Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
1999-02-22
2002-07-23
Webman, Edward J. (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S499000, C424S484000, C424S486000, C424S487000, C424S488000
Reexamination Certificate
active
06423345
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
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.
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.
It is an object of this invention to provide microparticles which have incorporated therein means for limiting diffusion of drug out of the microparticle.
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.
It is still another object of the present invention to provide microparticles particularly well suited for parenteral drug delivery.
SUMMARY OF THE INVENTION
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.
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 0.5 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-glyolic acid, polylactide, polyglycolide or polyactide co-glycolide, which may be conjugated to polyethylene glycol or other materials inhibiting uptake by the reticuloendothelial system (RES).
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), diarachidoylphosphatidylcholine (DAPC), dibehenoylphosphatidylcholine (DBPC), ditricosanoylphosphatidylcholine (DTPC), and dilignoceroylphatidylcholine (DLPC), incorporated at a ratio of between 0.01-60 (w/w polymer), most preferably between 0.1-30 (w lipid/w polymer).
Surface properties of the matrix can also be 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
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.
Reagents for Making Matrix Having Hydrophobic Compound Incorporated Therein
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.
Polyme
Bernstein Howard
Chickering Donald
Khattak Sarwat
Straub Julie
Acusphere, Inc.
Holland & Knight LLP
Pabst Patrea L.
Webman Edward J.
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