The Specification
320 The claimed priority date of the 807 Patent is 24 May 2002. The respondent did not contend for any different priority.
321 The 807 Patent is directed to a hypothetical skilled team ("the notional team") which would include a pharmaceutical scientist with expertise in particle engineering and a research pharmacist with expertise in pharmacology equipped with the common general knowledge in those fields as at 24 May 2002.
322 The 807 Patent describes the field of the invention at page 1 lines 5-7:
The present invention relates to a nanoparticulate composition comprising a fibrate, preferably fenofibrate or a salt thereof. The nanoparticulate fibrate, preferably fenofibrate, particles have an effective average particle size of less than about 2000 nm.
323 Nanoparticulate compositions and prior art methods of making them are discussed in a section of the specification headed "Background Regarding Nanoparticulate Compositions". The specification states at page 1 lines 10-19:
Nanoparticulate compositions, first described in U.S. Patent No. 5,145,684 ("the '684 patent"), are particles consisting of a poorly soluble therapeutic or diagnostic agent having adsorbed onto the surface thereof a non-crosslinked surface stabilizer. The '684 patent does not describe nanoparticulate compositions of a fibrate.
Methods of making nanoparticulate compositions are described in, for example, U.S. Patent Nos. 5,518,187 and 5,862,999, both for "Method of Grinding Pharmaceutical Substances;" U.S. Patent No. 5, 718,388, for "Continuous Method of Grinding Pharmaceutical Substances" and U.S. Patent No. 5,510,118 for "Process of Preparing Therapeutic Compositions Containing Nanoparticles."
This is followed by a lengthy discussion of other US patents in which nanoparticulate compositions are described.
324 Fenofibrate is described in the section of the specification headed "Background Regarding Fenofibrate". The compound is described at page 4 lines 16-20 as follows:
The compositions of the invention comprise a fibrate, preferably fenofibrate. Fenofibrate, also known as 2-[4-(4-chlorobenzoyl) phenoxy]-2-methyl-propanoic acid, 1-methylethyl ester, is a lipid regulating agent. The compound is insoluble in water …
325 This is also followed by a discussion of other US patents in which fenofibrate is described. The patents referred to include US Patents 6,074,670 and 6,277,405 both for "Fenofibrate Pharmaceutical Compositions Having High Bioavailability and Method for Preparing It", US Patent 6,074,670 which refers to "immediate-release fenofibrate composition comprising micronized fenofibrate and at least one inert hydrosoluble carrier", US Patent 4,739,101 describing a process for making fenofibrate, and US Patent 6,277,405 directed to micronized fenofibrate compositions having a specified dissolution profile.
326 The specification also refers to two International Applications, WO 01/80828 for "Improved Water-Insoluble Drug Particle Process" ("the 828 Patent") and WO 02/24193 for "Stabilised Fibrate Microparticles" ("the 193 Patent"). Both of these publications are said to describe a process for making small particle compositions of poorly water soluble drugs. Both documents, which it may be inferred were publicly available before the priority date of the 807 Patent, are specifically incorporated by reference (see page 42B lines 28-30).
327 After referring to the process described in the 828 Patent and the 193 Patent, the specification next states at page 5 lines 12-21:
The process requires preparing an admixture of a drug and one or more surface active agents, followed by heating the drug admixture to at or above the melting point of the poorly water soluble drug. The heated suspension is then homogenized. The use of such a heating process is undesirable, as heating a drug to its melting point destroys the crystalline structure of the drug. Upon cooling, a drug may be amorphous or recrystallize in a different isoform, thereby producing a composition which is physically and structurally different from that desired. Such a "different" composition may have different pharmacological properties. This is significant as U.S. Food and Drug Administration (USFDA) approval of a drug substance requires that the drug substance be stable and produced in a repeatable process.
328 This is followed by a further reference to another prior art publication describing compositions of fibrate and vitamin E TGPS (a water soluble derivative of vitamin E) comprising particles the diameters of which are within defined ranges in which the mean diameter of about 100 nm to about 900 nm, with 50% of the particles of the composition below the range 350 nm to 750 nm ("D50") and 99% below the range 500 nm to 900 nm ("D99"). The specification then states at page 6 lines 1-2 that this publication "… does not teach that the described compositions show minimal or no variability when administered in fed as compared to fasted conditions."
