The present invention relates to the molecular sustained controlled release system constructed by the conjugation of molecules to be released with biodegradable polyester polymer via covalent bond and method for preparation thereof. In accordance with the present invention, the system may be formulated into microspheres, nanoparticles, or films. The molecular release rate from the above system can be regulated to be proportional to the chemical degradation rate of the biodegradable polyester polymers, resulting in near zero order kinetics profile of release without showing a burst effect. Moreover, the high loading efficiency of hydrophilic drugs can be achieved.

SUMMARY OF THE INVENTION

It accordance with the present invention, There is provided a novel sustained controlled release system constructed by, conjugation of molecules to be released with biodegradable polyester polymers.

In particular, the present invention provides a sustained controlling-release system with high loading efficiency of drug molecules.

The present invention also provides the sustained controlled release system formulated into microspheres, preferably about 1 to about 300 .mu.m in diameter, nanoparticles, preferably about 50 to about 1000 nm in diameter, or films.

In addition, this invention Provides the sustained controlled release system using biodegradable polyester polymer selected from the groups comprising poly(lactic acid), poly(glycolic acid), poly(D-lactic-co-glycolic acid), poly(L-lactic-co-glycolic acid), poly(D,L-lactic-co-glycolic acid), poly(caprolactone), poly(valerolactone), poly(hydroxybutyrate), poly(hydrovalerate), polydioxnanone, and derivatives thereof. More preferably, the biodegradable polyester polymer is about 1,000 Da to about 100,000 Da in molecular weight.

This invention additionally provides the system using poly(lactic-co-glycolic acid) as a biodegradable polyester with various compositions, wherein the preferred ratio of lactic acid and glycolic acid, from 1:10 to 10:1.

This invention provides the system employing the ester bond, amide bond, anhydride bond, urea bond, urethane bond, carbonate bond, thioester bond, disulfide bond, imine bond, thioester bond, disulfide bond or carbamate bond for conjugation of molecules with biodegradable polyester polymers.

This invention also provides the system wherein the specified moieties are either directly bound to one another through covalent bond, or else indirectly bound to one another with an additional moiety such as a bridge, spacer, or linkage moieties.

Additionally, this invention provides the system wherein the molecules to be loaded are selected from the groups comprising peptides, proteins, therapeutic agents, diagnostic agent, and non-biological materials such as pesticides, herbicides, and fertilizers.

This invention also provides a process of preparing the sustained controlled release system, comprising the steps of; 1) activating drug molecule or polymer by mixing with coupling agents, bases, and, if needed, additives; 2) conjugating drug molecule with polymer by adding drug molecule to the activated polymer solution of step 1, or by adding polymer to the activated drug molecule solution of step 1; 3) purifying polymer-molecule conjugate of step 2.

Accordingly, an object of the present invention is to provide biodegradable polyester polymer-drug conjugates formed via covalent bond.

Another object of the present invention is to provide biodegradable polyester polymer-drug conjugates having an advantage that the removal process of the polymer carrier is not required after drug release, as a result of polymer degradation into low molecular weight molecules.

Still the object of the present invention is to provide microspheres, nanoparticles or films that are easy to formulate from biodegradable polyester polymer-drug conjugate by a single oil in water emulsion method.

Yet another object of the present invention is to provide microspheres, nanoparticles and films to get the high loading efficiency of hydrophilic drug.

A further object of the present invention is to provide a sustained controlled release system wherein the initial burst of molecules is prevented and zero order release profile is achieved by controlling the molecule release rate in accordance with the chemical degradation rate of the biodegradable polymer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a sustained controlled release system constructed by the conjugation of drug molecules to the terminal groups of biodegradable polyester polymers via covalent bond, with high loading efficiency.

The present invention also relates to the method for preparing system wherein the solvent is selected from the group comprising methylene chloride, N,N-dimethylformamide, dimethylsulfoxide, and tetrahydrofuran.

