NZ286487A - Method of forming an in situ implant using a thermoplastic polymer - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £86487 New Zealand No. 286487 International No. PCT/ TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates: 28.10.1991; Complete Specification Filed: 30.09.1992 Classification:^) A61L27/00; A61F2/02 Publication date: 24 November 1997 Journal No.: 1422 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: Method of using biodegradable polymer composition Name, address and nationality of applicant(s) as in international application form: ATRIX LABORATORIES, INC., a Delaware corporation of 2579 Midpoint Drive, Fort Collins, Colorado 80525, United States of America 28 6487 UtttSer prwistow <* Reg*- k'icn 25 the ••••••' t»«L Patents Form No. 5 Our Ref: GL206315 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION METHOD OF USING BIODEGRADABLE POLYMER COMPOSITION Divisional out of New Zealand patent application No. 244581 filed on 30 September 1992 We, ATRIX LABORATORIES, INC., a corporation under the state of Delaware, USA of 2579 Midpoint Drive, Fort Collins, Colorado 80525, United States Of America, hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: \ \ (followed by page la) PT0580954 \ METHOD OF USING BIODEGRADABLE POLYMER COMPOSITION Background of the Invention Polymeric implants are useful as delivery systems and/or as mechanical barriers. Implants such as preformed membranes or films have been described.

However, many of these implants have limited properties and produce inferior results either as mechanical barriers or delivery systems.

Several implant techniques' have been used in medical and dental applications. One application of interest is the use of implants in treatment of periodontal disease. Surgery alone does not result in restoration of lost periodontium. Successful periodontal restoration is known to occur if periodontal ligament cells are allowed to colonize root surfaces preferentially over gingival epithelial cells, gingival fibroblasts or osteoblasts. Microporous membranes, such as the Millipore® filter and GORE-TEX® membranes, have been used for periodontal tissue regeneration. Typically, the periodontal flap is cut, and the membrane is surgically inserted to cover the surface of the tooth root and to physically occlude epithelial cells from apically migrating along the root surface.

Those membranes, however, have several drawbacks. Besides variable results, a second surgical entry is needed to remove the membrane after tissue regeneration has been achieved because the membranes are not biodegradable. There is also a higher incidence of infection in connection with their use.

To preclude surgical removal of the implant, membranes made of bioabsorbable material, such as microfibrillar collagen, polylactic acid, and polygalactia (Vicryl®) mesh have been used. Results have been variable, and the therapeutic effect of these membranes has been unpredictable. In addition, fitting and positioning these membranes to the implant site is time-consuming and cumbersome. The degradation time of 286487 -la- (followed by page 2) 28 6 4 & 7 2 membranes composed of collagen has been variable, and the risk of adverse immunological reaction to this foreign protein material in the body presents a major concern.

An object of the invention of New Zealand Patent Application No. 244581, from which this application has been divided, is to provide a composition comprising a biodegradable or bioerodible polymer for use as an implant in an animal including a human. Another object is the development of an implant that will eliminate the need for its surgical removal after its purpose has been achieved. Another object of NZ 244581 is to provide a composition which may be administered to an implant site in liquid form and which is capable of solidifying in situ to form an implant.

It is an object of NZ 244581 and this invention to provide a biodegradable implant which may be used to enhance connective cell or tissue growth and deter growth of epithelial cells and tissue into the core of the implant. Another object of these inventions is to provide an implant which is capable of delivery of a drug or other medicament over a desired period of time. A further object of these inventions is to provide an implant for providing controlled release delivery of at least one biologically-active agent for stimulation and/or enhancement of physiological or biological activity in an animal. flmirniflty of the Invention These and other goals are achieved by the present invention which is directed to the use, in the manufacture of an iirplant for altering a biological or physiological activity in an animal, of composition for providing in situ a biodegradable or bioerodible microporous matrix. The matrix may be used to deliver biologically-active substances and/or for selective enhancement of cell growth and tissue regeneration in animals.

The composition is a liquid formulation of a biocompatible and biodegradable or bioerodible thermoplastic or thermoset polymer or copolymer which is I—r~r- I w./. J~ Q''^ »|- r; substantially insoluble in aqueous media and bodyj [ 2 8 AUG t9S7 286487 3 fluids. The liquid formulations may be of varying viscosities and conform to the shape of the cavities to which they are placed. The composition may include a separate pore-forming agent which is capable of generating additional pores within the polymer matrix.

When a biologically-active agent is to be released by the matrix, the agent is dissolved in the composition to form a homogenous solution or dispersed in the composition to form a suspension.

More particularly, the invention relates to the use, in the manufacture of a solid or gelatinous implant for altering a biological or physiological activity in an animal, of a biodegradable, bioerodible, thermoplastic polymer that is insoluble in aqueous media or body fluids, in a fluid composition in combination with an organic solvent that is miscible to dispersible in aqueous media or body fluids wherein the thermoplastic polymer coagulates or solidifies to form the solid or gelatinous implant in situ upon placement of the composition within a body as the organic solvent dissipates or disperses into body fluids, the implant having a core containing pores of diameters from 10 to 1000 microns surrounded by a skin containing pores of smaller diameters than the pores of the core.

