Patent Application
20080299210
The present invention relates to methods and compositions that provide improved solubility of poorly soluble drugs. More particularly, the invention relates to populations of nanoparticles and related methods that provide improved solubility of poorly soluble drugs.
Lead compounds that are currently being developed using combinatorial chemistry and other high throughput techniques often demonstrate very poor solubility. This may be in part because pharmaceutical companies may choose to screen first for activity against a target, and only then for pharmacokinetic properties. This can lead to discovery of very active compounds that are not particularly good orally dosed drugs.
If new drug leads have poor solubility, this may lead to poor oral absorption from the gastrointestinal tract. Poor oral absorption leads to poor bioavailability, and consequently poor drug performance.
These problems have been recognized in the industry. See M. Kataoka et al., “In Vitro System to Evaluate Oral Absorption of Poorly Water-Soluble Drugs: Simultaneous Analysis on Dissolution and Permeation of Drugs,” Pharm. Res. 20(10):1674-1680 (2003).
Development of new technologies to improve solubility has generated scientific interest, resulting in a large array of new systems that can be applied to compounds with intrinsically low solubility with associated poor dissolution performance. K. R. Horspool et al., “Advancing new drug delivery concepts to gain the lead.” Drug Delivery Technology 3:34-46 (2003) (“Horspool”). Horspool goes on to say:
U.S. Pat. No. 5,145,684 to Liversidge et al. discloses crystalline nanoparticles having a surface modifier adsorbed onto the surface of the nanoparticles. This patent does not disclose amorphous nanoparticles.
U.S. Pat. No. 6,656,504 to Bosch et al. and U.S. Published Patent Application 2002/0016290 to Floc'h et al. disclose nanoparticulate amorphous cyclosporine formulations. However, cyclosporine takes on an amorphous form quite easily and doesn't have a very stable crystalline form. This property is in contrast to most other poorly water-soluble drugs. The glass forming ability (GFA) of cyclosporine is greater than about 0.85.
Amorphous nanoparticles are disclosed in K. Chari et al., Effect of Poly(vinylpyrrolidone) on Transformation of the Dispersed Phase and Gelation in a Lyophobic Colloid System, J. Phys. Chem. 97:2640-2645 (1993) (“Chari 1”), and K. Chari et al., Dispersed Phase Microstructure in a Colloid Gel, J. Phys. Chem 98:5125-5126 (1994) (“Chari 2”). However, these nanoparticle populations are not very stable, with changes apparent after 20 days in Chari 1, and after one week in Chari 2.
Amorphous nanoparticles are also disclosed in K. Chari et al., Polymer-Surfactant Interaction and Stability of Amorphous Colloidal Particles, J. Phys. Chem B. 103:9867-9872 (1999). While the paper shows data that suggest that the size of the nanoparticles may remain relatively stable over one year, there is no evidence presented that the nanoparticles actually retain their amorphous stability over the year.
Although amorphous nanoparticles can be obtained by precipitation, the stability of amorphous nanoparticles made by this method is still fundamentally unsolved because of the impurities (dopants) and defects in the particles. B. Rabinow, Nanosuspensions in Drug Delivery, Nature Rev. Drug Discovery 3:785-796(2004).
Accordingly, substances, compositions, dosage forms and methods that address the above noted problems in the art are needed.
In an aspect, the invention relates to a population of nanoparticles wherein one or more of the nanoparticles comprises: an amorphous drug core having an effective diameter less than or equal to about 2.0 microns, wherein the amorphous drug core is substantially free of dopant, and wherein the amorphous drug core comprises a drug with properties that satisfy the following relationships: a glass transition temperature greater than or equal to about 50 Deg. C., a glass forming ability less than or equal to about 0.85; and water solubility at 25 Deg. C. less than or equal to about 1 mg/ml; and at least one stabilizer adsorbed on a surface of the amorphous drug core; and wherein the population of nanoparticles exhibits greater than about six months amorphous stability.
