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Title:
HYDROLYTICALLY DEGRADABLE POLY (ETHYLENE GLYCOL) DERIVATIVES THROUGH INTRODUCTION OF UNSATURATED METHYLENE ETHYLENE OXIDE REPEAT UNITS
Document Type and Number:
WIPO Patent Application WO/2013/154753
Kind Code:
A1
Abstract:
Reactive and hydrolytically-degradable poly(alkylene oxide) derivatives and methods for their synthesis are described herein. These polymers differ from poly(alkylene oxide) by the controlled incorporation of degradable repeat units together with alkylene oxide units. The degradable polymers contain vinyl ether degradable units (e.g., methylene ethylene oxide) incorporated into a polyalkylene backbone (e.g., ethylene oxide, propylene oxide, butylene oxide, other alkylene oxides, glycidol, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other repeat units derived among the glycidyl ethers). The alkylene oxides and glycidyl ethers may be racemic mixtures, enantiomerically enriched, or enantiomerically pure. The degradable polymers disclosed herein can be used in applications where hydrolytic degradability under physiological, or physiological-like conditions is desirable, such as pharmaceutical and cosmetic formulations and degradable devices.

Inventors:
HAWKER CRAIG J (US)
LYND NATHANIEL A (US)
VAN DEN BERG SEBASTIAN (NL)
LEE BONGJAE F (US)
LUNDBERG PONTUS (US)
PRESSLY ERIC D (US)
Application Number:
PCT/US2013/031882
Publication Date:
October 17, 2013
Filing Date:
March 15, 2013
Export Citation:
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Assignee:
UNIV CALIFORNIA (US)
International Classes:
C08G65/00
Domestic Patent References:
WO2010059883A12010-05-27
WO1999022770A11999-05-14
Other References:
CHRISTINE MANGOLD ET AL: "PEG-based Multifunctional Polyethers with Highly Reactive Vinyl-Ether Side Chains for Click-Type Functionalization", MACROMOLECULES, vol. 44, 2011, pages 6326 - 6334, XP002697338
LOONTJENS T ET AL: "BLOCK COPOLYMERS OF POLY(VINYL ETHERS) AND POLY(ETHYLENE GLYCOL) BY MEANS OF THE LIVING CATIONIC POLYMERIZATION OF VINYL ETHERS", POLYMER BULLETIN, SPRINGER, HEIDELBERG, DE, vol. 27, no. 5, 1 January 1992 (1992-01-01), pages 519 - 526, XP000259922, ISSN: 0170-0839, DOI: 10.1007/BF00300599
ZGOLA-GRZESKOWIAK ET AL: "Comparison of biodegradation of poly(ethylene glycol)s and poly(propylene glycol)s", CHEMOSPHERE, PERGAMON PRESS, OXFORD, GB, vol. 64, no. 5, 1 July 2006 (2006-07-01), pages 803 - 809, XP005531148, ISSN: 0045-6535, DOI: 10.1016/J.CHEMOSPHERE.2005.10.056
J. R. HAINES ET AL: "Microbial Degradation of Polyethylene Glycols", APPLIED MICROBIOLOGY, 1975, pages 621 - 625, XP002697339
YAMAOKA ET AL., JOURNAL OF PHARMACEUTICAL SCIENCES, vol. 83, 1994, pages 601 - 606
REID ET AL., MACROMOLECULES, vol. 43, 2010, pages 9588 - 9590
LEE ET AL.: "Poly(ethylene oxide sulfide): New Poly(ethylene glycol) Derivatives Degradable in Reductive Conditions", BIOMACROMOLECULES, vol. 6, 2005, pages 24 - 26
METZKE ET AL., JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 125, 2003, pages 7760 - 7761
VERONESE; PASUT, DRUG DISCOVERY TODAY, vol. 10, 2005, pages 1451 - 1458
LUNDBERG ET AL., ACS MACRO LETT., vol. 1, 2012, pages 1240 - 1243
LEIBOVITCH ET AL., PROGRESS IN POLYMER SCIENCE, vol. 230, 1991, pages 349 - 385
Attorney, Agent or Firm:
PABST, Patrea L. et al. (1545 Peachtree Street N.E.,Suite 32, Atlanta GA, US)
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Claims:
We claim:

1. A hydro lytically degradable poly(alkylene oxide) copolymer comprising:

alkylene oxide non-degradable units and vinyl ether degradable units, wherein the mole percent of the degradable units ranges from about 0.001 to about 25 mole percent.

2. The copolymer of claim 1, wherein the alkylene oxide units are selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, or other alkylene oxides, or from among glycidol, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other glycidyl ethers, or a-di- or mono-substituted glycidyl ethers.

3. The copolymer of claim 1, wherein the polymer has the following formula

wherein the units denoted by y are the degradable vinyl ether repeat units, and the units denoted by x are the non-degradable poly(alkylene oxide) repeat units,

wherein Ri, R2, R3, R4, R5, R6, R7, Rs, R9, and Rio are each independently selected from a group consisting of hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, amines, amides, activated-ester, alkene, vinyl, allyl, alkyne, maleimide, NHS-ester, tosyl, a polymer, or combinations thereof or conventional functional groups used in PEGylation

and where y is between 0.001 and 25 mole percent, and x = 100 -y mole percent.

4. The copolymer of claim 3, wherein y is between 0.001 and 10 mole percent, preferably between 0.01 and 1 mole percent.

5. The copolymer of claim 3, wherein R1-R10 are each independently selected from the group consisting of azides, activated-esters, NHS-ester, tosyl, alkynes, polymers, methyl, ethyl, maleimides, alkyl, alkoxy, n-hydroxy succinimate, 4-nitrophenolate, alkenes, and ethers, and combinations thereof.

