Formula I, the symbol X1 represents substituted or unsubstituted alkyl, O or NR8. R8 is a member selected from H, OH, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. Appropriate R1 groups are selected from OR9, NR9R10, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. The symbols R9 and R10 independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl and C(O)R11. R11 is a group such as substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl and substituted or unsubstituted heterocycloalkyl.
The symbol R2 is a member selected from an is a member selected from a nucleotide, an activating moiety, an amino acid residue of a peptide, a carbohydrate moiety attached to an amino acid residue of a peptide, a carbohydrate moiety attached to an amino acid residue of a peptide through a linker and a carbohydrate moiety attached to an amino acid residue of a peptide through a linker comprising at least a second carbohydrate moiety. Exemplary linkers include one or more additional carbohydrate moieties in addition to that of R2. R3 is a member selected from H, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. The symbols R4 and R3′ independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, OH, OR4′ and NHC(O)R12. R4′ is a member selected from H, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. R12 is a member selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heterocycloalkyl and NR13R14, in which R13 and R14 are members independently selected from H, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl.
Y is the residue of the sialic acid side chain remaining following oxidation to a carbonyl and subsequent reaction of the carbonyl moiety with a nucleophilic group, alternatively followed by additional modifications. Exemplary groups for Y include CH2, CH(OH)CH2, CH(OH)CH(OH)CH2 when the oxidation leads to formation of an aldehyde that is subsequently reductively aminated. When the aldehyde is converted to an imine species or is reacted with a phosphorus ylide, Y is typically CH, CH(OH)CH or CH(OH)CH(OH)CH. When the aldehyde is reacted with a Grignard or lithium reagent, exemplary Y groups include CH(OH), CH(OH)CH(OH), CH(OH)CH(OH)CH(OH) or an elimination product thereof, e.g., dehydration product.
The symbol Y2 represents groups formed by addition to the carbonyl moiety of the fragment. Y2 includes at least one modifying group e.g., biomolecule, therapeutic moiety, diagnostic moiety, and a polymeric modifying group, as exemplified by the term R6a. Exemplary identities for Y2 include substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl (e.g., formed by Wittig, Grignard or other appropriate chemistries), R6, and nitrogen-containing species, e.g.,
In an exemplary embodiment, Y2 is a member selected from substituted alkyl, substituted or unsubstituted heteroalkyl, R6, and nitrogen-containing species. R6 and R7 are independently H, C(O)R6b or -La-R6b wherein R6b is H or R6a and La is selected from a bond and a linker group.
When Y2 is substituted or unsubstituted alkyl, e.g., an alkene species formed by a Wittig reaction, or saturated species formed by Grignard or lithium chemistries, Y2 includes at least one modifying group (water-soluble or -insoluble polymer) as exemplified by the term R6a.
As discussed herein, R6a can be a polymeric modifying group. Preferred polymeric modifying groups include PEG. The PEG of use in the conjugates of the invention can be linear or branched. An exemplary precursor of use to form the branched PEG containing peptide conjugates according to this embodiment of the invention has the formula:
The branched polymer species according to this formula are essentially pure polymeric modifying groups. X3′ is a moiety that includes an ionizable (e.g., OH, COOH, H2PO4, HSO3, NH2, and salts thereof, etc.) or other reactive functional group, e.g., infra. C is carbon. X5, R16 and R17 are independently selected from non-reactive groups (e.g., H, unsubstituted alkyl, unsubstituted heteroalkyl) and polymeric arms (e.g., PEG). X2 and X4 are linkage fragments that are preferably essentially non-reactive under physiological conditions and that may be the same or different. An exemplary linker includes neither aromatic nor ester moieties. Alternatively, these linkages can include one or more moiety that is designed to degrade under physiologically relevant conditions, e.g., esters, disulfides, etc. X2 and X4 join polymeric arms R16 and R17 to C. When X3′ is reacted with a reactive functional group of complementary reactivity on a linker, sugar or linker-sugar cassette, X3′ is converted to a component of linkage fragment X3.
In an exemplary embodiment, the polymeric modifying group is bound to the glycosyl linking group, through a linker, La, in which case the residues R6 and R7 are independently as shown below:
R6a is the polymeric modifying group and La is selected from a bond and a linking group. The index w represents an integer selected from 1-6, preferably 1-3 and more preferably 1-2. Exemplary linking groups include substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl moieties. An exemplary component of the linker group is an acyl moiety. Another exemplary linking group is an amino acid (e.g., cysteine, serine, lysine, and short oligopeptides, e.g., Lys-Lys, Lys-Lys-Lys, Cys-Lys, Ser-Lys, etc.).
When La is a bond, it is formed by reaction of a reactive functional group on a precursor of R6a and a reactive functional group of complementary reactivity on a precursor of the glycosyl linking group. When La is a non-zero order linking group, L can be in place on the glycosyl moiety prior to reaction with the R6a precursor. Alternatively, the precursors of R6a and La can be incorporated into a preformed cassette that is subsequently attached to the glycosyl moiety. As set forth herein, the selection and preparation of precursors with appropriate reactive functional groups is within the ability of those skilled in the art. Moreover, coupling of the precursors proceeds by chemistry that is well understood in the art.
In another aspect, the invention provides an activated glycosyl linking group that is of use in the methods of the invention. In an exemplary embodiment, according to this aspect, the glycosyl linking group has a structure according to Formula I in which R2 is a nucleotide, forming a nucleotide sugar in which the sugar moiety is, or includes, the saccharyl fragment. R2 can also be a leaving group (activating group), such as a halogen, sulfonate ester and the like.
In a third aspect, the invention provides a peptide or lipid conjugate having a population of water-soluble polymer moieties covalently bound thereto through a glycosyl linking group that includes a moiety according to Formula I. In the conjugate of the invention, essentially each member of the population is bound via a glycosyl linking group, that includes a subunit according to Formula I, to an amino acid or glycosyl residue of the peptide, and each amino acid or glycosyl residue to which the linking group is bound has the same structure.
In a fourth aspect, the invention provides a method of forming a covalent conjugate between a polymer, e.g., water-soluble polymer, and saccharyl acceptor that is a glycosylated-peptide or -lipid, or a non-glycosylated-peptide or -lipid. The polymer is conjugated to the acceptor via a glycosyl linking group that includes a moiety according to Formula I. The glycosyl linking group is interposed between, and covalently linked either directly or indirectly to both the acceptor and the polymer. The method includes contacting the acceptor with a mixture containing a modified saccharyl fragment, generally activated as the nucleotide derivative, and an enzyme for which the modified saccharyl fragment is a substrate. The mixture also includes an enzyme that transfers a saccharyl residue, for which the modified saccharyl fragment is a substrate. The reaction is conducted under conditions appropriate to form the conjugate. See, for example WO03/031464 and related U.S. and PCT applications.
In a fifth aspect, the invention provides a conjugate analogous to those described above, in which the modified saccharyl fragment is derivatized with a therapeutic or diagnostic moiety. In an exemplary embodiment, the modifying group is a biomolecule, which can be a therapeutic or diagnostic agent.
In a further aspect, the present invention provides a composition for forming a conjugate between a peptide or lipid and a modified saccharyl fragment. The composition generally includes an activated analogue of the saccharyl fragment set forth in Formula I, an enzyme for which the activated glycosyl linking group is a substrate, and a (glyco)peptide or (glyco)lipid acceptor substrate. The glycosyl linking group has covalently attached thereto a member selected from water-soluble polymers, therapeutic moieties and biomolecules.
Also provided is a pharmaceutical composition. The composition includes a pharmaceutically acceptable carrier and a conjugate of the invention in admixture with a pharmaceutically acceptable carrier.
Other objects and advantages of the invention will be apparent to those of skill in the art from the detailed description that follows.
Branched or un-branched PEG, poly(ethyleneglycol), including m-PEG, methoxy-poly(ethylene glycol); branched or unbranched PPG, poly(propyleneglycol); m-PPG, methoxy-poly(propylene glycol); Fuc, fucosyl; Gal, galactosyl; GalNAc, N-acetylgalactosaminyl; Glc, glucosyl; GlcNAc, N-acetylglucosaminyl; Man, mannosyl; ManAc, mannosaminyl acetate; Sia, sialic acid; NeuAc, N-acetylneuraminyl; and SA*-Y, sialic acid fragment, wherein SA* is the glycosidic core or ring structure of the molecule and Y is part of the modified sialic acid side chain.
Unless defined otherwise, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Generally, the nomenclature used herein and the laboratory procedures in cell culture, molecular genetics, organic chemistry and nucleic acid chemistry and hybridization are those well known and commonly employed in the art. Standard techniques are used for nucleic acid and peptide synthesis. The techniques and procedures are generally performed according to conventional methods in the art and various general references (see generally, Sambrook et al. M
The term “alkyl,” by itself or as part of another substituent, means, unless otherwise stated, a straight or branched chain, or cyclic hydrocarbon radical, or combination thereof, which may be fully saturated, mono- or polyunsaturated and can include di- and multivalent radicals, having the number of carbon atoms designated (i.e. C1-C10 means one to ten carbons). Examples of saturated hydrocarbon radicals include, but are not limited to, groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, cyclohexyl, (cyclohexyl)methyl, cyclopropylmethyl, homologs and isomers of, for example, n-pentyl, n-hexyl, n-heptyl, n-octyl, and the like. An unsaturated alkyl group is one having one or more double bonds or triple bonds. Examples of unsaturated alkyl groups include, but are not limited to, vinyl, 2-propenyl, crotyl, 2-isopentenyl, 2-(butadienyl), 2,4-pentadienyl, 3-(1,4-pentadienyl), ethynyl, 1- and 3-propynyl, 3-butynyl, and the higher homologs and isomers. The term “alkyl,” unless otherwise noted, is also meant to include those derivatives of alkyl defined in more detail below, such as “heteroalkyl.” Alkyl groups, which are limited to hydrocarbon groups are termed “homoalkyl”.
The term “alkylene” by itself or as part of another substituent means a divalent radical derived from an alkane, as exemplified, but not limited, by —CH2CH2CH2CH2—, and further includes those groups described below as “heteroalkylene.” Typically, an alkyl (or alkylene) group will have from 1 to 24 carbon atoms, with those groups having 10 or fewer carbon atoms being preferred in the present invention. A “lower alkyl” or “lower alkylene” is a shorter chain alkyl or alkylene group, generally having eight or fewer carbon atoms.
The terms “alkoxy,” “alkylamino” and “alkylthio” (or thioalkoxy) are used in their conventional sense, and refer to those alkyl groups attached to the remainder of the molecule via an oxygen atom, an amino group, or a sulfur atom, respectively.
The term “heteroalkyl,” by itself or in combination with another term, means, unless otherwise stated, a stable straight or branched chain, or cyclic hydrocarbon radical, or combinations thereof, consisting of the stated number of carbon atoms and at least one heteroatom selected from the group consisting of O, N, Si and S, and wherein the nitrogen and sulfur atoms may optionally be oxidized and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) O, N and S and Si may be placed at any interior position of the heteroalkyl group or at the position at which the alkyl group is attached to the remainder of the molecule. Examples include, but are not limited to, —CH2—CH2—O—CH3, —CH2—CH2—NH—CH3, —CH2—CH2—N(CH3)—CH3, —CH2—S—CH2—CH3, —CH2—CH2, —S(O)—CH3, —CH2—CH2—S(O)2—CH3, —CH═CH—O—CH3, —Si(CH3)3, —CH2—CH═N—OCH3, and —CH═CH—N(CH3)—CH3. Up to two heteroatoms may be consecutive, such as, for example, —CH2—NH—OCH3 and —CH2—O—Si(CH3)3. Similarly, the term “heteroalkylene” by itself or as part of another substituent means a divalent radical derived from heteroalkyl, as exemplified, but not limited by, —CH2—CH2—S—CH2—CH2— and —CH2—S—CH2—CH2—NH—CH2—. For heteroalkylene groups, heteroatoms can also occupy either or both of the chain termini (e.g., alkyleneoxy, alkylenedioxy, alkyleneamino, alkylenediamino, and the like). Still further, for alkylene and heteroalkylene linking groups, no orientation of the linking group is implied by the direction in which the formula of the linking group is written. For example, the formula —C(O)2R′— represents both —C(O)2R′— and —R′C(O)2—.
In general, an “acyl substituent” is also selected from the group set forth above. As used herein, the term “acyl subsituent” refers to groups attached to, and fulfilling the valence of a carbonyl carbon that is either directly or indirectly attached to the polycyclic nucleus of the compounds of the present invention.
The terms “cycloalkyl” and “heterocycloalkyl”, by themselves or in combination with other terms, represent, unless otherwise stated, cyclic versions of “alkyl” and “heteroalkyl”, respectively. Additionally, for heterocycloalkyl, a heteroatom can occupy the position at which the heterocycle is attached to the remainder of the molecule. Examples of cycloalkyl include, but are not limited to, cyclopentyl, cyclohexyl, 1-cyclohexenyl, 3-cyclohexenyl, cycloheptyl, and the like. Examples of heterocycloalkyl include, but are not limited to, 1-(1,2,5,6-tetrahydropyridyl), 1-piperidinyl, 2-piperidinyl, 3-piperidinyl, 4-morpholinyl, 3-morpholinyl, tetrahydrofuran-2-yl, tetrahydrofuran-3-yl, tetrahydrothien-2-yl, tetrahydrothien-3-yl, 1-piperazinyl, 2-piperazinyl, and the like.
The terms “halo” or “halogen,” by themselves or as part of another substituent, mean, unless otherwise stated, a fluorine, chlorine, bromine, or iodine atom. Additionally, terms such as “haloalkyl,” are meant to include monohaloalkyl and polyhaloalkyl. For example, the term “halo(C1-C4)alkyl” is mean to include, but not be limited to, trifluoromethyl, 2,2,2-trifluoroethyl, 4-chlorobutyl, 3-bromopropyl, and the like.
The term “aryl” means, unless otherwise stated, a polyunsaturated, aromatic, hydrocarbon substituent which can be a single ring or multiple rings (preferably from 1 to 3 rings) which are fused together or linked covalently. The term “heteroaryl” refers to aryl groups (or rings) that contain from one to four heteroatoms selected from N, O, and S, wherein the nitrogen and sulfur atoms are optionally oxidized, and the nitrogen atom(s) are optionally quaternized. A heteroaryl group can be attached to the remainder of the molecule through a heteroatom. Non-limiting examples of aryl and heteroaryl groups include phenyl, 1-naphthyl, 2-naphthyl, 4-biphenyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 3-pyrazolyl, 2-imidazolyl, 4-imidazolyl, pyrazinyl, 2-oxazolyl, 4-oxazolyl, 2-phenyl-4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidyl, 4-pyrimidyl, 5-benzothiazolyl, purinyl, 2-benzimidazolyl, 5-indolyl, 1-isoquinolyl, 5-isoquinolyl, 2-quinoxalinyl, 5-quinoxalinyl, 3-quinolyl, and 6-quinolyl. Substituents for each of the above noted aryl and heteroaryl ring systems are selected from the group of acceptable substituents described below.
For brevity, the term “aryl” when used in combination with other terms (e.g., aryloxy, arylthioxy, arylalkyl) includes both aryl and heteroaryl rings as defined above. Thus, the term “arylalkyl” is meant to include those radicals in which an aryl group is attached to an alkyl group (e.g., benzyl, phenethyl, pyridylmethyl and the like) including those alkyl groups in which a carbon atom (e.g., a methylene group) has been replaced by, for example, an oxygen atom (e.g., phenoxymethyl, 2-pyridyloxymethyl, 3-(1-naphthyloxy)propyl, and the like).
Each of the above terms (e.g., “alkyl,” “heteroalkyl,” “aryl” and “heteroaryl”) include both substituted and unsubstituted forms of the indicated radical. Preferred substituents for each type of radical are provided below.
Substituents for the alkyl, and heteroalkyl radicals (including those groups often referred to as alkylene, alkenyl, heteroalkylene, heteroalkenyl, alkynyl, cycloalkyl, heterocycloalkyl, cycloalkenyl, and heterocycloalkenyl) are generally referred to as “alkyl substituents” and “heteroakyl substituents,” respectively, and they can be one or more of a variety of groups selected from, but not limited to: —OR′, ═O, ═NR′, ═—OR′, NR′R″, —SR′, -halogen, —SiR′R″R′″, —OC(O)R′, —C(O)R′, —CO2R′, —CONR′R″, —OC(O)NR′R″, —NR″C(O)R′, —NR′—C(O)NR″R′″, —NR″C(O)2R′, —NR—C(NR′R″R′″)═NR″″, —NR—C(N′R″)═NR′″, —S(O)R′, —S(O)2R′, —S(O)2NR′R″, —NRSO2R′, —CN and —NO2 in a number ranging from zero to (2m′+1), where m′ is the total number of carbon atoms in such radical. R′, R″, R′″ and R″″ each preferably independently refer to hydrogen, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, e.g., aryl substituted with 1-3 halogens, substituted or unsubstituted alkyl, alkoxy or thioalkoxy groups, or arylalkyl groups. When a compound of the invention includes more than one R group, for example, each of the R groups is independently selected as are each R′, R″, R′″ and R″″ groups when more than one of these groups is present. When R′ and R″ are attached to the same nitrogen atom, they can be combined with the nitrogen atom to form a 5-, 6-, or 7-membered ring. For example, —NR′R″ is meant to include, but not be limited to, 1-pyrrolidinyl and 4-morpholinyl. From the above discussion of substituents, one of skill in the art will understand that the term “alkyl” is meant to include groups including carbon atoms bound to groups other than hydrogen groups, such as haloalkyl (e.g., —CF3 and —CH2CF3) and acyl (e.g., —C(O)CH3, —C(O)CF3, —C(O)CH2OCH3, and the like).