In another aspect, the invention relates to a method of making a population of nanoparticles comprising: forming amorphous drug cores with an effective diameter less than or equal to about 2.0 microns, wherein the amorphous drug cores are substantially free of dopant, and wherein the amorphous drug cores comprise a drug with properties that satisfy the following relationships: a glass transition temperature greater than or equal to about 50 Deg. C., a glass forming ability less than or equal to about 0.85; and water solubility at 25 Deg. C. less than or equal to about 1 mg/ml; and adsorbing at least one stabilizer on a surface of the amorphous drug cores; wherein the population of nanoparticles exhibits greater than about six months amorphous stability.
The inventors have surprisingly found that the problems noted above can be solved by providing a population of nanoparticles, and methods of making such populations of nanoparticles, wherein one or more of the nanoparticles comprises: an amorphous drug core having an effective diameter less than or equal to about 2.0 microns, wherein the amorphous drug core is substantially free of dopant, and wherein the amorphous drug core comprises a drug with properties that satisfy the following relationships: a glass transition temperature greater than or equal to about 50 Deg. C., a glass forming ability less than or equal to about 0.85; and water solubility at 25 Deg. C. less than or equal to about 1 mg/ml; and at least one stabilizer adsorbed on a surface of the amorphous drug core; and wherein the population of nanoparticles exhibits greater than about six months amorphous stability.
Such populations of nanoparticles offer improved solubility and improved amorphous stability over crystalline nanoparticle formulations. As can be seen in Example 1, Table 2, even though crystalline nanoparticles may have a smaller particle size, populations of nanoparticles according to the invention may exhibit improved dissolution performance. This is further demonstrated by the results shown in Example 3,
All of these advantages represent significant improvements over the art.
The invention, and embodiments thereof, will now be described in more detail.
All percentages are weight percent unless otherwise noted.
All references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. The discussion of references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinence of the cited references.
The present invention is best understood by reference to the following definitions, the drawings and exemplary disclosure provided herein.
“Adsorbed” or “adsorption” means accumulated or accumulation on a surface of a solid, such as an amorphous drug core.
“Amorphous bulk material” means a portion of material, such as a drug, being larger than sub-micron in size and having generally amorphous properties. Methods of forming bulk materials are found elsewhere herein.
“Amorphous drug core” means a central portion of an inventive nanoparticle that comprises one or more drugs in a substantially amorphous state. An inventive amorphous drug core is substantially amorphous on its surface and in its interior. Accordingly, inventive populations of nanoparticles can be distinguished from populations of crystalline nanoparticles that may have an amorphous surface, due perhaps to the method of preparing such crystalline nanoparticles, but contain a highly crystalline interior. Of course, crystalline nanoparticles that have a crystalline surface and interior are also distinguishable from the inventive nanoparticles.
The amorphous state of the amorphous drug core is determined by subjecting a population of nanoparticles that comprise one or more nanoparticles that comprise the recited amorphous drug core to differential scanning calorimetry (DSC). In an embodiment, a DSC method according to the invention used a Perkin-Elmer DSC-7 or a Diamond DSC calorimeter applied for the measurement of specific transition temperatures of tested samples. Thus, the glass transition (Tg), melting (Tm) and crystallization (Tc) temperatures were measured for each sample, according to the PN-EN ISO 11357-1:2002 (ISO 11357-1:1997), ISO 11357-2:1999 and ISO 11357-3:1999 standards, at the rate of temperature change of 10 Deg C./min. The instrument was calibrated using indium, tin and zinc certified reference materials (CRMs)
The amorphous state of the amorphous drug core, as measured by DSC is expressed as a weight fraction of the weight of amorphous material in the amorphous drug core to the total weight of the amorphous drug core, expressed as an average value across the population of nanoparticles being measured. For instance, if a population of nanoparticles was measured using DSC, and the amorphous state was determined to be a particular value for the population, that value would be considered the average amorphous state for each nanoparticle within the population. An inventive amorphous drug core may contain a small amount of crystalline drug. In an embodiment, the amorphous drug core is substantially amorphous, preferably at least about 95% w/w amorphous, still more preferably at least about 98% w/w amorphous, even more preferably at least about 99% w/w amorphous, yet more preferably at least about 99.5% w/w amorphous, and most preferably at least about 99.9% w/w amorphous.