6. The copolymer of claim 3, wherein each of R3, R4, R5, Re, R7, Rs, R9, and Rio is hydrogen.

7. The copolymer of claim 3, further comprising a repeat unit structure selected from the group consisting of ethylene oxide, methylene ethylene oxide, alkyl oxide, glycidol, alkylene oxides, glycidyl-functional amines, glycidyl ethers, and a-di- or mono-substituted glycidyl ethers.

8. The copolymer of claim 7, wherein the polymer has the following formula:

wherein,

D is independently selected from the group consisting of propylene oxide, ethylene oxide, butylene oxide, or other alkylene oxides, or from a glycidol derivative, for example, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other glycidyl ethers, or a-di- or mono-substituted glycidyl ethers, wherein D is optionally independently substituted with one or more substituents independently selected from the group consisting hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, activated- ester, alkyne, a polymer, or combinations thereof;

Ri, R2, R3, R4, R5, R6, R7, Re, R9, and Rio are each independently selected from hydrogen, halogen, cyano, maleimide, NHS-ester, azide, alkyl, aryl, ester, ether, azide, activated-ester, alkyne, alkene, a polymer, or combinations thereof, or conventional functional groups used in PEGylation; and where m is between 0.001 and 99.998 mole percent; y is between 0.001 and 25 mole percent, and x = 100 -(y+m).

9. The copolymer of claim 7, wherein the polymer has the following structure

Formula III

wherein,

Ri, R2, R3, R4, R5, Re, 7, Rs, R9, Rio, R11, R12, R13, and R14 are each independently selected from a group consisting of hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, activated-ester, alkyne, alkene, maleimide, NHS-ester, tosyl, a polymer, or combinations thereof, or conventional functional groups used in PEGylation of pharmaceuticals or peptides;

and where x is between 0.001 and 99.998 mole percent; y is between 0.001 and 25 mole percent , and z = 100 -(x+p) mole percent, preferably y is between about 0.001 and 25 mole percent, more preferably y is from 0.01 to about 1 mole percent.

10. The copolymer of claim 7, wherein the copolymer is non-linear.

1 1. The copolymer of any one of claims 2 to 10, wherein R3 is derived from structural motifs with the formula -CH2-O-R4, and wherein R4 is selected from the group consisting of vinyl, allyl, alkyne, maleimide, NHS- ester, or any group used for conventional PEGylation reactions for targeting, imaging, or linked to therapeutic agents.

12. The copolymer of any one of claims 1 to 1 1, wherein the copolymer hydrolytically degrades at a pH ranging from 1 to 8, more preferably from about pH 5 to 7.4.

13. The copolymer of any one of claims 1 to 12, wherein the molecular weight of the degradation products varies as a function of the number of degradable vinyl ether units incorporated in the copolymer.

14. The copolymer of claim 13, wherein the molecular weight of the degradation products ranges from about 40,000 g/mol to about 500 g/mol.

15. The copolymer of any one of claims 8 to 10, wherein the end groups of the degradation products are non-acidic.

16. A method of making the degradable poly(alkylene oxide) polymers of any one of claims 1 to 15, using lewis acid catalyzed activated-monomer polymerization or anionic ring-opening polymerization.

17. The method of claim 16, wherein the lewis acid is trialkylaluminium.

18. The method of any one of claims 16 and 17, wherein the non- degradable starting materials are selected from the group consisting ethylene oxide, propylene oxide, butylene oxide, or other alkylene oxides, or from among glycidol, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other glycidyl ethers, or a-di- or mono-substituted glycidyl ethers; and the dedegradable starting material is a vinyl ether monomer.

19. A hydro lyrically degradable hydrogel comprising a degradable copolymer of any one of claims 1 to 15 crosslinked with a biocompatible macromolecule selected from the group consisting of proteins, modified proteins, peptides, aminocarbohydrates, glycosaminoglycans, aminolipids, poly(vinylamine), polylysine, and poly(ethylene glycol) amines.

20. A pharmaceutical composition comprising the degradable copolymer of any one of claims 1 to 15 linked to a conventional pharmaceutical or a peptide.

21. A medical device for use in a biodegradable implant comprising the degradable copolymer of any one of claims 1 to 15.

Description:
HYDROLYTICALLY DEGRADABLE POLY(ETHYLENE GLYCOL) DERIVATIVES THROUGH INTRODUCTION OF UNSATURATED METHYLENE ETHYLENE OXIDE REPEAT UNITS CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/623,168, entitled "Hydrolytically Degradable Poly(ethylene glycol) Derivatives Through Introduction of Unsaturated Methylene Ethylene Oxide Repeat Units", filed April 12, 2012, the disclosure of which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED

RESEARCH OR DEVELOPMENT

This invention was made with Government Support under grant No. HHSN268201000046C awarded to University of California, Santa Barbara by the National Heart, Lung, and Blood Institute. The Government has certain rights in the invention.

FIELD OF THE INVENTION

The invention relates to poly(ethylene glycol) derivatives, more particularly, to the synthesis of poly(ethylene glycol) derivatives using polymerization and post-polymerization functionalization.

BACKGROUND OF THE INVENTION

Polyethylene glycolization (PEGylation) is an emerging strategy used in the pharmaceutical industry for solubilizing and improving the biodistribution and circulation lifetime of drugs. Poly(ethylene glycol) (PEG) provides an excellent biocompatible platform for these applications. Specifically, PEG is a common component in cosmetics and an excipient in pharmaceutical formulations. PEG is also finding increasing use in specialty biomedical applications, such as drug and peptide delivery.

