Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-18
2002-04-23
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S409000, C525S413000, C528S094000, C524S091000, C523S406000, C548S257000, C546S272400
Reexamination Certificate
active
06376604
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to activated poly(ethylene glycol) derivatives and methods of preparing such derivatives.
BACKGROUND OF THE INVENTION
Covalent attachment of the hydrophilic polymer poly(ethylene glycol), abbreviated PEG, also known as poly(ethylene oxide), abbreviated PEO, to molecules and surfaces is of considerable utility in biotechnology and medicine. In its most common form, PEG is a linear polymer terminated at each end with hydroxyl groups:
HO—CH
2
CH
2
O—(CH
2
CH
2
O)
n
—CH
2
CH
2
—OH
The above polymer, alpha-,omega-dihydroxylpoly(ethylene glycol), can be represented in brief form as HO-PEG-OH where it is understood that the -PEG- symbol represents the following structural unit:
—CH
2
CH
2
O—(CH
2
CH
2
O)
n
—CH
2
CH
2
—
where n typically ranges from about 3 to about 4000.
PEG is commonly used as methoxy-PEG-OH, or mPEG in brief, in which one terminus is the relatively inert methoxy group, while the other terminus is a hydroxyl group that is subject to ready chemical modification. The structure of mPEG is given below.
CH
3
O—(CH
2
CH
2
O)
n
—(CH
2
CH
2
—OH
Random or block copolymers of ethylene oxide and propylene oxide, shown below, are closely related to PEG in their chemistry, and they can be substituted for PEG in many of its applications.
HO—CH
2
CHRO(CH
2
CHRO)
n
CH
2
CHR—OH
wherein each R is independently H or CH
3
.
PEG is a polymer having the properties of solubility in water and in many organic solvents, lack of toxicity, and lack of immunogenicity. One use of PEG is to covalently attach the polymer to insoluble molecules to make the resulting PEG-molecule “conjugate” soluble. For example, it has been shown that the water-insoluble drug paclitaxel, when coupled to PEG, becomes water-soluble. Greenwald, et al.,
J. Org. Chem.,
60:331-336 (1995).
To couple PEG to a molecule, such as a protein, it is often necessary to “activate” the PEG by preparing a derivative of the PEG having a functional group at a terminus thereof The functional group can react with certain moieties on the protein, such as an amino group, thus forming a PEG-protein conjugate.
In U.S. Pat. No. 5,650,234, which is incorporated by reference herein in its entirety, a 1-benzotriazolylcarbonate ester of poly(ethylene glycol) is described. The multi-step process described in the '234 patent for forming the 1-benzotriazolylcarbonate ester of PEG includes reaction of a PEG molecule with the volatile and hazardous compound, phosgene, in order to form a PEG chloroformate intermediate. The use of phosgene in the process results in the formation of HCl, which can cause degradation of the PEG backbone. Due to the volatile nature of phosgene, and the resulting safety and quality problems associated with its use, there is a need in the art for a method for preparing 1-benzotriazolylcarbonate esters of PEG without using phosgene.
SUMMARY OF THE INVENTION
The invention provides a method for the preparation of a 1-benzotriazolylcarbonate ester of a water-soluble and non-peptidic polymer by reacting the polymer with di(1-benzotriazolyl)carbonate. Using the invention, the 1-benzotriazolylcarbonate ester can be formed in a single step and without using phosgene, thereby avoiding the safety and quality problems associated with that compound.
The method of the invention includes providing a water-soluble and non-peptidic polymer having at least one terminal hydroxyl group and reacting the terminal hydroxyl group of the water-soluble and non-peptidic polymer with di(1-benzotriazolyl)carbonate to form the 1-benzotriazolylcarbonate ester of the water-soluble and non-peptidic polymer. Examples of suitable water-soluble and non-peptidic polymers include poly(alkylene glycol), poly(oxyethylated polyol), poly(olefinic alcohol), poly(vinylpyrrolidone), poly(hydroxypropylmethacrylamide), poly(a-hydroxy acid), poly(vinyl alcohol), polyphosphazene, polyoxazoline, poly(N-acryloylmorpholine), and copolymers, terpolymers, and mixtures thereof. In one embodiment, the polymer is poly(ethylene glycol) having an average molecular weight from about 200 Da to about 100,000 Da.
The reaction step can be conducted in the presence of an organic solvent and a base. Examples of suitable organic solvents include methylene chloride, chloroform, acetonitrile, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and mixtures thereof The base can be, for example, pyridine, dimethylaminopyridine, quinoline, trialkylamines, and mixtures thereof. The method of the invention can further include reacting the 1-benzotriazolylcarbonate ester of the water-soluble and non-peptidic polymer with the amino groups of a second polymer having a plurality of primary amino groups, such as a protein, poly(ethylene glycol), aminocarbohydrates, or poly(vinylamine), to form a cross-linked polymer. Additionally, the 1-benzotriazolylcarbonate ester can be reacted with either an amino acid, such as lysine, to form a polymeric amino acid derivative, or a biologically active agent to form a biologically active polymer conjugate.
DETAILED DESCRIPTION OF THE INVENTION
The terms “functional group”, “active moiety”, “activating group”, “reactive site”, “chemically reactive group” and “chemically reactive moiety” are used in the art and herein to refer to distinct, definable portions or units of a molecule. The terms are somewhat synonymous in the chemical arts and are used herein to indicate that the portions of molecules that perform some function or activity and are reactive with other molecules. The term “active,” when uses in conjunction with functional groups, is intended to include those functional groups that react readily with electrophilic or nucleophilic groups on other molecules, in contrast to those groups that require strong catalysts or highly impractical reaction conditions in order to react. For example, as would be understood in the art, the term “active ester” would include those esters that react readily with nucleophilic groups such as amines. Typically, an active ester will react with an amine in aqueous medium in a matter of minutes, whereas certain esters, such as methyl or ethyl esters, require a strong catalyst in order to react with a nucleophilic group.
The term “linkage” or “linker” is used herein to refer to groups or bonds that normally are formed as the result of a chemical reaction and typically are covalent linkages. Hydrolytically stable linkages means that the linkages are substantially stable in water and do not react with water at useful pHs, e.g., under physiological conditions for an extended period of time, perhaps even indefinitely. Hydrolytically unstable or degradable linkages means that the linkages are degradable in water or in aqueous solutions, including for example, blood. Enzymatically unstable or degradable linkages means that the linkage can be degraded by one or more enzymes. As understood in the art, PEG and related polymers may include degradable linkages in the polymer backbone or in the linker group between the polymer backbone and one or more of the terminal functional groups of the polymer molecule.
The term “biologically active molecule”, “biologically active moiety” or “biologically active agent” when used herein means any substance which can affect any physical or biochemical properties of a biological organism, including but not limited to viruses, bacteria, fungi, plants, animals, and humans. In particular, as used herein, biologically active molecules include any substance intended for diagnosis, cure mitigation, treatment, or prevention of disease in humans or other animals, or to otherwise enhance physical or mental well-being of humans or animals. Examples of biologically active molecules include, but are not limited to, peptides, proteins, enzymes, small molecule drugs, dyes, lipids, nucleosides, oligonucleotides, cells, viruses, liposomes, microparticles and micelles. Classes of biologically active agents that are suitable for use with the invention include, but are not limited to, antibiotics, fungicides, anti-viral agents, anti-inflammatory agents, anti-tumor agen
Alston & Bird LLP
Asinovsky Olga
Seidleck James J.
Shearwater Corporation
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