“Amorphous stability” means a measure of how much a material changes in its structure from being amorphous to being crystalline under defined conditions and a set timeframe. Amorphous materials such as a population of nanoparticles has amorphous stability if the weight fraction of amorphous material to total weight of the amorphous drug core changes by less than 10 percent, on an absolute basis, over 6 months at 25 degree C. For instance, an amorphous material that is initially 98% w/w amorphous is considered amorphously stable according to the invention if, at the end of 6 months testing at 25 degree C., the material is at least 88% w/w amorphous. The amorphous state of a material according to the invention is determined using a DSC method as detailed above and elsewhere herein.
In an embodiment, inventive nanoparticles exhibit greater than about 6 months stability, more preferably greater than about 9 months stability, still more preferably greater than about 12 months stability, yet more preferably greater than about 18 months stability, even more preferably greater than about 24 months stability.
“Dopant” means one or more substances added to another material in order to affect a physical property of the other material. The present invention discloses amorphous drug cores that are substantially free of dopant. In a preferred embodiment, the amorphous drug cores that are substantially free of dopant comprise amorphous drug cores containing less than about 15 weight percent dopant, more preferably less than about 10 weight percent dopant, still more preferably less than about 5 weight percent dopant, and yet more preferably less than about 1 weight percent dopant; all weight percentages being based on the total weight of the amorphous drug core.
“Drug(s)” means one or more biologically active substances that are useful or potentially useful in the treatment of various diseases, disorders, and the like. In a preferred embodiment, drugs useful in the practice of the invention comprise those drugs that fall in Biopharmaceutics Classification System (BCS) classes II and IV.
“Effective diameter” means a value such that at least 50% of a particle population has a weighted average particle size of less than the value, with the particle size measured using particle size measurement techniques known in the art. Effective diameter may be determined using a particle sizer, including but not limited to dynamic light scattering, laser light diffraction/scattering, atomic force microscopy (AFM), transmission electron microscopy (TEM), or scanning electron microscopy (SEM). In an embodiment, the effective diameter of an amorphous drug core according to the invention is less than or equal to about 2.0 microns, preferably less than or equal to about 1.5 micron, more preferably less than or equal to about 1.0 micron, and still preferably less than or equal to about 0.75 micron.
“Glass forming ability” or “GFA” means the ratio of Tg to Tm. It can be calculated as: GFA=Tg/Tm. GFA is a measure of the tendency of an amorphous drug to remain in an amorphous state. A higher GFA indicates an increased tendency for an amorphous drug to remain in an amorphous state. Drugs useful in the practice of the invention comprise those drugs having a GFA less than or equal to about 0.85. Preferably, the drugs have a GFA less than or equal to about 0.82, more preferably the drugs have a GFA less than or equal to about 0.77, and still more preferably the drugs have a GFA less than or equal to about 0.75.
“Glass transition temperature” or “Tg” means that temperature at which a material transitions to a glassy state from a liquid state, as measured at standard atmospheric pressure. Drugs useful in the practice of the invention comprise those drugs having a glass transition temperature greater than or equal to about 50 Deg. C. Preferably, the drugs have a Tg greater than or equal to about 60 Deg. C., more preferably the drugs have a Tg greater than or equal to about 70 Deg. C., still more preferably the drugs have a Tg greater than or equal to about 80 Deg. C., and yet more preferably the drugs have a Tg greater than or equal to about 100 Deg. C.
“Melting temperature” or “Tm” means the temperature at which the solid drug becomes a liquid at 1 atmosphere pressure.