Similar to the substituents described for the alkyl radical, the aryl substituents and heteroaryl substituents are generally referred to as “aryl substituents” and “heteroaryl substituents,” respectively and are varied and selected from, for example: halogen, —OR′, ═O, ═NR′, ═N—OR′, —NR′R″, —SR′, -halogen, —SiR′R″R′″, —OC(O)R′, —C(O)R′, —CO2R′, —CONR′R″, —OC(O)NR′R″, —NR″C(O)R′, —NR′—C(O)NR″R′″, —NR″C(O)2R′, —NR—C(NR′R″)═NR′″, —S(O)R′, —S(O)2R′, —S(O)2NR′R″, —NRSO2R′, —CN and —NO2, —R′, —N3, —CH(Ph)2, fluoro(C1-C4)alkoxy, and fluoro(C1-C4)alkyl, in a number ranging from zero to the total number of open valences on the aromatic ring system; and where R′, R″, R′″ and R″″ are preferably independently selected from hydrogen, (C1-C8)alkyl and heteroalkyl, unsubstituted aryl and heteroaryl, (unsubstituted aryl)-(C1-C4)alkyl, and (unsubstituted aryl)oxy-(C1-C4)alkyl. When a compound of the invention includes more than one R group, for example, each of the R groups is independently selected as are each R′, R″, R′″ and R″″ groups when more than one of these groups is present.
Two of the aryl substituents on adjacent atoms of the aryl or heteroaryl ring may optionally be replaced with a substituent of the formula -T-C(O)—(CRR′)q—U—, wherein T and U are independently —NR—, —O—, —CRR′— or a single bond, and q is an integer of from 0 to 3. Alternatively, two of the substituents on adjacent atoms of the aryl or heteroaryl ring may optionally be replaced with a substituent of the formula -A-(CH2)r—B—, wherein A and B are independently —CRR′—, —O—, —NR—, —S—, —S(O)—, —S(O)2—, —S(O)2NR′— or a single bond, and r is an integer of from 1 to 4. One of the single bonds of the new ring so formed may optionally be replaced with a double bond. Alternatively, two of the substituents on adjacent atoms of the aryl or heteroaryl ring may optionally be replaced with a substituent of the formula —(CRR′)s—X—(CR″R′″)d—, where s and d are independently integers of from 0 to 3, and X is —O—, —NR′—, —S—, —S(O)—, —S(O)2—, or —S(O)2NR′—. The substituents R, R′, R″ and R′″ are preferably independently selected from hydrogen or substituted or unsubstituted (C1-C6)alkyl.
As used herein, the term “heteroatom” includes oxygen (O), nitrogen (N), sulfur (S) and silicon (Si).
The term “nucleic acid” or “polynucleotide” refers to deoxyribonucleic acids (DNA) or ribonucleic acids (RNA) and polymers thereof in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions), alleles, orthologs, SNPs, and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al., Nucleic Acid Res. 19:5081 (1991); Ohtsuka et al., J. Biol. Chem. 260:2605-2608 (1985); and Rossolini et al., Mol. Cell. Probes 8:91-98 (1994)). The term nucleic acid is used interchangeably with gene, cDNA, and mRNA encoded by a gene.
The term “gene” means the segment of DNA involved in producing a polypeptide chain. It may include regions preceding and following the coding region (leader and trailer) as well as intervening sequences (introns) between individual coding segments (exons).
The term “amino acid” refers to naturally occurring and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function in a manner similar to the naturally occurring amino acids. Naturally occurring amino acids are those encoded by the genetic code, as well as those amino acids that are later modified, e.g., hydroxyproline, γ-carboxyglutamate, and O-phosphoserine. Amino acid analogs refers to compounds that have the same basic chemical structure as a naturally occurring amino acid, i.e., an α carbon that is bound to a hydrogen, a carboxyl group, an amino group, and an R group, e.g., homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. Such analogs have modified R groups (e.g., norleucine) or modified peptide backbones, but retain the same basic chemical structure as a naturally occurring amino acid. “Amino acid mimetics” refers to chemical compounds that have a structure that is different from the general chemical structure of an amino acid, but functioning in a manner similar to a naturally occurring amino acid.
Amino acids may be referred to herein by either the commonly known three letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Nucleotides, likewise, may be referred to by their commonly accepted single-letter codes.
“Conservatively modified variants” applies to both amino acid and nucleic acid sequences. With respect to particular nucleic acid sequences, “conservatively modified variants” refers to those nucleic acids that encode identical or essentially identical amino acid sequences, or where the nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given protein. For instance, the codons GCA, GCC, GCG and GCU all encode the amino acid alanine. Thus, at every position where an alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are “silent variations,” which are one species of conservatively modified variations. Every nucleic acid sequence herein that encodes a polypeptide also describes every possible silent variation of the nucleic acid. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine, and TGG, which is ordinarily the only codon for tryptophan) can be modified to yield a functionally identical molecule. Accordingly, each silent variation of a nucleic acid that encodes a polypeptide is implicit in each described sequence.
As to amino acid sequences, one of skill will recognize that individual substitutions, deletions or additions to a nucleic acid, peptide, polypeptide, or protein sequence which alters, adds or deletes a single amino acid or a small percentage of amino acids in the encoded sequence is a “conservatively modified variant” where the alteration results in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. Such conservatively modified variants are in addition to and do not exclude polymorphic variants, interspecies homologs, and alleles of the invention.
As to amino acid sequences, one of skill will recognize that individual substitutions, deletions or additions to a nucleic acid, peptide, polypeptide, or protein sequence which alters, adds or deletes a single amino acid or a small percentage of amino acids in the encoded sequence is a “conservatively modified variant” where the alteration results in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. Such conservatively modified variants are in addition to and do not exclude polymorphic variants, interspecies homologs, and alleles of the invention.
The following eight groups each contain amino acids that are conservative substitutions for one another:
Amino acids may be referred to herein by either the common three-letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Nucleotides, likewise, may be referred to by their commonly accepted single-letter codes.
The term “mutating” or “mutation,” as used in the context of altering the structure or enzymatic activity of a wild-type enzyme, refers to the deletion, insertion, or substitution of any nucleotide or amino acid residue, by chemical, enzymatic, or any other means, in a polynucleotide sequence encoding a that enzyme or the amino acid sequence of a wild-type enzyme, respectively, such that the amino acid sequence of the resulting enzyme is altered at one or more amino acid residues. The site for such an activity-altering mutation may be located anywhere in the enzyme, but is preferably within the active site of the enzyme.
“Peptide” refers to a polymer in which the monomers are amino acids and are joined together through amide bonds, alternatively referred to as a polypeptide. Additionally, unnatural amino acids, for example, β-alanine, phenylglycine and homoarginine are also included. Amino acids that are not gene-encoded may also be used in the present invention. Furthermore, amino acids that have been modified to include reactive groups, glycosylation sites, polymers, therapeutic moieties, biomolecules and the like may also be used in the invention. All of the amino acids used in the present invention may be either the
The term “peptide conjugate,” refers to species of the invention in which a peptide is conjugated with an acyl-containing group that is attached to the peptide through a sugar residue.
The term “sialic acid” refers to any member of a family of nine-carbon carboxylated sugars. The most common member of the sialic acid family is N-acetyl-neuraminic acid (2-keto-5-acetamido-3,5-dideoxy-D-glycero-D-galactononulopyranos-1-onic acid (often abbreviated as Neu5Ac, NeuAc, or NANA). A second member of the family is N-glycolyl-neuraminic acid (Neu5Gc or NeuGc), in which the N-acetyl group of NeuAc is hydroxylated. A third sialic acid family member is 2-keto-3-deoxy-nonulosonic acid (KDN) (Nadano et al. (1986) J. Biol. Chem. 261: 11550-11557; Kanamori et al., J. Biol. Chem. 265: 21811-21819 (1990)). Also included are 9-substituted sialic acids such as a 9-O—C1-C6 acyl-Neu5Ac like 9-O-lactyl-Neu5Ac or 9-O-acetyl-Neu5Ac, 9-deoxy-9-fluoro-Neu5Ac and 9-azido-9-deoxy-Neu5Ac. For review of the sialic acid family, see, e.g., Varki, Glycobiology 2: 25-40 (1992); Sialic Acids: Chemistry, Metabolism and Function, R. Schauer, Ed. (Springer-Verlag, New York (1992)). The synthesis and use of sialic acid compounds in a sialylation procedure is disclosed in international application WO 92/16640, published Oct. 1, 1992.
As used herein, the term “modified saccharyl fragment,” refers to a fragment of a naturally- or non-naturally-occurring carbohydrate that has been modified, typically oxidatively to create a locus for attaching a modifying group. In an exemplary embodiment, the saccharyl fragment is a sialic acid fragment in which the side chain is altered by oxidative degradation. The oxidation produces a carbonyl moiety that is subsequently reductively aminated with an amine analogue of the modifying group. In another exemplary embodiment, the ring structure of the saccharide is linearized by reductive conversion to an alditol (e.g., mannose to mannitol) and derivatized, e.g., at one or more of the primary hydroxyl moieties. Useful, modifying groups include, but are not limited to, water-soluble polymers, water-insoluble polymers, therapeutic moieties, diagnostic moieties, biomolecules and the like.
The term “water-soluble” refers to moieties that have a detectable degree of solubility in water. Methods to detect and/or quantify water solubility are well known in the art. Exemplary water-soluble polymers include peptides, saccharides, poly(ethers), poly(amines), poly(carboxylic acids) and the like. Peptides can have mixed sequences of be composed of a single amino acid, e.g., poly(lysine), poly(aspartic acid), and poly(glutamic acid). An exemplary polysaccharide is poly(sialic acid). An exemplary poly(ether) is poly(ethylene glycol), e.g., m-PEG. Poly(ethylene imine) is an exemplary polyamine, and poly(acrylic) acid is a representative poly(carboxylic acid).
The polymer backbone of the water-soluble polymer can be poly(ethylene glycol) (PEG), e.g., m-PEG. However, it should be understood that other related polymers are also suitable for use in the practice of this invention and that the use of the term PEG or poly(ethylene glycol) is intended to be inclusive and not exclusive in this respect. The term PEG includes poly(ethylene glycol) in any of its forms, including alkoxy PEG, alkyl PEG (e.g., mPEG), difunctional PEG, multiarmed PEG, forked PEG, branched PEG, pendent PEG (i.e. PEG or related polymers having one or more functional groups pendent to the polymer backbone), or PEG with degradable linkages therein.
The polymer backbone can be linear or branched. Branched polymer backbones are generally known in the art. Typically, a branched polymer has a central branch core moiety and a plurality of linear polymer chains linked to the central branch core. PEG is commonly used in branched forms that can be prepared by addition of ethylene oxide to various polyols, such as glycerol, pentaerythritol and sorbitol. The central branch moiety can also be derived from several amino acids, such as lysine. The branched poly(ethylene glycol) can be represented in general form as R(-PEG-OH)m in which R represents the core moiety, such as glycerol, pentaerythritol, amino acid (e.g., cysteine, serine, di-lysine, tri-lysine, etc.) and m represents the number of arms. Multi-armed PEG molecules, such as those described in U.S. Pat. Nos. 5,932,462; 5,643,575; European Patent Application 0473,084 A2; WO 96/41813 (and its priority documents), can also be used as the polymer backbone.
Many other polymers are also suitable for the invention. Polymer backbones that are non-peptidic and water-soluble, with from 2 to about 300 termini, are particularly useful in the invention. Examples of suitable polymers include, but are not limited to, other poly(alkylene glycols), such as poly(propylene glycol) (“PPG”), copolymers of ethylene glycol and propylene glycol and the like, poly(oxyethylated polyol), poly(olefinic alcohol), poly(vinylpyrrolidone), poly(hydroxypropylmethacrylamide), poly(α-hydroxy acid), poly(vinyl alcohol), polyphosphazene, polyoxazoline, poly(N-acryloylmorpholine), such as described in U.S. Pat. No. 5,629,384, which is incorporated by reference herein in its entirety, and copolymers, terpolymers, and mixtures thereof. Although the molecular weight of each chain of the polymer backbone can vary, it is typically in the range of from about 100 Da to about 100,000 Da, often from about 6,000 Da to about 80,000 Da.
The terms “large-scale” and “industrial-scale” are used interchangeably and refer to a reaction cycle that produces at least about 250 mg, preferably at least about 500 mg, and more preferably at least about 1 gram of glycoconjugate at the completion of a single reaction cycle.
The term, “glycosyl linking group,” as used herein refers to a glycosyl residue that is a fragment of a parent saccharide, generally prepared by oxidation of one or more primary or secondary hydroxyl moieties on the parent saccharide. An exemplary glycosyl linking group is set forth in Formula I, below. As shown in Formula I, the glycosyl linking group covalently joins the modifying group (e.g., PEG moiety, therapeutic moiety, biomolecule) to the molecule to which it is attached. In the methods of the invention, the “glycosyl linking group” is formed by the covalent modification, via an enzymatic glycosylation reaction linking the agent to an amino acid and/or glycosyl residue on the peptide. The glycosyl linking group can be a saccharide-derived structure that is degraded or degraded and modified prior to the addition of the modifying group (e.g., oxidation→Schiff base formation→reduction). Alternatively, a portion of the glycosyl linking group may be intact. For example, when the glycosyl linking group is Gal-SA* (SA* is the saccharyl fragment), with Gal attached to a peptide or lipid, the Gal can be intact. The glycosyl linking groups of the invention may be derived from a saccharide by addition of glycosyl unit(s) or removal of one or more glycosyl unit from a parent saccharide structure, followed by coupling a saccharyl fragment of the invention to the newly placed or exposed glycosyl residue.
The term “targeting moiety,” as used herein, refers to species that selectively localize in a particular tissue or region of the body. The localization is mediated by specific recognition of molecular determinants, molecular size of the targeting agent or conjugate, ionic interactions, hydrophobic interactions and the like. Other mechanisms of targeting an agent to a particular tissue or region are known to those of skill in the art. Exemplary targeting moieties include antibodies, antibody fragments, transferrin, HS-glycoprotein, coagulation factors, serum proteins, β-glycoprotein, G-CSF, GM-CSF, M-CSF, EPO and the like.
As used herein, “therapeutic moiety” means any agent useful for therapy including, but not limited to, antibiotics, anti-inflammatory agents, anti-tumor drugs, cytotoxins, and radioactive agents. “Therapeutic moiety” includes prodrugs of bioactive agents, constructs in which more than one therapeutic moiety is bound to a carrier, e.g, multivalent agents. Therapeutic moiety also includes proteins and constructs that include proteins. Exemplary proteins include, but are not limited to, Erythropoietin (EPO), Granulocyte Colony Stimulating Factor (GCSF), Granulocyte Macrophage Colony Stimulating Factor (GMCSF), Interferon (e.g., Interferon-α, -β, -γ), Interleukin (e.g., Interleukin II), serum proteins (e.g., Factors VII, VIIa, VIII, IX, and X), Human Chorionic Gonadotropin (HCG), Follicle Stimulating Hormone (FSH) and Lutenizing Hormone (LH) and antibody fusion proteins (e.g. Tumor Necrosis Factor Receptor ((TNFR)/Fc domain fusion protein)).
As used herein, “anti-tumor drug” means any agent useful to combat cancer including, but not limited to, cytotoxins and agents such as antimetabolites, alkylating agents, anthracyclines, antibiotics, antimitotic agents, procarbazine, hydroxyurea, asparaginase, corticosteroids, interferons and radioactive agents. Also encompassed within the scope of the term “anti-tumor drug,” are conjugates of peptides with anti-tumor activity, e.g. TNF-α. Conjugates include, but are not limited to those formed between a therapeutic protein and a glycoprotein of the invention. A representative conjugate is that formed between PSGL-1 and TNF-α.
As used herein, “a cytotoxin or cytotoxic agent” means any agent that is detrimental to cells. Examples include taxol, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine, colchicin, doxorubicin, daunorubicin, dihydroxy anthracinedione, mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, and puromycin and analogs or homologs thereof. Other toxins include, for example, ricin, CC-1065 and analogues, the duocarmycins. Still other toxins include diptheria toxin, and snake venom (e.g., cobra venom).
As used herein, “a radioactive agent” includes any radioisotope that is effective in diagnosing or destroying a tumor. Examples include, but are not limited to, indium-111, cobalt-60. Additionally, naturally occurring radioactive elements such as uranium, radium, and thorium, which typically represent mixtures of radioisotopes, are suitable examples of a radioactive agent. The metal ions are typically chelated with an organic chelating moiety.
Many useful chelating groups, crown ethers, cryptands and the like are known in the art and can be incorporated into the compounds of the invention (e.g., EDTA, DTPA, DOTA, NTA, HDTA, etc. and their phosphonate analogs such as DTPP, EDTP, HDTP, NTP, etc). See, for example, Pitt et al., “The Design of Chelating Agents for the Treatment of Iron Overload,” In, I
Additionally, a manifold of routes allowing the attachment of chelating agents, crown ethers and cyclodextrins to other molecules is available to those of skill in the art. See, for example, Meares et al., “Properties of In Vivo Chelate-Tagged Proteins and Polypeptides.” In, M
As used herein, “pharmaceutically acceptable carrier” includes any material, which when combined with the conjugate retains the conjugates' activity and is non-reactive with the subject's immune systems. Examples include, but are not limited to, any of the standard pharmaceutical carriers such as a phosphate buffered saline solution, water, emulsions such as oil/water emulsion, and various types of wetting agents. Other carriers may also include sterile solutions, tablets including coated tablets and capsules. Typically such carriers contain excipients such as starch, milk, sugar, certain types of clay, gelatin, stearic acid or salts thereof, magnesium or calcium stearate, talc, vegetable fats or oils, gums, glycols, or other known excipients. Such carriers may also include flavor and color additives or other ingredients. Compositions comprising such carriers are formulated by well known conventional methods.
As used herein, “administering” means oral administration, administration as a suppository, topical contact, intravenous, intraperitoneal, intramuscular, intralesional, or subcutaneous administration, administration by inhalation, or the implantation of a slow-release device, e.g., a mini-osmotic pump, to the subject. Adminsitration is by any route including parenteral and transmucosal (e.g., oral, nasal, vaginal, rectal, or transdermal), particularly by inhalation. Parenteral administration includes, e.g., intravenous, intramuscular, intra-arteriole, intradermal, subcutaneous, intraperitoneal, intraventricular, and intracranial. Moreover, where injection is to treat a tumor, e.g., induce apoptosis, administration may be directly to the tumor and/or into tissues surrounding the tumor. Other modes of delivery include, but are not limited to, the use of liposomal formulations, intravenous infusion, transdermal patches, etc.