In accordance with the present invention, the conjugate of target molecules and polymers is formulated into microspheres and polymers is formulated into microspheres, nanoparticles, or films. In the preferred embodiments, microspheres are approximately 1 to approximately 300 .mu.m and nanoparticles are about 50 to about 1,000 nm in size.

The present biodegradable polyester polymer may be selected from the group comprising poly(lactic acid), poly(glycolic acid), poly(D-lactic-co-glycolic acid), poly(L-lactic-co-glycolic acid), poly(D,L-lactic-co-glycolic acid), poly(caprolactone), poly(valerolatone), poly(hydroxybutyrate), poly(hydrovalerate), polydioxnanone, and their derivatives. Preferably, the molecular weight range of the biodegradable polyester polymer is from about 1,000 Da to 100,000 Da.

Also, the biodegradable polyester polymer is selected from poly(lactic-co-glycolic acid) with various compositions (the ratio of lactic acid and glycolic acid, from 1:10 to 10:1) for satisfying the required biocompatibility of the molecule to be delivered including degradation rate and degradation profile.

The present invention is based on the conjugation of molecule to be delivered with biodegradable polyester via covalent bond. Covalent bonding structure is defined as follows.

Biodegradable polyester polymer has two kind of functional group, i.e., carboxyl and hydroxy group. The conjugation method, therefore, may be divided into two groups; the method wherein the molecules are coupled to carboxyl group of polyester polymer, and the method wherein the molecules are coupled to hydroxy group of polyester polymer. Namely, drug molecules can be covalently conjugated with more than one functional group of polyester polymer. In either method, the drug-polymer conjugate may be formed by appropriate linker or spacer additionally, for coupling or introducing the multifunctional groups, respectively.

Moreover, preferably the covalent bond may be formed using multifunctional ligand. In particular, one or more drug molecules may be conjugated to the triglycerol covalently bound to biodegradable polyester polymer. In another preferred embodiment, covalent bond may be formed by conjugating alkyl spacer or other feasible spacer to glycerol or glyceraldehyde.

In case of all mentioned above, the covalent bond between molecules and biodegradable polyester polymers may be ester bond, amide bond, anhydride bond, carbonate bond, urea bond, urethane bond, thioester bond, disulfide bond, imine bond, or carbamate bond, which can or can not be broken down by enzymatic or nonenzymatic degradation.

Illustrative examples of molecules that can be used in the system of the present invention include; biologically active compounds such as peptides, proteins, therapeutic agents, diagnostic agents, and non-biological materials such as pesticides, herbicides, and fertilizers.

Preferably, peptides are selected from the group comprising insulin, calcitonin, ACTH, glucagon, somatostatin, somatotropin, somatomedin, parathyroid hormone, erythropoietin, hypo-thalmic releasing factors, prolactin, thyroid stimulating hormone, endorphins, enkephalins, vasopressin, non-naturally occurring opioids, superoxide dismutase, interferon, asparaginase, arginase, arginine deaminase, adenosine deaminase, ribonuclease, trypsin, chemotrypsin, and pepsin.

Therapeutic agent may comprise anticancer agents such as dideoxyinosine, floxuridine, 6-mercaptopurine, doxorubicin, daunorubicin, I-darubicin, cisplatin, methotrexate, etc.; antibiotics such as erythromycin, vancomycin, oleandomycin, ampicillin, etc.; anticoagulant such as heparin; germicides such as ara-A, acrylguanosine, nordeoxyguanosine, azidothymidine, dideoxyadenosine, dideoxythymidine, etc.; antiarrythmic agent; and prodrugs and derivatives thereof.

The present invention also relates to a method for manufacturing the sustained controlled release system.

