Biodegradable microparticles for sustained drug delivery, methods of making and uses thereof

Abstract

In certain embodiments, the present invention relates to biodegradable microparticles for sustained release drug delivery comprising an active agent and a three-dimensional covalently cross-linked polymer matrix, as well as methods of making and uses thereof. Furthermore, in certain embodiments, the present invention relates to pharmaceutically acceptable, biodegradable sustained release drug delivery systems comprising biodegradable microparticles for sustained release drug delivery, in particular for coating or use as medical implants, and methods of making the same. In certain embodiments, the invention also relates to corresponding methods of treatment, methods for controlling the release of an active agent and the use of the biodegradable microparticles for sustained release drug delivery.

Description

Technical Field

[0001] In certain embodiments, the present invention relates to biodegradable microparticles for sustained-release drug delivery, and methods for preparing and using the same, wherein the biodegradable microparticles comprise an active agent and a three-dimensional covalently cross-linked polymer matrix. In addition, in certain embodiments, the present invention relates to pharmaceutically acceptable, biodegradable sustained-release drug delivery systems and methods for making the same, wherein the drug delivery systems comprise biodegradable microparticles for sustained-release drug delivery, particularly for coating medical implants or for use as medical implants. In certain embodiments, the present invention further relates to methods for controlling the release of active agents and the uses of biodegradable microparticles for sustained-release drug delivery. Background Art

[0002] Controlled delivery of therapeutic agents has been a major area of ​​research in recent years. Controlled delivery will improve therapy, facilitate administration, and lead to better compliance, fewer side effects, and better treatment outcomes.

[0003] Sustained delivery of hydrophilic drug compounds from hydrogel-based implants or inserts is often too fast or too slow for the desired duration of treatment. This is because the rate of drug release from water-based hydrogels increases with increasing water solubility. There is a need to eliminate solubility limitations.

[0004] Encapsulating drugs within microparticles of biodegradable polymers can be used to modify the release rate of the contained drug. For example, because the rate of drug release from water-based hydrogels increases with increasing water solubility, incorporating drug-encapsulated microparticles into such hydrogels would make drug release less dependent on the degradation properties of the hydrogel.

[0005] To achieve delayed administration of the active ingredient, sustained-release encapsulation technology for drugs (e.g., drug-loaded microparticles) can be used to encapsulate the drug compound and slowly release it. Commonly used encapsulation materials for forming microparticles are polylactic acid (PLA), polyglycolic acid (PGA), and polylactic-co-glycolic acid (PLGA). These materials are considered biodegradable and have been proven to be safe for human use and have been used in human clinical applications for decades. There are many methods for producing such microparticles, which generally involve precipitating polymer microparticles from polymer solutions.

[0006] Microparticles for drug delivery have been described, for example, in US 2018 / 0085307, WO 2018 / 169950, WO 2021 / 237096, and US 2021 / 0251893. For example, US 2018 / 0085307 and US 2021 / 0251893, incorporated herein by reference, describe the use of biodegradable hydrogel-based sustained-release intracameral implants for treating ocular diseases. The intracameral implants include drug-containing PLA microparticles. The PLA microparticles are prepared from a drug-containing polylactide polymer solution using an oil-in-water emulsion method.

[0007] For example, PLA or PLGA microparticles are prepared by rapidly solidifying PLA or PLGA in a solution of a polymer in an organic solvent in the presence of a co-dissolved or particulate drug. The microparticles include polymers in the form of physical aggregations of polymer chains, and the polymers typically have acid or ester end groups. However, after removing residual solvents, the microparticles typically prepared from biodegradable polymers, copolymers, or polymer blends (e.g., PLGA microparticles) precipitated from the solution will typically become glassy materials. This characteristic makes drug release in vivo difficult to control.

[0008] The glass transition temperature (Tg) is a unique property of polymers that depends on composition and molecular weight. Furthermore, after implantation, the Tg decreases with degradation and increased moisture content. It has been observed that with these materials, the Tg often drops below body temperature, leading to plasticization of the microparticles, thereby converting the glassy solid microparticles into viscous liquid droplets in vivo. This phase transition during biodegradation has been found to sometimes drastically alter the degradation kinetics and drug release rate in an uncontrolled manner, which is detrimental to the safe and reliable sustained release of the active agent.

[0009] In order to achieve the purpose of sustained release, in many cases, the zero-order release rate of the preferred drug may be, that is, the constant release rate with only slight changes over time. However, the drug is discharged from non-crosslinked polymer PLA or PLGA microparticles and follows an S-shaped curve usually. This curve comprises a lag phase, a release phase and a decay phase, and usually a drug burst (burst) occurs immediately after implantation. The release rate and the stage of PLA or PLGA microparticles depend on the ratio of molecular weight, L and G, the end group (acid or ester) and environmental conditions on the polymer. Therefore, it is necessary to provide a microparticle for a continuous drug delivery system so as to better control the release of an active agent, and not be affected by the influence of its solubility in physiological fluids, and produce the reliable degradation kinetics of the polymeric material for encapsulating an active agent. It is also necessary to provide a microparticle for sustained release drug delivery, which has thermal stability and can be processed at high temperatures.

[0010] All references cited herein are incorporated by reference in their entirety for all purposes.

[0011] OBJECTIVES AND SUMMARY OF THE INVENTION

[0012] It is therefore an object of certain embodiments of the present invention to provide biodegradable microparticles for sustained release drug delivery that can provide a substantially constant zero-order release of an active agent over time.

[0013] It is another object of certain embodiments of the present invention to provide biodegradable microparticles for sustained release drug delivery that show little burst release of the active agent.

[0014] Yet another object of certain embodiments of the present invention is to provide biodegradable microparticles for sustained release drug delivery that are thermally stable and can be processed at elevated temperatures, such as in a hot melt extrusion process.

[0015] It is an object and an aspect of certain embodiments of the present invention to provide pharmaceutically acceptable biodegradable microparticles for sustained-release drug delivery of an active ingredient into a patient.

[0016] Another object and an aspect of certain embodiments of the present invention is to provide a method of making such biodegradable microparticles for sustained-release drug delivery of an active ingredient into a patient.

[0017] Another object and an aspect of certain embodiments of the present invention is to provide a biodegradable sustained-release drug delivery system comprising the biodegradable microparticles of the present invention for sustained-release drug delivery, particularly for use as drug-eluting implants or directly as medicaments.

[0018] It is another object and an aspect of certain embodiments of the present invention to provide a method for controlling the release of an active agent in a biodegradable sustained-release drug delivery system.

[0019] Another object and an aspect of certain embodiments of the present invention is to provide methods of treating a disease / medical condition in a patient using the biodegradable microparticles for sustained-release drug delivery of an active ingredient into the patient's body.

[0020] Another object and an aspect of certain embodiments of the present invention is to provide a method for controlling the release of an active agent in a biodegradable sustained-release drug delivery system comprising the biodegradable microparticles for sustained-release drug delivery of the present invention.

[0021] Some aspects of the present disclosure relate to biodegradable microparticles for sustained-release drug delivery, the biodegradable microparticles comprising at least one active agent and a three-dimensionally covalently cross-linked biodegradable polymer, wherein the cross-linked biodegradable polymer comprises at least one of the following: cross-linked polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), poly-p-dioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or a copolymer of any one thereof.

[0022] Some aspects of the present disclosure relate to biodegradable microparticles for sustained-release drug delivery, the biodegradable microparticles comprising at least one active agent and a three-dimensionally covalently cross-linked biodegradable polymer, wherein the biodegradable microparticles include an organogel comprising at least one cross-linked polymer and an oil.

[0023] In some aspects of the present disclosure, the microparticles are microspheres having a substantially spherical shape.

[0024] In some aspects of the present disclosure, the active agent is dispersed, embedded, or encapsulated in an organogel or a polymer matrix that forms an organogel. The organogel is formed by chemically crosslinking at least one multifunctional precursor, optionally in the presence of an oil, to form a three-dimensional covalently crosslinked biodegradable polymer matrix. In some aspects, the at least one multifunctional precursor has a chemical crosslinking functionality greater than 2, greater than 4, greater than 8, or 2 to 16, 2 to 10, or 2 to 8. In some aspects, the at least one multifunctional precursor is a dendrimer or multi-arm precursor having a core and 2 to 10 arms, or 3 to 10 arms, 4 to 8 arms, or 4 or 6 arms, each arm comprising a polymer unit and having a terminal end. The functional group for chemical crosslinking can be bonded to each terminal end.

[0025] In some aspects of the present disclosure, the covalently cross-linked biodegradable polymer in the microparticles comprises one or more of the following polymer units: polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or copolymers, random or block copolymers thereof, or combinations or mixtures thereof; or one or more of the following units: polyamino acids, glycosaminoglycans, polysaccharides or proteins, or combinations or mixtures thereof. The three-dimensional covalently cross-linked biodegradable polymer matrix may comprise a plurality of hydrophobic polymer units and / or hydrophilic polymer units.

[0026] In some aspects of the present disclosure, the three-dimensional covalently cross-linked biodegradable polymer comprises a plurality of hydrophobic polymer units, such as polylactic acid (PLA) or polylactic-co-glycolic acid (PLGA) units; and / or a plurality of hydrophilic polymer units, such as polyethylene glycol units, polypropylene glycol units or polyglycolic acid (PGA). In certain embodiments, the hydrophobic polymer units comprise polyethylene glycol units. In certain embodiments, the hydrophobic polymer units comprise polylactic acid (PLA) units.

[0027] In one embodiment of the present disclosure, the biodegradable polymer matrix of three-dimensional covalent crosslinking comprises poly(lactic acid)-co-glycolic acid (PLGA) unit or is made up of PLGA unit.Poly(lactic acid)-co-glycolic acid (PLGA) unit can have about 0:100 to about 100:0, or about 1:99 to about 99:1, or about 10:90 to about 90:10, or about 25:75 to about 75:25 range of L / G ratio (representing with L or G unit %).In certain embodiments, L / G ratio is 50:50.In one aspect, described polymeric unit each has about 1,000 to about 100,000 dalton, or about 10,000 to about 60,000 dalton, or about 15,000 to about 50,000 dalton range of mean molecular weight (Mw).

[0028] In some aspects of the present disclosure, the polymer matrix is ​​covalently cross-linked by intramolecular or intermolecular hydrolyzable bonds between polymer units, or a combination of the two. To form the organogel polymer matrix, a multifunctional precursor can be cross-linked using at least one cross-linking agent having at least two functional groups or more than two functional groups, such as a small amine such as tris(2-aminoethyl)amine (TAEA) or trilysine. Alternatively or in addition, the organogel comprises or is formed from at least two cross-linkable dendrimers or multi-arm precursors that are intramolecularly cross-linked to each other. The dendrimers or multi-arm precursors comprise functional groups on at least three of their arm ends or on each end.

[0029] In some aspects of the present disclosure, the polymer matrix is ​​formed by at least two multi-arm precursors (e.g., 2 to 10 arm precursors), the multi-arm precursors comprising a first multi-arm precursor comprising a first functional group and a second multi-arm precursor comprising a second functional group, the functional groups being located at the ends of each arm of the precursor or cross-linker, wherein the first functional group or the second functional group can be directly grafted to the precursor end, or grafted to the precursor end through a linker molecule. In certain embodiments, the first functional group and the second functional group are each selected from an electrophile and a nucleophile; a functional group for click chemistry; a functional group for a cycloaddition reaction, such as a 1,3 dipolar cycloaddition reaction, a hetero-Diels-Alder cycloaddition reaction; a functional group for nucleophilic ring opening; a functional group for a non-aldol type carbonyl reaction; a functional group for an addition reaction with a carbon-carbon multiple bond; a polymerizable vinyl group, or a combination thereof.

[0030] In one aspect of the present disclosure, the first functional group and the second functional group are each selected from the group consisting of electrophilic reagent and nucleophilic reagent, and the reaction between the first functional group and the second functional group is the electrophilic reagent-nucleophilic reagent reaction forming a covalent bond, such as polycondensation reaction.Nucleophilic reagent can be selected from one of amine (such as primary amine), hydroxyl, alcohol, thiol, azide anion and carboxyl.Electrophilic reagent can be selected from active ester groups, such as succinimidyl ester, succinimidyl carbonate, nitrophenyl carbonate, aldehyde, ketone, acrylate, acrylamide, maleimide, vinyl sulfone, iodoacetamide, alkene, alkynes, azide, norbornene, epoxide, mesylate, toluenesulfonate, trifluoroethanesulfonyl (tresyls), cyanurate, adjacent pyridyl disulfide or halogen.

[0031] In one embodiment and one aspect of the present disclosure, the nucleophile is an amine group, such as a primary amine, and the electrophile is an active ester group, such as a succinimidyl ester selected from succinimidyl succinate, succinimidyl glutarate, succinimidyl adipate, succinimidyl azelate, or succinimidyl glutaramide.

[0032] In some other aspects of the present disclosure, the first functional group and the second functional group are each selected from functional groups for click chemistry, including functional groups for cycloaddition reactions, such as 1,3 dipolar cycloaddition reactions, [3+2] cycloaddition reactions (such as alkene-nitrone cycloaddition reactions or alkyne-nitrone cycloaddition reactions), [4+2] cycloaddition reactions, hetero Diels-Alder cycloaddition reactions; functional groups for thiol-ene reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol type carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; and functional groups for Michael-type addition reactions.

[0033] In these aspects of the present disclosure, the first functional group is an alkyne compound, such as dibenzocyclooctyne (DBCO) or bicyclo[6.1.0]-nonyne (BCN); or norbornene or trans-cyclooctene (TCO), and the second functional group is azide, 3,4-dihydroxyphenylacetic acid (DHPA) or tetrazine (Tz). DBCO, BCN, norbornene, TCO, azide, DHPA and Tz functional groups can be grafted to the end of the multi-arm precursor through a linker, such as an acid group, a diacid group, a functionalized aliphatic group, a heteroaliphatic group, or an aromatic group or a heteroaromatic group.

[0034] In another aspect of the present disclosure, the first functional group and the second functional group are selected for a [3+2] cycloaddition reaction, such as an alkene-nitrone cycloaddition reaction or an alkyne-nitrone cycloaddition reaction.

[0035] In another aspect of the present disclosure, the first functional group and the second functional group are selected for a [4+2] cycloaddition reaction, particularly a hetero-Dickens-Alder reaction, wherein the first functional group is an aldehyde or an imine compound and the second functional group is a 1,3 diene compound, an unsaturated carbonyl compound, or a nitroso-olefin compound.

[0036] In another aspect of the present disclosure, the first functional group and the second functional group are selected for a thiol-ene reaction, wherein the first functional group is a thiol compound and the second functional group is an olefin, such as a terminal olefin.

[0037] In other aspects of the disclosure, the first functional group and the second functional group are selected for nucleophilic ring opening, wherein the first functional group is selected from an epoxide, a thiirane, an aziridine, or a lactam, and the second functional group is a nucleophile.

[0038] In one aspect of the present disclosure, the first functional group and the second functional group are selected for a non-aldol type carbonyl reaction, wherein the first functional group is an aldehyde or ketone compound and the second functional group is a primary amine, hydrazine, hydrazide, or aminooxy compound for forming an imine, amide, isourea, hydrazone, acylhydrazone, or oxime linkage.

[0039] In another aspect of the present disclosure, the first functional group and the second functional group are each selected from polymerizable vinyl groups and acrylates, such as (meth)acrylic acid, (meth)acrylates, acrylamide, fumaric acid, maleic acid, and combinations thereof.

[0040] In certain aspects of the present disclosure, crosslinking is induced thermally or photochemically using electromagnetic radiation, optionally with the use of an initiator, for example a photoinitiator, such as a free radical photoinitiator (Norish I type, for example 2,2-dimethoxy-1,2-diphenyl-ethan-1-one, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxy-cyclohexylphenyl ketone; or Norish II type, for example benzophenone and its derivatives and isopropylthioxanthone in combination with a synergist such as a tertiary amine, for example 2-ethylhexyl-(4-N,N-dimethylamino)benzoate and 2-ethyl-(4-N,N-dimethylamino)benzoate); or a cationic photoinitiator.

[0041] In one aspect of the present disclosure, the organogel forming the biodegradable microparticles comprises a polymer matrix, wherein the polymer is covalently cross-linked via linkages or bonds between polymer units. The linkages may be selected from amine, amide, carbamate, ester, anhydride, ether, acetal, ketal, nitrile, isonitrile, isothiocyanate, isourea, hydrazone, oxime, or imine bonds, and combinations thereof.

[0042] In some aspects of the present disclosure, the active agent is selected from at least one of the following: a therapeutic active agent or a diagnostic active agent, or a combination thereof. The therapeutic active agent can be selected from steroids; nonsteroidal anti-inflammatory drugs (NSAIDS), such as Diclofenac, Ibuprofen, Meclofenamate, Mefanamic A, Salsalate, Sulindac, Tolmetin, Ketoprofen, Diflunisal, Piroxicam, Naproxen, Etodolac, Flurbiprofen, Fenoprofen C, C), indomethacin, celecoxib, ketorolac, nepafenac; intraocular pressure lowering drugs; antibiotics, such as ciprofloxacin; analgesics, such as bupivacaine; calcium channel blockers, such as nifedipine; cell cycle inhibitors, such as simvastatin; proteins, such as insulin; small molecule hydrophilic drugs, including carboxylate and amine salts; small molecule hydrophobic drugs, hydrophilic peptides and protein drugs, such as insulin, single-chain antibody fragments, Fab fragments, IgG antibodies, fusion antibodies, etc.; aptamers; in particular bupivacaine (BPV-HCl or base), ropivacaine (RPV), dexamethasone, travoprost, axitinib, nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics, analgesics, calcium channel blockers, cell cycle inhibitors, chemotherapeutic agents, antiviral drugs, anesthetics, hormones, anticancer drugs, antitumor agents, viruses, viruses for gene delivery (such as AAV), etc., or any combination thereof.

[0043] In certain aspects of the present disclosure, the microparticles have a particle size (diameter) of about 0.1 μm to about 1000 μm, or about 1 μm to about 150 μm, about 1 μm to about 100 μm, about 20 μm to about 75 μm, about 10 μm to about 106 μm, or about 20 μm to about 55 μm, as determined by sieving, or have an average diameter in the range of about 0.1 μm to about 1000 μm, or about 1 μm to about 150 μm, about 1 μm to about 100 μm, about 20 μm to about 75 μm, about 10 μm to about 106 μm, or about 20 μm to about 55 μm, as determined by laser diffraction, and exhibit a substantially spherical shape. The microparticles may have a particle size distribution, for example, as determined by laser diffraction, with a D50 particle size of less than about 100 μm, or less than about 50 μm, or less than about 20 μm, and / or a D90 particle size of less than about 200 μm, or less than about 50 μm, or a D90 particle size of about 100 μm or less, or 30 μm or less, and / or a D90 particle size of about 20 μm or less. In certain embodiments, the lower limits of D50 and D90 are 1 μm, 5 μm, or 10 μm, and may be ranges having any of the above values.

[0044] In some aspects of the present disclosure, the biodegradable microparticles comprise or consist of a blend of microparticles having different particle sizes and / or having different polymer matrices and / or including different active agents.

[0045] In some aspects of the present disclosure, the choice of organogel precursor, and / or the hydrophobicity of the polymer units, and / or the L / G ratio of the PLGA units are used to tune the release rate. For example, the lipophilicity of the microparticles can be adjusted using combinations of different amounts of PEG and PLA or PLGA precursors.

[0046] In one aspect of the present disclosure, the biodegradable microparticles provide for release of an effective amount of the active agent over a period of time, for example, up to about 1 year, up to about 9 months, up to about 6 months, up to about 3 months, up to about 1 month, or up to about 25 days after administration, for example, up to about 14 days or up to about 21 days after administration, wherein optionally, the active agent release is substantially constant over a temperature range of about 30°C to about 45°C or about 36°C to about 43°C.

[0047] In some aspects of the present disclosure, the polymer matrix has a glass transition temperature below human body temperature, for example, below about 37°C, or below about 36°C, below about 30°C, below about 25°C, below about 20°C, or below about 10°C, and / or wherein the polymer matrix has a melting temperature greater than about 40°C, about 45°C, about 50°C, about 60°C, or about 70°C. In certain embodiments, the lower limit of the glass transition temperature is about 5°C, or about 10°C, or about 20°C, or about 30°C, and can be a range having any of the above values. In certain embodiments, the polymer matrix has a melting temperature of no more than about 50°C, or about 75°C, or about 100°C, or about 150°C, and can be a range having any of the above values.

[0048] Some aspects of the present disclosure relate to a method for making the biodegradable microparticles disclosed herein for sustained-release drug delivery, the method being selected from, for example, one of the following methods: emulsion solvent evaporation-extraction, emulsion solvent diffusion, supercritical fluid emulsification, coacervation, spray drying, hydrogel templates, microfluidic systems, membrane extrusion emulsification, particle replication in non-wetting templates (PRINT) technology, electrohydrodynamic atomization (EHDA) or electrospraying, or particles obtained from gas saturated solutions (PGSS) method, or using 3D printing.

[0049] Some aspects of the present disclosure relate to a method of making the biodegradable microparticles described herein for sustained-release drug delivery, the method comprising the steps of: (1) forming a gel comprising a covalently cross-linked polymer in the presence of at least one active agent, optionally at least one oil, and optionally a first solvent; (2) making microparticles wherein the at least one active agent is dispersed within the covalently cross-linked polymer; and (3) optionally, removing the solvent.

[0050] In some aspects of the present disclosure, the above method includes the following steps: (a) dissolving at least one polymer precursor in a first solvent to produce a first mixture; (b) providing a second mixture, the second mixture comprising a crosslinker in a second solvent; (c) adding at least one active agent and optionally an oil to at least one of the first mixture or the second mixture; (d) combining the first mixture and the second mixture to produce a first phase; (e) providing a second phase comprising a third solvent that is immiscible with the first solvent and the second solvent; (f) introducing the first phase into the second phase under agitation, thereby producing an emulsion in which the first phase is dispersed in the second phase; and (g) removing the first solvent, the second solvent, and / or the third solvent. These steps can be performed in any order.

[0051] The step of making microparticles (step (2)) or step (f) comprises forcing the first phase through a screen, or injecting the first phase into the agitated second phase, wherein the first solvent and / or the second solvent and / or the third solvent optionally contain additives such as emulsifiers, surfactants, dispersing aids or porogens, so as to form microspheres or nanosphere particles.

[0052] In some aspects of the methods of the present disclosure, the first solvent or the second solvent is selected from acetone, acetonitrile, benzyl alcohol, chloroform, dichloromethane (DCM), dioxane, dimethyl carbonate, DMSO, ethanol, ethyl acetate, ethyl formate, ethyl propionate, tetraethylene glycol ether, hexafluoroisopropanol, dimethyl isosorbide, isopropanol, chloromethane, dichloromethane, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate or tetrahydrofuran, or any mixture thereof, and the third solvent is water, an alcohol (e.g., methanol, ethanol or propanol) or any mixture thereof.

[0053] In some aspects of the methods of the present disclosure, additives may be used, such as additives selected from the group consisting of surfactants or emulsifiers, such as polyvinyl alcohol (PVA), polyethylene glycol sorbitan monolaurate (Tween®), sorbitan monolaurate (Span®), sodium dodecyl sulfate (SDS); and / or porogens, such as inorganic salts (NaCl, KCl, sodium or potassium carbonates or bicarbonates, ammonium bicarbonate), Pluronics; sodium or potassium oleate; gelatin; mustard oil, mineral oil; cyclodextrins; carbohydrates, bovine serum albumin (BSA); photoinitiators, free radical polymerization initiators, and combinations thereof.

[0054] In some aspects of the methods of the present disclosure, steps (1) and (2) utilize water-in-oil emulsion or oil-in-water emulsion technology, or a combination thereof, such as single or double emulsion technology, or microfluidics technology, or a combination thereof.

[0055] In some aspects of the methods of the present disclosure, removal of the first solvent and / or the second solvent and / or the third solvent is performed by one of hot air convection or direct drying, indirect or contact drying, spray drying, dielectric drying, vacuum drying, freeze drying, supercritical or superheated steam drying, or any combination of these methods.

[0056] Some aspects of the present disclosure relate to a biodegradable sustained-release drug delivery system comprising the biodegradable microparticles disclosed herein for sustained-release drug delivery. In some aspects, the biodegradable microparticles are incorporated into a hydrogel, xerogel, or organogel, optionally by extrusion or injection molding of a reaction mixture comprising the biodegradable microparticles of the present disclosure dispersed in a hydrogel, xerogel, or organogel, or a precursor thereof, for in situ implant formation. In some aspects thereof, gelation occurs before and / or during extrusion or injection molding of a gel-forming material comprising the biodegradable microparticles.

[0057] In other aspects, the biodegradable sustained release drug delivery system of the present disclosure is used to coat or serve as a medical implant. The implant can be selected from an intraocular implant, an intracavitary implant, an intracameral implant, an implant for introduction into the anterior chamber, vitreous, extrascleral, posterior subtenon's space (inferior fornix), subconjunctival, intracameral, periorbital, retrobulbar, subfascial, retinal, subretinal, intratubular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of cornea or conjunctiva, lacrimal puncta (tubules, upper / lower tubules), fornix, upper / lower fornix, subfascial space, choroid, suprachoroidal, Tenon's fascia, cornea, cancer tissue, organ, prostate, breast, joint space, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically generated space or injury, void space, and potential space.

[0058] Some aspects of the present disclosure relate to a biodegradable sustained-release drug delivery system comprising the biodegradable microparticles disclosed herein or produced by the methods disclosed herein, for use as a medicament.

[0059] In some aspects, the present invention relates to a biodegradable sustained-release drug delivery system comprising the biodegradable microparticles disclosed herein or produced by the methods disclosed herein for use in treating a disease / medical condition in a patient, wherein the use comprises incorporating the biodegradable microparticles disclosed herein into a carrier such as a hydrogel, organogel or xerogel, wherein the hydrogel, organogel or xerogel is formed in situ at the treatment site of the patient, or is pre-made and delivered or implanted at the treatment site of the patient so as to release the active agent from the microparticles over an extended period of time, or the carrier is a solvent or solvent system to produce an injectable suspension or dispersion.

[0060] Some aspects of the present disclosure relate to biodegradable sustained-release drug delivery systems comprising biodegradable microparticles disclosed herein or produced by the methods disclosed herein; methods for treating a disease / medical condition in a patient, the methods comprising incorporating the biodegradable microparticles according to the present disclosure into a hydrogel, organogel, or xerogel, wherein the hydrogel, organogel, or xerogel is formed in situ at the treatment site of the patient, or is pre-manufactured and delivered or implanted at the treatment site, so as to release the active agent over an extended period of time.