The term “isolated” refers to a material that is substantially or essentially free from components, which are used to produce the material. For conjugates of the invention, the term “isolated” refers to material that is substantially or essentially free from components, which normally accompany the material in the mixture used to prepare the conjugate. “Isolated” and “pure” are used interchangeably. Typically, isolated conjugates of the invention have a level of purity preferably expressed as a range. The lower end of the range of purity for the conjugates is about 60%, about 70% or about 80% and the upper end of the range of purity is about 70%, about 80%, about 90% or more than about 90%.
When the conjugates are more than about 90% pure, their purities are also preferably expressed as a range. The lower end of the range of purity is about 90%, about 92%, about 94%, about 96% or about 98%. The upper end of the range of purity is about 92%, about 94%, about 96%, about 98% or about 100% purity.
Purity is determined by any art-recognized method of analysis (e.g., band intensity on a silver stained gel, polyacrylamide gel electrophoresis, HPLC, or a similar means).
“Essentially each member of the population,” as used herein, describes a characteristic of a population of peptide conjugates of the invention in which a selected percentage of the modified saccharyl fragments added to a peptide are added to multiple, identical acceptor sites on the peptide. “Essentially each member of the population” speaks to the “homogeneity” of the sites on the peptide conjugated to a modified saccharyl fragment and refers to conjugates of the invention, which are at least about 80%, preferably at least about 90% and more preferably at least about 95% homogenous.
“Homogeneity,” refers to the structural consistency across a population of acceptor moieties to which the modified saccharyl fragments are conjugated. Thus, in a peptide conjugate of the invention in which each modified saccharyl fragment moiety is conjugated to a site having the same structure as the site to which every other modified saccharyl fragment is conjugated, the peptide conjugate is said to be about 100% homogeneous. Homogeneity is typically expressed as a range. The lower end of the range of homogeneity for the peptide conjugates is about 60%, about 70% or about 80% and the upper end of the range of purity is about 70%, about 80%, about 90% or more than about 90%.
When the peptide conjugates are more than or equal to about 90% homogeneous, their homogeneity is also preferably expressed as a range. The lower end of the range of homogeneity is about 90%, about 92%, about 94%, about 96% or about 98%. The upper end of the range of purity is about 92%, about 94%, about 96%, about 98% or about 100% homogeneity. The purity of the peptide conjugates is typically determined by one or more methods known to those of skill in the art, e.g., liquid chromatography-mass spectrometry (LC-MS), matrix assisted laser desorption mass time of flight spectrometry (MALDITOF), capillary electrophoresis, and the like.
“Substantially uniform conjugate” or a “substantially uniform conjugation pattern,” when referring to a glycoconjugate species, refers to the percentage of peptide glycosylation sites that are functionalized directly, or through a glycosyl linker, with a modified saccharyl fragment. A substantially uniform conjugation pattern exists if substantially all (as defined below) members of a glycosylation site population intended to bear the modified saccharyl fragment are directly or indirectly functionalized with that fragment.
The term “substantially” in the above definitions of “substantially uniform” generally means at least about 40%, at least about 70%, at least about 80%, or more preferably at least about 90%, and still more preferably at least about 95% of the acceptor moieties for a particular modified saccharyl fragment are modified by that fragment.
The terms “(glyco)peptide” and “(glyco)lipid,” refer, respectively, to peptide and glycopeptide; and lipid and glycolipid. The terms “peptide” and “lipid” are used generically to refer to both glycosylated and non-glycosylated analogues of these species.
The present invention provides conjugates bearing one or more modified saccharyl fragment moiety. The modified fragment is attached to an acceptor moiety on a substrate, e.g., an amino acid or glycosyl residue of a peptide or glycopeptide, or onto an aglycone or glycosyl residue of a glycolipid (e.g., sphingosine, ceramide, etc.). Also provided are enzymatically-mediated methods for producing the conjugates of the invention, and activated modified saccharyl fragments of use in the methods. The invention also provides pharmaceutical formulations that include a conjugate formed by a method of the invention.
Conjugates of the invention are formed between a therapeutic core molecule, e.g., (glyco)peptide, (glyco)lipid, and diverse modifying groups such as water-soluble polymers, therapeutic moieties, diagnostic moieties, targeting moieties and the like. The modifying group is conjugated to the therapeutic species through a saccharyl fragment. Also provided are conjugates that include two or more peptides linked together through a linker arm, i.e., multifunctional conjugates. The multi-functional conjugates of the invention can include two or more copies of the same peptide or a collection of diverse peptides with different structures and/or properties. In exemplary conjugates according to this embodiment, the linker between the two peptides includes at least one saccharyl fragment, or modified saccharyl fragment as described herein.
The conjugates of the invention are prepared by the enzymatic conjugation of an activated modified saccharyl fragment to a therapeutic substrate. When the conjugate of the invention is a glycopeptide conjugate, the modified saccharyl fragment is attached directly to an amino acid of a glycosylation site, or to a glycosyl residue attached either directly or indirectly (e.g., through one or more glycosyl residue) to a glycosylation site.
The invention also provides lipid conjugates in which the modified saccharyl fragment is attached to an aglycone moiety of a lipid or to a glycosyl residue of a glycolipid.
The modified saccharyl fragment, when interposed between the peptide (or glycosyl residue) and the modifying group, becomes what is referred to herein as a “glycosyl linking group.” Using the exquisite selectivity of enzymes, such as glycosyl transferases, amidases, endoglycanases, endoglycoceramidases, and the like, the present method provides peptides and lipids that bear a desired group at one or more specific locations. Thus, in exemplary conjugates according to the present invention, a modified saccharyl fragment is attached directly to a selected locus on the peptide chain or, alternatively, the modified saccharyl fragment is appended onto a carbohydrate moiety of a glycopeptide. Peptides in which modified saccharyl fragments are bound to both a glycopeptide carbohydrate and directly to an amino acid residue of the peptide backbone are also within the scope of the present invention.
The methods of the invention make it possible to assemble modified glycopeptides and glycolipids that have a substantially homogeneous derivatization pattern; the enzymes used in the invention are generally selective for a particular glycosyl residue or for particular substituents, or substituent patterns, on a glycosyl residue. The methods are also practical for large-scale production of modified glycopeptide and glycolipid conjugates. In one embodiment the methods of the invention provide a practical means for large-scale preparation of glycopeptide and glycolipid conjugates having preselected uniform derivatization patterns. The methods are particularly well suited for modification of therapeutic peptides, including but not limited to, glycopeptides that are incompletely glycosylated during production in cell culture cells (e.g., mammalian cells, insect cells, plant cells, fungal cells, yeast cells, or prokaryotic cells) or transgenic plants or animals.
The methods of the invention also provide conjugates of glycosylated and unglycosylated peptides, and glycolipids, with increased therapeutic half-life due to, for example, reduced clearance rate, or reduced rate of uptake by the immune or reticuloendothelial system (RES). Moreover, the methods of the invention provide a means for masking antigenic determinants on peptides, thus reducing or eliminating a host immune response against the peptide. Selective attachment of targeting agents to a peptide or glycolipid using an appropriate modified saccharyl fragment can also be used to target the peptide or glycolipid to a particular tissue or cell surface receptor that is specific for the particular targeting agent. Moreover, there is provided a class of peptides and glycolipids that are specifically modified with a therapeutic moiety conjugated through a glycosyl linking group.
The present invention provides glyco-conjugates that include a saccharyl fragment functionalized with a modifying group. When the saccharyl fragment is formed by oxidation of a saccharide, e.g., sialic acid, the reagent used to conjugate the modifying group to the oxidized saccharide fragment generally includes a group that reacts with a carbonyl moiety formed during the oxidation.
The present invention provides compounds and methods that are based upon the discovery that enzymes capable of transferring an intact glycosyl moiety to an acceptor substrate are also capable of transferring a modified saccharyl fragment to the acceptor. Accordingly, the invention is not limited by the structure or methods of obtaining appropriate saccharyl fragments or modified saccharyl fragments.
In an exemplary embodiment, the saccharide fragment is prepared by the oxidative degradation of the parent saccharide. Methods of selectively oxidizing saccharide groups are well known in the art. For example, the periodate ion is of use to cleave vicinal diols, forming the corresponding dialdehyde. Controlled periodate oxidation of the side chain of sialic acid leads to the formation of an oxidized or oxidized and truncated side chain bearing an aldehyde. By chosing appropriate conditions, a side chain containing from one to three carbon atoms is produced. See, for example, Chai et al., Carbohydr. Res. 239:107-115 (1993); and Murray et al., Carbohydr. Res. 186: 107-115 (1989).
The carbonyl moiety introduced into the saccharyl fragment undergoes those reactions generally used for the modification of a carbonyl moiety. For example, modifying groups that include amines are of use as are those that form imines, e.g., hydrazines, semicarbazines and the like. Other typical reactions include the reaction of the carbonyl moiety with ylides (e.g., sulfur and phosphorus), and with Grignard and lithium reagents.
An exemplary modified saccharyl fragment of the invention is formed by the oxidative degradation of the side chain of sialic acid. The oxidation leads to the formation of a carbonyl moiety that is reductively aminated with an amine derivative of a modifying group of interest. Thus, in this embodiment, the invention provides a modified saccharyl fragment having a structure according to Formula I:
In Formula I, the symbol X1 represents O or NR8. R8 is a member selected from H, OH, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. Appropriate R1 groups are selected from OR9, NR9R10, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. The symbols R9 and R10 independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, and C(O)R11. R11 is a group such as substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl and substituted or unsubstituted heterocycloalkyl.
The symbol R2 is a member selected from an amino acid residue of a peptide, a carbohydrate moiety attached to an amino acid residue of a peptide, or a carbohydrate moiety attached to an amino acid residue of a peptide through a linker. Exemplary linkers include one or more additional carbohydrate moieties in addition to that of R2. R3 is a member selected from H, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. R3′ is a member selected from H, OR4′, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. R4 and R4′ are members independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, OH and NHC(O)R12. R12 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heterocycloalkyl and NR13R14, in which R13 and R14 are members independently selected from H, substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl. In an exemplary embodiment, R3′ is H.
Y is the residue of the sialic acid side chain remaining following oxidation and further chemical modification. Exemplary groups for Y include CH2, CH(OH)CH2, CH(OH)CH(OH)CH2 when the oxidation leads to formation of an aldehyde that is subsequently reductively aminated. When the aldehyde is converted to an imine species, or when the product results from addition of a phosphorus or sulfur ylide, Y is typically CH, CH(OH)CH or CH(OH)CH(OH)CH. When the aldehyde is reacted with a Grignard or lithium reagent, exemplary Y groups include CH(OH), CH(OH)CH(OH), CH(OH)CH(OH)CH(OH) or an elimination product thereof, e.g., dehydration product.
The symbol Y2 represents groups formed by addition to the carbonyl moiety of the fragment. Y2 includes at least one modifying group e.g., biomolecule, therapeutic moiety, diagnostic moiety, and a polymeric modifying group, as exemplified by the term R6a. Exemplary identities for Y2 include substituted alkyl (e.g., formed by Wittig, Grignard or other appropriate chemistries), R6 and nitrogen-containing species, e.g., NR6R7 or R6R7N—N═. R6 and R7 are independently H, C(O)R6b or -La-R6b wherein R6b is H or R6a and La is selected from a bond and a linker group. In an exemplary embodiment, Y2 is N(R6)-La-(m-PEG)s wherein La is a linker moiety which is a member selected from an amino acid residue and a peptidyl residue; and the index s is an integer from 1 to 3.
When Y2 is substituted or unsubstituted alkyl, e.g., an alkene species formed by a Wittig reaction, or saturated species formed by Grignard or lithium chemistries, Y2 includes at least one modifying group (water-soluble or -insoluble polymer) as exemplified by the term R6a.
In an exemplary embodiment, the modified saccharyl fragment is prepared by reacting a carbonyl-containing saccharyl fragment with a Wittig reagent that includes within its structure a water-soluble polymer, e.g., m-PEG. Wittig reagents of m-PEG are readily formed by reaction of chloro-m-PEG with PPh3 and treating the resulting adduct with a base to form the ylide. Other ylides of use in forming the compounds of the invention are prepared by deprotonating an alkyl phosphonate according to the Arbuzov reaction and reacting the carbonyl moiety of the saccharyl fragment with this ylide under conditions appropriate for the Horner-Emmons reaction.
Grignard reagents of use in present invention, e.g. m-PEGMgBr, are readily prepared according to art-recognized methods. For example, m-PEG-Br is reacted with Mg under anhydrous conditions.
In another exemplary embodiment, the carbonyl-containing saccharyl fragment is reductively aminated with ammonia. The resulting amine is alkylated or acylated with a selected modifying group, e.g., m-PEG or branched m-PEG.
Typically, the saccharyl fragment is a monosaccharide; however, because the side chain of sialic acid is selectively oxidized in the presence of the vicinal diols of other saccharides, the present invention is not limited to the use of modified sialic acid, but is of use with sialic acid fragment-containing oligosaccharides and polysaccharides as well.
In another aspect, the invention provides an activated modified saccharyl fragment that is of use in the methods of the invention. An exemplary activated modified saccharyl fragment includes an activated leaving group. As used herein, the term “activated leaving group” refers to those moieties, which are easily displaced in enzyme-regulated nucleophilic substitution reactions. Many activated sugars are known in the art. See, for example, Vocadlo et al., In C
In an exemplary embodiment, according to this aspect, the saccharyl fragment has a structure according to Formula I in which R2 is an activating group. An exemplary activating group is a nucleotide, forming a nucleotide sugar in which the sugar moiety is the saccharyl fragment. R2 can also be a leaving group (activating group), such as a halogen, sulfonate ester and the like.
An exemplary activated leaving group is a nucleotide, which can be utilized to add the modified saccharyl fragment to an acceptor moiety on the substrate. Exemplary sugar nucleotides present in the compounds of the invention include nucleotide mono-, di- or triphosphates or analogs thereof. In a preferred embodiment, the modified saccharyl fragment nucleotide is selected from a UDP-glycoside, CMP-glycoside, or a GDP-glycoside. Even more preferably, the modified saccharyl fragment nucleotide is selected from analogues of UDP-galactose, UDP-galactosamine, UDP-glucose, UDP-glucosamine, GDP-mannose, GDP-fucose, CMP-sialic acid or CMP-NeuAc in which the saccharyl moiety (other than the nucleotide ribose) is a saccharyl fragment bearing a modifying group.
In an exemplary embodiment, one or more sugar nucleotides or modified sugar nucleotides are used in conjunction with a glycosyltransferase.
In other embodiments, the activating moiety is an activated leaving group other than a nucleotide. Examples of non-nucleotide activating groups include fluoro, chloro, bromo, tosylate ester, mesylate ester, triflate ester and the like. Preferred activated leaving groups, for use in the present invention, are those that do not significantly sterically encumber the enzymatic transfer of the glycoside to the acceptor. Accordingly, preferred embodiments of activated glycoside derivatives include glycosyl fluorides and glycosyl mesylates, with glycosyl fluorides being particularly preferred. Among the glycosyl fluorides, α-galactosyl fluoride, α-mannosyl fluoride, α-glucosyl fluoride, α-fucosyl fluoride, α-xylosyl fluoride, α-sialyl fluoride, α-N-acetylglucosaminyl fluoride, α-N-acetylgalactosaminyl fluoride, β-galactosyl fluoride, β-mannosyl fluoride, β-glucosyl fluoride, β-fucosyl fluoride, β-xylosyl fluoride, β-sialyl fluoride, β-N-acetylglucosaminyl fluoride and β-N-acetylgalactosaminyl fluoride are most preferred.
By way of illustration, glycosyl fluorides can be prepared from the saccharyl fragment or modified saccharyl fragment by first acetylating the sugar and then treating it with HF/pyridine. This generates the thermodynamically most stable anomer of the protected (acetylated) glycosyl fluoride (i.e., the α-glycosyl fluoride). If the less stable anomer (i.e., the β-glycosyl fluoride) is desired, it can be prepared by converting the peracetylated sugar with HBr/HOAc or with HCl to generate the anomeric bromide or chloride. This intermediate is reacted with a fluoride salt such as silver fluoride to generate the glycosyl fluoride. Acetylated glycosyl fluorides may be deprotected by reaction with mild (catalytic) base in methanol (e.g. NaOMe/MeOH). In addition, many glycosyl fluorides are commercially available.
Other activated glycosyl derivatives can be prepared using conventional methods known to those of skill in the art. For example, glycosyl mesylates can be prepared by treatment of the fully benzylated hemiacetal form of the sugar with mesyl chloride, followed by catalytic hydrogenation to remove the benzyl groups.
In an exemplary embodiment, one or more activated glycosyl derivative such as those set forth above is used in conjunction with an enzyme that is a mutant of a degradative enzyme; mutated to enhance its activity forming glycosidic and amino-glycosidic bonds relative to the activity of the wild-type, which predominantly cleave these bonds. Enzymes of use in this embodiment include those described in WO03/046150, WO03/045980, and their US counterpart patent applications).
In addition to including a moiety according to Formula I, the conjugates of the invention can include one or more additional modified saccharyl fragment appended to an amino acid, aglycone or glycosyl residue of the conjugate. The structure and preparation of exemplary modified saccharyl fragments that are of use in combination with the modified saccharyl fragment of the invention are also disclosed in WO03/031464 and related U.S. and PCT applications.
Any sugar can be utilized as the sugar core of the modified saccharyl fragment conjugates of the invention. Exemplary sugar cores that are useful in forming the compositions of the invention include, but are not limited to, sialic acid, glucose, galactose, and mannose and N-acetyl analogues of these sugars. Also of use are fucose, xylose, ribose, and arabinose. Also encompassed within the invention are species in which the sugar core is a disaccharide, an oligosaccharide or a polysaccharide.
