U.S. patent application number 11/617935 was filed with the patent office on 2007-05-10 for matrices formed of polymer and hydrophobic compounds for use in drug delivery.
This patent application is currently assigned to Acusphere, Inc.. Invention is credited to Howard Bernstein, Donald Chickering, Sarwat Khattak, Julie Straub.
Application Number | 20070104656 11/617935 |
Document ID | / |
Family ID | 26769533 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070104656 |
Kind Code |
A1 |
Bernstein; Howard ; et
al. |
May 10, 2007 |
Matrices Formed of Polymer and Hydrophobic Compounds For Use in
Drug Delivery
Abstract
A lipid or other hydrophobic or amphiphilic compound
(collectively referred to herein as "hydrophobic compounds") is
integrated into a polymeric matrix for drug delivery to alter drug
release kinetics. In embodiments where the drug is water soluble,
the drug is released over longer periods of time as compared to
release from the polymeric matrix not incorporating the hydrophobic
compound into the polymeric material. In contrast to methods in
which a surfactant or lipid is added as an excipient, the
hydrophobic compound is actually integrated into the polymeric
matrix, thereby modifying the diffusion of water into the
microparticle and diffusion of solubilized drug out of the matrix.
The integrated hydrophobic compound also prolongs degradation of
hydrolytically unstable polymers forming the matrix, further
delaying release of encapsulated drug.
Inventors: |
Bernstein; Howard;
(Cambridge, MA) ; Chickering; Donald; (Framingham,
MA) ; Khattak; Sarwat; (Hadley, MA) ; Straub;
Julie; (Winchester, MA) |
Correspondence
Address: |
PATREA L. PABST;PABST PATENT GROUP LLP
400 COLONY SQUARE, SUITE 1200
1201 PEACHTREE STREET
ATLANTA
GA
30361
US
|
Assignee: |
Acusphere, Inc.
|
Family ID: |
26769533 |
Appl. No.: |
11/617935 |
Filed: |
December 29, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09730694 |
Dec 6, 2000 |
7160557 |
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11617935 |
Dec 29, 2006 |
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09255179 |
Feb 22, 1999 |
6423345 |
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09730694 |
Dec 6, 2000 |
|
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60083636 |
Apr 30, 1998 |
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Current U.S.
Class: |
424/46 ; 424/486;
424/488 |
Current CPC
Class: |
Y10S 514/952 20130101;
Y10S 514/951 20130101; A61K 9/1617 20130101; A61K 9/1647
20130101 |
Class at
Publication: |
424/046 ;
424/486; 424/488 |
International
Class: |
A61K 9/14 20060101
A61K009/14 |
Claims
1. A polymeric matrix for delivery of a therapeutic or prophylactic
agent, wherein the matrix is formed of a biocompatible polymer
having incorporated therein an therapeutic or prophylactic agent
and an effective amount of a hydrophobic or amphiphilic compound to
modify the diffusion of water into the matrix and the release of
the therapeutic or prophylactic agent from the matrix.
2. The matrix of claim 1 wherein the matrix is in the form of
microparticles.
3. The matrix of claim 1 wherein the hydrophobic or amphiphilic
compound is incorporated into the matrix at a ratio of between 0.01
and 60 by weight of hydrophobic compound to weight of polymer.
4. The matrix of claim 3 wherein the hydrophobic or amphiphilic
compound is a lipid incorporated into the matrix at a ratio of
between 0.01 and 30 (weight lipid/weight matrix material).
5. The matrix of claim 4 wherein the lipid is selected from the
group consisting of fatty acids and derivatives, mono-, di and
triglycerides, phospholipids, sphingolipids, cholesterol and
steroid derivatives, oils, vitamins and terpenes.
6. The matrix of claim 5 wherein the lipid is a phospholipid
selected from the group consisting of phosphatidic acids,
phosphatidyl cholines with both saturated and unsaturated lipids,
phosphatidyl ethanolamines, phosphatidylglycerols,
phosphatidylserines, phosphatidylinositols, lysophosphatidyl
derivatives, cardiolipin, and .beta.-acyl-y-alkyl
phospholipids.
7. The matrix of claim 6 wherein the phospholipid is selected from
the group consisting of dioleoylphosphatidylcholine,
dimyristoylphosphatidylcholine, dipentadecanoylphosphatidylcholine
dilauroylphosphatidylcholine, dipalmitoylphosphatidylcholine,
distearoylphosphatidylcholine, diarachidoylphosphatidylcholine,
dibehenoylphosphatidylcholine, ditricosanoylphosphatidylcholine,
dilignoceroylphatidylcholine; and phosphatidylethanolamines.
8. The matrix of claim 1 wherein the agent is a therapeutic
agent.
9. The matrix of claim 1 wherein the matrix is formed of a
bioadhesive polymer.