[0061] Some aspects of the present disclosure relate to a method for treating a disease / medical condition in a patient, the method comprising administering to the patient a hydrogel, organogel, or xerogel comprising biodegradable microparticles according to the present disclosure to release the active agent over an extended period of time.

[0062] In some aspects of the invention, the treatment site is selected from the group consisting of the anterior chamber, vitreous, episcleral, posterior subfascial space (inferior fornix), subconjunctival, intracameral, periorbital, retrobulbar, subfascial, retinal, subretinal, intracanalicular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of the cornea or conjunctiva, puncta (canaliculi, superior / inferior canaliculi), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, Tenon's fascia, cornea, cancer tissue, organ, prostate, breast, joint, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or lesion, void space, and potential space.

[0063] In some aspects, the disease / medical condition to be treated is an eye disease, particularly a posterior eye disease, such as any posterior segment disease that affects the vasculature and integrity of the retina, macula, or choroid, leading to visual acuity impairment, vision loss, or blindness, particularly posterior segment disease states caused by age, trauma, surgical intervention, such as age-related macular degeneration (AMD), cystoid macular edema (CME), diabetic macular edema (DME), posterior uveitis, and diabetic retinopathy; or glaucoma, intraocular hypertension, hyphema, presbyopia, cataracts, retinal vein occlusion, inflammation.

[0064] In some aspects, the present disclosure also relates to a method for controlling the release of an active agent in a biodegradable sustained-release drug delivery system disclosed herein or manufactured by the method disclosed herein, wherein the control of the release of the active agent comprises any one or a combination of the following measures: selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) unit to adjust the hydrophobicity of the polymer matrix forming the microparticles; selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) unit to provide sustained release of the active agent in the microparticles; selecting the molar ratio of the amount of the first cross-linkable precursor to the amount of the second cross-linkable precursor to adjust the hydrophobicity of the polymer matrix forming ... The invention relates to a method for preparing a microparticle comprising: preparing a microparticle comprising: preparing a microparticle comprising: a first cross-linkable precursor and a second cross-linkable precursor; selecting a molar ratio of the amount of the first cross-linkable precursor to the amount of the second cross-linkable precursor to provide sustained release of the active agent from the microparticle; selecting the amount and / or particle size of the biodegradable microparticles included in the hydrogel, organogel or xerogel; adding a third cross-linkable precursor that is less hydrolyzable than the first cross-linkable precursor and the second cross-linkable precursor when forming the biodegradable microparticles, and optionally changing the molar ratio of the first cross-linkable precursor, the second cross-linkable precursor and / or the third cross-linkable precursor; and dispersing the active agent having high water solubility in the form of particles in the organogel having the biodegradable microparticles.

[0065] definition

[0066] The term "biodegradable" refers to a material or object (e.g., a microparticle according to the present invention) that degrades in vivo (i.e., when placed in a human or animal body) or in vitro when immersed in an aqueous solution under physiological conditions, such as pH 7.2-7.4 and 37°C. In the context of the present invention, as disclosed in detail below, after the microparticles containing the active agent are administered or deposited in the human or animal body, the microparticles slowly biodegrade over time. In certain embodiments, biodegradation occurs at least in part by ester hydrolysis in the aqueous environment of the body. Biodegradation can occur by covalent crosslinking and / or hydrolysis or enzymatic cleavage within the polymer units. The microparticles slowly soften and disintegrate, thereby being cleared through physiological pathways. In certain embodiments, the microparticles of the present invention retain their shape for an extended period of time (e.g., about 1 month, 3 months, or 6 months). In certain embodiments, the shape is maintained due to covalent crosslinking of the polymer components that form the microparticles, for example, until the active agent, or at least a substantial amount thereof (e.g., at least 50%, at least 75%, or at least 90%), is released from the microparticles.

[0067] In an embodiment of the present invention, the microparticles comprise an organogel. An "organogel" in the present invention is a solid or semi-solid system that forms a covalently cross-linked three-dimensional network of one or more hydrophilic or hydrophobic natural or synthetic polymers (as disclosed herein), wherein the one or more hydrophilic or hydrophobic natural or synthetic polymers include oils or generally include hydrophobic organic liquids disclosed herein. Thus, in the present invention, "organogel" is limited to so-called chemical organogels, in which the intermolecular interactions between the molecules of the organogelator are chemical linkages (e.g., covalent bonds) formed during gelation by chemical reactions that induce cross-linking. As used herein, "organogel" refers to a three-dimensional polymer network or matrix of at least two precursors / gelators / precursors that are covalently cross-linked to each other in the presence of an oil and, optionally, an organic solvent, and comprises an oil contained within the covalently cross-linked polymers that form the microparticles.

[0068] A "hydrogel" is a three-dimensional network of one or more hydrophilic natural or synthetic polymers (as disclosed herein) that can swell in water and retain a certain amount of water while maintaining or substantially maintaining its structure, for example due to chemical or physical crosslinking of individual polymer chains. Due to their high water content, hydrogels are soft and elastic, which makes them very similar to natural tissue. In the present invention, the term "hydrogel" is used to refer to a hydrogel in a hydrated state when it contains water (e.g., after the hydrogel is formed in an aqueous solution, or after hydration or (re)hydration after the hydrogel is inserted into the body or otherwise immersed in an aqueous environment), and to a hydrogel in a dry (dried / dehydrated) state, for example, when dried to a low water content, e.g., not more than 1% by weight, or when the formulation produces a low water content insert without the need for a drying step.

[0069] The terms "polymer," "polymer network," or "polymer matrix," as used in the context of the microparticles of the present invention, describe a structure formed by polymer chains (having the same or different molecular structures and the same or different molecular weights) that are covalently cross-linked to one another. Types of polymers suitable for the purposes of the present invention are disclosed below. The term "polymer network" is used interchangeably with the term "matrix."

[0070] The term "amorphous" refers to a polymer or polymer network that does not exhibit a melting point or a crystalline structure in X-ray or electron scattering experiments.

[0071] The term "semicrystalline" refers to a polymer or polymer network that has some crystalline character (ie, exhibits a melting point or some crystalline properties in X-ray or electron scattering experiments).

[0072] The term "precursor" or "gelling agent" or "component" refers herein to those molecules or compounds that react with each other and thereby link via covalent crosslinks to form a polymer network and, optionally in the presence of an oil, an organogel matrix.

[0073] The portion of the precursor molecule that is still present in the final polymer is also referred to herein as a "unit." Thus, a "unit" is a component or constituent of the polymer network that forms the microparticle. For example, a polymer network suitable for use in the present invention may contain the same or different PLGA units, polyethylene glycol units, or other types of polymers as further disclosed herein.

[0074] As used herein, the term "release" (and hence the terms "released," "releasing," etc.) refers to the provision of an active agent from a microparticle or drug delivery system (such as an implant comprising the microparticles of the invention) to the surrounding environment. The surrounding environment can be an in vitro or in vivo environment as described herein. In certain specific embodiments, the surrounding environment is the vitreous humor and / or ocular tissues, such as the retina and choroid.

[0075] The term "100% release of the active agent" should be interpreted as 95% to 100%. This controlled release is achieved through a number of parameters that are characteristic of the drug delivery systems disclosed herein. Each of these unique features of the drug delivery system can be responsible for controlled release, alone or in combination with one another.

[0076] For the purposes of the present invention, the term "sustained release" is intended to characterize products such as biodegradable microparticles, which are formulated so that the active agent is available over an extended period of time, thereby reducing the frequency of administration compared to immediate release dosage forms (such as active agent solutions applied topically to the eye, i.e., eye drops). Other terms that can be used interchangeably with "sustained release" in this article are "extended release" or "controlled release." Within the meaning of the present invention, the term "sustained release" includes constant active agent release, gradually decreasing active agent release, gradually increasing active agent release, and any combination thereof, such as constant active agent release followed by gradually decreasing active agent release. Within the meaning of the present invention, the term "tapered" or "tapering" refers to that the release of an active agent decreases over time. Specifically, the term "sustained release" refers to that the active agent is released in a predetermined manner from a microparticle or a drug delivery system comprising microparticles, and is in sharp contrast to immediate release such as bolus injection. In certain embodiments, controlled release refers to the amount of active agent released over the total number of days required for 100% release of the active agent in aqueous solution under in vitro physiological conditions, such as at pH 7.2-7.4 and 37°C.

[0077] As used herein, the term "extended period of time" refers to any period of time that one of ordinary skill in the art would recognize as prolonged in treating a disease, and specifically, refers to a period of time such as at least about 1 week, or at least about 1 month or longer, such as up to about 12 months, or any intermediate period of time, such as about 1 to about 6 months, about 2 to about 4 months, about 2 to about 3 months, or about 3 to about 4 months, or as otherwise disclosed herein.

[0078] "Zero order" release or "substantially zero order" release or "near zero order" release is defined as a relatively straight line in a graphical representation of the percentage of active agent released versus time. In certain embodiments of the invention, substantially zero order release is defined as the amount of active agent released being proportional to the elapsed time within 20%.

[0079] The terms "API," "active (pharmaceutical) ingredient," "active (pharmaceutical) agent," "active (pharmaceutical) principle," "(active) therapeutic agent," "active substance," and "drug" are used interchangeably herein and refer to substances used in a final pharmaceutical product (FPP) and substances used in the preparation of such final pharmaceutical products, which are intended to provide pharmacological activity or otherwise have a direct effect in the diagnosis, cure, mitigation, treatment or prevention of disease, or in restoring, correcting or regulating a patient's physiological function.

[0080] The activating agent used according to the present invention can be an activating agent for treating and / or preventing disease or illness, or a diagnostic agent, such as a marker. In one embodiment of the invention, the activating agent is a low water-soluble activating agent (that is, a solubility in water is less than about 1000 μg / mL or less than about 100 μg / mL). In other embodiments of the present invention, the activating agent is a highly water-soluble activating agent (that is, a solubility in water is greater than about 1000 μg / mL or even greater than 10 mg / mL). This definition is unrelated to the agent approved by a government agency.

[0081] For the purposes of the present invention, an activating agent in all possible forms can be used, including free acid, free base, polymorph or any pharmaceutically acceptable salt, anhydrous substance, hydrate, co-crystal, or other solvate or derivative, such as prodrug or conjugate. Whenever an activating agent is mentioned in this specification or in the claims, and no further explanation is given, even if it is not explicitly stated, it also refers to an activating agent in the form of any such polymorph, pharmaceutically acceptable salt, anhydrous substance or solvate (including hydrate) (we will discuss this deleted part). With regard to activating agent, suitable solid forms include but are not limited to the pure substance form in any physical form known to those of ordinary skill in the art. For example, the activating agent can be in the form of particles. The particles can be amorphous or crystalline, or present a mixture of two forms, and can be prepared to have any size, which can be, but is not limited to, classified as coarse particles, fine particles or ultrafine particles, the size of which can be particularly visible to the naked eye or visible under a microscope, and has a shape such as a single crystal grain and / or agglomerate. The particles can also be micronized. As used herein, the term "micronized" refers to small-sized particles, particularly those of the microscopic scale, which are reduced in size without restriction by, for example, jet milling, jaw crushing, hammer milling, wet milling, precipitation in a non-solvent, cryogenic grinding (grinding with liquid nitrogen or dry ice), and ball milling. The active agent may also be present in a dissolved or dispersed state, for example, in a solvent or in an aqueous medium, for example, in the form of particles dispersed in an oil or a compatible aqueous suspension that may optionally include additional excipients such as surfactants.

[0082] As used herein, the term "therapeutically effective" refers to the amount of active agent required to produce the desired therapeutic outcome following administration. For example, in the context of the present invention, a desired therapeutic outcome would be a reduction in symptoms associated with DED, as measured by in vivo tests known to those of ordinary skill in the art, such as an increase in the Schirmer's tear test score; a decrease in conjunctival lissamine green staining or corneal fluorescein staining; a decrease in dry eye severity and / or dry eye frequency scores on a visual analog scale (VAS); a decrease in the Ocular Surface Disease Index and / or Standard Patient Dry Eye Assessment scores; and a decrease in best-corrected visual acuity. In one embodiment, "therapeutically effective" means that the amount of active agent in the sustained-release tubing insert is capable of achieving a tear concentration over an extended period of time, and in particular, for substantially the entire remaining wear period of the insert after achieving a tear concentration that is comparable in therapeutic effect to a cyclosporine concentration of 0.236 μg / mL (a concentration believed to be necessary for immunomodulation; Tang-Liu and Acheampong, Clin. Pharmacokinet. 44(3), pp. 247-261).

[0083] As used herein, the values ​​"d10", "d50", "d90" and "d100" refer to values ​​that characterize the proportion of particles in a particle size distribution that meet a certain particle size. In a given particle size distribution, 10% of the particles exhibit a particle size of d10 or less, 50% of the particles exhibit a particle size of d50 or less, 90% of the particles exhibit a particle size of d90 or less, and substantially all of the particles exhibit a particle size of d100 or less. The percentages can be given by different parameters known to those of ordinary skill in the art, for example, the percentages can be based on the volume, weight or number of particles. Thus, d50 can be illustratively a median particle size based on volume, weight or number. For example, a volume-based d90 of 43 μm means that 90% of the particles by volume have a particle size of 43 μm or less. In certain embodiments, d10, d50 and d90 are volume-based values. Particle size distribution PSD can generally be measured by methods known to those of ordinary skill in the art, and include sieving methods as well as laser diffraction methods. In certain embodiments, PSD is measured according to USP <429> Light Diffraction Measurement of Particle Size is measured by laser diffraction. In certain embodiments, PSD is measured by laser diffraction using a Beckman Coulter LS 13320 based on the optical model "Fraunhofer.rf780z" with an obscuration value in the range of 7% to 9%.

[0084] The term "patient" herein includes both human and animal patients. Therefore, the biodegradable drug delivery system according to the present invention is suitable for human or veterinary applications. In general, a "subject" is a (human or animal) individual to whom the drug delivery system according to the present invention is administered. A "patient" is a subject who needs treatment due to a specific physiological or pathological condition. A "patient" does not necessarily have a diagnosis of a specific physiological or pathological condition before receiving the drug delivery system.

[0085] The molecular weight of the polymer precursors used for the purposes of the present invention and as disclosed herein can be determined by analytical methods known in the art. The molecular weight of the polyethylene glycol can be determined, for example, by any method known in the art, including gel electrophoresis, such as SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis); Gel permeation chromatography (GPC), including GPC with a static light scattering detector (SLS) or dynamic light scattering (DLS); Liquid chromatography (LC) and mass spectrometry, such as matrix-assisted laser desorption / ionization time of flight (MALDI-TOF) spectroscopy or electrospray ionization (ESI) mass spectrometry. The molecular weight of the polymers, including the polyethylene glycol precursors disclosed herein, is an average molecular weight (based on the molecular weight distribution of the polymer) and can therefore be expressed by means of various average values, including weight average molecular weight (Mw) and number average molecular weight (Mn). In the case of the cross-linkable polymer gelling agent used in the present invention, such as polyethylene glycol, PLGA and based on the precursor of poloxamer, the molecular weight indicated herein is according to standard method known in the art, uses polystyrene standards to pass through the number average molecular weight (Mn) determined by gel permeation chromatography.Usually, the material purchased, especially the multi-arm precursor has the specific molecular weight limited by the supplier.For example, the PEG precursor that is applicable can be obtained from many suppliers such as Jenkem Technology.

[0086] As used herein, the term "Day 1" refers to the time point immediately following "Day 0." Thus, whenever "Day 1" is used, it refers to a period of time in which one day or about 24 hours has passed after administration of the drug delivery system.

[0087] As used herein, the term "about" in relation to a measured quantity refers to the normal variation in that measured quantity that one of ordinary skill in the art would expect when making the measurements and exercising a degree of care commensurate with the purpose and the precision of the measuring device.

[0088] The term "at least about" with respect to a measured quantity refers to the normal variation in the measured quantity that one of ordinary skill in the art would expect when making the measurements and exercising a degree of care commensurate with the purpose and the precision of the measuring equipment, as well as any amount above the measured quantity.

[0089] As used herein, the term "average" refers to the central value or typical value in a group of data (points), which is calculated by dividing the sum of the individual data (points) in the group by their number (i.e., the average of a group of data).

[0090] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0091] The term "and / or" used herein in phrases such as "A and / or B" is intended to include both "A and B" and "A or B."

[0092] Open-ended terms such as “include,” “including,” “contain,” “containing,” etc. mean “comprising.” These open transition phrases are used to introduce an open list of elements, method steps, etc., and do not exclude additional, unrecited elements or method steps.

[0093] When the term "up to" is used herein with a certain value or number, it is intended to include the corresponding value or number.

[0094] The terms "from A to B," "of from A to B," and "of A to B" are used interchangeably herein and all refer to a range from A to B, including the upper and lower limits A and B.

[0095] Throughout this disclosure, various aspects of the present invention are presented in the form of ranges. It should be understood that the description in the form of ranges is merely for convenience and brevity, and should not be construed as an unchangeable limitation on the scope of the present invention. Therefore, the description of a range should be considered to have clearly disclosed all possible subranges and the individual numerical values ​​within the range. For example, a range description such as 1 to 6 should be considered to have clearly disclosed subranges, such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., and the individual numerals within the range, such as 1, 2, 3, 4, 5 and 6. Regardless of the breadth of the scope, this applies. The numerical ranges listed include the numerals that limit the range and include each integer within the limited range.

[0096] The abbreviation "PBS" when used herein means phosphate buffered saline.

[0097] The abbreviation "PEG" when used herein means polyethylene glycol.

[0098] The abbreviation "PLGA" when used herein means poly(lactic-co-glycolic acid). If not otherwise indicated, it has an L / G ratio of 1:1 (50:50).

[0099] The term "hydrophobicity" or "lipophilicity" is defined as the property of a polymer or material to have a low degree of water attraction or absorption, i.e., the material is repelled by large amounts of water. Conversely, the term "hydrophilicity" or "lipophobicity" is defined as the property of a material or polymer to attract or have a strong affinity for water. Hydrophobicity can be measured by determining the contact angle of a liquid droplet (preferably water droplet) formed on the surface of a solid polymer and / or gel. In addition, the hydrophobic organic liquid used in the present invention is immiscible or at least poorly miscible with water.

[0100] A "hydrophilic" molecule, eg, a precursor or a portion of a precursor, has a solubility in aqueous solution of at least 1 g / 100 mL.

[0101] As used herein, the term "immobilized" refers to long-range immobility, rather than local mobility within the microparticle polymer matrix, i.e., the oil is present as a continuous phase within the polymer matrix and may only be slowly mobile in vivo, i.e., it may slowly escape into body fluids over time. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Figure 1 An example of optimizing drug release by using a blend of different prior art non-crosslinked polymer microparticles relative to the release characteristics of individual prior art non-crosslinked microparticles made from different types of PLA polymers is shown.

[0103] Figure 2 An image of the Fibrijet® Y-mixer used.

[0104] Figure 3 is a SEM image of cross-linked PLGA microparticles without active agent after heating at 80°C for 2 hours.

[0105] Figure 4 1 and 2 are SEM images of microparticles with a diameter of >106 μm according to an embodiment of the present invention before and after heating at 80° C. for 2 hours.

[0106] Figure 5 1 and 2 are SEM images of microparticles with a diameter between 20 and 106 μm according to an embodiment of the present invention before and after heating at 80° C. for 2 hours.

[0107] Figure 6 Microscope images of microparticles according to an embodiment of the present invention (left) and comparative non-crosslinked PLA microparticles (right) after heat treatment at 80° C. for 2 hours are shown.

[0108] Figure 7 The effects of microparticle diameter and heat treatment on the in vitro release of travoprost are shown.

[0109] Figure 8 Graph comparing the in vitro release of travoprost from cross-linked PLGA microparticles and prior art non-cross-linked PLA microparticles.

[0110] Figure 9 is a graph comparing the in vitro release of travoprost from non-cross-linked PLA microparticles at different temperatures. DETAILED DESCRIPTION

[0111] The present invention relates to pharmaceutically acceptable biodegradable microparticles for sustained-release drug delivery of an active ingredient to a patient. In another aspect, a method for producing such biodegradable microparticles for sustained-release drug delivery of an active ingredient to a patient is provided. In certain aspects, the biodegradable microparticles can be incorporated into a biodegradable sustained-release drug delivery system, particularly as a drug-eluting implant, or the microparticles can be used directly as a medicament, such as an injectable solution containing the biodegradable drug-eluting microparticles in a suspended form.

[0112] In one embodiment, the biodegradable microparticles for sustained-release drug delivery comprise at least one active agent, such as a drug, and a three-dimensional covalently cross-linked biodegradable polymer. The active agent can be, for example, dispersed, embedded, or encapsulated in the covalently cross-linked biodegradable polymer.

[0113] particle

[0114] In certain embodiments, the biodegradable microparticles are formed by covalently crosslinking multifunctional monomers, oligomers, or polymer precursor molecules (disclosed herein below) through the formation of chemical bonds or linkages. The resulting three-dimensional covalently crosslinked polymer network can include the active agent (and other optional ingredients) and immobilize it within the polymer network of the microparticle, for example, until it is released from the microparticle in vivo or in vitro. A solvent or a hydrophobic organic liquid, such as an oil, can also be present in the microparticles, thereby forming organogel microparticles.

[0115] In certain embodiments, the covalent crosslinking of the polymer forming the precursor provides limited mobility for the active agent dispersed or encapsulated therein. This provides continuous control of drug release by limiting drug transport primarily to diffusion through the polymer matrix of the microparticles, thereby being largely independent of the degradation rate of the polymer itself. In addition, defects in the polymer, such as those caused by plasticization, will not develop in such crosslinked polymer microparticles, which would provide a path for the drug to quickly escape. In certain embodiments, the biodegradable microparticles of the present invention are completely or at least partially diffusion-controlled delivery systems, that is, the release of the active agent in the microparticles is primarily controlled by a diffusion process. In certain embodiments, in vivo degradation of the polymer also occurs in the microparticles of the present invention, but does not primarily control the release of the active agent. In non-crosslinked microparticles produced by solvent precipitation of linear polymers, the release of the active agent is primarily controlled by degradation of the polymer matrix, which primarily releases the active agent in a degradation-controlled system.

[0116] In certain embodiments, the use of covalently cross-linked polymers in the biodegradable microparticles for drug delivery of the present invention allows for the modification of the release of the active agent from the microparticles or drug delivery system by tailoring or appropriately selecting the precursor components that form the cross-linked polymer based on their hydrophilic and / or hydrophobic properties.

[0117] In addition, in certain embodiments, the release of the active agent from the microparticles or drug delivery system can be modified or controlled by appropriately selecting the type and amount of additives such as oil (hydrophobic organic liquid), for example, based on hydrophobicity, viscosity, compatibility with the active agent, solubility or insolubility of the active agent in the oil, etc.

[0118] In the embodiment of using oil in biodegradable microparticles, cross-linked polymers are formed into an organogel that comprises oil in a cross-linked polymer matrix. Oil can comprise the activating agent in dissolved or undissolved form and can be used to change the release of the activating agent or eliminate the incompatibility of the activating agent with the polymer. In other such embodiments, the activating agent itself can be oil, thus producing organogel as biodegradable microparticles. Hydrophobic organic liquids can also serve as pharmaceutical cosolvents in the microparticle manufacturing process.

[0119] The biodegradable microparticles of certain embodiments of the present invention offer various advantages over incorporating active agents directly into hydrogels. For example, the microparticles can be made of hydrophobic polymers and can be anhydrous, so that water-degradable (hydrolyzable) components, such as water-sensitive active agents, can be stabilized by encapsulation in the biodegradable microparticles and stored stably for extended periods of time without requiring hydration upon implantation.

[0120] Water-soluble compounds have low or no solubility in more hydrophobic polymers, allowing the incorporated drug to be embedded in the microparticles as a particulate solid for leaching through body fluids in vivo. Therefore, the low solubility of the drug in the microparticle polymer provides a reliable mechanism for controlling the drug release rate. This property greatly increases the range of compounds that can be included in the implant.

[0121] In addition, manipulation of the lipophilicity / hydrophilicity of the polymer in the microparticles can be used to adjust the release rate of the drug and affect the diffusion rate. Simple hydrogels cannot be adjusted in this way because they are water-based, so in these systems, the drug itself must be modified into a prodrug form to allow this adjustment of drug / matrix solubility. Using the active agent-loaded microparticles described herein embedded in the hydrogel matrix of the implant can avoid solubility issues and the use of prodrugs. In addition, changing the lipophilicity / hydrophilicity of the polymer can also be used to influence the degradation rate of the polymer matrix itself, which also has an additional impact on the release rate of the drug from the microparticles.

[0122] During the preparation of microparticles, solvents may be used and must be removed. Removal of the solvent can be achieved, for example, by heat treatment, freeze drying, evaporation, or vacuum drying. Some of these drying methods are limited or even impossible for non-crosslinked materials that undergo melting or glass transition at high temperatures. Other methods, such as freeze drying, are relatively expensive. In certain embodiments of the present invention, covalently crosslinked biodegradable polymers are used to produce thermally stable biodegradable microparticles.

[0123] In certain embodiments, the microparticles can be dimensionally stable to heat and will not melt, for example, at temperatures up to about 50°C, 60°C, 70°C, 80°C, 90°C, or about 100°C. Solvent extraction methods requiring heat treatment can be used without affecting the release characteristics of the microparticles. Furthermore, their thermal stability allows the microparticles to be used in extrusion processes, such as hot melt extrusion, or in 3D printing, for example, when incorporated into hydrogels or organogels for the production of composite implants.

[0124] In certain embodiments, during the microparticle production process, the particles are hardened or solidified by cross-linking, rather than simply by removing the solvent in an emulsion process, such as used with non-cross-linked polymers. This makes the microsphere production process faster and simpler.

[0125] In certain embodiments, the microparticles also have the following physical qualities: low modulus, dimensional stability, and favorable drug release kinetics. It has also been observed that the microparticles of certain embodiments of the present invention exhibit a release profile that is substantially temperature-independent, i.e., is not affected by temperature changes that occur under physiological conditions.

[0126] The microparticles may have a regular or irregular shape. In one general embodiment of the present disclosure, the microparticles are microspheres having a substantially spherical shape as it is typically obtained by the microparticle manufacturing methods described herein.

[0127] In one embodiment, the microparticles have a particle size (diameter) of about 0.1 μm to about 1000 μm, or about 1 μm to about 150 μm, about 1 μm to about 100 μm, about 20 μm to about 75 μm, about 10 μm to about 106 μm, or about 20 μm to about 55 μm, as determined by sieving, or have an average diameter in the range of about 0.1 μm to about 1000 μm, or about 1 μm to about 150 μm, about 1 μm to about 100 μm, about 20 μm to about 75 μm, about 10 μm to about 106 μm, or about 20 μm to about 55 μm, as determined by laser diffraction.

