Patent 6,726,918

Methods for treating inflammation-mediated conditions of the eye are described, comprising: implanting into the vitreous of the eye of an individual a bioerodible implant comprising a steroidal anti-inflammatory agent and a bioerodible polymer, wherein the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours and maintains a concentration equivalent to at least about 0.03 .mu.g/ml dexamethasone for at least about three weeks.

DISCLOSURE OF THE INVENTION

The present invention provides a method for treating an inflammation-mediated condition of the eye, comprising: implanting into the vitreous of the eye a bioerodible implant comprising a steroidal anti-inflammatory agent and a bioerodible polymer, wherein the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours and maintains a concentration equivalent to at least about 0.03 .mu.g/ml dexamethasone for at least about three weeks.

In another embodiment of the invention, a method for treating an inflammation-mediated condition of the eye is provided, comprising: implanting a solid body into the vitreous of the eye, said body comprising particles of a steroidal anti-inflammatory agent entrapped within a bioerodible polymer, whereby said agent is released from the body by erosion of the polymer, and whereby said agent is delivered to the vitreous at a rate and for a time sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours, and maintains a concentration equivalent to at least about 0.03 .mu.g/ml dexamethasone for at least about three weeks.

In another embodiment of the invention, a method for treating an inflammation-mediated condition of the eye is provided, comprising: implanting into the vitreous of the eye a bioerodible implant comprising a steroidal anti-inflammatory agent and a bioerodible polymer, wherein the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.2 .mu.g/ml dexamethasone within about 6 hours and maintains a concentration equivalent to at least about 0.01 .mu.g/ml dexamethasone for at least about three weeks.

In another embodiment of the invention, a method for treating an inflammation-mediated condition of the eye is provided, comprising: implanting a solid body into the vitreous of the eye, said body comprising particles of a steroidal anti-inflammatory agent entrapped within a bioerodible polymer, whereby said agent is released from the body by erosion of the polymer, and whereby said agent is delivered to the vitreous at a rate and for a time sufficient to reach a concentration equivalent to at least about 0.2 .mu.g/ml dexamethasone within about 6 hours, and maintains a concentration equivalent to at least about 0.01 .mu.g/ml dexamethasone for at least about three weeks.

MODES FOR CARRYING OUT THE INVENTION

Methods for Treating an Inflammation-Mediated Condition

Intraocular glucocorticoid drug delivery systems made of a biodegradable polymer matrix have been developed which can release drug loads over various programmed time periods. These drug delivery systems which when inserted into the vitreous provide therapeutic levels of glucocorticoid for extended periods of time (e.g., 3 weeks or more). In particular, these delivery systems provide an initial "loading dose" level of drug of at least about 0.05 .mu.g/ml dexamethasone equivalent to the posterior segment of the eye. These delivery systems have shown unexpected results in treating diseases such as uveitis and PVR.

Accordingly, the present invention provides a method for treating an inflammation-mediated condition of the eye, comprising: implanting into the vitreous of the eye a bioerodible implant comprising a steroidal anti-inflammatory agent and a bioerodible polymer, wherein the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours and maintains a concentration equivalent to at least about 0.03 .mu.g/ml dexamethasone for at least about three weeks.

In another embodiment of the invention, a method for treating an inflammation-mediated condition of the eye is provided, comprising: implanting a solid body into the vitreous of the eye, said body comprising particles of a steroidal anti-inflammatory agent entrapped within a bioerodible polymer, whereby said agent is released from the body by erosion of the polymer, and whereby said agent is delivered to the vitreous at a rate and for a time sufficient to reach a concentration equivalent to at least about 0.2 .mu.g/ml dexamethasone within about 6 hours, and maintains a concentration equivalent to at least about 0.01 g/ml dexamethasone for at least about three weeks.

Preferred inflammation-mediated conditions of the eye which may be treated by the methods of the invention include uveitis, macular edema, acute macular degeneration, retinal detachment, ocular tumors, fungal or viral infections, multifocal choroiditis, diabetic uveitis, proliferative vitreoretinopathy (PVR), sympathetic opthalmia, Vogt Koyanagi-Harada (VKH) syndrome, histoplasmosis, and uveal diffusion. In a preferred embodiment, the inflammation-mediated condition of the eye is uveitis. In another preferred embodiment, the inflammation-mediated condition of the eye is proliferative vitrioretinopathy (PVR).