The invention provides a use of a composition in the manufacture of an implant for preventing and treating diseases and disorders, such as diseases of the bone and connective tissue, infectious diseases, cancer, metabolic disorders and allergies. The invention also provides a use of a composition in the manufacture of an implant for tissue regeneration useful in wound and organ repair, nerve regeneration, periodontium regeneration, and bone regeneration. The invention also provides a use of a composition in the manufacture of an implant for altering the physiological or biological activity of an animal such as reproductive function. (followed •by-page • -3-a} 2 8 AUG 3a 286 48 7 Thermoplastic polymer compositions Accc^rdinq to a first embodiment of the invention of NZ 244581, the composition is a liquid formulation of a thermoplastic polymer and a pharmaceutically acceptable organic solvent. The composition is administered as a liquid to an implant, site, whereupon the solvent diffuses or dissipates into the surrounding aqueous tissue fluids. The thermoplastic polymer is not soluble in these aqueous fluids so that it coagulates or solidifies to form a microporous solid or gelatinous matrix. The matrix preferably has a two-layered pore structure composed of a core portion and an outer surface layer or skin. The polymer matrix is suitable for use as an in situ formed implant in an animal, including humans and other mammals. The composition may be administered to tissue, to a surgical incision, or to a void space in tissue such as a periodontal pocket, and the like. jy_p_age_4) hU3 1387 286487 4 Thermoset polymer compositions According to. a second embodiment of the invention of NZ 244581, the composition is a liquid formulation of thermoset prepolymer or copolymer, preferably an acrylic ester-terminated biodegradable prepolymer, which is capable of cross-linking in situ to form a polymeric or copolymeric solid or gelatinous matrix. The composition preferably is a neat liquid but may include a pharmaceutically acceptable organic solvent that is miscible with water and body fluids.

When the thermoset polymer composition is cross-linked in situ, the resulting matrix is rendered microporous by one of several means. Use of a small but suitable amount of organic solvent will produce pores as described above for the thermoplastic polymer. The prepolymer ingredients may release a pore-forming moiety such as carbon dioxide and the like, or a separate pore-forming agent may be included. The pore-forming agent may be any suitable organic or inorganic substance which is soluble or substantially miscible in water and tissue fluids, and substantially miscible or dispersible in the thermoset polymer composition.

The thermosetting polymer composition may include a curing agent, such as a catalyst, which is capable of enhancing the cross-linking reaction of prepolymers. The curing agent is biocompatible.

Preferred catalysts include benzoyl peroxide and azobisisobutyronitrile.

Porosity of the polymer matrices Several factors influence the size, or diameter, of the pores formed in the polymer matrix of the implant. In the polymer matrices formed from the thermoplastic polymer composition and from the thermoset polymer composition containing solvent or pore-forming moiety, the action of the solvent (or pore-forming moiety), as it diffuses out of the coagulating or 28 6487 solidifying polymer matrix and into the surrounding tissue fluids, generates pores in the matrix and produces a two-component structure. The outer component is a surface skin which surrounds the inner component or core. The core contains pores of diameter from about 10 to 1000 p while the skin is functionally non-porous in comparison with the core. In fact, the skin has pores which are significantly smaller in diameter than those of the core.

The addition of a pore-forming agent to the thermoplastic polymer composition and the use of a pore-forming agent as part of the thermoset polymer composition will produce a matrix having about the same diameter pores throughout the core and skin. The size and/or quantity of a pore-forming agent included in the polymer matrix, and the distribution of the pore-forming agent within • he polymer matrix, among other factors, may also influence pore size and porosity of the polymer matrix.

Where the implant is employed for the purpose of tissue regeneration, as for example, to promote guided tissue regeneration of periodontal tissue, it is preferred that the diameter of the pores in the matrix be effective to deter growth of epithelial cells into the polymer matrix of the implant, and enhance growth of connective tissue cells into the matrix. It is further preferred that the size of the pores and porosity of the matrix of the implant facilitate diffusion of nutrients and other growth-promoting substances such as growth factors, to cells which have grown into the matrix. Preferably, the size of the pores in the polymer matrix is about 3-500 microns, more preferably about 3-200 microns, and most preferably about 75-150 microns.

It is further preferred that the degree of porosity of the matrix provides an implant which is capable of substantially maintaining structural ^18 6 4 8 7 integrity for the desired period of time without breakage or fracturing during use.

Bioloqicallv-active Agent 5 The composition may further contain at least one biologically-active agent which is capable of providing a biological, physiological or therapeutic effect in an animal. For example it may enhance cell growth and tissue regeneration, act for birth control, cause nerve stimulation or bone growth. The agent may also stimulate other desired biological or physiological activity within the animal. Accordingly, NZ 244581 and this invention provides an in situ formed implant capable of functioning as a delivery system of drugs, medicaments 15 and other biologically-active agents to tissues adjacent to or distant from the implant site. The biologically-active agent is preferably incorporated into the polymer matrix, and subsequently released into surrounding tissue fluids and to the pertinent body tissue or organ.

Administration of the Composition The composition of NZ 244581 may be administered to the implant site by any suitable method for applying a 25 liquid, as for example, by means of a syringe, needle, cannula, catheter, pressure applicator, and the like.

In one embodiment, the composition may be administered by means of a syringe directly into integral tissue or into a void or hole such as a periodontal pocket or 30 surgical incision, wherein the mixture in situ forms a solid implant conforming to the shape or the contour of the site. Advantageously, the composition of NZ 244581 is useful in overcoming placement difficulties inherent with solid forms of implants. , 3 This invention provides the use of a composition in the manufacture of an implant for altering a biological or physiological activity in an animal. Treatment involves—,-——. administering to an animal, l ~~ " — f j 2 s AUS 1997 286487 7 one of the foregoing compositions in an amount effective to form a solid microporous matrix implant in the animal. The matrix, optionally containing at least one biologically-active agent, is capable of enhancing cell growth and/or tissue formation such as bone or nerve formation, or altering a biological or physiological activity in an animal such as reproductive function and the like.

Detailed Description of the Invention The composition of the invention of NZ 244581 nay be used to provide a biodegradable or bioerodible microporous in situ formed implant in animals. The composition is composed of either a thermoplastic polymer or copolymer in combination with a suitable solvent, or a thermosetting polymer or copolymer containing or combined with a pore-forming means. The polymers or copolymers are substantially insoluble in water and body fluids, biocompatible, and biodegradable and/or bioerodible within the body of an animal. The compositions are administered as a- liquid to tissue wherein the implant is formed in situ. The composition is biocompatible and the polymer matrix does not cause substantial tissue irritation or necrosis at the implant site. The implant has a variety of uses, as for example, for enhancing cell growth and tissue regeneration, and delivery of biologically-active agents such as drugs and medicaments.