[0128] In one embodiment, the biodegradable microparticles may have a particle size distribution, for example, as determined by laser diffraction, having a D50 particle size of less than about 100 μm, or less than about 50 μm, or less than about 20 μm, and / or a D90 particle size of less than about 200 μm, or less than about 50 μm, or a D90 particle size of about 100 μm or less, or 30 μm or less, and / or a D90 particle size of about 20 μm or less. Can we add an optional lower limit?

[0129] In certain embodiments, the biodegradable microparticles consist of or consist essentially of at least one active agent and at least one covalently cross-linked biodegradable polymer. In other embodiments, the biodegradable microparticles comprise at least one active agent and a covalently cross-linked biodegradable polymer, and other additives may also be present in the biodegradable polymer.

[0130] Other additives for the biodegradable microparticles of embodiments of the present invention include hydrophobic organic liquids, such as oils, solvents, salts, porogens, buffers, non-crosslinked oligomers or polymers, sugars, visualizing agents, markers, and the like.

[0131] Microparticles can be formed by crosslinking biodegradable polymer precursors, such as functionalized PLA, PLGA, or other polymers disclosed herein, in the presence of a co-dissolved or particulate drug and a solvent. These microparticles can be composed of a single crosslinked polymer precursor or an oil / polymer blend. In certain embodiments, gelation into an organogel eliminates the need for rapid solvent removal and produces a rubbery material, i.e., a material above its glass transition temperature. After removal of any residual solvent, PLGA microparticles are typically glassy at room temperature. The Tg is a unique property of PLGA and depends on its composition (i.e., the ratio of lactide to glycolide) and molecular weight. Furthermore, with non-crosslinked PLGA, the Tg decreases after implantation due to degradation and increased moisture content in the body environment. In this case, the Tg typically drops below body temperature (plasticization), converting the glassy solid microparticles of prior art non-crosslinked PLGA into viscous liquid droplets in vivo, which can dramatically accelerate degradation kinetics and drug release rates in an uncontrolled manner. For oil-free organogel microparticles, the PLGA matrix becomes a glassy solid after complete solvent removal. Like non-crosslinked PLGA, crosslinked PLGA will gradually plasticize under physiological conditions. However, unlike non-crosslinked PLGA, crosslinked PLGA will transform into a rubber instead of a viscous liquid above Tg, which may show significant differences from non-crosslinked PLGA microparticles in terms of drug release kinetics. For organogel microparticles containing oil in the crosslinked polymer, the oil will act as a plasticizer, lowering the Tg and producing rubbery microparticles in its initial state. Therefore, Tg will no longer be the main rate-controlling property for controlling the release of the active agent. It is believed that in these embodiments, the effect of plasticization on drug release in vivo is small or negligible because no transition involving Tg will occur.

[0132] In certain embodiments, the biodegradable microparticles may comprise or consist of a blend of microparticles of varying particle sizes and / or having different polymers and / or comprising different active agents. For example, blends of microparticles of varying sizes and / or polymers of varying molecular weights may be used to control the kinetics of active agent release to achieve a desired release over time. Blends of microparticles with different active agents may be used to administer multiple drugs simultaneously or to co-release therapeutic and diagnostic agents from the same microparticle mixture.

[0133] According to the present invention, the composition of the biodegradable microparticles can be designed according to the needs of the intended use and therapeutic application. In one embodiment, the microparticles comprise 5 to 99 wt%, 5 to 90 wt%, 10 to 70 wt%, 10 to 60 wt%, 15 to 50 wt%, or 15 to 35 wt%, or 5 to 95 wt%, 10 to 95 wt%, 40 to 95 wt%, 50-90 wt%, 60-90 wt%, or 60-85 wt% of a covalently cross-linked polymer; as well as % active agent; wherein all weight percentages selected add up to 100% and the weight percentages are based on the total mass of the microparticle. In embodiments where the microparticle comprises an organogel that further comprises an oil, the amount of oil may range from 1 to 70% by weight, or 5 to 65% by weight, 5 to 60% by weight, 10 to 50% by weight, 10 to 40% by weight, 15 to 40% by weight, or 15 to 35% by weight, wherein all weight percentages selected add up to 100% and the weight percentages are based on the total mass of the microparticle.

[0134] The microparticles of the present invention can achieve high drug loading. In one embodiment, the biodegradable microparticles have a drug loading (active agent content) of at least about 5% by weight, at least about 10% by weight, at least about 20% by weight, at least about 30% by weight, at least about 35% by weight, at least about 40% by weight, at least about 45% by weight, at least about 50% by weight, at least about 55% by weight, at least about 60% by weight, at least about 65% by weight, at least about 70% by weight, or up to about 80% by weight (including any range of any of these values), based on the total mass of the microparticles. In one aspect, the microparticles contain from about 30% to about 60% by weight, such as from about 40% to about 55% by weight, such as from about 45% to about 50% by weight of the active agent, based on the total mass of the microparticles. For example, for a drug in the form of an oil, such as travoprost, the drug loading of the microparticles can be up to about 50% by weight, such as from about 10% to 45% by weight, or about 45% by weight, based on the total mass of the microparticles. For drugs such as dexamethasone, the drug loading of the microparticles can be up to about 70% by weight, such as up to about 65% by weight, or from about 40% to about 60% by weight, based on the total mass of the microparticles. Highly potent active agents can be included with lower drug loadings, such as from about 5% to about 20% by weight, or even lower, such as from about 1% to about 5% by weight, based on the total mass of the microparticles.

[0135] In one embodiment, the mass ratio of active agent to polymer in the microparticles is from about 3:1 to about 1:3, or from about 2:1 to about 1:2, or about 1:1.

[0136] In one embodiment, the biodegradable microparticles are incorporated into a hydrogel, organogel or xerogel to form a sustained release drug delivery system for use as an implant. In one aspect, the biodegradable microparticles are present in an amount of about 10% to about 35% by weight, or about 23% to about 27% by weight, or about 12% to about 17% by weight, or about 30% to about 35% by weight, or about 25% by weight, or about 15% by weight, or about 34% by weight, relative to the gross weight of the implant.

[0137] If an organogel is used to incorporate the biodegradable microparticles, the organogel can comprise from about 1% to about 90% by weight, or from about 5% to about 90% by weight, from about 5% to about 60% by weight, from about 10% to about 50% by weight, from about 10% to about 40% by weight, from about 15% to about 40% by weight, from about 15% to about 35% by weight of a hydrophobic organic liquid or oil; or from about 5% to about 95% by weight, or from about 10% to about 95% by weight, from about 40% to about 95% by weight, from about 15% to about 35% by weight of a hydrophobic organic liquid or oil. 50 wt % to about 90 wt %, about 60 wt % to about 90 wt %, or 60 wt % to about 85 wt % of a covalently cross-linked polymer gel matrix; and about 1 wt % to about 50 wt %, or about 5 wt % to about 50 wt %, about 5 wt % to about 40 wt %, about 10 wt % to about 30 wt %, or about 10 wt % to about 25 wt % of biodegradable microparticles; wherein all weight percentages selected add up to 100%, and the weight % are each based on the total dry weight of the drug delivery system or implant.

[0138] Biodegradable polymers

[0139] The biodegradable microparticles encapsulating active agents of certain embodiments of the present invention include three-dimensional covalently cross-linked polymers. The polymer units in the biodegradable polymer or its precursor can be selected from, for example, any of the following: biodegradable natural, semisynthetic, synthetic or biosynthetic polymers, or combinations thereof.

[0140] Natural polymers may include glycosaminoglycans, polysaccharides (eg dextran), polyamino acids and proteins, or mixtures or combinations thereof. Semi-synthetic polymers may be selected from carboxymethylcellulose or alkylcelluloses, such as methylcellulose (MC), ethylcellulose (EC).

[0141] In some aspects, synthetic precursors are used. Synthetic refers to molecules not found in nature or not normally found in the human body. Synthetic polymers can generally be any polymer produced by various types of polymerization, including free radical polymerization, anionic or cationic polymerization, chain growth or addition polymerization, condensation polymerization, ring-opening polymerization, etc. Polymerization can be initiated by certain initiators, by light and / or heat, and can be mediated by catalysts.

[0142] In general, the biodegradable microparticles encapsulating active agents according to certain embodiments of the present invention comprise a three-dimensional covalently cross-linked homopolymer or copolymer, which can be selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol; random or block copolymers, or a combination or mixture of any of them, or one or more of polyamino acids, glycosaminoglycans, polysaccharides or proteins.

[0143] In a first embodiment, the biodegradable microparticles comprise at least one of the following: cross-linked polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), polydioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or a copolymer of any of these, and include at least one active agent. In a specific embodiment thereof, the covalently cross-linked biodegradable polymer used in the microparticles of the present invention is one of cross-linked polylactic acid (PLA) or cross-linked polylactic-co-glycolic acid (PLGA).

[0144] In a second embodiment, the biodegradable microparticles include an organogel and at least one active agent, wherein the organogel comprises at least one cross-linked polymer selected from the group consisting of polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, random or block copolymers, or combinations or mixtures thereof, or one or more of polyamino acids, glycosaminoglycans, polysaccharides, or proteins. In specific embodiments, the covalently cross-linked biodegradable polymer is one of the following: cross-linked polyethylene glycol (PEG) or polypropylene glycol (PPG), cross-linked polylactic-co-glycolic acid (PLGA), or a cross-linked copolymer of PEG and PLGA. In some aspects thereof, the active agent itself can be an oil that forms a microparticle in the form of an organogel with the cross-linked polymer.

[0145] In other embodiments of the second embodiment, the biodegradable microparticles include an organogel comprising at least one cross-linked polymer selected from the group consisting of polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), polydioxanone, poly(trimethylene carbonate), polycaprolactone, and / or polyvinyl alcohol, or copolymers thereof; at least one oil; and at least one active agent. In specific embodiments, the covalently cross-linked biodegradable polymer is one of cross-linked polylactic acid (PLA) or cross-linked polylactic-co-glycolic acid (PLGA). In some aspects thereof, the active agent itself can be an oil that forms microparticles in the form of an organogel with the cross-linked polymer.

[0146] In other embodiments, copolymers of PEG and PLGA, particularly block copolymers formed by copolymerization of multi-arm PEG and PLGA, can also be used in a similar manner.

[0147] The hydrophilic polymer may be selected from polyglycolic acid (PGA), and at least one of polyethylene glycol or polypropylene glycol may also be used. In one embodiment, the hydrophilic polymer includes polyglycolic acid (PGA) or polyethylene glycol.

[0148] In another embodiment of the present invention, the covalently cross-linked polymer of the microparticles comprises a combination of a plurality of hydrophobic polymer units selected from at least one of polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA) and a plurality of at least one hydrophilic polymer unit selected from at least one of polyethylene glycol (PEG) units, polypropylene glycol (PPG) or polyglycolic acid (PGA) units. In one embodiment, the hydrophilic polymer units include polyethylene glycol (PEG) units.

[0149] In one embodiment, the cross-linked polymer of the microparticles is formed from a multi-arm precursor comprising a combination of polylactic-co-glycolic acid (PLGA) units and polyethylene glycol (PEG) units. The ratio of polylactic-co-glycolic acid (PLGA) units to polyethylene glycol (PEG) units can be selected to be from about 2.5:1 to about 1:2.5, or from about 2:1 to about 1:2, or about 1:1.

[0150] In embodiments using PLGA, the polylactic-co-glycolic acid (PLGA) units can have an L / G ratio (expressed as % L or G units) ranging from 0:100 to 100:0, or from about 1:99 to about 99:1, or from about 10:90 to about 90:10, or from about 25:75 to about 75:25, or 50:50.

[0151] In certain embodiments, in the biodegradable microparticles, the polymers are covalently cross-linked via hydrolyzable bonds between the polymer units, which facilitates biodegradation in an in vivo aqueous environment, such as in the human or animal body.

[0152] The hydrolyzable bond may comprise a bond or linkage selected from the group consisting of an amine, amide, carbamate, ester, anhydride, ether, acetal, ketal, nitrile, isonitrile, isothiocyanate or imine bond, and combinations thereof. These bonds are typically formed by polycondensation of an appropriately functionalized gelling agent or precursor, respectively.

[0153] Precursor components

[0154] In embodiments of the present invention, covalently cross-linked polymers are formed by chemical covalently cross-linking multifunctional precursors. On the one hand, the precursor is a functionalized monomer, oligomer or polymer molecule with a functional group that can be cross-linked with other precursors or small molecule cross-linking agents. Small molecule precursors generally refer to precursors less than about 2000 daltons. Examples of small molecule cross-linking agents include diamines, triamines or tetramine compounds, diisocyanates or triisocyanates, etc. Non-limiting examples include ethylenediamine, tris (2-aminoethyl) amine (TAEA) or trilysine. Precursors and small molecule cross-linking agents can be linear or nonlinear, such as branched, star-shaped, comb-shaped or dendritic polymers, etc.

[0155] In one embodiment, at least one precursor or small molecule cross-linking agent has a chemical cross-linking functionality greater than 2, such as 3 to 10, or 3 to 9, or 4 to 8, or 4. In one aspect, at least one precursor or small molecule cross-linking agent has a functionality equal to or greater than 3, so as to produce a three-dimensional (3D) polymer network. This precursor can be a nonlinear, branched, star-shaped, comb-like or dendritic polymer. Therefore, if a linear bifunctional polymer precursor is used in one embodiment, small molecule cross-linking agent or the second polymer cross-linking agent are at least trifunctional, so that three-dimensional cross-linking can occur, forming a polymer matrix comprising an activating agent and an optional oil. When using a bifunctional small molecule cross-linking agent, at least one multi-arm polymer precursor should have a functionality of 3 or higher, to realize the three-dimensional cross-linking of the polymer matrix.

[0156] In one embodiment, the at least one precursor is a star-shaped, multi-armed or dendritic polymer precursor having a core and 2 to 10 arms, or 3 to 10 arms, 4 to 8 arms, or 4 or 6 arms, each arm comprising a polymer unit and having a terminal end. The polymer unit may comprise one or more of the following: a polyoxyalkylene such as polyethylene glycol, polypropylene glycol, poly(ethylene glycol)-block-poly(propylene glycol) copolymer, a poloxamer such as the commercially available Tetronic ® or commercially available Jeffamine ®Polymers, polyethylene oxide, polypropylene oxide; polyvinyl acetate, polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polyp-dioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or copolymers, random or block copolymers of any of them, or combinations or mixtures of any of them, or one or more of the following units: polyamino acids, glycosaminoglycans, polysaccharides or proteins, but this list is not intended to be limiting.

[0157] Biodegradable microparticles comprising covalently linked polymers can be formed from a plurality of hydrophobic polymer units, a plurality of hydrophilic polymer units, or a combination of hydrophobic and hydrophilic units. The polymer units can be selected to tailor the hydrophobicity and hydrophilicity of the microparticles to the characteristics of the active agent. This adjustment can control certain aspects of the release kinetics and degradation behavior of the microparticles.

[0158] In one embodiment of the present invention, the multi-arm precursor of the hydrophobic biodegradable polymer unit may include at least one of polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA) units. The polymer unit is appropriately functionalized with the desired reactive groups at its termini, and the molecular weight of the PLA or PLGA, or the L / G ratio of the PLGA copolymer can be varied according to the desired polymer properties (e.g., hydrophobicity). Polycaprolactone, polyvinyl alcohol, or poly(vinyl pyrrolidone) may also be used.

[0159] In the first embodiment mentioned above, the biodegradable microparticles comprise a covalently crosslinked polymer containing an active agent, and the polymer matrix or network is formed from at least one covalently crosslinkable precursor that is miscible with and / or soluble in a solvent. The precursor comprises polymer units of polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), polycaprolactone, and / or polyvinyl alcohol. The active agent can be dissolved in the same solvent or dispersed therein in particulate form.

[0160] In the second embodiment mentioned above, when the biodegradable microparticles comprise an organogel containing an oil (as an additive in addition to the active agent or the active agent is an oil), the polymer matrix of the organogel is formed from at least one covalently crosslinkable precursor comprising polymer units as defined herein, said covalently crosslinkable precursor being miscible with the oil, preferably soluble or dispersible in the oil, or optionally a mixture of an oil and a solvent.

[0161] In some embodiments, the microparticles comprise a polymer network or matrix, optionally in the form of an organogel, comprising or formed from at least one covalently cross-linked multi-arm precursor and a small molecule cross-linker. In other embodiments of the invention, the microparticles comprise a polymer network or matrix, optionally in the form of an organogel, comprising or formed from at least two covalently cross-linked multi-arm precursors.

[0162] Thus, a precursor is always a "functional polymer" or "functional material," such as a crosslinker (e.g., a small molecule with a low molecular weight), which is capable of participating in a crosslinking reaction with another precursor to form a covalently crosslinked polymer network (or matrix). Thus, the term "non-functional polymer" refers to a polymer that may be present in the organogel of the present invention but does not participate in a crosslinking reaction with a precursor to form a polymer network. The selection of a precursor should take into account the desired properties of the resulting particulate polymer and its structure upon formation, for example, if the crosslinked matrix is ​​formed as an organogel, compatibility with organic solvents should be considered.

[0163] The precursor used in the present invention may include any polymer unit described above so long as it is capable of reacting with another precursor or a crosslinking agent in the presence of an active agent and optionally an oil to form a biocompatible and biodegradable crosslinked polymer in microparticle form.

[0164] The crosslinked polymer matrix for the biodegradable microparticles may be formed from any of the biodegradable polymers mentioned in the above section, and the precursors to be covalently crosslinked comprise these polymer units carrying functional groups capable of chemically crosslinking the precursors by forming covalent bonds to form the crosslinked polymer matrix.

[0165] In some aspects of the invention, at least one cross-linkable precursor is hydrophobic or hydrophilic, and when two precursors are used, both can be hydrophobic, both can be hydrophilic, or one can be hydrophobic and the other can be hydrophilic. For more than two precursors, any mixture of hydrophilic and hydrophobic precursors can be selected, depending on the desired properties of the microparticles. Furthermore, the precursors can be copolymers incorporating both hydrophobic and hydrophilic substructures.

[0166] Functional groups for cross-linking

[0167] The precursor has a functional group pair that reacts with each other, that is, a first functional group on the first precursor that can react with the second functional group on the second precursor or the cross-linking agent. In one embodiment, the first multi-arm precursor comprising the first functional group reacts with the second multi-arm precursor or the small molecule cross-linking agent comprising the second functional group, and the functional group is positioned at the end of each arm of the precursor or the cross-linking agent, wherein the first functional group or the second functional group can be directly grafted to the end of the precursor, or are grafted to the end of the precursor by a connector molecule. These functional groups can react with each other and form covalent bonds or linkages, such as in electrophilic reagent-nucleophilic reagent reactions, or are configured to participate in other chemical cross-linking reactions described below.

[0168] In certain embodiments of the present invention, the first functional group and the second functional group are selected from electrophiles and nucleophiles; functional groups for click chemistry; functional groups for cycloaddition reactions, particularly 1,3 dipolar cycloaddition reactions and hetero-Diels-Alder cycloaddition reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; polymerizable vinyl groups, or combinations thereof. Those skilled in the art will recognize that certain functional group pairs can be classified into multiple groups within these groups. For example, in click chemistry, the reaction of azide with dibenzocyclooctyne can also be considered an electrophile-nucleophile reaction pair.

[0169] Thus, in one embodiment, the first functional group may be a nucleophile and the second functional group may be an electrophile, or vice versa, and the reaction between the first functional group and the second functional group is an electrophile-nucleophile reaction to form a covalent bond. According to certain embodiments of the present invention, each precursor or cross-linker comprises at least two or at least three terminal nucleophilic groups, or at least two or at least three terminal electrophilic groups.

[0170] The nucleophile may be selected from one of the following: an amine, such as a primary amine; a hydroxyl group; a thiol group; a carboxyl group; a dibenzocyclooctyne group; or a hydrazine group. In certain embodiments, at least one precursor comprises a nucleophile, such as a primary amine.

[0171] Electrophiles that can be used in the present invention can be selected from active ester groups such as succinimidyl esters, succinimidyl carbonates; nitrophenyl carbonates, aldehydes, ketones, acrylates, acrylamides, maleimides, vinyl sulfones, iodoacetamides, alkenes, alkynes, azides, norbornenes, epoxides, mesylates, tosylates, trifluoroethanesulfonyls, cyanurates, orthopyridyl disulfides or halogens. These electrophiles contain functional groups that participate in electrophile-nucleophile reactions and crosslink precursors, and they preferably further include reactive groups that include hydrolyzable groups or bonds such as glutarates. For example, in one embodiment of the present invention, the succinimidyl esters may include reactive groups such as succinimidyl succinate (SS), succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ) or succinimidyl glutaramide. Such electrophile-nucleophile cross-linking reactions of multi-arm PEG precursors are described, for example, in US 2002 / 0042473 A1, which is incorporated by reference.

[0172] Thus, in one embodiment, the first functional group and the second functional group are selected from functional group pairs used for click chemistry to form a covalent bond. For example, in the case of azide and dibenzocyclooctyne functionalization, the precursors can be cross-linked by so-called click chemistry reactions. A review of such reactions is provided in HC Kolb; MG Finn; KB Sharpless (2001). "Click Chemistry: Diverse Chemical Function from a Few Good Reactions", Angewandte Chemie International Edition, 40 (11): 2004–2021), which is incorporated herein by reference.

[0173] The functional groups used in click chemistry can be functional groups selected for cycloaddition reactions, in particular 1,3 dipolar cycloaddition reactions, [3+2] cycloaddition reactions such as olefin-nitrone cycloaddition reactions or alkyne-nitrone cycloaddition reactions, [4+2] cycloaddition reactions, hetero Diels-Alder cycloaddition reactions; functional groups for thiol-ene reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol type carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; functional groups for Michael type addition reactions.

[0174] For example, the first functional group is an alkyne compound, such as dibenzocyclooctyne (DBCO) or bicyclo[6.1.0]-nonyne (BCN); or norbornene or trans-cyclooctene (TCO), and the second functional group is azide, 3,4-dihydroxyphenylacetic acid (DHPA) or tetrazine (Tz). In these embodiments, DBCO, BCN, norbornene, TCO, azide, DHPA and Tz functional groups are grafted to the ends of the multi-arm precursor via a linker, such as an acid group, a diacid group, a functionalized aliphatic group, a heteroaliphatic group, or an aromatic group or a heteroaromatic group.

[0175] In another embodiment, the first and second functional groups are selected for a [3+2] cycloaddition reaction, such as an alkene-nitrone cycloaddition reaction or an alkyne-nitrone cycloaddition reaction. In another embodiment, the first and second functional groups are selected for a [4+2] cycloaddition reaction, particularly a hetero-Dickens-Alder reaction, wherein the first functional group is an aldehyde or imine compound and the second functional group is a 1,3-diene compound, an unsaturated carbonyl compound, or a nitroso-alkene compound. In yet another embodiment, the first and second functional groups are selected for a thiol-ene reaction, wherein the first functional group is a thiol compound and the second functional group is an alkene, preferably a terminal alkene. In another embodiment, the first and second functional groups are selected for a nucleophilic ring opening, wherein the first functional group is selected from an epoxide, a thiirane, an aziridine, or a lactam, and the second functional group is a nucleophile as mentioned above. In another embodiment, the first and second functional groups are selected for a non-aldol type carbonyl reaction, wherein the first functional group is an aldehyde or ketone compound and the second functional group is a primary amine, hydrazine, hydrazide, or aminooxy compound for forming an imine, amide, isourea, hydrazone, acylhydrazone, or oxime linkage.

[0176] In yet another embodiment, the first functional group and the second functional group are selected from free radical polymerizable / crosslinkable functional groups.

[0177] In these embodiments, the first functional group and the second functional group are selected from, for example, polymerizable vinyl groups and acrylates, such as (meth)acrylic acid, (meth)acrylates, acrylamides, fumaric acid, maleic acid, and combinations thereof. Crosslinking is induced thermally or photochemically, optionally with the use of an initiator, for example, a photoinitiator, such as a free radical photoinitiator (Norish I type, such as 2,2-dimethoxy-1,2-diphenyl-ethan-1-one, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxy-cyclohexylphenyl ketone; or Norish II type, such as benzophenone and its derivatives and isopropylthioxanthone in combination with a synergist such as tertiary amines 2-ethylhexyl-(4-N,N-dimethylamino)benzoate and 2-ethyl-(4-N,N-dimethylamino)benzoate); or a cationic photoinitiator.

[0178] Such a crosslinking mechanism with terminal vinyl-functionalized precursors is described, for example, in US 2021 / 0251893 A1, which is incorporated herein by reference.

[0179] Multi-armed precursor

[0180] The term "multi-arm" precursor means that the precursor is branched, i.e., nonlinear. In the case of a multi-arm polymer, the core refers to a continuous portion of a molecule that is engaged with a polymer unit arm extending from the core, wherein the arm has a nucleophilic or electrophilic functional group, which is typically located at the end of the branch. The precursor may have, for example, 2-100 arms, each of which has an end, keeping in mind that some precursors may be dendrimers or other highly branched materials, such as dendrimers. The arms on the precursor refer to a linear chain of chemical groups connecting a crosslinkable group to the polymer core, i.e., a polymer unit as defined herein. Some embodiments are precursors with between 3 and 300 arms; the skilled person will immediately appreciate that all ranges and values ​​within the explicitly stated range are encompassed, such as 4, 6, 8, 10, 12, 4 to 16, 8 to 100, 6, 8, 10, 12, or at least 4 arms.

[0181] In certain embodiments, multi-arm precursor of the present invention has a core and 2 to 10 arms, or 3 to 10 arms, 4 to 8 arms or 4 or 8 arms, and each arm comprises polymer unit and has end, and described end has the above defined functional group for crosslinking.Because in multi-arm precursor, arm extends from central core, their polymer end is identical, and all arms can be functionalized with identical functional group in a single reaction.

[0182] Each polymer unit in the multi-arm precursor can have an average molecular weight (Mw) ranging, for example, from about 1,000 to about 100,000 Daltons, or from about 10,000 to about 60,000 Daltons, or from about 15,000 to about 50,000 Daltons.

[0183] core

[0184] The core of the multi-arm precursor is a structure suitable for providing the desired number of precursor arms. For example, for a 4-arm polymer unit and precursor, the core can be a pentaerythritol or ethylenediamine structure, while for an 8-arm polymer unit and precursor, the core can be a hexaglycerol structure.