The delivery systems are designed to release the glucocorticoid at therapeutic levels to the vitreous for a sustained period of time. In one embodiment, the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours. In other embodiments, the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.06 .mu.g/ml, at least about 0.07 .mu.g/ml, at least about 0.08 .mu.g/ml, at least about 0.1 .mu.g/ml, at least about 0.125 .mu.g/ml, at least about 0.15 .mu.g/ml dexamethasone within about 48 hours.

In another embodiment, the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.2 .mu.g/ml dexamethasone within about 6 hours. In other embodiments, the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.3 .mu.g/ml, at least about 0.5 .mu.g/ml, at least about 0.75 .mu.g/ml, at least about 1.0 .mu.g/ml, at least about 2.0 .mu.g/ml dexamethasone within about 4 hours, within about 6 hours, within about 8 hours, within about 10 hours, within about 24 hours.

A concentration equivalent to at least about 0.01 .mu.g/ml, at least about 0.02 .mu.g/ml, at least about 0.03 .mu.g/ml, at least about 0.05 .mu.g/ml, at least about 0.07 .mu.g/ml dexamethasone may be maintained for an extended period of time (e.g., at least about three weeks.) The preferred concentration levels of drug in the vitreous may vary according to the inflammatory mediated condition being treated. For treating uveitis, a concentration equivalent of at least about 0.01 to 0.1 .mu.g/ml dexamethasone is preferred.

In one embodiment, said concentration is maintained for least about four weeks. In other embodiments, said concentration is maintained for at least about five weeks, at least about six weeks, at least about seven weeks, at least about eight weeks, at least about nine weeks, at least about 10 weeks, at least about 12 weeks. The preferred duration of drug release may be determined by the inflammatory mediated condition being treated. For treating uveitis, a drug release duration of at least about three weeks is preferable, more preferably at least about four weeks. In one embodiment, more than one implant may be sequentially implanted into the vitreous in order to maintain drug concentrations for even longer periods.

The implants may be inserted into the eye by a variety of methods, including placement by forceps or by trocar following making a 2-3 mm incision in the sclera. The method of placement may influence the drug release kinetics. For example, implanting the device with a trocar may result in placement of the device deeper within the vitreous than placement by forceps, which may result in the implant being closer to the edge of the vitreous. The location of the implanted device may influence the concentration gradients of drug surrounding the device, and thus influence the release rates (e.g., a device placed closer to the edge of the vitreous will result in a slower release rate).

Implants for Use in Treating Inflammatory-Mediated Conditions

The formulation of the implants for use in the invention may vary according to the preferred drug release profile, the particular glucocorticoid used, the condition being treated, and the medical history of the patient.

The implants of the invention are formulated with particles of the steroidal anti-inflammatory agent entrapped within the bioerodible polymer matrix. Release of the agent is achieved by erosion of the polymer followed by exposure of previously entrapped agent particles to the vitreous, and subsequent dissolution and release of agent. The release kinetics achieved by this form of drug release are different than that achieved through formulations which release drug through polymer swelling, such as with hydrogels such as methylcellulose. In that case, the drug is not released through polymer erosion, but through polymer swelling, which releases drug as liquid diffuses through the pathways exposed. The parameters which determine the release kinetics include the size of the drug particles, the water solubility of the drug, the ratio of drug to polymer, the method of manufacture, the surface area exposed, and the erosion rate of the polymer.

