WO2005041873A2 - Formulation of exendin-4 - Google Patents

Abstract

The invention provides methods and articles for the administration of exendin-4. These methods and articles provide for the controlled and sustained delivery of relatively large quantities of exendin-4 with a low burst effect. The articles made using the method of the invention have increased percentages (w/w) of macromer, increased crosslinking density, and reduced pore size in comparison to articles made using solution methods.

Description

FORMULATION OF EXENDIN-4 Background of the Invention The invention relates to biodegradable articles for the sustained-release delivery of exendin-4 and methods for administering exendin-4 via these articles. The rapid advances in the fields of genetic engineering and biotechnology have led to the development of an increasing number of proteins and peptides that are useful as pharmaceutical agents. The development of methods for administering these new pharmaceutical agents is thus becoming increasingly important. However, these molecules are generally limited to parenteral administration due to their susceptibility to degradation in the gastrointestinal tract. Treatment for chronic illnesses or indications may require multiple injections per day or injections several times per week over extended periods of time. As a result of the need for frequent injections, patient compliance may be less than optimal. Attempts to maintain a steady level of medication in the blood stream using biodegradable polymer vehicles has attracted considerable attention. These vehicles are biodegradable and do not require retrieval after the medication is exhausted. Therefore, they can be fabricated into microspheres, microcapsules, nanospheres, implantable rods, or other physical shapes with the drug encapsulated within. A burst release of the agent is often observed immediately after administration of the biodegradable delivery system, especially for low molecular weight agents. Burst is often a problem where the primary mechanism of drug release from the biodegradable polymer is diffusion. The initial burst results in much higher than normal therapeutic levels of medication in the blood. These high levels of agent can cause side effects such as nausea, vomiting, delirium and, sometimes, death. Exendin-4 is a peptide that was first isolated from the salivary secretions of the Gila-monster Helo derma suspectum (Eng et al., J. Biol. Chem., 267:7402 (1992)). Exendin-4 has some sequence similarity to several members of the glucagon-like peptide family, with the highest homology, 53%, being to GLP- 1(7-36)NH₂ (Goke et al., J. Biol. Chem., 268:19650 (1993)). GLP-1(7-36)NH₂, also known as proglucagon(78-107) and most commonly as "GLP-1," has an insulinotropic effect, stimulating insulin secretion from pancreatic β-cells; GLP-1 also inhibits glucagon secretion from pancreatic α-cells (Orskov et al., Diabetes, 42:658 (1993); D'Alessio et al., J. Clin. Invest, 97:133 (1996)). GLP-1 is reported to inhibit gastric emptying (Williams et al., J. Clin.

Encocrinol. Metab., 81(1): 327 (1996)). Similar biological activities have been reported for exendin-4. The delivery of peptide drugs is often complicated by factors such as molecular size, susceptibility to proteolytic breakdown, rapid plasma clearance, peculiar dose-response curves, immunogenicity, bioincompatibility, and the tendency of peptides and proteins to undergo aggregation, adsorption, and denaturation. There is a need for alternative methods of administering peptide drugs, such as exendin-4, in a sustained release fashion with little or no burst release.