[0185] As disclosed above, in certain embodiments, the polymer network of biodegradable microparticles is formed by at least two precursors, at least one of which is a multi-arm precursor and the other is a small molecule cross-linking agent, or is also a multi-arm precursor. The first multi-arm precursor comprises a first functional group, and the second precursor selected from a small molecule cross-linking agent or a multi-arm precursor comprises a second functional group, and the functional group is located at the end of the arm or the molecule. In various embodiments of the present invention, the first functional group and the second functional group are each selected from the group of cross-linkable functional groups defined above. In some embodiments, the functional group is selected from electrophiles and nucleophiles, and the reaction between the first functional group and the second functional group is an electrophile-nucleophile reaction or a condensation reaction that forms a covalent bond in the polymer of the biodegradable microparticles.

[0186] In some embodiments, when every kind of precursor is multi-arm, it comprises two or more arms, and thus for example comprises two or more identical or different electrophiles or nucleophiles, or any one of above other cross-linkable first and second functional groups to, thus make every kind of nucleophile can react with another electrophile (in the same precursor or another precursor) in electrophile-nucleophile reaction, to form a cross-linked polymer product.Therefore, for example, in some respects, precursor has at least 4 arms, at least 8 arms or at least 10 arms, wherein each arm is with nucleophile or electrophile end-blocking, and described nucleophile or electrophile may or may not be identical with its other arms.

[0187] In one embodiment, the biodegradable microparticles include at least two multi-arm precursors, the multi-arm precursors including a first multi-arm precursor containing a nucleophile and a second multi-arm precursor containing an electrophile. In this embodiment, the first multi-arm precursor and the second multi-arm precursor are covalently cross-linked in an electrophile-nucleophile reaction. In this case, multi-arm refers to at least 4 arms, at least 8 arms, such as at least 10 arms. In this embodiment, the nucleophile can be an amine, such as a primary amine; a thiol; a dibenzocyclooctyne; or a hydrazine, and the electrophile can be a succinimidyl ester, a succinimidyl carbonate, a nitrophenyl carbonate, an aldehyde, a ketone, an acrylate, an acrylamide, a maleimide, a vinyl sulfone, an iodoacetamide, an alkene, an alkyne, an azide, a norbornene, an epoxide, a mesylate, a tosylate, a trifluoroethanesulfonyl, a cyanurate, an orthopyridyl disulfide, or a halide. For example, in one embodiment of the invention, the succinimide ester may comprise a reactive group such as succinimidyl succinate (SS), succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ), or succinimidyl glutaramide.

[0188] Some precursors may have longer hydrolysis half-lives than other precursors. This means that the time required for their degradation may be longer. This may be partly due to the reactive groups contained in the precursor. For example, PLPGA polymers containing electrophilic groups, such as succinimidyl ester groups containing reactive groups such as succinimidyl glutarate (SG), have shorter hydrolysis half-lives than PLPGA polymers containing electrophilic groups, such as succinimidyl ester groups containing reactive groups such as succinimidyl succinate (SS).

[0189] In one embodiment, the biodegradable microparticle comprises two multi-arm precursors, and may include a first multi-arm precursor containing a nucleophile such as an amine and a second multi-arm precursor containing an electrophile such as a succinimidyl ester. In another embodiment, the biodegradable microparticle cross-linked polymer may include a first multi-arm precursor containing a nucleophile such as an amine (such as a primary amine) and a second multi-arm precursor containing an electrophile such as a succinimidyl ester, wherein the succinimidyl ester comprises a first reactive group. In this embodiment, the reactive group is selected from succinimidyl succinate (SS), succinimidyl glutarate (SG), succinimidyl adipate (SAP), or succinimidyl azelate (SAZ).

[0190] As disclosed above, the polymer network of biodegradable microparticles is formed by at least two precursors, at least one of which is a multi-arm precursor and the other is a small molecule cross-linking agent, or is also a multi-arm precursor. The first multi-arm precursor comprises a first functional group, and the second precursor selected from a small molecule cross-linking agent or a multi-arm precursor comprises a second functional group, and the functional group is located at the end of the arm or the molecule. In various embodiments of the present invention, the first functional group and the second functional group are each selected from the group of cross-linkable functional groups defined above. In some embodiments, the functional group is selected from electrophiles and nucleophiles, and the reaction between the first functional group and the second functional group is an electrophile-nucleophile reaction or a condensation reaction that forms a covalent bond in the polymer of the biodegradable microparticle.

[0191] PLA / PLGA precursor

[0192] In certain embodiments, the precursor is a polylactic-co-glycolic acid (PLGA) precursor, ie, having PLGA polymer units at the core of the multi-arm precursor.

[0193] In one embodiment, these precursors may have the following exemplary structure, with a pentaerythritol-derivatized, rather hydrophobic and oil-soluble 4a20K PLGA-NHS core:

[0194]

[0195] As its name suggests, this is a 4-arm PLGA in which each PLGA unit has an Mn of approximately 5,000 daltons and the PLGA units have an L / G ratio of 50:50 (i.e., 1:1). R, along with the two carbonyl groups to which it is attached, is part of a diacid linker derived from a saturated or unsaturated biocompatible organic diacid, such as one of the following: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, or fumaric acid, and NHS represents an N-hydroxysuccinimide electrophile as a functional group at the end of each arm. x is an integer and defines the number of lactic acid units, and y is an integer defining the number of glycolic acid units in the PLGA molecule. For 50:50 PLGA, x and y are equal. n is an integer defining the number of PLGA blocks in the optional block copolymer; for 50:50 PLGA, n is 1.

[0196] Another example of an electrophile-functionalized 4-arm PLGA precursor is 4a20K PLGA5050-SAP-NHS (x and y are about 15):

[0197]

[0198] In other embodiments, multi-arm PLGA precursors can also be derived from ethylenediamine as the core instead of pentaerythritol. Using different cores, the precursor can have more than 4 arms, such as 6, 8, 10 or 12 arms, up to dendrimers with up to 100 or more arms.

[0199] In various embodiments of the present invention, the biodegradable microparticle cross-linked polymer comprises or is constructed from a multi-arm precursor comprising polymer units, i.e., polylactic-co-glycolic acid (PLGA) units, and in other embodiments, polylactic acid (PLA) units, or combinations or (block) copolymers thereof. In such embodiments, the biodegradable microparticles are formed using at least one cross-linking agent, preferably a small molecule amine, such as oil-soluble tris(2-aminoethyl)amine (TAEA) or trilysine.

[0200] In certain embodiments, polylactic acid (PLA) units are preferred.

[0201] In some embodiments, these PLGA and / or PLA based microparticles may include oil to form an organogel as a biodegradable microparticle.

[0202] In some embodiments of the present invention, the biodegradable microparticle cross-linked polymer comprises: at least one multi-arm precursor comprising hydrophobic polymer units, wherein the hydrophobic polymer units are selected from polylactic acid (PLA) units and polylactic-co-glycolic acid (PLGA) units, or combinations or (block) copolymers thereof; and at least one other multi-arm precursor comprising hydrophilic polymer units, wherein the hydrophilic polymer units are preferably selected from polyethylene glycol (PEG) and polyglycolic acid (PGA).

[0203] In certain embodiments of the present invention, the PLA and / or PLGA units used in the precursor have a mean molecular weight in the range of about 1,000 to about 100,000 daltons, or in the range of about 10,000 to about 60,000 daltons, or in the range of about 15,000 to about 50,000 daltons. In some embodiments, the PLA and / or PLGA units have a mean molecular weight in the range of about 10,000 to about 40,000 daltons, or about 20,000 daltons. PLA and / or PLGA precursors having the same mean molecular weight can be used, or PLA and / or PLGA precursors having different mean molecular weights can be combined with each other. The mean molecular weight of the PLA and / or PLGA precursors used in the present invention is given as a number average molecular weight (Mn), and in certain embodiments, Mn can be determined relative to polystyrene standards by gel permeation chromatography according to a standardized method.

[0204] The above-mentioned precursors are commercially available, for example, 4-arm PLA SS (20k), 4-arm PLGA 50:50 SS (20k, 60k) or 4-arm PLGA 75:25 SS (20k, 60k), etc., can be obtained from Nanosoft Polymers in Winston-Salem, US or other suppliers, such as Creative PEGWorks in Chapel Hill, NC, USA, SinoPEG in China or Akina Inc. in West Lafayette, Indiana, USA.

[0205] PEG precursor

[0206] In some embodiments, the precursor is a polyethylene glycol precursor, that is, there is a polyethylene glycol polymer unit at the core of the multi-arm precursor. Therefore, in some embodiments, the polymer network of the microparticles of the covalently cross-linked precursor is made from at least one precursor containing polyethylene glycol or includes at least one precursor containing polyethylene glycol. Polyethylene glycol (PEG, also referred to as polyethylene oxide) refers to a polymer with a repeating group (CH2CH2O)n, where n is at least 3.

[0207] The polymer precursor with polyethylene glycol has at least three of these repeating groups that are interconnected in a linear series manner. The PEG polymer that does not participate in the cross-linking reaction between the precursor with hydroxyl or methoxy end-blocking is referred to as " non-functional PEG " as described above, and therefore is not used as one of precursor. Therefore, the PEG polymer that is end-blocked with a nucleophile selected from primary amine, thiol, dibenzocyclooctyne or hydrazine is considered to be " functional PEG ", and can be used as one of precursor. In addition, the PEG polymer that is end-blocked with an electrophile is considered to be " functional PEG ", and can be used as one of precursor, and the electrophile is selected from succinimidyl ester, succinimidyl carbonate, nitrophenyl carbonate, aldehyde, ketone, acrylate, acrylamide, maleimide, vinyl sulfone, iodoacetamide, alkene, alkynes, azide, norbornene, epoxide, mesylate, tosylate, trifluoroethanesulfonyl, cyanurate, adjacent pyridyl disulfide or halide.

[0208] The polymer network of the biodegradable microparticle drug delivery system of the present invention can comprise one or more multi-arm PEG precursors having 2 to 10 arms, or 4 to 8 arms, or 4, 5, 6, 7 or 8 arms. It should be noted that, since the multi-arm precursor has a core, a 2-arm PEG precursor differs from a simple linear PEG, for example, by the presence of a core structure. The two-arm precursor can form a 3D cross-linked network with a cross-linking agent having a functionality of at least 3. The PEG precursors can have different or equal numbers of arms. In certain embodiments, the PEG precursors used in the organogel of the present invention have 4 and / or 8 arms. In certain embodiments, a combination of 4-arm and 8-arm PEG precursors is utilized.

[0209] In certain embodiments of the present invention, the polyethylene glycol unit used as a precursor has a mean molecular weight within the range of about 1,000 to about 100,000 daltons, or within the range of about 10,000 to about 60,000 daltons, or within the range of about 15,000 to about 50,000 daltons. In some embodiments, the polyethylene glycol unit has a mean molecular weight within the range of about 10,000 to about 40,000 daltons or about 20,000 daltons. The PEG precursor having the same mean molecular weight can be used, or the PEG precursors having different mean molecular weights can be combined with each other. The mean molecular weight of the PEG precursor used in the present invention is given as a number average molecular weight (Mn), and in certain embodiments, Mn can be determined relative to polystyrene standards by gel permeation chromatography according to a standardized method.

[0210] In a 4-arm PEG, the average arm length (or molecular weight) of each arm can be the total molecular weight of the PEG divided by 4. Thus, a 4a20kPEG precursor, as a precursor that can be used in the present invention, has 4 arms, wherein the average molecular weight of each arm is about 5,000 Daltons. Thus, in addition to the 4a20kPEG precursor, an 8a20k PEG precursor that can also be used in the present invention has 8 arms, each having an average molecular weight of 2,500 Daltons. Thus, a 4a20K PLGA precursor has 4 arms, wherein the average molecular weight of each arm is about 5,000 Daltons.

[0211] In general, when referring to a polymer precursor having a specific average molecular weight, such as a 15kPEG precursor or a 20kPLGA precursor, the average molecular weight indicated (i.e., an Mn of 15,000 or 20,000, respectively) refers to the polymer unit portion of the precursor before the addition of the end groups ("20k" herein means 20,000 Daltons, and "15k" means 15,000 Daltons, and the same abbreviations are used herein for other average molecular weights of PEG or other polymer precursors). In certain embodiments, the Mn of the polymer unit portion of the precursor is determined by gel permeation chromatography relative to polystyrene standards according to standardized methods. The degree of substitution of the end groups disclosed herein can be determined by H-NMR after end group functionalization.

[0212] In various embodiments of the present invention, the biodegradable microparticles comprise at least two multi-arm precursors, the first precursor being a multi-arm PEG precursor comprising a nucleophile such as an amine (such as a primary amine). In some of these embodiments, the second multi-arm precursor is a multi-arm PEG precursor comprising an electrophile such as a succinimidyl ester. In other embodiments of these embodiments, the second multi-arm precursor is a multi-arm PLGA precursor comprising an electrophile such as a succinimidyl ester.

[0213] In some embodiments of the present invention, the biodegradable microparticle cross-linked polymer comprises three multi-arm precursors, the first multi-arm precursor being a multi-arm PEG precursor comprising a nucleophile such as an amine (such as a primary amine). In this embodiment, the second multi-arm precursor is a multi-arm PEG precursor comprising an electrophile such as a succinimidyl ester, wherein the succinimidyl ester comprises a first reactive group. In this embodiment, the third multi-arm precursor is a multi-arm PEG precursor comprising an electrophile such as a succinimidyl ester, wherein the succinimidyl ester comprises a second reactive group. In this embodiment, the first reactive group and the second reactive group can be selected from succinimidyl succinate (SS), succinimidyl glutarate (SG), succinimidyl adipate (SAP), or succinimidyl azelate (SAZ). SS, SG, SAP and SAZ are all functionalized linkers attached to a polymer comprising a reactive group consisting of an N-succinimidyl ester of the corresponding diacid having an ester linkage to the polymer at the second acid of the diacid that can be degraded by hydrolysis in water. In some embodiments, the first multi-arm precursor is succinimidyl succinate (SS) and the second multi-arm precursor is succinimidyl glutarate (SG).

[0214] Each and any combination of the PEG precursor containing electrophilic group and nucleophilic group disclosed herein can be used for preparing implants according to the present invention. For example, any 4-arm or 8-arm PEG precursor (for example, with the succinimide ester comprising SS, SG, SAP or SAZ reactive groups) can be combined with any 4-arm or 8-arm PEG precursor (for example, with NH2 group or another nucleophilic group). In addition, the PEG unit of the precursor containing electrophilic group and nucleophilic group can have the same average molecular weight, or can have different average molecular weights.

[0215] One such combination is a PEG amine precursor and two PEG succinimidyl ester precursors, one containing an SS reactive group and the other containing an SG reactive group. In certain embodiments, the present inventors have discovered that by maintaining a molar ratio of PEG amine to PEG succinimidyl ester of approximately 1:1 and by varying the molar ratio of the reactive groups, succinimidyl ester SS and SG, the time it takes for the polymer network to degrade in aqueous solution under physiological conditions can be controlled, although other ratios are also contemplated. The amounts of PEG SS and SG used to achieve a specific molar ratio of the two reactive groups can be calculated by a skilled artisan and are described below.

[0216] The amount of PEG amine and PEG ester (SS and SG) to be used is calculated by stoichiometric equations of molar ratios and converting moles to grams. First, the reactive end group molar ratios between the amine, succinimidyl succinate, and succinimidyl glutarate are determined. In an exemplary formulation, 4a20k PEG NH2, 4a20k PEG SS, and 4a40k PEGSG are used. The molar ratio between the amine and succinimidyl ester groups is approximately 1:1, and the molar ratio between SS and SG is approximately 80:20. The final end group molar ratio between 4a20k NH2: 4a20k SS: 4a40k SG is approximately 1.0: 0.8: 0.2. Next, the mass amounts are determined using stoichiometric conversions of grams to moles and moles to grams. An exemplary 4a20k SS calculation using 100 g of 4a20k NH2 at the above molar ratios is summarized below:

[0217]

[0218] Alternatively, the amount of PEG can be determined by calculating the molecular weight between crosslinks (MWc) and the arm length ratio. MWc can be calculated by summing the average arm lengths of each multi-arm PEG precursor.

[0219]

[0220]

[0221] The arm length ratio is calculated by dividing the PEG arm length by the MWc. The amount of a multi-arm precursor can be determined by multiplying the arm length ratio of a particular multi-arm precursor by the total PEG batch size. An exemplary calculation for the amount of 4a20k PEG SS is outlined below for a total batch size of 100 g PEG:

[0222]

[0223]

[0224]

[0225]

[0226]

[0227]

[0228] Similar calculations can be performed for other types of polymers described herein.

[0229] In certain embodiments, 4-arm PEG having an average molecular weight of about 20,000 Daltons and 4-arm PEG having an average molecular weight of about 40,000 Daltons can be used to form the covalently cross-linked polymers of microparticles according to the present invention.

[0230] Thus, the first precursor and / or the second precursor may be a 4a20k precursor, where 4 represents the number of arms and 20k represents Mn. Thus, for example, the first precursor, the second precursor, and / or the third precursor may be a 4a40k precursor. Thus, for example, the first precursor and / or the second precursor may be a 4a20k precursor, and the third precursor may be a 4a40k precursor.

[0231] Active agent:

[0232] The active agent in the biodegradable microparticles according to embodiments of the present invention may be a therapeutic active agent or a diagnostic active agent, or a combination thereof. It may be a single active agent or multiple active agents.

[0233] The therapeutically active agent can be a steroid; a nonsteroidal anti-inflammatory drug (NSAIDS), such as diclofenac, ibuprofen, meclofenamic acid, mefenamic acid A, salicylate, sulindac, tolmetin, ketoprofen, diflunisal, piroxicam, naproxen, etodolac, flurbiprofen, fenoprofen C, indomethacin, celecoxib, ketorolac, nepafenac; an intraocular pressure-lowering drug; an antibiotic, such as ciprofloxacin; an analgesic, such as bupivacaine; a calcium channel blocker, such as nifedipine; a cell cycle inhibitor, such as simvastatin; a protein, such as insulin; a small molecule hydrophilic drug, including a carboxylate and amine salts; small molecule hydrophobic drugs, hydrophilic peptides and protein drugs, such as insulin, single-chain antibody fragments, Fab fragments, IgG antibodies, fusion antibodies, etc.; aptamers; in particular bupivacaine (BPV-HCl or base), ropivacaine (RPV), dexamethasone, travoprost, axitinib, non-steroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics, analgesics, calcium channel blockers, cell cycle inhibitors, chemotherapeutic agents, antiviral drugs, anesthetics, hormones, anticancer drugs, antitumor agents, viruses, viruses for gene delivery such as AAV, etc., or any combination thereof.

[0234] In some embodiments, the steroid can be a corticosteroid, which can include hydrocortisone, loteprednol, cortisol, cortisone, prednisolone, methylprednisolone, dexamethasone, betamethasone, triamcinolone, aldosterone, or fludrocortisone.

[0235] In some embodiments, the NSAID can include diclofenac (e.g., diclofenac sodium), flubiprofen (e.g., flurbiprofen sodium), ketorolac (e.g., ketorolac tromethamine), bromfenac, or nepafenac.

[0236] In some embodiments, IOP lowering agents and / or glaucoma medications may include prostaglandin analogs (e.g., bimatoprost, latanoprost, travoprost, or latanoprostene bunod), rho kinase inhibitors (e.g., netarsudil), adrenergic agonists (epinephrine or dipivefrin), beta-adrenergic antagonists (also known as beta blockers), In some embodiments, the present invention includes but is not limited to: (e.g., timolol, levobunolol, metipranolol, carteolol, or betaxolol), α2-adrenergic agonists (e.g., apraclonidine, brimonidine, or brimonidine tartrate), carbonic anhydrase inhibitors (e.g., brinzolamide, dichlorphenamide, methazolamide, acetazolamide, acetazolamide, or dorzolamide), pilocarpine, echothiophate, demercarium, physostigmine, and / or isofluorophate.

[0237] In some embodiments, anti-infective drugs may include antibiotics including ciprofloxacin, tobramycin, erythromycin, ofloxacin, gentamicin, fluoroquinolone antibiotics, moxifloxacin, and / or gatifloxacin; antiviral drugs including ganciclovir, idoxuridine, vidarabine, and / or trifluridine; and / or antifungal drugs including amphotericin B. B), natamycin, voriconazole, fluconazole, miconazole, clotrimazole, ketoconazole, posaconazole, echinocandin, caspofungin and / or micafungin.

[0238] In some embodiments, antimetabolites may include methotrexate, mycophenolate, or azathioprine.

[0239] In some embodiments, anti-fibrotic agents may include mitomycin C or 5-fluorouracil.

[0240] In some embodiments, angiogenesis inhibitors may include anti-VEGF agents (e.g., aflibercept, ranibizumab, bevacizumab), PDGF-B inhibitors (e.g., Fovista®), complement antagonists or inhibitors (e.g., eculizumab, avaccincaptad pegol), tyrosine kinase inhibitors (e.g., sunitinib, axitinib), and / or integrin antagonists (e.g., natalizumab and vedolizumab).

[0241] In some embodiments, the cytoprotectant may include ebselen, sulforaphane, oltipraz, or dimethyl fumarate.

[0242] In some embodiments, neuroprotective agents may include ursodiol, memantine, or acetylcysteine.

[0243] In some embodiments, the anesthetic may include lidocaine, proparacaine, or bupivacaine.

[0244] In some embodiments, the active agent can be dexamethasone, ketorolac, diclofenac, vancomycin, moxifloxacin, gatifloxicin, besifloxacin, travoprost, 5-fluorouracil, methotrexate, mitomycin C, prednisolone, bevacizumab (Avastin®), ranibizumab (Lucentis®), sunitinib, pegaptanib (Macugen®), timolol, latanoprost, brimonidine, nepafenac, bromfenac, triamcinolone, difluprednate, fluocinolone acetonide, aflibercept, or a combination thereof. In some embodiments, the agent can be dexamethasone, ketorolac, diclofenac, moxifloxacin, travoprost, 5-fluorouracil, or methotrexate. In some embodiments, the agent is dexamethasone. In some embodiments, the agent is ketorolac. In some embodiments, the agent is travoprost.

[0245] Diagnostic agent can be, for example, imaging agent, marker or visualization agent. Generally, diagnostic agent can be a material for checking health to detect whether its normal function is impaired. In some cases, diagnostic agent can be an agent with functional purpose, such as for detecting eye deformity, illness and pathophysiological aspects. For example, diagnostic agent can be an important and effective diagnostic adjuvant, such as dye (for example, fluorescein dye, indocyanine green, trypan blue, dark quencher such as cyanine dye, azo dye, acridine, fluorene, oxazine, phenanthridine, naphthalimide, rhodamine, benzopyrone, perylene, benzanthrone, p-benzothranolone), to contribute to the visualization of eye tissue. Diagnostic agent can include paramagnetic molecule, fluorescent compound, magnetic molecule, radionuclide, x-ray imaging agent and / or contrast medium. In some embodiments, diagnostic agent can include radiopharmaceutical, contrast agent for imaging technology, allergen extract, activated carbon, different test strips (for example, cholesterol, ethanol and glucose), pregnancy test, 13C urea breath test and various staining agents / markers. In some embodiments, the labeling moiety is a fluorescent dye or dark quencher selected from the group consisting of: coumarin, cyanine dye, azo dye, acridine, fluorene, oxazine, phenanthridine, naphthalimide, rhodamine, benzopyrone, perylene, benzanthrone and benzanthrone. In specific non-limiting embodiments, the fluorescent dye is a residue of a compound selected from the group consisting of: coumarin, fluorescein, cyanine 3 (Cy3), cyanine 5 (Cy5), cyanine 7 (Cy7), Alexa dye, bodipy derivative, (E)-2-(4-(phenyldiazenyl)phenoxy)acetic acid, 3-(3',3'-dimethyl-6-nitrospiro[chromene-2,2'-indoline]-1'-yl)propionate (spiropyran), 3,5-dihydroxybenzoate and (E)-2-(4-(phenyldiazenyl)phenoxy)acetic acid or a combination thereof.

[0246] In certain embodiments of the present invention, the active agent is dispersed, embedded or encapsulated in a covalently cross-linked biodegradable polymer.In certain embodiments, the active agent may be in particulate form.

[0247] In certain embodiments of the present invention, the active agent is a drug in the form of a liquid oil at temperatures up to 37°C, such as travoprost, which forms an organogel with the cross-linked biodegradable polymer of the microparticles, which in vivo comprises the active agent as a liquid within the cross-linked polymer. According to other embodiments of the present invention, the active agent may be oil-soluble and dissolved in a hydrophobic organic liquid or oil, respectively, which forms an organogel with the cross-linked biodegradable polymer of the microparticles. Alternatively, the active agent may be oil-insoluble and may be dispersed in the hydrophobic organic liquid or oil in particulate form, or emulsified in liquid form, which may also form an organogel with the cross-linked biodegradable polymer of the microparticles. In these embodiments, the biodegradable microparticles are formed from an organogel containing the active agent, which is either in a liquid phase or immobilized in the cross-linked particles in a liquid phase.

[0248] In embodiments where the active agent is used in particulate form, the active agent particles can be micronized particles, for example, having a D50 particle size of less than about 15 μm, or less than 10 μm, and / or a D99 particle size of less than about 100 μm, or less than about 50 μm, or a D90 particle size of about 50 μm or less, or 5 μm or less, and / or a D98 particle size of about 10 μm or less. In other embodiments, the active agent particles can be nanoparticles, for example, having a D50 particle size of less than about 100 nm, or less than about 50 nm, and / or a D99 particle size of less than about 50 nm, or a D90 particle size of about 5 nm or less, and / or a D98 particle size of about 10 nm or less. Particle size is determined as disclosed in the "Definitions" section herein.

[0249] Oil / Additives

[0250] In certain embodiments of the present invention, oil is included in the cross-linked polymer to form an organogel, which constitutes the microparticles of these embodiments. These organogel microparticles mostly have a rubbery appearance. Oil, generally a hydrophobic organic liquid, can be used to change the release of the active agent from the microparticle drug delivery system. One or more of its properties, such as hydrophobicity, viscosity, compatibility with the active agent, solubility or insolubility of the active agent in the oil, etc., can be appropriately selected to control the release of the active agent from the organogel microparticles of these embodiments. For example, when the biodegradable microparticles for the sustained release drug delivery system of the embodiments of the present invention are used in a hydrogel or other matrix in the form of an implant inserted into the human body, or directly used in an oral dosage form, the oil can diffuse from the organogel microparticles into the aqueous environment together with the active agent dissolved therein, or diffuse simultaneously with the diffusion of the active agent in the oil. If the active agent is, for example, a water-soluble solid particle dispersed in a hydrophobic organic liquid, the oil can be used to slow down the contact of the aqueous environment with the active agent and delay the leaching of the active agent from the organogel microparticles.