329 The specification includes a description of a number of advantages that are said to arise using formulations of the fibrate composition to the invention. Compositions of the invention are said to significantly increase the bioavailability of fenofibrate which can enable use of a smaller solid dosage size. Compositions of the invention are also said to have an improved pharmacokinetic profile that is not substantially affected by the fed or fasted state of a human to whom such a composition is administered. This is a reference to what is referred to as the "food effect" whereby the taking of a poorly soluble drug with food (ie. in a fed state) may enhance it bioavailability compared to taking the drug without food (ie. in a fasted state).
330 The specification asserts that the invention encompasses a fibrate, preferably fenofibrate, composition in which administration of the composition to a subject in a fasted state is bioequivalent to the administration of the composition to a subject in a fed state. The specification adopts the following measure of bioequivalence at page 16 lines 26-30:
"Bioequivalency" is established by a 90% Confidence Interval (CI) of between 0.80 and 1.25 for both Cmax and AUC under USFDA regulatory guidelines, or a 90% CI for AUC of between 0.80 to 1.25 and a 90% CI for Cmax of between 0.70 to 1.43 under the European EMEA regulatory guidelines.
331 The specification also refers to the redispersibility of the fibrate compositions. This feature is explained at page 18 lines 13-26:
An additional feature of the fibrate, preferably fenofibrate, compositions of the invention is that the compositions redisperse such that the effective average particle size of the redispersed fibrate particles is less than about 2 microns. This is significant, as if upon administration the nanoparticulate fibrate compositions of the invention did not redisperse to a substantially nanoparticulate particle size, then the dosage form may lose the benefits afforded by formulating the fibrate into a nanoparticulate particle size.
This is because nanoparticulate active agent compositions benefit from the small particle size of the active agent; if the active agent does not redisperse into the small particle sizes upon administration, then "clumps" or agglomerated active agent particles are formed, owing to the extremely high surface free energy of the nanoparticulate system and the thermodynamic driving force to achieve an overall reduction in free energy. With the formation of such agglomerated particles, the bioavailability of the dosage form may fall well below that observed with the liquid dispersion form of the nanoparticulate active agent.
332 The specification refers at page 6 lines 3-10 to clinical studies demonstrating the association between cholesterol and the development of atherosclerosis. The specification then states at page 6 lines 11-24:
Fenofibric acid, the active metabolite of fenofibrate, produces reductions in total cholesterol, LDL cholesterol, apo-lipoprotein B, total triglycerides, and triglyceride rich lipoprotein … in treated patients. …
Because fibrates, including fenofibrate, are so insoluble in water, significant bioavailability can be problematic. In addition, conventional fibrate, including fenofibrate, formulations exhibit dramatically different effects depending upon the fed or fasted state of the patient. Finally, conventional fibrate, including fenofibrate, formulations require relatively large doses to achieve the desired therapeutic effects. There is a need in the art for nanoparticulate fibrate formulations which overcome these and other problems associated with prior conventional microcrystalline fibrate formulations. The present invention satisfies these needs.
333 The specification includes a number of definitions. According to the specification at page 6A lines 10-12, the word "comprise" (and its variants) "is not intended to exclude other additives, components, integers or steps." At page 12 lines 3-11 there is a rather curious definition of stable, which states:
As used herein with reference to stable fibrate, preferably fenofibrate, particles, "stable" includes, but is not limited to, one or more of the following parameters: (1) that the fibrate particles do not appreciably flocculate or agglomerate due to interparticle attractive forces, or otherwise significantly increase in particle size over time; (2) that the physical structure of the fibrate, preferably fenofibrate, particles is not altered over time, such as by conversion from an amorphous phase to crystalline phase; (3) that the fibrate, preferably fenofibrate, particles are chemically stable; and/or (4) where the fibrate has not been subject to a heating step at or above the melting point of the fibrate in the preparation of the nanopartic1es of the invention.
334 The specification includes under the heading "Summary of the Invention" a number of consistory statements. The first consistory statement at page 8a lines 1-16 mirrors the language of claim 1. This is then followed by five more consistory statements that mirror the language of claims 2, 3, 40, 41 and 42. The first three consistory statements (mirroring claims 1, 2 and 3) refer to compositions (ie. products) and the other three (mirroring claims 40, 41 and 42) refer to methods of treatment.
335 The consistory statements are followed by a detailed description of the invention including by reference to two graphs (Fig 1 and Fig 2).