The invention provides a peptide or lipid conjugate that includes a glycosyl linking group having the formula:
In other embodiments, the glycosyl linking group has the formula:
in which the index t is 0 or 1.
In a still further exemplary embodiment, the glycosyl linking group has the formula:
in which the index t is 0 or 1.
In yet another embodiment, the glycosyl linking group has the formula:
in which the index p represents an integer from 1 to 10; and a is either 0 or 1.
In an exemplary embodiment, the invention provides a glycoPEGylated peptide conjugate which is selected from the formulae set forth below:
In the formulae above, the index t is an integer from 0 to 1 and the index p is an integer from 1 to 10. The symbol R15′ represents H, OH (e.g., Gal-OH), a modified saccharyl fragment (Msf), a Msf which comprises -La-R6a, a Msf which comprises R6a, wherein R6a is a polymeric modifying group, or a sialyl moiety to which is bound a modified saccharyl fragment which comprises -La-R6a (e.g., Sia-Msf-La-R6a), or a sialyl moiety to which is bound a modified saccharyl fragment which comprises R6a, (e.g., Sia-Msf-R6a) (“Sia-Msfp”). Exemplary polymer modified saccharyl moieties have a structure according to Formula I. An exemplary peptide conjugate of the invention will include at least one glycan having a R15′ that includes a structure according to Formula I. In a further exemplary embodiment, the oxygen is attached to the carbon at position 3 of a galactose residue. In an exemplary embodiment, the modified sialic acid is linked α2,3-to the galactose residue. In another exemplary embodiment, the sialic acid is linked α2,6-to the galactose residue.
In an exemplary embodiment, R15′ is a sialyl moiety to which is bound a modified saccharyl fragment which comprises -La-R6a, or R6a, (e.g., Sia-Msf-La-R6a) (“Sia-Msfp”)). Here, the glycosyl linking group is linked to a galactosyl moiety through a sialyl moiety:
An exemplary species according to this motif is prepared by conjugating Msf-La-R6a to a terminal sialic acid of a glycan using an enzyme that forms Sia-Sia bonds, e.g., CST-II, ST8Sia-II, ST8Sia-III and ST8Sia-IV.
In another exemplary embodiment, the glycans on the peptide conjugates have a formula that is selected from the group:
and combinations thereof.
In each of the formulae above, R15′ is as discussed above. Moreover, an exemplary peptide conjugate of the invention will include at least one glycan with an R15′ moiety having a structure according to Formula.
In another exemplary embodiment, the glycosyl linking group has a formula according to:
wherein R15 includes a modified saccharyl fragment; and the index p is an integer selected from 1 to 10.
In an exemplary embodiment, the modified saccharyl fragment has the formula:
in which b is an integer from 0 to 1. The index s represents an integer from 1 to 10; and the index f represents an integer from 1 to 2500.
In another exemplary embodiment, the peptide conjugate comprises a glycosyl moiety selected from the formulae:
in which the index p is an integer from 1 to 10. The indices t and a are independently selected from 0 or 1. The indices m and n are integers independently selected from 0 to 5000. The indices j and k are integers independently selected from 0 to 20. A1, A2, A3, A4, A5, A6, A7, A8, A9, A10 and A11 are members independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, —NA12A13, —OA12 and —SiA12A13. A12 and A13 are members independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl. AA is an amino acid residue of the peptide. Each of these groups can be included as components of the mono-, bi-, tri- and tetra-antennary saccharide structures set forth above. La is a linker that results from the reaction of the polymer modifying group moiety and the modified saccharyl fragment. Exemplary linking groups include substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl moieties. An exemplary component of the linker is an acyl moiety. Another exemplary linking group is an amino acid (e.g., cysteine, serine, lysine, and short oligopeptides, e.g., Lys-Lys, Lys-Lys-Lys, Cys-Lys, Ser-Lys, etc.).
The peptide conjugates of the invention comprise a modifying group. This group can be covalently attached to a peptide through an amino acid or a glycosyl linking group. “Modifying groups” can encompass a variety of structures including targeting moieties, therapeutic moieties, biomolecules. Additionally, “modifying groups” include polymeric modifying groups, which can alter a property of the peptide such as its bioavailability or its half-life in the body.
In an exemplary embodiment, the modifying group is a targeting agent that localizes selectively in a particular tissue due to the presence of a targeting agent as a component of the conjugate. In an exemplary embodiment, the targeting agent is a protein. Exemplary proteins include transferrin (brain, blood pool), HS-glycoprotein (bone, brain, blood pool), antibodies (brain, tissue with antibody-specific antigen, blood pool), coagulation factors V-XII (damaged tissue, clots, cancer, blood pool), serum proteins, e.g., α-acid glycoprotein, fetuin, α-fetal protein (brain, blood pool), β2-glycoprotein (liver, atherosclerosis plaques, brain, blood pool), G-CSF, GM-CSF, M-CSF, and EPO (immune stimulation, cancers, blood pool, red blood cell overproduction, neuroprotection), albumin (increase in half-life), and lipoprotein E.
For the purposes of convenience, the modifying groups in the remainder of this section will be largely based on polymeric modifying groups such as water soluble and water insoluble polymers. However, one of skill in the art will recognize that other modifying groups, such as targeting moieties, therapeutic moieties and biomolecules, could be used in place of the polymeric modifying groups.
The linkers of the modifying group serve to attach the modifying group (ie polymeric modifying groups, targeting moieties, therapeutic moieties and biomolecules) to the glycosyl linking group. In an exemplary embodiment, the polymeric modifying group is bound to a glycosyl linking group, generally through a heteroatom, e.g, nitrogen, on the core through a linker, La, as shown below:
R6a is the polymeric modifying moiety and La is selected from a bond and a linking group. The index w represents an integer selected from 1-6, preferably 1-3 and more preferably 1-2. Exemplary linking groups include substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl moieties. An exemplary component of the linker is an acyl moiety.
In an exemplary embodiment, the invention has a structure according to Formula I above, in which Y2 is selected from the formulae:
In another exemplary embodiment, the compound is the product of a Wittig reaction and Y2 has the formula:
In another exemplary embodiment, the compound is formed from a reaction of the modified glycosyl linking fragment with a Grignard or lithium reagent and Y2 has a structure selected from the formulae:
In yet another exemplary embodiment, the glycosyl linking group and the polymeric modifying group are linked through a diamine. In an exemplary compound according to this aspect of the invention Y2 has the formula:
In another exemplary embodiment the glycosyl linking group and the modifying group are linked through an aminocarboxylic acid. In an exemplary compound according to this aspect of the invention Y2 has the formula:
In yet another exemplary embodiment the aldehyde containing glycosyl linking group is reductively aminated with ammonia and the resulting amine is used to attach the polymeric modifying group, thereby forming an amide bond. In this aspect of the invention Y2 is selected from the formulae:
in which the index s is an integer from 0 to 20.
In an exemplary embodiment, the polymeric modifying group-linker construct is a branched structure that includes two or more polymeric chains attached to central moiety. In this embodiment, the construct has the formula:
in which R6a and La are as discussed above and w′ is an integer from 2 to 6, preferably from 2 to 4 and more preferably from 2 to 3.
When La is a bond it is formed between a reactive functional group on a precursor of R6a and a reactive functional group of complementary reactivity on the saccharyl core. When La is a non-zero order linker, a precursor of La can be in place on the glycosyl moiety prior to reaction with the R6a precursor. Alternatively, the precursors of R6a and La can be incorporated into a preformed cassette that is subsequently attached to the glycosyl moiety. As set forth herein, the selection and preparation of precursors with appropriate reactive functional groups is within the ability of those skilled in the art. Moreover, coupling the precursors proceeds by chemistry that is well understood in the art.
In an exemplary embodiment, La is a linking group that is formed from an amino acid, or small peptide (e.g., 1-4 amino acid residues) providing a modified sugar in which the polymeric modifying group is attached through a substituted alkyl linker. Exemplary linkers include glycine, lysine, serine and cysteine. The PEG moiety can be attached to the amine moiety of the linker through an amide or urethane bond. The PEG is linked to the sulfur or oxygen atoms of cysteine and serine through thioether or ether bonds, respectively.
Many water-soluble polymers are known to those of skill in the art and are useful in practicing the present invention. The term water-soluble polymer encompasses species such as saccharides (e.g., dextran, amylose, hyalouronic acid, poly(sialic acid), heparans, heparins, etc.); poly (amino acids), e.g., poly(aspartic acid) and poly(glutamic acid); nucleic acids; synthetic polymers (e.g., poly(acrylic acid), poly(ethers), e.g., poly(ethylene glycol); peptides, proteins, and the like. The present invention may be practiced with any water-soluble polymer with the sole limitation that the polymer must include a point at which the remainder of the conjugate can be attached.
Methods for activation of polymers can also be found in WO 94/17039, U.S. Pat. No. 5,324,844, WO 94/18247, WO 94/04193, U.S. Pat. No. 5,219,564, U.S. Pat. No. 5,122,614, WO 90/13540, U.S. Pat. No. 5,281,698, and more WO 93/15189, and for conjugation between activated polymers and peptides, e.g. Coagulation Factor VIII (WO 94/15625), hemoglobin (WO 94/09027), oxygen carrying molecule (U.S. Pat. No. 4,412,989), ribonuclease and superoxide dismutase (Veronese at al., App. Biochem. Biotech. 11: 141-45 (1985)).
Exemplary water-soluble polymers are those in which a substantial proportion of the polymer molecules in a sample of the polymer are of approximately the same molecular weight; such polymers are “homodisperse.”
The present invention is further illustrated by reference to a poly(ethylene glycol) conjugate. Several reviews and monographs on the functionalization and conjugation of PEG are available. See, for example, Harris, Macronol. Chem. Phys. C25: 325-373 (1985); Scouten, Methods in Enzymology 135: 30-65 (1987); Wong et al., Enzyme Microb. Technol. 14: 866-874 (1992); Delgado et al., Critical Reviews in Therapeutic Drug Carrier Systems 9: 249-304 (1992); Zalipsky, Bioconjugate Chem. 6: 150-165 (1995); and Bhadra, et al., Pharmazie, 57:5-29 (2002). Routes for preparing reactive PEG molecules and forming conjugates using the reactive molecules are known in the art. For example, U.S. Pat. No. 5,672,662 discloses a water soluble and isolatable conjugate of an active ester of a polymer acid selected from linear or branched poly(alkylene oxides), poly(oxyethylated polyols), poly(olefinic alcohols), and poly(acrylomorpholine).
U.S. Pat. No. 6,376,604 sets forth a method for preparing a water-soluble 1-benzotriazolylcarbonate ester of a water-soluble and non-peptidic polymer by reacting a terminal hydroxyl of the polymer with di(1-benzotriazoyl)carbonate in an organic solvent. The active ester is used to form conjugates with a biologically active agent such as a protein or peptide.
WO 99/45964 describes a conjugate comprising a biologically active agent and an activated water soluble polymer comprising a polymer backbone having at least one terminus linked to the polymer backbone through a stable linkage, wherein at least one terminus comprises a branching moiety having proximal reactive groups linked to the branching moiety, in which the biologically active agent is linked to at least one of the proximal reactive groups. Other branched poly(ethylene glycols) are described in WO 96/21469, U.S. Pat. No. 5,932,462 describes a conjugate formed with a branched PEG molecule that includes a branched terminus that includes reactive functional groups. The free reactive groups are available to react with a biologically active species, such as a protein or peptide, forming conjugates between the poly(ethylene glycol) and the biologically active species. U.S. Pat. No. 5,446,090 describes a bifunctional PEG linker and its use in forming conjugates having a peptide at each of the PEG linker termini.
Conjugates that include degradable PEG linkages are described in WO 99/34833; and WO 99/14259, as well as in U.S. Pat. No. 6,348,558. Such degradable linkages are applicable in the present invention.
The art-recognized methods of polymer activation set forth above are of use in the context of the present invention in the formation of the branched polymers set forth herein and also for the conjugation of these branched polymers to other species, e.g., sugars, sugar nucleotides and the like.
An exemplary water-soluble polymer is poly(ethylene glycol), e.g., methoxy-poly(ethylene glycol). The poly(ethylene glycol) used in the present invention is not restricted to any particular form or molecular weight range. For unbranched poly(ethylene glycol) molecules the molecular weight is preferably between 500 and 100,000. A molecular weight of 2000-60,000 is preferably used and preferably of from about 5,000 to about 40,000.
In an examplary embodiment, poly(ethylene glycol) molecules of the invention include, but are not limited to, those species set forth below.
in which R18 is H, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted heteroalkyl, e.g., acetal, OHC—, H2N—CH2CH2—, HS—CH2CH2—, and —(CH2)qC(Y1)Z2; -sugar-nucleotide, or protein. The index “c” represents an integer from 1 to 2500. The indeces d, o, and q independently represent integers from 0 to 20. The symbol Z1 represents OH, NH2, halogen, S—R19, the alcohol portion of activated esters, —(CH2)d1C(Y3)V, —(CH2)d1U(CH2)gC(Y3)v, sugar-nucleotide, protein, and leaving groups, e.g., imidazole, p-nitrophenyl, HOBT, tetrazole, halide. The symbols X, Y1, Y3, W, U independently represent the moieties O, S, N—R20. The symbol V represents OH, NH2, halogen, S—R21, the alcohol component of activated esters, the amine component of activated amides, sugar-nucleotides, and proteins. The indeces d1, g and v are members independently selected from the integers from 0 to 20. The symbols R19, R20 and R21 independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heterocycloalkyl and substituted or unsubstituted heteroaryl.
In other exemplary embodiments, the poly(ethylene glycol) molecule is selected from the following:
In another embodiment the poly(ethylene glycol) is a branched PEG having more than one PEG moiety attached. Examples of branched PEGs are described in U.S. Pat. No. 5,932,462; U.S. Pat. No. 5,342,940; U.S. Pat. No. 5,643,575; U.S. Pat. No. 5,919,455; U.S. Pat. No. 6,113,906; U.S. Pat. No. 5,183,660; WO 02/09766; Kodera Y., Bioconjugate Chemistry 5: 283-288 (1994); and Yamasaki et al., Agric. Biol. Chem., 52: 2125-2127, 1998. In a preferred embodiment the molecular weight of each poly(ethylene glycol) of the branched PEG is less than or equal to 40,000 daltons.
Representative polymeric modifying moieties include structures that are based on side chain-containing amino acids, e.g., serine, cysteine, lysine, and small peptides, e.g., lyslys. Exemplary structures include:
Those of skill will appreciate that the free amine in the di-lysine structures can also be pegylated through an amide or urethane bond with a PEG moiety.
In yet another embodiment, the polymeric modifying moiety is a branched PEG moiety that is based upon a tri-lysine peptide. The tri-lysine can be mono-, di-, tri-, or tetra-PEG-ylated. Exemplary species according to this embodiment have the formulae:
in which the indices e, f and f′ are independently selected integers from 1 to 2500; and the indices q, q′ and q″ are independently selected integers from 1 to 20.
As will be apparent to those of skill, the branched polymers of use in the invention include variations on the themes set forth above. For example the di-lysine-PEG conjugate shown above can include three polymeric subunits, the third bonded to the α-amine shown as unmodified in the structure above. Similarly, the use of a tri-lysine functionalized with three or four polymeric subunits labeled with the polymeric modifying moiety in a desired manner is within the scope of the invention.
As discussed herein, the PEG of use in the conjugates of the invention can be linear or branched. An exemplary precursor of use to form the branched PEG containing peptide conjugates according to this embodiment of the invention has the formula:
Another exemplary precursor of use to form the branched PEG containing peptide conjugates according to this embodiment of the invention has the formula:
in which the indices m and n are integers independently selected from 0 to 5000. The indices t and a are independently selected from 0 or 1. The indices j and k are integers independently selected from 0 to 20. A1, A2, A3, A4, A5, A6, A7, A8, A9, A10 and A11 are members independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, —NA12A13, —OA12 and —SiA12A13. A12 and A13 are members independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl.
The branched polymer species according to this formula are essentially pure water-soluble polymers. X3′ is a moiety that includes an ionizable (e.g., OH, COOH, H2PO4, HSO3, NH2, and salts thereof, etc.) or other reactive functional group, e.g., infra. C is carbon. X5, R16 and R17 are independently selected from non-reactive groups (e.g., H, unsubstituted alkyl, unsubstituted heteroalkyl) and polymeric arms (e.g., PEG). X2 and X4 are linkage fragments that are preferably essentially non-reactive under physiological conditions, which may be the same or different. An exemplary linker includes neither aromatic nor ester moieties. Alternatively, these linkages can include one or more moiety that is designed to degrade under physiologically relevant conditions, e.g., esters, disulfides, etc. X2 and X4 join polymeric arms R16 and R17 to C. When X3′ is reacted with a reactive functional group of complementary reactivity on a linker, sugar or linker-sugar cassette, X3′ is converted to a component of linkage fragment X3.
Exemplary linkage fragments for X2, X3 and X4 are independently selected and include S, SC(O)NH, HNC(O)S, SC(O)O, O, NH, NHC(O), (O)CNH and NHC(O)O, and OC(O)NH, CH2S, CH2O, CH2CH2O, CH2CH2S, (CH2)oO, (CH2)oS or (CH2)oY′-PEG wherein, Y′ is S, NH, NHC(O), C(O)NH, NHC(O)O, OC(O)NH, or O and o is an integer from 1 to 50. In an exemplary embodiment, the linkage fragments X2 and X4 are different linkage fragments.
In an exemplary embodiment, the precursor (Formula II), or an activated derivative thereof, is reacted with, and thereby bound to a sugar, an activated sugar or a sugar nucleotide through a reaction between X3′ and a group of complementary reactivity on the sugar moiety, e.g., an amine. Alternatively, X3′ reacts with a reactive functional group on a precursor to linker, L.