Thermoplastic polymer composition Thermoplastic polymers useful in the composition of the invention of NZ 244581 include pharmaceutically compatible polymers that are bioerodible by cellular action, are biodegradable by action of non-living body fluid components, soften when exposed to heat but return to the original state when cooled and are capable of substantially dissolving or dispersing in a water- 286487 8 miscible carrier or solvent to form a solution or dispersion. Upon contact with an aqueous fluid and the dissipation of the solvent component, the thermoplastic polymers are capable of coagulating or solidifying to 5 form a solid or gelatinous matrix suitable for use as an implant in an animal.

The kinds of thermoplastic polymers suitable for the conposition of NZ 244581 generally include any having the foregoing characteristics. Examples aire 10 polylactides, polyglycolides, polycaprolactones, polyanhydrides, polyamides, polyurethanes, polyesteramides, polyorthoesters, polydioxanones„ polyacetals, polyketals, polycarbonates, polyorthocarbonates, polyphosphazenes, polyhydroxy-15 butyrates, polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates, poly(amino acids), poly(methyl vinyl ether), poly(maleic.anhydride), and copolymers , terpolymers, or combinations or mixtures therein. Polylactides, polycaprolactones, polyglycolides and copolymers thereof are highly'preferred thermoplastic polymers.

The thermoplastic polymer La combined with a suitable organic solvent to form a solution. The solubility or miscibility of a polymer in a particular solvent will vary according to factors such as crystallinity, hydrophilicity, capacity for hydrogen-bonding and molecular weight of the polymer. Consequently, the molecular weight and the concentration of the polymer in the solvent are adjusted to achieve desired miscibility. Highly preferred thermoplastic polymers are those which have a low degree of crystallization, a low degree of hydrogen-bonding, low solubility in water, and high solubility in organic solvents. 286487 Thermoset polymer compositions The composition of NZ 244581 may as well be a liquid formulation of a thermosetting oligomeric prepolymer or copolymer which is capable of cross-linking 5 or hardening to provide a microporous gelatinous or solid matrix suitable for use as an implant in an animal, including a human. The thermosetting prepolymers and resulting cross-linked polymers and copolymers are biocompatible, and biodegradable and/or 10 bioerodible.

The pre-polymers are preferably low molecular weight polymers or oligomers having end functional groups that are reactive with acryloyl chloride to produce acrylic ester-terminated pre-polymers. Acrylic 15 pre-polymers for use in the compositions may be synthesized according to a variety of methods including, but not limited to, reaction of a carboxylic acid, such as acrylic or roethacrylic acid, with an alcohol? reaction of a carboxylic acid ester, such as methyl 20 acrylate or methyl methacrylate, with an alcohol by transesterification; and reaction of an isocyanatoalkyl acrylate, such as isocyanatoethyl methacrylate, with an alcohol.

The thermosetting prepolymers are also short 25 chain polyol derivatives of the thermoplastic polymers described herein. The polyol terminated derivatives are converted to acrylic ester terminated prepolymers by any suitable method. Examples are short chain polyol derivatives of polylactides, polyglycolides, 30 polycaprolactones, polyanhydrides, polyamides, polyurethanes, polyesteramides, polyorthoesters, polydioxanones, polyacetals, polyketals, polycarbonates, polyorthocarbonates, polyphosphazenes, polyhydroxy-butyrates, polyhydroxyvalerates, polyalkylene oxalates, 35 polyalkylene succinates, poly(malic acid), poly(amino acids), poly(methyl vinyl ether), poly(maleic 28 6487 anhydride), chitin, chitosan, and copolymers, terpolymers, or combinations or mixtures therein.

A preferred polymer matrix and implant prepared with thermosetting prepolymers is composed of poly(DL-lactide-co-caprolactone) (DL-PLC). To prepare the DL-PLC polymer matrix, DL-lactide or L-lactide and 7-caprolactone are co-polymerized in the presence of a multifunctional polyol initiator and a curing agent to produce hydroxy-terminated PLC prepolymers. This polyol-terminated pre-polymer is then converted to an acrylic ester-terminated pre-polymer by any suitable method, as for example, by acylation of the alcohol terminus with acryloyl chloride by means of, for example, a Schotten-Baumann technique (reaction of acyl halide with alcohol).

Optionally, a curing agent, such as a catalyst, may be added to the acrylic pre-polymer mixture to enhance cross-linking of the pre-polymers and the subsequent coagulation or solidification of the resulting polymer to form a matrix. For example, the acrylic pre-polymer, in an amount of about 5 grams, may be added to a solution of benzoyl peroxide (BP) in about 1 ml of CH2C12. Optionally, other acrylic monomers may be added to the acrylic pre-polymer mixture before adding the curing agent. The acrylic pre-polymer mixture may be cured in air at room temperature, or in a preheated vacuum oven.

Preferred catalysts for the preparation of the PLC prepolymers are basic or neutral ester-interchange (transesterification) catalysts, as for example, metallic esters of carboxylic acids containing up to 18 carbon atoms, formic, acetic, lauric, stearic, and benzoic acid. Preferred catalysts include, for example, stannous octoate and stannous chloride.

A multi-functional polyol chain initiator may be included in the thermosetting polymer compositions to vary the molecular weight and composition of the 28 6487 11 polymer. For example, a bifunctional chain initiator such as ethylene glycol, may be included to produce a bifunctional polymer, or a trifunctional initiator, such as trimethylolpropane, may be used to produce a trifunctional polymer. Furthere the molecular weight of the polymer or co-polymer may be varied according to the concentration of the chain initiator in the composition. For example, a high concentration of a bifunctional chain initiator may make available an initiator molecule for each polymer chain, while a low concentration may contain one initiator molecule for every two polymer chains.