Summary of the Invention The present invention features articles for the delivery of exendin-4, and methods for making such articles. The articles made using the method of the invention have increased percentages (w/w) of macromer, increased crosslinking density, and reduced pore size in comparison to articles made using solution methods. The articles exhibit extended release profiles. The invention also features methods of treating a mammal using the articles described herein. Accordingly, in a first aspect the invention features a therapeutic article for delivery of exendin-4, including exendin-4 within a polymerized macromer, the macromer including at least one water soluble polymer region, at least one degradable polymer region which is hydrolyzable under in vivo conditions, and polymerized end groups, wherein the polymerized end groups are separated by at least one degradable polymer region. When fully hydrated the article includes at least 35% (w/w) polymerized macromer. Desirably, the fully hydrated article includes at least 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or even 95% (w/w) polymerized macromer. In a preferred embodiment of the first aspect of the invention, the article when fully hydrated includes less than 50% (w/w) water. Desirably, the fully hydrated article includes less than 45%, 40%, 35%, 30%, 25%, 20%, 15%, or even 12% (w/w) water. In a second aspect, the invention features a method for making a controlled release therapeutic article for delivery of exendin-4, wherein the article includes exendin-4 within a polymerized macromer, the macromer including at least one water soluble polymer region, at least one degradable polymer region which is hydrolyzable under in vivo conditions, and polymerized end groups, wherein the polymerized end groups are separated by at least one degradable polymer region. The method includes the steps of: a) heating the macromer until it melts; b) forming a mixture of exendin-4 and melted macromer; and c) polymerizing the mixture to form the therapeutic article. In one embodiment of the second aspect of the invention, the mixture of step (b) is emulsified prior to step (c). The emulsion can be formed with a non- miscible continuous phase liquid (e.g., propylene glycol, mineral oil). Alternatively, the mixture of step (b) can be sprayed from a nozzle to produce small droplets, which are then polymerized, for example, upon exposure to UV light. In another embodiment of the second aspect, the mixture of step (b) comprises exendin-4 in the form of a particle having a mean particle size of 0.02 to 10 microns. Desirably, the exendin-4 is in the form of a particle having a mean particle size of 0.02 to 5 microns, 0.05 to 10 microns, 0.05 to 5 microns, 0.1 to 5 microns, or 0.02 to 0.5 microns. In a preferred embodiment of the second aspect of the invention, the article when fully hydrated includes at least 35% (w/w) polymerized macromer. Desirably, the fully hydrated article includes at least 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or even 95% (w/w) polymerized macromer. In another preferred embodiment of the second aspect of the invention, the article when fully hydrated includes less than 50% (w/w) water. Desirably, the fully hydrated article includes less than 45%, 40%, 35%, 30%, 25%, 20%, 15%, or even 12% (w/w) water. In a third aspect, the invention features a method of treating a mammal including administering a therapeutic article of the first aspect of the invention to a mammal. Desirably, the mammal is a dog, cat, cow, pig, horse, sheep, goat, or human. Such mammals include those who have diabetes mellitus, have impaired glucose tolerance, are obese, hyperglycemic, or have dyslipidemia and/or cardiovascular disease. In yet other embodiments of the third aspect, the articles are administered systemically or locally. Desirably, the articles are administered subcutaneously, intramuscularly, intravenously, orally, nasally, or are administered to the lung of the mammal. In another embodiment of any of the above aspects, the polymerized macromer includes: (a) a region forming a central core; (b) at least two degradable regions attached to the core; and (c) at least two polymerized end groups, where the polymerized end groups are attached to the degradable regions. Desirably, the region forming a central core is a water soluble region. The water soluble region may be poly(ethylene glycol), poly(ethylene oxide), poly(vinyl alcohol), poly(vinylpyrrolidone), poly(ethyloxazoline), poly(ethylene oxide)-co-ρoly(propylene oxide) block copolymers, polysaccharides, carbohydrates, proteins, and combinations thereof. For example, the water soluble region may consist essentially of PEG having a molecular weight of about 500 to 30,000 daltons, or more preferably, between 1,000 and 10,000 daltons. Degradable regions include, without limitation, poly(α-hydroxy acids), poly(lactones), poly(amino acids), poly(anhydrides), poly(orthoesters), poly(orthocarbonates), poly(α-hydroxy alkanoates), poly(dioxanones), and poly(phosphoesters). The poly(α-hydroxy acid) can be poly(glycolic acid), poly(DL-lactic acid), or poly(L-lactic acid), and the poly(lactone) is poly(ε- caprolactone), poly(δ-valerolactone), or poly(γ-butyrolactone). Desirably, the degradable region includes poly(caprolactone). The degradable region may include a blend of at least two different polymers. Desirably, the polymerizable end groups contain a carbon-carbon double bond capable of polymerizing the macromer. In another embodiments of any of the above aspects, the macromer includes: (a) a water soluble region including a three-armed poly(ethylene glycol); (b) lactate groups attached to the region in (a); and (c) acrylate groups capping the region in (b). The macromer may alternatively include: (a) a water soluble region including a three-armed poly(ethylene glycol); (b) lactate groups on either side of the region in (a); and (c) acrylate groups capping either side of the region in (b). In another alternative, the macromer may include (a) a water soluble region including a three-armed poly(ethylene glycol); (b) caprolactone groups on either side of region in (a); and (c) acrylate groups capping either side of the region in (b). In one embodiment of any of the above aspects, the macromer includes a water soluble region consisting of a three-armed, four-armed, five-armed, six- armed, seven-armed, or eight-armed PEG with a molecular weight of 1,000 to 20,000, 1,000 to 15,000, 1,000 to 10,000, 1,000 to 7,000, 2,000 to 6,000, 4,200 to 5,400 daltons; degradable polymers at the end of each arm of the PEG; and polymerizable end groups attached to each of the degradable polymers. In another embodiment of any of the above aspects, the macromer includes a water soluble region consisting of a three-armed PEG with a molecular weight of 4,200 to 5,400 daltons; lactate groups one end of each arm of the PEG; and acrylate groups capping the lactate groups. The macromer can also be made of a triad ABA block copolymer of acrylate-poly(lactic acid)- PEG-acrylate-poly(lactic acid)-acrylate. The PEG has a MW of 3,400 daltons; the poly(lactic acids) on both sides have an average of about five lactate units per side; and the macromer is therefore referred to herein as A3.4kL5. A lower molecular weight PEG, such as MW 2,000 daltons PEG can be used in place of the MW 3,400 PEG, and the resulting macromer is abbreviated as "2kL5." The macromer is an acrylate-PCL-PEG-PCL-acrylate macromer. The PEG has a MW of 3,400 daltons and has polycaprolactone (PCL) on both sides, with an average of about 6 caproyl units per side. This macromer is referred to herein as "3.4kC6." In still other embodiments of any of the above aspects of the invention, the article includes at least 0.1% exendin-4 by dry weight. More preferably the article includes at least 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, or even 30% exendin-4 by dry weight. In an embodiment of any of the above aspects, the time at which 5% of the releasable exendin-4 is released from the article is greater than 1/16 of t₅₀. The articles of the invention can release exendin-4 such that t₅₀ is greater than or equal to 5/8 of t₈₀. The therapeutic articles of the invention can be capable of releasing the exendin-4 for at for a period of time at least 2 times greater than t₅₀. The article can also capable of delivering a therapeutic dose of the exendin-4 for at for a period of time at least 11/4 times greater than t₅₀. In yet another embodiment of any of the above aspects, at least 80% of the therapeutic articles may have a particle size of less than about 80 microns. Desirably, at least 80% of the