In an exemplary embodiment, the moiety:
is the linker arm, L. In this embodiment, an exemplary linker is derived from a natural or unnatural amino acid, amino acid analogue or amino acid mimetic, or a small peptide formed from one or more such species. For example, certain branched polymers found in the compounds of the invention have the formula:
Xa is a linkage fragment that is formed by the reaction of a reactive functional group, e.g., X3′, on a precursor of the branched polymeric modifying moiety and a reactive functional group on the sugar moiety, or a precursor to a linker. For example, when X3′ is a carboxylic acid, it can be activated and bound directly to an amine group pendent from an amino-saccharide (e.g., Sia, GalNH2, GlcNH2, ManNH2, etc.), forming a Xa that is an amide. Additional exemplary reactive functional groups and activated precursors are described hereinbelow. The index c represents an integer from 1 to 10. The other symbols have the same identity as those discussed above.
In another exemplary embodiment, Xa is a linking moiety formed with another linker:
in which Xb is a second linkage fragment and is independently selected from those groups set forth for Xa, and, similar to La, L1 is a bond, substituted or unsubstituted alkyl or substituted or unsubstituted heteroalkyl.
Exemplary species for Xa and Xb include S, SC(O)NH, HNC(O)S, SC(O)O, O, NH, NHC(O), C(O)NH and NHC(O)O, and OC(O)NH.
In another exemplary embodiment, X4 is a peptide bond to R17, which is an amino acid, di-peptide (e.g.,, Lys-Lys) or tri-peptide (e.g., Lys-Lys-Lys) in which the alpha-amine moiety(ies) and/or side chain heteroatom(s) are modified with a polymeric modifying moiety.
In a further exemplary embodiment, the peptide conjugates of the invention include a moiety, e.g., an R15′ moiety that has a formula that is selected from:
in which the identity of the radicals represented by the various symbols is the same as that discussed hereinabove. La is a bond or a linker as discussed above for L and L1, e.g., substituted or unsubstituted alkyl or substituted or unsubstituted heteroalkyl moiety. In an exemplary embodiment, La is a moiety that is functionalized with the polymeric modifying moiety as shown. Exemplary La moieties include substituted or unsubstituted alkyl chains, NH and NR6.
In yet another exemplary embodiment, the invention provides peptide conjugates having a moiety, e.g., an R15′ moiety with formula:
The identity of the radicals represented by the various symbols is the same as that discussed hereinabove. As those of skill will appreciate, the linker arm in Formula VII is equally applicable to other modified sugars set forth herein. In an exemplary embodiment, the species of Formula VII is the R15 moieties attached to the glycan structures set forth herein.
In an exemplary embodiment, the glycosyl linking group has a structure according to the following formula:
The embodiments of the invention set forth above are further exemplified by reference to species in which the polymer is a water-soluble polymer, particularly poly(ethylene glycol) (“PEG”), e.g., methoxy-poly(ethylene glycol). Those of skill will appreciate that the focus in the sections that follow is for clarity of illustration and the various motifs set forth using PEG as an exemplary polymer are equally applicable to species in which a polymer other than PEG is utilized.
PEG of any molecular weight, e.g., 1 kDa, 2 kDa, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa and 80 kDa is of use in the present invention.
In other exemplary embodiments, the peptide conjugate includes an R15′ moiety selected from the group:
In each of the formulae above, the indices e and f are independently selected from the integers from 1 to 2500. In further exemplary embodiments, e and f are selected to provide a PEG moiety that is about 1 kDa, 2 kDa, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa and 80 kDa. The symbol Q represents substituted or unsubstituted alkyl (e.g., C1-C6 alkyl, e.g., methyl), substituted or unsubstituted heteroalkyl or H.
Other branched polymers have structures based on di-lysine (Lys-Lys) peptides, e.g.:
and tri-lysine peptides (Lys-Lys-Lys), e.g.:
In each of the figures above, the indices e, f, f′ and f″ represent integers independently selected from 1 to 2500. The indices q, q′ and q″ represent integers independently selected from 1 to 20.
In another exemplary embodiment, Y2 has a formula that is a member selected from:
wherein Q is a member selected from H and substituted or unsubstituted C1-C6 alkyl. The indices e and f are integers independently selected from 1 to 2500, and the index q is an integer selected from 0 to 20.
In another exemplary embodiment, Y2 has a formula that is a member selected from:
wherein Q is a member selected from H and substituted or unsubstituted C1-C6 alkyl. The indices e, f and f′ are integers independently selected from 1 to 2500, and q and q′ are integers independently selected from 1 to 20.
In another exemplary embodiment, the branched polymer has a structure according to the following formula:
in which the indices m and n are integers independently selected from 0 to 5000. The indices t and a are independently selected from 0 or 1. The indices j and k are integers independently selected from 0 to 20. A1, A2, A3, A4, A5, A6, A7, A8, A9, A10 and A11 are members independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, —NA12A13, —OA12 and —SiA12A13. A12 and A13 are members independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl.
Formula IIa is a subset of Formula II. The structures described by Formula Ia are also encompassed by Formula II.
In another exemplary embodiment according to the formula above, the branched polymer has a structure according to the following formula:
In an exemplary embodiment, A1 and A2 are each —OCH3 or H.
In an exemplary embodiment the modified saccharyl fragment is linked to the polymeric modifying group by reacting the aldehyde group of the oxidized sialyl side chain with a Grignard reagent or a Wittig reagent or an appropriate amine containing reagent, thereby forming an imine, which is alternatively reduced. Formulae according to this embodiment include:
In another exemplary embodiment the modified saccharyl fragment is linked to the polymeric modifying group through a diamino alkyl linker or an amino carboxylic acid linker. Formulae according to this embodiment include:
in which the index h is an integer from 0 to 20 and the indices q, q′, e and f are as defined above.
In an illustrative embodiment, the aldehyde group of the oxidized sialyl side chain of the modified saccharyl fragment is functionalized with the modifying group. For example, the aldehyde is reductively aminated with ammonia. The resulting primary amine is functionalized to provide a compound according to the invention. Formulae according to this embodiment include:
The indices h, i and 1 are integers from 0 to 20. The index r is an integer from 1 to 2500. The structures set forth above can be components of R15′.
Although the present invention is exemplified in the preceding sections by reference to PEG, as those of skill will appreciate, an array of polymeric modifying moieties is of use in the compounds and methods set forth herein.
In selected embodiments, R6a or L-R6b is a branched PEG, for example, one of the species set forth above. In an exemplary embodiment, the branched PEG structure is based on a cysteine peptide. Illustrative modified saccharyl fragments according to this embodiment include:
in which X4 is a bond or O. In each of the structures above, the alkylamine linker —NHC(O)(CH2)h— can be present or absent. The structures set forth above can be components of R15/R15′.
As discussed herein, the polymeric modifying groups of use in the invention may also be linear structures. Thus, the invention provides for conjugates that include a modified saccharyl fragment derived from a structure such as:
in which the indices q and e are as discussed above.
Exemplary modified sugars are modified with water-soluble or water-insoluble polymers. Examples of useful polymer are further exemplified below.
In another exemplary embodiment, the peptide is derived from insect cells, remodeled by adding GlcNAc and Gal to the mannose core and glycopegylated using a sialic acid bearing a linear PEG moiety, affording a peptide conjugate that comprises at least one moiety having the formula:
in which the index t is an integer from 0 to 1; the index s represents an integer from 1 to 10; and the index f represents an integer from 1 to 2500.
In another embodiment, analogous to those discussed above, the modified sugars include a water-insoluble polymer, rather than a water-soluble polymer. The conjugates of the invention may also include one or more water-insoluble polymers. This embodiment of the invention is illustrated by the use of the conjugate as a vehicle with which to deliver a therapeutic peptide in a controlled manner. Polymeric drug delivery systems are known in the art. See, for example, Dunn et al., Eds. P
The motifs set forth above for R6a, La-R6a, R15, R15′ and other radicals are equally applicable to water-insoluble polymers, which may be incorporated into the linear and branched structures without limitation utilizing chemistry readily accessible to those of skill in the art. Similarly, the incorporation of these species into any of the modified sugars discussed herein is within the scope of the present invention. Accordingly, the invention provides conjugates containing, and for the use of to prepare such conjugates, sialic acid and other sugar moieties modified with a linear or branched water-insoluble polymers, and activated analogues of the modified sialic acid species (e.g., CMP-Sia-(water insoluble polymer)).
Representative water-insoluble polymers include, but are not limited to, polyphosphazines, poly(vinyl alcohols), polyamides, polycarbonates, polyalkylenes, polyacrylamides, polyalkylene glycols, polyalkylene oxides, polyalkylene terephthalates, polyvinyl ethers, polyvinyl esters, polyvinyl halides, polyvinylpyrrolidone, polyglycolides, polysiloxanes, polyurethanes, poly(methyl methacrylate), poly(ethyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate), poly(hexyl methacrylate), poly(isodecyl methacrylate), poly(lauryl methacrylate), poly(phenyl methacrylate), poly(methyl acrylate), poly(isopropyl acrylate), poly(isobutyl acrylate), poly(octadecyl acrylate)polyethylene, polypropylene, poly(ethylene glycol), poly(ethylene oxide), poly (ethylene terephthalate), poly(vinyl acetate), polyvinyl chloride, polystyrene, polyvinyl pyrrolidone, pluronics and polyvinylphenol and copolymers thereof.
Synthetically modified natural polymers of use in conjugates of the invention include, but are not limited to, alkyl celluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters, and nitrocelluloses. Particularly preferred members of the broad classes of synthetically modified natural polymers include, but are not limited to, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, cellulose acetate phthalate, carboxymethyl cellulose, cellulose triacetate, cellulose sulfate sodium salt, and polymers of acrylic and methacrylic esters and alginic acid.
These and the other polymers discussed herein can be readily obtained from commercial sources such as Sigma Chemical Co. (St. Louis, Mo.), Polysciences (Warrenton, Pa.), Aldrich (Milwaukee, Wis.), Fluka (Ronkonkoma, N.Y.), and BioRad (Richmond, Calif.), or else synthesized from monomers obtained from these suppliers using standard techniques.
Representative biodegradable polymers of use in the conjugates of the invention include, but are not limited to, polylactides, polyglycolides and copolymers thereof, poly(ethylene terephthalate), poly(butyric acid), poly(valeric acid), poly(lactide-co-caprolactone), poly(lactide-co-glycolide), polyanhydrides, polyorthoesters, blends and copolymers thereof. Of particular use are compositions that form gels, such as those including collagen, pluronics and the like.
The polymers of use in the invention include “hybrid” polymers that include water-insoluble materials having within at least a portion of their structure, a bioresorbable molecule. An example of such a polymer is one that includes a water-insoluble copolymer, which has a bioresorbable region, a hydrophilic region and a plurality of crosslinkable functional groups per polymer chain.
For purposes of the present invention, “water-insoluble materials” includes materials that are substantially insoluble in water or water-containing environments. Thus, although certain regions or segments of the copolymer may be hydrophilic or even water-soluble, the polymer molecule, as a whole, does not to any substantial measure dissolve in water.
For purposes of the present invention, the term “bioresorbable molecule” includes a region that is capable of being metabolized or broken down and resorbed and/or eliminated through normal excretory routes by the body. Such metabolites or break down products are preferably substantially non-toxic to the body.
The bioresorbable region may be either hydrophobic or hydrophilic, so long as the copolymer composition as a whole is not rendered water-soluble. Thus, the bioresorbable region is selected based on the preference that the polymer, as a whole, remains water-insoluble. Accordingly, the relative properties, i.e., the kinds of functional groups contained by, and the relative proportions of the bioresorbable region, and the hydrophilic region are selected to ensure that useful bioresorbable compositions remain water-insoluble.
Exemplary resorbable polymers include, for example, synthetically produced resorbable block copolymers of poly(α-hydroxy-carboxylic acid)/poly(oxyalkylene, (see, Cohn et al., U.S. Pat. No. 4,826,945). These copolymers are not crosslinked and are water-soluble so that the body can excrete the degraded block copolymer compositions. See, Younes et al., J Biomed. Mater. Res. 21: 1301-1316 (1987); and Cohn et al., J Biomed. Mater. Res. 22: 993-1009 (1988).
Presently preferred bioresorbable polymers include one or more components selected from poly(esters), poly(hydroxy acids), poly(lactones), poly(amides), poly(ester-amides), poly(amino acids), poly(anhydrides), poly(orthoesters), poly(carbonates), poly(phosphazines), poly(phosphoesters), poly(thioesters), polysaccharides and mixtures thereof. More preferably still, the biosresorbable polymer includes a poly(hydroxy) acid component. Of the poly(hydroxy) acids, polylactic acid, polyglycolic acid, polycaproic acid, polybutyric acid, polyvaleric acid and copolymers and mixtures thereof are preferred.
In addition to forming fragments that are absorbed in vivo (“bioresorbed”), preferred polymeric coatings for use in the methods of the invention can also form an excretable and/or metabolizable fragment.
Higher order copolymers can also be used in the present invention. For example, Casey et al., U.S. Pat. No. 4,438,253, which issued on Mar. 20, 1984, discloses tri-block copolymers produced from the transesterification of poly(glycolic acid) and an hydroxyl-ended poly(alkylene glycol). Such compositions are disclosed for use as resorbable monofilament sutures. The flexibility of such compositions is controlled by the incorporation of an aromatic orthocarbonate, such as tetra-p-tolyl orthocarbonate into the copolymer structure.
Other polymers based on lactic and/or glycolic acids can also be utilized. For example, Spinu, U.S. Pat. No. 5,202,413, which issued on Apr. 13, 1993, discloses biodegradable multi-block copolymers having sequentially ordered blocks of polylactide and/or polyglycolide produced by ring-opening polymerization of lactide and/or glycolide onto either an oligomeric diol or a diamine residue followed by chain extension with a di-functional compound, such as, a diisocyanate, diacylchloride or dichlorosilane.
Bioresorbable regions of coatings useful in the present invention can be designed to be hydrolytically and/or enzymatically cleavable. For purposes of the present invention, “hydrolytically cleavable” refers to the susceptibility of the copolymer, especially the bioresorbable region, to hydrolysis in water or a water-containing environment. Similarly, “enzymatically cleavable” as used herein refers to the susceptibility of the copolymer, especially the bioresorbable region, to cleavage by endogenous or exogenous enzymes.
When placed within the body, the hydrophilic region can be processed into excretable and/or metabolizable fragments. Thus, the hydrophilic region can include, for example, polyethers, polyalkylene oxides, polyols, poly(vinyl pyrrolidine), poly(vinyl alcohol), poly(alkyl oxazolines), polysaccharides, carbohydrates, peptides, proteins and copolymers and mixtures thereof. Furthermore, the hydrophilic region can also be, for example, a poly(alkylene) oxide. Such poly(alkylene) oxides can include, for example, poly(ethylene) oxide, poly(propylene) oxide and mixtures and copolymers thereof.
Polymers that are components of hydrogels are also useful in the present invention. Hydrogels are polymeric materials that are capable of absorbing relatively large quantities of water. Examples of hydrogel forming compounds include, but are not limited to, polyacrylic acids, sodium carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidine, gelatin, carrageenan and other polysaccharides, hydroxyethylenemethacrylic acid (HEMA), as well as derivatives thereof, and the like. Hydrogels can be produced that are stable, biodegradable and bioresorbable. Moreover, hydrogel compositions can include subunits that exhibit one or more of these properties.
Bio-compatible hydrogel compositions whose integrity can be controlled through crosslinking are known and are presently preferred for use in the methods of the invention. For example, Hubbell et al., U.S. Pat. No. 5,410,016, which issued on Apr. 25, 1995 and U.S. Pat. No. 5,529,914, which issued on Jun. 25, 1996, disclose water-soluble systems, which are crosslinked block copolymers having a water-soluble central block segment sandwiched between two hydrolytically labile extensions. Such copolymers are further end-capped with photopolymerizable acrylate functionalities. When crosslinked, these systems become hydrogels. The water soluble central block of such copolymers can include poly(ethylene glycol); whereas, the hydrolytically labile extensions can be a poly(α-hydroxy acid), such as polyglycolic acid or polylactic acid. See, Sawhney et al., Macromolecules 26: 581-587 (1993).
In another preferred embodiment, the gel is a thermoreversible gel. Thermoreversible gels including components, such as pluronics, collagen, gelatin, hyalouronic acid, polysaccharides, polyurethane hydrogel, polyurethane-urea hydrogel and combinations thereof are presently preferred.
In yet another exemplary embodiment, the conjugate of the invention includes a component of a liposome. Liposomes can be prepared according to methods known to those skilled in the art, for example, as described in Eppstein et al., U.S. Pat. No. 4,522,811. For example, liposome formulations may be prepared by dissolving appropriate lipid(s) (such as stearoyl phosphatidyl ethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidyl choline, and cholesterol) in an inorganic solvent that is then evaporated, leaving behind a thin film of dried lipid on the surface of the container. An aqueous solution of the active compound or its pharmaceutically acceptable salt is then introduced into the container. The container is then swirled by hand to free lipid material from the sides of the container and to disperse lipid aggregates, thereby forming the liposomal suspension.
The above-recited microparticles and methods of preparing the microparticles are offered by way of example and they are not intended to define the scope of microparticles of use in the present invention. It will be apparent to those of skill in the art that an array of microparticles, fabricated by different methods, is of use in the present invention.
The structural formats discussed above in the context of the water-soluble polymers, both straight-chain and branched are generally applicable with respect to the water-insoluble polymers as well. Thus, for example, the cysteine, serine, dilysine, and trilysine branching cores can be functionalized with two water-insoluble polymer moieties. The methods used to produce these species are generally closely analogous to those used to produce the water-soluble polymers.
In another exemplary embodiment, the modified saccharyl fragment bears a biomolecule. In still further preferred embodiments, the biomolecule is a functional protein, enzyme, antigen, antibody, peptide, nucleic acid (e.g., single nucleotides or nucleosides, oligonucleotides, polynucleotides and single- and higher-stranded nucleic acids), lectin, receptor or a combination thereof.