Following the addition of the curing agent, the pre-polymer polymer mixture preferably remains in liquid form for a period of time effective to allow administration of the composition to the implant site, thereafter, the cross-linking reaction preferably continues until a solid or gelatinous polymer matrix is produced. Accordingly, the pre-polymer mixture cures, or solidifies, in situ to form a polymer matrix which is capable of biodegradation and/or bioabsorption over time.

The thermoset polymer composition contains one or more materials to form the microporous matrix. The polymer itself can contain moieties that are released as volatile substances during cross-linking to cause pore-formation. Alternatively, the composition can contain a minimum amount of suitable, biocompatible organic solvent as described below, or can contain a separate pore-forming agent as discussed below. The thermoset polymers containing releaseable moieties are known in the art.

Solvents Solvents suitable for the thermoplastic polymer composition are those which are biocompatible, preferably pharmaceutically acceptable, miscible with 12 28 6 48 7 the polymer component and water, and capable of diffusing into tissue fluids surrounding the implant site. Preferably, the solvent has a Hildebrand (HLB) solubility ratio of from about 9(cal/cm3)35 to 5 ^(cal/cm3)3*. The degree of polarity of the solvent should be effective to provide at least about 10% solubility in water, and to dissolve or disperse the polymer component into solution.

The composition is . administered to the implant site in liquid form, whereupon the solvent diffuses into the adjacent tissue fluids. Upon contact with the surrounding aqueous fluids, the polymer moiety coagulates or solidifies to form a solid or gelatinous matrix fitting the usually 15 irregular shape of the incision or void of the implant site. Preferably, the solvent quickly diffuses into the surrounding tissue fluids to enhance formation of the polymer matrix following administration of the composition to the implant site. Preferably, the 20 polymer matrix is capable of adhering to the adjacent tissue by mechanical forces to at least partially bond or attach the implant to the adjacent tissue, and/or mechanically bond two tissues together. The concentration of polymer in solvent for the composition 25 will generally accomplish rapid and effective dissipation of the solvent and coagulation of the polymer. This concentration may range from 0.0lg of polymer per ml of solvent to a saturated concentration whereby the formulation may be highly viscous such as a gel or putty or paste, preferably from O.lg per ml to saturation. 30 Solvents which may be used in the thermoplastic polymer composition of the invention include, for example, N-methyl-2—pyrrolidone, 2-pyrrolidone, C-3 to Cg alkanols, acetone, alkyl esters such as methyl acetate, ethyl acetate, ethyl lactate, alkyl 35 ketones such as methyl ethyl ketone, dialkylamides such as dimethyl formamide, dimethyl sulfoxide, dimethyl sulfone, tetrahydrofuran, cyclic alkyl amides sufii .as ~ O p t};\ 0 fWl) l^j'j { 286487 13 caprolactam, decvlmethylsulfoxide, oleic acid, propylene carbonate, aromatic amides such as N,N-diethyl-m-toluamide, and l-dodecylazacycloheptan-2-one. Preferred solvents according to the invention include N-methyl-2-5 pyrrolidone, 2-pyrrolidone, dimethyl sulfoxide, acetone, and propylene carbonate.

A mixture of solvents may be used to increase the coagulation rate of polymers which exhibit a slow coagulation or setting rate. For example, the polymer 10 may be combined with a coagulant-promoting solvent system composed of a mixture of a good solvent and a poorer solvent or a non-solvent for the polymer component. It is preferred that the solvent mixture contain an effective amount of the two solvents such 15 that the polymer will remain soluble in the mixture but coagulate upon dissipation or diffusion of the solvents into surrounding tissue fluids at the implant site.

The same solvents can also be combined with the thermoset polymer composition. In this variation, the 20 solvent does not form the liquid character of the composition. The prepolymer itself is liquid. Instead the solvent acts to produce the two component porous matrix discussed below. The solvent concentration is at a minimum for such purpose and is preferably inert 25 toward the cross-linking reaction. The solvent diffuses as the prepolymer hardens to form the solid implant matrix. The organic solvent is included in the thermosetting polymer composition in an amount suitable to form pores but not high enough to substantially 30 dilute the pre-polymer ingredient to a condition where it only lightly cross-links.

Pore-formation and porosity Upon contact with an aqueous body fluid or 35 water, the thermoplastic polymer composition of NZ 244581 coagulates or solidifies to form a microporous gelatinous or solid matrix. Similarly, the thermoset polymer composition 14 28 6487 hardens to form a microporous solid matrix. In either variation, pores may be formed within the matrix by several means. Dissipation, dispersement or diffusion of the solvent or released moiety (thermoset polymer) 5 out of the solidifying polymer matrix or hardening polymer matrix (thermoset polymer) and into the adjacent tissue fluids may generate pores, including pore channels, in the polymer matrix.

Diffusion of the solvent or released moiety 10 produces a thermoplastic or thermoset polymer matrix having a two component structure, that is, an inner core portion or layer, and an outer surface portion or skin. The pores of the core are substantially uniform while by comparison with the porous nature of the core, the skin 15 is essentially non-porous. In fact, the skin has pores with diameters significantly smaller in size than those iri the core.

Pore-forming agent 20 In either the thermoplastic or thermoset polymer composition of NZ -244581, a pore-^forming agent may be included to generate additional pores in the polymer matrix. The pore-forming agent is biocompatible, and soluble in body fluids and water as well as in the 25 organic solvents. The pore-forming agent is further capable of diffusing or dispersing out of the coagulating polymer matrix and into the adjacent fluids, whereupon pores are generated in the polymer matrix.

The pore-forming agent, when combined with the 30 thermoplastic polymer and solvent or with the thermoset polymer optionally containing a minimal amount of solvent, preferably forms a uniform mixture with the polymer either as a dispersion or suspension, or as a solution. When the mixture is administered to an 35 implant site, the solvent and/or pore-forming agent preferably dissipate or diffuse into surrounding tissue fluids causing the formation of microporous channels 286487 within the coagulating polymer matrix. Optionally, the pore-forming agent may become incorporated into the polymer matrix, and dissipate into the surrounding tissue fluids at a rate slower than that of the solvent, 5 or be released from the matrix by biodegradation or bioerosion. The porous matrices formed through the inclusion of a pore-forming agent have a pore structure in which the pores are substantially similar in size throughout the matrix structure.