PEG is nondegradable and therefore is not ideally suited for in vivo application. While degradable PEG analogs have been prepared, they are difficult to synthesize and are made by uncontrolled processes such as step- growth or condensation methods that result in materials with wide molecular weight distributions which is an undesirable feature for in vivo applications. Yamaoka et al. (Journal of Pharmaceutical Sciences, 1994, 83: 601-606) studied the effect of molecular weight on the circulation half- life of PEG in vivo. They found that the half-life is non-linear as a function of molecular weight. In particular, there is a dramatic increase in circulation half-life occurring at about 30 kg/mol. Due to slow clearance from the blood at molecular weights 30 kg/mol and greater, and a lack of biodegradability in PEG, bioaccumulation is a concern. For this reason, PEG of a lower molecular weight (i.e., less than 30 kg/mol) is typically employed in therapeutic applications.

Several methods of introducing degradability, and thereby enabling the use of higher molecular weight PEGs in linear PEGs, have been studied. Step-growth polymerization of telechelic PEG-macromonomers is among the most common method. Esters, amides, and urethanes have all been utilized as hydrolytically degradable backbone moieties. A potentially versatile postpolymerization modification of PEG involves introducing hydrolytically degradable hemiacetals along the PEG backbone (Reid et al,

Macromolecules, 2010, 43 :9588-9590). However, PEG degradation occurred during hemiacetal formation at low molar incorporations of about 3, limiting degradability and chain-end fidelity of these PEG derivatives. Other degradation-stimuli have also been investigated. Lee et al.,

"Poly(ethylene oxide sulfide): New Poly(ethylene glycol) Derivatives Degradable in Reductive Conditions ", Biomacromolecules, 2005, 6:24-26 describes utilizing disulfide linkages that cleave under reductive conditions, such as those found within a cell. Degradable PEG-replacements prepared by step-growth synthesis have also been developed. Metzke et al. (Journal of the American Chemical Society, 2003, 125:7760-7761) describes methoxylated carbohydrate-derived polyester and polyamide derivatives. For polymer-based therapeutics, the breadth of the molecular weight distribution that results from a step-growth synthesis is a regulatory concern for in vivo applications.

Therefore, there is a need for improved degradable PEGs with controlled molecular weights, both before and after degradation of the polymer. There is also a need for improved methods for making degradable PEGs.

It is an object of the invention to provide degradable-PEGs with controlled molecular weights, both before and after degradation of the polymer.

It is yet another object of this invention to provide improved methods for making degradable PEG polymers.

It is a further object of this invention to provide improved biodegradable medical devices.

SUMMARY OF THE INVENTION

Reactive and hydrolytically-degradable poly(alkylene oxide) derivatives are described herein. These polymers differ from poly(alkylene oxide) by the controlled incorporation of degradable repeat units together with alkylene oxide units. The degradable polymers contain vinyl ether degradable units (e.g., methylene ethylene oxide) incorporated into a polyalkylene backbone (e.g., ethylene oxide, propylene oxide, butylene oxide, other alkylene oxides, glycidol, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other repeat units derived among the glycidyl ethers). The alkylene oxides and glycidyl ethers may be racemic mixtures, enantiomerically enriched, or enantiomerically pure.

The methods of synthesis described herein incorporate the degradable repeat units into degradable poly(alkylene oxide) polymers during copolymerization with alkylene oxide. This allows degradable polymers to be synthesized that have narrower molecular weight distributions compared to copolymers formed via other synthesis methods. This is an important consideration in pharmaceutical applications. Exemplary methods of synthesis are aluminum catalyzed activated-monomer polymerization and anionic ring-opening polymerization.

Degradable-poly(alkylene oxide) polymers increase the range of applications for poly(alkylene oxide) to include applications where hydrolytic degradability under physiological, or physiological-like conditions is desirable. For example, poly(ethylene glycol), or PEG, is an important component of many pharmaceutical, and cosmetic formulations. The degradable polymers disclosed herein can be used in pharmaceutical and cosmetic formulations and degradable devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a synthesis of degradable poly(alkylene oxide) polymer.

Figure 2 shows a synthesis of degradable vinyl ether groups.

Figure 3 shows a synthesis of degradable poly(alkylene oxide) polymer by aluminum catalyzed activated-monomer polymerization.

Figure 4 shows a synthesis of azido-terminal degradable

poly(alkylene oxide) polymer using aluminum catalyzed activated-monomer polymerization.

Figure 5 shows a synthesis of mono functional degradable poly(alkylene oxide) polymer using anionic ring-opening polymerization and a Hofmann elimination to generate the desired degradable product.

Figure 6 shows a synthesis of heterobifunctional degradable poly(alkylene oxide) polymer using anionic ring-opening polymerization and a Hofmann elimination to generate the desired degradable product.

Figure 7 shows the stereochemical relationships between the repeat units.

Figure 8 shows a vinyl-ether hydrolysis mechanism of methylene ethylene oxide units resulting in non-acidic end-groups.

Figure 9 shows a graph of the circulation half-life of non-degradable PEG as a function of PEG molecular weight in kDa (prior art).

Figures 10A and 10B show l H NMR spectra of polyethylene glycol copolymerized with epichlrohydrin (FIG. 10A), and the resultant degradable- PEG polymer after elimination (FIG. 10B).

Figure 11 shows gel permeation chromatography traces of the degradable-PEG polymer (Figure 10) before (solid line), and after hydrolysis (dashed line) by treatment with a 1% aqueous solution of trifluoroacetic acid.

Figure 12 shows the molecular weight after degradation of degradable-PEG polymers (shown in Table 1) with 1% aqueous solution of trifluoroacetic acid as a function of mole percent incorporation of methylene ethylene oxide units in P(EO-co-MEO).

Figure 13 is a graph of molecular weight measured by SEC with respect to PEG standards (g/mol PEG standards) as a function of time (hours) in pH 7.4, and pH 5.0 buffers at 37 °C.