In a presently preferred embodiment, the modifying group is biotin. In an exemplary embodiment, the selectively biotinylated peptide is elaborated by the attachment of an avidin or streptavidin moiety bearing one or more modifying groups. Preferred biomolecules are essentially non-fluorescent, or emit such a minimal amount of fluorescence that they are inappropriate for use as a fluorescent marker in an assay. Moreover, it is generally preferred to use biomolecules that are not sugars. An exception to this preference is the use of an otherwise naturally occurring sugar that is modified by covalent attachment of another entity (e.g., PEG, biomolecule, therapeutic moiety, diagnostic moiety, etc.). In an exemplary embodiment, a sugar moiety, which is a biomolecule, is conjugated to a linker arm and the sugar-linker arm cassette is subsequently conjugated to a peptide via a method of the invention.
Biomolecules useful in practicing the present invention can be derived from any source. The biomolecules can be isolated from natural sources or they can be produced by synthetic methods. Peptides can be natural peptides or mutated peptides. Mutations can be effected by chemical mutagenesis, site-directed mutagenesis or other means of inducing mutations known to those of skill in the art. Peptides useful in practicing the instant invention include, for example, enzymes, antigens, antibodies and receptors. Antibodies can be either polyclonal or monoclonal.
Both naturally derived and synthetic peptides and nucleic acids are of use in conjunction with the present invention; these molecules can be attached to a sugar residue component or a crosslinking agent by any available reactive group. For example, peptides can be attached through a reactive amine, carboxyl, sulfhydryl, or hydroxyl group. The reactive group can reside at a peptide terminus or at a site internal to the peptide chain. Nucleic acids can be attached through a reactive group on a base (e.g., exocyclic amine) or an available hydroxyl group on a sugar moiety (e.g., 3′- or 5′-hydroxyl). The peptide and nucleic acid chains can be further derivatized at one or more sites to allow for the attachment of appropriate reactive groups onto the chain. See, Chrisey et al. Nucleic Acids Res. 24: 3031-3039 (1996).
In a further preferred embodiment, the biomolecule is selected to direct the peptide modified by the methods of the invention to a specific tissue, thereby enhancing the delivery of the peptide to that tissue relative to the amount of underivatized peptide that is delivered to the tissue. In a still further preferred embodiment, the amount of derivatized peptide delivered to a specific tissue within a selected time period is enhanced by derivatization by at least about 20%, more preferably, at least about 40%, and more preferably still, at least about 100%. Presently, preferred biomolecules for targeting applications include antibodies, hormones and ligands for cell-surface receptors.
II. D. v. Methods of Producing the Polymeric Modifying Groups
The polymeric modifying groups can be activated for reaction with a glycosyl or saccharyl moiety, an amino acid moiety, an amine or with other nucleophiles. Exemplary structures of activated species (e.g., carbonates and active esters) include:
Other activating, or leaving groups, appropriate for activating linear and branched PEGs of use in preparing the compounds set forth herein include, but are not limited to the species:
PEG molecules that are activated with these and other species and methods of making the activated PEGs are set forth in WO 04/083259.
Those of skill in the art will appreciate that one or more of the m-PEG arms of the branched polymers shown above can be replaced by a PEG moiety with a different terminus, e.g., OH, COOH, NH2, C2-C10-alkyl, etc. Moreover, the structures above are readily modified by inserting alkyl linkers (or removing carbon atoms) between the α-carbon atom and the functional group of the amino acid side chain. Thus, “homo” derivatives and higher homologues, as well as lower homologues are within the scope of cores for branched PEGs of use in the present invention.
The branched PEG species set forth herein are readily prepared by methods such as that set forth in the scheme below:
in which Xd is O or S and r is an integer from 1 to 5. The indices e and f are independently selected integers from 1 to 2500. In an exemplary embodiment, one or both of these indices are selected such that the polymer is about 1 kDa, 2 kDa, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa or 80 kDa in molecular weight.
Thus, according to this scheme, a natural or unnatural amino acid is contacted with an activated m-PEG derivative, in this case the tosylate, forming 1 by alkylating the side-chain heteroatom Xd. The mono-functionalize m-PEG amino acid is submitted to N-acylation conditions with a reactive m-PEG derivative, thereby assembling branched m-PEG 2. As one of skill will appreciate, the tosylate leaving group can be replaced with any suitable leaving group, e.g., halogen, mesylate, triflate, etc. Similarly, the reactive carbonate utilized to acylate the amine can be replaced with an active ester, e.g., N-hydroxysuccinimide, etc., or the acid can be activated in situ using a dehydrating agent such as dicyclohexylcarbodiimide, carbonyldiimidazole, etc.
In other exemplary embodiments, the urea moiety is replaced by a group such as an amide.
In addition to providing peptide conjugates that are formed through a chemically or enzymatically added glycosyl linking group, the present invention provides compositions of matter comprising peptide conjugates that are highly homogenous in their substitution patterns. Using the methods of the invention, it is possible to form peptide conjugates in which substantial proportion of the glycosyl linking groups and glycosyl moieties across a population of peptide conjugates are attached to a structurally identical amino acid or glycosyl residue. Thus, in another aspect, the invention provides a peptide conjugate having a population of water-soluble polymer moieties, which are covalently bound to the peptide through a glycosyl linking group, e.g., a modified saccharyl fragment. In a an exemplary peptide conjugate of the invention, essentially each member of the water soluble polymer population is bound via the modified saccharyl fragment to a glycosyl residue of the peptide, and each glycosyl residue of the peptide to which the modified saccharyl fragment is attached has the same structure.
The present invention also provides conjugates analogous to those described above in which the peptide is conjugated to a modifying group, e.g. therapeutic moiety, diagnostic moiety, targeting moiety, toxin moiety or the like via a glycosyl linking group such as a modified saccharyl fragment. Each of the above-recited modifying groups can be a small molecule, natural polymer (e.g., polypeptide) or synthetic polymer. When the modifying group is attached to a sialic acid, it is generally preferred that the modifying group is substantially non-fluorescent.
In an exemplary embodiment, the peptides of the invention include at least one O-linked or N-linked glycosylation site, which is glycosylated with a modified sugar that includes a polymeric modifying group, e.g., a PEG moiety. In an exemplary embodiment, the PEG is covalently attached to the peptide via an intact glycosyl linking group such as a modified saccharyl fragment, or via a non-glycosyl linker, e.g., substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl. The glycosyl linking group is covalently attached to either an amino acid residue or a glycosyl residue of the peptide. Alternatively, the glycosyl linking group is attached to one or more glycosyl units of a glycopeptide. The invention also provides conjugates in which a glycosyl linking group is attached to both an amino acid residue and a glycosyl residue.
In another aspect of the invention, the invention also provides sugar nucleotides. Exemplary species according to this embodiment include:
in which the index y is an integer selected from 0, 1 and 2. Base is a nucleic acid base, such as adenine, thymine, guanine, cytidine and uridine. Y, X1, Y2, R1, R3 and R4 are as described above. In an exemplary embodiment, Y2 or La-(R6a)w is a member selected from
in which the variables are as described above.
In an exemplary embodiment, Y2 or L-(R6a)w has a structure according to the following formula:
In an exemplary embodiment, A1 and A2 are each —OCH3.
In another exemplary embodiment, the nucleotide sugar has a structure according to the following formula:
In addition to the compositions discussed above, the present invention provides methods for preparing modified saccharyl fragments and glyco-conjugates incorporating these fragments. Exemplary methods include synthesizing a modified peptide or lipid using a modified saccharyl fragment, e.g., modified-galactose, -fucose, and -sialic acid. When a modified sialic acid is used, either a sialyltransferase or a trans-sialidase (for α2,3-linked sialic acid only) can be used to transfer the modified fragment onto the acceptor moiety of the substrate.
The method of the invention includes transferring a modified saccharyl fragment from an activated modified saccharyl fragment onto an acceptor moiety of a substrate. Exemplary substrates include peptides and lipids of therapeutic relevance. Exemplary acceptor moieties include amino acid residues, aglycone residues and glycosyl moieties directly or indirectly bound to an amino acid or aglycone residue.
For clarity of illustration, the invention is illustrated with reference to a conjugate formed between a (glyco)peptide a modified saccharyl fragment that is transferred to an acceptor moiety on the (glyco)peptide from an activated modified saccharyl fragment that includes a water-soluble polymer. Those of skill will appreciate that the invention equally encompasses methods of forming conjugates of (glyco)lipids with saccharyl fragments modified with water-soluble polymers, and forming conjugates between (glyco)peptides and (glyco)lipids and saccharyl fragments bearing modifying groups other than water-soluble polymers.
In exemplary embodiments, the conjugate is formed between a water-soluble polymer, a therapeutic moiety, targeting moiety or a biomolecule, and a glycosylated peptide. The polymer, therapeutic moiety or biomolecule is conjugated to the peptide via a glycosyl linking group, which is interposed between, and covalently linked to, both the peptide (directly or through an intervening glycosyl linker) and the modifying group (e.g., water-soluble polymer). The glycosyl linking group includes a modified saccharyl fragment. The method includes contacting the glycopeptide with an activated modified saccharyl fragment and an enzyme for which the activated modified saccharyl fragment is a substrate. The components of the reaction mixture are combined under conditions appropriate to enzymatically tranfer the modified saccharyl fragment from the activated modified saccharyl fragment to an acceptor moiety on the glycopeptide, thereby preparing the conjugate.
The acceptor peptide is typically synthesized de novo, or recombinantly expressed in a prokaryotic cell (e.g., bacterial cell, such as E. coli) or in a eukaryotic cell such as a mammalian, yeast, insect, fungal or plant cell. The peptide can be either a full-length protein or a fragment. Moreover, the peptide can be a wild type or mutated peptide. In an exemplary embodiment, the peptide includes a mutation that adds one or more N- or O-linked glycosylation sites to the peptide sequence.
The method of the invention also provides for modification of incompletely glycosylated peptides that are produced recombinantly. Many recombinantly produced glycoproteins are incompletely glycosylated, exposing carbohydrate residues that may have undesirable properties, e.g., immunogenicity, recognition by the RES. The incomplete glycosyl residue can be masked using a water-soluble polymer.
Exemplary peptides that can be modified using the methods of the invention are set forth in
Peptides modified by the methods of the invention can be synthetic or wild-type peptides or they can be mutated peptides, produced by methods known in the art, such as site-directed mutagenesis. Glycosylation of peptides is typically either N-linked or O-linked. An exemplary N-linkage is the attachment of the modified saccharyl fragment to the side chain of an asparagine residue. The tripeptide sequences asparagine-X-serine and asparagine-X-threonine, where X is any amino acid except proline, are the recognition sequences for enzymatic attachment of a carbohydrate moiety to the asparagine side chain. Thus, the presence of either of these tripeptide sequences in a polypeptide creates a potential glycosylation site. O-linked glycosylation refers to the attachment of one sugar (e.g., N-acetylgalactosamine, galactose, mannose, GlcNAc, glucose, fucose or xylose) to the hydroxy side chain of a hydroxyamino acid, preferably serine or threonine, although unusual or non-natural amino acids, e.g., 5-hydroxyproline or 5-hydroxylysine may also be used.
Moreover, in addition to peptides, the methods of the present invention can be practiced with other biological structures (e.g., glycolipids, lipids, sphingoids, ceramides, whole cells, and the like. In general, the only limitation on the substrate structure is that it includes a glycosylation site).
For substrates lacking a glycosylation site, or for which it is desired to add a further glycosylation site, reliable methods are known in the art. For example, addition of glycosylation sites to a peptide, or other structure, is conveniently accomplished by altering the amino acid sequence such that it contains the desired glycosylation site. The addition may be made by mutation or by full chemical synthesis of the peptide. The peptide amino acid sequence is preferably altered through changes at the DNA level, particularly by mutating the DNA encoding the peptide at preselected bases such that codons are generated that will translate into the desired amino acids. The DNA mutation(s) are preferably made using methods known in the art. Both O-linked and N-linked glycosylation sites can be engineered into a peptide.
In an exemplary embodiment, the glycosylation site is added by shuffling polynucleotides. Polynucleotides encoding a candidate peptide can be modulated with DNA shuffling protocols. DNA shuffling is a process of recursive recombination and mutation, performed by random fragmentation of a pool of related genes, followed by reassembly of the fragments by a polymerase chain reaction-like process. See, e.g., Stemmer, Proc. Natl. Acad. Sci. USA 91: 10747-10751 (1994); Stemmer, Nature 370: 389-391 (1994); and U.S. Pat. Nos. 5,605,793, 5,837,458, 5,830,721 and 5,811,238.
The present invention also provides means of adding (or removing) one or more selected glycosyl residues to a peptide, after which a modified saccharyl fragment is conjugated to at least one of the selected glycosyl residues of the peptide. The present embodiment is useful, for example, when it is desired to conjugate the modified saccharyl fragment to a selected glycosyl residue that is either not present on a peptide or is not present in a desired amount. Thus, prior to coupling a modified saccharyl fragment to a peptide, the selected glycosyl residue is conjugated to the peptide by enzymatic or chemical coupling. In another embodiment, the glycosylation pattern of a glycopeptide is altered prior to the conjugation of the modified saccharyl fragment by the removal of a carbohydrate residue from the glycopeptide. See, for example WO 98/31826.
Addition or removal of any carbohydrate moiety present on the glycopeptide is accomplished either chemically or enzymatically. Chemical deglycosylation is preferably brought about by exposure of the polypeptide variant to the compound trifluoromethanesulfonic acid, or an equivalent compound. This treatment results in the cleavage of most or all sugars except the linking sugar (N-acetylglucosamine or N-acetylgalactosamine), while leaving the peptide intact. Chemical deglycosylation is described by Hakimuddin et al., Arch. Biochem. Biophys. 259: 52 (1987) and by Edge et al., Anal. Biochem. 118:131(1981). Enzymatic cleavage of carbohydrate moieties on polypeptide variants can be achieved by the use of a variety of endo- and exo-glycosidases as described by Thotakura et al., Meth. Enzymol. 138: 350 (1987).
Chemical addition of glycosyl moieties is carried out by any art-recognized method. Enzymatic addition of sugar moieties is preferably achieved using a modification of the methods set forth herein, substituting native glycosyl units for the modified saccharyl fragments used in the invention. Other methods of adding sugar moieties are disclosed in U.S. Pat. No. 5,876,980, 6,030,815, 5,728,554, and 5,922,577.
Exemplary attachment points for selected glycosyl residue include, but are not limited to: (a) consensus sites for N-linked glycosylation, and sites for O-linked glycosylation; (b) terminal glycosyl moieties that are acceptors for a glycosyltransferase; (c) arginine, asparagine and histidine; (d) free carboxyl groups; (e) free sulfhydryl groups such as those of cysteine; (f) free hydroxyl groups such as those of serine, threonine, or hydroxyproline; (g) aromatic residues such as those of phenylalanine, tyrosine, or tryptophan; or (h) the amide group of glutamine. Exemplary methods of use in the present invention are described in WO 87/05330 published Sep. 11, 1987, and in Aplin and Wriston, CRC C
In one embodiment, the invention provides a method for linking two or more peptides through a linking group. The linking group is of any useful structure and may be selected from straight- and branched-chain structures. Preferably, each terminus of the linker, which is attached to a peptide, includes a modified saccharyl fragment.
In an exemplary method of the invention, two peptides are linked together via a linker moiety that includes a polymeric (e.g., PEG linker). The focus on a PEG linker that includes two glycosyl groups is for purposes of clarity and should not be interpreted as limiting the identity of linker arms of use in this embodiment of the invention. In an example of this embodiment, diamino-PEG is converted to a bifunctional linking group by reaction with two saccharyl fragments, e.g., sialic acid aldehyde. The bifunctional linking group is then enzymatically coupled to each peptide. As will be appreciated by those of skill in the art, the saccharyl fragments attached to the PEG moiety can be the same or different.
Exemplary peptides with which the present invention can be practiced, methods of adding or removing glycosylation sites, and adding or removing glycosyl structures or substructures are described in detail in WO03/031464 and related U.S. and PCT applications.
In general, the saccharyl fragment and the modifying group are linked together through the use of reactive groups, which are typically transformed by the linking process into a new organic functional group or unreactive species. The reactive group on the saccharyl fragment in generally formed through a degradative process, e.g., oxidation. In the present invention, the modified saccharyl fragment is generally made by combining an amino analogue of the modifying group with an aldehyde or ketone moiety generated by oxidation of a saccharyl hydroxyl moiety.
In an exemplary embodiment, the method provides for forming a covalent conjugate between a modified saccharyl fragment and a glycosylated or non-glycosylated peptide. The method includes enzymatically transferring the modified saccharyl fragment from an activated modified saccharyl fragment to an acceptor moiety on the peptide. In another exemplary embodiment, the modified saccharyl fragment is covalently attached to a glycosyl residue that is covalently attached to the peptide. In another exemplary embodiment, the modified saccharyl fragment is covalently attached to an amino acid residue of the peptide. In another exemplary embodiment, the enzyme is a glycosyltransferase which is a member selected from sialyltransferases, trans-sialidases, galactosyltransferases, glucosyltransferases, GalNAc transferase, GlcNAc transferase, fucosyltransferases, and mannosyltransferases. In another exemplary embodiment, the glycosyltransferase is recombinant. In another exemplary embodiment, the method is performed in a cell-free environment.
Methods for converting saccharyl hydroxyl moieties into carbonyl-containing compounds are well known in the art. As exemplified by the selective oxidation of the side chain of sialic acid, conditions are generally available for preparing an oxidized saccharyl precursor in a controlled and reproducible fashion.
For example, in the scheme above, selective oxidation of the primary hydroxyl of the sialic acid side chain, followed by reductive amination with m-PEG-NH2 provides the corresponding saccharyl PEG-amine fragment according to route (iii).
Further, mild periodate oxidation (e.g., 1 mM sodium metaperiodate, 0° C.), according to route (i), produces a sialic acid fragment that is incompletely oxidized relative to the fragment resulting from the harsher oxidation conditions of route (ii). The aldehyde is coupled with a modifying group, e.g., amino-m-PEG, under reducing conditions, thereby forming an exemplary sialic acid fragment-m-PEG conjugate.