Preferably, the pore-forming agent is combined with the thermoplastic polymer and solvent, or the thermoset pre-polymer or copolymer mixture before the matrix is formed. The pore-forming agent may form a mixture solution or dispersion with the polymer. 15 Pore-forming agents include, any pharmaceutically acceptable organic or inorganic water-soluble substance that is substantially miscible in water and body fluids and will dissipate from the in situ formed matrix into body fluids. The pore-forming 20 agent may also be a water-immiscible substance that rapidly degrades to a water-soluble substance. In the thermoplastic polymer composition of NZ 244581, it is further preferred that the pore-forming agent is v- miscible or dispersible in the organic solvent to form a 25 uniform mixture with the polymer moiety. Suitable pore-forming agents include, for example, sugars such as sucrose and dextrose, salts such as sodium chloride and sodium carbonate, and polymers such as hydroxylpropylcellulose, carboxymethylcellulose, 30 polyethylene glycol, and polyvinylpyrrolidone.

The concentration of pore-forming agent relative to polymer in the composition will vary according to the degree of pore-formation desired.

Generally, this concentration will range from O.Olg of 35 pore-forming agent per gram of polymer to about lg per gram. 286487 16 The size or diameter of the pores formed in the matrix may be modified by the size and/or distribution of the pore-forming agent within the polymer matrix. For example, pore-forming agents which are relatively 5 insoluble in the polymer mixture, may be selectively included in the composition according to particle size to generate pores having a diameter which corresponds to the size of the pore-forming agent. Pore-forming agents which are soluble in the polymer mixture may vary the 10 pore size and porosity of the polymer matrix according to the pattern of distribution and/or aggregation within the mixture and resulting polymer matrix.

The concentration of water-soluble components/ such as the solvent and/or pore-forming agent, in the 15 composition may vary the porosity of the polymer matrix. For example, a composition having a high concentration of water-soluble substances may produce a polymer matrix having a high degree of porosity.

To provide an effective implant for bone cell 20 regrowth and tissue regeneration, it is preferred that the diameter of the pores be about 3-500 microns, more preferably about 3-200 microns, and most preferably 75-150 microns. It is further preferred that the matrix has a porosity of about 5-95%, preferably about 25-85% 25 in order to provide optimum cell and tissue ingrowth into the matrix and optimum structural integrity.

Pore diameter and distribution within the polymer matrix may be measured, as for example, according to scanning electron microscopy methods by 30 examination of cross-sections of the polymer matrix.

Porosity of the polymer matrix may be measured according to any suitable method, as for example, mercury intrusion porosimetry, specific gravity or density comparisons, calculation from scanning electronic 35 microscopy photographs, and the like. Additionally, porosity may be calculated according to the proportion or percent of water-soluble material included in the 286487 17 polymer composition. For example, a composition which contains about 30% polymer and about 70% solvent and/or other water-soluble components will generate a polymer matrix having about 70% porosity.

Preferably, the pore-forming agent is dissipated immediately from the polymer matrix to generate a matrix having a porosity and pore structure effective to perform the particular purpose of the impiant, as for example, a tissue regeneration site or a matrix for timed-release of a drug or medicament.

Implant for tissue regeneration The composition of. NZ 244581 may be administered to an implant site, as for example, whole tissue or tissue with a void such as a periodontal pocket, a soft-tissue defect, a surgical incision, and the like. When the composition is administered to a tissue regeneration site, it is preferred that the implant provides a surface to facilitate the growth of regenerative tissue. For example, to enhance regeneration of hard tissue such as bone tissue, it is preferred that the polymer matrix will provide a support for new bone cell growth which will replace the matrix as it is gradually absorbed or eroded by body fluids.

The microporous polymer matrix is capable of biodegradation and/or bioabsorption within the implant site. According to NZ 244581, the particular polymer and the molecular weight of the polymer may vary in the composition according to a desired duration or time interval of the degradation or bioerosion of the polymer matrix, as for example, a few weeks or several years. When the implant is used to enhance cell growth and tissue regeneration, it is preferred that the matrix disintegrate at a rate effective to allow replacement of the matrix by cell growth from the adjacent cells or tissue. 28 6487 18 Biologically-active agent The in situ formed implants may also provide a delivery system for biologically-active agents to adjacent or distant body tissues and organs. 5 Biologically-active agents which may be used alone or in combination in the present compositions and implants include medicaments, drugs, or any suitable biologically-, physiologically- or pharmacologically-active substance which is capable of providing local or 10 systemic biological or physiological activity in an animal, including a human, and which is capable of being released from the polymer matrix into an adjacent or surrounding aqueous fluid.

The biologically-active agent may be miscible 15 in the polymer and/or solvent to provide a homogenous mixture with the polymer, or insoluble in the polymer and/or solvent to form a suspension or dispersion with the polymer. It is highly preferred that the biologically-active agent be combined with the 20 thermosetting polymer composition almost immediately prior to administration of the composition to the implant site. It is further preferred that the bioactive agent will not contain functional groups which will interfere with the cross-linking reaction of the 25 thermoset polymer. These conditions are readily determined by those of skill in the art simply by comparing the structure of the bioactive agent and the reacting moieties of the thermoset polymer.

Upon administration of the composition to the 30 implant site, the biologically-active agent preferably becomes incorporated into the polymer matrix. As the matrix biodegrades and/or bioerodes, the biologically-active agent may be released from the matrix into the adjacent tissue fluids. Preferably, the 35 biologically-active agent is released into the surrounding tissue fluids at a controlled rate. For example, the polymer matrix may be formulated to degrade 286487 19 after an effective and/or substantial amount of the biologically-active agent is released from the matrix. Release of a biologically-active agent having a low solubility in water, as for example a peptide or protein, may require the degradation of a substantial part of the polymer matrix to expose the agent directly to the surrounding tissue fluids. Thus, the release of the biologically-active agent from the matrix may be varied by, for example, the solubility of the biologically-active agent in water, the distribution of the biologically-active agent within the matrix, or the size, shape, porosity, solubility and biodegradability of the polymer matrix, among other factors.