10. The matrix of claim 1 wherein the matrix is formed is formed of
a polymer selected from the group consisting of poly(hydroxy
acids), polyanhydrides, plyorthoesters, polyamides, polycarbonates,
polyalkylenes, polyalkylene glycols, polyalkylene oxides,
polyalkylene terepthalates, polyvinyl alcohols, polyvinyl ethers,
polyvinyl esters, polyvinyl halides, polyvinylpyrrolidone,
polysiloxanes, poly(vinyl alcohols), poly(vinyl acetate),
polystyrene, polyurethanes and co-polymers thereof, synthetic
celluloses polyacrylic acids, poly(butyric acid), poly(valeric
acid), and poly)lactide-co-caprolactone), ethylene vinyl acetate,
copolymers and blends thereof.
11. The matrix of claim 1 wherein the matrix is formed of a protein
or polysaccharide.
12. The matrix of claim 1 wherein the matrix is in a
pharmaceutically acceptable carrier for topical application or
application to a mucosal surface.
13. The matrix of claim 1 wherein the matrix is in a
pharmaceutically acceptable carrier for injection.
14. The matrix of claim 1 wherein the matrix is formulated for
administration rectally or vaginally.
15. The matrix of claim 2 wherein the microparticles are formulated
for pulmonary administration.
16. A method for making a polymeric matrix comprising a
biocompatible polymer having incorporated therein an therapeutic or
prophylactic agent and a hydrophobic or amphiphilic compound,
comprising distributing the hydrophobic compound into the polymer
in an amount effective to modify the diffusion of water into the
matrix and the rate of release of the therapeutic or prophylactic
agent.
17. The method of claim 16 wherein the matrix is formed by melting
the polymer with the hydrophobic or amphiphilic compound.
18. The method of claim 16 wherein the matrix is formed by
dissolving the polymer with the hydrophobic or amphiphilic compound
together.
19. The method of claim 16 wherein the solvent is removed by
evaporation or extraction.
20. A method for administering a therapeutic or prophylactic agent
comprising administration to a patient a polymeric matrix
comprising a biocompatible polymer having incorporated therein an
therapeutic or prophylactic agent and an effective amount of a
hydrophobic or amphiphilic compound to modify the diffusion of
water into the matrix and the release of the therapeutic
prophylactic agent from the matrix.
Description
[0001] This claims priority to U.S. Ser. No. 60/083,636 filed Apr.
30, 1998 for "Lipid Polymer Compositions For Enhanced Drug
Delivery" by Howard Bernstein, Donald E. Chickering and Julie Ann
Straub.
BACKGROUND OF THE INVENTION
[0002] The present invention is generally in the area of drug
delivery, and is particularly directed to polymer matrices
containing drug and having lipid or another hydrophobic or
amphiphilic compound incorporated therein to modify the release
kinetics. The matrices are preferably used for parenteral delivery.
The matrices are preferably in the form of microparticles.
[0003] Controlled or sustained release compositions have been
developed over the last twenty to thirty years in order to increase
the amount of drug delivered by any of a variety of routes, to
sustain drug release in a controlled fashion, thereby avoiding
burst release which can cause elevated but transient drug levels,
and to provide a means for customized release profiles. These
formulations have taken many forms, including microparticles such
as microspheres and microcapsules formed of drug and encapsulated
or mixed with a natural or synthetic polymer, drug particles mixed
with excipients such as surfactants to decrease agglomeration of
the particles, and devices such as the silastic controlled release
depots which release drug as a function of diffusion of water into
the device where it dissolves and releases drug back out the same
entry. It is difficult to achieve sustained release when the
delivery means consists solely of drug or drug and excipient since
the drug tends to solubilize relatively quickly. In contrast,
non-biodegradable devices such as the silastic devices must be
removed after usage.
[0004] Microparticles have been formed using a wide range of
techniques, including spray drying, hot melt, solvent evaporation,
solvent extraction, and mechanical means such as milling and
rolling. The microparticles are typically formed of a biocompatible
material having desirable release properties as well as being
processible by techniques compatible with the drug to be delivered.
Many drugs are labile and cannot be encapsulated using harsh
organic solvents or heat. Most of these methods result in formation
of a structure where drug is released by diffusion of drug out of
the microparticle and/or degradation of the microparticle. In some
cases it is desirable to further limit or control diffusion.
[0005] It is an object of this invention to provide microparticles
which have incorporated therein means for limiting diffusion of
drug out of the microparticle.
[0006] It is a further object of this invention to provide
biodegradable microparticles which have incorporated therein means
for modifying the degradation kinetics of the microparticles.
[0007] It is still another object of the present invention to
provide microparticles particularly well suited for parenteral drug
delivery.
SUMMARY OF THE INVENTION
[0008] A lipid or other hydrophobic or amphiphilic compound
(collectively referred to herein as "hydrophobic compounds") is
integrated into a polymeric matrix for drug delivery to alter drug
release kinetics. In one embodiment where the drug is water
soluble, the drug is released over longer periods of time as
compared to release from the polymeric matrix not incorporating the
hydrophobic compound into the polymeric material. In a further
embodiment where the drug has low water solubility, the drug is
released over shorter periods of time as compared to release from
matrix not incorporating the hydrophobic compound into the
polymeric material. In contrast to methods in which a surfactant or
lipid is added as an excipient, the hydrophobic compound is
actually integrated into the polymeric matrix, thereby modifying
the diffusion of water into the microparticle and diffusion of
solubilized drug out of the matrix. The integrated hydrophobic
compound also prolongs degradation of hydrolytically unstable
polymers forming the matrix, further delaying release of
encapsulated drug.