DETAILED DESCRIPTION OF THE INVENTION

I. Degradable Poly(alkylene oxide) Polymers

Degradable poly(alkylene oxide) polymers are disclosed herein. The degradable polymer contains alkylene oxide non-degradable units and vinyl ether degradable units, wherein the mole percent of the degradable units ranges from about 0.001 to about 25 mole percent. "Degradable" as used herein refers to the conversion of materials into smaller components, intermediates, or end products by chemical processes such as hydrolytic degradation and/or by the action of biological entities, such as bacteria or enzymes. It refers to both heterogeneous (or bulk erosion) and homogenous (or surface erosion) degradation, and any stage of degradation between these two by the action of physical or chemical factors on the degradable group(s). Degradation may be the result of, but is not limited to, a chemical reaction, a thermal reaction, an enzymatic reaction, and/or a reaction induced by radiation. The degradability of the degradable poly(alkylene oxide) polymers used depends, at least in part, on the backbone structure of the polymer. For instance, the presence of degradable units, such as hydrolysable monomers in the degradable polymer backbone, often yields a degradable polymer that will degrade as described herein.

The degradable polymers contain one or more non-degradable monomers of alkylene oxide and one or more degradable copolymerizable monomers. Non-degradable alkylene oxide units include, but are not limited to, ethylene oxide, propylene oxide, butylene oxide; or glycidol derivatives including glycidyl-functional amines, glycidyl ether repeat units such as, methyl glycidyl ether, ethylene glycol vinyl glycidyl ether, allyl glycidyl ether, amine functional glycidyl ethers, azide functional glycidyl ethers, alkyne functional glycidyl ethers, glycidyl ethers containing conventional groups used for PEGylation, and glycidyl ethers containing short oligomeric ethylene glycol chains [-(CH 2 CH 2 0) n -] (n<50) containing conventional functional groups for PEGylation (i.e., functional oligo(ethylene glycol) glycidyl ethers), or other functional groups such as hydroxyl, halogens, or combinations thereof. Preferably, the non-degradable poly(alkylene oxide) units are ethylene oxide, propylene oxide, or allyl glycidyl ether in combination with ethylene oxide.

The degradable monomer is a vinyl ether or vinyl ether derivative. The nondegradable and degradable units can each be independently substituted with substituents selected from hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, activated-ester, alkyne, maleimide, alkoxy, n- hydroxy succinimate, 4-nitrophenolate, 3-nitrophenolate, 2-nitrophenolate, tosyl, a polymer, or combinations thereof, or conventional functional groups used in PEGylation of pharmaceuticals or peptides. Veronese and Pasut, Drug Discovery Today, 2005, 10: 1451-1458 reviews successful PEGylation strategies, the disclosure of which is incorporated herein by reference.

Optionally, the degradable poly(alkylene oxide) polymers have functional end groups, that is, they have proximal reactive groups linked to at least one arm of the polymer backbone. "Proximal" as used herein refers to the terminus of each arm of the polymer backbone. The terminus typically has a reactive moiety covalently linked to a polymer backbone through a hydrolytically stable linkage. The reactive moiety is a group capable of reacting with a moiety in another molecule including, but not limited to, targeting agents, imaging agents, therapeutic agents, biologically active agents such as proteins, peptides. Suitable reactive moieties include, but are not limited to, alkenes, alkynes, azides, active esters, active carbonates, aldehydes, isocyanates, isothiocyanates, epoxides, alcohols, maleimides, vinylsulfones, hydrazides, dithiopyridines, 4-nitrophenolate, alkoxy, amines, amides, N-hydroxy succinamide, N-succinimidyl, and iodoacetamides.

The selection of a free reactive moiety is determined by the moiety in another molecule with which the free reactive moiety is to react. For example, when the moiety in another molecule is a thiol moiety, then a vinyl sulfone moiety is preferred for the free reactive moiety of the activated polymer. On the other hand, an N-succinimidyl moiety is preferred to react with an amino moiety on a biologically active agent.

The degradable polymers may be block copolymers, random copolymers, branch copolymers, brush copolymers, comb copolymers. There may be a gradient, alternating, or statistical ordering of the degradable and non-degradable units into the polymer backbone. Further, the polymer backbone may be linear or branched. Typically, a branched polymer has a central branch core moiety and a plurality of linear polymer chains linked to the central branch core.

The molecular weight of the degradable poly(alkylene oxide) polymers is not limited. In one embodiment, the molecular weight is in the range of from about 5,000 g/mol to about 500,000 g/mol, preferably from about 6,000 g/mol to about 100,000 g/mol.

A. Degradable-Poly(alkylene oxide) Copolymer (Two Repeat Units)

In one embodiment, the degradable-poly(alkylene oxide) polymer contains non-degradable alkylene oxide units (shown in parenthesis with subscript x) and degradable vinyl ether units (shown in parenthesis with subscript y), as shown in Formula I:

Formula I wherein,

Ri, R2, R3, R4, R5, R6, R7, Re, R9, and Rio are each independently selected from hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, maleimide, NHS-ester, tosyl, azide, activated-ester, alkyne, alkenes, 4- nitrophenolate, alkoxy, amines, amides, N-hydroxy succinamide, a polymer, or combinations thereof, or conventional functional groups used in

PEGylation;

and where y is between 0.001 and 99.999 mole percent, and x = 100 -y mole percent. Preferably, y is between about 0.001 and about 25 mole percent, more preferably from about 0.01 to about 1 mole percent.

Preferably, Ri and R2 are each independently selected from azide, activated-ester, an alkyne, a polymer, methyl, ethyl. Ri is optionally covalently linked to the polymer backbone through an oxygen atom.

"Activated-esters", as used herein, refers to those known in the art.

Activating groups include, but are not limited to mesylate, tosylate, nosylate, triflate, n-hydroxy succinimate, 4-nitrophenolate, and halide moieties.