“Stabilizer” means one or more substance(s) that are effectively adsorbed to a surface of an amorphous drug core but do not chemically bond to the amorphous drug core. In an embodiment, the adsorption of stabilizer on the amorphous drug core is in an amount sufficient to maintain an effective diameter of an amorphous drug core less than or equal to about 2.0 microns, preferably less than or equal to about 1.5 micron, more preferably less than or equal to about 1.0 micron, and still preferably less than or equal to about 0.75 micron. Preferably, the stabilizer may be an amorphous material (either in solid or in solution) by itself, and may in certain embodiments have some hydrophobic group(s) in the chemical structure. Suitable surface stabilizers are preferably selected from known organic and inorganic pharmaceutical excipients (GRAS). Such excipients include various polymers, low molecular weight oligomers, natural products, and surfactants. Preferred surface stabilizers are hydrophilic nonionic polymer or copolymers with one or more weak polar group(s). Combinations of different stabilizers and or co-stabilizers may be useful in the practice of this invention.
In a preferable embodiment, stabilizers may comprise co-stabilizers. Co-stabilizers comprise nonionic or ionic surfactants or polymers, which cannot effectively stabilize the particles in the absence of stabilizers. However, in presence of a stabilizer, a co-stabilizer can significantly improve stabilization of stabilizers by enhancing static repulsion and/or playing a role of Ostwald ripening inhibitor and/or recrystallization inhibitor. Preferred co-stabilizers are those that are not prone to solubilize the drug, such as double chain ionic surfactants.
The surface stabilizers and co-stabilizers employed in the present invention can be polymers or copolymers; surfactants, peptides and/or proteins and combinations thereof. Representative examples of surface stabilizers and co-stabilizers include polymer or copolymers, surfactants, proteins and other pharmaceutical excipients listed in Handbook of Pharmaceutical Excipients, published jointly by the American Pharmaceutical Association and The Pharmaceutical Society of Great Britain (The Pharmaceutical Press, 1986), such as:
Polyvinylpyrrolidone (e.g. PVP K12, PVP K17, and PVP K30 etc.)
Cellulosic polymers, such as HPC-SL, HPC-L, HPMC
Copolymer of Vinyl Pyrrolidone and Vinyl acetate (e.g. Plasdone® S630, VA64)
Poloxamers, such as, Pluronics® F68, F 108 which are block copolymers of ethylene oxide and propylene oxide);
Polyethylene Glycol (e.g. PEG 400, PEG 2000, PEG 4000, etc)
Polyvinyl alcohol (PVA),
Tyloxapol
Polyoxyethylene Castor oil Derivatives
Colloidal silicon Dioxide
Carbomers (e.g. Carbopol 934 (Union Carbide); CMC Na
Polysobate 80, 20 etc.
Benzalkonium chloride
Charged Phospholipids
Sodium Docusate, Aerosol OT (Cytec)
Others examples include gelatin, casein, lysozyme, albumin, cholesterol, stearic acid, calcium stearate, glycerol monostearate, sodium dodecylsulfate, methylcellulose, noncrystalline cellulose, magnesium aluminium silicate, Triton® X-200 (an alkyl aryl polyether sulfonate available from Rohm and Haas). Mixtures of any of the above are also within the scope of the invention.
“Nanoparticle” means a particle having an effective diameter less than or equal to about 2.0 microns, preferably less than or equal to about 1.5 micron, more preferably less than or equal to about 1.0 micron, and still preferably less than or equal to about 0.75 micron.
“Nanosizing the amorphous bulk material” means forming amorphous drug cores that, in an embodiment, possess effective diameters less than or equal to about 2.0 microns, preferably less than or equal to about 1.5 micron, more preferably less than or equal to about 1.0 micron, and still preferably less than or equal to about 0.75 micron. Methods of nanosizing the amorphous bulk material are found elsewhere herein.