[0251] In certain embodiments, the oil or hydrophobic organic liquid is liquid at human body temperature, such as at a temperature of about 37°C or lower, or in the range of 0°C to 40°C, or 10°C to 38°C, or 15°C to 37°C, or 25°C to 37°C, or at 37°C. The term "liquid" may include viscous fluids having a creamy or waxy but non-solid appearance. In addition, for some hydrophobic organic liquids that undergo hydration in aqueous embodiments (such as body fluids), the melting point of the hydrated material at a certain temperature may be different from that of the non-hydrated material. In certain embodiments of the present invention, the hydrated form of such materials is liquid under those conditions as described above.

[0252] In one embodiment, the active agent is dissolved or dispersed in the oil prior to incorporation into the cross-linked polymer of the microparticles. In another embodiment, the active agent is itself an oil or an oil-like hydrophobic organic liquid, or forms at least a part thereof. An example is travoprost as the active agent.

[0253] In certain embodiments, the oil may include a mixture of oils. The oil may be a biocompatible vegetable oil, synthetic oil or mineral oil, a liquid fatty acid or triglyceride composition, or it may be a biodegradable hydrophobic liquid polymer, or a combination thereof.

[0254] In certain aspects of the present disclosure, the oil is a biocompatible oil, which can be selected from the group comprising: triethyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), alpha-tocopherol (vitamin E), alpha-tocopheryl acetate; plant or vegetable oils such as sesame oil, olive oil, soybean oil, sunflower oil, coconut oil, canola oil, rapeseed oil, nut oils such as hazelnut oil, walnut oil, pecan oil, almond oil, cottonseed oil, corn oil, safflower oil, linseed oil, etc., ethyl oleate, castor oil and its derivatives (Cremophor®); lipids that are liquid at 37° C. or lower, such as saturated or unsaturated fatty acids, monoglycerides, diglycerides, triglycerides (Myglyols®), phospholipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides, biodegradable hydrophobic liquid polymers, low melting point waxes such as vegetable waxes, animal waxes or synthetic waxes, lanolin, jojoba oil, or combinations thereof.

[0255] In certain aspects, the oil is liquid at human body temperature and can have a glass transition temperature and / or melting temperature of 45°C or less, or 37°C or less.

[0256] In certain embodiments, the oil is non-volatile, non-toxic, and / or biocompatible at 37°C and ambient pressure, and / or is capable of being cleared from the implantation site, metabolized, and / or eliminated from the body unchanged.

[0257] Manufacturing method

[0258] Methods for making polymer microparticles are known to those skilled in the art, and these methods can generally be applied and appropriately used in embodiments of the present invention.

[0259] In certain embodiments of the present invention, the method of manufacturing biodegradable microparticles for sustained-release drug delivery involves a method selected from one of the following methods: emulsion solvent evaporation-extraction, emulsion solvent diffusion, supercritical fluid emulsification, coacervation, spray drying, hydrogel templates, use of microfluidic systems, membrane extrusion emulsification, particle replication in non-wetting templates (PRINT) technology, electrohydrodynamic atomization (EHDA) or electrospraying, or a method of obtaining particles from gas-saturated solutions (PGSS), or using 3D printing.

[0260] Lagreca et al., Progress in Biomaterials, Vol. 9, 2020, pp. 153-174, which is incorporated herein by reference, review methods for preparing microparticles made of PLA or PLGA polymers. These methods can primarily be used with other biodegradable polymers and the multi-arm precursors described herein.

[0261] Exemplary preparation methods that may be advantageously employed in embodiments of the present invention are single emulsion techniques and double emulsion techniques.

[0262] A functionalized precursor of a hydrophobic polymer unit (e.g., polylactic acid (PLA), polylactic-co-glycolic acid (PLGA), polyvinylpyrrolidone, or polycaprolactone) and a lipophilic drug are dissolved in an organic non-polar solvent and combined with a cross-linking agent (optionally in a second solution), and the combined solution is added to an aqueous phase comprising a surfactant or emulsifier under agitation, stirring, ultrasonication, or homogenization conditions to form an oil-in-water emulsion. Microparticles form and harden during the removal of the organic solvent, such as by evaporation and cross-linking. Evaporation can be facilitated by continuous stirring or by using a negative pressure solvent extraction system.

[0263] For active agents / drugs that are solid and / or insoluble in organic solvents, a variation of this technique involves dispersing or suspending the active agent / drug in an organic solvent containing a dissolved polymer precursor or crosslinker solution. Optionally, oil can be added, thereby producing organogel microparticles.

[0264] Using double emulsion technology, at least one appropriately functionalized polymer precursor is dissolved in an organic solvent. An aqueous solution containing a water-soluble drug and, optionally, a hydrophilic crosslinker or a second functionalized precursor is added to this organic solvent. The mixture is then emulsified, for example, by sonication, into a water-in-oil emulsion. The resulting emulsion is then added to a larger continuous aqueous phase containing an emulsifier, thereby forming a double emulsion (water-in-oil-in-water). Solidification and crosslinking of the microparticles occur during emulsion formation and subsequent solvent removal.

[0265] More complex techniques, such as microfluidics, which rely on the same basic principles as single or double emulsion techniques and use corresponding microfluidic devices and equipment, are also suitable for making the microparticles of the present invention. The use of a microfluidic focusing device to prepare non-crosslinked monodispersed biodegradable polymer microparticles has been described, for example, in Xu, Q. et al., “Preparation of Monodispersed Biodegradable Polymer Microparticles Using a Microfluidic Flow-Focusing Device for Controlled Drug Delivery”, Small, Vol. 5(13): 1575-1581, 2009. Methods for producing microspheres using microfluidic devices are also described in Duncanson, WJ et al., “Microfluidic Synthesis of Monodisperse Porous Microspheres with Size-tunable Pores”, Soft Matter, Vol. 8, 10636-10640, 2012, and US 8,916,196 B1 describes an apparatus and method for making emulsion-based microparticles that can be used in conjunction with the present invention.

[0266] In generally applicable embodiments, a method of making biodegradable microparticles for sustained-release drug delivery comprises the steps of: (1) forming a gel comprising a covalently cross-linked polymer in the presence of at least one active agent and, optionally, at least one oil and, optionally, a first solvent; (2) making microparticles wherein the at least one active agent is dispersed within the covalently cross-linked polymer; and (3) optionally, removing the solvent.

[0267] When oil is present in step (1), an organogel is formed which comprises the oil in the cross-linked polymer used to form the microparticles. The active agent may be dissolved or dispersed in the oil.

[0268] In one embodiment, the method comprises the following steps: (a) dissolving at least one polymer precursor in a first solvent to produce a first mixture; (b) providing a second mixture comprising a cross-linking agent in a second solvent; (c) adding at least one active agent and optionally an oil to at least one of the first mixture or the second mixture; (d) combining the first mixture with the second mixture to produce a first phase; (e) providing a second phase comprising a third solvent that is immiscible with the first and second solvents; (f) introducing the first phase into the second phase under agitation to thereby produce an emulsion in which the first phase is dispersed in the second phase; and (g) removing the first solvent, the second solvent, and / or the third solvent. Agitation includes stirring, ultrasonication, vortexing, or using a homogenizer known in the art.

[0269] In certain embodiments, the step of making microparticles (step (2)) or step (f) comprises forcing the first phase through a screen, or injecting the first phase into the agitated second phase, wherein the first solvent and / or the second solvent and / or the third solvent optionally contain additives such as emulsifiers, surfactants, dispersing aids or porogens to form microspheres or nanosphere particles.

[0270] In certain embodiments of the method, the first solvent and / or the second solvent is an organic solvent that can dissolve the precursor and the crosslinker, and the second solvent can be the same as the first solvent. The third solvent is a solvent that does not dissolve the precursor, the crosslinker and / or the formed organogel.

[0271] The first solvent and / or the second solvent are selected from acetone, acetonitrile, benzyl alcohol, chloroform, dichloromethane (DCM), dioxane, dimethyl carbonate (DMC), DMSO, ethanol, ethyl acetate, ethyl formate, ethyl propionate, tetraethylene glycol ether, hexafluoroisopropanol, dimethyl isosorbide, isopropanol, chloromethane, dichloromethane, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate or tetrahydrofuran, or any mixture thereof, and the third solvent is water; an alcohol such as methanol, ethanol or propanol; or any mixture thereof.

[0272] The additives can be surfactants or emulsifiers, such as polyvinyl alcohol (PVA), polyethylene glycol dehydrated sorbitan monolaurate (Tween®), dehydrated sorbitan monolaurate (Span®), sodium dodecyl sulfate (SDS), and can be used in the second aqueous phase; and / or porogens, such as inorganic salts (NaCl, KCl, sodium or potassium carbonate or bicarbonate, ammonium bicarbonate), pluronic; sodium oleate or potassium oleate; gelatin; mustard oil, mineral oil; cyclodextrin; carbohydrates, bovine serum albumin (BSA); photoinitiators, free radical polymerization initiators, and combinations thereof.

[0273] According to some embodiments, method steps 1 and 2 utilize oil-in-water emulsion or water-in-oil single or double emulsion technology, or a combination thereof, in particular single or double emulsion technology, or microfluidics technology, or a combination thereof.

[0274] The removal of the first solvent and / or the second solvent and / or the third solvent is performed by one of the following methods: hot air convection or direct drying, indirect or contact drying, spray drying, dielectric drying, vacuum drying, freeze drying, supercritical or superheated steam drying, or a combination of any one thereof.

[0275] In an exemplary embodiment, biodegradable microparticles containing active agents for drug delivery are prepared by an oil-in-water emulsion solvent evaporation / extraction technique. An appropriately functionalized multi-arm precursor (e.g., 4a20kPLGA-NHS) and at least one active agent (e.g., travoprost) as described herein are dissolved in a first solvent, such as dichloromethane (DCM), to prepare a single-phase solution, or a suspension when the agent is in particulate form and insoluble in the solvent, which is the first solution (or suspension). A second solution is prepared containing a small molecule cross-linker or a second functionalized multi-arm precursor in the same or similar miscible solvent. The two solutions are combined and added as a dispersed phase (DP) to a stirred third solution containing an immiscible solvent, referred to as a continuous phase (CP).

[0276] In one embodiment, the present invention provides the hydrophobic polymer precursor of the present invention.For hydrophobic polymer precursor, as PLA or PLGA, the solvent of the first solution and the second solution is non-polar, and the solvent in the 3rd solution is polar and immiscible with the first solvent, and this is just opposite for hydrophilic polymer precursor.The dispersed phase of the first solution and the second solution that merge is added in the 3rd solution that is stirring and can for example be carried out by syringe or syringe pump injection.If hydrophobic precursor and non-polar solvent are used for the dispersed phase that merges, then the 3rd solution can be the aqueous solution of the polyvinyl alcohol (PVA) that for example forms continuous phase (CP).The concentration of this solution can be about 1% (w / w) or any other applicable concentration.PVA mainly serves as emulsifying agent or surfactant, makes the droplet of DP stable, and they are cross-linked and hardened to form microsphere subsequently, also will increase the viscosity of continuous phase simultaneously, thereby helps to form spheroid.

[0277] In certain embodiments, injection occurs before passing through the online homogenizer to disperse the DP into the newly formed microparticles. Adding the dispersed phase to the continuous phase at this introduction stage allows the droplets to have time to disperse before crosslinking and hardening to form an initial emulsion. Then, these newly formed microparticles in the CP stream can flow into the CP (quenching medium) stirred in a jacketed reactor maintained at a controlled temperature. This emulsion is stirred in the quenching medium for a sufficiently long time to extract and evaporate the DCM and harden the microparticles.

[0278] In certain embodiments, the resulting microparticles are filtered, washed, and sieved into appropriately sized fractions, for example, using a vibrating screen agitator. Optionally, the microparticles are dried or lyophilized to remove residual solvent, ultimately yielding dry biodegradable microparticles comprising the covalently crosslinked polymer. Because the crosslinked polymer microparticles of embodiments of the present invention have relatively high thermal stability, the solvent can be advantageously removed by hot air convection or direct drying, indirect or contact drying, spray drying, dielectric drying, vacuum drying, supercritical or superheated steam drying, or a combination of these methods, which can utilize elevated temperatures, thereby avoiding complex and expensive lyophilization steps or freeze drying.

[0279] In one embodiment, when all components are combined in the reaction mixture in step (f), at least one precursor and one small molecule crosslinker, or at least two precursors, will undergo an electrophile-nucleophile reaction to form a covalently crosslinked matrix. If oil is present, organogel microparticles will form. The reaction can be initiated or accelerated by heat, or can occur under ambient conditions.

[0280] In another embodiment, when all components are combined in the reaction mixture in step (f), at least one precursor and one small molecule crosslinker, or at least two precursors, which have been functionalized with polymerizable acryloyl groups, will undergo free radical polymerization, optionally under photoinduction, to form a covalently crosslinked matrix in the form of microparticles. The reaction can be initiated or accelerated by heat, or can occur under ambient conditions. Click chemistry functionalization as described above can also be used.

[0281] The emulsion mixed with the precursor (as formed in step (f)) can be prepared to have a viscosity suitable for introduction through a small-gauge needle using manual force. The diameter of the small-gauge needle is less than the diameter of a 27-gauge (e.g., 28, 29, 30, 31, 32, or 33-gauge) needle, where the specifications specifically refer to the inner diameter and / or outer diameter. Thus, a viscosity between about 1 and about 100,000 mPa∙s can be used; the skilled artisan will immediately understand that all ranges and values ​​within the explicitly specified ranges are contemplated, such as about 10 to about 10,000 mPa∙s, less than about 5 to about 10,000 mPa∙s, less than about 100 or about 500 mPa∙s, or between about 1 and about 100 mPa∙s. The viscosity can be controlled, for example, by selecting appropriate precursors, adjusting solid and / or solvent concentrations, and reaction kinetics. Generally, lower precursor concentrations, increased hydrophilicity, and lower molecular weight favor lower viscosities.

[0282] Release kinetics

[0283] In embodiments of the present invention, the biodegradable microparticles for drug delivery allow the release of active agents in the microparticles to be changed or customized by several measures. For example, the precursor components of the cross-linked polymers that are customized or suitably selected to form the microparticles according to hydrophilic and / or hydrophobic properties will have an impact on the release of the active agent. In addition, if the oil containing the organogel type polymer matrix is ​​used, the diffusion kinetics and the release of the active agent in the microparticle or drug delivery system can be changed or controlled by suitably selecting the oil component according to one or more of the following characteristics: hydrophobicity, viscosity, compatibility with the active agent, solubility or insolubility of the active agent in the oil, etc.

[0284] Therefore, in various embodiments of the present invention, the selection of oil, and / or properties such as the type, composition and hydrophobicity of the polymer network, and / or the L / G ratio in the PLCA can be used to tune the release rate. Each of these individual parameters can be selected individually or in combination with one another to provide controlled release of the active agent.

[0285] In certain embodiments, the biodegradable microparticles and / or drug delivery systems comprising the biodegradable microparticles are formulated so that the active agent is available over an extended period of time, thereby reducing the frequency of administration compared to immediate release dosage forms, such as active agent solutions applied topically to the eye (i.e., eye drops). In certain embodiments, the release of the active agent comprises a constant release of the active agent, a gradually decreasing release of the active agent, and any combination thereof, such as a constant release of the active agent followed by a gradually decreasing release of the active agent. "Sustained release" can be measured in vitro in an aqueous solution under physiological conditions (such as at pH 7.2-7.4 and 37° C.), and is considered to be the same or substantially the same when the drug delivery system is administered to a subject in vivo.

[0286] In various embodiments of the present invention, the release of the active agent follows zero-order release kinetics or substantially zero-order release kinetics, preferably without a "burst" of active agent at the beginning of this period. Burst release refers to the rapid initial release of the active agent from the microparticles within a relatively short time interval after insertion of the implant, for example, within the first day after insertion. According to the present invention, burst release is minimized.

[0287] Certain embodiments of the present invention can cause a therapeutically effective amount of an active agent to be released over a sustained period of time after administration, such as up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month, or up to about 25 days. Other embodiments of the present invention can cause a therapeutically effective amount of an active agent to be released over a sustained period of time after administration, such as up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month, or up to about 25 days. Other embodiments of the present invention can cause a therapeutically effective amount of an active agent to be released over a sustained period of time after administration for up to about 14 days or up to about 21 days, or cause a therapeutically effective amount of an active agent to be released over a sustained period of time after administration for about 6 hours or longer, or for about 12 hours, or 24 hours or longer, or about 48 hours or longer, or about 72 hours or longer, or about 7 days or longer, or about 10 days or longer after administration. All of the above lower and higher time periods in any combination of ranges are encompassed by the present invention.

[0288] In some embodiments of the present invention, crosslinked polymer biodegradable microparticles delay the release of water-soluble active agents or accelerate the release of hydrophobic active agents. In other embodiments of the present invention, crosslinked polymer biodegradable microparticles delay the release of hydrophobic active agents or accelerate the release of water-soluble active agents.

[0289] In one aspect of the present invention, a biodegradable microparticle for sustained drug delivery or a sustained release drug delivery system comprising the biodegradable microparticle is provided, such as a pharmaceutically acceptable implant, for controlled release of an active agent (e.g., total amount) contained therein. Throughout this disclosure, controlled release should be considered as controlled release measured from the time and conditions of the first immersion of the implant in an aqueous solution under physiological conditions such as pH 7.2-7.4 and a temperature of 37°C. Upon exposure to physiological conditions, the cross-linked polymer or organogel in the microparticle or contained in the drug delivery system can slowly release the hydrophobic organic liquid from the organogel while forming a hydrogel.

[0290] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being between 0 and 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being between 0 and 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being at least 2 days.

[0291] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being from 0 to about 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being from 0 to about 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being at least 3 days.

[0292] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being from 0 to about 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being from 0 to about 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being at least 4-7 days.

[0293] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being from 0 to about 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being from 0 to about 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being at least 10-15 days.

[0294] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being from 0 to about 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being from 0 to about 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being at least 10-30 days.

[0295] In certain embodiments, controlled release can be characterized by the amount of active agent released on day 1 being from 0 to about 50% of the total amount of active agent, the amount of active agent released each day from day 2 until the last day of release being from 0 to about 50% of the total amount of active agent, and / or the number of days required for 100% release of the total amount of active agent being greater than 30 days.

[0296] According to certain embodiments of the present invention, the controlled release is characterized in that the amount of active agent released on day 1 is 0 to about 25%, 0 to about 20%, 0 to about 10%, 0 to about 5%, or about 0% of the total amount of active agent, and from day 2 until the last day of release, the amount of active agent released each day is 0 to about 50%, or 0 to about 40%, or 0 to about 30%, or 0 to about 20%, or 0 to about 10%, or 0 to about 5% of the total amount of active agent. In certain embodiments, the number of days required for 100% release of the total amount of active agent is at least 3 days, but no more than 30 days, 25 days, or no more than 16 days. In other embodiments, the time is as disclosed above.

[0297] In one embodiment, the controlled release characterized above comprises zero-order release, such as near zero-order release or substantially zero-order release. In one embodiment, the zero-order release or near zero-order release or substantially zero-order release begins at least 1 day after the pharmaceutically acceptable implant is immersed under physiological conditions (such as pH 7.2-7.4 and 37°C).

[0298] The dosage form or implant showing zero-order release rate will present a relatively straight line in the graphical representation of the percentage of the active agent released versus time. In certain embodiments of the present invention, zero-order release is completed in a complete release period. In certain embodiments of the present invention, zero-order release is completed in a part of the release period. In some such embodiments, zero-order release is completed from the end of the 1st day (that is, 24 hours after the release begins) to the end of release. If less release or incomplete release is completed before the end of the 1st day, this release will be considered to have a lag time of one day or 24 hours. This lag time can also be longer. If high release is completed before the end of the 1st day, this release will be considered to be a burst release during the first day or 24 hours. This burst release time can also be longer. Zero-order release can also be completed in a complete release period. In this context, a complete release period is defined as until 95% of the release is completed.

[0299] Within the meaning of the present invention, zero-order release is defined as being achieved if the release during the corresponding time is proportional to the elapsed time. Proportional to the elapsed time means that the proportional release is calculated over the entire zero-order release time defining a straight line (the release expressed as the cumulative percentage release over the entire time period over which zero-order release is achieved divided by the entire time period defining the straight line), and that the release at any point in time therebetween (i.e., between the start of zero-order release and the end of zero-order release) is within 20% of the cumulative percentage release of the proportional release defined by the straight line.

[0300] Sustained-release drug delivery systems:

[0301] In certain embodiments, a biodegradable sustained release drug delivery system is provided, wherein the drug delivery system comprises the biodegradable microparticles for sustained release drug delivery described herein. In order to provide a drug delivery system, the biodegradable microparticles are incorporated into a hydrogel, a xerogel or an organogel, wherein extrusion or 3D printing is optionally used. In embodiments of the present invention, such a system is used to coat a medical implant. In other embodiments, the drug delivery system is used to manufacture or form a medical implant, wherein the biodegradable microparticles are embedded or dispersed in a hydrogel, a xerogel or an organogel matrix.

[0302] Because biodegradable microparticles are thermostable rubber materials with a melting point higher than the glass transition temperature, unlike conventional non-crosslinked polymer particles, they will not melt, and such medical implants can be molded or implant coatings can be applied using a processing step (e.g., extrusion) involving heat. The method involving a processing step requiring the application of heat can be, for example, an extrusion method (e.g., hot melt extrusion) or injection molding, or a 3D printing method, performed on a reaction mixture comprising biodegradable microparticles dispersed in a hydrogel, xerogel, or organogel, or its precursor. In these methods, gelation occurs before and / or during extrusion or injection molding of a gel-forming material comprising biodegradable microparticles. If extrusion is utilized to manufacture these implants, high-throughput production can be achieved using thermostable biodegradable microspheres.

[0303] In certain embodiments of the present invention, the biodegradable microparticles defined herein are incorporated into (i.e., dispersed or distributed in) a biodegradable hydrogel, organogel, or xerogel. In a specific embodiment, the biodegradable microparticles are uniformly dispersed in the biodegradable polymer. The preparation of a hydrogel matrix suitable for incorporating the biodegradable microparticles of the present invention is described below in the sections "PEG hydrogels" and "Methods for preparing a drug delivery system or implant containing biodegradable microparticles," and the principles described are also applicable to incorporating biodegradable microparticles into hydrogels made from polymers other than PEG, such as the polymers described herein that can be used to prepare the microparticles themselves, as well as the organogel matrix (including oil) used to replace the hydrogel. Because the biodegradable microparticles are thermally stable rubber materials with a melting point above their glass transition temperature, unlike conventional non-crosslinked polymer particles, they will not melt, and processing steps involving heat (e.g., extrusion) can be used to shape such medical implants or apply implant coatings. Methods involving processing steps requiring the application of heat may be, for example, extrusion (e.g., hot melt extrusion) or injection molding of a reaction mixture comprising biodegradable microparticles dispersed in a hydrogel, xerogel, or organogel, or a precursor thereof, or 3D printing methods incorporating the biodegradable microparticles of the present invention.

[0304] PEG hydrogel

[0305] In certain embodiments, the hydrogel comprises a polymer network comprising one or more polyethylene glycol units. In certain embodiments of the present invention, the polymer network forming the hydrogel comprises polyethylene glycol (PEG) units. It is known in the art that PEG forms hydrogels when cross-linked, and these PEG hydrogels are suitable for pharmaceutical applications, for example as a matrix for drugs intended to be administered to all parts of the human or animal body.

[0306] The polymer network of the hydrogel implants of the present invention can comprise one or more multi-arm PEG units having 2 to 10 arms, or 4 to 8 arms, or 4, 5, 6, 7, or 8 arms. In certain embodiments, the PEG units used in the hydrogels of the present invention have 8 arms. In certain specific embodiments, 8-arm PEG is used.

[0307] In certain embodiments, the polyethylene glycol unit is a 4- to 10-arm polyethylene glycol unit, or an 8-arm polyethylene glycol unit.

[0308] The molecular weight of polyethylene glycol refers to the number average molecular weight (Mn). As used herein, a multi-arm PEG unit having a particular molecular weight may be abbreviated as, for example, 8a15kPEG, which refers to an 8-arm PEG having a molecular weight of 15,000 daltons, as described above.

[0309] In a 4-arm PEG, the average arm length (or molecular weight) of each arm can be the total molecular weight of the PEG divided by 4. Thus, a 4a20kPEG precursor, a particularly suitable precursor for use in the present invention, has four arms, each with an average molecular weight of approximately 5,000 Daltons. An 8a20kPEG precursor can also be used in combination with or in place of the 4a20kPEG precursor of the present invention, thus having eight arms, each with an average molecular weight of 2,500 Daltons. Longer arms can provide increased flexibility compared to shorter arms. PEGs with longer arms can swell more than PEGs with shorter arms. PEGs with a lower arm number can also swell more and be more flexible than PEGs with a higher arm number. In certain embodiments, only a 4-arm PEG precursor is used in the present invention. In certain embodiments, two different 4-arm PEG precursors are used in the present invention. In certain other embodiments, a combination of a 4-arm PEG precursor and an 8-arm precursor is used in the present invention. Furthermore, longer PEG arms have a higher melting temperature when dry, thereby providing greater dimensional stability during storage.

[0310] In certain embodiments, the polymer network of the hydrogel that embeds the biodegradable microparticles is formed by reacting a multi-arm polymer precursor containing an electrophilic group with a cross-linking agent containing a nucleophilic group. In certain specific embodiments, the multi-arm polymer precursor is a 4- to 10-arm polyethylene glycol precursor, or an 8-arm polyethylene glycol precursor.

[0311] In certain embodiments, the electrophilic end group used with the PEG precursor to prepare the hydrogels of the present invention is an N-hydroxysuccinimidyl (NHS) ester, including but not limited to NHS dicarboxylates, such as a succinimidyl malonate group, a succinimidyl maleate group, a succinimidyl fumarate group, "SAZ" for a succinimidyl azelate end group, "SAP" for a succinimidyl adipate end group, "SG" for a succinimidyl glutarate end group, and "SS" for a succinimidyl succinate end group.

[0312] In certain embodiments, the multi-arm polymer precursor is selected from the group consisting of 8-arm-15K-SG polyethylene glycol or 8-arm-15K-SAZ polyethylene glycol.

[0313] In certain embodiments, the electrophilic group is selected from the group consisting of a succinimidyl glutarate (SG) group and a succinimidyl azelaate (SAZ) group.