Preferably, the steroidal anti-inflammatory agent is selected from the group consisting of 21-acetoxypregnenolone, alclometasone, algestone, amcinonide, beclomethasone, betamethasone, budesonide, chloroprednisone, clobetasol, clobetasone, clocortolone, cloprednol, corticosterone, cortisone, cortivazol, deflazacort, desonide, desoximetasone, dexamethasone, diflorasone, diflucortolone, difluprednate, enoxolone, fluazacort, flucloronide, flumethasone, flunisolide, fluocinolone acetonide, fluocinonide, fluocortin butyl, fluocortolone, fluorometholone, fluperolone acetate, fluprednidene acetate, fluprednisolone, flurandrenolide, fluticasone propionate, formocortal, halcinonide, halobetasol propionate, halometasone, halopredone acetate, hydrocortamate, hydrocortisone, loteprednol etabonate, mazipredone, medrysone, meprednisone, methylprednisolone, mometasone furoate, paramethasone, prednicarbate, prednisolone, prednisolone 25-diethylamino-acetate, prednisolone sodium phosphate, prednisone, prednival, prednylidene, rimexolone, tixocortol, triamcinolone, triamcinolone acetonide, triamcinolone benetonide, and triamcinolone hexacetonide. In a preferred embodiment, the steroidal anti-inflammatory agent is selected from the group consisting of cortisone, dexamethasone, hydrocortisone, methylprednisolone, prednisolone, prednisone, and triamcinolone. In a more preferred embodiment, the steroidal anti-inflammatory agent is dexamethasone. In another embodiment, the bioerodible implant comprises more than one steroidal anti-inflammatory agent.

The implants may further comprise one or more additional therapeutic agents, such as antimetabolites and/or antibiotics. Antimetabolites include, but are not limited to, folic acid analogs (e.g., denopterin, edatrexate, methotrexate, piritrexim, pteropterin, Tomudex.RTM., trimetrexate), purine analogs (e.g., cladribine, fludarabine, 6-mercaptopurine, thiamiprine, thiaguanine), and pyrimidine analogs (e.g., ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, doxifluridine, emitefur, enocitabine, floxuridine, fluorouracil, gemcitabine, tegafur). Specific antibiotics include, but are not limited to:

Antibacterial antibiotics:

Aminoglycosides (e.g., amikacin, apramycin, arbekacin, bambermycins, butirosin, dibekacin, dihydrostreptomycin, fortimicin(s), gentamicin, isepamicin, kanamycin, micronomicin, neomycin, neomycin undecylenate, netilmicin, paromomycin, ribostamycin, sisomicin, spectinomycin, streptomycin, tobramycin, trospectomycin), amphenicols (e.g., azidamfenicol, chloramphenicol, florfenicol, thiamphenicol), ansamycins (e.g., rifamide, rifampin, rifamycin sv, rifapentine, rifaximin), .beta.-lactams (e.g., carbacephems (e.g., loracarbef), carbapenems (e.g., biapenem, imipenem, meropenem, panipenem), cephalosporins (e.g., cefaclor, cefadroxil, cefamandole, cefatrizine, cefazedone, cefazolin, cefcapene pivoxil, cefclidin, cefdinir, cefditoren, cefepime, cefetamet, cefixime, cefinenoxime, cefodizime, cefonicid, cefoperazone, ceforanide, cefotaxime, cefotiam, cefozopran, cefpimizole, cefpiramide, cefpirome, cefpodoxime proxetil, cefprozil, cefroxadine, cefsulodin, ceftazidime, cefteram, ceftezole, ceftibuten, ceftizoxime, ceftriaxone, cefuroxime, cefuzonam, cephacetrile sodium, cephalexin, cephaloglycin, cephaloridine, cephalosporin, cephalothin, cephapirin sodium, cephradine, pivcefalexin), cephamycins (e.g., cefbuperazone, cefinetazole, cefininox, cefotetan, cefoxitin), monobactams (e.g., aztreonam, carumonam, tigemonam), oxacephems, flomoxef, moxalactam), penicillins (e.g., amdinocillin, amdinocillin pivoxil, amoxicillin, ampicillin, apalcillin, aspoxicillin, azidocillin, azlocillin, bacampicillin, benzylpenicillinic acid, benzylpenicillin sodium, carbenicillin, carindacillin, clometocillin, cloxacillin, cyclacillin, dicloxacillin, epicillin, fenbenicillin, floxacillin, hetacillin, lenampicillin, metampicillin, methicillin sodium, mezlocillin, nafcillin sodium, oxacillin, penamecillin, penethamate hydriodide, penicillin g benethamine, penicillin g benzathine, penicillin g benzhydrylamine, penicillin g calcium, penicillin g hydrabamine, penicillin g potassium, penicillin g procaine, penicillin n, penicillin o, penicillin v, penicillin v benzathine, penicillin v hydrabamine, penimepicycline, phenethicillin potassium, piperacillin, pivampicillin, propicillin, quinacillin, sulbenicillin, sultamicillin, talampicillin, temocillin, ticarcillin), other (e.g., ritipenem), lincosamides (e.g., clindamycin, lincomycin), macrolides (e.g., azithromycin, carbomycin, clarithromycin, dirithromycin, erythromycin, erythromycin acistrate, erythromycin estolate, erythromycin glucoheptonate, erythromycin lactobionate, erythromycin propionate, erythromycin stearate, josamycin, leucomycins, midecamycins, miokamycin, oleandomycin, primycin, rokitamycin, rosaramicin, roxithromycin, spiramycin, troleandomycin), polypeptides (e.g., amphomycin, bacitracin, capreomycin, colistin, enduracidin, enviomycin, fusafungine, gramicidin s, gramicidin(s), mikamycin, polymyxin, pristinamycin, ristocetin, teicoplanin, thiostrepton, tuberactinomycin, tyrocidine, tyrothricin, vancomycin, viomycin, virginiamycin, zinc bacitracin), tetracyclines (e.g., apicycline, chlortetracycline, clomocycline, demeclocycline, doxycycline, guamecycline, lymecycline, meclocycline, methacycline, minocycline, oxytetracycline, penimepicycline, pipacycline, rolitetracycline, sancycline, tetracycline), and others (e.g., cycloserine, mupirocin, tuberin).