“Water solubility” means a measure of the maximum possible concentration of a drug dissolved in water. The water temperature may be specified; in an embodiment water solubility is determined at 25 Deg. C. Units of measurement of water solubility are typically mass/volume, such as mg/ml. The water solubility of drug useful in the practice of the present invention is less than or equal to about 1 mg/ml at 25 Deg. C.; preferably less than or equal to about 0.1 mg/ml at 25 Deg. C.; more preferably less than or equal to about 0.01 mg/ml at 25 Deg. C., still more preferably less than or equal to about 1 microgram/ml at 25 Deg. C.
3. Materials and Methods for Making the Inventive Nanoparticles
The inventive nanoparticles may be made by a variety of methods, as generally set forth herein.
Amorphous bulk materials according to the invention may be formed in a variety of ways including but not limited to directly obtaining through chemical synthesizing, melting/quenching the drug, solvent casting the drug, super critical fluid extraction, rapid precipitation by antisolvent addition, grinding/milling, freeze drying, spray freezing (e.g. Enhanced aqueous dissolution of a poorly water soluble drug by novel particle engineering technology: spray-freezing into liquid with atmospheric freeze-drying. Pharm Res. 2003 March; 20(3):485-93), solvent extraction, or dehydration of hydrated compounds (e.g. Advanced Drug Delivery Reviews 48 (2001) 27-42), freeze-drying, spray-drying (e.g. J. Broadhead, S. K. Rouan Edmond, C. T. Rhodes, The spray drying of pharmaceuticals, Drug Dev. Ind. Pharm. 18 (1992) 1169-1206.), or combinations of the above. Additional methods may be found in Yu L., Amorphous pharmaceutical solids: preparation characterization and stabilization. Adv. Drug. Delivery Rev., 2001, 48, p. 27-42.
Typically, the method or methods of forming amorphous bulk materials according to the invention will result in amorphous bulk materials that are substantially amorphous, preferably at least about 80% w/w amorphous, more preferably at least about 85% w/w amorphous, still more preferably at least about 90% w/w amorphous, even more preferably at least about 95% w/w amorphous, yet more preferably at least about 99% w/w amorphous, and most preferably at least about 99.5% w/w amorphous. The weight fraction of amorphous material in the amorphous bulk material may be determined according to the DSC methods disclosed herein as being useful for determining weight fraction of amorphous material in the inventive amorphous drug cores. When preparing bulk amorphous drug, it is preferred that there is no excipient and/or dopant added.
Amorphous bulk materials according to the invention may be nanosized in a variety of ways, including but not limited to milling (as described, for example, in U.S. Pat. No. 5,145,684), high speed homogenization, hydrodynamic cavitation (as described, for example, in U.S. Pat. No. 5,858,410), ultrasonication (as described, for example, in U.S. Pat. No. 5,091,188), or combinations of any of the above methods. Operation at relatively low temperatures and pressures is preferred. For example, the size reduction operation temperature is preferred to be done at temperatures at least 10 Degree C. lower than the drug's Tg. Atmospheric pressure is preferred during nanosizing operations.
A typical effective diameter target for a nanosizing operation according to the invention is to get the effective diameter of particles to be equal to or less than about 0.8 micron. The particle size can be checked during or after the nanosizing operation. If particle size doesn't decrease even if the nanosizing time is extended, the operation is essentially complete, or must be continued using a different unit operation.
Preferably, stabilizers, and optional co-stabilizers, may be combined with the amorphous bulk materials prior to nanosizing the amorphous bulk materials. In certain embodiments, stabilizers and optional co-stabilizers may be added during or shortly after the nanosizing. The timing of adding the stabilizers may be dependent on interactions between the amorphous bulk material and the particular stabilizer and optional co-stabilizer. In embodiments, the weight ratio of amorphous bulk material to stabilizer (including optional co-stabilizer) ranges from about 1/2 to about 20/1, preferably from about 1/1 to about 10/1. Preferably, the weight ratios are measured based on the amorphous bulk material to stabilizer (including optional co-stabilizer) added to the nanosizing operation (as opposed to direct measurement of the inventive nanoparticles themselves.
