Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D403/00—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00
  • C07D403/02—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00 containing two hetero rings
  • C07D403/10—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00 containing two hetero rings linked by a carbon chain containing aromatic rings
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/41—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having five-membered rings with two or more ring hetero atoms, at least one of which being nitrogen, e.g. tetrazole
  • A61K31/4164—1,3-Diazoles
  • A61K31/4184—1,3-Diazoles condensed with carbocyclic rings, e.g. benzimidazoles
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/14—Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles
  • A61K9/141—Intimate drug-carrier mixtures characterised by the carrier, e.g. ordered mixtures, adsorbates, solid solutions, eutectica, co-dried, co-solubilised, co-kneaded, co-milled, co-ground products, co-precipitates, co-evaporates, co-extrudates, co-melts; Drug nanoparticles with adsorbed surface modifiers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P13/00—Drugs for disorders of the urinary system
  • A61P13/12—Drugs for disorders of the urinary system of the kidneys
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/04—Inotropic agents, i.e. stimulants of cardiac contraction; Drugs for heart failure
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/10—Drugs for disorders of the cardiovascular system for treating ischaemic or atherosclerotic diseases, e.g. antianginal drugs, coronary vasodilators, drugs for myocardial infarction, retinopathy, cerebrovascula insufficiency, renal arteriosclerosis
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/12—Antihypertensives

Definitions

• the present invention encompasses stable candesartan cilexetil of fine particle size, processes for its preparation and pharmaceutical compositions thereof.
• Candesartan is a potent, long-acting, selective AT 1 subtype angiotensin II receptor antagonist.
• Candesartan is a useful therapeutic agent for treating circulatory system diseases such as hypertensive diseases, heart diseases (e.g. hypercardia, heart failure, cardiac infarction, etc.), strokes, cerebral apoplexy, and nephritis, among others.
• Candesartan meets the requirement of high potency but it is poorly absorbed when administered orally. Therefore, the prodrug candesartan cilexetil was developed. During absorption from the gastrointestinal tract candesartan cilexetil is rapidly and completely hydrolyzed to candesartan.
• candesartan 2-ethoxy-l-[[2'-(lH- tetrazol-5-yl)bi ⁇ henyl-4-yl]methylJ-lH-benzimidazole-7-carboxylic acid.
• the chemical name for candesartan cilexetil is ( ⁇ )-l-[[(cyclohexyloxy)carbonyl]oxy]ethyl-2-ethoxy-l- [[2'-(lH-tetrazol-5-yl)[l,l'biphenyl]-4-yl]methyl]-lH-benzimidazole-7-carboxylate.
• Candesartan cilexetil is a white to off-white powder and is sparingly soluble in water and in methanol. Although candesartan cilexetil contains an asymmetric center in the ester portion of the molecule, it is sold as the racemic mixture.
• Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin-co ⁇ verting enzyme (ACE, kininase II).
• Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation, and renal reabsorption of sodium.
• Angiotensin II help maintain constant blood pressure despite fluctuations in a person's state of hydration, sodium intake and other physiological variables.
• Angiotensin II also performs the regulatory tasks of inhibiting excretion of sodium by the kidneys, inhibiting norephedrine reuptake and stimulating aldosterone biosynthesis.
• Candesartan blocks the vasoconstrictor and aldosterone secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT 1 receptor in many tissues, such as vascular smooth muscle and the adrenal gland. By inhibiting angiotensin II binding to AT 1 receptors, candesartan disrupts the vasoconstriction mediated by AT 1 receptors. Blocking vasoconstriction by angiotensin II has been found to be beneficial to patients with hypertension. The United States Food and Drug Administration has approved candesartan for the treatment of hypertension alone or in combination with other antihypertensive agents.
• U.S. Patent No. 5,196,444 (the '444 patent) relates to one. crystalline form of candesartan cilexetil, the C-type crystal, which has the following lattice spacings: 3.5, 3.7, 3.8, 4.0, 4.1, 4.3, 4.4, 4.6, 4.8, 5.1, 5.2, 6.9, 7.6, 8.8, 9.0 and 15.9 A, with varying peak intensities.
• the C-type crystals claimed by US'444 are said to be stable by heating, but no data is provided in support.
• Atacand® appears to contain the active ingredient in reduced particle sizes. Small particles size is usually achieved by milling or micronization. Particle size reduction of Candesartan cilexetil, however, showed to have an adverse effect on its chemical stability.
• the present invention encompasses stable candesartan cilexetil of fine particle size, wherein desethyl-candesartan (desethyl-CNS) within the stable candesartan cilexetil does not increase to more than about 0.1%w/w by HPLC relative to the initial amount of candesartan cilexetil, when the stable candesartan cilexetil is maintained at a temperature of about 55 0 C for at least 2 weeks.