[0009] The hydrophobic compound must be incorporated into the
matrix and the matrix shaped using a technique which results in
integration of the hydrophobic compound into the polymeric matrix,
rather than at the outer surface of the matrix. In the preferred
embodiment, the matrix is formed into microparticles. The
microparticles are manufactured with a diameter suitable for the
intended route of administration. For example, with a diameter of
between 0.5 and 8 microns for intravascular administration, a
diameter of 1-100 microns for subcutaneous or intramuscular
administration, and a diameter of between 0.05 and 5 mm for oral
administration for delivery to the gastrointestinal tract or other
lumens. A preferred size for administration to the pulmonary system
is an aerodynamic diameter of between one and three microns, with
an actual diameter of five microns or more. In the preferred
embodiment, the polymers are synthetic biodegradable polymers. Most
preferred polymers are biocompatible hydrolytically unstable
polymers like polyhydroxy acids such as polylactic acid-co-glycolic
acid, polylactide, polyglycolide or polyactide co-glycolide, which
may be conjugated to polyethylene glycol or other materials
inhibiting uptake by the reticuloendothelial system (RES).
[0010] The hydrophobic compounds can be hydrophobic compounds such
as some lipids, or amphiphilic compounds (which include both a
hydrophilic and hydrophobic component or region). The most
preferred amphiphilic compounds are phospholipids, most preferably
dipalmitoylphosphatidylcholine (DPPC),
distearoylphosphatidylcholine (DSPC),
diarachiodoylphosphatidylcholine (DAPC),
dibehenoylphosphatidylcholine (DBPC),
ditricosanoylphosphatidylcholine (DTPC), and
dilignoceroylphatidycholine (DLPC), incorporated at a ratio of
between 0.01-60 (w/w polymer), most preferably between 0.1-30 (w
lipid w/polymer).
[0011] Surface properties of the matrix can also b modified. For
example, adhesion can be enhanced through the selection of
bioadhesive polymers, which may be particularly desirable when the
matrix is in the form of microparticles administered to a mucosal
surface such as in intranasal, pulmonary, vaginal, or oral
administration. Targeting can also be achieved by selection of the
polymer or incorporation within or coupling to the polymer to
ligands which specifically bind to particular tissue types or cell
surface molecules. Additionally, ligands may be attached to the
microparticles which effect the charge, lipophilicity or
hydrophilicity of the particle.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Methods are provided for the synthesis of polymeric delivery
systems consisting of polymer matrices that contain an active
agent, such as a therapeutic or prophylactic agent (referred to
herein generally as "drug"). The matrices are useful in a variety
of drug delivery applications, and can be administered by
injection, aerosol or powder, orally, or topically. A preferred
route of administration is via the pulmonary system or by
injection. The incorporation of a hydrophobic and/or amphiphilic
compound (referred to generally herein as "hydrophobic compound")
into the polymeric matrix modifies the period of drug release as
compared with the same polymeric matrix without the incorporated
hydrophobic compound, by altering the rate of diffusion of water
into and out of the matrix and/or the rate of degradation of the
matrix.
[0013] Reagents for Making Matrix Having Hydrophobic Compound
Incorporated Therein
[0014] As used herein, the term "matrix" refers to a structure
including one or more materials in which a drug is dispersed,
entrapped, or encapsulated. The material can be crystalline,
semi-crystalline, or amorphous. The matrix can be in the form of
pellets, tablets, slabs, rods, disks, hemispheres, or
microparticles, or be of an undefined shape. As used herein, the
term microparticle includes microspheres and microcapsules, as well
as microparticles, unless otherwise specified. Microparticles may
or may not be spherical in shape. Microcapsules are defined as
microparticles having an outer polymer shell surrounding a core of
another material, in this case, the active agent. Microspheres are
generally solid polymeric spheres, which can include a honeycombed
structure formed by pores through the polymer which are filled with
the active agent, as described below.
[0015] Polymers
[0016] The matrix can be formed of non-biodegradable or
biodegradable matrices, although biodegradable matrices are
preferred, particularly for parenteral administration. Non-erodible
polymers may be used for oral administration. In general, synthetic
polymers are preferred due to more reproducible synthesis and
degradation, although natural polymers may be used and have
equivalent or even better properties, especially some of the
natural biopolymers which degrade by hydrolysis, such as
polyhydroxybutyrate. The polymer is selected based on the time
required for in vivo stability, i.e. that time required for
distribution to the site where delivery is desired, and the time
desired for delivery.