The degradable polymers described by Formula I may be block copolymers, random copolymers, branch copolymers, brush copolymers, comb copolymers. There may be a gradient, alternating, or statistical ordering of the degradable and non-degradable units into the polymer backbone. Further, the polymer backbone may be linear or branched.

Typically, a branched polymer has a central branch core moiety and a plurality of linear polymer chains linked to the central branch core.

B. Degradable Poly(alkylene oxide) Copolymers (Three Repeat Units)

Optionally, the degradable poly(alkylene oxide) polymer of Formula I may be combined with additional co-monomers. The degradable polymer may include co-monomers from other non-degradable poly(alkylene oxide) units, monomers from other degradable polymers, or monomers from other non-degradable polymers. Suitable monomers from non-degradable polymers include, but are not limited to, alkylene oxides including glycidyl ether derivatives. Suitable degradable monomers from degradable polymers include, but are not limited to, vinyl ethers, carboxylic acids, lactones, esters, carbonate, amide, acetal, and ketal. In this embodiment, the degradable polymer contains repeat units of alkylene oxide (shown in parenthesis with subscript x), vinyl ether (shown in parenthesis with subscript y), and a degradable monomer or non-degradable monomer denoted by the symbol "D" (repeat unit with subscript m), as shown in Formula II:

Formula II

wherein,

D is independently selected from the group consisting of propylene oxide, ethylene oxide, butylene oxide, or other alkylene oxides, or from a glycidol derivative, for example, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, or other glycidyl ethers, or a-di- or mono-substituted glycidyl ethers, wherein D is optionally independently substituted with one or more substituents independently selected from the group consisting hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, activated- ester, alkyne, a polymer, or combinations thereof;

Ri, R2, R3, R4, R5, R6, R7, Re, R9, and Rio are each independently selected from hydrogen, halogen, cyano, maleimide, NHS-ester, azide, tosyl, alkyl, aryl, ester, ether, azide, activated-ester, alkyne, alkenes, 4- nitrophenolate, alkoxy, amines, amides, N-hydroxy succinamide, a polymer, or combinations thereof, or conventional functional groups used in

PEGylation; and where m is between 0.001 and 99.998 mole percent; y is between 0.001 and 99.998 mole percent, and x = 100 -(y+m). Preferably, y is between about 0.001 and 25 mole percent, more preferably 0.01 to about 1 mole percent.

In one embodiment, R 3 , R4, R 5 , R 6 , R7, Rs, R9, and Rio are hydrogen and Ri and R2 are each independently selected from hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, 4-nitrophenolate, alkoxy, amines, amides, N-hydroxy succinamide, activated-ester, alkenes, alkyne, a polymer, or combinations thereof, or conventional functional groups used in

PEGylation either alone or in combination.

The degradable polymers described by Formula II may be block copolymers, random copolymers, branch copolymers, brush copolymers, comb copolymers.

One exemplary embodiment of a degradable polymer of Formula II is shown as the structure below:

C. Degradable Poly(alkylene oxide) Copolymers containing Glycidol Derivative

Optionally, the non-degradable units in the degradable polymer may further contain a glycidyl ether moiety. In this embodiment, the degradable poly(alkylene oxide) polymer contains repeat units of alkylene oxide (shown in parenthesis with subscript x), vinyl ether (shown in parenthesis with subscript y), and glycidyl ether (shown in parenthesis with subscript p) as shown in Formula III:

Formula III wherein,

Ri, R 2 , R 3 , R 4 , R 5 , Re, R7, Rs, R9, Rio, R11, R12, R13, and R 14 are each independently selected from a group consisting of hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, maleimide, tosyl, NHS-ester, activated- ester, alkyne, alkene, 4-nitrophenolate, alkoxy, amines, amides, N-hydroxy succinamide, a polymer, or combinations thereof, or conventional functional groups used in PEGylation of pharmaceuticals or peptides;

and where x is between 0.001 and 99.998 ; p is between 0.001 and 99.998 mole percent, and z = 100 -(x+p) mole percent. Preferably, y is between about 0.001 and 25 mole percent, more preferably 0.01 to about 1 mole percent.

Preferably, Ri, R2, and R3 are each independently selected from the group consisting of azide, activated-ester, an alkyne, a polymer, methyl, ethyl. Ri is optionally covalently linked to the polymer backbone through an oxygen atom.

The degradable polymers described by Formula III may be block copolymers, random copolymers, branch copolymers, brush copolymers, comb copolymers.

II. Methods of Making Degradable-poly(alkylene oxide)

Copolymerization is a strategy for the synthesis of materials that allow properties to be tuned between those observed for two or more unique homopolymers. Among many polymerizable chemical functionalities, epoxide groups provide a versatile polymerizable functionality for designing materials via copolymerization. A general method for synthesis of the degradable poly(alkylene oxide) polymers with degradable vinyl ether units is shown in Figure 1. This method converts non-degradable monomer units to degradable vinyl ether units, from a copolyether precursor. Degradable poly(alkylene oxide) polymers are formed during this process, however the degradable vinyl ether units can isomerize into non-degradable vinyl ether units (final step in the scheme shown in Figure 1).

Another exemplary method of synthesis of degradable vinyl ether groups, is shown in Figure 2. Similarly to the scheme in Figure 1, non- degradable monomer units are converted to degradable vinyl ether units in the copolyether polymer. It is desirable, in polymer chemistry, to incorporate the degradable repeat units into the polymers during copolymerization with alkylene oxide. This allows degradable polymers to be synthesized that have narrower molecular weight distributions.

The methods of synthesis, discussed below, incorporate the degradable repeat units into the degradable poly(alkylene oxide) polymers during copolymerization with alkylene oxide. Exemplary methods of synthesis are aluminum catalyzed activated-monomer polymerization (Figures 3 and 4) and anionic ring-opening polymerization (Figures 5 and 6).