As shown in route (iv), the oxidized sialic acid can also be reacted with a Wittig, Grignard or lithium reagent to form a species in which the water-soluble polymer and the saccharyl fragment are conjugated through a linker group, Ld. The alkene moiety can be reduced using art-recognized conditions, forming a species in which Ld is linked to the remainder of the saccharyl fragment through a saturated C—C bond. Exemplary linkers include substituted or unsubstituted alkyl and substituted or unsubstituted heteroalkyl moieties.
Route (v) exemplifies a scheme in which the aldhehyde is reductively aminated with ammonia and the resulting amine is acylated with an active m-PEG derivative, e.g., an active ester.
Those of skill in the art will readily appreciate that both routes (iv) and (v) can be practiced with any of the side chain oxidized sialic acid fragments set forth in the scheme.
In addition to the species described above, R1-R4 can also represent or include protecting groups or protected groups. Those of skill in the art understand how to protect a particular functional group such that it does not interfere with a chosen set of reaction conditions. For examples of useful protecting groups, see, for example, Greene et al., P
Although exemplified above by reference to the use of an amine analogue of the modifying group, it is understood that the aldehyde or ketone group of the saccharide is readily modified by via formation of carbonyl derivatives such as, for example, imines, hydrazones, semicarbazones or oximes, or via such mechanisms as Grignard addition or alkyllithium addition. Accordingly, the present invention encompasses modified saccharyl fragments, linking groups and conjugates that include one or more of these derivatives, and is not limited to a particular saccharyl fragment or method of forming the fragment.
Exemplary moieties attached to the conjugates disclosed herein include, but are not limited to, PEG derivatives (e.g., acyl-PEG, acyl-alkyl-PEG, alkyl-acyl-PEG carbamoyl-PEG, aryl-PEG), PPG derivatives (e.g., acyl-PPG, acyl-alkyl-PPG, alkyl-acyl-PPG carbamoyl-PPG, aryl-PPG), therapeutic moieties, diagnostic moieties, mannose-6-phosphate, heparin, heparan, SLex, mannose, mannose-6-phosphate, Sialyl Lewis X, FGF, VFGF, proteins, chondroitin, keratan, dermatan, albumin, integrins, antennary oligosaccharides, peptides and the like. Methods of conjugating the various modifying groups to a saccharide moiety are readily accessible to those of skill in the art (P
Preparation of the modified saccharyl fragment for use in the methods of the present invention includes attachment of a modifying group to a sugar residue and forming a stable adduct, which is a substrate for a glycosyltransferase. Thus, it is often preferred to use a cross-linking agent to conjugate the modifying group and the sugar. Exemplary bifunctional compounds which can be used for attaching modifying groups to carbohydrate moieties include, but are not limited to, bifunctional poly(ethyleneglycols), polyamides, polyethers, polyesters and the like. General approaches for linking carbohydrates to other molecules are known in the literature. See, for example, Lee et al., Biochemistry 28: 1856 (1989); Bhatia et al., Anal. Biochem. 178: 408 (1989); Janda et al., J. Am. Chem. Soc. 112: 8886 (1990) and Bednarski et al., WO 92/18135. In the discussion that follows, the reactive groups are treated as benign on the sugar moiety of the nascent modified saccharyl fragment. The focus of the discussion is for clarity of illustration. Those of skill in the art will appreciate that the discussion is relevant to reactive groups on the modifying group as well.
A variety of reagents are used to modify the components of the modified saccharyl fragment with intramolecular chemical crosslinks (for reviews of crosslinking reagents and crosslinking procedures see: Wold, F., Meth. Enzymol. 25: 623-651, 1972; Weetall, H. H., and Cooney, D. A., In: E
An exemplary cross-linking moiety includes a reactive functional group that reacts with the saccharyl ketone or aldehyde moiety (e.g., amine, hydrazine, etc.). The reactive functional group is tethered to a second reactive functional group that reacts with a moiety on the modifying group, forming a linker covalently bonded to both the saccharyl fragment and the modifying group.
Exemplary cross-linking groups of use in the present invention are set forth in WO03/031464 and related U.S. and PCT applications.
The modified saccharyl fragments are conjugated to a glycosylated or non-glycosylated peptide using an appropriate enzyme to mediate the conjugation. Preferably, the concentrations of the modified donor sugar(s), enzyme(s) and acceptor peptide(s) are selected such that glycosylation proceeds until the acceptor is consumed. The considerations discussed below, while set forth in the context of a sialyltransferase, are generally applicable to other glycosyltransferase reactions.
A number of methods of using glycosyltransferases to synthesize desired oligosaccharide structures are known and are generally applicable to the instant invention. Exemplary methods are described, for instance, WO 96/32491, Ito et al., Pure Appl. Chem. 65: 753 (1993), and U.S. Pat. Nos. 5,352,670, 5,374,541, and 5,545,553.
The present invention is practiced using a single glycosyltransferase or a combination of glycosyltransferases. For example, one can use a combination of a sialyltransferase and a galactosyltransferase. In those embodiments using more than one enzyme, the enzymes and substrates are preferably combined in an initial reaction mixture, or the enzymes and reagents for a second enzymatic reaction are added to the reaction medium once the first enzymatic reaction is complete or nearly complete. By conducting two enzymatic reactions in sequence in a single vessel, overall yields are improved over procedures in which an intermediate species is isolated. Moreover, cleanup and disposal of extra solvents and by-products is reduced.
In a preferred embodiment, each of the first and second enzyme is a glycosyltransferase. In another preferred embodiment, one enzyme is an endoglycosidase. In an additional preferred embodiment, more than two enzymes are used to assemble the modified glycoprotein of the invention. The enzymes are used to alter a saccharide structure on the peptide at any point either before or after the addition of the modified saccharyl fragment to the peptide.
In another preferred embodiment, each of the enzymes utilized to produce a conjugate of the invention are present in a catalytic amount. The catalytic amount of a particular enzyme varies according to the concentration of that enzyme's substrate as well as to reaction conditions such as temperature, time and pH value. Means for determining the catalytic amount for a given enzyme under preselected substrate concentrations and reaction conditions are well known to those of skill in the art.
The temperature at which an above process is carried out can range from just above freezing to the temperature at which the most sensitive enzyme denatures. Preferred temperature ranges are about 0° C. to about 45° C., and more preferably about 20° C. to about 30° C. In another exemplary embodiment, one or more components of the present method are conducted at an elevated temperature using a thermophilic enzyme.
The reaction mixture is maintained for a period of time sufficient for the acceptor to be glycosylated, thereby forming the desired conjugate. Some of the conjugate can often be detected after a few hours, with recoverable amounts usually being obtained within 24 hours or less. Those of skill in the art understand that the rate of reaction is dependent on a number of variable factors (e.g., enzyme concentration, donor concentration, acceptor concentration, temperature, solvent volume), which are optimized for a selected system.
The present invention also provides for the industrial-scale production of modified peptides.
In the discussion that follows, the invention is exemplified by the conjugation of modified sialic acid fragment to a glycosylated peptide. The exemplary modified sialic acid fragment is labeled with PEG. The focus of the following discussion on the use of PEG-modified sialic acid fragments and glycosylated peptides is for clarity of illustration and is not intended to imply that the invention is limited to the conjugation of these two partners. One of skill understands that the discussion is generally applicable to the additions of modified glycosyl fragments other than sialic acid fragments. Moreover, the discussion is equally applicable to the modification of a saccharyl fragment with agents other than PEG including other water-soluble polymers, therapeutic moieties, and biomolecules.
An enzymatic approach can be used for the selective introduction of PEGylated or PPGylated carbohydrates onto a peptide or glycopeptide. The method utilizes modified saccharyl fragments containing PEG, PPG, or a masked reactive functional group, and is combined with the appropriate glycosyltransferase or glycosynthase. By selecting the glycosyltransferase that will make the desired carbohydrate linkage and utilizing the modified saccharyl fragment as the donor substrate, the PEG or PPG can be introduced directly onto the peptide backbone, onto existing sugar residues of a glycopeptide or onto sugar residues that have been added to a peptide.
An acceptor for the sialyltransferase is present on the peptide to be modified by the methods of the present invention either as a naturally occurring structure or one placed there recombinantly, enzymatically or chemically. Suitable acceptors, include, for example, galactosyl acceptors such as GalNAc, Galβ1,4GlcNAc, Galβ1,4GalNAc, Galβ1,3GalNAc, lacto-N-tetraose, Galβ1,3GlcNAc, Galβ1,3Ara, Galβ1,6GlcNAc, Galβ1,4Glc (lactose), and other acceptors known to those of skill in the art (see, e.g., Paulson et al., J. Biol. Chem. 253: 5617-5624 (1978)).
In one embodiment, an acceptor for the sialyltransferase is present on the glycopeptide to be modified upon in vivo synthesis of the glycopeptide. Such glycopeptides can be sialylated using the claimed methods without prior modification of the glycosylation pattern of the glycopeptide. Alternatively, the methods of the invention can be used to sialylate a peptide that does not include a suitable acceptor; one first modifies the peptide to include an acceptor by methods known to those of skill in the art. In an exemplary embodiment, a GalNAc residue is added by the action of a GalNAc transferase.
In an exemplary embodiment, an acceptor for a modified sialic acid fragment is assembled by attaching a galactose residue to an appropriate acceptor linked to the peptide, e.g., a GlcNAc. The method includes incubating the peptide to be modified with a reaction mixture that contains a suitable amount of a galactosyltransferase (e.g., galβ1,3 or galβ1,4), and a suitable galactosyl donor (e.g., UDP-galactose). The reaction is allowed to proceed substantially to completion or, alternatively, the reaction is terminated when a preselected amount of the galactose residue is added. Other methods of assembling a selected saccharide acceptor will be apparent to those of skill in the art.
In yet another embodiment, glycopeptide-linked oligosaccharides are first “trimmed,” either in whole or in part, to expose either an acceptor for the sialyltransferase or a moiety to which one or more appropriate residues can be added to obtain a suitable acceptor. Enzymes such as glycosyltransferases and endoglycosidases (see, for example U.S. Pat. No. 5,716,812) are useful for the attaching and trimming reactions.
In the discussion that follows, the method of the invention is exemplified by the use of modified saccharyl fragments having a water-soluble polymer attached thereto. The focus of the discussion is for clarity of illustration. Those of skill will appreciate that the discussion is equally relevant to those embodiments in which the modified saccharyl fragment bears a therapeutic moiety, biomolecule or the like.
In another exemplary embodiment, a water-soluble polymer is added to one or both of the terminal mannose residues of the biantennary structure via a modified saccharyl fragment having a galactose residue, which is conjugated to a GlcNAc residue added onto the terminal mannose residues. Alternatively, an unmodified Gal can be added to one or both terminal GlcNAc residues.
In yet a further example, a water-soluble polymer is added onto a Gal residue using a modified sialic acid fragment.
The Examples set forth above provide an illustration of the power of the methods set forth herein. Using the methods of the invention, it is possible to “trim back” and build up a carbohydrate residue of substantially any desired structure. The modified saccharyl fragment can be added to the termini of the carbohydrate moiety as set forth above, or it can be intermediate between the peptide core and the terminus of the carbohydrate.
In an exemplary embodiment, an existing sialic acid is removed from a glycopeptide using a sialidase, thereby unmasking all or most of the underlying galactosyl residues. Alternatively, a peptide or glycopeptide is labeled with galactose residues, or an oligosaccharide residue that terminates in a galactose unit. Following the exposure of, or addition of, the galactose residues, an appropriate sialyltransferase is used to add a modified sialic acid. The approach is summarized in Scheme 2.
In which SA* is saccharyl fragment and Y is as described above (Formula I).
In an alternative embodiment, the modified saccharyl fragment is added directly to the peptide backbone using a glycosyltransferase known to transfer sugar residues to the peptide backbone. Use of this approach allows the direct addition of modified saccharyl fragments onto peptides that lack any carbohydrates or, alternatively, onto existing glycopeptides. In both cases, the addition of the modified saccharyl fragment occurs at specific positions on the peptide backbone as defined by the substrate specificity of the glycosyltransferase and not in a random manner as occurs during modification of a protein's peptide backbone using chemical methods. An array of agents can be introduced into proteins or glycopeptides that lack the glycosyltransferase substrate peptide sequence by engineering the appropriate amino acid sequence into the polypeptide chain.
In each of the exemplary embodiments set forth above, one or more additional chemical or enzymatic modification steps can be utilized following the conjugation of the modified saccharyl fragment to the peptide. In an exemplary embodiment, an enzyme (e.g., fucosyltransferase) is used to append a glycosyl unit (e.g., fucose) onto the terminal modified saccharyl fragment attached to the peptide. In another example, an enzymatic reaction is utilized to “cap” sites to which the modified saccharyl fragment failed to conjugate. Alternatively, a chemical reaction is utilized to alter the structure of the conjugated modified saccharyl fragment. For example, the conjugated modified saccharyl fragment is reacted with agents that stabilize or destabilize its linkage with the peptide component to which the modified saccharyl fragment is attached. In another example, a component of the modified saccharyl fragment is deprotected following its conjugation to the peptide. One of skill will appreciate that there is an array of enzymatic and chemical procedures that are useful in the methods of the invention at a stage after the modified saccharyl fragment is conjugated to the peptide. Further elaboration of the modified saccharyl fragment-peptide conjugate is within the scope of the invention.
In another exemplary embodiment, the invention provides a composition for forming a conjugate between a peptide and a modified saccharyl fragment. This composition includes a mixture of an activated modified saccharyl fragment, an enzyme for which the activated modified saccharyl fragment is a substrate, and a peptide acceptor substrate, wherein the modified saccharyl fragment is covalently attached a member selected from water-soluble polymers, therapeutic moieties and biomolecules.
General methods of remodeling peptides and lipids using enzymes that transfer a sugar donor to an acceptor are discussed in detail in DeFrees, WO 03/031464 A2, published Apr. 17, 2003. A brief summary of selected enzymes of use in the present method is set forth below.
Glycosyltransferases catalyze the addition of activated sugars (donor NDP-sugars), in a step-wise fashion, to a protein, glycopeptide, lipid or glycolipid or to the non-reducing end of a growing oligosaccharide. N-linked glycopeptides are synthesized via a transferase and a lipid-linked oligosaccharide donor Dol-PP-NAG2Glc3Mang in an en block transfer followed by trimming of the core. In this case the nature of the “core” saccharide is somewhat different from subsequent attachments. A very large number of glycosyltransferases are known in the art.
The glycosyltransferase to be used in the present invention may be any as long as it can utilize the modified saccharyl fragment as a sugar donor. Examples of such enzymes include Leloir pathway glycosyltransferase, such as galactosyltransferase, N-acetylglucosaminyltransferase, N-acetylgalactosaminyltransferase, fucosyltransferase, sialyltransferase, mannosyltransferase, xylosyltransferase, glucurononyltransferase and the like.
For enzymatic saccharide syntheses that involve glycosyltransferase reactions, glycosyltransferase can be cloned, or isolated from any source. Many cloned glycosyltransferases are known, as are their polynucleotide sequences. See, e.g., “The WWW Guide To Cloned Glycosyltransferases,” Taniguchi et al., 2002, Handbook of Glycosyltransferases and Related Genes, Springer, Tokyo. Glycosyltransferase amino acid sequences and nucleotide sequences encoding glycosyltransferases from which the amino acid sequences can be deduced are also found in various publicly available databases, including GenBank, Swiss-Prot, EMBL, and others.
Glycosyltransferases that can be employed in the methods of the invention include, but are not limited to, galactosyltransferases, fucosyltransferases, glucosyltransferases, N-acetylgalactosaminyltransferases, N-acetylglucosaminyltransferases, glucuronyltransferases, sialyltransferases, mannosyltransferases, glucuronic acid transferases, galacturonic acid transferases, and oligosaccharyltransferases. Suitable glycosyltransferases include those obtained from eukaryotes, as well as from prokaryotes. The enzymes may be wild-type or mutant enzymes. Methods of preparing mutant glycosyltransferases and characterizing these species are known in the art.
In some embodiments, a glycosyltransferase used in the method of the invention is a fucosyltransferase. Fucosyltransferases are known to those of skill in the art. Exemplary fucosyltransferases include enzymes, which transfer L-fucose from GDP-fucose to a hydroxy position of an acceptor sugar. Fucosyltransferases that transfer non-nucleotide sugars to an acceptor are also of use in the present invention.
In some embodiments, the acceptor sugar is, for example, the GlcNAc in a Galβ(1→3,4)GlcNAcβ-group in an oligosaccharide glycoside. Suitable fucosyltransferases for this reaction include the Galβ(1→3,4)GlcNAcpβ1-α(1→3,4)fucosyltransferase (FTIII E.C. No. 2.4.1.65), which was first characterized from human milk (see, Palcic, et al., Carbohydrate Res. 190: 1-11 (1989); Prieels, et al., J. Biol. Chem. 256: 10456-10463 (1981); and Nunez, et al., Can. J. Chem. 59: 2086-2095 (1981)) and the Galβ(1→4)GlcNAcβ-αfucosyltransferases (FTIV, FTV, FTVI) which are found in human serum. FTVII (E.C. No. 2.4.1.65), a sialyl α(2→3)Galβ((1→3)GlcNAcβ fucosyltransferase, has also been characterized. A recombinant form of the Galβ(1→3,4) GlcNAcβ-α(1→3,4)fucosyltransferase has also been characterized (see, Dumas, et al., Bioorg. Med. Letters 1: 425-428 (1991) and Kukowska-Latallo, et al., Genes and Development 4: 1288-1303 (1990)). Other exemplary fucosyltransferases include, for example, α1,2 fucosyltransferase (E.C. No. 2.4.1.69). Enzymatic fucosylation can be carried out by the methods described in Mollicone, et al., Eur. J. Biochem. 191: 169-176 (1990) or U.S. Pat. No. 5,374,655. Cells that are used to produce a fucosyltransferase will also include an enzymatic system for synthesizing GDP-fucose.