[0017] Representative synthetic polymers are: poly(hydroxy acids)
such as poly(lactic acid), poly(glycolic acid), and poly(lactic
acid-co-glycolic acid), poly(lactide), poly(glycolide),
poly(lactide-co-glycolide), polyanhydrides, polyorthoesters,
polyamides, polycarbonates, polyalkylenes such as polyethylene and
polypropylene, polyalkylene glycols such as poly(ethylene glycol),
polyalkylene oxides such as poly(ethylene oxide), polyalkylene
terepthalates such as poly(ethylene terephthalate), polyvinyl
alcohols, polyvinyl ethers, polyvinyl esters, polyvinyl halides
such as poly(vinyl chloride), polyvinylpyrrolidone, polysiloxanes,
poly(vinyl alcohols), poly(vinyl acetate), polystyrene,
polyurethanes and co-polymers thereof, derivativized celluloses
such as alkyl cellulose, hydroxyalkyl celluloses, cellulose ethers,
cellulose esters, nitro celluloses, methyl cellulose, ethyl
cellulose, hydroxypropyl cellulose, hydroxy-propyl methyl
cellulose, hydroxybutyl methyl cellulose, cellulose acetate,
cellulose propionate, cellulose acetate butyrate, cellulose acetate
phthalate, carboxylethyl cellulose, cellulose triacetate, and
cellulose sulphate sodium salt (jointly referred to herein as
"synthetic celluloses"), polymers of acrylic acid, methacrylic acid
or copolymers or derivatives thereof including esters, poly(methyl
methacrylate), poly(ethyl methacrylate), poly(butylmethacrylate,
poly(isobutyl methacrylate), poly(hexylmethacrylate), poly(isodecyl
methacrylate), poly(lauryl methacrylate), poly(phenyl
methacrylate), poly(methyl acrylate), poly(isopropyl acrylate),
poly(isobutyl acrylate), and poly(octadecyl acrylate) (jointly
referred to herein as "polyacrylic acids"), poly(utyric acid),
poly(valeric acid), and poly(lactide-co-caprolactone), copolymers
and blends thereof. As used herein, "derivatives" include polymers
having substitutions, additions of chemical groups, for example,
alkyl, alkylene, hydroxylations, oxidations, and other
modifications routinely made by those skilled in the art.
[0018] Examples of preferred biodegradable polymers include
polymers of hydroxy acids such as lactic acid and glycolic acid,
and copolymers with PEG, polyanhydrides, poly(ortho)esters,
polyurethanes, poly(butyric acid), poly(valeric acid),
poly(lactide-co-caprolactone), blends and copolymers thereof.
[0019] Examples of preferred natural polymers include proteins such
as albumin and prolamines, for example, zein, and polysaccharides
such as alginate, cellulose and polyhydroxyalkanoates, for example,
polyhydroxybutyrate. The in vivo stability of the matrix can be
adjusted during the production by using polymers such as
polylactide co glycolide copolymerized with polyethylene glycol
(PEG). PEG if exposed on the external surface may elongate the time
these materials circulate since it is hydrophhilic.
[0020] Examples of preferred non-biodegradable polymers include
ethylene vinyl acetate, poly(meth)acrylic acid, polyamides,
copolymers and mixtures thereof.
[0021] Bioadhesive polymers of particular interest for use in
targeting of mucosal surfaces, as in the gastrointestinal tract,
include polyanhydrides, polyacrylic acid, poly(methyl
methacrylates), poly(ethyl methacrylates), poly(butylmethacrylate),
poly(isobutyl methacrylate), poly(hexylmethacrylate), poly(isodecyl
methacrylate), poly(lauryl methacrylate), poly(phenyl
methacrylate), poly(methyl acrylate), poly(isopropyl acrylate),
poly(isobutyl acrylate), and poly(octadecyl acrylate).
[0022] Solvents
[0023] A solvent for the polymer is selected based on its
biocompatibility as well as the solubility of the polymer and where
appropriate, interaction with the agent to be delivered. For
example, the ease with which the agent is dissolved in the solvent
and the lack of detrimental effects of the solvent on the agent to
be delivered are factors to consider in selecting the solvent.
Aqueous solvents can be used to make matrices formed of water
soluble polymers. Organic solvents will typically be used to
dissolve hydrophobic and some hydrophilic polymers. Preferred
organic solvents are volatile or have a relatively low boiling
point or can be removed under vacuum and which are acceptable for
administration to humans in trace amounts, such as methylene
chloride. Other solvents, such as ethyl acetate, ethanol, methanol,
dimethyl formamide (DMF), acetone, acetonitrile, tetrahydrofuran
(THF), acetic acid, dimethyle sulfoxide (DMSO) and chloroform, and
combinations thereof, also may be utilized. Preferred solvents are
those rated as class 3 residual solvents by the Food and Drug
Administration, as published in the Federal Register vol. 62,
number 85, pp. 24301-24309 (May 1997).
[0024] In general, the polymer is dissolved in the solvent to form
a polymer solution having a concentration of between 0.1 and 60%
weight to volume (w/v), more preferably between 0.25 and 30%. The
polymer solution is then processed as described below to yield a
polymer matrix having hydrophobic components incorporated
therein.