336 The specification states at page 10 line 16 to page 11 line 24:
The present invention is directed to nanoparticulate compositions comprising a fibrate, preferably fenofibrate. The compositions comprise a fibrate, preferably fenofibrate, and preferably at least one surface stabilizer adsorbed on the surface of the drug. The nanoparticulate fibrate, preferably fenofibrate, particles have an effective average particle size of less than about 2000 run.
As taught in the '684 patent, and as exemplified in the examples below, not every combination of surface stabilizer and active agent will result in a stable nanoparticulate composition. It was surprisingly discovered that stable, nanoparticulate fibrate, preferably fenofibrate, formulations can be made.
Advantages of the nanoparticulate fibrate, preferably fenofibrate, formulations of the invention as compared to conventional non-nanoparticulate formulations of a fibrate, particularly a fenofibrate such as TRICOR® (tablet or capsule microcrystalline fenofibrate formulations), include, but are not limited to: (1) smaller tablet or other solid dosage form size; (2) smaller doses of drug required to obtain the same pharmacological effect; (3) increased bioavailability; (4) substantially similar pharmacokinetic profiles of the nanoparticulate fibrate, preferably fenofibrate, compositions when administered in the fed versus the fasted state; (5) improved pharmacokinetic profiles; (6) bioequivalency of the nanoparticulate fibrate, preferably fenofibrate, compositions when administered in the fed versus the fasted state; (7) an increased rate of dissolution for the nanoparticulate fibrate, preferably fenofibrate, compositions; (8) bioadhesive fibrate, preferably fenofibrate, compositions; and (9) the nanoparticulate fibrate, preferably fenofibrate, compositions can be used in conjunction with other active agents useful in treating dyslipidemia, hyperlipidemia, hypercholesterolemia, cardiovascular disorders, or related conditions.
The present invention also includes nanoparticulate fibrate, preferably fenofibrate, compositions together with one or more non-toxic physiologically acceptable carriers, adjuvants, or vehicles, collectively referred to as carriers. The compositions can be formulated for parenteral injection (e.g., intravenous, intramuscular, or subcutaneous), oral administration in solid, liquid, or aerosol form, vaginal, nasal, rectal, ocular, local (powders, ointments or drops), buccal, intracisternal, intraperitoneal, or topical administration, and the like.
A preferred dosage form of the invention is a solid dosage form, although any pharmaceutically acceptable dosage form can be utilized. Exemplary solid dosage forms include, but are not limited to, tablets, capsules, sachets, lozenges, powders, pills, or granules, and the solid dosage form can be, for example, a fast melt dosage form, controlled release dosage form, lyophilized dosage form, delayed release dosage form, extended release dosage form, pulsatile release dosage form, mixed immediate release and controlled release dosage form, or a combination thereof. A solid dose tablet formulation is preferred.
337 The specification also states at page 24 lines 2-15:
The invention provides compositions comprising fibrate, preferably fenofibrate, particles and at least one surface stabilizer. The surface stabilizers preferably are adsorbed on, or associated with, the surface of the fibrate, preferably fenofibrate, particles. Surface stabilizers especially useful herein preferably physically adhere on, or associate with, the surface of the nanoparticulate fibrate particles but do not chemically react with the fibrate particles or itself. Individually adsorbed molecules of the surface stabilizer are essentially free of intermolecular cross-linkages.
338 At page 26 lines 1-10 the specification states:
The choice of a surface stabilizer for a fibrate is non-trivial and required extensive experimentation to realize a desirable formulation. Accordingly, the present invention is directed to the surprising discovery that nanoparticulate fibrate, preferably fenofibrate, compositions can be made.
Combinations of more than one surface stabilizer can be used in the invention. Useful surface stabilizers which can be employed in the invention include, but are not limited to, known organic and inorganic pharmaceutical excipients. Such excipients include various polymers, low molecular weight oligomers, natural products, and surfactants. Surface stabilizers include nonionic, anionic, cationic, ionic, and zwitterionic surfactants.
339 This passage is followed by a lengthy list of surface stablizers that can be used to perform the invention. The surface stablizers referred to include hydroxypropyl methylcellulose (also known as hypromellose or HPMC), sodium lauryl sulfate, gelatin, commercially available Tweens (eg Tween 20 and Tween 80) and many more. At page 27 lines 15-16 the specification also states that "[i]f desirable, the nanoparticulate fibrate, preferable fenofibrate, compositions of the invention can be formulated to be phospholipid-free."
