Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
2000-01-04
2002-05-14
Dees, Jose′ G. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S401000
Reexamination Certificate
active
06387409
ABSTRACT:
This application claims benefit of provisional application Ser. No. 60/079,809 filed Mar. 30, 1998, the disclosure of which is hereby incorporated by reference.
This invention relates to compositions and procedures that yield sub-micron and micron-size stable particles of water-insoluble or poorly soluble drugs or other industrially useful insoluble compounds. The compositions of this invention include combinations of natural or synthetic phospholipids, a charged surface modifier such as a highly purified charged phospholipid and a block copolymer coated or adhered onto the surfaces of the water insoluble-compound particles. The combination of charged surface modifier and block copolymer allows the formation and stabilization of the sub-micron and micron size compound particles—stabilized by the charged phospholipid surface modifiers to provide electrostatic stabilization and the block copolymer to provide steric stabilization—and therefore prevent these particles from particle growth, aggregation or flocculation.
BACKGROUND OF THE INVENTION
There is a critical need in the pharmaceutical and other biological based industries to formulate water-insoluble or poorly soluble substances into formulations for oral, injectable, inhalation and ophthalmic routes of delivery. Water insoluble compounds are those having poor solubility in water, that is <5 mg/ml at physiological pH (6.5-7.4). Preferably their water solubility is <1 mg/ml, more preferably <0.1 mg/ml. It is desirable that the drug is stable in water as a dispersion; otherwise a lyophilized or spray-dried solid form may be desirable.
As used herein, “micro” refers to a particle having diameter of from nanometers to micrometers. Microparticles, as used herein, refer to solid particles of irregular, non-spherical or spherical shapes. Formulations containing these microparticles provide some specific advantages over the unformulated non-micronized drug particles, which include improved oral bioavailability of drugs that are poorly absorbed from GI tract, development of injectable formulations that are currently available only in oral dosage form, less toxic injectable formulations that are currently prepared with organic solvents, sustained release of intramuscular injectable drugs that are currently administered through daily injection or constant infusion, and preparation of inhaled, ophthalmic formulation of drugs that otherwise could not be formulated for nasal or ocular use.
Current technology for delivering insoluble drugs as described in U.S. Pat. Nos. 5,091,188; 5,091,187 and 4,725,442 focuses on (a) either coating small drug particles with natural or synthetic phospholipids or (b) dissolving the drug in a suitable lipophilic carrier and forming an emulsion stabilized with natural or semisynthetic phospholipids. One of the disadvantages of these formulations is that certain drug particles in suspension tend to grow over time because of the dissolution and reprecipitation phenomenon known as the “Oswald ripening” or particle growth, as the solvent becomes saturated with solute, the larger particles grow and become even larger, Luckham, Pestic. Sci., (1999) 25, 25-34.
Another approach, as described in a series of patents uses a cloud point modifier(s). In U.S. Pat. Nos. 5,298,262; 5,326,552; 5,336,507; 5,304,564 and 5,470,583 a poorly soluble drug or diagnostic agent has adsorbed on its surface both a cloud-point modifier and a non-crosslinked nonionic surfactant. The role of the cloud point modifier is to increase the cloud point of the surfactant such that the resulting nanoparticles are resistant to particle size growth upon heat sterilization at 121° C.
DESCRIPTION OF THE INVENTION
The present invention focuses on preparing submicron to micron size particles using a combination of electrostatic and steric stabilization using at least one charged surface modifier and at least one block copolymer, with particles coated with a natural phospholipid. In this manner the growth of particle size, and hence storage stability, is controlled by adding a combination of electrostatic and steric stabilizing materials.
The use of this particular combination of electrostatic and steric stabilizers in addition to a natural phospholipid is characterized by its ability to result in volume weighted mean particle size values that are smaller than what can be achieved using phospholipid alone without the use of a surfactant with the same energy input, and provide compositions resistant to particle size growth on storage. In order to achieve the advantages of the present invention it is necessary that the natural phospholipid and stabilizers all be present at the time of particle size reduction or precipitation.
Another aspect of the present invention includes free-flowing powders of poorly soluble or insoluble drug substances such as cyclosporin as well as solid dosage forms of these powders, for instance in the form of compressed tablets and the like. Surprisingly we have found that microparticle formulations exhibit enhanced stability as illustrated in the data that follows.
Although we do not wish to be bound by any particular theory, it appears that these surface modifiers generally, that is phospholipids and one or more surfactants, adsorb to the surfaces of drug particles, and (a) convert lipophilic to hydrophilic surfaces with increased steric hindrance/stability, and (b) possibly modify zeta potential of surfaces with more charge repulsion stabilization. The concentrations of surface modifiers used in the process described here are normally above their critical micelle concentrations (CMC) and hence facilitate the formation of sub-micron to micron particles by stabilizing the small particles as they are formed to prevent reaggregation.
Phospholipid and surface modifier(s) are adsorbed onto the surfaces of drug particles in sufficient quantity to retard drug particle growth, reduce drug average particle size from 5 to 100 &mgr; to sub-micron and micron size particles by one or combination of methods known in the art, such as sonication, homogenization, milling, microfluidization, precipitation or recrystallization or precipitation from supercritical fluid, and maintain sub-micron and micron size particles on subsequent storage as suspension or solid dosage form.
The formulations prepared by this invention may be dried, e.g., by lyophilization, fluid or spray drying, into powders, which can be resuspended or filled into capsules or converted into granules or tablets with the addition of binders and other excipients known in the art of tablet making.
By industrially useful insoluble or poorly soluble compounds we include biologically useful compounds, imaging agents, pharmaceutically useful compounds and in particular drugs for human and veterinary medicine. Water insoluble compounds are those having a poor solubility in water, that is less than 5 mg/ml at a near neutral pH of 5 to 8, although the water solubility may be less than 1 mg/ml and even less than 0.1 mg/ml.
Examples of some preferred water-insoluble drugs include immunosuppressive agents such as cyclosporins including cyclosporine (cyclosporin A), immunoactive agents, antiviral and antifungal agents, antineoplastic agents, analgesic and anti-inflammatory agents, antibiotics, anti-epileptics, anesthetics, hypnotics, sedatives, antipsychotic agents, neuroleptic agents, antidepressants, anxiolytics, anticonvulsant agents, antagonists, neuron blocking agents, anticholinergic and cholinomimetic agents, antimuscarinic and muscarinic agents, antiadrenergic and antiarrhythmics, antihypertensive agents, hormones, and nutrients. A detailed description of these and other suitable drugs may be found in
Remington's Pharmaceutical Sciences,
18th edition, 1990, Mack Publishing Co. Philadelphia, Pa.
The phospholipid may be any naturally occurring phospholipid or mixtures of phospholipids, sometimes referred to herein as “commercial” phospholipids, such as egg or soybean phospholipid or a combination thereof. The phospholipid may be salted or desalted, hydrogenated or parti
Khan Sheema
Pace Gary W.
Dees Jose′ G.
George Konata M.
Nixon & Vanderhye
RTP Pharma Inc.
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