[0025] Hydrophobic and Amphiphilic Compounds
[0026] In general, compounds which are hydrophobic or amphiphilic
(i.e., including both a hydrophilic and a hydrophobic component or
region) can be used to modify penetration and/or uptake of water by
the matrix, thereby modifying the rate of diffusion of drug out of
the matrix, and in the case of hydrolytically unstable materials,
alter degradation and thereby release of drug from the matrix.
[0027] Lipids which may be used include, but are not limited to,
the following classes of lipids: fatty acids and derivatives,
mono-, di and triclycerides, phospholipids, sphingolipids,
cholesterol and steroid derivatives, terpenes and vitamins. Fatty
acids and derivatives thereof may include, but are not limited to,
saturated and unsaturated fatty acids, odd and even number fatty
acids, cis and trans isomers, and fatty acid derivatives including
alcohols, esters, anhydrides, hydroxy fatty acids and
prostaglandins. Saturated and unsaturated fatty acids that may be
used include, but are not limited to, molecules that have between
12 carbon atoms and 22 carbon atoms in either linear or branched
form. Examples of saturated fatty acids that may be used include,
but are not limited to, lauric, myristic, palmitic, and steariac
acids. Examples of unsaturated fatty acids that may be used
include, but are not limited to, lauric, physeeric, myristoleic,
palmitoleic, petroselinic, and oleic acids. Examples of branched
fatty acids that may be used include, but are not limited to,
isolauric, isomyristic, isopalmitic, and isostearaic acids and
isoprenoids. Fatty acids derivatives include
12-(((7'-diethylaminocoumarin-3
yl)carbonyl)methylamino)-ocadecanoic acid;
N-[12-(((7'diethylaminocoumarin-3-yl) carbonyl)methyl-amino)
octadecanoyl]-2-aminopalmitic acid, N
succinyl-dioleoylphosphatidylethanol amine and
palmitoyl-homocysteine; and/or combinations thereof. Mono, di and
triclycerides or derivatives thereof that may be used include, but
are not limited to, molecules that have fatty acids or mixtures of
fatty acids between 6 and 24 carbon atoms, digalactosyldiglyceride,
1,2-dioleoyl-sn-glycerol;1,2-cdipalmitoyl-sn-3 succinylglycerol;
and 1,3-dipalmitoyl-2-succinylglycerol.
[0028] Phospholipids which may be used include, but are not limited
to, phosphatidic acids, phosphatidyl cholines with both saturated
and unsaturated lipids, phosphatidyl ethanolamines,
lysophosphatidyl derivatives, cardiolipin, and .beta.-acyl-y-alkyl
phospholipids. Examples of phospholipids include, but are not
limited to, phosphatidylcholines such as
dioleoylphosphatidylcholine, dimyristoylphosphatidylcholine,
cipentadecanoylphosphatidylcholine dilauroylphosphatidylcholine,
dipalmitoylphosphatidylcholine (DPPC),
distearoylphosphatidylcholine (DSPC),
diarachidoylphosphatidylcholine (DAPC),
dibehenoylphosphatidylcholine (DBPC),
ditricosanoylphosphatidylcholine (DTPC),
dilignoceroylphatidylcholine (DLPC); and phosphatidylethanolamines
such as dioleoylphosphatidylethanolamine or
1-hexadecyl-2-palmitoylglycerophosphoethanolamine. Synthetic
phospholipids with asymmetric acyl chains (e.g., with one acyl
chain of 6 carbons and another acyl chain of 12 carbons) may also
be used.
[0029] Sphingolipids which may be used include ceramides,
sphingomyelins, cerebrosides, gangliosides, sulfatides and
lysosulfatides. Examples of Sphinglolipids include, but are not
limited to, the gangliosides GM1 and GM2.
[0030] Steroids which may be used include, but are not limited to,
cholesterol, cholesterol sulfate, cholesterol hemisuccinate,
6-(5-cholesterol 3.beta.-yloxy)
hexyl-6-amino-6-deoxy-1-thio-.alpha.-D-galactopyranoside,
6-(5-cholesten-3
.beta.-tloxy)hexyl-6-amino-6-deoxyl-1-thio-.alpha.-D
mannopyranoside and cholesteryl)4'-trimethyl 35
ammonio)butanoate.
[0031] Additional lipid compounds which may be used include
tocopherol and derivatives, and oils and derivatized oils such as
stearlyamine.
[0032] A variety of cationic lipids such as DOTMA,
N-[1-(2,3-dioleoyloxy)propyl-N,N,N-trimethylammonium chloride;
DOTAP, 1,2-dioleoyloxy-3-(trimethylammonio) propane; and DOTB,
1,2-dioleoyl-3-(4'-trimethyl-ammonio) butanoyl-sn glycerol may be
used.
[0033] The most preferred lipids are phospholipids, preferably
DPPC, DAPC, DSPC, DTPC, DBPC, DLPC and most preferably DPPC, DAPC
and DBPC.