The composition and in situ formed implant contain the biologically-active agent in an amount effective to provide a desired biological, physiological, pharmacological and/or therapeutic effect, optionally according to a desired release profile, and/or time duration of release. It is further preferred that the biologically-active agent is included in the polymer composition in an amount effective to provide an acceptable solution or dispersion viscosity.

In addition, the biologically-active agent may act as a pore-forming agent, or substance capable of generating pores in the polymer matrix of the implant. To enhance selective cell growth into the matrix, for example, it is preferred that the bioactive agent is released from the polymer matrix at a rate corresponding to that of cell migration and growth into newly formed pores of the matrix.

The biologically-active agent may also be a substance, or metabolic precursor thereof, which is capable of promoting growth and survival of cells and tissues, or augmenting the activity of functioning cells, as for example, blood cells, neurons, muscle, bone marrow, bone cells and tissues, and the like. For example, the biologically-active agent may be a nerve 286487 growth promoting substance, as for example, a ganglioside, phosphatidylserine, a nerve growth factor, brain-derived neurotrophic factor, a fibroblast growth factor, and the like. In particular, the in situ 5 implants are capable of enhancing regeneration of the periodontium by providing an outer surface having a porosity which serves as a physical barrier between an exposed root surface and encroaching epithelial cells to promote guided tissue regeneration. 10 To promote tissue growth, the biologically- active agent may be either a hard or soft tissue promoting substance or combinations thereof. Suitable tissue growth promoting agents include, for example, fibronectin (FN), endothelial cell growth factor (ECGF), 15 cementum attachment extracts (CAE), human growth hormone (HGH), a Periodontal ligament cell growth factor, fibroblast growth factor (FGF), animal growth hormones, platelet derived growth factor (PDGF), epidermal growth factor (EGF), protein growth factor interleukin-1 (IL-20 1), transforming growth factor (TGF/3-2), insulin-like growth factor II (ILGF-II), human alpha thrombin (HAT), osteoinductive factor (OIF), bone morphogenetic protein (BMP) or protein derived therefrom, demineralized bone matrix, and releasing factors thereof. 25 Further, the agent may be a bone growth promoting substance such as hydroxyapatite, tricalcium phosphate, a di- or polyphosphonic acid, an anti-estrogen, a sodium fluoride preparation, a substance having a phosphate to calcium ratio similar to natural 30 bone, and the like. A bone growth promoting. substance may be in the form, as for example, of bone chips, bone crystals or mineral fractions of bone and/or teeth, a synthetic hydroxyapatite, or other suitable form. The agent may further be capable of treating metabolic bone 35 disorders such as abnormal calcium and phosphate metabolism by, for example, inhibiting bone resorption, mw 21 promoting bone mineralization, or inhibiting calcification.

See, for example, U.S. Patent No. 4,939,131 to Benedict et al., U.S. Patent No. 4,942,157 to Gall et 5 al., U.S. Patent No. 4,894,373 to Young, U.S. Patent No. 4,904,478 to Walsdorf et al., and U.S. Patent No. 4,911/931 to Baylink, U.S. Patent No. 4,916,241 to Hayward et al., U.S. Patent No. 4,921,697 to Peterlik et al., U.S. Patent No. 4,902,296 to Bolander et al., U.S. 10 Patent No. 4,294,753 to Urist, U.S. Patent No. 4,455,256 to Urist, U.S. Patent No. 4,526,909 to Urist, U.S.

Patent No. 4,563,489 to Urist, U.S. Patent No. 4,596,574 to Urist, U.S. Patent No. 4,619,989 to Urist, U.S.

Patent No. 4,761,471 to Urist, U.S. Patent No. 4,789,732 15 to Urist, U.S. Patent No. 4,795,804 to Urist, and U.S.

Patent No. 4,857,456 to Urist, the disclosures of which axe incorporated by reference herein.

Suitable biologically-active agents also include substances useful in preventing infection at the 20 implant site, as for example, antiviral, antibacterial, antiparasitic, antifungal substances and combinations thereof. The agent may further be a substance capable of acting as a stimulant, sedative, hypnotic, analgesic, anticonvulsant, and the like.

The delivery system can contain a large number of biologically-active agents either singly or in combination. Examples of these biologically-active agents include, but are not limited to: Anti-inflammatory agents such as 30 hydrocortisone, prednisone, fiudrotisone, triamcinolone, dexamethasone, betamethasone and the like.

Anti-bacterial agents such as penicillins, cephalosporins, vancomycin, bacitracin, polymycins, 35 tetracyclines, chloramphenicol, erythromycin, streptomycin, and the like. 286487 22 Antiparasitic agents such as quinacrine, chloroquine, quinine, and the like.

Antifungal agents such as nystatin, gentamicin, miconazole, tolnaftate, undecyclic acid and its salts, and the like.

Antiviral agents such as vidarabine, acyclovir, ribarivin, amantadine hydrochloride, iododeoxyuridine, dideoxyuridine, interferons and the like.

Antineoplastic agents such as methotrexate, 5-fluorouracil, bleomycin, tumor necrosis factor, tumor specific antibodies conjugated to toxins, and the like.

Analgesic agents such as salicylic acid, salicylate esters and salts, acetaminophen, ibuprofen, morphine, phenylbutazone, indomethacin, sulindac, tolmetin, zomepirac, and the like.

Local anaesthetics such as cocaine, benzocaine, novocaine, lidocaine, and the like.

Vaccines such as hepatitis, influenza, measles, mumps, rubella, hemophilus, diphtheria, tetanus, rabies, polio, and the like.