Synthetic antibacterials:

2,4-Diaminopyrimidines (e.g., brodimoprim, tetroxoprim, trimethoprim), nitrofurans (e.g., furaltadone, furazolium chloride, nifuradene, nifuratel, nifurfoline, nifurpirinol, nifurprazine, nifurtoinol, nitrofuirantoin), quinolones and analogs (e.g., cinoxacin, ciprofloxacin, clinafloxacin, difloxacin, enoxacin, fleroxacin, flumequine, grepafloxacin, lomefloxacin, miloxacin, nadifloxacin, nalidixic acid, norfloxacin, ofloxacin, oxolinic acid, pazufloxacin, pefloxacin, pipemidic acid, piromidic acid, rosoxacin, rufloxacin, sparfloxacin, temafloxacin, tosufloxacin, trovafloxacin), sulfonamides (e.g., acetyl sulfamethoxypyrazine, benzylsulfamide, chloramine-b, chloramine-t, dichloramine t, n² -formylsulfisomidine, n⁴ -.beta.-d-glucosylsulfanilamide, mafenide, 4'-(methylsulfamoyl)sulfanilanilide, noprylsulfamide, phthalylsulfacetamide, phthalylsulfathiazole, salazosulfadimidine, succinylsulfathiazole, sulfabenzamide, sulfacetamide, sulfachlorpyridazine, sulfachrysoidine, sulfacytine, sulfadiazine, sulfadicramide, sulfadimethoxine, sulfadoxine, sulfaethidole, sulfaguanidine, sulfaguanol, sulfalene, sulfaloxic acid, sulfamerazine, sulfameter, sulfamethazine, sulfamethizole, sulfamethomidine, sulfamethoxazole, sulfamethoxypyridazine, sulfametrole, sulfamidochrysoidine, sulfamoxole, sulfanilamide, 4-sulfanilamidosalicylic acid, n⁴ -sulfanilylsulfanilamide, sulfanilylurea, n-sulfanilyl-3,4-xylamide, sulfanitran, sulfaperine, sulfaphenazole, sulfaproxyline, sulfapyrazine, sulfapyridine, sulfasomizole, sulfasymazine, sulfathiazole, sulfathiourea, sulfatolamide, sulfisomidine, sulfisoxazole) sulfones (e.g., acedapsone, acediasulfone, acetosulfone sodium, dapsone, diathymosulfone, glucosulfone sodium, solasulfone, succisulfone, sulfanilic acid, p-sulfanilylbenzylamine, sulfoxone sodium, thiazolsulfone), and others (e.g., clofoctol, hexedine, methenamine, methenamine anhydromethylene-citrate, methenamine hippurate, methenamine mandelate, methenamine sulfosalicylate, nitroxoline, taurolidine, xibomol).