[0034] Other preferred hydrophobic compounds include amino acids
such as tryptophane, tyrosine, isoleucine, leucine, and valine,
aromatic compounds such as an alkyl paraben, for example, methyl
paraben, and benzoic acid.
[0035] The content of hydrophobic compound ranges from 0.01-60 (w
hydrophobic compound /w polymer); most preferably between 0.01-30
(w hydrophobic compound /w polymer).
[0036] Targeting
[0037] Microparticles can be targeted specifically or
non-specifically through the selection of the polymer forming the
microparticle, the size of the microparticle, and/or incorporation
or attachment of a ligand to the microparticles. For example,
biologically active molecules, or molecules affecting the charge,
lipophilicity or hydrophilicity of the particle, may be attached to
the surface of the microparticle. Additionally, molecules may be
attached to the microparticles which minimize tissue adhesion, or
which facilitate specific targeting of the microparticles in vivo.
Representative targeting molecules include antibiotics, lectins,
and other molecules which are specifically bound by receptors on
the surfaces of cells of a particular type.
[0038] Inhibition of Uptake by the RES
[0039] Uptake and removal of the microparticles can be minimized
through the selection of the polymer and/or incorporation or
coupling of molecules which minimize adhesion or uptake. For
example, tissue adhesion by the microparticle can be minimized by
covalently binding poly(alkylene glycol) moieties have a high
affinity for water that reduces protein adsorption onto the surface
of the particle. The recognition and uptake of the microparticle by
the reticulo-endothelial system (RES) is therefore reduced.
[0040] In one method, the terminal hydroxyl group of the
poly(alkylene glycol) is covalently attached to biologically active
molecules, or molecules affecting the charge, lipophilicity or
hydrophilicity of the particle, onto the surface of the
microparticle. Methods available in the art can be used to attach
any of a wide range of ligands to the microparticles to enhance the
delivery properties, the stability or other properties of the
microparticles in vivo.
[0041] Active Agents
[0042] Active agents which can be incorporated into the matrix for
delivery include therapeutic or prophylactic agents. These can be
proteins or peptides, sugars, oligosaccharides, nucleic acid
molecules, or other synthetic or natural agents. The agents may be
labeled with a detectable label such as a fluorescent label or an
enzymatic or chromatographically detectable agent.
[0043] Preferred drugs include antibiotics, antivirals, vaccines,
vasodilators, vasoconstrictors, immunomodulatory compounds,
including steroids, antihistamines, and cytokines such as
interleukins, colony stimulating factors, tumor necrosis factor and
interferon (.alpha., .beta., .gamma.), oligonucleotides including
genes and antisense, nucleases, bronchodilators, hormones including
reproductive hormones, calcitonin, insulin, erthropoietin, growth
hormones, and other types of drugs such as Antiban.TM..
[0044] Methods for Manufacture of Matrix
[0045] In the most preferred embodiment, microparticles are
produced by spray drying. Techniques which can be used to make
other types of matrices, as well as microparticles, include melt
extrusion, compression molding, fluid bed drying, solvent
extraction, hot melt encapsulation, and solvent evaporation, as
discussed below. A major criteria is that the hydrophobic compound
must be dissolved or melted with the polymer or dispersed as a
solid or a liquid in a solution of the polymer, prior to forming
the matrix. As a result, the hydrophobic (or amphiphilic) compound
is mixed throughout the matrix, in a relatively uniform manner, not
just on the surface of the finished matrix. The active agent can be
incorporated into the matrix as solid particles, as a liquid or
liquid droplets, or by dissolving the agent in the polymer
solvent.
[0046] a. Solvent Evaporation. In this method the polymer and
hydrophobic compound are dissolved in a volatile organic solvent
such as methylene chloride. A pore forming agent as a solid or as a
liquid may be added to the solution. The active agent can be added
as either a solid or in solution to the polymer solution. The
mixture is sonicated or homogenized and the resulting dispersion or
emulsion is added to an aqueous solution that may contain a surface
active agent such as TWEEN.TM. 20, TWEEN.TM. 80, PEG or poly(vinyl
alcohol) and homogenized to form an emulsion. The resulting
emulsion is stirred until most of the organic solvent evaporates,
leaving microparticles. Several different polymer concentrations
can be used (0.05-0.60 g/ml). Microparticles with different sizes
(1-1000 microns) and morphologies can be obtained by this method.
This method is particularly useful for relatively stable polymers
like polyesters.
[0047] Solvent evaporation is described by E. Mathiowitz, et al.,
J. Scanning Microscopy, 4, 329 (1990); L. R. Beck, et al., Fertil.
Steril., 31, 545 (1979); and S. Benita, et al., J. Pharm. Sci., 73,
1721 (1984), the teachings of which are incorporated herein.
[0048] Particularly hydrolytically unstable polymers, such as
polyanhydrides, may degrade during the fabrication process due to
the presence of water. For these polymers, the following two
methods, which are performed in completely organic solvents, are
more useful.