The stereochemical relationships between the repeat units may be racemic mixtures, enantiomerically enriched, or pure, with segments of the copolymer being racemic, enantiomerically enriched, or pure, or some combination thereof (Figure 7).

1. Lewis-acid catalyzed polymerization

Degradable poly(alkylene oxide) polymers of Formulas I, II, and III can be prepared according to the scheme in Figure 3 (see, for example,

Lundberg et al, ACS Macro Lett. 2012, 1 : 1240-1243). The polymers are prepared from a copolyether precursor polymer, which is prepared by the lewis acid-activated copolymerization of an alkylene oxide and glycidol derivative, such as epichlorohydrin using tetraoctylammonium bromide as initiator. Suitable lewis acid complexes include aluminium complexes such as trialkylaluminum, cobalt complexes, zinc complexes, and iron complexes such as [^ 5 -[C 5 H 5 )Fe(CO) 2 (THF)] + . The alkylene oxide and

epichlorohydrin groups are optionally substituted with a suitable functional group. Suitable functional groups include, but are not limited to, hydrogen, halogen, cyano, azide, alkyl, aryl, ester, NHS-ester, ether, maleimide, tosyl, alkene, azide, activated-ester, alkyne, a polymer, or combinations thereof.

Copolymerizations may be carried out in methylene chloride and initiated at -30 °C under an argon atmosphere.

Degradable poly(alkylene oxide) polymers with functionalize end- groups can also be synthesized using aluminium catalyzed polymerization, Figure 4. The desired functional end group is incorporated in the tetraoctylammonium initiator complex. Suitable functional end groups that may be incorporated in the trioctylammonium initiator include, but are not limited to, azide, halogen, alkoxide, carboxylic acids, alkenes, alkynes, azides, active esters, active carbonates, aldehydes, isocyanates,

isothiocyanates, epoxides, alcohols, maleimides, vinylsulfones, hydrazides, dithiopyridines, N-succinimidyl, and iodoacetamides.

2. Anionic ring opening

Alternately, anionic ring-opening polymerization may be used to synthesize the degradable poly(alkylene oxide) polymers of Formulas I, II, and III. An example is shown in Figure 5. Nonfunctional, monofunctional, or heterobifunctional degradable polymers can be synthesized. This method of synthesis allows control over the molecular weight and molecular weight distribution of the degradable polymer.

Synthesis of degradable polymers using anionic ring opening reacts an alkoxide derivative with alkylene oxide and a glycidol derivative to give a copoly ether compound as shown in Figure 5. Suitable glycidol derivatives include, but are not limited to, glycidyl-functional amines, glycidyl ether repeat units such as, methyl glycidyl ether, ethylene glycol vinyl glycidyl ether, allyl glycidyl ether, amine functional glycidyl ethers, azide functional glycidyl ethers, alkyne functional glycidyl ethers, glycidyl ethers containing conventional groups used for PEGylation, and glycidyl ethers containing short oligomeric ethylene glycol chains [-(CH 2 CH 2 0) n -] (n<50) containing conventional functional groups for PEGylation (i.e., functional

oligo(ethylene glycol) glycidyl ethers), or other functional groups including, but not limited to hydroxyl groups, or halogens, or combinations thereof.

The copolyether then undergoes elimination to form degradable vinyl units within the degradable polymer. The elimination procedure that results in formation of the vinyl double bond may be varied, for example, using a different solvent, bases, and reaction conditions.

Optionally, the starting materials, that is, alkoxide, alkylene oxide, and the functionalized glycidol derivative may be independently substituted. Suitable substituents include, but are not limited to, hydrogen, halogen, cyano, azide, alkyl, aryl, ester, ether, azide, activated-ester, alkyne, a polymer, or combinations thereof.

a) Synthesis of Heterobifunctional Degradable Polymer using Anionic Ring Opening

One exemplary method of synthesizing heterobifunctional degradable polymers using anionic ring opening is shown in Figure 6. The use of glycidyl-functional amines allows incorporation of quaternized amines into the polymer backbone. The quaternized amine is eliminated via Hofmann elimination to yield methylene ethylene oxide units along the backbone.

This synthetic scheme adds the ability to trigger the elimination with heat. Therefore, the poly(alkylene oxide) polymers cen be stored in the quaternized amine form before use. In one embodiment, heat is used to carry out the elimination, generating the methylene ethylene oxide units in situ.

3. Functionalization of degradable vinyl ether units.

The vinyl-ether repeat units that provide the hydrolytic degradability are amenable to alternative PEGylation and functionalization strategies along the poly(alkylene oxide) backbone, while still retaining hydrolytic degradability. The degradable vinyl ether units may be functionalized using reactions known to persons of skill in the art, including, but not limited to, thiol-ene radical reactions, Michael additions of thiols or amines, cycloadditions, and any reaction that vinyl ethers serve as a reactant. 4. Methods of Controlling the Molecular Weight of the Degradable Polymers and their Degradation Products

Precise definition of the postdegradation molecular weight is important in order to avoid toxicity associated with poly(alkylene oxide), such as PEG. Molecular weights lower than about 400 g/mol is generally toxic to mammals. The synthetic methods described above allow control over the starting and final molecular weight. Therefore, a greater degree of control over circulation half-life of PEGylated therapeutics can be achieved.

Using the synthetic strategies above, the molecular weight can be defined by the polymerization stoichiometry, and the number of degradable sites can be adjusted by the comonomer feed-ratio, which defines the average molecular weight after degradation (see Example Table 1 and Lundberg et al, ACS Macro Lett. 2012, 1 : 1240-1243).