therapeutic articles have a particle size of less than 50, 40, 30, 20, 10, 5, 4, 3, 2, 1, or even 0.5 microns. The density of the particles is expressed in terms of tap density. Tap density is a standard measure of the envelope mass density. The envelope mass density of an isotropic particle is defined as the mass of the particle divided by the minimum sphere envelope volume within which it can be enclosed. The density of particles can be measured using a GeoPyc (Micrometers Instrument Corp., Norcross, GA) or a AutoTap (Quantachrome Corp., Boyton Beach, FL). In one embodiment of the first and second aspects of the invention, the tap density of the articles is greater than 0.6 g/cm³. Desirably, the tap density is greater than 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.1, 1.2, 1.3, 1.4, or even 1.5 g/cm³. In one embodiment of any of the above aspects, the therapeutic article is biocompatible. In another embodiment of any of the above aspects, the degradable polymer region is hydrolyzed in the presence of water. In yet another embodiment of any of the above aspects, the degradable polymer region is hydrolyzed enzymatically. The methods and compositions described herein can also be used to generate information useful, for example, for increasing investment in a company or increasing consumer demand for the methods and/or compositions. The invention therefore features a method of increasing consumer demand for a pharmaceutical composition (e.g., the articles of the invention) or therapeutic regimen (e.g., the administration of articles of the invention) described herein. The method includes the step of disseminating information about the pharmaceutical composition or therapeutic regimen. The invention further features a method of increasing investment in a company seeking governmental approval for the sale of a pharmaceutical composition and/or therapeutic regimen described herein. The method includes the steps of i) disseminating information about the pharmaceutical composition or therapeutic regimen and ii) disseminating information about the intent of the company to market the pharmaceutical composition or therapeutic regimen. Consumer demand for a pharmaceutical composition described herein can be increased by disseminating information about the utility, efficacy, or safety of the pharmaceutical composition. Consumers include health maintenance organizations, hospitals, doctors, and patients. Typically, the information will be disseminated prior to a governmental approval for the sale of a composition or therapeutic regimen of the invention. A company planning to sell a pharmaceutical composition described herein can increase investment therein by disseminating information about the company's intention to seek governmental approval for the sale of and disseminating information about the pharmaceutical composition and/or therapeutic regimen of the invention. For example, the company can increase investment by disseminating information about in vivo studies conducted, or planned, by the company, including, without limitation, information about the toxicity, efficacy, or dosing requirements of a pharmaceutical composition or therapeutic regimen of the invention. The company can also increase investment by disseminating information about the projected date of governmental approval of a pharmaceutical composition or therapeutic regimen of the invention. Information can be disseminated in any of a variety of ways, including, without limitation, by press release, public presentation (e.g., an oral or poster presentation at a trade show or convention), on-line posting at a web site, and mailing. Information about the pharmaceutical composition or therapeutic regimen can include, without limitation, a structure, diagram, figure, chemical name, common name, tradename, formula, reference label, or any other identifier that conveys the identity of the pharmaceutical composition or therapeutic regimen of the invention to a person. By "in vivo studies" is meant any study in which a pharmaceutical composition or therapeutic regimen of the invention is administered to a mammal, including, without limitation, non-clinical studies, e.g., to collect data concerning toxicity and efficacy, and clinical studies. By "projected date of governmental approval" is meant any estimate of the date on which a company will receive approval from a governmental agency to sell, e.g., to patients, doctors, or hospitals, a pharmaceutical composition or therapeutic regimen of the invention. A governmental approval includes, for example, the approval of a drug application by the Food and Drug Administration, among others. As used herein, "exendin-4" refers to the peptide of SEQ ID NO. 1 : His Gly Glu Gly Thr Phe Thr Ser Asp Leu Ser Lys Gin Met Glu Glu Glu Ala Val Arg Leu Phe He Glu Trp Leu Lys Asn Gly Gly Pro Ser Ser Gly Ala Pro Pro Pro Ser-NH₂. By "macromer" is meant a polymer with three components: (1) a biocompatible, water soluble region; (2) a degradable region, and (3) at least two polymerizable regions. As used herein, "biocompatible" refers to a therapeutic article which is administered to a subject, cell, or tissue to treat, replace, or augment a function of the subject, cell or tissue, and is not harmful to the function. Biocompatible articles produce minimal immune cell infiltration and encapsulation when injected in vivo. As a result, the bioavailability of the exendin-4 is not reduced by immunological responses. As used herein, "hydrolyzable under in vivo conditions" refers to the degradable region of a macromer or therapeutic article. One or more bonds within the degradable region are cleaved by the addition of water. The degradable region can be selected to hydrolytically degrade in aqueous environments. Examples of degradable regions that hydrolyze in the presence of water include esters and carbonates, among others. Alternatively, the degradable region can be selected to selectively hydrolyze in the presence of an enzyme. Examples of degradable regions that can be enzymatically hydrolyzed in vivo include polypeptides, among others. By "therapeutic dose," is meant a plasma level between the minimum effective level and the toxic level of exendin-4. As used herein, "pore size" refers to the dimensions of a space in the intact article through which exendin-4 potentially can pass. Pore sizes which are created using the melt process of the invention are smaller than the previously reported solution-phase polymerization described in the prior art. As a result, even low molecular weight substances formulated as described herein are released over longer periods of time. As used herein, "period of release" is meant the length of time it takes for a specified percent of the exendin-4 to be released from an article. The period of release may be assessed, for example, by measuring the time it takes for 10%, 20%, 30%, 40%, 50%, or 80% of the exendin-4 to be released from the article. By "low burst effect" is meant that the amount of exendin-4 released from an article is released relatively steadily over time, rather than at an initial fast rate, followed by a slower rate. For example, a therapeutic article has a low burst effect (e.g., less than or equal to 20% burst) upon release from an article when the period of release for 5% of the releasable exendin-4 is greater than 1/16 of t₅₀, or when the t₅₀ is greater than or equal to 5/8 of t₈₀. In contrast to a low burst article, a high burst article (e.g., one which rapidly releases 30% of the exendin-4) might release 5% of its releasable exendin-4 in less than 1/18 of t₅₀ and have a t₅₀ equal to 1/2 of t₈₀. A specific example of a low burst product of the present invention is one in which less than 20% of the exendin-4 comes out in the first day for a product designed to release exendin-4 for 10 days. By "t₅₀" is meant the time at which 50% of the releasable exendin-4 has been released. Preferably, the articles of the invention release 5% of the releasable exendin-4 at a time which is greater than 1/16 of t₅₀, or the t₅₀ is greater than or equal to 5/8 of the t₈₀. By "t₈₀" is meant the time at which 80% of the original load of exendin- 4 has been released. As used herein, the term "dry" refers to articles containing less than 10% water by weight. Desirably, the water content of the dry article is less than 5%, 2%, 1%, 0.5%, or less. Articles can be dried using a variety of techniques, such as lyophilization or by exposure to a stream of dry gas. As used herein, the term "fully hydrated" refers to articles placed in a stirring solution of phosphate buffered saline at 37 C (pH = 7.4) for one hour and isolated by centrifugation.