[0049] b. Hot Melt Microencapsulation. In this method, the polymer
and the hydrophobic compound are first melted and then mixed with
the solid or liquid active agent. A pore forming agent as a solid
or in solution may be added to the solution. The mixture is
suspended in a non-miscible solvent (like silicon oil), and, while
stirring continuously, heated to 5.degree. C. above the melting
point of the polymer. Once the emulsion is stabilized, it is cooled
until the polymer particles solidify. The resulting microparticles
are washed by decantation with a polymer non-solvent such as
petroleum ether to give a free-flowing powder. Microparticles with
sizes between one to 1000 microns can be obtained with this method.
The external surfaces of particles prepared with this technique are
usually smooth and dense. This procedure is used to prepare
microparticles made of polyesters and polyanhydrides. However, this
method is limited to polymers with molecular weights between
1000-50,000.
[0050] Hot-melt microencapsulation is described by E. Mathiowitz,
et al., Reactive Polymers, 6, 275 (1987), the teachings of which
are incorporated herein. Preferred polyanhydrides include
polyanhydrides made of biscarboxyphenoxypropane and sebacic acid
with molar ratio of 20:80 (P(CPP-SA) 20:80) (Mw 20,000) and
poly(fumaric-co-sebacic) (20:80) (MW 15,000) microparticles.
[0051] c. Solvent Removal. This technique was primarily designed
for polyanhydrides. In this method, the solid or liquid active
agent is dispersed or dissolved in a solution of the selected
polymer and hydrophobic compound in a volatile organic solvent like
methylene chloride. This mixture is suspended by stirring in an
organic oil (such as silicon oil) to form an emulsion. Unlike
solvent evaporation, this method can be used to make microparticles
from polymers with high melting points and different molecular
weights. The external morphology of particles produced with this
technique is highly dependent on the type of polymer used.
[0052] d. Spray Drying of Microparticles. Microparticles can be
produced by spray drying by dissolving a biocompatible polymer and
hydrophobic compound in an appropriate solvent, dispersing a solid
or liquid active agent into the polymer solution, and then spray
drying the polymer solution, to form microparticles. As defined
herein, the process of "spray drying" a solution of a polymer and
an active agent refers to a process wherein the solution is
atomized to form a fine mist and dried by direct contact with hot
carrier gases. Using spraying drying apparatus available in the
art, the polymer solution may be delivered through the inlet port
of the spray drier, passed through a tube within the drier and then
atomized through the outlet port. The temperature may be varied
depending on the gas or polymer used. The temperature of the inlet
and outlet ports can be controlled to produce the desired
products.
[0053] The size of the particulates of polymer solution is a
function of the nozzle used to spray the polymer solution, nozzle
pressure, the flow rate, the polymer used, the polymer
concentration, the type of solvent and the temperature of spraying
(both inlet and outlet temperature) and the molecular weight.
Generally, the higher the molecular weight, the larger the particle
size, assuming the concentration is the same. Typical process
parameters for spray drying are as follows: polymer
concentration=0.005-0.20 g/ml, inlet temperature=20-1000.degree.
C., outlet temperature =10-300.degree. C., polymer flow rate=5-2000
ml/min., and nozzle diameter=0.2-4 mm ID. Microparticles ranging in
diameter between one and ten microns can be obtained with a
morphology which depends on the selection of polymer,
concentration, molecular weight and spray flow.
[0054] If the active agent is a solid, the agent may be
encapsulated as solid particles which are added to the polymer
solution prior to spraying, or the agent can be dissolved in an
aqueous solution which then is emulsified with the polymer solution
prior to spraying, or the solid may be cosolubilized together with
the polymer in an appropriate solvent prior to spraying.
[0055] e. Hydrogel Microparticles. Microparticles made of gel-type
polymers, such as polyphosphazene or polymethylmethacrylate, are
produced by dissolving the polymer in an aqueous solution,
suspending if desired a pore forming agent and suspending a
hydrophobic compound in the mixture, homogenizing the mixture, and
extruding the material through a microdroplet forming device,
producing microdroplets which fall into a hardening bath consisting
of an oppositely charged ion or polyelectrolyte solution, that is
slowly stirred. The advantage of these systems is the ability to
further modify the surface of the microparticles by coating them
with polycationic polymers, like polylysine after fabrication.
Microparticle particles are controlled by using various size
extruders.
[0056] Additives to Facilitate Matrix Formation
[0057] A variety of surfactants may be added to the continuous
phase as emulsifiers if one is used during the production of the
matrices. Exemplary emulsifiers or surfactants which may be used
(0.1-5% by weight) include most physiologically acceptable
emulsifiers. Examples include natural and synthetic forms of bite
salts or bile acids, both conjugated with amino acids and
unconjugated such as taurodeoxycholate, and cholic acid. In
contrast to the methods described herein, these surfactant will
coat the microparticle and will facilitate dispersion for
administration.