III. Methods of Use

Degradable-poly(alkylene oxide) polymers increase the scope of applications for poly(alkylene oxide) to those where hydrolytic degradability under physiological, or physiological-like conditions would be desirable. For example, poly(ethylene glycol), or PEG, is a vital component of many pharmaceutical, and cosmetic formulations. The degradable polymers disclosed, increases the scope of applications for PEG to those where hydrolytic degradability under physiological, or physiological-like conditions would be desirable.

1. Degradation Mechanism

The expected hydrolysis mechanism for the degradable vinyl ether units is based on a generally accepted mechanism of vinyl ether hydrolysis, shown in Figure 8. The degradation products are shorter non-degradable and degradable poly(alkylene oxide) oligomers. Preferably, the degradation products are shorter non-degradable poly(alkylene oxide) oligomers. The molecular weight of the degradation product(s) can be controlled by the amount of degradable units included in the polymerization. Preferably, for degradable polymers with similar mole percent nondegradable units, as the number of degradable vinyl units incorporated into the degradable polymer increases, the average molecular weight of the degraded products decreases. In one embodiment, the molecular weight of the degraded products ranges from about 40,000 g/mol to about 500 g/mol.

The rates at which the degradable poly(alkylene oxide) polymers degrade are dependent on the environment to which the degradable units and/or degradable poly(alkylene oxide) is subjected, e.g., temperature, the presence of moisture, oxygen, microorganisms, enzymes, pH, and the like may affect the rate of degradation. Additionally, the monomer structure, i.e. the functional groups on the monomer units, may be changed in order to change the degradation rate (Leibovitch et al. Progress in Polymer Science, 1991, 230:349-385).

Preferably, the degradable poly(alkylene oxide) polymers degrades hydrolytically. The end groups of the degradable polymer may be non-acidic after degradation; and/ or the repeat units can undergo functionalization reactions.

The degradable poly(alkylene oxide) polymers hydrolytically degrades at pH ranging from about 1 to about 8. The degradable poly(alkylene oxide) polymers degrades markedly faster at a lower pH. For example, degradable-PEG degrades faster at the pH of 5.0 than at pH 7.4, and degrades into non-acidic, shorter PEG oligomers. The degradable polymers can be used in a number of applications in vivo because of their ability to degrade hydrolytically at physiological pH.

a. Ionic or Covalent Coupling to Therapeutic, Prophylactic, or Diagnostic Agents

The degradable polymers are preferably functional. As used herein,

"functionality" is broadly defined as a measure of the type and quantity of functional groups that a particular degradable polymer has while still retaining hydrolytic degradability into shorter polyalkylene oxide chains, or oligomers as desired by the degradable-poly(alkylene oxide) composition. As used herein, "functional groups," are reactive chemical groups which modify the degradable polymers directly or provide sites for further reactions. The degradable-poly(alkylene oxide) polymers may be monofunctional. Mono-functional as used herein refers to a degradable polymer having one functional group at one end which can take part in reactions with other external groups, such as PEGylation reactions, while the other end(s) do not have a functional group. In one embodiment, the degradable-PEG polymer may be heterobifunctional. Heterobifunctional as used herein refers to linear or branched polymers having one functional group at one terminal and a different functional group at least one other terminal.

The degradable poly(alkylene oxide) polymers can encapsulate, be mixed with, or be ionically or covalently coupled to any of a variety of therapeutic, prophylactic or diagnostic agents. Examples of suitable therapeutic agents include synthetic inorganic and organic compounds, proteins and peptides, polysaccharides and other sugars, lipids, and DNA and RNA nucleic acid sequences having therapeutic, prophylactic or diagnostic activities. Nucleic acid sequences include genes, antisense molecules which bind to complementary DNA to inhibit transcription, and ribozymes.

Compounds with a wide range of molecular weight can be encapsulated, for example, between 100 and 500,000 grams or more per mole. Examples of suitable materials include proteins such as antibodies, receptor ligands, and enzymes, peptides such as adhesion peptides, saccharides and

polysaccharides, synthetic organic or inorganic drugs, and nucleic acids. Examples of materials which can be encapsulated include enzymes, blood clotting factors, inhibitors or clot dissolving agents such as streptokinase and tissue plasminogen activator; antigens for immunization; hormones and growth factors; polysaccharides such as heparin; oligonucleotides such as antisense oligonucleotides and ribozymes and retroviral vectors for use in gene therapy. The polymer can also be used to encapsulate cells and tissues,

i. PEGylation Strategies

PEG chains possessing a functional group at only one end are typically not suitable for subsequent derivatization/modification, which is frequently crucial for the design of biomaterials or for biomedical applications. For high-performance PEGylation, heterotelechelic PEG is required, i.e., PEG molecules

having two different reactive functional end groups. Several

heterobifunctional PEG derivatives are commercially available but at relatively high costs.

The methods of making degradable-PEG disclosed, allows the synthesis of heterobifunctional degradable-PEGs to take advantage of already established PEGylation strategies. For example, drugs that exhibit decreased activity when PEGylated, i.e., covalently bound to a PEG, can be attached to degradable-PEG and thereby reap the benefits of PEGylation, such as improved biodistribution and stealth, but allow the drug itself to have a reduced degree of PEGylation interfering with the function of the drug. Degradable-PEG could also be used to fine-tune the circulation half-life of PEGylated therapeutics. Degradable-PEG could be used alone, as a block in a non-degradable PEG, or blended with other non-degradable PEGs to fine- tune the circulation profile. The circulation half-life profile of non- degradable PEG is shown in Figure 9.

ii. Formation of Hydrogels

The degradable poly(alkylene oxide) polymers may be used to form hydrolytically degradable hydrogels. End-functional degradable-PEG could be used as the crosslinking polymer in hydrogel materials, rendering the entire hydrogel hydrolytically degradable. Therefore, the hydrogels can be used as a carrier for delivery of biologically active agents and other suitable biomedical applications. For example, the hydrogel can carry therapeutic drugs and can be implanted or injected in the target area of the body. The hydrogel may also carry other agents such as nutrients or labeling agents for imaging analysis.