A method, wherein the conjugation of molecule with polyester polymer is carried out, comprises the steps of; 1) activating drug molecule or polymer by mixing with coupling agents, bases, and, if needed, additives; 2) conjugating drug molecule with polymer by adding drug molecule to the activated polymer solution of step 1, or by adding polymer to the activated drug molecule solution of step 1; 3) purifying polymer-molecule conjugate of step 2.

The coupling agent of step 1 may be one or more selected from the group comprising bis(2-oxo-3-oxazolydinyl)phosphonic chloride (BOP-Cl), bromo-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBroP), benzotriazol-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU), dicyclohexyl carbodiimide, disuccinimidyl carbonate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), bis(2-oxo-3-oxazolydinyl)phosphin, diisopropyl carbodiimde (DIPC), 2-(1H-benzotrioxazolyl)-1,1,3,3-tetramethyl-uronium tetrafluoroborate (TBTU), 2-(5-norboren)-2,3-dicarboxyimido)-1,1,3,3-tetramethyluronium tetrafluoroborate (TNTU), para-nitrophenylchloroformate and O-(N-succinimidyl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TSTU).

The base of step 1 may be selected from the groups comprising triethylamine, N-methylmorpholine, pyridine, 1,8-diazabicyclo[5,4,0]-undec-7-ene, N,N-dimethyl aminopyridine, and N,N-diisopropyl ethylamine.

The additives of step 1 may be one or more selected from the groups comprising hydroxybenzotriazole, pentafluorophenol, and N-hydroxy-5-norboren-endo-2,3-dicarboximide.

In this invention, we designed microspheres, nanoparticles, and films by conjugating various target molecules to the terminal end groups of biodegradable polyester microspheres, nanoparticles, and films via a biodegradable ester bond, amide bond, or carbamate linkage to obtain a zero order release kinetic profile. The strategy is that when the conjugated biodegradable polyester chains are randomly hydrolyzed and water soluble fractions are leached out [R. A. Kenley, et al., macromolecules, 20 (1987) 2398 2403], target drug molecules which were bound to the terminal ends of the cleaved polyester oligomer are released out concomitantly. The drug release rate from the proposed system is expected to be proportional to mass erosion rate of the biodegradable microspheres, nanoparticles, and films. After the release, polyester oligomer chains conjugated to the drug moiety would be further degraded, eventually generating an intact free drug and/or drug with 1 3 polyester oligomer chain.

The main advantage of the conjugation of drug to biodegradable polyester is, first to prevent the initial burst and control the sustained release of molecules from microspheres, nanoparticles, and films. Second, drug-polymer conjugates are easily formulated into microspheres, nanoparticles, and films by a single Oil-in-Water emulsion method with very high encapsulation efficiency (almost 100%).

 

Claim 1 of 18 Claims

1. A sustained controlled release system consisting of a drug molecule to be released directly conjugated to a biodegradable polyester polymer via a covalent bond, wherein the conjugation is carried out after activating the biodegradable polyester polymer by mixing with coupling agents, bases and optionally additives, wherein the coupling agents are selected from the group comprising bis(2-oxo-3-oxazolydinyl)phosphonic chloride (BOP-Cl), bromo-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBroP), benzotriazol-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyl-uronium hexafluorophosphate (HBTU), dicyclohexyl carbodiimide, disuccinimidyl carbonate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), bis(2-oxo-3-oxazolydinyl)phosphin, diisopropyl carbodiimde (DIPC), 2-(1H-benzotrioxazolyl)-1,1,3,3-tetramethyl-uronium tetrafluoroborate (TBTU), 2-(5-norboren)-2,3-dicarboxyimido)-1,1,3,3-tetramethyluronium tetrafluoroborate (TNTU), para-nitrophenylchloroformate, and O-(N-succinimidyl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TSTU), and wherein the bases are selected from the group consisting of triethylamine, N-methylmorpholine, pyridine, 1,8-diazabicyclo[5,4,0]-undec-7-ene, N,N-dimethyl aminopyridine, and N,N-diisopropyl ethylamine.
 

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