[0058] Pore Forming Agents
[0059] ore forming agents can be included in an amount of between
0.01% and 90% weight to volume, to increase matrix porosity and
pore formation during the production of the matrices. The pore
forming agent can be added as solid particles to the polymer
solution or melted polymer or added as and aqueous solution which
is emulsified with the polymer solution or is co-dissolved in the
polymer solution. For example, in spray drying, solvent
evaporation, solvent removal, hot male encapsulation, a pore
forming agent such as a volatile salt, for example, ammonium
bicarbonate, ammonium acetate, ammonium chloride or ammmonium
benzonate or other lyophilizable salt, is first dissolved in water.
The solution containing the pore forming agent is then emulsified
with the polymer solution to create droplets of the pore forming
agent in the polymer. This emulsion is then spray dried or taken
through a solvent evaporation/extraction process. After the polymer
is precipitated, the hardened microparticles can be frozen and
hypholized to remove any pore forming agents not removed during the
microencapsulation process.
[0060] Methods for Administration of Drug Delivery Systems
[0061] The matrix can be administered orally, topically, to a
mucosal surface (i.e., nasal, pulmonary, vaginal, rectal), or by
implantation or injection, depending on the form of the matrix and
the agent to be delivered. Useful pharmaceutically acceptable
carriers include saline containing glycerol and TWEEN.TM. 20 and
isotonic mannitol containing TWEEN.TM. 20. The matrix can also be
in the form of powders, tablets, in capsules, or in a topical
formulation such as an ointment, gel or lotion.
[0062] Microparticles can be administered as a powder, or
formulated in tablets or capsules, suspended in a solution or in a
gel (ointment, lotion, hydrogel). As noted above, the size of the
microparticles is determined by the method of administration. In
the preferred embodiment, the microparticles are manufactured with
a diameter of between 0.5 and 8 microns for intravascular
administration, a diameter of 1-100 microns for subcutaneous or
intramuscular administration, and a diameter of between 0.5 and 5
mm for oral administration for delivery to the gastrointestinal
tract or other lumens, or application to other mucosal surfaces
(rectal, vaginal, oral, nasal). A preferred size for administration
to the pulmonary system is an aerodynamic diameter of between one
and three microns, with an actual diameter of five microns or more,
as described in U.S. Pat. No. U.S. Pat. No. 5,855,913, which issued
on Jan. 5, 1999, to Edwards, et al. Particle size analysis can be
performed on a Coulter counter, by light microscopy, scanning
electron microscopy, or transmittance electron microscopy.
[0063] In the preferred embodiment, microparticles are combined
with a pharmaceutically acceptable carrier such as phosphate
buffered saline or saline or mannitol, then an effective amount
administered to a patient using an appropriate route, typically by
injection into a blood vessel (i.v.), subcutaneously,
intramuscularly (IM) or orally. Microparticles containing an active
agent may be used for delivery to the vascular system, as well as
delivery to the liver and renal systems, in cardiology
applications, and in treating tumor masses and tissues. For
administration to the pulmonary system, the microparticles can be
combined with pharmaceutically acceptable bulking agents and
administered as a dry powder. Pharmaceutically acceptable bulking
agents include sugars such as mannitol, sucrose, lactose, fructose
and trehalose. The microparticles also can be linked with ligands
that minimize tissue adhesion or that target the microparticles to
specific regions of the body in vivo as described above.
[0064] The methods and compositions described above will be further
understood with reference to the following non-limiting
examples.
EXAMPLE 1
Preparation of PLGA:DAPC Drug Delivery Particles
[0065] 30 grams of PLGA (50:50) (IV 0.4 dL/g Boehringer Ingelheim),
1.8 g of diarachidoylphosphatidylcholine (Avanti, Birmingham, Ala.)
and 495 mg of Azure A (Sigma Chemicals, St. Louis, Mo.) were
dissolved in 1000 ml of methylene chloride. The solution was pumped
at a flowrate of 20 mL/min and spray dried using a Bucchi Lab spray
dryer. The inlet air temperature was 40.degree. C. The dried
microparticle powder was collected and stored at -20.degree. C.
until analysis. Size of the microparticles was performed using a
Coulter multisizer II. The microparticles have a volume average
mean diameter of 5.982 microns.
[0066] 18 grams of PLGA (50:50) (IV 0.4 dL/g Boehringer Ingelheim)
and 1.08 g of diarachidoylphosphatidylcholine (Avanti, Birmingham,
Ala.) were dissolved in 600 mL of methylene chloride. 38.9 mg of
Eosin Y (Sigma Chemicals) was dissolved in 38.9 mL of a 0.18 g/ml
ammonium bicarbonate solution. The eosin solution was emulsified
with the polymer solution using a Silverson homogenizer at 7000 rpm
for 8 minutes. The solution was pumped at a flowrate of 20 mL/min
and spray dried using a Bucchi Lab spray dryer. The inlet air
temperature was 40.degree. C. The dried microparticle powder was
collected and stored at -20.degree. C. until analysis. Size
analysis of the microparticles was performed using a Coulter
multisizer II. The microparticles have a volume average mean
diameter of 6.119 microns.
[0067] Modifications and variations of the present invention will
be obvious to those skilled in the art from the foregoing detailed
description and are intended to come within the scope of the
following claims.
* * * * *