[0314] In certain embodiments of the present invention, the polymer network is formed by reacting a multi-arm polymer precursor containing an electrophilic group with a cross-linking agent containing a nucleophilic group, wherein the electrophilic group is selected from the group consisting of a succinimidyl glutarate (SG) group and a succinimidyl azelaate (SAZ) group, and the multi-arm polymer precursor is selected from the group consisting of 8-arm-15K-SG polyethylene glycol or 8-arm-15K-SAZ polyethylene glycol; and the cross-linking agent containing a nucleophilic group is trilysine, or 8-arm-15K-SAZ polyethylene glycol; and the cross-linking agent containing a nucleophilic group is trilysine, or the polymer network comprises cross-linked 8-arm polyethylene glycol, including groups shown in the following formula:

[0315] ,

[0316] where m is 2 or 6.

[0317] Thus, in certain embodiments, the PEG precursor is an NHS dicarboxylate-terminated multi-arm PEG precursor, which can be represented by the following formula:

[0318]

[0319] Where n is determined by the molecular weight of the corresponding PEG arm, m is an integer from 0 to 10 and specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, and x is the number of arms (and thus can be, for example, 2, 4, 8, etc., see above). When m is 1, each arm is terminated with a succinimidyl succinate (SS) end group; when m is 2, each arm is terminated with a succinimidyl glutarate (SG) group; when m is 3, each arm is terminated with a succinimidyl adipate (SAP) group; and when m is 6, each arm is terminated with a succinimidyl azelaate (SAZ) group. In the presence of these specific electrophilic end groups, the multi-arm PEG unit can be abbreviated, for example, to 4a20kPEG-SAP, which refers to a 4-arm PEG with succinimidyl adipate end groups and a molecular weight of 20,000. In the above formula, R is a core structure suitable for providing the desired number of arms. For 4-arm PEG units and precursors, R can be a pentaerythritol structure, while for 8-arm PEG units and precursors, R can be a hexaglycerol structure.

[0320] In certain embodiments, the multi-arm polymer precursor has a mass average molecular weight in the range of about 10,000 to about 20,000 Daltons. In more specific certain embodiments, the multi-arm polymer precursor has a mass average molecular weight of 15,000 ± 10%.

[0321] In certain embodiments, for example, a cross-linking agent containing a nucleophilic group reacts with a PEG unit containing an electrophilic group, such as an amine-containing cross-linking agent reacts with a PEG unit containing an active ester group to produce multiple PEG units cross-linked by the cross-linking agent via amide groups.

[0322] For PEG with NHS ester end groups, such as succinimidyl azelaate (SAZ)-capped, succinimidyl adipate (SAP)-capped, or succinimidyl glutarate (SG)-capped PEG units (see above), reaction with an amine-containing cross-linker will result in multiple PEG units cross-linked by the cross-linker via a hydrolyzable linker having the formula:

[0323]

[0324] wherein m is an integer from 0 to 10, and specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. For SAZ end groups, m is 6. For SAP end groups, m is 3, while for SG end groups, m is 2, and for SS end groups, m is 1.

[0325] In one embodiment, the cross-linking agent containing a nucleophilic group is an amine. In another embodiment, the cross-linking agent containing a nucleophilic group is a small amine having a molecular weight of less than 1,000 Da and comprising two or more primary aliphatic amine groups. In one embodiment, the cross-linking agent containing a nucleophilic group is a small amine selected from the group consisting of dilysine, trilysine, tetralysine, ethylenediamine, 1,3-diaminopropane, 1,3-diaminopropane, diethylenetriamine, and trimethylhexamethylenediamine. In one embodiment, the cross-linking agent containing a nucleophilic group is trilysine. In a specific embodiment, the cross-linking agent containing a nucleophilic group is trilysine acetate.

[0326] In another embodiment, the trilysine is labeled with a visualization agent selected from the group consisting of a fluorophore, such as fluorescein, rhodamine, coumarin, and cyanine. Specifically, the cross-linking agent containing a nucleophilic group is a fluorescein-conjugated trilysine. More specifically, the fluorescein-conjugated trilysine is obtained by reacting trilysine acetate with N-hydroxysuccinimide (NHS)-fluorescein. Even more specifically, wherein the trilysine is labeled by conjugation with a visualization agent moiety.

[0327] Method for preparing a drug delivery system or implant comprising biodegradable microparticles

[0328] In another aspect, the present invention relates to a method for manufacturing a sustained-release drug delivery system (e.g., an implant) comprising the biodegradable microparticles described herein for sustained drug delivery. The method comprises the following steps:

[0329] a) preparing the biodegradable microparticles described herein for sustained drug delivery,

[0330] b) preparing a precursor mixture comprising a hydrogel, organogel or xerogel precursor and said biodegradable microparticles,

[0331] c) cross-linking the precursor mixture using a cross-linking agent to form a polymer network and obtaining a hydrogel or organogel mixture comprising the polymer network, and

[0332] d) drying the hydrogel or organogel mixture to provide the drug delivery system or implant.

[0333] The component types, component contents and mass ratios described above in connection with the preparation of microparticles and hydrogels are also applicable to the preparation method of the present invention.

[0334] In another aspect, the present invention relates to a sustained-release biodegradable drug delivery system or implant obtainable by the above method.

[0335] Steps b) and c) of the above method can be performed by any suitable mixing and crosslinking method, as further described herein and known, for example, from US 2021 / 0251893A1 or US 2018 / / 085307A1. As is known in the art, the components can be mixed using a syringe, the implant can be extruded as a string or pellet, or directly inserted into the human or animal body. In addition, because the biodegradable microparticles are thermally stable, such medical implants can be formed or implant coatings can be applied using heat-related processing steps (e.g., extrusion).

[0336] Methods involving processing steps requiring the application of heat may be, for example, extrusion (eg, hot melt extrusion) or injection molding of a reaction mixture comprising biodegradable microparticles dispersed in a hydrogel, xerogel, or organogel, or a precursor thereof.

[0337] For example, for acrylate-modified hydrogels or organogel precursors, radiation curing (e.g., UV curing) 3D printing methods can be employed, especially when more complex implant structures are required.

[0338] Application

[0339] The biodegradable sustained-release drug delivery system comprising the biodegradable microparticles can be provided in the form of an implant as described above, such as a medical implant or a pharmaceutically acceptable implant, and can also be provided in the form of an implant coating or an oral dosage form.

[0340] If the biodegradable sustained release drug delivery system comprising biodegradable microparticles is an implant, the implant can be one of the following: an intraocular implant; an intracavitary implant; an intracameral implant; an implant for introduction into the anterior chamber, vitreous, episcleral, posterior subfascial space (inferior fornix), subconjunctival, intracameral, periorbital, retrobulbar, subfascial, retinal, subretinal, intracanalicular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of the cornea or conjunctiva, lacrimal puncta (canaliculus, superior / inferior canaliculus), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, fascia, cornea, cancer tissue, organ, prostate, breast, joint space, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or injury, void space and potential space.

[0341] In certain embodiments of the present invention, the biodegradable microparticles or drug delivery systems comprising the biodegradable microparticles can be formulated for direct or indirect administration by various routes, such as oral administration, parenteral administration, or administration by surgical insertion or injection. Oral dosage forms can be composed of the biodegradable microparticles of the present invention, which can optionally be enteric-coated or filled into capsules. Injectable formulations can be composed of the biodegradable microparticles of the present invention suspended in an injectable liquid, etc.

[0342] Treatment

[0343] According to the present invention, the sustained-release biodegradable microparticles or the biodegradable drug delivery system comprising the biodegradable microparticles are configured for use as a medicament, for example, for treating a disease or medical condition in a patient.

[0344] In one embodiment, a method for treating a disease or medical condition in a patient comprises administering to the patient biodegradable microparticles comprising a therapeutically active agent or administering a hydrogel, organogel, or xerogel comprising the biodegradable microparticles so as to release the active agent over an extended period of time.

[0345] The treatment methods of embodiments of the present invention include incorporating biodegradable microparticles into a hydrogel, organogel, or xerogel, wherein the hydrogel, organogel, or xerogel is formed in situ at the treatment site of the patient to release the active agent over an extended period of time.

[0346] In another embodiment, the treatment method comprises incorporating the biodegradable microparticles into a hydrogel, organogel, or xerogel, wherein the hydrogel, organogel, or xerogel is prefabricated and delivered to or implanted at the treatment site in the patient so as to release the active agent over an extended period of time.

[0347] The treatment site can be one of the following: anterior chamber, vitreous, episcleral, posterior subfascial space (inferior fornix), subconjunctival, intra-anterior chamber, periorbital, retrobulbar, subfascial, retinal, subretinal, intracanalicular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of cornea or conjunctiva, lacrimal puncta (canaliculus, superior / inferior canaliculus), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, fascia, cornea, cancer tissue, organ, prostate, breast, joint space, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or lesion, void space and potential space.

[0348] In an embodiment of the invention, the disease or medical condition to be treated is an eye disease, e.g., a posterior ocular disease, such as any posterior segment eye disease that affects the vasculature and integrity of the retina, macula, or choroid, leading to visual acuity impairment, vision loss, or blindness, particularly posterior segment disease states caused by age, trauma, surgical intervention, such as age-related macular degeneration (AMD), cystoid macular edema (CME), diabetic macular edema (DME), posterior uveitis, and diabetic retinopathy; or glaucoma, intraocular hypertension, hyphema, presbyopia, cataracts, retinal vein occlusion, inflammation.The ocular disease may be selected from the group consisting of retinal neovascularization, choroidal neovascularization, wet AMD, dry AMD, retinal vein occlusion, diabetic macular edema, retinal degeneration, corneal transplant rejection, retinoblastoma, melanoma, glaucoma, autoimmune uveitis, uveitis, proliferative vitreoretinopathy and corneal degeneration, acute and chronic macular neuroretinopathy, central serous chorioretinopathy, macular edema, acute multifocal squamous pigment epitheliopathy, Behcet's disease, disease), shotgun choroidopathy, posterior uveitis, posterior scleritis, creeping choroiditis, subretinal fibrosis, uveitis syndrome, Vogt-Koyanagi-Harada syndrome, retinal artery occlusive disease, central retinal vein occlusion, disseminated intravascular coagulation, branch retinal vein occlusion, fundus hypertension, ocular ischemic syndrome, retinal artery microaneurysms, Coat's disease, juxtafoveal telangiectasia, hemiretinal vein occlusion, papillary phlebitis, carotid artery disease (CAD), frosted branch angiitis, sickle cell retinopathy, angioid streaks, familial exudative vitreoretinopathy, Eales disease disease), proliferative vitreoretinopathy, diabetic retinopathy, tumor-related retinal diseases, congenital hypertrophy of the retinal pigment epithelium (RPE), posterior uveal melanoma, choroidal hemangioma, choroidal osteoma, choroidal metastatic carcinoma, combined hamartoma of the retina and retinal pigment epithelium, retinoblastoma, fundus vascular proliferative tumors, retinal astrocytoma, intraocular lymphoid tumors, myopic retinal degeneration, acute retinal pigment epitheliitis, glaucoma, endophthalmitis, cytomegalovirus retinitis, retinal carcinoma, retinitis pigmentosa, Leber's congenital amaurosis, choroideremia, X-linked retinitis pigmentosa, best vitelliform macular dystrophy, X-linked retinoschisis, achromatopsia CNGA3, achromatopsia CNGB3, LHON, Stargardt disease, Usher syndrome, Norrie disease disease), Bardet-Biedl syndrome, and red-green color blindness.

[0349] The methods described in this subsection can also include administering the biodegradable microparticles, optionally included in a drug delivery system, such as a pharmaceutically acceptable implant, in combination with another agent, also referred to as "combination therapy."

[0350] In one embodiment, the combination therapy comprises administering the biodegradable microparticles and one or more additional agents, optionally contained in a drug delivery system, such as a pharmaceutically acceptable implant, on the same day or on different days. In one embodiment, the additional agent to be administered in the combination therapy may be a liquid formulation of the agent, or it may be contained in an oral dosage form. Thus, the additional agent may be any small molecule, macromolecule, protein, nanoparticle, or any other active agent described herein.

[0351] Treatment methods involving administration of biodegradable microparticles, optionally included in a drug delivery system such as a pharmaceutically acceptable implant, may include any of the following: intravitreal, intracameral, subconjunctival, retrobulbar, subfascial, subretinal, and suprachoroidal injections. Administration may also be topical or oral.

[0352] The active agent or additional agent to be administered in the combination therapy may also be a diagnostic agent. Diagnostic agents are described above and may be substances used to examine the body to detect whether its normal functions are impaired. In some cases, the diagnostic agent may be an agent with a functional purpose, such as for detecting eye malformations, ailments, and pathophysiological aspects.

[0353] Release control method

[0354] In one aspect, the present invention relates to a method for controlling the release of an active agent in a biodegradable sustained-release drug delivery system as previously described herein, the drug delivery system comprising biodegradable microparticles. Controlled release can be achieved by any one or a combination of the following:

[0355] - selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units to adjust the hydrophobicity of the polymer matrix forming the microparticles;

[0356] - selecting the L / G ratio of polylactic-co-glycolic acid (PLGA) units to provide sustained release of the active agent from the microparticles;

[0357] - selecting the molar ratio of the amount of the first crosslinkable precursor to the second crosslinkable precursor so as to adjust the hydrophobicity of the polymer matrix forming the microparticles, thereby modifying the crosslinking density and structure of the polymer matrix;

[0358] - selecting a molar ratio of the amount of the first cross-linkable precursor to the amount of the second cross-linkable precursor to provide a sustained release of the active agent from the microparticles;

[0359] - selection of the amount and / or particle size of the biodegradable microparticles to be included in the hydrogel, organogel, xerogel;

[0360] - adding a third crosslinkable precursor having a lower hydrolyzability than the first crosslinkable precursor and the second crosslinkable precursor, optionally after forming the biodegradable microparticle, modifying the molar ratio of the first precursor, the second precursor and / or the third precursor;

[0361] - Active agents with high water solubility are dispersed in oil in particulate form, using organogels to form biodegradable microparticles.

[0362] In certain embodiments of the present invention, the release of activating agent is mainly controlled by the diffusion of activating agent from cross-linked polymers and / or from the organogel that forms the polymer matrix, hydrophobic liquid (for example oil).The degradation rate of polymer network provides another independent other mechanism for release control.In certain embodiments, oil will delay or accelerate degradation, and it can be used as another method of controlling the release of activating agent.When the activating agent that is dispersed in the oil releases from the organogel together with oil, the release rate of said agent will be substantially affected by the oil diffusion to the influence of the diffusion rate in the surrounding tissue or the body environment or by its decision.In other embodiments, activating agent can be easier than oil from the diffusion of polymer network from the diffusion of oil.

[0363] When in contact with aqueous body fluids, the biodegradable microparticles of the present invention swell due to the absorption of water. The degree of swelling is primarily determined by the gel-forming components used and their hydrophobicity / hydrophilicity. Swelling can increase the length and / or diameter of the organogel according to the present invention by up to about 2000%, up to about 1000%, up to about 100%, up to about 95%, up to about 90%, up to about 80%, up to about 75%, up to about 70%, up to about 60%, up to about 50%, up to about 40%, up to about 30%, up to about 20%, or up to about 10%. In certain embodiments, swelling increases the length and / or diameter of the organogel by a ratio of at least 1.05, 1.1, 1.2, 1.5, or 2, and can be a range having any of the above values.

[0364] However, even after swelling, in certain embodiments, the drug delivery systems containing biodegradable microparticles of the present invention maintain their shape or general shape over an extended period of time due to crosslinking of the polymer components. In certain embodiments, the polymer network of the drug delivery system and / or microparticles is not substantially degraded until all of the active agent has been released, or at least a substantial portion of the active agent, e.g., at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%, or at least about 100% by weight of the active agent has been released.

[0365] For example, over time, water gradually replaces the oil in the organogel microparticles, thereby stably dissolving the hydrophilic active agent that is dispersed but not dissolved in the oil, which can be used to further control the release of the active agent. In this embodiment, the release of the active agent is primarily or entirely a controlled diffusion of the active agent through the oil and polymer into the surrounding tissue. In certain embodiments, when the release rate of the active agent is largely independent of the diffusion rate of the hydrophobic liquid, such as when it is a hydrophilic agent dispersed in oil in the form of solid particles, another factor that influences or determines the release of the active agent dispersed in the oil is the rate at which water diffuses into the organogel particles and / or oil, thereby subsequently dissolving the active agent and eluting it from the organogel into the surrounding aqueous environment.

[0366] Furthermore, in certain embodiments, the slow replacement of oil by water slowly converts the organogel microparticles into hydrogel microparticles, but still cross-linked, thereby maintaining their shape, but after the microparticles or drug delivery system are depleted of the active agent and / or oil, the microparticles can then be more readily (bio)degraded by hydrolysis and / or enzymatic reactions.

[0367] The overall release of the active agent is controlled by at least one or a combination of all of these release mechanisms.

[0368] In embodiments of the present invention involving PLGA units in a cross-linked polymer or organogel matrix, another mechanism can also be utilized to influence or control the release of the active agent. The hydrophobic properties of the covalently cross-linked polymer network in the patient's body can be modified by adjusting the ratio of lactic acid to glycolic acid units. By changing or selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units, the hydrophobicity of the polymer network can be altered. The more hydrophobic lactic acid (L) units will increase the hydrophobicity of the polymer and reduce swelling and water absorption; increasing the content of the relatively more hydrophilic glycolic acid (G) units will reduce the hydrophobicity of the polymer and will increase swelling and water absorption of the polymer.

[0369] In an embodiment of the present invention, by varying and / or selecting the molar ratio of the first crosslinkable precursor to the second crosslinkable precursor, another possibility for adjusting the hydrophobicity of the polymer network is provided. Using a higher amount of a hydrophobic precursor in combination with a more hydrophilic precursor such as a PEG unit, or vice versa, using a higher amount of a more hydrophilic precursor in combination with a hydrophobic precursor, will allow for adjustment of the swelling and release of the hydrophobic liquid and / or active agent.

[0370] Adding a third cross-linkable precursor having a different hydrophobicity than the first and second precursors and varying the molar ratios of these components can further be used to influence swelling and hydrophobic liquid and / or active agent release, as well as diffusion rates of active agent, hydrophobic liquid and / or water.

[0371] Example

[0372] The following examples are included to demonstrate certain aspects and embodiments of the present invention as described in the claims. However, it should be understood by those skilled in the art that the following description is illustrative only and should not be construed as limiting the present invention in any way.

[0373] Materials and abbreviations used in the examples:

[0374] 4a20kPLGA-NHS is a four-arm 20-kilodalton electrophile-functionalized polymer precursor obtained by functionalizing commercially available 4a20kPLGA (with a 50:50 L / G ratio) with N-hydroxysuccinimide (NHS).

[0375] TAEA is tris(2-aminoethyl)amine, commercially available from Sigma-Aldrich / Merck.

[0376] DMC is dimethyl carbonate.

[0377] DCM is dichloromethane.

[0378] PBS is phosphate-buffered saline with physiological salt concentration, pH 7.4.

[0379] 1% PVA aqueous solution was obtained by diluting 4% PVA aqueous solution commercially available from Sigma-Aldrich.

[0380] Example 1

[0381] Thermal stability of cross-linked PLGA microspheres

[0382] Biodegradable microparticles comprising a cross-linked PLGA polymer matrix but without active agents were fabricated using 4a20k-PLGA-NHS as an electrophile-functionalized polymer precursor, TAEA as a small molecule nucleophilic cross-linker, and DCM as a solvent (Sample No. RH-558-1).

[0383] 4a20k-PLGA-NHS (1000 mg) was dissolved in DCM (2 mL) and a portion of the solution was filled into the first syringe. Separately, TAEA (10 mg) was mixed in DCM (2 mL) and the solution was filled into the second syringe. Using a Fibrijet® Y-type mixer ( Figure 2 ) The two solutions were continuously combined and the mixed precursor solution was injected into a 1% PVA aqueous solution (300 mL) under stirring (pitch impeller, 700 rpm) through a 21G needle. The resulting emulsion was stirred overnight, DCM was extracted and evaporated, and the microparticles were hardened. Thereafter, the formed microparticles were removed from the solution and washed with water. The washed microparticles were then sieved into two fractions, i.e., particles with a diameter greater than 106 μm and particles with a diameter of 20-106 μm. The remaining water in the microparticles was removed by lyophilization to obtain dry cross-linked PLGA microparticles.

[0384] Table 1: Composition details of examples of the present invention.

[0385]

[0386] Microparticles with a diameter of >106 μm obtained according to Example 1 were heated on a glass slide at 80° C. for 2 hours. Figure 3 The SEM images of the microparticles showed that the microparticles maintained their shape, indicating that the microparticles did not melt and were thermally stable.

[0387] Example 2

[0388] Biodegradable microparticles containing the organogel and the active agent were fabricated using 4a20k-PLGA-NHS as the electrophile-functionalized polymer precursor, travoprost as the active agent, TAEA as the small molecule nucleophile / cross-linker, and DCM as the solvent (Sample No. RH-558-7).

[0389] 4a20k-PLGA-NHS (500 mg) and travoprost (500 mg) were dissolved in DCM (2.5 mL) and the solution was filled into the first syringe. Separately, TAEA (5 mg) was dissolved in DCM (2.5 mL) and the solution was filled into the second syringe. As in Example 1, a Fibrijet® Y-type mixer ( Figure 2The two solutions were combined continuously and injected through a 21G needle into a 1% PVA aqueous solution (300 mL) under agitation (pitch impeller, 700 rpm). The resulting emulsion was stirred overnight to extract and evaporate the DCM and harden the microparticles. The resulting microparticles were then removed from the solution and washed with water. The washed microparticles were then sieved into two fractions: particles with a diameter >106 μm and particles with a diameter of 20-106 μm. Remaining water in the microparticles was removed by lyophilization to obtain dry, cross-linked PLGA microparticles loaded with travoprost. The travoprost content was determined by extracting the microparticles with acetonitrile and diluting with PBS. The extract was analyzed by UPLC on a Water Acquity system (Waters, USA) equipped with an Acquity BEH C18 column (2.1 mm × 50 mm, 1.7 μm particles). The mobile phase consisted of isopropanol and a 50:50 gradient of 0.1% TFA:acetonitrile. The run time was 5 minutes, with the travoprost peak appearing at 1.4 minutes. UV detection was performed at 220 nm. These results are summarized in Table 2 below.

[0390] Table 2: Composition details of examples of the present invention.

[0391]

[0392] Table 3: Travoprost loading of cross-linked PLGA microparticles of the present invention.

[0393]

[0394] The microparticles obtained according to Example 1 and comparative microparticles made from non-crosslinked PLGA according to a prior art method were heated at 80° C. for 2 hours on a glass slide, respectively. Figure 4 and 5 The SEM images showed that the particles with diameters of 20-106 μm ( Figure 4 ) and particles with a diameter >106 µm ( Figure 5 ) mainly maintained its shape, indicating that the particles did not melt and were thermally stable. Figure 4 and Figure 5 The left image was obtained at room temperature before heating, while the right image was obtained after heat treatment at 80 °C for 2 h.

[0395] Figure 6Images of microparticles from Example 2 (left, colored with purple dye (D&C Violet # 2) for better visualization) and comparative uncrosslinked PLA microparticles prepared as described in Example 1 of US 2018 / 0085307 A1 (right) after heat treatment at 80°C for 2 hours. The thermally stable microparticles from Example 2 maintained their shape, while the comparative PLGA microparticles exhibited a collapsed shape due to melting.

[0396] Example 3

[0397] Effects of heat treatment and particle size on in vitro active agent release

[0398] Accelerated in vitro travoprost release kinetics were measured in 50 mL of modified 1x PBS buffer (including 0.5% PEG40 castor oil and 0.01% NaF) at 40°C for the cross-linked microparticles prepared in this Example 2 without heat treatment and after heat treatment at 80°C for 2 hours, such that 100% release corresponds to 5 to 10 times less than the sink condition. The cross-linked microparticles had the two described particle size fractions (20-106 μm and >106 μm). The in vitro release data are shown in Figure 7 middle.

[0399] from Figure 7 As can be seen in Figure 3, the active agent (travoprost) is released in a constant, slow, sustained manner over an extended period of time, following essentially zero-order kinetics, with little initial burst. Because the polymer microparticles are expected to degrade substantially only after six months, the release kinetics of the active agent are diffusion-controlled. No effect of microparticle degradation was observed.

[0400] Furthermore, smaller microparticles with a diameter of 20-106 µm released travoprost faster than microparticles with a diameter >106 µm. This can be explained by the higher surface area to volume ratio of microparticles with a diameter of 20-106 µm compared to microparticles with a diameter >106 µm, resulting in a higher diffusion rate as diffusion occurs at the surface of the particle.

[0401] Figure 7 It was also shown that the active agent release from the cross-linked PLGA microparticles was not substantially affected by heat treatment at 80°C for 2 hours over a considerable period of time, as the release was similar to that of the corresponding unheated microparticles.

[0402] Example 4

[0403] Comparison with conventional microparticles

[0404] The release of active agent from the cross-linked microparticles with a particle size fraction > 106 μm prepared in this Example 2 was compared to uncross-linked PLA microparticles prepared in the same manner as described in US2018 / 0085307A1, paragraph

[0149] or US2021 / 0251893A1, paragraph

[0501] , and designated 4.5A PLA, 8A PLA, and 10.5A PLA, respectively (A denotes acid-terminated linear PLA, and the polymers have different molecular weights: 4.5A has an intrinsic viscosity of 0.3-0.4 dL / g, 8A has an intrinsic viscosity of 0.7-0.9 dL / g, and 10.5A has an intrinsic viscosity of 1.0-1.1 dL / g (all measured in 0.5% w / v chloroform at 30°C using an Ubbelohde Viscosimeter Model 0). B, the viscometer approximate constant (C) is 0.005 mm² / s², the capillary working length (L) is 40 mm, the balloon volume (V) is 3.0 mL, the capillary inner diameter (d) is 0.46 mm, and the approximate flow time of the solvent (CHCl3) is 78 seconds).

[0405] All microparticles were subjected to accelerated in vitro travoprost release kinetics measurements in 50 mL of modified 1x PBS buffer at 40°C as described in Example 3, such that 100% release corresponds to 5 to 10 times less than sink conditions. Figure 8 middle.

[0406] from Figure 8 As can be seen, the release of travoprost from the non-crosslinked PLA microparticles was significantly faster and less linear compared to the crosslinked PLGA microparticles of Example 2 which had essentially zero order release and did not show any initial burst release, with the 4.5A PLA particles having a larger burst release.

[0407] As a further comparison, Figure 9 The in vitro release profiles of travoprost from different non-crosslinked PLA microparticle blends in modified 1x PBS buffer at 37°C and 40°C are shown as described in Example 3. A clear initial burst of travoprost from the microparticles was observed at both temperatures, with >10% of the travoprost released. In addition, the release of travoprost from the polymer blend microparticles (similar to Figure 1 ) was almost constant at 37°C, whereas the release of travoprost from the mixed non-crosslinked PLA microparticles was not temperature stable, and nonlinear release was observed at 40°C. When compared with the linear zero-order release of the crosslinked PLGA microparticles of the present invention at the same temperature (see Figure 8 ), which demonstrates that the release kinetics will be better controlled by using the cross-linked microparticle drug delivery system according to the embodiments of the present invention.