Brief Description of the Drawings Fig. 1 is a graph depicting the in vitro release of GLP-1 from a therapeutic article prepared as described in Example 1. Detailed Description The invention provides methods and articles for the administration of exendin-4. These methods and articles provide for the controlled, sustained delivery of relatively large quantities of exendin-4, with a low burst effect. The articles made using the method of^" the invention have increased percentages (w/w) of macromer, increased crosslinking density, reduced pore size, and decreased swelling in water in comparison to articles made using solution methods. As a result, the articles exhibit extended release profiles for exendin- 4.

Macromers The macromers of the present invention have at least one water-soluble region, at least one degradable (e.g., hydrolyzable) region, and at least one polymerizable region. The macromers may be water-soluble or water insoluble. These macromers are polymerized to form hydrogels, which are useful for delivering incorporated exendin-4 at a controlled rate. Methods of formulating macromers and shaping them into articles are described, for example in WO99/03454, incorporated herein by reference. An important aspect of the macromers is that the polymerizable regions are separated by at least one degradable region. This separation facilitates uniform degradation in vivo. The ratio between the water-soluble region and the hydrolyzable region of the macromer determines many of the general properties of the macromer. For example, the water solubility of the macromers can be controlled by varying the percentage of the macromer that consists of hydrophobic degradable groups. Accordingly, the macromer can be altered by changing the identity of the degradable groups or the number of degradable groups. There are several variations of the macromers of the present invention. For example, the polymerizable regions can be attached directly to the degradable regions; alternatively, they can be attached indirectly via water- soluble, non-degradable regions, with the polymerizable regions separated by a degradable region. For example, if the macromer contains a single water- soluble region coupled to a degradable region, one polymerizable region can be attached to the water-soluble region, and the other to the degradable region. Typically, the water-soluble region forms the central core of the macromer and has at least two degradable regions attached to it. At least two polymerizable regions are attached to the degradable regions so that, upon degradation, the polymerizable regions, particularly in the polymerized gel form, are separated. Alternatively, if the central core of the macromer is formed by a degradable region, at least two water soluble regions can be attached to the core, and polymerizable regions are attached to each water soluble region. In some instances, the macromer has a water-soluble backbone region, with a degradable region attached to the macromer backbone. At least two polymerizable regions are attached to the degradable regions, such that they are separated upon degradation, resulting in gel product dissolution. The macromer backbone region can be formed of a degradable backbone region having water-soluble regions as branches or grafts attached to the degradable backbone, wherein two or more polymerizable regions are attached to the water soluble branches or grafts. In another variation, the macromer backbone may have multiple arms; e.g., it may be star-shaped or comb-shaped. The backbone may include a water-soluble region, a biodegradable region, or a water-soluble, biodegradable region. The polymerizable regions are attached to this backbone. Again, the polymerizable regions must be separated at some point by a degradable region. Throughout the specification, the following nomenclature is used to describe the specific macromers of the invention. In three particular examples, a macromer having a water soluble region consisting of PEG with a molecular weight of 4,000 daltons, with 5 lactate groups on either side of this region, capped on either side with acrylate groups, is referred to as "4kL5." Similarly, a macromer having a water soluble region consisting of PEG with a molecular weight of 3,400 daltons, with 6 caprolactone groups on either side of this region, capped on either side with acrylate groups, is referred to as "3.4kC6." Likewise, a macromer having a water soluble region consisting of PEG having a molecular weight of 4,400 daltons and 3 arms, each arm containing 3 lactate groups, extending from this region, capped on either side with acrylate groups, is referred to as "4.4kL3-A3." "4.4kC5-A3" is a macromer having a water soluble region consisting of PEG having a molecular weight of 4,400 daltons and 3 arms, each arm containing 5 caprolactone groups, extending from this region, capped on either side with acrylate groups. Other macromers may be identified using this same no enclature. As mentioned above, one of the ways in which the release properties of the polymerized macromer can be altered is by making changes to the degradable region. The degradable region can contain, for example, polymers of glycolic acid, lactic acid, caprolactone, trimethylene carbonate, or blends or copolymers thereof. As the degradable region increases in hydrophobicity, the polymerized macromer will degrade in water more slowly. A macromer having a degradable region containing 15-20 lactide units can be prepared; this macromer will provide a relatively fast release rate. A macromer with a degradable region containing 6 caprolactone units will provide a relatively slow release rate. A macromer with a degradable region containing a copolymer of 6 caprolactone units, 4 lactide units, and 4 glycolide units will provide a fast release rate, and a macromer with a degradable region containing a copolymer of 3 lactide units and 7 trimethylene carbonate units will provide an intermediate release rate. The water soluble region of these macromers is preferably PEG. The water soluble region can have multiple arms; for example, it may be star- shaped or comb-shaped, as described, for example in U.S. Patent No. 5,410,016, incorporated herein by reference. The water soluble region preferably has 3, 4, 6, or 8 arms and a molecular weight of 500 to 20,000, preferably, 1,000 to 10,000 daltons. Water-Soluble Region The water soluble region of the macromer may include poly(ethylene glycol), poly(ethylene oxide), poly( vinyl alcohol), poly(vinylpyrrolidone), poly(ethyloxazoline), poly(ethylene oxide)-co-poly(propylene oxide) block copolymers, polysaccharides, carbohydrates, or proteins, or combinations thereof. The macromer preferably includes a water soluble core region including PEG, as PEG has high hydrophilicity and water solubility, as well as good biocompatibility. The PEG region preferably has a molecular weight of about 400 to about 40,000 daltons, and more preferably has a molecular weight of about 400 to 20,000, 400 to about 15,000 daltons, about 1,000 to about 12,000 daltons, or about 1,000 to about 10,000 daltons.

Degradable Region The degradable region of the macromer may contain, for example, poly(α-hydroxy acids), poly(lactones), poly(amino acids), poly(anhydrides), poly(orthoesters), poly(orthocarbonates) or poly(phosphoesters), or blends or copolymers of these polymers. Exemplary poly(α-hydroxy acids) include poly(glycolic acid), poly(DL- lactic acid), and poly(L-lactic acid). Exemplary poly(lactones) include poly(ε- caprolactone), poly(δ-valerolactone), poly(γ-butyrolactone), poly(l,5- dioxepan-2-one), and poly(trimethylene carbonate). The degradable region may include a blend of at least two different polymers. Examples of copolymers include a copolymer of caprolactone and glycolic acid; and a copolymer of caprolactone and lactic acid. Polymerizable Region The polymerizable regions of trie macromer preferably contain carbon- carbon double bonds capable of polymerizing the macromers. The choice of an appropriate polymerizable group permits rapid polymerization and gelation. Polymerizable regions containing acrylates are preferred because they can be polymerized using several initiating systems, as discussed below. Examples of acrylates include acrylate, methacrylate, and methyl methacrylate.