340 The specification later states at page 30 line 22 to page 31 line 13:
In one embodiment of the invention, the preferred one or more surface stabilizers of the invention is any suitable surface stabilizer as described below, with the exclusion of PEG-derivatized vitamin E, which is a non-ionic compound. In another embodiment of the invention, the preferred one or more surface stabilizers of the invention is any suitable surface stabilizer as described below, with the exclusion of phospholipids. Finally, in another embodiment of the invention, the preferred one or more surface stabilizers of the invention is any substance which is categorized by the USFDA as GRAS ("Generally Recognized As Safe").
Preferred surface stabilizers of the invention include, but are not limited to, hypromellose, docusate sodium (DOSS), Plasdone® S630 (random copolymer of vinyl pyrrolidone and vinyl acetate in a 60:40 ratio), hydroxypropyl cellulose SL (HPC-SL), sodium lauryl sulfate (SLS), and combinations thereof. Particularly preferred combinations of surface stabilizers include, but are not limited to, hypromellose and DOSS; Plasdone® S630 and DOSS; HPC-SL and DOSS; and hypromellose, DOSS, and SLS.
The surface stabilizers are commercially available and/or can be prepared by techniques known in the art. Most of these surface stabilizers are known phannaceutical LO excipients and are described in detail in the Handbook of Pharmaceutical Excipients, published jointly by the American Pharmaceutical Association and The Pharmaceutical Society of Great Britain (The Pharmaceutical Press, 2000), specifically incorporated by reference.
341 The specification also includes a description of other pharmaceutical excipients that may be used as binders, fillers, lubricants, sweeteners and flavourings. It is said that such excipients are known in the art.
342 The description of excipients is followed by a description of the "nanoparticulate particle size". At page 32 line 24 to page 33 line 24 the specification states:
The compositions of the invention contain nanoparticulate fibrate particles, preferably nanoparticulate fenofibrate particles, which have an effective average particle size of less than about 2000 nm (i.e., 2 microns), less than about 1900 nm, less than about 1800 nm, less than about 1700 nm, less than about 1600 nm, less than about 1500 nm, less than about 1400 nm, less than about 1300 nm, less than about 1200 nm, less than about 1100 nm, less than about 1000 nm, less than about 900 nm, less than about 800 nm, less than about 700 nm, less than about 600 nm, less than about 500 nm, less than about 400 run, less than about 300 nm, less than about 250 nm, less than about 200 nm, less than about 150 nm, less than about 100 nm, less than about 75 nm, or less than about 50 nm, as measured by light-scattering methods, microscopy, or other appropriate methods.
By "an effective average particle size of less than about 2000 nm" it is meant that at least 50% of the fibrate, preferably fenofibrate, particles have a particle size of less than the effective average, by weight, i.e., less than about 2000 nm, 1900 nm, 1800 nm, etc., when measured by the above-noted techniques. Preferably, at least about 70%, about 90%, or about 95% of the fibrate, preferably fenofibrate, particles have a particle size of less than the effective average, i.e., less than about 2000 nm, 1900 nm, 1800 nm, 1700 nm, etc.
In one embodiment of the invention, at least 99% of the fibrate particles ("D99") have a particle size less than about 500 nm, less than about 450 nm, less than about 400 nm, less than about 350 nm, less than about 300 nm, less than about 250 nm, less than 15 about 200 run, less than about 150 nm, or less than about 100 nm. In another embodiment of the invention, at least 50% of the fibrate particles ("D50") have a particle size less than about 350 nm, less than about 300 nm, less than about 250 nm, less than about 200 nm, less than about 150 nm, less than about 100 nm, or less than about 75 nm. In yet another embodiment of the invention, the mean particle size of the fibrate composition is less than 20 about 100 nm, less than about 75 nm, or less than about 50 nm.
In the present invention, the value for D50 of a nanoparticulate fibrate, preferably fenofibrate, composition is the particle size below which 50% of the fibrate particles fall, by weight. Similarly, D90 is the particle size below which 90% of the fibrate particles fall, by weight.