[0408] The present invention is further described by the following list of items.

[0409] First Project List

[0410] 1. Biodegradable microparticles for sustained-release drug delivery, the biodegradable microparticles comprising an active agent and a three-dimensional covalently cross-linked biodegradable polymer matrix, wherein the cross-linked biodegradable polymer comprises polymer units of at least one of: cross-linked polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), poly(p-dioxanone), poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or a mixture or copolymer of any one thereof.

[0411] 2. The biodegradable microparticle according to item 1, wherein the microparticle is a microsphere having a substantially spherical shape.

[0412] 3. The biodegradable microparticles according to item 1 or 2, wherein the active agent is dispersed, embedded or encapsulated in the cross-linked polymer.

[0413] 4. The biodegradable microparticle according to any one of the preceding items, wherein the cross-linked polymer further comprises at least one oil, and the microparticle consists of an organogel comprising at least one active agent and the at least one oil in the cross-linked polymer.

[0414] 5. The biodegradable microparticle according to any one of the preceding items, wherein the polymer unit further comprises a unit selected from the group consisting of at least one of polyethylene glycol (PEG), polypropylene glycol (PPG), and / or at least one of polyamino acids, glycosaminoglycans, polysaccharides, or proteins, and optionally a copolymer or mixture thereof with any of the polymer units according to item 1.

[0415] 6. The biodegradable microparticle according to item 5, wherein the three-dimensional covalently cross-linked biodegradable polymer comprises a plurality of hydrophobic polymer units and / or hydrophilic polymer units.

[0416] 7. The biodegradable microparticle according to item 6, wherein the hydrophobic polymer unit is selected from at least one of polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA) units, and the hydrophilic polymer unit is selected from at least one of polyethylene glycol units, polypropylene glycol units, or polyglycolic acid (PGA), preferably polyethylene glycol units.

[0417] 8. The biodegradable microparticle according to any one of the preceding items, wherein the three-dimensional covalently cross-linked biodegradable polymer comprises or consists of cross-linked polylactic-co-glycolic acid (PLGA) units.

[0418] 9. The biodegradable microparticle according to claim 8, wherein the polylactic-co-glycolic acid (PLGA) units have an L / G ratio (expressed as % of L or G units) in the range of 0:100 to 100:0, or 1:99 to 99:1, or 10:90 to 90:10, or 25:75 to 75:25, preferably 50:50.

[0419] 10. The biodegradable microparticle of any preceding item, wherein each of the polymer units has an average molecular weight (Mw) ranging from about 1,000 to about 100,000 Daltons, or from about 10,000 to about 60,000 Daltons, or from about 15,000 to about 50,000 Daltons.

[0420] 11. The biodegradable microparticle according to any of the preceding items, wherein the polymer is covalently cross-linked via linkages between polymer units.

[0421] 12. The biodegradable microparticle according to item 11, wherein the linkage is selected from the group consisting of an amine, amide, carbamate, ester, anhydride, ether, acetal, ketal, nitrile, isonitrile, isothiocyanate, isourea, hydrazone, oxime or imine linkage, optionally generated by polycondensation, free radical polymerization or click chemistry reaction, and combinations thereof.

[0422] 13. The biodegradable microparticle according to any one of the preceding items, wherein the active agent is selected from at least one of a therapeutic active agent or a diagnostic active agent, or a combination thereof.

[0423] 14. The biodegradable microparticles according to any one of the preceding items, wherein the therapeutically active agent is selected from steroids; nonsteroidal anti-inflammatory drugs (NSAIDS), such as diclofenac, ibuprofen, meclofenamic acid, mefenamic acid A, salicylate, sulindac, tolmetin, ketoprofen, diflunisal, piroxicam, naproxen, etodolac, flurbiprofen, fenoprofen C, indomethacin, celecoxib, ketorolac, nepafenac; intraocular pressure reducing drugs; antibiotics, such as ciprofloxacin; analgesics, such as bupivacaine; calcium channel blockers, such as nifedipine; cell cycle inhibitors, such as simvastatin; proteins, such as insulin; micromolecules hydrophilic drugs, including carboxylates and amine salts; small molecule hydrophobic drugs, hydrophilic peptides and protein drugs, such as insulin, single-chain antibody fragments, Fab fragments, IgG antibodies, fusion antibodies, etc.; aptamers; in particular bupivacaine (BPV-HCl or base), ropivacaine (RPV), dexamethasone, travoprost, axitinib, non-steroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics, analgesics, calcium channel blockers, cell cycle inhibitors, chemotherapeutic agents, antiviral drugs, anesthetics, hormones, anticancer drugs, antitumor agents, viruses, viruses for gene delivery such as AAV, etc., or any combination thereof.

[0424] 15. The biodegradable microparticles according to any one of the preceding items, wherein the microparticles have a particle size (diameter) of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by sieving, or have an average diameter within the range of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by laser diffraction.

[0425] 16. The biodegradable microparticles according to any of the preceding items, wherein the microparticles have a particle size distribution, for example, as determined by laser diffraction, with a D50 particle size of less than about 100 μm, or less than about 50 μm, or less than about 20 μm, and / or a D90 particle size of less than about 200 μm, or less than about 50 μm, or a D90 particle size of about 100 μm or less, or 30 μm or less, and / or a D90 particle size of about 20 μm or less.

[0426] 17. Biodegradable microparticles according to any of the preceding items, consisting of a blend of microparticles of different particle sizes and / or having different polymer matrices and / or comprising different active agents.

[0427] 18. The biodegradable microparticle according to any one of the preceding items, wherein the cross-linked biodegradable polymer has a glass transition temperature below human body temperature, for example below 37°C, or below 36°C, below 30°C, below 25°C, below 20°C or below 10°C, and / or wherein the polymer has a melting temperature above 40°C, 45°C, 50°C, 60°C or 70°C.

[0428] 19. The biodegradable microparticles according to any of the preceding items, which release a therapeutically or diagnostically effective amount of the active agent over a period of time, for example up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month or up to about 25 days after administration, preferably up to about 14 days or up to about 21 days after administration, wherein optionally, the release of the active agent is substantially constant within a temperature range of 30°C to 45°C or 36°C to about 43°C.

[0429] Second project list

[0430] 1. A biodegradable microparticle for sustained-release drug delivery, the biodegradable microparticle comprising an organogel comprising at least one active agent, at least one oil, and a three-dimensional covalently cross-linked biodegradable polymer matrix, wherein the cross-linked biodegradable polymer comprises polymer units of at least one of polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, a random or block copolymer, or a combination or mixture of any of them, or one or more units of a polyamino acid, a glycosaminoglycan, a polysaccharide, or a protein.

[0431] 2. The biodegradable microparticle according to item 1, wherein the microparticle is a microsphere having a substantially spherical shape.

[0432] 3. The biodegradable microparticles according to item 1 or 2, wherein the active agent is dispersed, embedded or encapsulated in the cross-linked polymer.

[0433] 4. The biodegradable microparticle according to any one of the preceding items, wherein the at least one oil is liquid at human body temperature, for example at about 37°C or lower, or in the range of 0°C to 40°C, or 10°C to 38°C, or 15°C to 37°C, or 25°C to 37°C, or at 37°C.

[0434] 5. The biodegradable microparticle according to any one of the preceding items, wherein the at least one oil is selected from the group consisting of triethyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), α-tocopherol (vitamin E), α-tocopheryl acetate; plant or vegetable oils such as sesame oil, olive oil, soybean oil, sunflower oil, coconut oil, canola oil, rapeseed oil, nut oils such as hazelnut oil, walnut oil, pecan oil, almond oil, cottonseed oil, corn oil, safflower oil, linseed oil, etc., ethyl oleate, castor oil and its derivatives (Cremophor®); lipids that are liquid at 37° C. or lower, such as saturated or unsaturated fatty acids, monoglycerides, diglycerides, triglycerides (Myglyols®), phospholipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides, hydrophobic biodegradable liquid polymers, low melting point waxes such as vegetable waxes, animal waxes or synthetic waxes, lanolin, jojoba oil, or combinations thereof.

[0435] 6. The biodegradable microparticle according to any one of the preceding items, wherein the three-dimensional covalently cross-linked biodegradable polymer comprises a plurality of hydrophobic polymer units and / or hydrophilic polymer units.

[0436] 7. The biodegradable microparticle according to item 6, wherein the hydrophobic polymer unit is selected from at least one of polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA) units, and the hydrophilic polymer unit is selected from at least one of polyethylene glycol units, polypropylene glycol units, or polyglycolic acid (PGA), preferably polyethylene glycol units.

[0437] 8. The biodegradable microparticle according to any one of the preceding items, wherein the three-dimensional covalently cross-linked biodegradable polymer comprises or consists of cross-linked polylactic-co-glycolic acid (PLGA) units.

[0438] 9. The biodegradable microparticle according to claim 8, wherein the polylactic-co-glycolic acid (PLGA) units have an L / G ratio (expressed as % of L or G units) in the range of 0:100 to 100:0, or 1:99 to 99:1, or 10:90 to 90:10, or 25:75 to 75:25, preferably 50:50.

[0439] 10. The biodegradable microparticle of any preceding item, wherein each of the polymer units has an average molecular weight (Mw) ranging from about 1,000 to about 100,000 Daltons, or from about 10,000 to about 60,000 Daltons, or from about 15,000 to about 50,000 Daltons.

[0440] 11. The biodegradable microparticle according to any of the preceding items, wherein the polymer is covalently cross-linked via linkages between polymer units.

[0441] 12. The biodegradable microparticle according to item 11, wherein the linkage is selected from the group consisting of an amine, amide, carbamate, ester, anhydride, ether, acetal, ketal, nitrile, isonitrile, isothiocyanate, isourea, hydrazone, oxime or imine linkage, optionally generated by polycondensation, free radical polymerization or click chemistry reaction, and combinations thereof.

[0442] 13. The biodegradable microparticle according to any one of the preceding items, wherein the active agent is selected from at least one of a therapeutic active agent or a diagnostic active agent, or a combination thereof.

[0443] 14. The biodegradable microparticles according to any one of the preceding items, wherein the therapeutically active agent is selected from steroids; nonsteroidal anti-inflammatory drugs (NSAIDS), such as diclofenac, ibuprofen, meclofenamic acid, mefenamic acid A, salicylate, sulindac, tolmetin, ketoprofen, diflunisal, piroxicam, naproxen, etodolac, flurbiprofen, fenoprofen C, indomethacin, celecoxib, ketorolac, nepafenac; intraocular pressure reducing drugs; antibiotics, such as ciprofloxacin; analgesics, such as bupivacaine; calcium channel blockers, such as nifedipine; cell cycle inhibitors, such as simvastatin; proteins, such as insulin; micromolecules hydrophilic drugs, including carboxylates and amine salts; small molecule hydrophobic drugs, hydrophilic peptides and protein drugs, such as insulin, single-chain antibody fragments, Fab fragments, IgG antibodies, fusion antibodies, etc.; aptamers; in particular bupivacaine (BPV-HCl or base), ropivacaine (RPV), dexamethasone, travoprost, axitinib, non-steroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics, analgesics, calcium channel blockers, cell cycle inhibitors, chemotherapeutic agents, antiviral drugs, anesthetics, hormones, anticancer drugs, antitumor agents, viruses, viruses for gene delivery such as AAV, etc., or any combination thereof.

[0444] 15. The biodegradable microparticles according to any one of the preceding items, wherein the microparticles have a particle size (diameter) of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by sieving, or have an average diameter within the range of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by laser diffraction.

[0445] 16. The biodegradable microparticles according to any of the preceding items, wherein the microparticles have a particle size distribution, for example, as determined by laser diffraction, with a D50 particle size of less than about 100 μm, or less than about 50 μm, or less than about 20 μm, and / or a D90 particle size of less than about 200 μm, or less than about 50 μm, or a D90 particle size of about 100 μm or less, or 30 μm or less, and / or a D90 particle size of about 20 μm or less.

[0446] 17. Biodegradable microparticles according to any of the preceding items, consisting of a blend of microparticles of different particle sizes and / or having different polymer matrices and / or comprising different active agents.

[0447] 18. The biodegradable microparticle according to any one of the preceding items, wherein the cross-linked biodegradable polymer or organogel has a glass transition temperature below human body temperature, for example below 37°C, or below 36°C, below 30°C, below 25°C, below 20°C or below 10°C, and / or wherein the polymer has a melting temperature above 40°C, 45°C, 50°C, 60°C or 70°C.

[0448] 19. The biodegradable microparticles according to any of the preceding items, which release a therapeutically or diagnostically effective amount of the active agent over a period of time, for example up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month or up to about 25 days after administration, preferably up to about 14 days or up to about 21 days after administration, wherein optionally, the release of the active agent is substantially constant within a temperature range of 30°C to 45°C or 36°C to about 43°C.

[0449] Third project list

[0450] 1. Biodegradable microparticles for sustained-release drug delivery, comprising an active agent and a three-dimensional covalently cross-linked biodegradable polymer matrix, wherein at least one of the following conditions is achieved:

[0451] - the cross-linked biodegradable polymer comprises at least one of the following: cross-linked polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), poly(p-dioxanone), poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or a copolymer of any one of them;

[0452] - The biodegradable microparticles comprise an organogel comprising the covalently cross-linked biodegradable polymer and an oil.

[0453] 2. The biodegradable microparticle according to item 1, wherein the microparticle is a microsphere having a substantially spherical shape.

[0454] 3. The biodegradable microparticle according to item 1 or 2, wherein the active agent is dispersed, embedded or encapsulated in the organogel.

[0455] 4. The biodegradable microparticle according to any one of the preceding items, wherein the organogel is formed by chemically crosslinking at least one multifunctional precursor, optionally in the presence of an oil, to form the three-dimensional covalently crosslinked polymer matrix.

[0456] 5. The biodegradable microparticle according to item 4, wherein the at least one precursor has a functionality greater than 2, such as 3 to 10, or 3 to 9, or 4 to 8, or 4 for chemical cross-linking.

[0457] 6. The biodegradable microparticle according to any one of items 4 or 5, wherein the at least one precursor is a dendrimer or a multi-arm precursor having a core and 2 to 10 arms, or 3 to 10 arms, 4 to 8 arms, or 4 or 6 arms, each arm comprising a polymer unit and having a terminus.

[0458] 7. The biodegradable microparticle according to any one of items 4 to 6, wherein the polymer unit is selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone, a random or block copolymer, or a combination or mixture of any one thereof, or one or more of the following units: polyamino acids, glycosaminoglycans, polysaccharides or proteins.

[0459] 8. The biodegradable microparticle according to any one of items 4 to 7, wherein the polymer units in each arm of the multi-arm precursor are the same or different types of polymer units.

[0460] 9. The biodegradable microparticle according to any one of items 4 to 8, further comprising at least one cross-linking agent having at least two functional groups or more than two functional groups, preferably a small molecule amine, such as tris(2-aminoethyl)amine (TAEA) or trilysine.

[0461] 10. The biodegradable microparticle according to any one of items 4 to 8, wherein the organogel comprises at least two cross-linkable dendrimers or multi-arm precursors that are cross-linked to each other.

[0462] 11. The biodegradable microparticle according to any one of items 4 to 10, wherein the dendrimer or multi-arm precursor comprises a functional group on the end of at least three arms or on each end thereof.

[0463] 12. The biodegradable microparticle according to any one of items 4 to 11, wherein the polymer matrix is ​​formed by a first multi-armed precursor comprising a first functional group and a second multi-armed precursor or a cross-linking agent comprising a second functional group, wherein the functional group is located at the end of each arm of the precursor or the cross-linking agent, wherein the first functional group or the second functional group can be directly grafted to the end of the precursor or grafted to the end of the precursor through a linker molecule.

[0464] 13. The biodegradable microparticle according to item 12, wherein the first functional group and the second functional group are each selected from the group consisting of electrophiles and nucleophiles; functional groups for click chemistry; functional groups for cycloaddition reactions, in particular 1,3 dipolar cycloaddition reactions and hetero-Diels-Alder cycloaddition reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; polymerizable vinyl groups, or combinations thereof.

[0465] 14. The biodegradable microparticle according to item 13, wherein the first functional group and the second functional group are each selected from an electrophile and a nucleophile, and the reaction between the first functional group and the second functional group is an electrophile-nucleophile reaction to form a covalent bond.

[0466] 15. The biodegradable microparticle according to item 14, wherein the nucleophile is selected from one of the following: an amine, such as a primary amine; a hydroxyl group; an alcohol; a thiol; an azide anion; and a carboxyl group.

[0467] 16. The biodegradable microparticle according to item 14 or 15, wherein the electrophile is selected from active ester groups such as succinimidyl ester, succinimidyl carbonate, nitrophenyl carbonate, aldehyde, ketone, acrylate, acrylamide, maleimide, vinyl sulfone, iodoacetamide, olefin, alkyne, azide, norbornene, epoxide, mesylate, tosylate, trifluoroethanesulfonyl, cyanurate, o-pyridyl disulfide or halogen.

[0468] 17. The biodegradable microparticle according to any one of items 14 to 16, wherein the nucleophile is an amine group, in particular a primary amine, and the electrophile is an active ester group, in particular a succinimidyl ester selected from the group consisting of succinimidyl succinate, succinimidyl glutarate, succinimidyl adipate, succinimidyl azelate or succinimidyl glutaramide.

[0469] 18. The biodegradable microparticle according to item 13, wherein the first functional group and the second functional group are each selected from functional groups for click chemistry, in particular functional groups for cycloaddition reactions, in particular 1,3 dipolar cycloaddition reactions, [3+2] cycloaddition reactions such as olefin-nitrone cycloaddition reactions or alkyne-nitrone cycloaddition reactions, [4+2] cycloaddition reactions, hetero Diels-Alder cycloaddition reactions; functional groups for thiol-ene reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol type carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; and functional groups for Michael type addition reactions.

[0470] 19. The biodegradable microparticle according to claim 18, wherein the first functional group is an alkyne compound, such as dibenzocyclooctyne (DBCO) or bicyclo[6.1.0]-nonyne (BCN); or norbornene or trans-cyclooctene (TCO), and the second functional group is azide, 3,4-dihydroxyphenylacetic acid (DHPA) or tetrazine (Tz).

[0471] 20. The biodegradable microparticle according to claim 19, wherein the DBCO, BCN, norbornene, TCO, azide, DHPA and Tz functional groups are grafted to the ends of the multi-arm precursor via a linker, such as an acid group, a diacid group, a functionalized aliphatic group, a heteroaliphatic group, or an aromatic group or a heteroaromatic group.

[0472] 21. The biodegradable microparticle according to claim 13, wherein the first functional group and the second functional group are selected for a [3+2] cycloaddition reaction, such as an alkene-nitrone cycloaddition reaction or an alkyne-nitrone cycloaddition reaction, or wherein the first functional group and the second functional group are selected for a [4+2] cycloaddition reaction, in particular a hetero-Dickens-Alder reaction, wherein the first functional group is an aldehyde or an imine compound, and the second functional group is a 1,3 diene compound, an unsaturated carbonyl compound or a nitroso-alkene compound.

[0473] 22. The biodegradable microparticle according to claim 13, wherein the first functional group and the second functional group are selected for a thiol-ene reaction, wherein the first functional group is a thiol compound and the second functional group is an olefin, preferably a terminal olefin, or wherein the first functional group and the second functional group are selected for a nucleophilic ring opening, wherein the first functional group is selected from an epoxide, a thiirane, an aziridine or a lactam, and the second functional group is a nucleophile.

[0474] 23. The biodegradable microparticle of claim 13, wherein the first functional group and the second functional group are selected for a non-aldol type carbonyl reaction, wherein the first functional group is an aldehyde or ketone compound and the second functional group is a primary amine, hydrazine, hydrazide or aminooxy compound for forming an imine, amide, isourea, hydrazone, acylhydrazone or oxime linkage.

[0475] 24. The biodegradable microparticle according to item 13, wherein the first functional group and the second functional group are each selected from polymerizable vinyl groups and acrylates, such as (meth)acrylic acid, (meth)acrylates, acrylamide, fumaric acid, maleic acid and combinations thereof, wherein crosslinking is induced thermally or photochemically, optionally using an initiator, such as a photoinitiator, such as a free radical photoinitiator (Norish I type, such as 2,2-dimethoxy-1,2-diphenyl-ethan-1-one, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxy-cyclohexylphenyl ketone; or Norish II type, such as benzophenone and its derivatives and isopropylthioxanthone in combination with a synergist such as the tertiary amines 2-ethylhexyl-(4-N,N-dimethylamino)benzoate and 2-ethyl-(4-N,N-dimethylamino)benzoate); or a cationic photoinitiator.

[0476] Fourth Project List

[0477] 1. A method for producing biodegradable microparticles for sustained-release drug delivery according to any one of the first to third lists, the method being selected from one of the following techniques: emulsion solvent evaporation-extraction, emulsion solvent diffusion, supercritical fluid emulsification, coacervation, spray drying, hydrogel templates, microfluidic systems, membrane extrusion emulsification, particle replication in non-wetting templates (PRINT) technology, electrohydrodynamic atomization (EHDA) or electrospraying, or particles from gas saturated solution (PGSS) method, or utilizing 3D printing.

[0478] 2. The method according to item 1, comprising the following steps:

[0479] (1) forming a gel comprising covalently cross-linked polymers in the presence of at least one active agent, optionally at least one oil, and optionally a first solvent,

[0480] (2) producing microparticles wherein the at least one active agent is dispersed in the covalently cross-linked polymer, and

[0481] (3) Optionally, removing the solvent.

[0482] 3. The method according to item 2, further comprising the following steps:

[0483] (a) dissolving at least one polymer precursor in a first solvent to obtain a first mixture;

[0484] (b) providing a second mixture comprising a cross-linking agent in a second solvent;

[0485] (c) adding at least one active agent and optionally oil to at least one of the first mixture or the second mixture;

[0486] (d) combining the first mixture with the second mixture to produce a first phase;

[0487] (e) providing a second phase comprising a third solvent that is immiscible with the first solvent and the second solvent;

[0488] (f) introducing the first phase into the second phase under agitation, thereby producing an emulsion in which the first phase is dispersed in the second phase; and

[0489] (g) removing the first solvent, the second solvent and / or the third solvent.

[0490] 4. A method as described in item 2 or 3, wherein the step of producing microparticles (step (2)) or the step f) comprises forcing the first phase through a screen, or injecting the first phase into the agitated second phase, and the first solvent and / or the second solvent and / or the third solvent optionally contain additives such as emulsifiers, surfactants, dispersing aids or porogens to form microspheres or nanosphere particles.

[0491] 5. The method of any one of items 2 to 4, wherein the first solvent and / or the second solvent is an organic solvent in which the precursor is soluble, and the third solvent is a solvent in which the first phase and / or the organogel formed thereof is insoluble.

[0492] 6. A method as described in item 5, wherein the first solvent or the second solvent is selected from acetone, acetonitrile, benzyl alcohol, chloroform, dichloromethane (DCM), dioxane, dimethyl carbonate, DMSO, ethanol, ethyl acetate, ethyl formate, ethyl propionate, tetraethylene glycol ether, hexafluoroisopropanol, isosorbide dimethyl ether, isopropanol, chloromethane, dichloromethane, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate or tetrahydrofuran, or any mixture thereof, and the third solvent is water; an alcohol such as methanol, ethanol or propanol; or any mixture thereof.

[0493] 7. The method of any one of items 4 to 6, wherein the additive is selected from surfactants or emulsifiers, such as polyvinyl alcohol (PVA), polyethylene glycol sorbitan monolaurate (Tween®), sorbitan monolaurate (Span®), sodium dodecyl sulfate (SDS); and / or porogens, such as inorganic salts (NaCl, KCl, sodium or potassium carbonates or bicarbonates, ammonium bicarbonate), pluronic; sodium oleate or potassium oleate; gelatin; mustard oil, mineral oil; cyclodextrins; carbohydrates, bovine serum albumin (BSA); photoinitiators, free radical polymerization initiators, and combinations thereof.

[0494] 8. The method according to any one of items 2 to 7, wherein steps 1 and 2 utilize water-in-oil emulsion or oil-in-water emulsion technology, or a combination thereof, in particular single emulsion or double emulsion technology, or microfluidics technology, or a combination thereof.

[0495] 9. A method as described in any one of items 2 to 8, wherein the removal of the first solvent and / or the second solvent and / or the third solvent is carried out by one of the following methods: hot air convection or direct drying, indirect or contact drying, spray drying, dielectric drying, vacuum drying, freeze drying, supercritical or superheated steam drying, or a combination of any one thereof.

[0496] 10. A biodegradable microparticle for sustained drug delivery, wherein the biodegradable microparticle is obtainable by the method according to any one of the preceding items.

[0497] Fifth Project List

[0498] 1. A biodegradable sustained-release drug delivery system comprising the biodegradable microparticles for sustained-release drug delivery according to any one of the first to third lists above.

[0499] 2. The drug delivery system of claim 1, wherein the biodegradable microparticles are incorporated into a hydrogel, xerogel or organogel.

[0500] 3. The drug delivery system of item 1 or 2, which is used for coating a medical implant or as a medical implant.

[0501] 4. A medical implant for sustained drug delivery, comprising the biodegradable microparticles for sustained-release drug delivery according to any one of the first to third lists above.

[0502] 5. A drug delivery system or implant as described in any one of items 1 to 4, wherein the system or implant is selected from the group consisting of: an intraocular implant; an intracavitary implant; an intracameral implant; an implant for introduction into the anterior chamber, vitreous, extrascleral, posterior subfascial space (inferior fornix), subconjunctival, intracameral, periorbital, retrobulbar, subfascial, retinal, subretinal, intratubular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of the cornea or conjunctiva, punctum (tubule, superior / inferior fornix), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, Tenon's fascia, cornea, cancer tissue, organ, prostate, breast, joint space, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or injury, void space and potential space.

[0503] 6. The drug delivery system or implant according to any one of items 1 to 4, wherein the system or implant is obtained by extrusion or injection molding of a reaction mixture comprising the biodegradable microparticles dispersed in a hydrogel, xerogel or organogel or a precursor thereof.

[0504] 7. The drug delivery system or implant according to item 6, wherein gelation occurs before and / or during extrusion or injection molding of the gel-forming material comprising the biodegradable microparticles.