Central nervous system agentu such as tranquilizers, sedatives, anti-depressants, hypnotics, B-adrenergic blocking agents, dopamine, and the like.

Growth factors such as colony stimulating factor, epidermal growth factor, erythropoietin, fibroblast growth factor, neural growth factor, human growth hormone, platelet derived growth factor, insulin-like growth factor, and the like.

Hormones such as progesterone, estrogen, testosterone, follicle stimulating hormone, chorionic gonadotrophin, insulin, endorphins, somatotropins and the like. 23 Antihistamines such as diphenhydramine, chlorpheneramine, chlorcyclizine, promethazine, cimetidine, terfenadine, and the like.

Cardiovascular agents such as verapamil hydrochloride, digitalis, streptokinase, nitroglycerine papaverine, disopyramide phosphate, isosorbide dinitrate, and the like.

Anti-ulcer agents such as cimetidine hydrochloride, isopropamide iodide, propantheline bromide, and the like.

Bronchodilators such as metaproteraal sulfate, aminophylline, albuterol, and the like.

Vasodilators such as theophylline, niacin, nicotinate esters, amylnitrate, minoxidil, diazoxide, nifedipine, and the like.

The biologically-active agent may be included in the compositions in the form of, for example, an uncharged molecule, a molecular complex, a salt, an ether, an ester, an amide, or other form to provide the effective biological or physiological activity.

Administration of the composition of NZ 244581 ultimately will be accomplished according to the wisdom and protocol of the patient's attending health care professional such as a physician, or if appropriate, a dentist. Choice of the particular composition will depend upon the malcondition or condition to be treated, which choice will be made by the attending health care professional. Application by syringe, or other means for applying a liquid to or into a tissue may be employed. Without a bioactive agent, the composition can function as a structure for promotion of cell growth and tissue repair. With a bioactive agent, the composition will not only function in such capacity but will also adopt the properties of the bioactive agent.

The amounts and concentrations of composition administered to the patient will generally be sufficient 286487 24 to accomplish the task intended. If that task is void space filling, enough composition will be administered to accomplish this task. For administration of bioactive agent, the amounts and release rates will 5 follow recommendations of the manufacturer of the bioactive agent. Generally, the concentration of bioactive agent in the liquid polymer mixture will be from O.Olmg per g of mixture to 400mg per g of mixture.

Advantageously, the polymer compositions may be 10 administered to an implant site, as for example, by injection with a syringe, whereupon the composition will solidify in situ. The resulting implant may thus be administered to an implant site without the need for surgical incision.

The invention will be described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the scope of the claims.

The invention is described with reference particularly to Examples 11 to 14. Examples 1 to 10 refer to the preparation of the polymers as described in WO 9101126..

EXAMPLE 1 A mixture comprising about 5% equimolar mixture of sodium carbonate and citric acid, about 34.8% poly(DL-lactide) (DL-PLA) and about 60.2% N-methyl pyrrolidone (NMP) was prepared by suspending sodium carbonate and citric acid in the polymer solution. The DL-PLA polymer had a molecular weight of about 30,000 daltons (inherent viscosity of 0.38 dL/g).

One drop of the mixture was precipitated into a vial containing phosphate-buffered saline (PBS) or water. The vial was placed in a 37°C shaker bath for about 48 hours. The sample was then removed from the bath, and dried in vacuo prior to examination by Scanning Electron Microscopy (SEM). The resulting article was porous with pores of about 5m in diameter, and a porosity of about 65%. 286487 EXAMPLE 2 A mixture comprising about 5% sucrose, about 34.8% DL-PLA and about 60.2% NMP was prepared according to Example 1. A porous article was produced having 5 pores of about 3p in diameter and a porosity of about 65%.

EXAMPLE 3 A mixture comprising about 5% poly(vinyl 10 pyrrolidone)(PVP), about 34.8% DL-PLA and about 60.2% NMP was prepared according to Example 1. A porous article was produced having pores of about 5-10p in diameter and a porosity of about 65%.

EXAMPLE 4 A mixture comprising about 10% PVP, about 33.0% DL-PLA, and about 57.0% NMP was prepared according to Example 1. A porous article was produced having pores of about 5-2Op in diameter and a porosity of about 65%.

EXAMPLE 5 In this example, a mixture was prepared comprising about 50% of two different molecular weights of DL-PLA and about 50% NMP. A water-soluble, 25 low molecular weight DL-PLA (molecular weight of about 2000 daltons) was mixed with a higher molecular weight DL-PLA with an inherent viscosity of 0.38 dL/g (molecular weight of about 30,000 daltons). The DL-PLA mixture was dissolved in NMP to provide a mixture 30 comprised of about 38% low molecular weight DL-PLA, about 12% higher molecular weight DL-PLA, and about 50% NMP. This mixture was then precipitated, incubated and dried according to Example 1. A porous article was producing having pores of about 10-50p in diameter, and 35 about 50% porosity. 286487 26 EXAMPLE 6 A mixture comprising about 5% ethoxydihydrosanguinarine (SaOEt), 27.5% DL-PLA and 67.5% NMP was prepared according to Example 1. SaOEt is 5 an antimicrobial agent derivable from benzophenanthridine alkaloids. A porous article was produced having pores of about 15-30^ in diameter and about 70% porosity.

EXAMPLE 7 A mixture comprising about 5% SaOEt, 27.5% DL-PLA and 67.5% NMP was prepared according to Example 1, the DL-PLA component having a molecular weight of about 10,000 daltons. A porous article was produced having 15 pores of about 4-8p in diameter. A wet sample of the article was examined by X-ray tomography by scanning at intervals of about 0-25 mm. The articles showed porosity throughout with about 70% porosity.

EXAMPLE B An implant comprising about 5.0% sanguinarine chloride (SaCl), about 47.5% DL-PLA, and about 47.5% NMP was administered to a periodontal pocket of a human patient. SaCl is an antimicrobial and anti-inflammatory 25 agent derivable from benzophenanthridine alkaloids.