• desethyl-candesartan desethyl-CNS
• the candesartan cilexetil is the crystalline Form I, characterized by x- ray diffractogram having peaks at about 5.6, 9.8, 17.0, 18.5, and 22.2 +0.2 degrees two- theta.
• This stable candesartan cilexetil of fine particle size may be further characterized by a DSC thermogram having an endotherm with a peak temperature of at least about 158.O 0 C followed by an exothermal peak caused by decomposition.
• Another embodiment of the invention encompasses a process for the preparation of stable micronized candesartan cilexetil of fine particle size, comprising slurrying a sample of candesartan cilexetil of fine particle size in a suitable solvent for a suitable amount of time, and recovering stable candesartan cilexetil of fine particle size, wherein desethyl-candesartan (desethyl-CNS) within the stable candesartan cilexetil does not increase to more than about 0.1%w/w by HPLC relative to the initial amount of candesartan cilexetil, when the stable candesartan cilexetil is maintained at a temperature of about 55 0 C for at least 2 weeks.
• desethyl-candesartan desethyl-CNS
• the solvent is a C 1 -C 4 alcohol, and more preferably methanol or ethanol.
• the slurrying is performed at a temperature of at least about 15 0 C. This process may be also used in order to further stabilize candesartan cilexetil.
• the invention also encompasses pharmaceutical compositions comprising stable candesartan cilexetil of fine particle size and a pharmaceutically acceptable excipient, and methods of treating circulatory system diseases using the same.
• the candesartan cilexetil is Form I.
• Figure 1 illustrates the powder X-ray diffraction pattern for candesartan cilexetil Form I of fine particle size.
• Figure 2 illustrates the powder X-ray diffraction pattern for candesartan cilexetil Form I of fine particle size after slurry in the suitable solvent.
• Figure 3 illustrates the DSC thermogram for candesartan cilexetil Form I of fine particle size.
• Figure 4 illustrates the DSC thermogram for candesartan cilexetil Form I of fine particle size obtained after slurry.
• Particles size can affect the solubility properties of a compound, like candesartan cilexetil.
• Particle size reduction is one method of formulating materials having low solubility, like candesartan cilexetil.
• Particle size reduction can also increase a compound's dissolution rate, and hence, its bioavailability.
• the enhanced dissolution rate is achieved with the increase in the surface area as a result of particle size reduction.
• the rate of dissolution of a poorly soluble drug is the rate limiting factor in its rate of absorption by the body.
• these drugs may be more readily bioavailable if administered in a finely divided state.
• Particle size also can affect how freely crystals or a powdered form of a drug will flow past each other which has consequences in the production process of pharmaceutical products containing the drug.
• the term "fine particle size” refers to a sample comprising particles having a maximum diameter of no more than about 20 ⁇ m.
• the term “stable” in reference to candesartan cilexetil means candesartan cilexetil wherein the level of the desethyl-candesartan (desethyl-CNS) impurity does not increase to more than about 0.1%w/w by HPLC, relative to the candesartan cilexetil, when maintained at a temperature of about 55 0 C for at least 2 weeks.
• the present invention provides stable candesartan cilexetil of fine particle size.
• the candesartan cilexetil is crystalline Form I.
• the stable candesartan cilexetil of fine particle size is maintained for at least 4 weeks.
• Candesartan cilexetil Form I may be characterized by main x-ray diffraction peaks at about 5.6, 9.8, 17.0, 18.5 and 22.2 ⁇ 0.2 degrees two-theta. Form I is substantially depicted in Figure 2. This stable candesartan cilexetil of fine particle size is further characterized by a DSC thermogram having an endotherm with a peak temperature of at least about 158.O 0 C followed by an exothermal peak caused by decomposition, substantially as depicted in Figure 4.
• the present invention also encompasses processes for the preparation of stable candesartan cilexetil of fine particle size.
• the processes comprise: a) providing a sample of candesartan cilexetil of fine particle size; b) slurrying the sample in at least one C 1 -C 4 alcohol for about 16 to about 48 hours; c) recovering stable candesartan cilexetil of fine particle size.
• the candesartan cilexetil obtained by this process is crystalline Form I.
• the C 1 -C 4 alcohol is methanol or ethanol.
• the slurrying in step b) is performed at a temperature of at least about 15 0 C, more preferably, at a temperature of between about 15 0 C to about 5O 0 C, and most preferably, at a temperature of between about 25 0 C to about 35 0 C.
• the sample is slurried for about 20 to about 30 hours.