343 This is followed by a description of what are said to be several "exemplary nanoparticulate fenofibrate tablet formulations" and "exemplary embodiments of the invention". I do not propose to set these out but it is worth nothing that the exemplary embodiments include descriptions of the invention in which it is said that the fenofibrate particles have an effective average particle size of less than about 2000 nm associated with a surface stabilizer that is not a phospholipid.
344 The description of the exemplary embodiments is followed by a section of the specification that describes methods for making the nanofibrate compositions. The specification states at page 36D lines 2-4 that "[t]he nanoparticulate fibrate, preferably fenofibrate, compositions can be made using, for example, milling, homogenization, or precipitation techniques. Exemplary methods of making nanoparticulate compositions are described in the '684 patent." This statement is followed by numerous references to prior art describing methods of making nanoparticulate compositions.
345 The specification also includes a description of milling, microprecipitation and homogenization methods used to prepare the nanoparticulate fibrate compositions. These three methods are described at page 37 line 20 to page 39 line 5 as follows:
1. Milling to Obtain Nanoparticulate Fibrate Dispersions
Milling a fibrate, preferably fenofibrate, to obtain a nanoparticulate dispersion comprises dispersing the fibrate particles in a liquid dispersion medium in which the fibrate is poorly soluble, followed by applying mechanical means in the presence of grinding media to reduce the particle size of the fibrate to the desired effective average particle size. The dispersion medimn can be, for example, water, safflower oil, ethanol, t-butanol, glycerin, polyethylene glycol (PEG), hexane, or glycol. A preferred dispersion medium is water.
The fibrate, preferably fenofibrate, particles can be reduced in size in the presence of at least one surface stabilizer. Alternatively, the fibrate particles can be contacted with one or more surface stabilizers after attrition. Other compounds, such as a diluent, can be added to the fibrate/surface stabilizer composition during the size reduction process. Dispersions can be manufactured continuously or in a batch mode.
In one embodiment of the invention, a mixture of a fibrate and one or more surface stabilizers is heated during the milling process. If a polymeric surface stabilizer is utilized, the temperature is raised to above the cloud point of the polymeric surface stabilizer but below the actual or depressed melting point of the fibrate. The utilization of heat may be important for scale up of the milling process, as it can aid in the solubilization of the one or more active agents.
2. Precipitation to Obtain Nanoparticulate Fibrate Compositions
Another method of forming the desired nanoparticulate fibrate, preferably fenofibrate, composition is by microprecipitation. This is a method of preparing stable dispersions of poorly soluble active agents in the presence of one or more surface stabilizers and one or more colloid stability enhancing surface active agents free of any trace toxic solvents or solubilized heavy metal impurities. Such a method comprises, for example: (1) dissolving a fibrate in a suitable solvent; (2) adding the formulation from step (1) to a solution comprising at least one surface stabilizer; and (3) precipitating the formulation from step (2) using an appropriate non-solvent. The method can be followed by removal of any formed salt, if present, by dialysis or diafiltration and concentration of the dispersion by conventional means.
3. Homogenization to Obtain Nanoparticulate Fibrate Compositions
Exemplary homogenization methods of preparing active agent nanoparticulate compositions are described in U.S. Patent No. 5,510,118, for "Process of Preparing Therapeutic Compositions Containing Nanoparticles." Such a method comprises dispersing particles of a fibrate, preferably fenofibrate, in a liquid dispersion medium, followed by subjecting the dispersion to homogenization to reduce the particle size of the fibrate to the desired effective average particle size. The fibrate particles can be reduced in size in the presence of at least one surface stabilizer. Alternatively, the fibrate particles can be contacted with one or more surface stabilizers either before or after attrition. Other compounds, such as a diluent, can be added to the fenofibrate/surface stabilizer composition either before, during, or after the size reduction process. Dispersions can be manufactured continuously or in a batch mode.
346 The specification refers at page 42B page 57 to eight examples given to illustrate the invention. The information presented includes a description of various formulations including details of particle sizes, redispersibility and a study of the food effect. The results presented are said at page 52 lines 11-14 to show that in one of the examples tested (Example 5) the pharmacokinetic profile of the fibrate was not affected by the fed or fasted state of a subject ingesting the composition (ie. no food effect). At page 58 lines 8-18 it is also asserted that, when compared to the conventional microcrystalline form of fenofibrate 160 mg dosage form "the nanoparticulate fenofibrate dosage form of the invention exhibit dramatically improved rates of dissolution."