After 28 days, the implant was removed, dried in vacuo and examined by SEM. Pores having a diameter of about 1-2jj and of about 10-20y were detected. Approximately 50% of the pores were 10-20ji. The implant had a total 30 porosity of about 50%.

EXAMPLE 9 A mixture comprising about 33% PVP, about 33% 50/50 copolymer of DL-lactide and glycolide (DL-PLG), 35 and about 34% NMP was prepared according to Example 1. A porous article was produced having pores of about 3-10/j. Examination of the article showed that the pores 286481 27 were arranged in an interconnecting network. The article had a porosity of about 65%.

EXAMPLE 10 A lyophilized sample of fibronectin, a tissue growth and cell attachment factor, was added to a solution of DL-PLA in NMP to provide a dispersion comprising about 13.2% wt-% lyophilized fibronectin, about 30.4 wt-% DL-PLA, and about 56.4 wt-% NMP. As a 10 result of the lyophilization process, the lyophilized fibronectin contained various salts with only about 0.89% active component. This dispersion was added to a phosphate-buffered receiving solution wherein it coagulated into a solid matrix. The receiving solution 15 was maintained at 37°C under agitation and changed periodically to preclude a high concentration of fibronectin within the receiving solution. The receiving solution was analyzed for total protein concentration by the Pierce BCA protein assay. The 20 cumulative percentage of fibronectin released from the matrix was calculated. About 12% of the fibronectin component was released after one day, about 25% after 2 days, about 26% after 3 days, about 28% after 4 days, 30% after 5 days, and 33% after 7 days. The porosity of 25 the solid matrix of the implant was initially about 55%.

The porosity level of the matrix increased as the fibronectin component was released over time. The pores of greater than 3/j in diameter were produced by the dissolving fibronectin component.

EXAMPLE 11 Norethindrone and ethinylestradiol, birth control agents, may be added to a solution of DL-PLA in NMP to provide a liquid mixture containing about 10% 35 wt.% norethindrone, about 1 wt.% ethinylestradiol, about 33 wt.% DL-PLA and about 56 wt.% NMP. The mixture can then be injected under the skin of an animal where it 286487 28 coagulates to form a solid microporous implant. Levels of norethindrone and ethinylestradiol in the blood can be measured over time. The effect on rates of pregnancy can also be measured. The implant advantageously 5 functions to release birth control agents continuously over time and does not have to be removed by surgery.

EXAMPLE 12 Terfenadine, an antiallergy medication, may be 10 added to a solution of DL-PLA in NMP to provide a liquid mixture containing about 10 wt.% terfenadine, about 33 wt.% DL-PLA and 57 wt.% NMP. The mixture can then be injected under the skin of an animal where it coagulates to form a solid microporous implant. The level of 15 terfenadine in the blood can be measured over time. The efficacy of the implant in controlling allergy symptoms can also be measured.

EXAMPLE 13 Bone chips and bone morphogenetic protein can be added to form a liquid mixture containing about 10 wt.% bone chips, about 1 wt.% bone morphogenetic protein, about 5 wt.% PVP, about 33 wt.% DL-PLA, and about 51 wt.% NMP. The mixture can then be injected to 25 fill in a bone defect in a crushed cheekbone. The mixture coagulates in situ, conforming to the shape of the site, and filling in the damaged tissue. Healing and regeneration of bone tissue can be monitored over time.

EXAMPLE 14 Ovine follicle stimulating hormone, an ovulation stimulatory agent, may be added to form a liquid mixture containing about 2 wt.% ovine follicle stimulating hormone, about 41 wt.% DL-PLA, and about 57 35 wt.% NMP. The solution can be injected subdermally into a cow to form a solid microporous implant. The ovulation rate can be measured 4-6 days after oestrus.

Claims (1)

1. WHAT WE CLAIM IS: 29 286 48 7 The use, in the manufacture of a solid or gelatinous implant for altering a biological or physiological activity in an animal, of a biodegradable, bioerodible, thermoplastic polymer that is insoluble in aqueous media or body fluids, in a fluid composition in combination with an organic solvent that is miscible to dispersible in aqueous media or body fluids wherein the thermoplastic polymer coagulates or solidifies to form the solid or gelatinous implant in situ upon placement of the composition within a body as the organic solvent dissipates or disperses into body fluids, the implant having a core containing pores of diameters from 10 to 1000 microns surrounded by a skin containing pores of smaller diameters than the pores of the core. ' 1 The use. according to claim i, wherein the implant is capable of enhancing tissue regeneration. 4 The use' according to claim 1, wherein the implant is capable of filling in defects in tissue. The use according to claim 1, wherein the composition further comprises at least one biologically-active agent. The use according to claim 4, wherein the biologically-active agent is selected from the group consisting of anti-inflammatory agents, antibacterial agents, antiparasitic agents, antifungal agents, antiviral agents, anti-neoplastic agents, analgesic agents, anaesthetics, vaccines, central nervous system agents, growth factors, hormones, antihistamines, osteoinductive agents, cardiovascular agents, anti-ulcer agents, bronchodilators, vasodilators, birth control agents, and fertility enhancing agents. ! 2 8 AU5 1S97 30 "286 48 7 The use according to claim 4, wherein the biologically-active agent is capable of altering the biological or physiological action of the reproductive system. The use, in the manufacture of a solid or gelatinous implant for altering a biological or physiological activity in an animal, of a biodegradable, bioerodible, thermoplastic polymer that is insoluble in aqueous media or body fluids, in a fluid composition in combination with an inert carrier wherein the thermoplastic polymer undergoes curing to form a solid or gelatinous implant in situ upon placement of the composition within a body, the implant having a core containing pores of diameters from 10 to 1000 microns surrounded by a skin containing pores of smaller diameters than the pores of the core. The use, in the manufacture of a solid or gelatinous implant for altering a biological or physiological activity in an animal, substantially as herein described with reference to Examples 11-14. END OF CLAIMS