Antifungal antibiotics:

Polyenes (e.g., amphotericin b, candicidin, dermostatin, filipin, fungichromin, hachimycin, hamycin, lucensomycin, mepartricin, natamycin, nystatin, pecilocin, perimycin), others (e.g., azaserine, griseofulvin, oligomycins, neomycin undecylenate, pyrrolnitrin, siccanin, tubercidin, viridin).

Synthetic antifungals:

Allylamines (e.g., butenafine, naftifine, terbinafine), imidazoles (e.g., bifonazole, butoconazole, chlordantoin, chlormidazole, cloconazole, clotrimazole, econazole, enilconazole, fenticonazole, flutrimazole, isoconazole, ketoconazole, lanoconazole, miconazole, omoconazole, oxiconazole nitrate, sertaconazole, sulconazole, tioconazole), thiocarbamates (e.g., tolciclate, tolindate, tolnaftate), triazoles (e.g., fluconazole, itraconazole, saperconazole, terconazole) others (e.g., acrisorcin, amorolfine, biphenamine, bromosalicylchloranilide, buclosamide, calcium propionate, chlorphenesin, ciclopirox, cloxyquin, coparaffinate, diamthazole dihydrochloride, exalamide, flucytosine, halethazole, hexetidine, loflucarban, nifuratel, potassium iodide, propionic acid, pyrithione, salicylanilide, sodium propionate, sulbentine, tenonitrozole, triacetin, ujothion, undecylenic acid, zinc propionate).

Antineoplastic:

Antibiotics and analogs (e.g., aclacinomycins, actinomycin f₁, anthramycin, azaserine, bleomycins, cactinomycin, carubicin, carzinophilin, chromomycins, dactinomycin, daunorubicin, 6-diazo-5-oxo-L-norleucine, doxorubicin, epirubicin, idarubicin, menogaril, mitomycins, mycophenolic acid, nogalamycin, olivomycines, peplomycin, pirarubicin, plicamycin, porfiromycin, puromycin, streptonigrin, streptozocin, tubercidin, zinostatin, zorubicin), antimetabolites (e.g. folic acid analogs (e.g., denopterin, edatrexate, methotrexate, piritrexim, pteropterin, Tomudex.RTM., trimetrexate), purine analogs (e.g., cladribine, fludarabine, 6-mercaptopurine, thiamiprine, thioguanine), pyrimidine analogs (e.g., ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, doxifluridine, emitefur, enocitabine, floxuridine, fluorouracil, gemcitabine, tagafur).

The steroidal anti-inflammatory agent is preferably from about 10 to 90% by weight of the implant. More preferably, the agent is from about 50 to about 80% by weight of the implant. In a preferred embodiment, the agent comprises about 50% by weight of the implant. In a particularly preferred embodiment, the agent comprises about 70% by weight of the implant.

The implants are preferably monolithic, i.e. having the glucocorticoid homogenously distributed through the polymeric matrix. The selection of the polymeric composition to be employed will vary with the desired release kinetics, patient tolerance, the nature of the disease to be treated and the like. Characteristics of the polymers will include biodegradability at the site of implantation, compatibility with the agent of interest, ease of encapsulation, water insolubility, and the like. Preferably, the polymeric matrix will not be fully degraded until the drug load has been released. The polymer will usually comprise at least about 10, more usually at least about 20 weight percent of the implant.

Biodegradable polymeric compositions which may be employed may be organic esters or ethers, which when degraded result in physiologically acceptable degradation products, including the monomers. Anhydrides, amides, orthoesters or the like, by themselves or in combination with other monomers, may find use. The polymers will be condensation polymers. The polymers may be cross-linked or non-cross-linked, usually not more than lightly cross-linked, generally less than 5%, usually less than 1%. For the most part, besides carbon and hydrogen, the polymers will include oxygen and nitrogen, particularly oxygen. The oxygen may be present as oxy, e.g., hydroxy or ether, carbonyl, e.g., non-oxo-carbonyl, such as carboxylic acid ester, and the like. The nitrogen may be present as amide, cyano and amino. The biodegrable polymers set forth in Heller, Biodegrable Polymers in Controlled Drug Delivery, in: CRC Critical Reviews in Therapeutic Drug Carrier Systems, Vol. 1. CRC Press, Boca Raton, Fla. (1987), may be used.