Exendin-4 Exendin-4 can be synthesized using, for example, solid phase methods

(see Merrifield, Chem. Soc. 85:2149 (1962); and Stewart and Young, "Solid Phase Peptide Synthesis," Freeman, San Francisco, 1969, pp. 27-66). It is also possible to isolate naturally occurring exendin-4 from venom samples as described in Eng et al., J. Biol. Chem., 267:7402 (1992). Alternatively, it is possible to obtain exendin-4 using recombinant DNA techniques (see, for example, Maniatis et al, "Molecular Biology: A Laboratory Manual," Cold Spring Harbor, N.Y., 1982). Exendin-4 can be purchased from Phoenix Pharmaceuticals Inc. (Catalogue No. 070-94).

Preparation of Articles The articles of the present invention may be formed in any shape desired. For example, the articles may be shaped to fit into a specific body cavity. They may also be formed into thin, flat disks, pellets, rods, or particles, such as microspheres. Alternatively, the articles may be shaped, then processed into the desired shape before use, or ground into fine particles. The desired shape of the article will depend on the specific application. As used herein, the term "particles" includes, but is not limited to, microspheres. In a microsphere, exendin-4 is dispersed throughout the particle. The particles may have a smooth or irregular surface, and may be solid or slightly porous, but with a pore size smaller than the hydrodynamic radius of human growth hormone. ,

Preconditioning of Exendin-4 The particle size and distribution of the exendin-4 particles can affect the release profile of the therapeutic articles. The particle size and distribution of the exendin-4 can be adjusted using techniques known in the art, including the inclusion of additives, choice of equipment and methodology in the preparation of the articles, and processing conditions. Desirably, the exendin-4 is preconditioned to form of a microparticulate powder having a particle size of about 0.02 to 10 microns, 0.05 to 5 microns, or 0.1 to 4 microns, depending upon the route of administration for which they are being formulated. Exendin-4 can be preconditioned to a microparticulate powder using a variety of processes, including spray drying, flash freezing, crystallization, cryopelletization, precipitation, super-critical fluid evaporation, coacervation, homogenization, inclusion complexation, lyophilization, melting, mixing, molding, solvent dehydration, sonication, spheronization, spray chilling, spray congealing, spray drying, and combinations thereof. In some instances, appropriate additives can also be introduced to the exendin-4 during preconditioning to facilitate the formation of a microparticiuate powder. For example, such powders can be prepared by coating the surface of the particulate exendin-4 particles with sugars, such as lactose, sucrose, trehalose, or dextrose; polysaccharides, such as maltodextrin or dextrates; starches; cellulose, such as microcrystalline cellulose or microcrystalline cellulose/sodium carboxymethyl cellulose; inorganics, such as dicalcium phosphate, hydroxyapitite, tricalcium phosphate, talc, or titania; polyols, such as mannitol, xylitol, sorbitol; or surfactants, such as PEG; or combinations thereof. Alternatively, a microparticulate powder can be prepared from a suitable salt of exendin-4. Acceptable salts include non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids; polymeric acids such as tannic acid, or carboxymethyl cellulose; and inorganic acid addition salts such as hydrochloric acid, hydrobromic acid, sulfuric acid, or phosphoric acid. Cationic salts can be prepared from zinc, iron, sodium, potassium, magnesium, meglumine, ammonium, and calcium, among others. Typically, the final step of preconditioning involves preparing a finely divided powder by milling, micronizing, nanosizing, (e.g., under high pressure) or precipitating the exendin-4 prior to its use in the macromer formulations described herein.

Polymerization of Macromers to Therapeutic Articles The macromers of the present invention are polymerized using polymerization initiators under the influence of long wavelength ultraviolet light, visible light, thermal energy, or a redox system. In combination with the melt process of the invention, the use of long wavelength ultraviolet light is prefened. Polymerization of the macromers may be initiated in situ by light having a wavelength of 320 nm or longer. When the polymerizable region contains acrylate groups, the initiator may be any of a number of suitable dyes, such as xanthine dyes, acridine dyes, thiazine dyes, phenazine dyes, camphorquinone dyes, acetophenone dyes, or eosin dyes with triethanolamine, 2,2-dimethyl-2- phenyl acetophenone, and 2-methoxy-2-phenyl acetophenone. The polymerization may also take place in the absence of light. For example, the polymerization can be initiated with a redox system, using techniques known to those of skill in the art. In some cases it is advantageous to prepare articles using the methods described herein using a redox system, as radical initiator production occurs at reasonable rates over a wide range of temperatures. Initiators that can be used in the redox system include, without limitation, peroxides such as acetyl, benzoyl, cumyl and t-butyl; hydroperoxides such as t-butyl and cumyl, peresters such as t-butyl perbenzoate; acyl alkylsulfonyl peroxides, dialkyl peroxydicarbonates, diperoxyketals, ketone peroxide, azo compounds such as 2,2'- azo(bis)isobutyronitrile (AIBN), disulfϊdes, and tetrazenes.