Typically, the backbone of the hydrogel is a biocompatible macromolecule. For example, the backbone may have an amino group available to react with the crosslinking degradable polymers to form a hydrolyzable carbamate linkage. Preferably, the backbone has at least two of such amino groups. Examples of such backbones include, but are not limited to, proteins, modified proteins such as glycoproteins, phosphorylated proteins, acylated proteins, and chemically modified proteins, peptides, aminocarbohydrates, glycosaminoglycans, aminolipids, poly(vinylamine), polylysine, poly(ethylene glycol) amines, pharmaceutical agents having at least two amino groups, etc. Specific examples of the backbone include, but are not limited to, fibrin, fibrinogen, thrombin, albumins, globulins, collagen, fibronectin, chitosan and the like. Optionally, the biologically active agents to be delivered can be used as the backbone, or part of the backbone of the hydrogel.

iii. Degradable Devices

The degradable polymers are useful for preparing a variety of medical devices, including but not limited to, biodegradable implants, sutures, matrices and scaffolds for drug delivery and/or tissue engineering. The biodegradable polymers preferably exhibit a relatively slow

biodegradation, for example, having a in vivo half-life of between three and six months. Degradability of the degradable polymers is dependent on properties of the polymer, such as the hydrophobicity of the polymer, the substitution of the polymer with groups which can promote or decrease hydrolysis rate (such as the copolymerization with polylactic acid, which can decrease degradation times substantially), as well as the form of the device.

When devices including the degradable poly(alkylene oxide) polymers are delivered and/or implanted in the body, the degradation products are expected to show very little, if any, acute inflammatory reaction or adverse tissue reaction. Release of the degradation products from the implanted materials typically is slow and well tolerated by the body.

Devices prepared from the degradable poly(alkylene oxide) polymers can be used for a wide range of different medical applications. Examples of such applications include particles, matrices and/or scaffolds for delivery for delivery of a therapeutic or diagnostic agent, particularly for controlled release of an active agent, particles, matrices and/or scaffolds for tissue engineering, cell encapsulation, targeted delivery, guided tissue regeneration; biocompatible coatings on medical devices (including micron and submicron-sized particles); biocompatible implants; wound dressings;

orthopedic devices; prosthetics; injectable materials, such as bone cements, adhesives and/or structural fillers; and diagnostics.

Examples

To investigate the degradability of the degradable-PEG polymers, a series of degradable-PEG materials at 10,000 g/mol on average were synthesized. The molecular weight (M n ), polydispersity (PDI), mole % of epichlorohydrin (ECH) in monomer feedstock, and mole % of methylene ethylene oxide (MEO) units after elimination are shown in Table 1.

Table 1. Characterization of poly [(ethylene oxide)-co-(epichlorohydrin)] precursors and poly[(ethylene oxide)-co-(methylene ethylene oxide)] copolymers.

1 10500 1.25 7030 1.57 1 0.7

2 9200 1.33 3600 1.93 2 1.1 5 10000 1.26 2130 1.74 5 4.5

10 9000 1.44 850 1.61 10 9.0

(a) Number average molecular weight (Mn) and polydispersity (PDI)

determined by SEC in chloroform relative to PEG calibration standards (g/mol) of P(EO-ran-MEO) before degradation.

(b) Number-average molecular weight (M n ) and polydispersity (PDI)

determined by SEC in chloroform relative to PEG calibration standards after degradation in 1% TFA for 24 h at room temperature.

(c) Mole percent of epichlorohydrin (ECH) in monomer feedstock.

(d) Mole percent of methylene ethylene oxide repeat units measured by l H NMR spectroscopy.

NMR of Degradable-PEG

The formation of degradable and reactive MEO units along the PEG backbone can be observed clearly by l H NMR spectroscopy (Figure 10). The changes seen in the spectrum as the P(EO-co-ECH) in Figure 5a is eliminated to P(EO-co-MEO) are consistent with the formation of the vinyl ether (MEO). Hydrolysis

To probe the effect of mole % MEO incorporation on the molecular weight after degradation, the P(EO-co-MEO) (i.e., degradable-PEG) was treated with an aqueous solution of 1 trifluoroacetic acid and characterized by gel permeation chromatography (GPC). A representative GPC trace before (dashed-line), and after (solid line) 1% TFA treatment is shown below in Figure 11. The decrease in molecular weight upon hydrolysis is evident.

The number average molecular weight (M n ) after degradation with 1 TFA as a function of the mole % MEO incorporation is shown in Figure 12 for all samples in Table 1. As expected, as the mole % incorporation of MEO repeat units increases, the ultimate molecular weight of remaining PEG oligomers after degradation decreases.

Effect of pH on Hydrolysis

The effects of pH on degradation kinetics was explored in buffer at pH 7.4, and pH 5.0 at 37 °C. The P(EO-co-MEO) (i.e., degradable-PEG) degraded markedly faster at pH 5.0 than at pH 7.4. The degradable-PEG degraded completely within 10-24 hours at pH 5.0, whereas at pH 7.4 degradation was not complete even after 72 hours. The degraded products had a final molecular weight of about 850 g/mol. The number average molecular weight as a function of degradation time is shown in Figure 13.

Hydrolysis Mechanism

The expected hydrolysis mechanism for the MEO units based on a generally accepted mechanism of vinyl ether hydrolysis is shown in Figure 8. The degradation products are shorter, non-degradable, and degradable PEG oligomers. The molecular weight after degradation of the MEO units can be controlled by the amount of degradable monomer (in this case

epichlrohydrin) included in the polymerization.