While there has been described and pointed out features and advantages of the invention, as applied to present embodiments, those skilled in the medical art will appreciate that various modifications, changes, additions, and omissions in the method described in the specification can be made without departing from the spirit of the invention. In particular, the following Examples are intended to be illustrative, and not limiting in any way, of the present invention.
The following drug (COMPOUND 1), with a water solubility less than or equal to about 0.2 ng/ml, was selected for forming nanoparticles according to the invention.
After the crystalline form of this drug was melted at 200° C. in an aluminum container, it was quickly transferred into an ice bath and converted into bulk amorphous drug, i.e. amorphous bulk material in this embodiment. The bulk amorphous drug was then mixed with water, stabilizers and other milling media. The mixture was loaded into a mechanical mill (Elan, Nanomill). Shear force was applied by milling to nanosize the bulk amorphous drug into nanosized amorphous drug particles with adsorbed stabilizer, i.e. the inventive population of nanoparticles. The same particle size reduction method was applied for crystalline COMPOUND 1 to get nanosized crystalline nanoparticles. The nanosized formulations were collected, and dried through lyophilization if necessary.
Composition for wet milling (same for both crystalline and amorphous samples), expressed as weight percent based on total weight of material charged to the mill.
Compound 1:15%
Hydroxypropylmethyl cellulose (HPMC): 3.5%
Deionized water: 81.25%
Conditions for Milling:
Milling media: 5.43 g Polymill 500 (Elan)
From the DSC study, it can be seen that crystalline Compound 1 has a melting point at 171.34 Deg C. and no glass transition is detected, while the amorphous COMPOUND 1 doesn't have melting point but has a glass transition at 87.07° C. (Tg) (see Table 1). The glass forming ability (GFA), Tg/Tm=0.81. The X-ray diffraction spectra (XRD) (
The preparation of Example 1 was substantially duplicated, except for the following changes:
Composition for wet milling (same for both crystalline and amorphous samples), expressed as weight percent based on total weight of material charged to the mill.
Compound 1:7.5%
Hydroxypropylmethyl cellulose (HPMC): 3.8%
Deionized water: 88.43%
Condition of Milling:
Milling media: 5.43 g Polymill 500 (Elan)
After size reduction by milling, both crystalline drug nanoparticles and inventive amorphous drug nanoparticles were obtained. Table 3 shows particles size of the nanosized crystalline and amorphous COMPOUND 1 after milling. In this example, the particle size of inventive nanoparticles comprising amorphous drug cores that comprise COMPOUND 1 is about 200 nm. Again,
Terfenadine is an antihistamine drug. After the crystalline form of this drug was melted at 170° C. and quickly transferred into dry ice (solid CO2) bath and converted into amorphous form, bulk amorphous drug, i.e. amorphous bulk material in this embodiment, was mixed with water, stabilizers and other milling media. The mixture was loaded into a mechanical mill. Shear force was applied to nanosize the bulk amorphous drugs into nanosized amorphous drug with adsorbed stabilizer, i.e. the inventive population of nanoparticles. The same particle size reduction method was applied to crystalline terfenadine to get nanosized crystalline particles. The formulations were collected, and dried through lyophilization if necessary.
Composition for wet milling (same for both crystalline and amorphous samples), expressed as weight percent based on total weight of material charged to the mill.
Terfenadine: 5%
Hydroxypropylmethyl cellulose (HPMC): 2.85%
DI water: 92.01%
Condition of Milling:
Milling media: 5.44 g Polymill 500 (Elan)
From the DSC study, it can be seen that crystalline terfenadine has a melting peak at 151.06° C. and no glass transition is detected. After melting and quenching, the amorphous terfenadine has glass transition at 53.77° C. (Tg) but also has a small melting peak at 148.89° C. (Table 4). The crystalline portion of the amorphous terfenadine is less than 20 percent of original crystallinity. In XRD (
This application claims the benefit of U.S. Provisional Application Ser. No. 60/716,459, filed Sep. 12, 2005.
| Number | Date | Country | |
|---|---|---|---|
| 60792053 | Apr 2006 | US |