Excipients Excipients may be added to the melt prior to polymerization to, for example, modulate the hydrophobicity of the resulting article. Excipients that can be used in combination with the present invention include saccharides, such as of sucrose, trehalose, lactose, fructose, galactose, mannitol, dextran and glucose; poly alcohols, such as glycerol or sorbitol; proteins, such as albumin; hydrophobic molecules, such as oils; hydrophobic polymers, such as polylactic acid or polycaprolactone; and hydrophilic polymers, such as polyethylene glycol, among others. Excipients may also be incorporated during the preconditioning of the exendin-4. For example, a lipophilic salt of exendin-4 can be prepared (e.g., acrylamido-2-methyl-l-propanesulfonic acid), thereby altering the water solubility of the encapsulated exendin-4 and its release profile. The Melt Process To prepare the articles described herin, the macromer is heated until it forms a melt. To the liquid macromer is added a) exendin-4 powder with or without preconditioning; b) a polymerization initiator dissolved in a minimal amount of solvent; and, optionally, c) additional excipients as desired to alter the release profile of the resulting therapeutic article. The resulting viscous liquid is a mixture containing suspended particles of exendin-4 and ready for polymerization. Prior to polymerization the melt can be formed into any desired shape as described above. For example, to form particles the viscous melt can be added to an immiscible liquid with vigorous mixing to form an emulsion and, for example, exposed to light to polymerize the macromers to form hydrogel particles incorporating the substance, such as exendin-4. Typically, emulsion and polymerization is carried out under conditions in which the temperature is controlled to keep the macromer in a liquid state. Non-miscible solvents that can be used to form an emulsion with the macromer-melt include, without limitation, silicon oil, mineral oil, polypropylene glycol, Migliyoyl 850, oils that are removed after production of the microspheres, and any oils generally regarded as safe (GRAS) by the Food and Drug Administration. The microspheres prepared using the techniques described above are first washed to remove any oils used in emulsion methods, any organic solvents used in washing steps (e.g., to remove oils), and dried by lyophilization or by passing anhydrous gas (e.g., dry nitrogen) over or through a fluidized bed of the microspheres, so they have a long shelf life (without biodegradation). Prior to use for injectable formulations, the microspheres are reconstituted in a suitable solution, such as saline or other liquids. For pulmonary delivery, either freeze dried or reconstituted particles may be used. Properties of the Therapeutic Articles The articles of the present invention are biodegradable. Biodegradation occurs at the linkages within the extension oligomers and results in fragments which are non-toxic and easily removed from the body and/or are normal, safe chemical intermediates in the body. The articles have a high density of crosslinking in comparison articles produced by polymerization in solution having lower macromer content. As a result, the articles are particularly useful for the sustained delivery of low molecular weight peptides, such as exendin-4, since the tight crosslinking limit diffusion into and out of the articles prior to degradation. The relatively higher macromer content results in a much denser article, which swells in the body more slowly and, hence, degrades more slowly.

Use of the Therapeutic Articles Macromers can be shaped into articles, for example, microspheres, and these articles are capable of degrading under in vivo conditions at rates that permit the controlled release of incorporated exendin-4. Release of exendin-4 may occur by its diffusion from the polymer prior to degradation and/or by diffusion of the material from the polymer as it degrades. Degradation of the polymer facilitates eventual controlled release of free macromolecules in vivo by gradual hydrolysis of the terminal degradable region. The burst effects that are sometimes associated with other release systems are thus avoided in a range of formulations. The rate of release of exendin-4 depends on many factors, for example, the composition of the water soluble region, the degree of polymerization of the macromer. The rate of release of exendin-4 also depends on the rate of degradation of the degradable region of the macromer. For example, glycolic esters lead to very rapid degradation, lactic esters to somewhat slower degradation, and caprolactic esters to very slow degradation. When the degradable region consists of polyglycolic acid, the release period is less than one or two weeks. When the degradable region consists of poly(lactic acid), the release period is about one week or greater. When the degradable region consists of a copolymer of caprolactone and lactic acid or a copolymer of trimethylene carbonate and lactic acid, the release period is two weeks or greater. When the degradable region consists of poly(trimethylene carbonate) or a copolymer of caprolactone and trimethylene carbonate, the release period is about three weeks or greater. When the degradable region consists of poly(trimethylene carbonate) or poly(caprolactone), the release period is longer than about five weeks. The precise rate of release of exendin-4 from an article can be further modified by altering the ratio of hydrophilic and hydrophobic components of the article. For example, a very soluble macromer will yield, after polymerization, a hydrophilic gel; hydrophilic hydrogels have been shown to degrade more rapidly than hydrophobic ones. A blend of a hydrophilic macromer (e.g., 4kL5) with a hydrophobic water insoluble macromer (3.4kC6) is used to form a polymerized hydrogel. This hydrogel will have a release rate that is in between the release rate of a hydrogel containing only lactic acid and a hydrogel containing only caprolactone. A macromer in which the degradable region is a copolymer of caprolactone and lactic acid will also have a release rate which is in between the release rate of a hydrogel containing only lactic acid and a hydrogel containing only caprolactone as the primary degradable group.

Therapy Exendin-4 acts as an agonist of the GLP-1 receptor. The use of exendin- 4 as an insulinotropic agent for the treatment of diabetes mellitus and the prevention of hyperglycemia is described in U.S. Patent No. 5,424,286. Exendin-4 is also said to stimulate somatostatin release and inhibit gastrin release in isolated stomachs (Goke et al., J. Biol. Chem., 268:19650 (1993); Schepp et al., Eur. J. Pharmacol, 69:183 (1994); and Eissele et al., Life Set, 55:629 (1994)). Furthermore, the use of exendin-4 is described in U.S.S.N. 08/908,867, filed August 8, 1997, to regulate gastrointestinal motility; in U.S.S.N. 09/756,690, filed January 9, 2001, to modulate triglyceride levels and treat dyslipidemia; and in U.S.S.N. 09/003,869, filed January 7, 1998, to reduce food intake. The amount of exendin-4 to be administered for the treatment of a particular condition is described in the patents and patent applications above and in U.S.S.N. 10/157,224, filed May 28, 20O2, which describes sustained release formulations of exendins. Each of the patents and patent applications described above are incorporated herein by reference. The polymer articles of the present invention may be used to treat a mammal, by delivering exendin-4 to the mammal in a controlled manner with a low burst effect. Various routes of administration may be used to deliver the articles of the present invention, as described below.

Administration Therapeutic articles containing exendin-4 can be administered subcutaneously, intramuscularly, intravenously, orally, nasally, or to the lung of the mammal.

Intramuscular and Subcutaneous Administration The articles of the present invention can be used to administer microspheres that degrade over a day, several days, or even up to 3-6 months, by intramuscular injection or by subcutaneous injection. For this application, particle sizes of up to 1 mm, or greater, can be used. Intravenous Administration In the case of intravenous injection, it is important to formulate the microspheres in acceptable agents so the microspheres do not aggregate and clog blood vessels. The microspheres must be appropriately sized, so that they don't lodge in capillaries. For this application, particle sizes of 0.2-0.5 μm are preferred. The microspheres of the present invention may be cleared relatively slowly from the circulation. Alternatively, the microspheres can be targeted to exit the circulatory system through leaky blood vessels or through more active targeting mechanisms, e.g., receptor mediated targeting mechanisms.