Of particular interest are polymers of hydroxyaliphatic carboxylic acids, either homo- or copolymers, and polysaccharides. Included among the polyesters of interest are polymers of D-lactic acid, L-lactic acid, racemic lactic acid, glycolic acid, polycaprolactone, and combinations thereof. By employing the L-lactate or D-lactate, a slowly biodegrading polymer is achieved, while degradation is substantially enhanced with the racemate. Copolymers of glycolic and lactic acid are of particular interest, where the rate of biodegradation is controlled by the ratio of glycolic to lactic acid. The % of polylactic acid in the polylactic acid polyglycolic acid (PLGA) copolymer can be 0-100%, preferably about 15-85%, more preferably about 35-65%. In a particularly preferred embodiment, a 50/50 PLGA copolymer is used. The most rapidly degraded copolymer has roughly equal amounts of glycolic and lactic acid, where either homopolymer is more resistant to degradation. The ratio of glycolic acid to lactic acid will also affect the brittleness of in the implant, where a more flexible implant is desirable for larger geometries. The size of the polymer particles is preferably about 1-100 .mu.m in diameter, more preferably about 5-50 .mu.m in diameter, more preferably about 9-12 .mu.m in diameter, still more preferably about 10 .mu.m in diameter.

Among the polysaccharides of interest are calcium alginate, and functionalized celluloses, particularly carboxymethylcellulose esters characterized by being biodegradable, water insoluble, a molecular weight of about 5 kD to 500 kD, etc.

Additionally, release modulators such as those described in U.S. Pat. No. 5,869,079 may be included in the implants. The amount of release modulator employed will be dependent on the desired release profile, the activity of the modulator, and on the release profile of the glucocorticoid in the absence of modulator.

Other agents may be employed in the formulation for a variety of purposes. For example, buffering agents and preservatives may be employed. Water soluble preservatives which may be employed include sodium bisulfite, sodium bisulfate, sodium thiosulfate, benzalkonium chloride, chlorobutanol, thimerosal, phenylmercuric acetate, phenylmercuric nitrate, methylparaben, polyvinyl alcohol and phenylethyl alcohol. These agents may be present in individual amounts of from about 0.001 to about 5% by weight and preferably about 0.01 to about 2%. Suitable water soluble buffering agents that may be employed are sodium carbonate, sodium borate, sodium phosphate, sodium acetate, sodium bicarbonate, etc., as approved by the FDA for the desired route of administration. These agents may be present in amounts sufficient to maintain a pH of the system of between 2 to 9 and preferably 4 to 8. As such the buffering agent may be as much as 5% on a weight to weight basis of the total composition. Electrolytes such as sodium chloride and potassium chloride may also be included in the formulation. Where the buffering agent or enhancer is hydrophilic, it may also act as a release accelerator. Hydrophilic additives act to increase the release rates through faster dissolution of the material surrounding the drug particles, which increases the surface area of the drug exposed, thereby increasing the rate of drug bioerosion. Similarly, a hydrophobic buffering agent or enhancer dissolve more slowly, slowing the exposure of drug particles, and thereby slowing the rate of drug bioerosion.

The proportions of glucocorticoid, polymer, and any other modifiers may be empirically determined by formulating several implants with varying proportions. A USP approved method for dissolution or release test can be used to measure the rate of release (USP 23; NF 18 (1995) pp. 1790-1798). For example, using the infinite sink method, a weighed sample of the drug delivery device is added to a measured volume of a solution containing 0.9% NaCl in water, where the solution volume will be such that the drug concentration is after release is less than 5% of saturation. The mixture is maintained at 37^oC. and stirred slowly to maintain the implants in suspension. The appearance of the dissolved drug as a function of time may be followed by various methods known in the art, such as spectrophotometrically, HPLC, mass spectroscopy, etc. until the absorbance becomes constant or until greater than 90% of the drug has been released.