• the stable candesartan cilexetil of fine particle size may be recovered by any method known in the art, such as cooling the sample, filtering out the solvent, washing the particles, preferably with the solvent added in step a), and drying the particles, preferably at a temperature of about 6O 0 C under reduced pressure.
• the candesartan cilexetil of fine particle size provided in step a) may be obtained directly from the synthesis of candesartan cilexetil, or by comminuting a candesartan cilexetil sample in order to decrease their size to a maximum diameter of no more than about 20 ⁇ m.
• Comminution of the candesartan cilexetil of fine particle size may be performed by any known methods of particle size reduction starting with crystals, powder aggregates and course powder of either crystalline or amorphous candesartan cilexetil.
• the principal operations of conventional size reduction are milling of a feedstock material and sorting of the milled material by size.
• a fluid energy mill, or micronizer is an especially preferred type of mill for its ability to produce particles of small size in a narrow size distribution.
• the feedstock should be provided in an average particle size range of about 12 to 20 ⁇ m which may be achieved using a conventional ball, roller or hammer mill if necessary.
• fluid energy mills use the kinetic energy of collision between particles suspended in a rapidly moving fluid (typically air) stream to cleave the particles.
• the suspended particles are injected under pressure into a recirculating gas stream. Smaller particles are carried aloft inside the mill and swept into a vent and are collected.
• the vent may be connected to a particle size classifier such as a cyclone.
• Fluid energy mills are designed so that particles are classified by mass. Only particles with a momentum in a certain range will enter the vent and be collected. Centrifugal forces serve to classify the particles in a fluid energy mill.
• a powder composition according to this invention can be produced using cyclonic or centrifugation separation techniques.
• Candesartan cilexetil samples of fine particle size were slurried as described above.
• the peak temperature and the stability of the slurried sample were studied for two weeks.
• the results are summarized in Table 1. The values are reported as weight percent (w/w%) as determined by HPLC.
• Table 2b Correlation between time of slurry and peak temperature of Candesartan cilexetil of fine particle size, measured by DSC and stability
• candesartan cilexetil particles of the present invention may be determined by any method known in the art, such as laser diffraction, sieve analysis, microscope observation, sedimentation etc.
• the present invention further provides a pharmaceutical composition comprising stable candesartan cilexetil of fine particle size and a pharmaceutically acceptable excipient. Also provided are methods of treating circulatory system diseases using the same.
• the stable fine particle size candesartan cilexetil in the pharmaceutical composition yields a stable pharmaceutical composition.
• the candesartan cilexetil is crystalline Form I.
• the pharmaceutical composition comprising the stable fine particle size candesartan cilexetil of the invention may be prepared by using a diluent or an excipient such as carriers, fillers, bulking agents, binders, wetting agents, disintegrating agents, surface active agents, lubricants, and the like.
• the pharmaceutical composition can include at least one diluent or excipient.
• compositions various types can be selected depending on the therapeutic purpose, for example tablets, pills, powders, liquids, suspensions, emulsions, granules, capsules, suppositories, injection preparations (solutions and suspensions), and the like.
• Any excipient commonly known and used widely in the art can be used in the pharmaceutical composition.
• Carriers include, but are not limited to, lactose, white sugar, sodium chloride, glucose, urea, starch, calcium carbonate, kaolin, crystalline cellulose, and silicic acid.
• Binders include, but are not limited to, water, ethanol, propanol, simple syrup, glucose solutions, starch solutions, gelatin solutions, carboxymethyl cellulose, shelac, methyl cellulose, potassium phosphate, and polyvinylpyrrolidone.
• Disintegrating agents include, but are not limited to, dried starch, sodium alginate, agar powder, laminalia powder, sodium hydrogen carbonate, calcium carbonate, fatty acid esters of polyoxyethylene sorbitan, sodium laurylsulfate, monoglyceride of stearic acid, starch, and lactose.
• Disintegration inhibitors include, but are not limited to, white sugar, stearin, coconut butter, and hydrogenated oils.
• Absorption accelerators include, but are not limited to, quaternary ammonium base, and sodium laurylsulfate.
• Wetting agents include, but are not limited to, glycerin, and starch.
• Adsorbing agents include, but are not limited to, starch, lactose, kaolin, bentonite, and colloidal silicic acid.
• Lubricants used include, but are not limited to, purified talc, stearates, boric acid powder, and polyethylene glycol. Tablets can be further coated with commonly known coating materials such as sugar coated tablets, gelatin film coated tablets, tablets coated with enteric coatings, tablets coated with films, double layered tablets, and multi-layered tablets.
• any commonly known excipient used in the art can be used.