Oral Administration In some portions of the gastrointestinal tract, there is relatively good transport of peptides across the intestinal mucosa into the systemic and local circulation. The articles of the invention, for example, freeze dried microspheres having very small particle sizes and containing exendin-4, can therefore be administered orally in an appropriate enteric formulation that protects the exendin-4-containing microspheres from enzymatic attack and the low pH found in the upper GI tract. Such an enteric formulation could also be designed using several available technologies to gradually expel exendin-4- containing microspheres as the enteric capsule traverses the gastrointestinal tract. This is described in more detail in WO 99/03454 and in Mathiowitz et al., Nature 386: 410 (1997). It is anticipated that this approach will have a number of advantages over other approaches for delivering exendin-4 orally. For example, dried hydrogels are very adhesive to wet tissue. The microparticles will bind well to the GI tract and will be transported into the system via the gastrointestinal circulation or release their contents on the intestinal mucosa; in turn, the exendin-4 will enter the systemic and gastrointestinal circulation. Chemical enhancers, or formulations containing compositions that utilize specific and non-specific biological transport mechanisms to facilitate transport across the GI tract into the systemic circulation, can be included as well.

Inhalation The use of the hydrogel particles of the invention can enhance the delivery of exendin-4 to the lung. Administration to the lung provides for the delivery of exendin-4 that can be transported across the lung tissue barriers and into circulation, as described WO 99/03454. A problem with the delivery of exendin-4 to the lung is that pulmonary macrophages can take up the therapeutic articles, thus preventing the exendin-4 from entering into systemic and local circulation. Uptake occurs when proteins adsorbed to the article's surface bind with receptors of the pulmonary macrophages. To prevent uptake, the invention provides nonionic hydrogels, e.g., formed with polymers based on polyethylene glycol. These hydrogels adsorb low levels of proteins and thus bind poorly to cell surfaces. Anionic hydrogels, e.g., formed with polyacrylic acid, also adsorb relatively low levels of proteins and thus bind poorly to cell surfaces. In a further embodiment, biocompatible microcapsules may be formed and the surface provided with water soluble non-ionic polymers such as polyethylene oxide (PEO), to create resistance to cell adhesion, as described in U.S. Patent No. 5,380,536, incorporated herein by reference. The size and density of the articles can also be selected to maximize the quantity of exendin-4 that is delivered to the lung. For example, the macrophages will not take up large particles as efficiently as they will take up small particles. However, large particles are not delivered to the deep lung as well as small particles are. To overcome these conflicting factors, the invention provides small particles that can swell as they hydrate. The particles are administered to the deep lung as small (i.e., 1-5 μm), dry, or slightly wet, particles; upon hydration, they swell, and therefore become resistant to uptake by the pulmonary macrophages. The swelling can occur when the particles are hydrated from the dry state and when they are hydrated from one state of hydration to another by a change in temperature, pH, salt concentration, or the presence of other solvents, for example, depending upon the chemical and physical nature of the hydrogel polymer. In addition to particles, the polymer may be provided in other shapes suitable for delivery to the deep lung. For example, PEG emulsion microspheres are subjected to high pressure and a vacuum onto a flat plate to form very light very thin layers, for example, having a snow flake consistency, that react differently to fluidic wind forces. The resulting thin flakes can be, e.g., 0.01 μm, 1 μm, or 10 μm thick. The particles can be administered to the respiratory system alone, or in any appropriate pharmaceutically acceptable excipient, such as a liquid, for example, saline, or a powder. Aerosol dosages, formulations and delivery systems may be selected for a particular therapeutic application (see, for example, Gonda "Aerosols for delivery of therapeutic and diagnostic agents to the respiratory tract," Critical Reviews in Therapeutic Drug Carrier Systems, 6:273 (1990); and "Aerosols in Medicine. Principles, Diagnosis and Therapy," Moren, et al., Eds., Elsevier, Amsterdam, 1985). Pulmonary drug delivery may be achieved using devices such as liquid nebulizers, aerosol-based metered dose inhalers, and dry powder dispersion devices. For the use of dry powder dispersion devices, the polymer particle incorporating the therapeutic agent is formulated as a dry powder, for example, by lyophilization or spray-drying. Methods for preparing spray-dried, pharmaceutical-based dry powders including a pharmaceutically acceptable amount of a therapeutic agent and a carrier are described in PCT WO 96/32149, hereby incorporated by reference. The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the methods and compounds claimed herein are performed, made, and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention.

Examples

Example 1: Controlled Release Formulation of GLP-1. The process of making controlled release formulation of GLP-1 (SEQ ID NO. 2: His-Ala-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu- Gly-Gln-Ala-Ala-Lys-Glu-Phe-Ile-Ala-Trp-Leu-Val-Lys-Gly-Arg-NH₂) involves two steps, making a salt of the peptide and encapsulating the salt in a therapeutic article. First, a GLP-1 salt was created using 2-acrylamido-2-methyl-l- propanesulfonic acid (AMPS). GLP-1 (between 25 and 50 mg) was dissolved in 1 mL 10 mM PBS buffer. The pH was adjusted to 5.5 by addition of AMPS (50 to 100 mg) until the GLP-1 /AMPS salt precipitates from the solution. The solution was decanted and the precipitate lyophilized. The lyophilized GLP- 1/AMPS salt was then used in the encapsulation procedure. Second, 4.4kC5-A3 macromer (1 g) was weighed into a 15 mL centrifuge tube which was heated with a heating block at 50 C until the macromer completely melted. 2,2-dimethaoxy 2-phenyl acetophenone (DMPA) in 1,4 dioxane (0.125 g of a 15% solution) was added to the melted macromer. This was followed by GLP-1 /AMPS salt (50 mg) and the mixture was heated at 50 C for 2-5 minutes until the contents turned into a viscous liquid. The viscous liquid was transferred into a 3-mL syringe and released into a solution of polypropylene glycol (PPG) forming an emulsion. During the process of emulsification, one can control the size of the particles by adjusting the flow rates of the oil and macromer phases. In this process, we used a rate of 25 mL/min for the PPG (oil) and 1 ml/min for the melted macromer liquid. The emulsion was collected in a beaker after flowing through two static mixers and then exposed to long wave ultra violet light (LWUV) for 1 hour to crosslink the macromer using radical polymerization. The resulting microspheres were washed with hexane and 10 mM citrate buffer at pH 6.0. The microspheres were freeze-dried and tested in vitro using a fluidized bed column with 10 mM PBS buffer at pH 7.4 with a flow of 5 mL/day. The collected buffer was tested for GLP-1 using reverse phase column chromatography. The results are summarized in FIG. 1. Exendin-4 is similar in size and composition to GLP-1 and can be formulated as described above, with the substitution of exendin-4 for GLP-1, to make the articles of the invention. Other Embodiments All publications, patent applications, and patents mentioned in this specification are herein incorporated by reference. While the invention has been described in connection with specific embodiments, it will be understood that it is capable of further modifications. Therefore, this application is intended to cover any variations, uses, or adaptations of the invention that follow, in general, the principles of the invention, including departures from the present disclosure that come within known or customary practice within the art. Other embodiments are within the clai s. What we claim is:

Claims

Claims 1. A therapeutic article comprising exendin-4 within a polymerized macromer, the macromer comprising at least one water soluble polymer region, at least one degradable polymer region which is hydrolyzable under in vivo conditions, and polymerized end groups, wherein the polymerized end groups are separated by at least one degradable polymer region and wherein said article when fully hydrated comprises at least 35% (w/w) polymerized macromer.

2. The article of claim 1 , wherein said article when fully hydrated comprises less than 50% (w/w) water.

3. The article of claim 1 , wherein said macromer comprises: (a) a region forming a central core; (b) at least two degradable regions attached to said core; and (c) at least two polymerized end groups, wherein said polymerized end groups are attached to said degradable regions.

4. The article of claim 3, wherein said central core comprises a polymer selected from the group consisting of poly(ethylene glycol), poly(ethylene oxide), poly( vinyl alcohol), poly(vinylpyrrolidone), poly(ethyloxazoline), poly(ethylene oxide)-co-poly(propylene oxide) block copolymers, polysaccharides, carbohydrates, proteins, and combinations thereof.

5. The article of claim 3, wherein said degradable regions comprise a polymer selected from the group consisting of poly(α-hydroxy acids), poly(lactones), poly(amino acids), poly(anhydrides), poly(orthoesters), poly(orthocarbonates), and poly(phosphoesters).

6. The article of claim 5, wherein said poly(α-hydroxy acid) is selected from the group consisting of poly(glycolic acid), poly(DL-lactic acid), and poly(L-lactic acid).

7. The article of claim 5, wherein said poly(lactone) is selected from the group consisting of poly(ε-caprolactone), poly(δ-valerolactone), and poly(γ-butyrolactone) .

8. The article of claim 7, wherein said degradable regions comprise poly(caprolactone) .

9. The article of claim 3, wherein said polymerized end groups are the product of a reaction between carbon-carbon double bonds capable of polymerizing said macromer.

10. The article of claim 3, wherein said macromer comprises: (a) a water soluble region comprising three-armed poly(ethylene glycol); (b) lactate groups attached to the region in (a); and (c) acrylate groups capping the region in (b).

11. The article of claim 3, wherein said macromer is comprises: (a) a water soluble region comprising three-armed poly(ethylene glycol); (b) caprolactone groups on either side of region in (a); and (c) acrylate groups capping either side of the region in (b).

12. The article of claim 1, wherein the article releases 5% of the releasable exendin-4 from the article at a time greater than 1/16 of t₅₀.

13. The article of claim 1, wherein said article comprises at least 0.1% exendin-4 by dry weight.

14. The article of claim 13, wherein said article comprises at least 5% exendin-4 by dry weight.

15. The article of claim 14, wherein said article comprises at least 10% exendin-4 by dry weight.

16. The therapeutic article of claim 1, wherein said article is formed by a method comprising the following steps: (a) heating the macromer until it melts; (b) forming a mixture of exendin-4 and melted macromer; and (c) polymerizing the mixture to form said article.

17. The article of claim 16, wherein the method further comprises the step of forming particles of said article.

18. A method for making a controlled release therapeutic article for delivery of exendin-4, said article comprising exendin-4 within a polymerized macromer, the macromer comprising at least one water soluble polymer region, at least one degradable polymer region which is hydrolyzable under in vivo conditions, and polymerized end groups, wherein the polymerized end groups are separated by at least one degradable polymer region, said method comprising the steps of: (a) heating the macromer until it melts; (b) forming a mixture of exendin-4 and melted macromer; and (c) polymerizing the mixture to form said therapeutic article.

19. The method of claim 18, wherein the mixture of step (b) is emulsified prior to step (c).

20. The method of claim 18, wherein the mixture of step (b) comprises an exendin in the fonn of particles having a mean size of 0.02 to 10 microns.

21. The method of claim 18, wherein said article when fully hydrated comprises at least 35% (w/w) polymerized macromer.

22. The method of claim 18, wherein said article when fully hydrated comprises less than 50% (w/w) water.

23. A method for delivering exendin-4 to a mammal, said method comprising administering the article of claim 1 to said mammal.

24. The method of claim 23, wherein said article is administered to the lung of said mammal.

25. The method of claim 23, wherein said article is administered intravenously.

26. The method of claim 23, wherein said article is administered subcutaneously.

27. The method of claim 23, wherein said article is administered intramuscularly.

28. The method of claim 23, wherein said article is administered orally.

29. The method of claim 23, wherein said article is administered nasally.

30. The method of claim 23, wherein said mammal is a human.

31. The method of claim 23, wherein said mammal has diabetes mellitus.

32. The method of claim 23, wherein said mammal has impaired glucose tolerance.

33. The method of claim 23, wherein said mammal is obese.

34. The method of claim 23, wherein said mammal is hyperglycemic.

35. The method of claim 23, wherein said mammal has dyslipidemia.

36. The method of claim 23, wherein said mammal has cardiovascular disease.