The release kinetics of the drug delivery devices of the invention are dependent in part on the surface area of the devices. Larger surface area exposes more polymer to the vitreous, causing faster erosion and dissolution of the drug particles entrapped by the polymer. The size and form of the implant can be used to control the rate of release, period of treatment, and drug concentration at the site of implantation. Larger implants will deliver a proportionately larger dose, but depending on the surface to mass ratio, may have a slower release rate. The implants may be particles, sheets, patches, plaques, films, discs, fibers, microcapsules and the like and may be of any size or shape compatible with the selected site of insertion, as long as the implants have the desired release kinetics. Preferably, the implant to be inserted is formulated as a single particle. Preferably, the implant will not migrate from the insertion site following implantation. The upper limit for the implant size will be determined by factors such as the desired release kinetics, toleration for the implant, size limitations on insertion, ease of handling, etc. The vitreous chamber is able to accommodate relatively large implants of varying geometries, having diameters of 1 to 3 mm. In a preferred embodiment, the implant is a cylindrical pellet (e.g., rod) with dimensions of about 2 mmx0.75 mm diameter. The implants will also preferably be at least somewhat flexible so as to facilitate both insertion of the implant in the vitreous and accommodation of the implant. The total weight of the implant is preferably about 250-5000 .mu.g, more preferably about 500-1000 .mu.g. In one embodiment, the implant is about 500 g. In a particularly preferred embodiment, the implant is about 1000 .mu.g.

In a preferred embodiment, a solid bioerodible implant for treating an inflammation-mediated condition of the eye is provided, consisting essentially of: dexamethasone particles entrapped within a polylactic acid polyglycolic acid (PLGA) copolymer, wherein the implant comprises about 70 percent by weight of dexamethasone and about 30 percent by weight of PLGA, wherein the total mass of the implant is about 800-1100 .mu.g, and wherein the implant releases at least about 10% of the drug load within 1 week when measured under infinite sink conditions in vitro. In a more preferred embodiment, the total mass of the implant is about 1000 .mu.g. In other embodiments, the implant releases at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, of the drug load within 1 week when measured under infinite sink conditions in vitro. In other embodiments, the implant releases at least about 15%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, of the drug load within 2 weeks when measured under infinite sink conditions in vitro.

Methods for Making the Implants of the Invention

Various techniques may be employed to produce the implants. Useful techniques include phase separation methods, interfacial methods, extrusion methods, compression methods, molding methods, injection molding methods, heat press methods and the like.

Choice of the technique, and manipulation of the technique parameters employed to produce the implants can influence the release rates of the drug. Room temperature compression methods result in an implant with discrete microparticles of drug and polymer interspersed. Extrusion methods result in implants with a progressively more homogenous dispersion of the drug within the polymer, as the production temperature is increased. When using extrusion methods, the polymer and drug are chosen to as to be stable at the temperatures required for manufacturing, usually at least about 85^oC. Extrusion methods use temperatures of about 25^oC. to about 150^oC., more preferably about 65^oC. to about 130^oC. Generally, compression methods yield implants with faster release rates than extrusion methods, and higher temperatures yield implants with slower release rates.

In a preferred embodiment, compression methods are used to produce the implants of the invention. Preferably, compression methods use pressures of 50-150 psi, more preferably about 70-80 psi, even more preferably about 76 psi, and use temperatures of about 0^oC. to about 115^oC., more preferably about 25^oC. In another preferred embodiment, extrusion methods are used. Preferably, implants produced by extrusion methods are heated to a temperature range of about 60^oC. to about 150^oC. for drug/polymer mixing, more preferably about 130^oC., for a time period of about 0 to 1 hour, 0 to 30 minutes, 5-15 minutes, preferably about 10 minutes, preferably about 0 to 5 min. Preferably, the implants are then extruded at a temperature of about 60^oC. to about 130^oC., more preferably about 75^oC.

Kits for the Administration of the Implants

In another aspect of the invention, kits for treating an inflammation-mediated condition of the eye are provided, comprising: a) a container comprising a bioerodible implant comprising dexamethasone and polylactic acid polyglycolic acid (PLGA) copolymer in a ratio of about 70/30; and b) instructions for use.

Claim 1 of 42 Claims

What is claimed is:

1. A method for treating an inflammation-mediated condition of the eye in an individual, comprising: implanting into the vitreous of the eye a bioerodible implant comprising a steroidal anti-inflammatory agent and a bioerodible polymer, wherein the implant delivers the agent to the vitreous in an amount sufficient to reach a concentration equivalent to at least about 0.05 .mu.g/ml dexamethasone within about 48 hours and maintains a concentration equivalent to at least about 0.03 .mu.g/ml dexamethasone for at least about three weeks.

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