• carriers include, but are not limited to, lactose, starch, coconut butter, hardened vegetable oils, kaolin, and talc.
• Binders include, but are not limited to, gum arabic powder, tragacanth gum powder, gelatin, and ethanol.
• Disintegrating agents include, but are not limited to, agar, and laminalia.
• excipients include, but are not limited to, polyethylene glycols, coconut butter, higher alcohols, esters of higher alcohols, gelatin, and semisynthesized glycerides.
• injectable pharmaceutical compositions When preparing injectable pharmaceutical compositions, solutions and suspensions are sterilized and are preferably made isotonic to blood.
• injection preparations may use carriers commonly known in the art.
• carriers for injectable preparations include, but are not limited to, water, ethyl alcohol, propylene glycol, ethoxylated isostearyl alcohol, polyoxylated isostearyl alcohol, and fatty acid esters of polyoxyethylene sorbitan.
• carriers for injectable preparations include, but are not limited to, water, ethyl alcohol, propylene glycol, ethoxylated isostearyl alcohol, polyoxylated isostearyl alcohol, and fatty acid esters of polyoxyethylene sorbitan.
• One of ordinary skill in the art can easily determine with little or no experimentation the amount of sodium chloride, glucose, or glycerin necessary to make the injectable preparation isotonic.
• Additional ingredients, such as dissolving agents, buffer agents, and analgesic agents
• compositions for treating circulatory system diseases of the present invention are not specifically restricted, and can be administered in various preparations depending on the age, sex, and symptoms of the patient.
• tablets, pills, solutions, suspensions, emulsions, granules and capsules may be orally administered.
• injection preparations may be administered individually or mixed with injection transfusions such as glucose solutions and amino acid solutions intravenously. If necessary, the injection preparations are administered singly intramuscularly, intracutaneously, subcutaneously or intraperitoneally. Suppositories may be administered into the rectum.
• the amount of candesartan cilexetil contained in a pharmaceutical composition for treating circulatory system diseases according to the present invention is not specifically restricted, however, the dose should be sufficient to treat, ameliorate, or reduce the symptoms associated with the circulatory system disease.
• the dosage of a pharmaceutical composition for treating circulatory system diseases according to the present invention will depend on the method of use, the age, sex, and condition of the patient. Typically, about 4 mg to 32 mg of candesartan cilexetil may be contained in an administration form unit.
• Scintag X-ray powder diffractometer model X'TRA Cu-tube solid state detector.
• the sample holder was a round standard aluminum sample holder with rough zero background quartz plate with a cavity of 25 (diameter)*C).5 mm (depth).
• the scanning parameters were range: 2-40 and in some cases 2-30 degrees two-theta; scan mode: continuous scan; step size: 0.05 deg.; and a rate of 3 deg/min.
• DSC analysis was done on a Mettler 821 Star e.
• the weight of the samples was about 5 mg; the samples were scanned at a rate of 10°C/min from 30°C to 130 0 C and at a rate of l°C/min from 130°C to 180°C.
• the oven was constantly purged with nitrogen gas at a flow rate of 40 ml/min. Standard 40 ⁇ l aluminum crucibles covered by lids with 3 holes were used.
• Particle size measurements were done on a Malvern Mastersizer S instrument.
• the solvent silicon fluid Silicaid F- 10 was used for measurements.
• the sample amount was about 0.1 g.
• the suspension was prepared by vortex for 10 seconds and by sonication for
• the detection limit was 0.02%.
• An example sample solution preparation was carried out by accurately preparing a 0.8 mg/mL solution of candesartan.
• Trityl Candesartan Cilexetil (TCS, 1000 g, 1172 mmol), Toluene (3000 mL), Methanol (6000 mL) and Water (50 mL) was refluxed for about 3-4 h (HPLC control), the solvents were evaporated at 50°C under reduce pressure to give a residue as a viscous oil.
• the residue was dissolved at 50 0 C in a mixture of Toluene/Methanol (2960 g, 95:5, w/w). The mixture was then cooled to (-5)°C to (5)°C and kept at this temperature for about 12 h.
• Desethyl-CNS 0.03% by w/w HPLC. Maintaining the micronized product for 2 weeks increased the desethyl-CNS level to 0.06% area by HPLC.
• Example 5 Micronized candesartan (70 g, Sample 1) was slurried at 50°C in absolute ethanol
• the starting micronized candesartan and the product candesartan were tested for stability in an oven at 55°C for 2 weeks.
• Table 3 summarizes the results. The values are reported as weight percent (w/w%) as determined by HPLC.
• Table 4 illustrates that the starting micronized candesartan partly decomposed to the IN-Et and 2N-Et products.

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