In another group of embodiments, the glycosyltransferase is a galactosyltransferase. Exemplary galactosyltransferases include α(1,3) galactosyltransferases (E.C. No. 2.4.1.151, see, e.g., Dabkowski et al., Transplant Proc. 25:2921 (1993) and Yamamoto et al. Nature 345: 229-233 (1990), bovine (GenBank j04989, Joziasse et al., J. Biol. Chem. 264: 14290-14297 (1989)), murine (GenBank m26925; Larsen et al., Proc. Nat'l. Acad Sci. USA 86: 8227-8231 (1989)), porcine (GenBank L36152; Strahan et al., Immunogenetics 41: 101-105 (1995)). Another suitable α1,3 galactosyltransferase is that which is involved in synthesis of the blood group B antigen (EC 2.4.1.37, Yamamoto et al., J. Biol. Chem. 265: 1146-1151 (1990) (human)). Yet a further exemplary galactosyltransferase is core Gal-T1.
Also suitable for use in the methods of the invention are β(1,4) galactosyltransferases, which include, for example, EC 2.4.1.90 (LacNAc synthetase) and EC 2.4.1.22 (lactose synthetase) (bovine (D'Agostaro et al., Eur. J. Biochem. 183: 211-217 (1989)), human (Masri et al., Biochem. Biophys. Res. Commun. 157: 657-663 (1988)), murine (Nakazawa et al., J. Biochem. 104: 165-168 (1988)), as well as E.C. 2.4.1.38 and the ceramide galactosyltransferase (EC 2.4.1.45, Stahl et al., J. Neurosci. Res. 38: 234-242 (1994)). Other suitable galactosyltransferases include, for example, α1,2 galactosyltransferases (from e.g., Schizosaccharomyces pombe, Chapell et al., Mol. Biol. Cell 5: 519-528 (1994)).
Sialyltransferases are another type of glycosyltransferase that is useful in the recombinant cells and reaction mixtures of the invention. Cells that produce recombinant sialyltransferases will also produce CMP-sialic acid, which is a sialic acid donor for sialyltransferases. Examples of sialyltransferases that are suitable for use in the present invention include ST3Gal III (e.g., a rat or human ST3Gal III), ST3Gal IV, ST3Gal I, ST6Gal I, ST3Gal V, ST6Gal II, ST6GalNAc I, ST6GalNAc II, and ST6GalNAc III (the sialyltransferase nomenclature used herein is as described in Tsuji et al., Glycobiology 6: v-xiv (1996)). An exemplary α(2,3)sialyltransferase referred to as α(2,3)sialyltransferase (EC 2.4.99.6) transfers sialic acid to the non-reducing terminal Gal of a Galβ1→3Glc disaccharide or glycoside. See, Van den Eijnden et al., J. Biol. Chem. 256: 3159 (1981), Weinstein et al., J. Biol. Chem. 257: 13845 (1982) and Wen et al., J. Biol. Chem. 267: 21011 (1992). Another exemplary α2,3-sialyltransferase (EC 2.4.99.4) transfers sialic acid to the non-reducing terminal Gal of the disaccharide or glycoside. see, Rearick et al., J. Biol. Chem. 254: 4444 (1979) and Gillespie et al., J. Biol. Chem. 267: 21004 (1992). Further exemplary enzymes include Gal-β-1,4-GlcNAc α-2,6 sialyltransferase (See, Kurosawa et al. Eur. J. Biochem. 219: 375-381 (1994)).
A list of sialyltransferases of use in the invention are provided in
N-acetylgalactosaminyltransferases are of use in practicing the present invention, particularly for binding a GalNAc moiety to an amino acid of the O-linked glycosylation site of the peptide. Suitable N-acetylgalactosaminyltransferases include, but are not limited to, α(1,3) N-acetylgalactosaminyltransferase, β(1,4) N-acetylgalactosaminyltransferases (Nagata et al., J. Biol. Chem. 267: 12082-12089 (1992) and Smith et al., J. Biol Chem. 269: 15162 (1994)) and polypeptide N-acetylgalactosaminyltransferase (Homa et al., J. Biol. Chem. 268: 12609 (1993)). See also the work of W. Wakarchuk generally and U.S. Pat. No. 6,723,545; and published U.S. Patent Application No. 2003/0180928; 2003/0157658; 2003/0157657; and 2003/0157656.
Production of proteins such as the enzyme GalNAc TI-XX from cloned genes by genetic engineering is well known. See, e.g., U.S. Pat. No. 4,761,371. One method involves collection of sufficient samples, then the amino acid sequence of the enzyme is determined by N-terminal sequencing. This information is then used to isolate a cDNA clone encoding a full-length (membrane bound) transferase which upon expression in the insect cell line Sf9 resulted in the synthesis of a fully active enzyme. The acceptor specificity of the enzyme is then determined using a semiquantitative analysis of the amino acids surrounding known glycosylation sites in 16 different proteins followed by in vitro glycosylation studies of synthetic peptides. This work has demonstrated that certain amino acid residues are overrepresented in glycosylated peptide segments and that residues in specific positions surrounding glycosylated serine and threonine residues may have a more marked influence on acceptor efficiency than other amino acid moieties.
In another embodiment, the enzymes utilized in the method of the invention are cell-bound glycosyltransferases. Although many soluble glycosyltransferases are known (see, for example, U.S. Pat. No. 5,032,519), glycosyltransferases are generally in membrane-bound form when associated with cells. Many of the membrane-bound enzymes studied thus far are considered to be intrinsic proteins; that is, they are not released from the membranes by sonication and require detergents for solubilization. Surface glycosyltransferases have been identified on the surfaces of vertebrate and invertebrate cells, and it has also been recognized that these surface transferases maintain catalytic activity under physiological conditions. However, the more recognized function of cell surface glycosyltransferases is for intercellular recognition (Roth, M
Methods have been developed to alter the glycosyltransferases expressed by cells. For example, Larsen et al., Proc. Natl. Acad. Sci. USA 86: 8227-8231 (1989), report a genetic approach to isolate cloned cDNA sequences that determine expression of cell surface oligosaccharide structures and their cognate glycosyltransferases. A cDNA library generated from mRNA isolated from a murine cell line known to express UDP-galactose:.β.-D-galactosyl-1,4-N-acetyl-D-glucosaminide α-1,3-galactosyltransferase was transfected into COS-1 cells. The transfected cells were then cultured and assayed for α1-3 galactosyltransferase activity.
Francisco et al., Proc. Natl. Acad. Sci. USA 89: 2713-2717 (1992), disclose a method of anchoring β-lactamase to the external surface of Escherichia coli. A tripartite fusion consisting of (i) a signal sequence of an outer membrane protein, (ii) a membrane-spanning section of an outer membrane protein, and (iii) a complete mature β-lactamase sequence is produced resulting in an active surface bound β-lactamase molecule. However, the Francisco method is limited only to procaryotic cell systems and as recognized by the authors, requires the complete tripartite fusion for proper functioning.
The invention also provides methods for producing peptides that include sulfated molecules, including, for example sulfated polysaccharides such as heparin, heparan sulfate, carragenen, and related compounds. Suitable sulfotransferases include, for example, chondroitin-6-sulphotransferase (chicken cDNA described by Fukuta et al., J. Biol. Chem. 270: 18575-18580 (1995); GenBank Accession No. D49915), glycosaminoglycan N-acetylglucosamine N-deacetylase/N-sulphotransferase 1 (Dixon et al., Genomics 26: 239-241 (1995); UL18918), and glycosaminoglycan N-acetylglucosamine N-deacetylase/N-sulphotransferase 2 (murine cDNA described in Orellana et al., J. Biol. Chem. 269: 2270-2276 (1994) and Eriksson et al., J. Biol. Chem. 269: 10438-10443 (1994); human cDNA described in GenBank Accession No. U2304).
This invention also encompasses the use of wild-type and mutant glycosidases. Mutant β-galactosidase enzymes have been demonstrated to catalyze the formation of disaccharides through the coupling of an a-glycosyl fluoride to a galactosyl acceptor molecule. (Withers, U.S. Pat. No. 6,284,494; issued Sep. 4, 2001). Other glycosidases of use in this invention include, for example, β-glucosidases, β-galactosidases, β-mannosidases, β-acetyl glucosaminidases, β-N-acetyl galactosaminidases, β-xylosidases, β-fucosidases, cellulases, xylanases, galactanases, mannanases, hemicellulases, amylases, glucoamylases, α-glucosidases, α-galactosidases, α-mannosidases, α-N-acetyl glucosaminidases, α-N-acetyl galactose-aminidases, α-xylosidases, α-fucosidases, and neuraminidases/sialidases.
The present invention also provides for the use of enzymes that are immobilized on a solid and/or soluble support. In an exemplary embodiment, there is provided a glycosyltransferase that is conjugated to a PEG via an intact glycosyl linker according to the methods of the invention. The PEG-linker-enzyme conjugate is optionally attached to solid support. The use of solid supported enzymes in the methods of the invention simplifies the work up of the reaction mixture and purification of the reaction product, and also enables the facile recovery of the enzyme. The glycosyltransferase conjugate is utilized in the methods of the invention. Other combinations of enzymes and supports will be apparent to those of skill in the art.
The products produced by the above processes can be used without purification. However, it is usually preferred to recover the product. Standard, well-known techniques for recovery of modified peptides such as thin or thick layer chromatography, column chromatography, ion exchange chromatography, or membrane filtration can be used. It is preferred to use membrane filtration, more preferably utilizing a reverse osmotic membrane, or one or more column chromatographic techniques for the recovery as is discussed hereinafter and in the literature cited herein. For instance, membrane filtration wherein the membranes have molecular weight cutoff of about 3000 to about 10,000 can be used to remove proteins such as glycosyl transferases. Nanofiltration or reverse osmosis can then be used to remove salts and/or purify the conjugates (see, e.g., WO 98/15581). Nanofilter membranes are a class of reverse osmosis membranes that pass monovalent salts but retain polyvalent salts and uncharged solutes larger than about 100 to about 2,000 Daltons, depending upon the membrane used. Thus, in a typical application, conjugates prepared by the methods of the present invention will be retained in the membrane and contaminating salts will pass through.
If the modified glycoprotein is produced intracellularly, as a first step, the particulate debris, either host cells or lysed fragments, is removed, for example, by centrifugation or ultrafiltration; optionally, the protein may be concentrated with a commercially available protein concentration filter, followed by separating the polypeptide variant from other impurities by one or more steps selected from immunoaffinity chromatography, ion-exchange column fractionation (e.g., on diethylaminoethyl (DEAE) or matrices containing carboxymethyl or sulfopropyl groups), chromatography on Blue-Sepharose, CM Blue-Sepharose, MONO-Q, MONO-S, lentil lectin-Sepharose, WGA-Sepharose, Con A-Sepharose, Ether Toyopearl, Butyl Toyopearl, Phenyl Toyopearl, or protein A Sepharose, SDS-PAGE chromatography, silica chromatography, chromatofocusing, reverse phase HPLC (e.g., silica gel with appended aliphatic groups), gel filtration using, e.g., Sephadex molecular sieve or size-exclusion chromatography, chromatography on columns that selectively bind the polypeptide, and ethanol or ammonium sulfate precipitation.
Modified glycopeptides produced in culture are usually isolated by initial extraction from cells, enzymes, etc., followed by one or more concentration, salting-out, aqueous ion-exchange, or size-exclusion chromatography steps. Additionally, the modified glycoprotein may be purified by affinity chromatography. Finally, HPLC may be employed for final purification steps.
A protease inhibitor, e.g., methylsulfonylfluoride (PMSF) may be included in any of the foregoing steps to inhibit proteolysis and antibiotics may be included to prevent the growth of adventitious contaminants.
In another method, supernatants from systems that produce the modified glycopeptide of the invention are first concentrated using a commercially available protein concentration filter, for example, an Amicon or Millipore Pellicon ultrafiltration unit. Following the concentration step, the concentrate may be applied to a suitable purification matrix. For example, a suitable affinity matrix may comprise a ligand for the peptide, a lectin or antibody molecule bound to a suitable support. Alternatively, an anion-exchange resin may be employed, for example, a matrix or substrate having pendant DEAE groups. Suitable matrices include acrylamide, agarose, dextran, cellulose, or other types commonly employed in protein purification. Alternatively, a cation-exchange step may be employed. Suitable cation exchangers include various insoluble matrices comprising sulfopropyl or carboxymethyl groups. Sulfopropyl groups are particularly preferred.
Finally, one or more RP-HPLC steps employing hydrophobic RP-HPLC media, e.g., silica gel having pendant methyl or other aliphatic groups, may be employed to further purify a polypeptide variant composition. Some or all of the foregoing purification steps, in various combinations, can also be employed to provide a homogeneous modified glycoprotein.
The modified glycopeptide of the invention resulting from a large-scale fermentation may be purified by methods analogous to those disclosed by Urdal et al., J. Chromatog. 296: 171 (1984). This reference describes two sequential, RP-HPLC steps for purification of recombinant human IL-2 on a preparative HPLC column. Alternatively, techniques such as affinity chromatography may be utilized to purify the modified glycoprotein.
In another aspect, the invention provides a pharmaceutical composition. The pharmaceutical composition includes a pharmaceutically acceptable carrier and a conjugate between a glycosylated or non-glycosylated peptide and a modified saccharyl fragment which is covalently linked to a water-soluble or -insoluble polymer, therapeutic moiety or biomolecule. The polymer, therapeutic moiety or biomolecule is conjugated to the peptide via an intact glycosyl linking group interposed between and covalently linked to both the peptide and the polymer, therapeutic moiety or biomolecule.
Pharmaceutical compositions of the invention are suitable for use in a variety of drug delivery systems. Suitable formulations for use in the present invention are found in Remington's Pharmaceutical Sciences, Mace Publishing Company, Philadelphia, Pa., 17th ed. (1985). For a brief review of methods for drug delivery, see, Langer, Science 249:1527-1533 (1990).
The pharmaceutical compositions may be formulated for any appropriate manner of administration, including for example, topical, oral, nasal, intravenous, intracranial, intraperitoneal, subcutaneous or intramuscular administration. For parenteral administration, such as subcutaneous injection, the carrier preferably comprises water, saline, alcohol, a fat, a wax or a buffer. For oral administration, any of the above carriers or a solid carrier, such as mannitol, lactose, starch, magnesium stearate, sodium saccharine, talcum, cellulose, glucose, sucrose, and magnesium carbonate, may be employed. Biodegradable microspheres (e.g., polylactate polyglycolate) may also be employed as carriers for the pharmaceutical compositions of this invention. Suitable biodegradable microspheres are disclosed, for example, in U.S. Pat. Nos. 4,897,268 and 5,075,109.
Commonly, the pharmaceutical compositions are administered parenterally, e.g., intravenously. Thus, the invention provides compositions for parenteral administration which comprise the compound dissolved or suspended in an acceptable carrier, preferably an aqueous carrier, e.g., water, buffered water, saline, PBS and the like. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions, such as pH adjusting and buffering agents, tonicity adjusting agents, wetting agents, detergents and the like.
These compositions may be sterilized by conventional sterilization techniques, or may be sterile filtered. The resulting aqueous solutions may be packaged for use as is, or lyophilized, the lyophilized preparation being combined with a sterile aqueous carrier prior to administration. The pH of the preparations typically will be between 3 and 11, more preferably from 5 to 9 and most preferably from 7 and 8.
In some embodiments the glycopeptides of the invention can be incorporated into liposomes formed from standard vesicle-forming lipids. A variety of methods are available for preparing liposomes, as described in, e.g., Szoka et al., Ann. Rev. Biophys. Bioeng. 9: 467 (1980), U.S. Pat. Nos. 4,235,871, 4,501,728 and 4,837,028. The targeting of liposomes using a variety of targeting agents (e.g., the sialyl galactosides of the invention) is well known in the art (see, e.g., U.S. Pat. Nos. 4,957,773 and 4,603,044).
Standard methods for coupling targeting agents to liposomes can be used. These methods generally involve incorporation into liposomes of lipid components, such as phosphatidylethanolamine, which can be activated for attachment of targeting agents, or derivatized lipophilic compounds, such as lipid-derivatized glycopeptides of the invention.
Targeting mechanisms generally require that the targeting agents be positioned on the surface of the liposome in such a manner that the target moieties are available for interaction with the target, for example, a cell surface receptor. The carbohydrates of the invention may be attached to a lipid molecule before the liposome is formed using methods known to those of skill in the art (e.g., alkylation or acylation of a hydroxyl group present on the carbohydrate with a long chain alkyl halide or with a fatty acid, respectively). Alternatively, the liposome may be fashioned in such a way that a connector portion is first incorporated into the membrane at the time of forming the membrane. The connector portion must have a lipophilic portion, which is firmly embedded and anchored in the membrane. It must also have a reactive portion, which is chemically available on the aqueous surface of the liposome. The reactive portion is selected so that it will be chemically suitable to form a stable chemical bond with the targeting agent or carbohydrate, which is added later. In some cases it is possible to attach the target agent to the connector molecule directly, but in most instances it is more suitable to use a third molecule to act as a chemical bridge, thus linking the connector molecule which is in the membrane with the target agent or carbohydrate which is extended, three dimensionally, off of the vesicle surface.
The compounds prepared by the methods of the invention may also find use as diagnostic reagents. For example, labeled compounds can be used to locate areas of inflammation or tumor metastasis in a patient suspected of having an inflammation. For this use, the compounds can be labeled with 25I, 14C, or tritium.
Moreover, the invention provides methods of preventing, curing or ameliorating a disease state by administering a conjugate of the invention to a subject at risk of developing the disease or to a subject that has the disease. The conjugate is administered in a therapeutically effective amount. Because many of the conjugates, particularly those that include a polymeric modifying group, are anticipated to display enhanced in vivo residence times, a therapeutically effective dosage is readily determinable from a dosage of the non-conjugated therapeutic agent typically administered.
It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.
The present application is a U.S. National Phase of PCT Patent No. PCT/US06/00282 filed Jan. 6, 2006 and claims priority to U.S. Provisional Patent Application No. 60/641,956, filed Jan. 6, 2005, each of which is incorporated herein by reference in their entirety for all purposes.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US06/00282 | 1/6/2006 | WO | 00 | 8/11/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60641956 | Jan 2005 | US |