[0505] 8. The drug delivery system or implant of any one of items 2 to 7, wherein the content of the biodegradable microparticles embedded in the hydrogel, organogel or xerogel is from about 10 wt % to about 35 wt %, or from about 23 wt % to about 27 wt %, or from about 12 wt % to about 17 wt %, or from about 30 wt % to about 35 wt %, or about 25 wt %, or about 15 wt %, or about 34 wt %, relative to the total weight of the drug delivery system or implant.

[0506] 9. A drug delivery system or implant as described in any of the preceding items, which provides for release of a therapeutically or diagnostically effective amount of the active agent over a period of time, such as up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month, or up to about 25 days after administration, preferably up to about 14 days or up to about 21 days after administration, wherein optionally, the release of the active agent is substantially constant within a temperature range of 30°C to 45°C or 36°C to 43°C.

[0507] 10. The biodegradable sustained-release drug delivery system or implant according to any one of items 1 to 8, for use as a medicament.

[0508] 11. A biodegradable sustained-release drug delivery system or implant as described in any one of items 1 to 8 for treating a disease / medical condition in a patient, said use comprising incorporating the biodegradable microparticles according to any one of the first to third lists above into a carrier, such as a hydrogel, organogel or xerogel, wherein the hydrogel, organogel or xerogel is formed in situ at the treatment site of the patient, or is pre-manufactured and delivered or implanted at the treatment site of the patient, so as to release the active agent from the microparticles over an extended period of time, or the carrier is a solvent or solvent system for producing an injectable suspension or dispersion.

[0509] 12. A method for treating a disease / medical condition in a patient, the method comprising incorporating the biodegradable microparticles according to any one of the first to third lists above into a hydrogel, organogel or xerogel, wherein the hydrogel, organogel or xerogel is formed in situ at the treatment site in the patient, or is pre-manufactured and delivered or implanted at the treatment site in the patient, so as to release the active agent over an extended period of time.

[0510] 13. A method for treating a disease / medical condition in a patient, the method comprising administering to the patient a hydrogel, organogel or xerogel comprising biodegradable microparticles according to any one of the first to third lists above, so as to release the active agent over an extended period of time.

[0511] 14. The system for use or method of any one of items 9 to 12, wherein the treatment site is selected from the group consisting of anterior chamber, vitreous, episcleral, posterior subfascial space (inferior fornix), subconjunctival, intra-anterior chamber, periorbital, retrobulbar, subfascial, retinal, subretinal, intracanalicular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of cornea or conjunctiva, lacrimal puncta (canaliculus, superior / inferior canaliculus), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, fascia, cornea, cancer tissue, organ, prostate, breast, joint, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or injury, void space, and potential space.

[0512] 15. The system for use or method of treatment according to any one of items 9 to 13, wherein the disease / medical condition to be treated is an eye disease, such as a posterior ocular disease, such as any posterior segment disease affecting the vasculature and integrity of the retina, macula or choroid, leading to visual acuity impairment, vision loss or blindness, in particular posterior segment disease states caused by age, trauma, surgical intervention, such as age-related macular degeneration (AMD), cystoid macular edema (CME), diabetic macular edema (DME), posterior uveitis and diabetic retinopathy; or glaucoma, intraocular hypertension, hyphema, presbyopia, cataract, retinal vein occlusion, inflammation.

[0513] Sixth Project List

[0514] 1. A method of controlling the release of an active agent from biodegradable microparticles for sustained drug delivery according to the first to third lists above, the method comprising one or a combination of the following measures:

[0515] - selecting / adjusting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units to adjust the hydrophobicity of the polymer matrix forming the microparticles;

[0516] - selecting / adjusting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units to provide sustained release of the active agent from the microparticles;

[0517] - selecting / adjusting the molar ratio of the amount of the first crosslinkable precursor to the second crosslinkable precursor in order to adjust the hydrophobicity of the polymer matrix forming the microparticles;

[0518] - selecting / adjusting the molar ratio of the amount of the first cross-linkable precursor to the second cross-linkable precursor to provide a sustained release of the active agent from the microparticles;

[0519] - adding a third crosslinkable precursor having a lower hydrolyzability than the first crosslinkable precursor and the second crosslinkable precursor, optionally after forming the biodegradable microparticle, modifying the molar ratio of the first precursor, the second precursor and / or the third precursor;

[0520] - dispersing the active agent with high water solubility in particulate form into the organogel of biodegradable microparticles;

[0521] - Select / adjust the amount and type of oil in the organogel microparticles;

[0522] - selecting / adjusting the amount and / or particle size of said biodegradable microparticles included in said hydrogel, organogel, xerogel.

Claims

1. A biodegradable microparticle for sustained-release drug delivery, comprising an active agent and a three-dimensionally covalently cross-linked biodegradable polymer, wherein at least one of the following conditions is achieved: - the cross-linked biodegradable polymer comprises at least one of the following: cross-linked polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), poly(vinyl pyrrolidone), poly(p-dioxanone), poly(trimethylene carbonate), polycaprolactone and / or polyvinyl alcohol, or a copolymer of any one of them; - The biodegradable microparticles include an organogel comprising the cross-linked biodegradable polymer and an oil.

2. The biodegradable microparticles of claim 1, wherein the microparticles are microspheres having a substantially spherical shape.

3. The biodegradable microparticle according to claim 1 or 2, wherein the active agent is dispersed, embedded or encapsulated in the polymer or organogel.

4. The biodegradable microparticle according to any one of the preceding claims, wherein the organogel or cross-linked polymer is formed by chemically cross-linking at least one multifunctional precursor, optionally in the presence of an oil, to form the three-dimensional covalently cross-linked polymer matrix.

5. The biodegradable microparticle of claim 4, wherein the at least one precursor has a functionality greater than 2, such as 3 to 10, or 3 to 9, or 4 to 8, or 4 for chemical cross-linking.

6. The biodegradable microparticle according to any one of claims 4 or 5, wherein the at least one precursor is a dendrimer or a multi-armed precursor having a core and 2 to 10 arms, or 3 to 10 arms, 4 to 8 arms, or 4 or 6 arms, each arm comprising a polymer unit and having a terminus.

7. The biodegradable microparticle according to any one of claims 4 to 6, wherein the polymer unit is selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polyvinyl alcohol, poly(vinyl pyrrolidone), polylactic acid (PLA), polyglycolic acid (PGA), polylactic-co-glycolic acid (PLGA), polydioxanone, poly(trimethylene carbonate), polycaprolactone, a random or block copolymer, or a combination or mixture of any one thereof, or one or more of the following units: polyamino acids, glycosaminoglycans, polysaccharides or proteins.

8. The biodegradable microparticle according to any one of claims 4 to 7, wherein the polymer units in each arm of the multi-arm precursor are the same or different types of polymer units.

9. The biodegradable microparticle according to any one of claims 4 to 8, wherein the three-dimensional covalently cross-linked biodegradable polymer matrix comprises a plurality of hydrophobic polymer units and / or hydrophilic polymer units.

10. The biodegradable microparticle according to claim 9, wherein the hydrophobic polymer unit is selected from at least one of polylactic acid (PLA) and polylactic-co-glycolic acid (PLGA) units, preferably polylactic acid (PLA). The biodegradable microparticle according to claim 9 , wherein the hydrophilic polymer unit is selected from at least one of a polyethylene glycol unit, a polypropylene glycol unit, and polyglycolic acid (PGA), preferably a polyethylene glycol unit.

12. The biodegradable microparticle according to any one of claims 1 to 8, wherein the three-dimensional covalently cross-linked polymer comprises or consists of polylactic-co-glycolic acid (PLGA) units or polylactic acid (PLA).

13. The biodegradable microparticle of any one of claims 4 to 12, wherein the polymer units each have an average molecular weight (Mw) ranging from about 1,000 to about 100,000 Daltons, or from about 10,000 to about 60,000 Daltons, or from about 15,000 to about 50,000 Daltons.

14. The biodegradable microparticle according to claim 11 or 12, wherein the polylactic-co-glycolic acid (PLGA) units have an L / G ratio (expressed as % of L or G units) in the range of 0:100 to 100:0, or 1:99 to 99:1, or 10:90 to 90:10, or 25:75 to 75:25, preferably 50:

50.

15. The biodegradable microparticle according to any one of claims 4 to 14, further comprising at least one cross-linking agent having at least two functional groups or more than two functional groups, preferably a small molecule amine, such as tris(2-aminoethyl)amine (TAEA) or trilysine.

16. The biodegradable microparticle according to any one of claims 4 to 14, wherein the organogel comprises at least two cross-linkable dendrimers or multi-arm precursors cross-linked to each other.

17. The biodegradable microparticle according to any one of claims 4 to 16, wherein the dendrimer or multi-arm precursor comprises a functional group at the end of at least three arms or at each end thereof.

18. The biodegradable microparticle according to any one of claims 15 to 17, wherein the polymer matrix is ​​formed by a first multi-arm precursor comprising a first functional group and a second multi-arm precursor or a cross-linking agent comprising a second functional group, wherein the functional group is located at the end of each arm of the precursor or the cross-linking agent, wherein the first functional group or the second functional group can be directly grafted to the end of the precursor or grafted to the end of the precursor through a linker molecule.

19. The biodegradable microparticle according to claim 18, wherein the first functional group and the second functional group are each selected from the group consisting of an electrophile and a nucleophile; a functional group for click chemistry; a functional group for cycloaddition reaction, in particular a 1,3 dipolar cycloaddition reaction or a hetero-Diels-Alder cycloaddition reaction; a functional group for nucleophilic ring opening; a functional group for non-aldol carbonyl reaction; a functional group for addition reaction with a carbon-carbon multiple bond; a polymerizable vinyl group, or a combination thereof.

20. The biodegradable microparticle of claim 19, wherein the first functional group and the second functional group are each selected from an electrophile and a nucleophile, and the reaction between the first functional group and the second functional group is an electrophile-nucleophile reaction to form a covalent bond.

21. The biodegradable microparticle of claim 20, wherein the nucleophile is selected from one of the following: an amine, such as a primary amine; a hydroxyl group; an alcohol; a thiol; an azide anion; and a carboxyl group.

22. The biodegradable microparticle according to claim 20 or 21, wherein the electrophile is selected from active ester groups such as succinimidyl ester, succinimidyl carbonate, nitrophenyl carbonate, aldehyde, ketone, acrylate, acrylamide, maleimide, vinyl sulfone, iodoacetamide, olefin, alkyne, azide, norbornene, epoxide, mesylate, tosylate, triflate, cyanurate, o-pyridyl disulfide or halogen.

23. The biodegradable microparticle according to any one of claims 20 to 22, wherein the nucleophile is an amine group, in particular a primary amine, and the electrophile is an active ester group, in particular a succinimidyl ester selected from the group consisting of succinimidyl succinate, succinimidyl glutarate, succinimidyl adipate, succinimidyl azelate or succinimidyl glutaramide.

24. The biodegradable microparticle according to claim 18, wherein the first functional group and the second functional group are each selected from functional groups for click chemistry, in particular functional groups for cycloaddition reactions, in particular 1,3 dipolar cycloaddition reactions, [3+2] cycloaddition reactions such as olefin-nitrone cycloaddition reactions or alkyne-nitrone cycloaddition reactions, [4+2] cycloaddition reactions, hetero Diels-Alder cycloaddition reactions; functional groups for thiol-ene reactions; functional groups for nucleophilic ring opening; functional groups for non-aldol type carbonyl reactions; functional groups for addition reactions with carbon-carbon multiple bonds; and functional groups for Michael type addition reactions.

25. The biodegradable microparticle of claim 24, wherein the first functional group is an alkyne compound, such as dibenzocyclooctyne (DBCO) or bicyclo[6.1.0]-nonyne (BCN); or norbornene or trans-cyclooctene (TCO), and the second functional group is azide, 3,4-dihydroxyphenylacetic acid (DHPA) or tetrazine (Tz).

26. The biodegradable microparticle of claim 25, wherein the DBCO, BCN, norbornene, TCO, azide, DHPA and Tz functional groups are grafted to the ends of the multi-arm precursor via a linker, such as an acid group, a diacid group, a functionalized aliphatic group, a heteroaliphatic group, or an aromatic group or a heteroaromatic group.

27. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are selected for a [3+2] cycloaddition reaction, such as an alkene-nitrone cycloaddition reaction or an alkyne-nitrone cycloaddition reaction.

28. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are selected for a [4+2] cycloaddition reaction, in particular a hetero-Dickens-Alder reaction, wherein the first functional group is an aldehyde or an imine compound, and the second functional group is a 1,3 diene compound, an unsaturated carbonyl compound, or a nitroso-olefin compound.

29. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are selected for a thiol-ene reaction, wherein the first functional group is a thiol compound and the second functional group is an olefin, preferably a terminal olefin.

30. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are selected for nucleophilic ring opening, wherein the first functional group is selected from epoxide, thiirane, aziridine or lactam, and the second functional group is a nucleophile.

31. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are selected for a non-aldol type carbonyl reaction, wherein the first functional group is an aldehyde or ketone compound and the second functional group is a primary amine, hydrazine, hydrazide or aminooxy compound for forming an imine, amide, isourea, hydrazone, acylhydrazone or oxime linkage.

32. The biodegradable microparticle of claim 18, wherein the first functional group and the second functional group are each selected from polymerizable vinyl groups and acrylates, such as (meth)acrylic acid, (meth)acrylate, acrylamide, fumaric acid, maleic acid, and combinations thereof.

33. The biodegradable microparticle according to claim 32, wherein crosslinking is induced thermally or photochemically, optionally using an initiator, for example a photoinitiator, such as a free radical photoinitiator (Norish I type, for example 2,2-dimethoxy-1,2-diphenyl-ethan-1-one, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxy-cyclohexylphenyl ketone; or Norish II type, for example benzophenone and its derivatives and isopropylthioxanthone in combination with a synergist such as the tertiary amines 2-ethylhexyl-(4-N,N-dimethylamino)benzoate and 2-ethyl-(4-N,N-dimethylamino)benzoate); or a cationic photoinitiator.

34. The biodegradable microparticle of any preceding claim, wherein the polymer is covalently cross-linked via linkages between polymer units.

35. The biodegradable microparticle of claim 34, wherein the linkage is selected from the group consisting of an amine, amide, carbamate, ester, anhydride, ether, acetal, ketal, nitrile, isonitrile, isothiocyanate, isourea, hydrazone, oxime or imine bond, and combinations thereof.

36. The biodegradable microparticle according to any one of the preceding claims, wherein the active agent is selected from at least one of a therapeutically active agent or a diagnostically active agent, or a combination thereof.

37. The biodegradable microparticles according to any one of the preceding claims, wherein the therapeutically active agent is selected from the group consisting of steroids; nonsteroidal anti-inflammatory drugs (NSAIDS), such as diclofenac, ibuprofen, meclofenamic acid, mefenamic acid A, salicylate, sulindac, tolmetin, ketoprofen, diflunisal, piroxicam, naproxen, etodolac, flurbiprofen, fenoprofen C, indomethacin, celecoxib, ketorolac, nepafenac; intraocular pressure reducing drugs; antibiotics, such as ciprofloxacin; analgesics, such as bupivacaine; calcium channel blockers, such as nifedipine; complement inhibitors, such as pegol; cell cycle inhibitors, such as simvastatin; proteins small molecule hydrophilic drugs, including carboxylates and amine salts; small molecule hydrophobic drugs, hydrophilic peptides and protein drugs, such as insulin, single-chain antibody fragments, Fab fragments, IgG antibodies, fusion antibodies, etc.; aptamers; in particular bupivacaine (BPV-HCl or base), ropivacaine (RPV), dexamethasone, travoprost, axitinib, non-steroidal anti-inflammatory drugs (NSAIDs), steroids, antibiotics, analgesics, calcium channel blockers, cell cycle inhibitors, chemotherapeutic agents, antiviral drugs, anesthetics, hormones, anticancer drugs, antitumor agents, viruses, viruses for gene delivery such as AAV, etc., or any combination thereof.

38. The biodegradable microparticles according to any one of the preceding claims, wherein the microparticles have a particle size (diameter) of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by sieving, or have an average diameter in the range of 0.1-1000 μm, or 1 to 150 μm, 1 to 100 μm, 20 to 75 μm, 10 to 106 μm or 20 to 55 μm as determined by laser diffraction.

39. The biodegradable microparticles according to any one of the preceding claims, wherein the microparticles have a particle size distribution, for example as determined by laser diffraction, with a D50 particle size of less than about 100 μm, or less than about 50 μm, or less than about 20 μm, and / or a D90 particle size of less than about 200 μm, or less than about 50 μm, or a D90 particle size of about 100 μm or less, or 30 μm or less, and / or a D90 particle size of about 20 μm or less.

40. The biodegradable microparticle according to any one of the preceding claims, consisting of: Blends of microparticles of different particle sizes and / or having different polymer matrices and / or comprising different active agents.

41. The biodegradable microparticle of any preceding claim, wherein the choice of organogel precursor, and / or the hydrophobicity of the polymer units, and / or the L / G ratio of the PLGA units are used to tune the release rate.

42. The biodegradable microparticles according to any of the preceding claims, which release a therapeutically or diagnostically effective amount of the active agent over a period of time, for example up to 1 year, up to 9 months, up to 6 months, up to 3 months, up to 1 month or up to about 25 days after administration, preferably up to about 14 days or up to about 21 days after administration, wherein optionally the release of the active agent is substantially constant within a temperature range of 30°C to 45°C or 36°C to about 43°C.

43. The biodegradable microparticles according to any one of the preceding claims, wherein the polymer matrix has a glass transition temperature below human body temperature, for example below 37°C, or below 36°C, below 30°C, below 25°C, below 20°C or below 10°C, and / or wherein the polymer matrix has a melting temperature above 40°C, 45°C, 50°C, 60°C or 70°C.

44. A method for manufacturing biodegradable microparticles for sustained release drug delivery according to any one of the preceding claims, the method being selected from one of the following techniques: emulsion solvent evaporation-extraction, emulsion solvent diffusion, supercritical fluid emulsification, coacervation, spray drying, hydrogel templates, microfluidic systems, membrane extrusion emulsification, particle replication in non-wetting templates (PRINT) technology, electrohydrodynamic atomization (EHDA) or electrospraying, or particles from gas saturated solution (PGSS) method, or using 3D printing.

45. The manufacturing method according to claim 44, comprising the steps of: (1) forming a gel comprising covalently cross-linked polymers in the presence of at least one active agent, optionally at least one oil, and optionally a first solvent, (2) producing microparticles wherein the at least one active agent is dispersed in the covalently cross-linked polymer, and (3) Optionally, removing the solvent.

46. ​​The method of claim 45, comprising the steps of: (h) dissolving at least one polymer precursor in a first solvent to obtain a first mixture; (i) providing a second mixture comprising a cross-linking agent in a second solvent; (j) adding at least one active agent and optionally oil to at least one of the first mixture or the second mixture; (k) combining the first mixture with the second mixture to produce a first phase; (1) providing a second phase comprising a third solvent, the third solvent being immiscible with the first solvent and the second solvent; (m) introducing the first phase into the second phase under agitation, thereby producing an emulsion in which the first phase is dispersed in the second phase; as well as (n) removing the first solvent, the second solvent and / or the third solvent.

47. A method as claimed in claim 45 or 46, wherein the step of producing microparticles (step (2)) or the step f) comprises forcing the first phase through a screen, or injecting the first phase into an agitated second phase, the first solvent and / or the second solvent and / or the third solvent optionally containing additives such as emulsifiers, surfactants, dispersing aids or porogens, so as to form microspheres or nanosphere particles.

48. The method of any one of claims 45 to 47, wherein the first solvent and / or the second solvent is an organic solvent in which the precursor is soluble, and the third solvent is a solvent in which the first phase and / or the organogel formed thereof is not soluble.

49. The method of claim 48, wherein the first solvent or the second solvent is selected from acetone, acetonitrile, benzyl alcohol, chloroform, dichloromethane (DCM), dioxane, dimethyl carbonate, DMSO, ethanol, ethyl acetate, ethyl formate, ethyl propionate, tetraethylene glycol ether, hexafluoroisopropanol, dimethyl isosorbide, isopropanol, chloromethane, dichloromethane, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate or tetrahydrofuran, or any mixture thereof, and the third solvent is water; an alcohol such as methanol, ethanol or propanol; or any mixture thereof.

50. The method of any one of claims 46 to 49, wherein the additive is selected from surfactants or emulsifiers, such as polyvinyl alcohol (PVA), polyethylene glycol sorbitan monolaurate (Tween®), sorbitan monolaurate (Span®), sodium dodecyl sulfate (SDS); and / or porogens, such as inorganic salts (NaCl, KCl, sodium or potassium carbonates or bicarbonates, ammonium bicarbonate), pluronic; sodium or potassium oleate; gelatin; mustard oil, mineral oil; cyclodextrins; carbohydrates, bovine serum albumin (BSA); photoinitiators, free radical polymerization initiators, and combinations thereof.

51. The method of any one of claims 45 to 50, wherein steps 1 and 2 utilize water-in-oil emulsion or oil-in-water emulsion technology, or a combination thereof, in particular single or double emulsion technology, or microfluidics technology, or a combination thereof.

52. The method of any one of claims 45 to 51, wherein the removal of the first solvent and / or the second solvent and / or the third solvent is performed by one of the following methods: hot air convection or direct drying, indirect or contact drying, spray drying, dielectric drying, vacuum drying, freeze drying, supercritical or superheated steam drying, or a combination of any one thereof.

53. A biodegradable sustained-release drug delivery system comprising the biodegradable microparticles for sustained-release drug delivery according to any one of claims 1 to 43.

54. The biodegradable sustained release drug delivery system of claim 52, wherein the biodegradable microparticles are incorporated into a hydrogel, xerogel or organogel, optionally by using an extrusion method or by 3D printing.

55. The biodegradable sustained-release drug delivery system of claim 53 or 54, which is used for coating a medical implant or as a medical implant.

56. The biodegradable sustained release drug delivery system of claim 55, wherein the implant is selected from the group consisting of an intraocular implant, an intracavitary implant, an intracameral implant, an implant for introduction into the anterior chamber, vitreous, episcleral, posterior subfascial space (fornix), subconjunctival, intracameral, peribulbar, retrobulbar, subfascial, retinal, subretinal, intratubular, intravitreal, intrascleral, choroidal, suprachoroidal space, retinal, subretinal or lens, surface of the cornea or conjunctiva, lacrimal puncta (tubules, superior / inferior tubules), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, fascia, cornea, cancer tissue, organ, prostate, breast, joint space, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or injury, void space, and potential space.

57. The biodegradable sustained release drug delivery system of any one of claims 53 to 58, wherein the system is obtained by extrusion or injection molding of a reaction mixture comprising the biodegradable microparticles of any one of claims 1 to 43 dispersed in a hydrogel, xerogel or organogel or a precursor thereof.

58. The biodegradable sustained-release drug delivery system of claim 57, wherein gelling occurs before and / or during extrusion or injection molding of the gel-forming material comprising the biodegradable microparticles.

59. A biodegradable sustained release drug delivery system as claimed in any one of claims 53 to 57 or manufactured according to the method of any one of claims 44 to 52 for use as a medicament.

60. A biodegradable sustained release drug delivery system as claimed in any one of claims 53 to 57 or manufactured according to the method of any one of claims 44 to 52, for use in treating a disease / medical condition in a patient, said use comprising incorporating the biodegradable microparticles according to any one of claims 1 to 43 into a carrier, such as a hydrogel, organogel or xerogel, wherein the hydrogel, organogel or xerogel is formed in situ at the treatment site of the patient, or is pre-made and delivered to or implanted at the treatment site of the patient, so as to release the active agent from the microparticles over an extended period of time, or the carrier is a solvent or solvent system for producing an injectable suspension or dispersion.

61. A method for treating a disease / medical condition in a patient, the method comprising incorporating the biodegradable microparticles according to any one of claims 1 to 43 into a hydrogel, organogel or xerogel, wherein the hydrogel, organogel or xerogel is formed in situ at a treatment site in the patient, or is pre-manufactured and delivered or implanted at a treatment site so as to release the active agent over an extended period of time.

62. A method for treating a disease / medical condition in a patient, the method comprising administering to the patient a hydrogel, organogel or xerogel comprising the biodegradable microparticles according to any one of claims 1 to 43 so as to release the active agent over an extended period of time.

63. The system for use or method of treatment of any one of claims 53 to 62, wherein the treatment site is selected from the group consisting of anterior chamber, vitreous, episcleral, posterior subfascial space (fornix), subconjunctival, intra-anterior chamber, peribulbar, retrobulbar, subfascial, retinal, subretinal, intracanalicular, intravitreal, intrascleral, choroidal, suprachoroidal space, retina, subretinal or lens, surface of cornea or conjunctiva, lacrimal puncta (canaliculus, superior / inferior canaliculus), fornix, superior / inferior fornix, subfascial space, choroid, suprachoroidal, fascia, cornea, cancer tissue, organ, prostate, breast, joint, subdural, tooth, subcutaneous, carpal tunnel, perivascular, surgically created space or lesion, void space, and potential space.

64. A system for use or a method for treatment according to any one of claims 53 to 62, wherein the disease / medical condition to be treated is an eye disease, such as a posterior ocular disease, such as any posterior segment disease affecting the vasculature and integrity of the retina, macula or choroid, leading to visual acuity impairment, vision loss or blindness, particularly posterior segment disease states caused by age, trauma, surgical intervention, such as age-related macular degeneration (AMD), cystoid macular edema (CME), diabetic macular edema (DME), posterior uveitis and diabetic retinopathy; or glaucoma, intraocular hypertension, hyphema, presbyopia, cataract, retinal vein occlusion, inflammation.

65. A method for controlling the release of an active agent from a biodegradable sustained-release drug delivery system according to any one of claims 53 to 60 or manufactured according to the method of any one of claims 44 to 52, said method being achieved by any one or a combination of the following measures: - selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units to adjust the hydrophobicity of the polymer matrix forming the microparticles; - selecting the L / G ratio of the polylactic-co-glycolic acid (PLGA) units to provide sustained release of the active agent from the microparticles; - selecting the molar ratio of the amount of the first crosslinkable precursor to the second crosslinkable precursor so as to adjust the hydrophobicity of the polymer matrix forming the microparticles; - selecting a molar ratio of the amount of the first cross-linkable precursor to the amount of the second cross-linkable precursor to provide a sustained release of the active agent from the microparticles; - selecting the amount and / or particle size of said biodegradable microparticles to be included in said hydrogel, organogel xerogel; - adding a third crosslinkable precursor having a lower hydrolyzability than the first crosslinkable precursor and the second crosslinkable precursor, optionally after forming the biodegradable microparticle, modifying the molar ratio of the first precursor, the second precursor and / or the third precursor; - Active agents with high water solubility in particulate form are dispersed in an organogel of biodegradable microparticles.

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